Question

One application of pump systems is in cooling towers. Cooling towers reject heat from the chiller condenser to the atmosphere (act as reservoirs). Parallel condenser pumps are used in large chilled water systems to decrease operating costs and for redundancy. Use the following system to select Armstrong pumps for the cooling system. The performance curve of an individual pump is given as He = 75-0.75Q?, where head is in feet and flowrate is in cfs. Remember to leave one pump for backup. The total design flowrate is 6,000 gpm. The friction losses for the system are provided in the table below. - OPEN DISCHARGE DISTRIBUTION PAN 10 FT! S CONDENSER COOLING! TOWER! WATER LEVEL: PUMP SUCTION PAN www ww xo xo xo xo PUMPS & TRIPLE DUTY VALVES Capacity, Friction losses, gpm 6600 6000 4200 3000 1800 0 60.5 50 24.5 12.5 4.5 0

Answer 1

Hp = 75 - 0:15 92 ig in CES When pump are installed in parallel than total discharge will be summed up directly but Head wall semain constant Suppose we are ling_02- pumps Discharge ber bumb will be - co00 gpm (ht) Hp = elevation difference_+_frictional lowes ( z) Hp = loft + 50ft ( hi from table foxy = 6000 9. Pro) 7 Hp = 60ft - Now By equation D & @ =) 60 = 75 - 0.75.8? = 15 V0.75 g= 4.47 CFS = 4.47 x_448.83 = 2006:3 gpm By Fa = 000 = 2006.3 n = 2.99 3 so that at least 3 pump are requird pump for back up. Total pump=4 1 Additional (so ok).