Consider a water-to-water counter-flow heat exchanger
with these specifications. Hot water enters at 95ºC
while cold water enters at 20ºC. The exit temperature of hot
water is 15ºC greater than that of cold water, and the mass flow
rate of hot water is 50 percent greater than that of cold water.
The product of heat transfer surface area and the overall heat
transfer coefficient is 1400 W/m2 · ºC. Taking the specific heat
of both cold and hot water to be Cp 4180 J/kg · ºC, determine
(a) the outlet temperature of the cold water, (b) the effectiveness
of the heat exchanger, (c) the mass flow rate of the cold
water, and (d) the heat transfer rate.