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© 2012 CLEAResult │ All rights reserved.© 2012 CLEAResult │ All rights reserved.
HVAC and Mechanical SystemOverview
© 2012 CLEAResult │ All rights reserved.
Objectives
Cooling Systems Types Geothermal Heat Pumps Cooling Mode Heating Mode
Variable Refrigerant DX Units
© 2012 CLEAResult │ All rights reserved.
Cooling System Types
Air (DX) Systems –refrigerant directly cools air Chilled Water - air
cooled Chilled Water - water
cooled Thermal Storage – ice
and chilled water
© 2012 CLEAResult │ All rights reserved.
Geothermal Heat Pumps
Geothermal Heat Pumps (20 EER and above)
© 2012 CLEAResult │ All rights reserved.
Efficiency from Within the Earth
Geothermal uses heat from the earth during the heating season, at an efficiency up to 500%, and returns it during the cooling season.
The most energy efficient, environmentally clean, and cost-effective space conditioning systems, according to US EPA
Taps into relatively constant temperature of the earth to save 25% to 40% of energy use
Lowest emissions among all heating & cooling technologies
© 2012 CLEAResult │ All rights reserved.
Cooling Mode
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Heating Mode
© 2012 CLEAResult │ All rights reserved.
What is a VRF or VRV System?
Variable refrigerant flow (VRF) also known as variable refrigerant volume (VRV).
A sophisticated control system enables switching between heating and cooling modes
Applications: office, retail, hotel, luxury apartments, industrial, new and retrofitted buildings
© 2012 CLEAResult │ All rights reserved.
VRF/VRV Systems
© 2012 CLEAResult │ All rights reserved.
VRF/VRV Systems
The refrigerant flow is varied using either an inverter controlled variable speed compressor, or multiple compressors of varying capacity in response to changes in the cooling or heating requirement within the air conditioned space.
In more sophisticated versions, the indoor units may operate in heating or cooling mode independently of others
This offers energy savings when heating and cooling are required simultaneously in different zones
VRV systems require no internal plant room space and works with many types of air handling units available
© 2012 CLEAResult │ All rights reserved.
Motors, Pumps, Fans
Motor HP power reduction
Motor & Pump retrofit Adding VFD or VSD
controls on motors, pumps, and fans
3
2
=
=
old
new
old
new
old
new
old
new
CFMCFM
HPHP
CFMCFM
SPSP
3
2
=
=
∆∆
old
new
old
new
old
new
old
new
GPMGPM
HPHP
GPMGPM
PP
Fan Law Pump Law
© 2012 CLEAResult │ All rights reserved.
Pump Affinity Laws
3
2
1
2
1
2
2
1
2
1
2
1
2
1
=
=
=
NN
BHPBHP
NN
HH
NN
QQ With impeller diameter
held constant:
Where: Q = Capacity, GPM H = Total Head, Feet BHP = Brake Horsepower N = Pump Speed, RPM
© 2012 CLEAResult │ All rights reserved.
Pump Curves
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Compressed Air
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Objectives
Parts of a Compressed Air System Types of Air Compressors Compressed Air Energy Efficiency Compressor Controls Reducing System Pressure Air Leakage Cooler Inlet Air Sizing Compressed Air Receivers
© 2012 CLEAResult │ All rights reserved.
Compressed Air System
© 2012 CLEAResult │ All rights reserved.
Compressed Air System
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Types of Air Compressors
Reciprocating Compressors 1/2HP & 1cfm to 1,250 HP &
6,300cfm Uses reciprocating motion of a
piston in a cylinder to compress air
Rotary Screw Compressors Sizes 30cfm to 3,000cfm Positive displacement units,
that increases pressure through the action of two intermeshing rotors.
Centrifugal Compressors Sizes 400cfm to 15,000cfm Uses high speed rotating
impellers to accelerate air
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Compressor Controls
Start/Stop: Frequently used by small reciprocating
compressors. Compressor turns itself off and draws no
power as long as the discharge pressure remains above a specified level
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Compressor Controls
Load/Unload Control: the compressor runs fully loaded, producing
compressed air at maximum efficiency until the discharge pressure reaches the upper activation pressure setting, which causes the compressor to unload. When unloaded, the compressor no longer
adds compressed air to the system, but the motor continues to run.
