MET 387 Course Pack - Copy (2)

8/19/2019 MET 387 Course Pack - Copy (2)

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Old Dominion University

Mechanical Engineering Technology

MET 387 Power and Energy

Laboratory Course Pack

Contents

Axial Flow Turbofan

Conduction Heat Transfer

Four-Stroke Cycle Gasoline Engine Analysis

Heat Exchanger Performance Hilton Air Conditioning Unit

Reaction Turbine

Subsonic Ramjet Performance

Steam Power Plant


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Theory: Centrifugal machinery (pumps, fans, turbines) have several inherent

characteristics that are primarily a function of the unit’s design. Manufacturers provide

these characteristics (in the form of curves) to aid in the proper placement of these unitsin the systems for which they operate. The most widely used performance curves for

centrifugal machinery are the following three characteristics plotted versus the flow rate

through the fan:

1. Rise in pressure head across the fan

2. Horsepower required (brake horsepower — bhp)

3. Fan efficiency

Fan speed should remain constant for each curve.

The rise in pressure head across the fan is simply obtained by using the manometer that isconnected across the fan and is given by the following equation:

1m

F

air

H h

Where: F h = manometer reading across the fan

Note, the digital manometer is reading in inches of water

m = specific weight of the manometer fluid which is water

air = specific weight of flowing air

Note: P g atm

air RT g catm

where: P atm = atmospheric pressure (lbf /ft2)

T atm = atmospheric temperature (oR)

R = air gas constant, 53.3 (lbf -ft)/(lbmoR)

g = acceleration of gravity, 32,2 ft/s2

gc = gravitational constant, 32.2 lbm-ft/lbf -s2

Brake horsepower can be determined using the following equation:

2 BHP NT

Where: N = fan speed (rpm)

T = fan torque which is the slide weight times measured slide distance


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The fan efficiency is the ratio of the power delivered to the air to the power

provided to the fan unit (BHP). From Bernoulli’s equation and some assumptions, it has

been shown that the power delivered to the air can be determined from the followingequation:

Delivered air P QH

Where Q = volumetric flow rate

H = rise in pressure head across fan

The efficiency can then be determined from the following equation:

Delivered P

BHP WATCH UNITS!

The flow rate can be calculated from the venturi equation:

4

2 1

1

mV

air

V V

V

T

gh

Q C A D

D

Where: AV = area of the venturi throatDV = diameter of the venture throat

DT = diameter of the ductCV = 0.95

Procedure:

WARNINGS:

1. This lab involves the use of machinery rotating at high angular velocity; do

not wear loose clothing or jewelry that could become caught in the rotatingshaft!

2. When changing orifices, be careful to support both ends of the tube to prevent

damage to laboratory equipment.


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ACTION:

1. Record room temperature and pressure

2. Turn on and then zero the digital manometer and tachometer by pressing the

―tare‖ button and note which reading corresponds to the orifice plate andwhich corresponds to the fan.

3. Place the sliding weight at the outermost point on the scale and level the

motor using the spring adjustment.

4. With the blank orifice installed (the one without a hole), set the fan speed at

6,000 rpm using the variac to control the motor speed.

5. Slide the weight along the arm until the motor is balanced. Record the

distance the weight was moved from its initial position.

6.

Record the manometer readings for pressure head across the fan and the

venturi.

7. Install the next smallest orifice.

8. Repeat steps 3 - 5 for the remaining orifices ending with no orifice.

Report Requirements:

1.

Calculate head, BHP, volumetric flow rate (Q), and for each test condition.

2. Plot head, BHP, and (all three on the ordinate(s)) versus Q (on the abscissa)

on a single graph and discuss the resulting curves.


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Raw Data Sheet

Ambient Temperature: ___________Barometric Pressure: ___________

Speed:_______rpmMass: _______grams

Tube Diameter (DT): ___________

Venturi Diameter (DV): ___________

Orifice number

Slide Distance

d

Units = ______

Fan Manometer

hF

(inches of water)

Venturi Manometer

hV

(inches of water)

blank1

2

3

4

5

6

7

8

9

10

1112

13

14

15

none


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MET 387 Power and Energy Laboratory

Title: Conduction Heat Transfer Unit (Rev. July 2011, NJL)

Purpose: In technical calculations it is important to be able to determine the amount ofheat that is transferred between two mediums of different temperatures per unit time,

when the two mediums are separated by a wall. The transfer of energy due to a

temperature difference is called heat transfer and occurs in tree main forms:

Thermal conduction in a solid body, in a moving liquid body, or in agaseous body

Convection between a solid medium and flowing liquid of gaseous

medium

Thermal radiation which occurs between two bodies in sight of each

other and does not require a material between

Heat is mostly transferred simultaneously by conduction, convection and radiation. Sincethe individual types of heat transfer are governed by different laws, they must be

addresses separately. This experiment will determine the characteristics of thermalconduction in solid bodies experimentally.


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The setup for Linear conduction comprises three element: Fixed part with heater (1),

Location for varous inserts (2) and a movable part with the water cooler (3). By opening

the toggle fastener (4) and sliding back the cooler, the insert can be installed. By thismeans the heat is transferred linearly from the heater, through the insert and to the cooler.

The heater comprises external insulation (5), lid (6), brass rod (7) and the electrical heater

element (8). There are three temperature measuring points (9) under the insulation in the brass rod at 45˚. Together with the insert (10) there is thus a measurement section of ninemeasuring points.

Insert 1 has three temperature measuring points in a brass rod (11). This brass rod has

the same diameter as the heater and the cooler. When using the other inserts, insert 1 can be places on one side.

Insert 2 (12) also has the same diameter as the heater and cooler, but is made from

corrosion resistant steel (13) and does not have any temperature measuring points

Insert 3 (14) on the other hand is a smaller diameter and is again made from brass (15), italso has no temperature measuring points.

All the inserts are fitted with an insulating sleeve.

Figure 2 Linear conduction Figure 3 Heater

Figure 4 Cooler Figure 5 Inserts


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The measuring points for linear conduction are numbered form left to right. The

distance between adjacent measuring points is 10mm. The diameter of the heater, cooler,

inserts 1 and insert 2 is 25mm. Insert 3 has a diameter of 15mm. If insert 1 is not used inthe experiment, the temperature displayed for measuring points 4, 5, and 6 should be

ignored.

Figure 6 Measuring points for linear conduction

The radial conduction test item is a sealed unit. It comprises and insulating housing (1)with lid, and a disc (2) with heater (3) and cooler (4). The heater is fixed from below in

the center of the brass disc. There is copper pipe around the disc through which cooling

water can flow. From above, six temperature measuring points are fitted in a line thatstretched radially from the center to the outside. Using the apparatus the heat is

transferred radially from the heater to the cooler.

Figure 7 Radial Conduction


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The measuring points for radial conduction are numbered from the center outwards. The

distance between adjacent measuring points is 10mm. The diameter of the disc is110mm; it is 4mm thick. The heater is in the center of the disk on the underside and has

a diameter of 12mm. The temperatures for measuring points 7, 8 and 9 should be ignored

during the radial experiments.

Figure 8 Measuring points for radial conduciton


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The control and display unit has a temperature display and a power display (1,2). These

are both digital displays. The temperature is displayed in ˚C and the heater power is in

watts. The measuring point for the temperature display is selected via the rotary knob(3). The heater power is switched with the ON / OFF switch (4) and adjusted using the

potentiometer (5). Alternatively, the temperature can also be provided via software; in

this case the switch (6) has to be set onto operation mode “PC”

Figure 7 Control and display unit


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Theory: Thermal conductivity is analogous to electrical conductivity. The Fourier

Conduction Equation, which is analogous to Ohm’s Law, is shown in the following

equation for linear conduction:

Equation 1: dT

q kAdx

Where: q = rate of heat flow

k = coefficient of thermal conductionW

m K

A = area normal to heat flow (m2)

dT

dx= temperature gradient in direction of heat flow

K

m

The negative sign is required for the adopted sign convention that the direction of

increasing distance (x) is to be the direction of positive heat flow. Thus, since according

to the Second Law of Thermodynamics, heat will flow from higher to lowertemperatures. Heat flow will be positive when the temperature gradient is negative.

