Question

An induced-draft cooling tower cools 90,000 gallons per minute of water from 84 to 68oF. Air at 14.61 psia, 70oF dry bulb and 60oF wet bulb enters the tower and leaves saturated at 80oF. Find (a) the volume flow rate of air in cubic feet per minute, and (b) the makeup water required, in lbm/hr.

Answer 1

Answer:

a. V = 109.64 × 10⁵ ft/min

b. Mw = 654519.54 kg/hr

Explanation:

Given Parameters

mass flow rate of water, Mw = 90000g/min = 6607.33 kg/s

inlet temperature of water, T1 = 84 F = 28.89 C

outlet temperature of water, T2 = 68 F = 20 C

specific heat capacity of water, c = 4.18kJ/kgK

rate of heat remover from water, Qw is given by

Qw = 6607.33[28.89 - 20] * 4.18

Qw = 245529.545kw

For air, inlet condition

DBT = 70 F              hi = 43.43 kJ/kg

WBT = 60 F             wi = 0.00874 kJ/kg

                                u1 = 0.8445 m/kg

oulet condition,

DBT = 70 F        RH = 100.1

h1 = 83.504kJ/kg

Wo = 0.222kJ/kg

check the attached file for complete solution