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

w

HVAC – Basic Systems - AC

AC

Water to Water

w

A

HVAC – Basic Systems - AC

A

A

HVAC – Basic Systems - AC

w

A

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