For a constant cross section area and steady flow of energy, we can integrate and re-writeequations 1 as follows:

2 1 2 1

qdx dt

kA

q x x T T

kA

We now have the following:

Equation 2:

2 1

2 1

q x xk

A T T

We can modify Equation 1 for radial conduction as follows:

2 A rl (r = radius, l = length or thickness of the cylinder)

2

dT

q k rl dr

Separation of variables yields:

2dr kl dT

r q


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We now integrate as follows:

2 2

1 1

2 2

11

2 1 2 1

2

2ln Now inserting the limts we have

2ln

r T

r T

r T

T r

dr kl dT

r q

kl r T

q

kl r r T T

q

Rearranging and solving the above equation for q gives us the following:

1 2

2

1

2

ln

T T q kl

r r

And finally we get

Equation 3:

2

1

1 2

ln

2

r q

r k

l T T

By measuring any two radii and corresponding temperatures, we can solve for thecoefficient of thermal conduction, k.


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Procedure

IMPORTANT!

Never operate without cooling water

Never connect the heater directly to the mains. The connection must always

be made via the control and display unit Never operate the unit above 120˚C

Always switch off the control and display unit prior to changing the power

and data cables.

1. Provide electrical power: On the rear of the control and display unit (2) there is a

mains connector (3) with a series fuse (4) and the main switch (5) via which the

control and display unit is supplied.2. Connect the test unit to the control and display unit with the data cable (6) and the

mains cable (7). The sockets for the heater load (8) and data acquisition (9) are

on the rear. The data cable and socket on the left of the test unit are used for

experiments on radial conduction (10), those on the right for linear conduction(11).

3. Make the connections for the cooling water feed and return and turn on thecooling water supply.

4. Verify water is draining from the return side before operation.

Figure 8 Unit Figure 9 Back of control unit


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Figure 10 Connection side of unit

Linear conduction

5.

Connect the data cable for linear conduciton6. Install insert 1 (or what eve insert you are testing) and verify cooling water is

running7. Switch on the unit and adjust the desired temperature via the power setting on the

control and display unit

8. When the thermal conduction process has reached steady state conditions, i.e. the

temperatures at the individual measuring points are stable and no longer changing,record the measurement results at the individual measuring points and the

electrical power supplied to the heater.

Radial conduction

9. Power everything down and switch the data cable for radial conduction

10. Switch on the unit and adjust the desired temperature via the power setting on thecontrol and display unit

11. When the thermal conduction process has reached steady state conditions, i.e. the

temperatures at the individual measuring points are stable and no longer changing,record the measurement results at the individual measuring points and the

electrical power supplied to the heater.

Further Experiments

It is possible to perform further experiments by clamping paper, cork or a thin metalsheet in place of the inserts. These intermediate pieces may make a poor contact, they

should not be thicker than 1mm.


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1. For each setup, radial, linear and different inserts if applicable, do thefollowing:

a. Calculate and tabulate the coefficient of thermal conductivity between

each successive location using the appropriate equations.i. For linear conduction use equation 2 1. Area for linear conduction is the cross sectional area of

the circular inserts

ii. For radial conduction use equation 3 2. Calculate the average coefficient of thermal conduction for each experiment

and compare to the expected values. Discuss any differences and reasons why

they might exist.

3. Plot on a separate graph for each experiment Temperature (ordinate) versuslocation (abscissa).

4. Discuss your graph(s) and results


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Radial conduction

Circular Disk as

Hollow Cylinder

Measurement Section: Brass

Diameter: 110 mm by 4mm thick

Coefficient of Thermal Conduction at 20˚C: 113 W m K

Power: ________ Watts

Measuring Point

Distance

r a

(mm)

Termperature(˚C)

Temperature

Difference

(Kelvin)

Coefficient ofthermal

conduction

W

m K

1 -

2 10

3 20

4 30

5 40

6 50


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Title: Four-Stroke Cycle Gasoline Engine Analysis (Rev. August 2011, NJL)

Purpose: To calculate the brake horsepower, volumetric efficiency, specific fuel

consumption, air to fuel ratio, equivalence ratio, and exhaust heat loss. In addition, the

torque, brake horsepower, air to fuel ratio, specific fuel consumption, and exhaust

temperature will be plotted versus engine speed.

Apparatus: The test rig consists of a Honda GX140 engine, hydraulic dynamometer,

and instrumentation unit. A stopwatch, thermometer, and barometer will also be used in

this lab. The engine and dynamometer are mounted to a test bed and joined by a rubbercoupling. The dynamometer is a paddle wheel type with water being used to provide

resistance to the paddle wheel rotation. The instrument unit houses all the instruments

for measuring engine performance as well as the fuel system and air bow viscous flowmeter. The airflow manometer must be calibrated to zero and the span and zero

adjustment on the torque meter must be calibrated prior to starting the engine.

Engine Specifications:

Manufacturer/Type Honda GX140

Valve Position Overhead ValveValve Clearance Inlet: 0.15- 0.20mm

Exhaust: 0.15- 0.20mm

(Measured at TDC when cold)

Swept Volume 144 cm3

Bore 64 mm

Stroke 45 mmCompression Ratio 8.7:1

Maximum Torque 9.8 N-m @ 2500 rpm

Maximum Output 3.7 kW @ 3600 rpmRecommended Maximum Speed Governed at 4500 rpm

Ignition System Transistor magneto

Ignition on/off switch On flywheel cover

Spark Plug NGK: BP6ES or BPR6ES

Spark Gap 0.7- 0.8 mmDry Mass 14 kg


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Theory:

For a four-stroke engine, the brake power is calculated as follows:

Equation 1: 2b P NT WATCH UNITS!

Where: N = speed (rpm)T = torque (N-m)

The brake thermal efficiency is defined as the actual power output divided by therate of heat input, as follows:

Equation 2: bb

f f

P

m HV

WATCH UNITS!

Where: f HV = Heating value of the fuel (46,152 kJ/kg)

f m = Mass flow rate of fuel

Volumetric Efficiency:

We assumed that during each cycle, an engine could draw in a mass of air equalto the sweep volume multiplied by the ambient air density. In practice, the mass of air is

also less than we assumed, partly because of the pressure losses in the induction systemand also because of heating effects that reduce the air density as it enters the engine

cylinder. The actual mass of air drawn in per cycle is calculated from the consumption

rate and the number of cycles completed per unit time. For practical reasons,consumption rates for engines are usually expressed in kg/hr.

Volumetric efficiency is defined as the ratio of the actual mass airflow to the ideal massairflow.

Equation 3: AV I

V

V

Where: VA = Actual Volumetric air flow

VI = Ideal Volumetric air flow

To find the actual and ideal volume of air for calculating the volumetric efficiency

(Equation 3), the following equations should be used:


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Equation 4: a Aair

mV

N

WATCH UNITS!

Where: VA units: m3/revolution

atmair

atm

P RT

measured mass flow rate of air am

measured engine speed N

Equation 5:1

2 2 I

SweptVolume Cycle SweptVolumeV

Cycle rev

Calculating the mass flow rate of the fuel (non-ideal):

Assuming a density for water of 1,000 kg/ m3, the mass flow rate of the fuel can

be determined as follows:

Equation 6: ( ) f f f f f Water m V SG V

Where:8ml

is what we measured,unit time

V

Note: 31 1000m l

f SG = specific gravity of fuel = 0.74 for gasoline

Specific fuel consumption is defined as the fuel consumption rate divided by the

brake power, as follows:

Equation 7: SFC =b

f

P

m

units: kg/ KW-hr

The air/fuel ratio is defined as the mass flow rate of the air divided by the massflow rate of the fuel. Values for stoichimetric air/fuel ratio (a/f) are obtained by using the

complete combustion for the fuel used. The equation for air/fuel ratio is:

Equation 8: / a

f

m A F

m

WATCH UNITS!


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Measuring the difference between the exhaust and the ambient temperatures can

make an estimate of the heat lost to the exhaust. The equation for percent heat loss in the

exhaust is:

Equation 9: %Heat Loss =

( )

100

f P fuel a

f f

C m m T

m HV

Where: T = the difference between Texhaust and Tambient

NOTE: Use Figure 1 to determine am

.

Figure 1 Viscous Flow Meter Calibration


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Procedure:

PRECAUTIONS1. When the engine is running, the lab is a high noise environment. Be sure to wear

hearing protection whenever the engine is running.

2.

The engine shaft rotates at a high angular velocity. Do not wear loose clothing or jewelry that could get caught in the rotating shaft. Wear eye protection.3. When using the strobotac to determine engine speed, do not look directly at the

light source.

