SHEET (4)
AIR CONDITIONING PROCESSES
1-Ten grams of moisture per kg of dry air is removed from atmospheric air when it passed
through an air-conditioning system and its temperature becomes 30C. the atmospheric
conditions are 40C DBT and 60%R.H. Find the following for air leaving the equipment :
a- Relative humidity.
b- Wet-bulb temperature.
c- Dew-point temperature.
2-A cooling coil is used to cool 3600kg/hr of air initially at 32C DBT and 40%RH. Find the
cooling capacity of the coil in ton-ref, if the final DBT is
a-13C
b-21C
3-The atmospheric air at 30C DBT and 40% R.H is cooled to 15C DBT. Calculate the heat
removed if the supply of air is 150m3/min.
4- The conditions of atmospheric air are 40C DBT and 60%RH. The air is cooled to 20C DBT
if the air supply to system is 200m3/min, find:
a- Heat removed from the air per minute.
b- Relative humidity and wet-bulb-temperature.
5- One kg of air at 20C DBT and 80%RH is mixed with two kg of air at 30C DBT and 10C
dew point temperature. the mixture of air then passed through cooling coil with a rate of 200
m3/min.the temperature of air coming out of the cooling coil is15C DBT. Calculate the
following:
a- DBT and specific humidity of air after mixing.
b- Cooling load on the cooling coil in tons of refrigeration.
6- Air at 27C DBT and 60%RH is cooled and dehumidified by a direct expansion cooling coil
till a temperature 16C DBT. The air flow rate is 1000m3/hr. Find the cooling capacity in
tons-ref, coil SHF, coil dew point, by-pass factor and amount of condensate.
7- A chilled water spray system is used to cool and dehumidifying 11400 kg/hr of air from
30CDBT and 21WBT to 13DBT.determine the cooling capacity in ton-ref, apparatus SHF
and apparatus dew point.
8- Air at 27c DBT and 16c WBT is humidified partially to 90%rh with adiabatic air washer.
Estimate the amount of water required for humidification process in lit/min and humidifying
efficiency. If the air flow rate is 10000m 3/hr.
1
9- Air at 25CDBT and 30%RH is humidified by steam humidifier to 50%RH. Estimate the
humidifier capacity in kg/hr and heating capacity required to generate steam in KW. If the
air flow rate is 1200 m3/hr.
10- The air at 40C DBT and 35%RH is passed through adiabatic humidifier and it comes out
with 26.4C DBT and fully saturated. Find the quantity of water vapor added per kg of dry
air . Assume air pressure 101.3kpa.
11-1000m3 of air per minute at 24C DBT and 40% RH is supplied to auditorium. The condition
of atmospheric air is 33C DBT and 60% RH. The required condition is achieved first by
cooling and dehumidification and then heating. Find the cooling capacity required in tons of
refrigeration and heating capacity required in KW.
12-The atmospheric air at 40C DBT and 60%RH and at pressure 1.013bar is passed with a
rate of 30m3/min through air-conditioning system and cooled down to 15C DBT. This
cooled air is further passed through a water heater and heated to 24C. Find the final RH
and quantity of water vapor removed per hour.
If the temperature of water inlet and outlet through the water heating coil are 30C and 25C
.find the amount of water circulation in kg per minute through the heating coil.
13-Atmospheric air at 12C and 75% RH is to be conditioned to a temperature of 22C and
60% RH. The amount of air supplied is 200m3/min.
The required condition is achieved first by heating then by adiabatic humidifying .find the
following:
a- Amount of steam required in kg/h through the heating coil at pressure 2bar and 0.96
dry. Assume only latent heat of steam is used for heating.
b- The quantity of water required per hour in the humidifier.
14-Atomspheric air at 38C and 20%RH. brought to a temperature of 22C and 60%RH. First
by adiabatic humidification and then by cooling.
If the quantity of free air flow is 500m3/min, then find the following:
a- Capacity of the humidifier.
b- Capacity of the cooling coil in tons of refrigeration.
If the required conditions is achieved first by injecting the saturated steam at 100C, then
find the quantity of steam required per hour and change in capacity of the cooling coil.
15-Air at 26C and 40%RH is required for some industrial purposes when atmospheric
conditions are 42C DBT and 29C WBT. The quantity of air required is 500m3/min. The
required condition is achieved first by cooling and dehumidification and then by heating. If
the dew point of the cooling coil is 10C then fined the following:
a- cooling coil capacity in tons of refrigeration and its bypass factor
b-the quantity of steam required per hour at 2 bar and saturated which is used in
the heating coil. Assume only latent heat is used for heating.
2
16- a cold dry air at 10C and 60%RH is required for industrial process, when the ambient
conditions 41C DBT and 25C WBT. The required conditions are achieved first by
cooling and dehumidification and then by chemical dehumidification and lastly by cooling.
The dew point temperature of the cooling coil is 5C and bypass factor is 0.11. If the
quantity of air supplied is 200m3/min, find the capacities of different equipments used.
17-saturated air at 5C is first preheated and then saturated adiabatically and reheated to a
final condition of 40C DBT and 30%RH.To what temperature must the air, initially, to be
heated in the preheating coil.
3