overview - el paso electricpumps, and fans. 3 2 ... parts of a compressed air system types of air...

© 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


Cooling System Types

Air (DX) Systems –refrigerant directly cools air Chilled Water - air

cooled Chilled Water - water

cooled Thermal Storage – ice

and chilled water


Geothermal Heat Pumps

Geothermal Heat Pumps (20 EER and above)


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


Cooling Mode


Heating Mode


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


VRF/VRV Systems


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


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


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


Pump Curves

© 2012 CLEAResult │ All rights reserved.© 2012 CLEAResult │ All rights reserved.

Compressed Air


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


Compressed Air System


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


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


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.


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.


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.


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


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


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


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.


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


QUESTION THUS FAR?

overview - el paso electricpumps, and fans. 3 2 ... parts of a compressed air system types of air...

Documents