Lecture Objectives:

• Finish with thermal storage systems

• Learn about plumbing systems

Construction and benefits Active

Passive (wall)

Modeling(stratified tank)

Write energy and mass balancer equation for each section

Installation of thermal storage system

DownstreamUpstream

• Increases chiller efficiency • Increases chiller capacity • Overall system efficiency ??? • Decreases storage capacity• Simplifies system layout• …..

• Decreases chiller efficiency• Decreases chiller capacityOverall system efficiency ???• Increases storage capacity•……• Does not allow chiller shut down!

Plumbing Systems - Hydronic Terms

• Head loss

• Open-loop vs. closed loop

• Open System

• Closed System

Pump

h

Cooling coil in AHUChiller

Pump

Is this open or closed system ?

Cooling towers

Relationship between velocity in a pipe and pressure drop

Δp ~ v2

Δp = Constant × v2

Δp

[Pa

or

ft w

ater

]

v [m/s or fpm]

larger pipesmaller pipe

Required power (P) for the pump

P = V × Δp P –power [W],

V –volume flow rate [m3/s], v – velocity [m/s]

Δp – pressure drop [Pa]

Δp ~ v2 (Δp ~ V2 – when same pipe is used)

P ~ V × V2 – when same pipe is used

P ~ V3 P2/P1 = (V2/V1)3 For the same pipe

When different pipe is used for the same flow rate:

For the same

flow rate V

Reduction of D:

D1

D2= D1/2 A1

V1

P1

A2=1/22 A1

V2=22 V1

P2/P1 = (D1/D2)4 - for the same flow rate

or 50% smaller diameter of the pipe

for the same flow rate wee have:

4 times larger velocity

16 times larger pressure drop and

16 times lager power for the pump

Head Loss

Fittings

g

Vkh

2

2

Pumps• Raise pressure and produce flow

• Main type• Centrifugal

Inline Base mounted

Example of Turbine pump

Reading (textbook)Page 3-36 - 3-45

Pump curves

• NPSHR = Net Positive Suction Head Required

Changing Pump Speed

Net Positive Suction Head(cavitation)

Curve for Multiple Pumps

System Curves

A B∆p

V

A+B

ParallelA B

A B

∆p

V

A+B

A

B

Serial

Find a system curve for this plumbing configuration

Primary/Secondary and Tertiary Pumping (schematics A&B below)

Taylor, S., P. Dupont, B. Jones, T. Hartman and M. Hydeman. 2000. Chilled water plant design guide. San Francisco: Pacific Gas & Electric Company.

http://www.taylor-engineering.com/downloads/cooltools/EDR_DesignGuidelines_CoolToolsChilledWater.pdf

Reading Assignment:

System balancing

BOILER

HC2

AHU1 AHU2

HC1

pump

100 ft 1000 ft

2 gpm 10 gpm

10 ft

Valves• Section 5-14 and 6-15 in the textbook

• Types• Butterfly Valves

• Ball Valves

• Globe Valves

Three way valves

Valve Sizing and Flow Coefficient

Cv value:

in liter/hour or….

in Pa

Control Valve Selection For Hydronic Systems reference:http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCUQFjAA&url=http%3A%2F%2Fbookstore.ashrae.biz%2Fjournal%2Fdownload.php%3Ffile%3Dhegberg.pdf&ei=IvcqU_O1KMuE2AWgloHgDA&usg=AFQjCNFRAMzPnbzDpAluhyk4l8u_SKKTdw

Control Valve Selection For Hydronic Systems

Before DC we tried to do this

Valve authority