(Solved): solve in 10 min A double pipe parallel flow heat exchanger is used to heat water (Cp=4180J/kg ...

solve in 10 min

A double pipe parallel flow heat exchanger is used to heat water $$(\mathrm{Cp}=4180\mathrm{J}/\mathrm{kg}?\mathrm{K})$$ at a rate of $$0.2$$ $$\mathrm{kg}/\mathrm{s}$$ from $$28^{?}\mathrm{C}$$ to $$65^{?}\mathrm{C}$$. Geothermal water $$(\mathrm{Cp}=4310\mathrm{J}/\mathrm{kg}?\mathrm{K})$$ available at $$127^{?}\mathrm{C}$$ at a mass flow rate of $$0.3\mathrm{kg}/\mathrm{s}$$ is used for heating. The inner tube is $$0.8\mathrm{cm}$$ in diameter and has a thin wall. Determine the length of the tube required to achieve the desired heating if the overall heat transfer coefficient of the heat exchanger is $$550\mathrm{W}/{\mathrm{m}}^2.\mathrm{K}$$.