4. Ensure that there is water supplied to the dynamometer at all times to preventequipment damage.

Pre-Engine Test

NOTE: Calibrate and zero the torque meter before use, to do this:1. Turn the exhaust fan on.

2. Turn the instrument unit on.

3.

Set the SPAN control to its maximum clockwise position.4.

Shake or rock the engine vigorously to overcome the striction of the bearing seals.

Vibration will take care of this normally while the engine is running.

5. Adjust the ZERO control until the torque meter reads zero.

6. Check that the zero is accurate by shaking the engine again.7. Hang a load of 3.5 kg on the calibration arm.

8. Shake the engine until the torque meter settles down to a constant value.

9. Adjust the SPAN control to give a torque reading of 8.6 N-m.10. Remove the calibration load and repeat steps 3 to 7 until satisfied that the zero

and span settings are correct.

11. Ensure that the exhaust and water hose is hooked up.

12. Ensure that any air is removed from the fuel line.

Pre-Start Check List

1. Check that the engine sump is filled with the correct grade of oil. DO NOT

OVERFILL.

2. Adjust the scale on the airflow manometer to read zero.

3. Turn on the water supply to the dynamometer. Adjust the needle valve so that themaximum flow is obtained. This ensures that the dynamometer seals are

lubricated.

4. Reduce the water flow to a trickle so that the load on the engine is not too great

when starting the engine.5. Remove all tools, weights, and obstructions from around the engine to enable

access to all controls.

6. Clear the area of personnel not involved in the test.

7. Start the engine.8. Record physical data (ambient temperature, barometric pressure, date, and time).


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Test Procedure

1. Advance the throttle to its maximum position.

2. Note the maximum speed of the engine. The dynamometer water flow should still be at the trickle flow used for starting the engine.

3. When the engine has settled down to a steady output, record the readings of

speed, torque, exhaust temperature, and air consumption. Close the fuel tap beneath the pipette so that the engine takes its fuel from the pipette. Time theconsumption of the 8mL of fuel. Turn the tap so that the pipette fills again. Enter

the results into the table provided.

4. Check that the temperature of the water flowing out of the dynamometer is lessthan 80°C. If the temperature is higher than this, increase water flow to cool the

dynamometer bearing seals.

5. Increase the flow of water flowing out of the dynamometer until the engine torque

is 1 N-m. Because the time response of the dynamometer is fairly slow, theneedle valve as to be operated slowly and oscillated to maintain a constant speed.

Allow time for the engine speed to stabilize before taking another set of data. If

the dynamometer is too sensitive to obtain the desired speed, it will help if thedrain tap is partially closed. Do not fully close the drain tap.

6. Repeat step 8 until in increments of 1 N-M until the engine stops.

7. Study the torque results. Engines normally produce a maximum torque at a

certain speed. If your results suggest that the maximum is at a lower speed thanyou have reached, restrict the water flow from the dynamometer as described in

step 8.

8. Reduce the load and throttle and let the engine cool down while running.9. After the engine has cooled, turn the engine off and increase water flow through

the dynamometer.

NOTE: When taking readings at specific intervals, the water flow through the

dynamometer may need to be adjusted to maintain the torque and the enginespeed constant.


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Report Requirements:1. Use the data sheets to record the following measured data from the dynamometer:

a. Engine speed. b. Torque.

c. Fuel consumption time.

d.

Airflow Manometer reading.e. Exhaust temperature.2. The following values should be calculated and placed in data sheet format:

a. Brake horsepower.

b. Specific fuel consumption.c. Mass flow rate of air.

d. Air/fuel ratio.

e. Volumetric efficiency.

f. Brake thermal efficiency.g. Percent heat loss.

3. Graph the torque, brake thermal efficiency, and brake horsepower (KW) as a

function of engine speed (all on the same graph).4.

Place results in tables. Make conclusions based on the results in the tables and

graphs and compare them to the ideal cycles.


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Recorded Data

Date:____________

Ambient Temperature:_________

Barometric Pressure:__________

Trial

# Speed Torque Fuel Consumption Manometer Exhaust

(rpm) (N-m) Rate (mL/s) Reading (mm H2O) Temperature (oC)

0

1

2

3

4

5

6

7

8

Calculated Data

TrialAir

FlowFuelFlow

Air/FuelRatio

BrakePower

BrakeThermal SFC Volumetric Perce

# (kg/hr) (kg/hr) (kgAIR /kgFUEL) (W) Efficiency (g /kwh) EfficiencyHeaLos

01

2

3

4

5

6

7

8


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Title: Heat Exchanger Performance (Rev. June 2011, NJL)

Purpose: The purpose of this experiment is to calculate the convective heat transfer

coefficients (h) and overall conductance (UA) for a counter flow heat exchanger using both design calculations and experimental results.

Apparatus: The experimental apparatus consists of a Hilton H-950 single tube, water-to-water turbulent flow heat exchanger test rig. The apparatus is designed so that

temperatures can be read at the locations illustrated in the figures shown in this lab. Flow

meters are provided to read the hot water and cold water flow rates.

The hot water is heated by an electric immersion heater and is re-circulated by a pump.

The cold water is from the building’s piping and is dumped after cooling the hot water.The hot water inlet temperature can be controlled by the heater power control. The

control valves can regulate both water flow rates.

The heat exchanger is a concentric (tube within a tube) type with the hot water flowing

through the inner (core) tube and the cold water flowing through the annulus (outer tube).By rearranging the water connections, the heat exchanger can be set up as a counter-flow

or parallel-flow configuration.

Temperatures at six positions are read by thermocouples giving both water temperaturesand tube wall temperatures at inlets and outlets. The tube material is copper and the heat

exchanger dimensions are as follows:

Tube length, L = 0.8700m

Inner tube (inner diam.), di = 0.0079m

Inner tube flow area, Ai = [( di2 ) / 4] = 49x10

-6m

2

Inner tube (outer diam.), do = 0.0095mOuter tube (inner diam.), Di = 0.0111m

Annulus flow area, Aa = [( (Di2 - do

2 )) / 4] = 25.9x10

-6m

2

Inner heat transfer area, Ah i = ( di L ) = 0.0216m2

Outer heat transfer area, Ah o = ( do L) = 0.0260m2


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Figure 5-3


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Theory: The following symbols will be used in the calculations and theory explanations:

Symbol Designation Units A Area m

2

C Specific Heat J/kgK

De,de Equivalent Diameter mQ Heat Transfer Rate WR Thermal Resistance K/W

U Overall Heat Transfer Coefficient W/m2K

Nu Nusselt Number unitlessPr Prandtl Number unitless

Re Reynolds Number unitless

h Convective Heat Transfer Coefficient W/m2K

k Thermal Conductivity of Fluid W/mKk T Thermal Conductivity of Tube W/mK

m

Mass Flow Rate kg/sec

T Fluid Bulk Temperature Cv Fluid Velocity m/secx Wall Thickness m

T Temperature Difference KLMTD Log Mean Temperature Difference K

Dynamic Viscosity kg/(m-s)

Density kg/m3

Four dimensionless numbers are listed in the above table with no units; the

following expressions define those numbers:

Equation 5-1: Nu = eh d

k or e

h D

k

Equation 5-2: Pr =C

k

Equation 5-3: Re = eVd

or e

VD

Where:m

V A

NOTE: de = d i for the inner tube flow area (hot water)De = Di – do for the annular flow area (cold water)


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The following numbers designate the temperatures at the indicated locations:

1 Hot steam entering the top of the heat exchanger

2 Hot steam leaving the bottom of the heat exchanger3 Metal wall at top of heat exchanger

4 Metal wall at bottom of heat exchanger

5 Cold stream at top of heat exchanger6 Cold stream at bottom of heat exchanger

Theory (Design):

Conduction is heat transfer through solids and through fluids in situations where there is

no movement of the fluid in the direction of heat flow. For one dimensional conductionthrough a flat wall, the rate of heat transfer is given by :

Equation 5-4: 1 2 1 2 1 2( )kA T T T T T T Q x x R

kA

Thermal resistance in conduction is the wall thickness divided by the heat transfer

rate, as shown in the following equation:

Equation 5-5: x

RkA

Convection is heat transfer through a fluid system by the motion of the fluid. Forced

convection occurs when a mechanical device such as a pump causes the motion of thefluid. Natural convection occurs when the heating process (through the density change ofthe fluid) causes the motion of the fluid.

