Outdoor conditions are 32°C DBT and 22°C WBT. Required comfort conditions are 22°C DBT and 55% RH. Quantity of outdoor air supplied is 0.5 m3/min/student. Comfort conditions are achieved first by chemically dehumidifying the air and then cooling by coil. Find:

i. DBT of air leaving dehumidifier

ii. Capacity of dehumidifier

iii. Capacity of cooling coil in tons of refrigeration

iv. Required surface temperature of cooling coil if the bypass factor of coil is 0.3

Subject:- Refrigeration and Air Conditioning

Topic:- Design of air conditioning systems

Difficulty:- Low

$t_d3=22℃,∅3=55%, t_d1=32℃, t_w1=22℃, $

$V ̇_1=0.5*60=30 \frac{m3}{min},BPF=0.3$

Capacity of cooling coil in TR

=$m ̇_1*(h_2- h_3)=34.1*(56-45.5)=358.05 \frac{kJ}{min}=\frac{358.05}{(60*3.5)}$=1.705 TR

Let required surface temperature of cooling coil be $t_d4$

BPF=0.3=$\frac{(t_d3-t_d4)}{(t_d2-t_d4 )}=\frac{(22-t_d4)}{(32-t_d4 )}$

∴$t_d4$=17.71℃