In a nutritional products plant, a plate heat exchanger cools infant formula by approximately \(25{ }^{\circ} \mathrm{C}\) from an inlet temperature of \(68{ }^{\circ} \mathrm{C}\) as it flows through the plates shown in Fig. P7.71. The process engineer would like to be able to cool the infant formula by as much as \(35^{\circ} \mathrm{C}\) as it passes through the plates. The plate heat exchanger is currently in use, so he would like to build a \(\frac{1}{2}\)-scale model for testing purposes. In the model, water will be used instead of infant formula. What flow rate is needed in the model?

Figure P7.71

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1.4 m 30% glycol solution D= 0.05 m Infant formula p = 1036.6 kg/m =1.7 x 103 N-s/m Q = 16.8 m/hr at average formula temperature