Within a heat exchanger, heat transfer occurs through a combination of conduction andconvection. According to the flow rate, and the resulting Reynold’s number, the flow in a

bulk of fluid may be laminar or turbulent. At higher Reynold’s numbers, ordered laminar

flow breaks down and is replaced by random and turbulent flow. The movement withinthe fluid would then rapidly distribute the heat that has been transferred from the walls.

However, even when the bulk of the fluid has vigorous turbulent flow, the boundary layer

against the wall has the turbulent flow greatly suppressed. Due to this suppression, heat

transfer within the boundary layer is mainly due to conduction. In both laminar andturbulent flow, the rate of heat transfer to a surface is given by the following equation:

Equation 5-7: 1

F S F S F S

T T T T Q hA T T

R

hA


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Forced Convection in TubesThe large number of factors affecting convective heat transfer makes the theoretical

solution of heat exchanger problems almost impossible. To ease the problem,dimensional analysis combined with experimental investigations has yielded a number of

relationships which can be easily handled. For turbulent flow in channels of uniform

cross-section, a well-known equation for this relationship is:

Equation 5-9: Nu = 0.023 (Re0.8

) (Pr0.4

)

For convenience, the properties used in the above calculations are those at the meantemperature of the fluid. Thus, if the mean temperature values are known, or are

assumed, as well as the flow rates and dimensions of the heat exchanger, then all of the

values for Nu, Pr, and Re can be calculated.

The convective heat transfer coefficient, h can also be calculated by rearranging Equation

5-1 so that:

u

e

N k h

d or u

e

N k h

D

Finally, after those calculations are performed, UA may be calculated by noting from

equation 5-8 that1

ln1 1

2

o

i

i hi T o ho

UAd

d

h A Lk h A


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Theory (Experimental):

Temperature Distribution in Simple Concentric Tube Heat ExchangersThe temperature distribution in a concentric tube heat exchanger through which two

single-phase fluids flow in either a con-current or counter-current fashion is shown

below. The temperature difference between the two streams varies according to their position within the heat exchanger.

Figure 5-3

Heat transfer calculations are eased if a mean value of the local temperaturedifferences can be found. This value is called the log mean temperature difference ( ln)

and its value can be found using the following:

Equation 5-10: 1 5 2 6

1 5

2 6

[( ) ( )]

( )ln( )

T T T T LMTD

T T T T

The rate of heat transfer can be given by the following:

Equation 5-11: Q UA LMTD

t2

t4t3t4t3

t1 t1t2

t6 t6t5t5

METAL

M E T A L

t2

t4t6Local Temperature

Difference

t1

t3

t5 T e m p e r a t u r e

Position

COUNTER-CURRENT FLOWCON-CURRENT FLOW

Position

T e m p e r a t u r e

t5

t3

t1

Local Temperature

Difference

t6t4

t2


35/85

8

Evaluation of Heat Transfer CoefficientsBy observing the temperatures and mass flow rates of both streams and the temperatures

of the walls, the following may be calculated:

NOTE: The subscript i is used to denote the hot fluid flowing in the inner stream.

The subscript o is used to denote the cold fluid flowing in the outer stream.

1. The rate of heat transfer from the hot stream: 1 2( )inner iQ m C T T

2. The rate of heat transfer to the cold stream: 5 6( )outer oQ m C T T

Note: For Qi and Qo the appropriate mass flow rate should be used. Any

discrepancies between Qi and Qo should be explained in the conclusion

section of the report.

3. Overall heat transfer coefficient:

1 5 2 6

1 5

2 6

ln

iQUA

T T T T T T

T T

4. The convection heat transfer coefficient between inner surface of tube and the

hot stream:

1 3 2 4

1 3

2 4

ln

ii

hi

Qh

T T T T A

T T

T T

5. The convection heat transfer coefficient between the outer surface of the tube

and the cold stream:

3 5 4 6

3 5

4 6

ln

oo

ho

Qh

T T T T A

T T

T T


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9

Procedure:

1. Ensure that the water connections are aligned for a counter-flowconfiguration. The heat exchanger should already be set up for this

configuration.

2. Calibrate the thermocouples: Before opening any valves, start the hot water pump to activate the temperature indicator. Record all 6 temperatures,

compare them to room temperature and make correction factors if necessary.

3. Add water to cover the de-aerating screen in the heating tank, if required.

4. Turn on the power switches to the pump and heater. If there is no indication

of pump running (light behind switch is not on), try pressing the reset buttonor check the plug.

5.

Fully open the cooling water control valves.

6. Adjust the flow and heater controls (set the heater control to maximum

clockwise position) to achieve the desired average temperatures (maximum

hot water temperature is approximately 75°C).

7. Allow temperatures to stabilize.

8. Record the six temperatures and the mass rates of the hot and cold fluids.

9. Reduce the cold water flow in two 25% steps and record data. Allow the

temperatures to stabilize before taking readings. Be sure to take into accountthat there are two valves for the control of cold water.

10. Leaving the cold water valves in their current position, reduce the hot waterflow in two 25% steps and record data. Allow the temperatures to stabilize

before taking readings.


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10

Presentation of results:

STEP A. CALCULATING THEORETICAL VALUES

1. Calculate the mean hot and cold temperatures.

a.2

HOT OUT HOT IN

AVG HOT

T T T

b.2

COLDOUT COLD IN AVGCOLD

T T T

2. Determine the thermal conductivity, density, dynamic viscosity, and specific

heat at those temperatures using the provided chart.

3. Calculate Re for each of those temperatures.

4. Calculate Pr for each of those temperatures.

5. Calculate Nu for each of those temperatures from Equation 5-9:

Nu = [0.023 (Re0.8

) (Pr0.4

)]

6. Calculate hi and ho by rearranging:

a.,u o

o

e

N k h

D

b. ,u iie

N k hd

7. Calculate UA using the following equation:

1

ln1 1

2

o

i

i hi T o ho

UAd

d

h A Lk h A

8.

Calculate the theoretical heat transfer, Q using equation 5-8 where

HOT AVG COLD AVGT T T

9. Repeat these steps for each trial and record values in data table.


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11

STEP B. CALCULATING EXPERIMENTAL VALUES

1. Calculate Qi and Qo.

a. 1 2( )i pQ mC T T

b.

5 6( )o pQ mC T T

2. Calculate the OVERALL log mean temperature difference (LMTD).

1 5 2 6

1 5

2 6

[( ) ( )]

( )ln

( )

T T T T LMTD

T T

T T

3. Calculate hiUA and hoUA

a. i

hi

QUA

LMTD

b. o

ho

QUA

LMTD

4. Calculated the INSIDE and OUTSIDE LMTD.

a. 1 3 2 4

1 3

2 4

[( ) ( )]

( )ln

( )

inside

T T T T LMTD

T T

T T

b. 3 5 4 6

3 5

4 6

[( ) ( )]

( )ln

( )

outside

T T T T LMTD

T T

T T

5. Calculate ho and hi

a.

Average

i

hi inside

Qh

A LMTD

b.

Average

o

ho outside

Qh

A LMTD

Typical Values

U ≈ 8,000 W/m2°C UA ≈ 208 W/m

2°C

Theoretical hi ≈ 17,000 W/m2°C Experimental hi ≈ 27,000 W/m

2°C


39/85

12


1. Compare and discuss theoretical and experimental values of hi, ho, and UA.2. Discuss any inconsistencies in heat transfer from the hot to cold stream

3. Discuss how each varies with flow rate.

4.

Generally discuss experimental results.

Raw Data Sheet:

Date:_____________

Ambient Temperature:__________

Barometric Pressure:___________

Recorded Data

1 2 3 4 5

Full Open Cold 75% Cold 50%Hot75%

Hot50%

T1 ºC

T2 ºC

T3 ºC

T4 ºC

T5 ºCT6 ºC

Hot Flow Rate (gram/s)

Cold Flow Rate (gram/s)


40/85

13

You should present your

calculated results in the

following format

Calculated Theoretical Data

Hot Water

Flow setting 1 2 3 4 5

Average Temperature (ºC)

Specific Heat (J/ kg ºC)

Density (kg/ m )

Thermal Conductivity (W/ m ºC)

Viscosity (kg/ m s)Prandtl Number

Reynolds Number

Nusselt Number

hi (W/m ºC)

UA (W/ºC)

Cold Water


Average Temperature (ºC)

Specific Heat (J/ kg K)

Density (kg/ m )

Thermal Conductivity (W/ m ºC)

Viscosity (kg/ m s)

Prandtl Number

Reynolds Number

Nusselt Number

ho (W/m ºC)

UA (W/ºC)


41/85

14

Calculated Experimental Data

Hot Water


Qi (W)Overall LMTD

UAhi (W/ºC)

LMTD inside to the wall

hi (W/m ºC)

Cold Water


Qo (W)

Overall LMTDUAho (W/ºC)

LMTD outside to the wall

ho (W/m ºC)


42/85

15


43/85


44/85

2

For the purpose of this experiment, it is convenient to assume that the heating or

cooling surfaces are external to the duct. In the evaporator, heat is removed from the air

and gained by the refrigerant changing it to a saturated vapor. The heat lost by the airshould be equivalent to the heat gained by the refrigerant if we neglect any losses to

atmosphere.

