hvac – air handling unit
DESCRIPTION
hQ = 200,000 Btu/h. HVAC – Basic Terms. cQ. assumeto = 20. tr = 70. CO2. 50 people. 20 cfm/pers. tsi = 105. 1000 cfm. 20%. coil Q = V*rho *cp*TD 5000 cfm. ti = 62. hQ vent = V*rho*cp*TD. Heating. Ventilating. AC =Cooling. HVAC – Air Handling Unit. HVAC – Basic Terms. - PowerPoint PPT PresentationTRANSCRIPT
HVAC – Air Handling Unit
Heating
Ventilating
AC =Cooling
HVAC – Basic TermshQ = 200,000 Btu/h
CO220 cfm/pers
50 people
1000 cfm
cQassumeto = 20 tr = 70
ti = 62
tsi = 10520% coilQ= V*rho*cp*TD
5000 cfm
hQvent = V*rho*cp*TD
HVAC – Basic Terms
By Conduction Convection
Radiation
(Heating Load) Heat Out = Heat In
(Cooling Load including “Latent Load”)
Heat and Humidity in = Heat and Humidity out
HVAC – Basic Terms
Conduction
AreaTemperature
Resistance
HVAC – Basic Terms
Conduction
Convection
Radiation
HVAC – Basic Terms
HVAC – Basic Systems Heating
hQsen + hQvent = coilQsen
hQsen = 200,000 Btu/h
HVAC – Basic Systems Heating
w
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HVAC – Basic Systems - AC
AC
Water to Water
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HVAC – Basic Systems - AC
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HVAC – Basic Systems - AC
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HVAC – Basic Systems - AC
Constant Volume Double Duct Terminal Box
Damper blades change air flow as the pressure at the inlet to the box increases or decreases and in response to room temperature
Variable Volume Single Duct Terminal Box
Pressure Independent (between Max and Min), based on room thermostat. If temperature rises, damper opens for more cooling.
Air Flow is unaffected by other boxes in the system.
55 – 60o
P SensorThermostat = Master
Velocity = Sub Master
cfm
Inlet Guide Vanes
Variable Speed Drives
Variable Speed Drives
Variable Speed Drives
Variable Speed Drives
COP – dimensionless! –
EER – dimensions of
Btu/h/W!
HVAC - Cooling
ideal
evQ
kpH’
The energy efficiency rating (EER) of an air conditioner is its BTU/h rating over its Wattage.
Example: window air conditioner Rating: 10,000-BTU/h Power Consumption: 1,200 watts EER = 10,000 BTU/h/1,200 watts = 8.3 Btu/Wh
Normally a higher EER is accompanied by a higher price.
HVAC - Cooling
Choice between two 10,000-BTU/h units
1. EER of 8.3, consumes 1,200 watts2. EER of 10, consumes 1000 watts.
Price difference is $100. Usage: 4 months a year, 6 hours a day. Electricity Cost: $0.10/kWh. ===========================================4 mo. x 30 days/mo. x 6 hr/day = 720 hours
(720 h x .2 kW) x $0.10/kWh = $14.40 Savings
Since the EER 10 unit costs $100 more, it will take about seven years for this more expensive unitto break even
HVAC - Cooling
Energy AnalysisExample
ECM: Heat Recovery