A counterflow heat exchanger is located between a collector and a storage tank. The fluid in the collector side is a water-glycol mixture with cp = 3840 J/kg-°C and a flow rate of 1.35 kg/s, whereas the fluid in the tank side is water with a flow rate of 0.95 kg/s. If the UA of the heat exchanger is 5650 W/°C, the hot glycol enters the heat exchanger at 59°C, and the water from the tank at 39°C, estimate the heat exchange rate.
First, the capacitance rates for the collector and tank sides are required, given by Cc = (mcp)c = 1.35 X 3840 = 5184W/°C
From Eq. (5.54), the heat exchanger dimensionless capacitance rate is equal to
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