The rate of heat lost by the air can be found from the energy equation:

Equation 6-1: AIROUT IN Air Air hhmQ )(

The enthalpies are found from the Psychrometric chart using wet and dry bulb

temperatures at the evaporator inlet and exit.Refrigerant (R134a) enters the evaporator from the expansion valve as a wet

vapor and leaves somewhere near a saturated vapor (probably slightly superheated). This

is because the refrigerant is gaining heat in the evaporator and this rate of heat addition

can also be found using the energy equation:

Equation 6-2: ref IN OUT f f hhmQ )(ReRe

Applying the steady flow energy equation between B and C gives us:

Equation 6-3: )( C B A A hhmQ

Where:

AQ is the rate of heat removal from the air stream

Am

is the air stream mass flow rate

hB and hC are the inlet and outlet enthalpies, respectively


45/85


46/85

4

Procedure 1. Inspect the apparatus and identify all of its components.

2. Carefully level and zero the inclined manometer for the airflow ratemeasurement using the leveling screw knob

3. Fill the main wet bulb water reservoir on the front of the unit to the indicated

maximum level and verify the attached wet bulb thermometer reservoirs arefilled/filling correctly4. Start the fan and the compressor using the appropriate controls on the

apparatus. NOTE: The instructor might have started the humidification

heater to add moisture to the incoming air.5. Adjust the fan speed control to maximum.

6. Wait until the entire apparatus reaches a steady-state condition. This has

occurred when the airflow thermometers reach a constant value.

7. While waiting for the system to reach steady-state, measure the lab’s humidityusing the sling or digital psychrometer.

8. Record all data for both air and refrigerant loops.

a.

These include:Atmospheric Pressure

Wet Bulb Room Temperature

Dry Bulb Room Temperature

Air Flow (manometer)Freon Flow (measured at the black line in the middle of the rotameter)

Evaporator Pressure

Condenser Inlet PressureCondenser Exit Pressure

T6 wet bulb out

T5 dry bulb out

T4 wet bulb inT3 dry bulb in

T13 Compressor inlet

T14 Compressor exitT15 Condenser exit

9. Repeat step 8 three times, reducing the air flow rate by 2mm each trial.

10. Turn off the apparatus.

NOTE: Be sure to check the wet bulb main reservoir regularly to ensure that they do not

dry out.


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5

Presentation / Report Requirements

1. Using a Psychrometric chart, find the required air properties, see table

2. Repeat for the inlet and exit air conditions for each trial.

3. Compare the humidity ratios upstream of the evaporator with the laboratoryvalue. Discuss any differences.

4. Find the mass rate of air from the attached manometer reading conversionchart using the curve that is closest to your experiment conditions, note you

measured the volumetric flowrate at the exit so you must also use the specific

volume of the air at the exit in your mass flow rate calculation.

5. Calculate the heat removed from the air stream for each trial.

6.

Sketch the refrigeration process for one of the trials on the pressure-enthalpychart provided.

7. Find and use the evaporator inlet and exit enthalpies to calculate

f Q -- the rate

of heat addition to the refrigerant.

a. Using the appropriate Temperatures and Pressures, use either

refrigerant property tables or the pressure-enthalpy chart to obtain theenthalpy leaving the evaporator (h OUT).

b. The enthalpy into the evaporator (h IN) is the same as the enthalpy into

the expansion valve or the enthalpy out of the condenser.i. This will either be a compressed liquid or saturated liquid.

8.

Tabulate all of your calculated data – you can model your table after the

included data table.

9. Plot the heat removal from air and heat addition to refrigerant (ordinate) on

the same graph vs. the airflow rate (Abscissa) for the all four trails and draw a best fit lines through your data

10. Compare the calculated rate of heat removal from the air and the rate of heataddition to refrigerant. Discuss any differences. Include the assessment of

heat flows not accounted for. Do not forget condensate flow rate.


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6

Data Tables


49/85

7

Date:______________

Atmospheric Pressure:_____________

Wet Bulb Room Temperature:_______Dry Bulb Room Temperature:_______

Air Flow (mm)Freon Flow (gram/sec)

T6 wet bulb exit (oC)

T5 dry bulb exit (oC)

T4 wet bulb in (oC)

T3 dry bulb in (oC)

Evaporator gage pressure (kPa)

Condenser inlet gage pressure (kPa)

Condenser exit gage pressure (kPa)

T13 Compressor inlet (oC)

T14 Compressor exit (oC)

T15 Condenser exit (oC)

Calculated Data

Evaporator absolute pressure (kPa)

Condenser inlet absolute pressure (kPa)

Condenser exit absolute pressure (kPa)

Air specific volume inlet (m /kg)

Air specific volume exit (m3/kg)

Volumetric flow rate of air at the exit(m

3/hr)

Mass flow rate of air (kg/hr)

Air Data from Psychrometric chart at 1atm

Relative Humidity at inlet

Humidity Ratio at inlet

Relative Humidity at exit

Humidity Ratio at exit

Inlet enthalpy of air (kJ/kg)

Exit enthalpy of air (kJ/kg)

Heat Removed from air (kJ/hr)

R134a Data From P-h diagram or saturation and superheated data tables

Condenser inlet enthalpy (kJ/kg)

Condenser exit enthalpy (kJ/kg)

Evaporator Inlet enthalpy (kJ/kg)

Evaporator Exit enthalpy (kJ/kg)

Heat added to R134a (kJ/hr)


50/85

8

Note, this chart is included for your convenience and can be found in your

thermodynamic textbook, along with the r134a saturation and superheated data tables


51/85

9


52/85

1




Title: Reaction Turbine (Francis turbine) (Rev. August 2011, NJL)

Purpose: To understand the basic properties and performance characteristics of a Francis

turbine .

Apparatus:The TQ Tutor pump and Francis turbine test set is a self-contained, trolley

mounted unit, and provides the means to study the characteristics of a centrifugal pump

and Francis turbine under various conditions of head, flow and velocity.

The main tank contains all necessary water so no external water supply isrequired. Within the tank is a V-notch and sight tank to allow flow discharge

measurement,

The basic centrifugal pump apparatus consists of a glass reinforced plastic (GRP)tank with two compartments, separated by a 90˚ V-notch. The GRP tank mounts on a

box section wheeled trolley, which houses the centrifugal pump and it d.c. drive motor.

Beneath the shallow end of the GRP tank is the electrical enclosure, which contains thed.c. motor speed controller and instrument panel. A discharge pipe, fitted with a ball

valve, connects between the centrifugal pump inlet and the base of the deep section of the

GRP tank.

The centrifugal pump outlet pipes, via a ball valve, to the side inlet of the Francisturbine. Figure1 1 and 2 show the unit, minus the turbine attachment and the instrument

panel respectively. The Francis turbine consists of a volute containing variable guide

vanes and an impeller. There is a transparent window for viewing the turbine inoperation, and for use with a stroboscope. For measuring torque, a disc brake assembly

using a simple spring balance is attached with a moment arm of 0.074m. An external

level allows adjustment of the guide vanes when the machine is running. The Francis

turbine can be seen in figure 3 below.


53/85

2

Figure 1 Layout of the Pump Set

Figure 2 Instrument Panel


54/85

3

Figure 3 Layout of the Francis Turbine


55/85

4

Theory: Turbines with a variety of shapes of blades are used to do work on various

systems. Based on the blade shape, the performance and therefore the useful applications

for the turbines can be determined.The two main types of turbines are the Impulse Turbine (Pelton turbine) and

Reaction Turbine (Francis turbine). They operate by passing water through an impeller

which has blades that cause a change in the direction of fluid. Thus, its momentum ischanged and the rate of momentum change will produce a force that acts on the impellerand results in rotation.

