These are defined by the cooling effect in Btu (not in tons) divided by the power use in watts (not in kW) for the peak day (EER), or the seasonal average day (SEER).
For room air conditioners, the commonly used efficiency ratio is the
EER - Energy Efficiency Ratio
For central air conditioners, it the ratio used is
SEER - Seasonal Energy Efficiency Ratio
These ratings are posted on the Energy Guide Label, which shall be attached to all new air conditioners.
Some of the air conditioner manufacturers participate in the voluntary EnergyStar labeling program where EnergyStar-labeled appliances mean that they have high EER and SEER ratings.
EER - Energy Efficiency Ratio
Room air conditioners in general range from 5,000 Btu per hour to 15,000 Btu per hour. Select room air conditioners with EER of at least 9.0 for mild climates. In a hot climates, select air conditioners with EER over 10.
SEER - Seasonal Energy Efficiency Ratio
For central air conditioners there is units with SEERs reaching nearly 17.
Example - EER
A cooling unit operating at 1 kW/ton would have an EER of 12,000 Btu divided by 1000 watts or 12. This is mathematically equivalent to multiplying the COP by 3.413. Therefore a small cooling unit operating at 1 kW (1000 watts) per ton is equivalent to a COP of 3.516, or an EER of 12.
Labels: air conditioner system, hvac system
The sensible heat in a heating or cooling process of air can be expressed as
hs = 1.08 q dt (1)
where
hs = sensible heat (btu/hr)
q = air volume flow (cfm, cubic feet per minute)
dt = temperature difference (oF)
Latent Heat
The latent heat due to moisture in the air can be expressed as:
hl = 0.68 q dwgr (2)
or
hl = 4,840 q dwlb (3)
where
hl= latent heat (btu/hr)
q = air volume flow (cfm, cubic feet per minute)
dwgr = humidity ratio difference (gram water/lb dry air)
dwlb = humidity ratio difference (lb water/lb dry air)
Total Heat - Latent and Sensible Heat
Total heat due to both temperature and moisture can be expressed as:
ht = 4.5 q dh (4)
where
ht= total heat (btu/hr)
q = air volume flow (cfm, cubic feet per minute)
dh = enthalpy difference (btu/lb dry air)
Total heat can also be expressed as:
ht = hs + hl
= 1.08 q dt + 0.68 q dwgr (4)
Example - Heating Air
An air flow of one cfm is heated from 32 to 52oF. Using (1) the sensible heat added to the air can be expressed as:
hs = 1.08 1(cfm) (52 - 32)(oF)
= 21.6 (btu/hr)
Labels: air conditioner system, hvac system
In a chilled-water system the air conditioner cools water to between 40 and 45oF (4 and 7oC). The chilled water is distributed throughout the building in a piping system and connected to air condition cooling units wherever needed.
Total Heat Removed
The total heat removed by air condition chilled-water installation can be expressed as
h = 500 q dt (1)
where
h = total heat removed (Btu/h)
q = water flow rate (gal/min)
dt = temperature difference (oF)
Evaporator Flow Rate
The evaporator water flow rate can be expressed as
qe = htons 24 / dt (2)
where
qe = evaporator water flow rate (gal/min)
htons = air condition cooling load (tons)
Condenser Flow Rate
The condenser water flow rate can be expressed as
qc = htons 30 / dt (2)
where
qc = condenser water flow rate (gal/min)
htons = air condition cooling load (tons)
Labels: air conditioner system, hvac system