Question

3. A cold storage facility is maintained at 20°F when the outside air temperature is 90°RF by an air conditioning unit operating as a cycle at steady state. The unit must remove 120,000 Btu/h continuously from the facility to maintain the required indoor temperature, and has a power input of 20 hp Determine: the actual coefficient of the air conditioning unit the minimum theoretical horsepower that would be required to operate a cooling unit under these conditions. (1hp 2545 Btu/h) a. b. TH=90°F Cold Storage 120,000 Btu/h Facility Tc 20°F A/C,Unit Weycle =20 hp

Answer 1

Given Data:

!) Cold storage maintained at 20⁰ f

2) Outside air temperature at 90⁰f

3) Heat Removal= 120000 Btu/h

4) Power input= 20 hp

To Determine:

1) The actual coefficient of the air conditioning unit

2) The minimum theoretical horsepower required to operate a cooling unit under these conditions

Solution

1) Actual coefficient of air conditioning unit

actual heatremoval actual powerinput

120000 20x2545

Actual coefficient of performance= 2.36

2) Minimum theoretical horsepower required

T2 Theoretical COP = T1-T2

Provided T1= Higher temperature & T2= Lower temperature

Here T1= 90⁰F= 32.22⁰C & T2= 20⁰F= -6.67⁰C

Theoretical COP = (-6.67 + 273) (32.22+273) – (6.67 + 273)

Theoretical COP= 6.85

Actual Powerremoval Minimum Power Required == Theoretical COP

120000 Minimum Power Required = P=17523 Btu/h 6,85

Minimum power required= 6.88 hp