Impulse turbines use a high head (pressure) to extract a greater potential energy

from the same amount of water. This is due to the design of the cup-shaped blade tipsaround the perimeter of the wheel. Compared to the Reaction turbine, impulse wheels use

much less water but operate at a much higher head. The Pelton wheel is an example of an

Impulse turbine. The full force of water is directed against the blades of the turbine and

power is derived from the force of water at high pressure hitting the passing buckets, thusthe term “impulse” turbine. With the Pelton wheel, water is directed into the radial

buckets at an angle of 90 degrees to the shaft. The Pelton wheel however is not usually

used at lower heads due to the resulting slow rotational speed and they would require avery large impeller.

The Francis wheel is a Reaction turbine that allows water to enter the turbine in a

radial direction and is discharged in an axial direction. It consists of an impeller with

fixed vanes (blades), usually nine or more. This type of turbine is favored in low pressureapplications since, by design its capable of moving large amounts of fluid at low speeds.

However, reaction turbines rotate faster than impulse turbines given the same head and

flow conditions. The advantage of this can be seen in hydroelectric applications where itis the Francis wheel turbine that dominates large hydroelectric plants around the world

due to its high efficiency at full-flow.

The water horsepower is the measure of input in the turbine. In order to calculate

the water horsepower (WHP) of the turbine the following equation is used:

Equation 1: WHP QH

Where: H = head (meters of water)

Q = Volumetric flow rate (m3/s)

= specific weight of water (N/m3)

In order to find the flow rate in m3/s the readings from the flow tank, in mm, must

be converted first to liters/min using the 90˚ V-notch calibration chart below in figure 5.


56/85

5

Figure 5 90˚ V-notch calibration chart

The brake horsepower is the measure of the output of the turbine. In order tocalculate the brake horsepower (BHP) of the turbine the following equation is used:

Equation 2:2

BHP NT

Where: N = Speed of turbine (rpm)

T = Torque (N-m)


57/85

6

Torque is determined from knowing the breaking force and moment arm length.

The breaking force is determined experimentally. Moment arm length is taken directly

from the apparatus and is 0.074m. Torque is calculated using the following equation:

Equation 3:m

T F R

Where: F= force (N)R m= moment arm length (m)

Hydraulic efficiency is the ratio of output to input as shown in the following equation:

Equation 4: BHP

WHP


58/85

7

Procedure:

WARNING: This lab involves the use of rotating machinery; do not wear looseclothing or jewelry that could become caught in the rotating shafts!

1.

Make sure the deep side of the GRP tank is filled to the bottom of the shallow side ofthe tank

2. Turn on the pump set at the rear of the unit

3. Turn on the motor drive at the front of the instrument panel

4. Fully release the brake screw on the turbine

5. Increase the power to pump using the motor speed potentiometer until the turbineinlet read 15 mH2O

6.

Turn the spring balance tension screw until the pointer on the spring balance housingaligns with the scribed line on the brake caliper. Record the initial indication on the

spring balance as X.

7. Record the turbine inlet head

8.

Record the flow rate by reading the V-notch shelf water level sight glass in mm.

9. Record the turbine speed with a stroboscope or digital tachometer.

10. Turn the brake screw to apply a braking force until the turbine RPM has decreased byapproximately 100-200 RPM.

11.

Wait 20 seconds, and then verify the turbine inlet head is reading 15 mH2O. If it has

lowered a bit, VERY slightly increase the pump motor power with the potentiometeruntil the turbine inlet head is 15 mH2O.

12. Adjust the spring balance tension screw until the pointer on the spring balance againaligns with the scribed line on the brake caliper. Do this VERY slowly so as not to

overshoot the scribed line, the pointer will creep up slowly as you adjust the tensionscrew. Record the indication on the spring balance as Y, the braking force = X-Y

Newtons for each brake setting

13. Record the flow rate in mm

14.

Record the turbine speed in RPM.

15. Increase the braking force by adjusting the brake screw ¼ turn

16. Repeat steps 11-15 until the turbine comes to a compelte stop, always maintain 15mH2O turbine inlet head.


59/85

8


1. Tabulate all recorded data2. Calculate braking force, flow-rate, torque, BHP, WHP and efficiency

3. Plot torque and efficiency versus speed at constant head on one graph

4.

Plot BHP and WHP versus speed at constant head on one graph5. Discuss your results and the curve trends


60/85

9

Raw Data Sheet

Date: _________Lever Arm Length: _0.074m__

Initial spring balance indication, X _________

Barometric Pressure: _________Ambient Temperature: _________

Head (m H2O) Flow (mm) Speed (RPM)Spring balance

indication, Y


61/85


62/85

2

Theory: The following symbols and units will be used in the theory section of this lab

and all calculations:

SYMBOL DESCRIPTION UNITS

M Mach Number N/A

c Local speed of sound ft s

k Ratio of specific heats unitless

Pt Absolute total pressure

Inches of H20

(measured)

2

lbf

ft (for calculations)

Ps Absolute static pressure

Inches of H20(measured)

2

lbf

ft

(for calculations)

v Velocity ft

s

gc Gravitational constant 232.2 ft lbm

lbf s

R Gas constant ft lbf

lbm R

T Static temperature R

m Mass flow ratelbm

s

Density 3lbm

ft

A Cross-sectional area2 ft

Ft Internal thrust lbf

Fnet Net thrust lbf

FD Drag lbf

CT Thrust coefficient N/A

CD Drag coefficient N/A

SFC Specific fuel consumption Fuel

Thrust

lbm

hr lbf


63/85

3

When a body moves through a fluid, each element of the solid surface diverts the fluid

from the course which it might otherwise take. For example, when a projectile is moving

thr ough air, each element of the projectile’s surface area pushes the neighboring air out ofthe way and this local disturbance creates a pressure pulse that propagates into the

surrounding air. In a compressible fluid, the “pressure wave” spreads spherically from

the source with the speed of sound relative to the fluid. The nature of these pressure flow patterns depend on the comparative magnitudes of the source velocity and the sonicvelocity (speed of sound). The ratio of these two velocities is called the Mach

number, V

M c

. Therefore, the Mach number is a quantifiable description of the type of

flow.

For subsonic compressible flow, the source velocity and sonic velocity are comparable inmagnitude; however, the source velocity is less than the speed of sound. In this case,

changes in Mach number occur primarily because of changes in source velocity (V) and

only secondarily through changes in the sonic velocity (c).

For isentropic flow of a calorically perfect gas (Ideal gas with constant specific heats),

the sonic velocity (c) is a relation between pressure and density can be derived as

follows:

A common derivation in any compressible flow book for one-dimensional shock waves

gives us the following relation for the speed of sound in isentropic flow:

Equation4-1.0 2

ConstantS

P c

We also know that for isentropic ideal gases, Constantk Pv and1

v

which gives us

Equation 4-1.1 onstantk

P c

Where: P = pressure

= density

k = ratio of specific heats

Putting Equation 4-1.1 into logarithmic form, differentiating, and noting that P RT

for an ideal gas, we obtain:

Equation 4-1.2: ln ln constant P k

Equation 4-1.3:

d k

P

dP


64/85

4

Equation 4-1.4:ConstantS

P kP kRT

Thus, for the speed of sound in a calorically perfect gas we get:

Equation 4-1.5: kRT c =W

T k

Where: = Universal Gas ConstantW = molecular weight

More simply, the final equation for the speed of sound is:

Equation 4-2: RT kg c c

The Mach number can be defined in terms of the pressures and the fluid properties as

follows:

Equation 4-3:

1

21

1

k

k T

S

P M

k P

By combining equations 4-2, 4-3 and the definition of the Mach number, the velocity of

air can be found. Knowing the velocity of air and the cross-sectional area, the mass flow

rate becomes the following:

Equation 4-4: m AV

Where: V M c = c M kg RT 2

4

D A

Equation 4-5: S P

RT

Combining all of the above equations allows for mass flow rate to be calculated from the

following equation:

Equation 4-6: S c P AM m kRTg RT

NOTE: Equations 4-1 through 4-6 are valid only at the ramjets inlet and exit. Once air

enters the device, the characteristics of the flow are more complex to determine.


