Question

Q2/ In one of applications, wanted to condition laboratory at inside design condition DBT-24 °C and 50% Rh and outside design condition DBT-44 °C and WBT-27 °C. Total sensible load for the space is 35 kW and total latent load for the space is 19 kW. Rate of supplied air to the space is 11050 m'/hr and rate of outside ventilation air is 4250 m/hr. The recireulated air is mixing with the outside air and then entering to cooling coil and leaving at 95% Rh then the air is passing through heating coil before supply to the space. Determine: 1.Condition of supply air to the conditioned space (DBT & RH): 2.Condition of air before and after cooling coil (DBT & RH); 3. Sensible load of heating coil; 4.Sensible load and latent load and total load of cooling coil: 5. Apparatus dew point (ADP) for the cooling coil; 6. Draw the cycle on the psychrometric chart.

Answer 1

From the given dry bulb temperature and relative humidity, the absolute humidity inside the space is calculated. Using the given sensible load and the latent load, the condition of supply air is evaluated. The condition of the air before the cooling coil is obtained by mixing the recirculated air with the outside air. Once dry bulb temperature after mixing is obtained, the properties such as relative humidity and absolute humidity can also be obtained. The absolute humidity will remain same across the cooling coil. The condition of the air after the cooling coil can be obtained. Further, the sensible load of cooling coil and the heating coil can be obtained as the dry bulb temperature after each process is known. The cycle is represented on the psychometric chart.