Math Problem Solver

MPEN 417 REFRIGERATION AND AIR CONDITIONING DEC. 2024

Requirements: - Thermodynamic and Transport Properties of Fluids, Calculators

-Answer all questions (30 Marks)

QUESTION ONE

Saturated air at 20 °C is passed through a drier so that its final relative humidity is 20%. The drier uses silica gel adsorbent. The air is then passed through a cooler until its final temperature is 20 °C without a change in specific humidity. With the aid of psychrometric chart, calculate:

i.The temperature of air at the end of the drying process

ii.The heat rejected in kJ/kg dry air during the cooling process

iii.The relative humidity at the end of the cooling process

iv.The dew point temperature at the end of the drying process

v.The moisture removed during the drying process in kg vap. /kg dry air.

QUESTION TWO

A small-size cooling tower is designed to cool 5.0 litres of water per second, the inlet temperature of which is 450C. The motor-driven fan induces 9 m3/s of air through the tower and the power absorbed is 4.8 kW. The air entering the tower is at 200C, and has a relative humidity of 60%. The air leaving the tower can be assumed to be saturated and its temperature is 270C. Calculate:

i.The amount of cooling water (make-up) required per second.

ii.The final temperature of the water.

Assume that the pressure remains constant throughout the tower at 1.013 bar