65/85

5

Once the air enters the device and mixes with the fuel (propane), a new gas constant must

be determined. The value for R for a mixture is dependent upon the molecular weights of

the constituents and the percentage of each substance in the mixture. The same result can be obtained from the following equation:

Equation 4-7: Air Fuel MixtureTotal

m R m R

R

m

To calculate internal thrust we use the data at the ramjet’s inlet and exit:

Equation 4-8: exit entranceThrust c

mV mV

F g

The difference between the generated, or internal, thrust and the measured, or net, thrustis the drag of the force required to overcome the drag of the engine:

Equation 4-9: _ Drag Thrust Net measured F F F

For comparison with other devices, the thrust coefficient and drag coefficient are usually

used. The thrust and drag coefficients can be calculated as follows:

Equation 4-10:

21

2

Thrust

T

Max S Entrance

F C

A kP M

Equation 4-11:

21

2

Drag

D

Max S Entrance

F C

A kP M

Where: Amax = maximum cross-sectional flow area of the jet


66/85

6

The specific fuel consumption tells us how much thrust is being generated per unit fuel

being burned. The specific fuel consumption is defined by the following equation:

Equation 4-12: Fuel

Thrust

mSFC

F

Equation 4-13: fuel supply Absolute

fuel supply Absolute

530237 %

44.7 fuel

P m flow

T

2

NOTE: In the above equation, mass flow rate units are

Pressure units are

Temperature units are

% fuel flow is the fractional percentage

lbm

hr

lbf

in

R

Figure 4-2 Ramjet internals/scaling


67/85

7

Procedure:

NOTE: SAFETY IS OF PARAMOUNT IMPORTANCE. HEARING PROTECTIONS

IS REQUIRED AT ALL TIMES. FOLLOW THE PROCEDURE CLOSELY AND BEAWARE OF FLAMES AND HOT SURFACES.

1.

Move the pressure probe in and out of the ramjet. Not where the entrance andexit positions of the ramjet are.

2. Move the probe to the maximum upstream position. This will be the 0-inch

position. Data will be taken at one-inch intervals for the full movement of the probe (Pt, Ps, Psupply).

3. Ensure the igniter is plugged in.

4. Look into the tail end of the ramjet, press the igniter button, and make sure a

spark is present.

5.

Start the cooling water for the pressure probe at the maximum pressure

achievable. Check at regular intervals to ensure that the water is still flowing.

IF THE COOLING WATER IS NOT USED, THE PROBE WILL MELT!

6. Make sure the indoor gas supply shut-off valves (ball valve and gate valve)

are closed.

7. Turn on the supply valve at the propane tank outside in the fenced area.

NOTE: Follow the steps closely to bleed air and high pressure from the lines

to prevent potential hazards.

8.

Open the fuel control valve (red knob on the control panel) one to two turns.

9. Open the ball valve by turning the yellow handle 90° making sure the gatesupply valve (gray knob downstream from the ball valve) is closed.

10. SLOWLY crack open the gate valve (gray knob) allowing fuel to bleed.Establish a small flow for about 5 seconds.

11. Close the fuel control valve (red).

12. Fully open the gate valve (gray).

13. Push in the air damper and start the fan. Allow the fan to reach full speed

before proceeding.

14. Obtain about 5 inches of H2O air pressure by slowly opening the air damper.


68/85

8

15. While holding in the ignition button, slowly open the fuel control knob and

allow fuel flow to increase. [Ignition should occur around 40% (refer to fuel

flow measurement figure). If ignition occurs outside of the ramjet, decreasethe fuel supply until the flame originates inside the tube. NOTE: Starting the

ramjet is not a “cut and dried” procedure, some fiddling is required to get it

started.]

16. After establishing a good straight flame, increase the airflow and the fuel flow

simultaneously to increase thrust. Allow airflow to maximize. Thrust should

be anywhere between 2-3 lbf. With the amount of airflow present, fuelsupply should not exceed 55%.

17. While maintaining constant thrust, take data at one-inch probe intervals.

18. Close the fuel supply valve.

19.

After 5 minutes, shut off the fan.

20. Close the ball and gate fuel supply valves.

21. Open the fuel control valve until fuel flow ceases. Close the valve.

22. Shut off the probe cooling water.

23. Close the fuel tank valve outside and secure the fenced-in area.


69/85

9

FUEL FLOW MEASUREMENTFUEL TO RAMJET

TAKEREADING

HERE

FUEL FROM TANK

Figure 4-3 Fuel Flow Measurement

Figure 4-4 Sample Graph


70/85

10


1. Prepare a table and plot on the same graph the total and static pressure(ordinates) versus probe position (abscissa). Indicate the positions of the inlet,

outlet, flame holder, and fuel spray bars on the graph.

2.

Perform the following calculations:a. Note the entrance and exit positions and record Pt and Ps for both. b. At the entrance, calculate the Mach number, velocity, and mass flow

rate (k=1.4).

c. At the exit, calculate temperature, velocity, Mach number, and massflow rate (k=1.3).

i. First calculate the exit mass flow rate:

[

m exit =

m air (in) +

m fuel].

ii. Then calculate the exit Mach number from Equation 4-3.iii. Calculate the exit temperature from Equation 4-6.

iv. Calculate the exit density from equation 4-5.

v.

Calculate the exit velocity from equation 4-4.d. Calculate the internal thrust.e. Calculate the drag.

f. Calculate the specific fuel consumption.

3. Discussion:

a. Compare the calculated drag to the measured drag and offer reasons

for the difference.

b. Discuss the results to previous tests or other known data.c. Discuss the shapes of the curves.


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Raw Data Sheet

Date:___________

Ambient Temperature:__________

Barometric Pressure:___________

Air Supply Temperature:_____________ Air Supply Pressure:_____________

Fuel Supply Temperature:____________ Fuel Supply Pressure:____________

Measured Trust:________lbf Measured Drag:_________lbf

Percent Fuel Flow:______%

StaticPressure Probe

Position

(inches)

Static Pressure

(inches H2O gage)

TotalPressure Probe

Position

(inches)

Total Pressure

(inches H2O gage)

-3 -4

-2 -3

-1 -2

0 (Ent) -1

1 0 (Ent)

2 1

3 24 3

5 4

6 5

7 6

8 7

9 8

10 9

11 10

12 11

13 1214 13

15 (Exit) 14

16 15 (Exit)


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Title: Steam Power Plant (Rev. August 2011, NJL)

Purpose: To gain hands-on experience in the operation of a small steam power plant.

The student will analyze the operation of some power plant components. In addition, the

student must demonstrate the ability to convey a system description by developing an

engineering diagram for the power plant setup by tracing out the system and itscomponents.

Apparatus: The steam power plant is comprised of the normal Rankine Cycle

components: a boiler, condenser, turbine, and feed water pump. The student will use a pen, pencil, or computer-aided drafting program to represent the apparatus setup. This

drawing will be sketched before beginning the experiment. Most valves and measuring

devices are labeled to indicate their associated function (i.e. “B” for boiler, “T” forturbine, “CW” for cooling water, etc.). Some flow measuring devices are provided. The

load placed on the turbine is an electrical generator with a resistive load bank attached.

The load can be varied using the dials on the load bank apparatus. The heat rejectionsystem consists of a cooling tower, a shell and tube condenser, and air removal

equipment (the air ejectors will not be used in this experiment). The cooling tower

located outside provides cooling water. A propane-fueled boiler provides steam. The

student should be familiar with the location of the components and valves to bemanipulated prior to the start of the experiment.

Experimentally Determined Constraints:

Boiler Mass Flow Rate: Bm

= 35.1 lbm/cycle

Fuel Mass Flow Rate: f m

= 40.2 lbm/hr

Condensate Volumetric Flow: Vc = 0.00682 ft3/6”

Air Ejector Mass Flow Rate: Mae = 109 lbm/hr


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Apparatus:

Figure 1 Steam Plant General Diagram

Theory:

Point Properties:

Boiler inlet: The sub-cooled water enters the boiler. Two properties are needed

to determine the state:

Tbi the boiler inlet temperature read directly from the thermometer.Pbi the boiler inlet pressure read directly from the gage.

Boiler outlet: The saturated water-vapor mixture leaving the boiler since our

boiler does not superheat the steam. One property and the vapor quality are

needed to determine the state:Pb the boiler steam pressure read directly from the gage.

Xbe the steam vapor quality indirectly determined by expanding

vapor through an adiabatic throttling calorimeter, the outletvapor must be in the superheated region for the analysis to

hold.


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Turbine inlet: The turbine inlet enthalpy is assumed to be equal to the boiler

outlet enthalpy since again, the water entering the turbine is a saturated water-vapor mixture, we can however still measure the turbine inlet conditions:

Tti the temperature of the steam entering the turbine.