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Compressor Controls
Modulation Control: the inlet air valve to the compression device is
continuously adjusted, restricting the inlet air to vary the compressed air output to meet the demand on the system. Auto-dual control is a combination of modulation
and load/unload control in which the compressor operates in modulation control down to a specified pressure and switches to load/unload control below this pressure.
© 2012 CLEAResult │ All rights reserved.
Compressor Controls
Variable Speed Drive: As system pressure rises toward a set point,
the variable frequency drive reduces compressor speed by reducing the frequency of the power it supplies to the motor. As system pressure reduces, signaling a need
for more air, the drive increases compressor speed by increasing the frequency of the power to the motor.
© 2012 CLEAResult │ All rights reserved.
Cost for Different Control Modes
% Load Modulating
Load/Unload with 1 gal/cfm
Receiver
Load/Unload with 10 gal/cfm
Receiver Variable Speed
Drive100 $36,130 $36,130 $36,130 $36,850 75 $33,420 $34,680 $29,350 $27,090 65 $32,330 $33,240 $27,820 $23,480 50 $30,710 $31,070 $24,200 $18,060 25 $28,000 $24,930 $16,800 $9,030 10 $26,370 $16,620 $11,740 $3,610
Approximate Annual Cost for a 100 HP Compressor at Different Control Modes
Based on $0.10 per kWh and 4,250 hours per year
© 2012 CLEAResult │ All rights reserved.
Cool Inlet Air
Cool air intake leads to a more efficient compression.
The colder the incoming air the more the air that can be packed in for each revolution of the air compressor.
Deg F Eff. of Air Delivery
-10 1.155
0 1.130
10 1.104
20 1.083
30 1.061
40 1.040
50 1.020
60 1.000
70 0.980
80 0.961
90 0.944
100 0.928
Effect of Intake Temperature on Air Compressor Delivery
© 2012 CLEAResult │ All rights reserved.
Air Leakage
Where: T = on-load time (minutes) t = off-load time (minutes)
(Ex.) 100 HP compressor rated at 400 cfm is loaded for 2 minutes and unloaded for 3 minutes
for this example 2/5 = 0.4. This indicates the compressor is loaded 40% of the time.
The leak load would then be 40% of 400 cfm or 160 cfm.
For Load/Unload Compressors
( )tTTLeakage
+×
=100%
Where: V = the system volume in cubic feet P1 = the operating pressure in psig P2 = the pressure after time t (in
minutes) and should be a point equals to about one-half the operating pressure P1
t = time in minutes, it takes for the system to drop to one-half the operating pressure P1
The 1.25 multiplier corrects leakage to normal operating pressure, allowing for reduced leakage with falling pressure.
tPPVCFMLeakage 25.17.14)()( 21 ××−×
=
Compressors with different capacity control
© 2012 CLEAResult │ All rights reserved.
Benefits of Compressed Air Receivers Dampens pulsations caused by reciprocating
compressors. Supplying peak demands from stored air without
needing to run an extra compressor. Reducing load/unload or start/stop cycle
frequencies to help screw compressors run more efficiently and reduce motor starts.
Allows for better compressor control and more stable system pressures.
Separates moisture and oil vapor, allowing the moisture carried over from the after-coolers to precipitate.
© 2012 CLEAResult │ All rights reserved.
Compressed Air Rules of Thumb
Approximately 90% of the energy to produce and distribute compressed air is lost. Only about 10% of energy reaches the point of final use.
A 50 hp compressor rejects approximately 126,000 btu per hour (available for heat recovery)
4 cubic foot per minute (CFM) per 1 motor hp (horsepower)
1 hp = 0.746/0.9 = 0.829kW
Therefore; 1 CFM = 0.207kW
© 2012 CLEAResult │ All rights reserved.
QUESTION THUS FAR?