Chapter 1 Basics of Heat Transfer1-124 Water is heated from 16°C to 43°C by an electric resistance heater placed in the water pipe as it flows through a showerhead steadily at a rate of 10 L/min. The electric power input to the heater, and the money that will be saved during a 10-min shower by installing a heat exchanger with an effectiveness of 0.50 are to be determined. Assumptions1This is a steady-flow process since there is no change with time at any point within the system and thus ΔΔmECVCVand ==00,. 2 Water is an incompressible substance with constant specific heats.3 The kinetic and potential energy changes are negligible, ΔΔkepe≅≅0.4 Heat losses from the pipe are negligible.PropertiesThe density and specific heat of water at room temperature are ρ= 1 kg/L and C= 4.18 kJ/kg·°C (Table A-9). AnalysisWe take the pipe as the system. This is a control volumesince mass crosses the system boundary during the process. We observe that there is only one inlet and one exit and thus mm. Then the energy balance for this steady-flow system can be expressed in the rate form as &
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