Pti the pressure of the steam entering the turbine.

Turbine exhaust: For most conditions, the turbine exhaust will be slightly

superheated. The state can be determined from the following:

Tte the turbine exhaust temperature (not used in this experiment).

Pte the turbine exhaust pressure.

Condenser: The properties of the condenser are already determined. The

following information is needed:

Pc – the condenser pressure (it operates at atmospheric pressure).

the condenser mass flow rate which can be read directly.

Tc the temperature of the condenser which can be read directly.Tcwi the cooling water inlet temperature which can be read directly.

Tcwe the cooling water exit temperature can be read directly.

Pae the air ejector steam pressure (not used in this experiment).

Turbine Generator: The following data will be required to calculate efficiencies

and work rates:

Fm the moment force applied to the 6-inch arm.

V the generator voltage (is to be adjusted to 110 V).

I the generator current.

N the turbine generator angular velocity (expressed in rpm).


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Adiabatic Throttling Calorimeter:

“Well Insulated” The Throttling Process

Figure 2

For the adiabatic throttling calorimeter, the following equations are used:

exit i eboiler C C h h h

We know the calorimeter is open to the atmosphere and is superheated so all we

need is to measure the Temperature at the calorimeter exit and using the superheated

tables atmospheric pressure we can findeC

h

Now that we know the boiler exit enthalpy we can find its quality and entropy

@

@

exit boiler

exit

boiler

boiler f P

boiler

fg P

h h x

h

@ @exit boiler exit boiler boiler f P boiler fg P s s x s


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Simple Rankine Cycle:

Figure 3 Ideal Rankine

See chapter 10 in your thermodynamics textbook for a review of the Rankine cycle


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Actual Cycle Analysis:

Figure 4 Our cycle

Notice what is happening between states 1 and 2. When our feed-water leaves thecondenser it is pumped into a storage tank and sits until the second feed-water pump

delivers it to the boiler. The second pump does not run continuously and cold city water

is added to the storage tank as the boiler loses steam to the environment in order tomaintain the proper water level in the boiler. We do not have temperature or pressure

gages between states 1 and 2 and due to mixing with cold city water the temperature ofthe feed-water entering the boiler is actually lower than the temperature of the feed-water

exiting the condenser. Because of all this we ignore the work of the pumps since they aresmall relative to the turbine work.


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I) Fixing your states using the steam tables in your text or another reference:

State 1: 1 @ (compressed liquid approximation)condensor condensor

f T

condensor

T h h

P

State 2: 2 @ (compressed liquid approximation)boiler inlet boiler

boiler inlet

f T

T h h

P

State 3: 3 exit i eboiler C C h h h h

3 @

3

@

boiler

boiler

f P

fg P

h h x

h

3 @ 3 @boiler boiler f P fg P s s x s

State 4: Assume an isentropic efficiency for the turbine of 80%

4 3

4

3 44

3 4

find

0.8 Solve for

s

s

Turbine exit

aT a

s

s sh

P

h hh

h h

II) Cycle performance:

Recall we define performance asDesired Output

Required Input

a) Find mass flow rate of fuel

time fuel is on in seconds40.2

total fuel on/off cycle time in seconds fuel

lbm

hr

b) Find mass flow rate of the steam in the cycle

3

1condensate flow time in seconds

0.00682

specific volume at state 1

condensate steam

condensate

condensate

condensate

V mv

V ft

v


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c) Calculate the boiler efficiency

3 2 steam

B

fuel

m h h

m HV

Watch your Units!

Where HV is the heating value of propane, 20,895 BTU

lbm

d) Calculate the thermal efficiency, neglecting the pump work

3 4

3 2

aT th

in

h hw

q h h

Watch your Units!

e) Calculate the Mechanical efficiency

3 4

2 shaft M

steamT a

W NT

W m h h

Watch your Units!

Where Torque is the measured spring force times the moment arm of 0.5feet

f) Calculate the electrical efficiency

2

E

E shaft

W V I

NT W

Watch your Units!

g) Calculate the overall cycle efficiency

O B th M E

fuel

V I

m HV

Watch your Units!


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Procedure:

INITIAL WARNINGS/NOTES:

1. All procedures must be followed to prevent equipment damage or injury.

2.

READ ALL PROCEDURES BEFORE ATTEMPTING TO START THEEXPERIMENT.3. The piping and components of the steam plant may exceed 350°F. The

electrical equipment operates at high voltages. The steam driven equipment

rotates at high speeds. The following rules must be observed at all times:

a. DO NOT TOUCH PIPING OR COMPONENTS.

b. DO NOT WEAR LOOSE CLOTHING OR JEWELRY

c. DO NOT PLACE BOOK BAGS NEAR THE STEAMPLANT.

d. DO NOT TAMPER WITH THE ELECTRICAL CIRCUITS.4. If boiler ignition does not occur during light off, do not attempt to restart it more

than once before resetting the ignition system. Open the control box in the frontof the boiler and hit the reset button before attempting to restart a second time.

5. The turbine must be warmed up properly to prevent damage to the turbine blades

or bearings.6. When changing loads on the turbine generator, turn off the selector switch on the

load panel prior to changing any loads.

7. Prior to recording initial data, the errors of the instruments should be

recorded in table 1 for future correction of the data.

PRE-WARMUP PROCEDURE (TO BE PERFORMED OUTSIDE IN FENCED-INAREA)

1. Open the fuel storage tank valve (5B). 2. Close all drain valves on the cooling water tower (4CW, 5CW, 7CW, 8CW). 3. Shut the pump and fan motors disconnect switches.

BOILER START-UP

1. Open the boiler bottom blow valve (8B) and its quick-closing valve to lower the

water level to within the proper band on the boiler sight glass. Then close the

valve (8B). 2. Open the condensate receiver make-up fill valve (3C). 3. Open the feed water pump suction valve (4C) if it is closed. 4. Open the city water supply valve (WS1). If the water level in the boiler is low,

the pump will start automatically to fill the boiler when power is turned on. 5. Open the feed water valves (3B, 4B) if closed.


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6. Open the boiler steam stop valve (1B) ONE TURN AND open the steam drain

valve (1T) ONE TURN to allow air evacuation during the warm-up period. 7. Start up the burner.

BURNER START-UP

1. Trace the fuel line from where it enters the building to the burner and make sure

the pilot valve is on.

2. Energize the switch designated BOILER at the motor control box.3. Turn on the burner switch on the burner control panel. The burner blower will

start and the burner control will go through its flame safety sequence.

4. When the fuel-on light indicates ignition, open the fuel line valve (7B).

NOTE: If ignition does not occur, check the pilot light valve and set the RESETinside the motor control box.

The boiler will require about 50 minutes to warm-up. After about 30 minutes, whenthe boiler pressure shows about 5psig, close the boiler steam stop valve (1B). If

necessary, drain water through the bottom blow valve (8B) to maintain water in

proper band on the boiler sight glass. Once the boiler is warmed up it should be

between 120 and 130 psig

HEAT REJECTION SYSTEM START-UP

1. Open the tower make-up water supply valve (1CW). A float valve in the sump

will maintain the water level automatically.

2. Open the condenser cooling water outlet valve (4CW) ONE TURN.

3. Start the circulating pump by energizing the switch on the motor control panelmarked “cooling tower”.

4. Adjust the flow meter outlet valve (4CW) to 30gpm or wide open.

TURBINE WARM-UP AND START-UP

NOTE: Condensate in the turbine and steam supply lines will cause turbine blade

erosion and put excessive thrust on the bearings. This condensate must be removed

during the warm-up period.

1. Reset the turbine over speed trip by rotating the trip valve 90° and engaging the

lever into the pin on the valve wheel. Ensure that the trip mechanism is

operating freely.

2. Fully open the nozzle valve (5T), if it is closed.3. Open the steam drain valve (1T) HALF A TURN.

4. When the steam line is free of liquid, the strainer drain valve (1T) may be

closed.5. Fully open the boiler steam stop (1B).


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6. Fully open the turbine casing drain valve (3T).

7. Open the turbine inlet valve (2T) approximately ¼ turn.

8. When the discharge from the turbine casing is mainly vapor, fully close theturbine casing drain valve (3T) and then reopen valve (3T) ½ turn.

9. Slowly open the turbine inlet valve (2T). The turbine should be operated at

1,000 rpm for several minutes until the casing drains are free of condensate.10. Close the turbine casing drain val

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MET 387 Course Pack - Copy (2)