A chiller plant with a capacity of 1.200 tons and designed to operate with water
ID: 1843768 • Letter: A
Question
A chiller plant with a capacity of 1.200 tons and designed to operate with water supplied at 42 F and returned at 65 F, uses two chillers with equal capacity and two equal size pumps operating at 3, 500 rpm Design constant and variable flow systems, and determine satisfactory operating conditions: flow rate, bypass flow, pump speeds when the system is operating at full load, under a load of 900 tons, 60 percent of full capacity, and 25 percent of full capacity Under partial load conditions the chiller flow rates may be reduced a maximum of 30 percent of full flow.Explanation / Answer
Given: L = 1200 tons, T1 = 65 F, T2 = 42 F, N = 3500 rpm
specific gravity of water (S) = 1
specific heat of water (C) = 1.005 BTU/lb-F
a) flow rate = Q =0.5* L*15000/(500*S*C*(T1-T2)) = 778.715 GPM
From pump performance curve, pump head (H) corresponding to Q = 240 ft
pump seed = NQ1/2/(H3/4) = 1601.77 rpm
b) flow rate = Q =0.5* L*15000/(500*S*C*(T1-T2)) = 584.04 GPM
From pump performance curve, pump head (H) corresponding to Q = 249 ft
pump seed = NQ1/2/(H3/4) = 1349.397 rpm
c) flow rate = Q =0.5* L*15000/(500*S*C*(T1-T2)) = 467.23 GPM
From pump performance curve, pump head (H) corresponding to Q = 250 ft
pump seed = NQ1/2/(H3/4) = 1203.32 rpm
d) flow rate = Q =0.5* L*15000/(500*S*C*(T1-T2)) = 194.68 GPM
From pump performance curve, pump head (H) corresponding to Q = 250 ft
pump seed = NQ1/2/(H3/4) = 775.898 rpm
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