Chapter 11, Problem 50P

Consider the flow of engine oil $\left(c_p=2048\text{J/kg}\cdot \text{K}\right)$ and through a thin-walled copper tube at a rate of 0.3 kg/s. The engine oil that enters the copper tube at an inlet temperature of $\text{8}0°\text{C}$ and is to be cooled by cold water $\left(c_p=4180\text{J/kg}\cdot \text{K}\right)$ and flowing at a temperature of $\text{2}0°\text{C}$. We wish to have the exit temperature of the engine oil not exceed $\text{4}0°\text{C}$. The individual convective heat transfer coefficients on oil and water sides are $750{\text{W/m}}^{\text{2}}\cdot \text{K}\text{and}\text{350}{\text{W/m}}^{\text{2}}\cdot \text{K}$, respectively. If a thermocouple probe installed on the downstream side of the cooling water measures a temperature of $\text{32}°\text{C}$, for a double-pipe parallel-flow heat exchanger determine (a) the mass flow rate of the cooling water, (b) the log mean temperature difference, and (c) the area of the heat exchanger.