In an attempt to reduce cost, a solar designer has proposed replacing the shell-and-tube heat exchanger in
Question:
In an attempt to reduce cost, a solar designer has proposed replacing the shell-and-tube heat exchanger in Figure 7.27 with a tube coil immersed in the storage tank. The shelland-tube heat exchanger originally specified had a surface area of \(10 \mathrm{~m}^{2}\) and a \(U\) value of \(2000 \mathrm{~W} / \mathrm{m}^{2} \mathrm{~K}\) to be used with a \(100 \mathrm{~m}^{2}\) solar collector. Using Equation 7.66 to estimate the \(U\) value of the submerged coil, how much length of \(0.5 \mathrm{in} .(1.27 \mathrm{~cm})\) diameter copper pipe would be needed to achieve the same value of \(U A\) product as the shell-and-tube heat exchanger? What percentage of the storage tank volume would be consumed by this coil if \(50 \mathrm{~kg}\) of water is used per square meter of collector? Use a storage water temperature of \(60^{\circ} \mathrm{C}\) and a collector water outlet temperature of \(70^{\circ} \mathrm{C}\) for the calculations.
Figure 7.27
Equation 7.66
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