Question

A heat recovery unit in a factory uses a shell-in-tube counter flow type unit to recover heat from a flow of hot fluid to preheat water for the factory. The hot fluid enters at 88°C and a flow rate of 25 kg/minute, and exits at 55°C. The cold water will enter the heat exchanger at 15°C and exit at 55°C. Take cHot-fluid = 3000 J/kg.K, cwater = 4200 J/kg.K.

**PART (b)**

An air to water heat exchanger with an effectiveness of 80% uses water at 20°C to cool exhaust gas from 350°C. Flow of exhaust gas is 1.9 kg/s (c = 1000 J/kg.K) and the water flow is 3 kg/s (c = 4200 J/kg.K). There is no phase change of the water.

Determine the **hot exit** **temperatures
(°C)**.

Answer #1

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