(Solved): 22-38 A double-pipe parallel-flow heat exchanger is used to heat cold tap water with hot water. ...

22-38 A double-pipe parallel-flow heat exchanger is used to heat cold tap water with hot water. Hot water $\left(c_p=4.25\mathrm{kJ}/\mathrm{kg}?\mathrm{K}\right)$ enters the tube at $85^{?}\mathrm{C}$ at a rate of $1.4\mathrm{kg}/\mathrm{s}$ and leaves at $50^{?}\mathrm{C}$. The heat exchanger is not well insulated, and it is estimated that 3 percent of the heat given up by the hot fluid is lost from the heat exchanger. If the overall heat transfer coefficient and the surface area of the heat exchanger are $1150\mathrm{W}/{\mathrm{m}}^2?\mathrm{K}$ and $4{\mathrm{m}}^2$, respectively, determine the rate of heat transfer to the cold water and the log mean temperature difference for this heat exchanger.