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A hot gas stream at 150C is to be cooled to 60C by exchanging it against a 20kg/s stream of cooling water available at 10C. The exchanger contains 240 steel tubes, 21 mm i.d., 23mm o.d. and 4.6m long arranged in a single pass. Each tube has attached to its external surface 24 longitudinal steel fins, 1mm thick with a radial length of 12mm. The water flow in the tubes is sufficient to give an internal heat transfer coefficient of 4000W/m2K. The heat transfer coefficient on the gas side is estimated to be 60W/m2K for all exposed extemal surfaces. (i) Show that heat exchange between the gas and the water is controlled by conditions on the gas side of the exchanger. Hence, estimate the overall heat transfer coefficient for the exchanger. [30%] (ii) Show that the maximum gas flowrate that can be processed in this heat exchange system is 30kg/s approximately. [50%] The efficiency, , of a fin of rectangular cross-section is given by =mLtanhmLwherem=kAhC h is the gas-side heat transfer coefficient, k is the thermal conductivity of the fin material and L,C, and A are respectively the radial length, perimeter, and cross-section of the fin. A hot gas stream at 150C is to be cooled to 60C by exchanging it against a 20kg/s stream of cooling water available at 10C. The exchanger contains 240 steel tubes, 21 mm i.d., 23mm o.d. and 4.6m long arranged in a single pass. Each tube has attached to its external surface 24 longitudinal steel fins, 1mm thick with a radial length of 12mm. The water flow in the tubes is sufficient to give an internal heat transfer coefficient of 4000W/m2K. The heat transfer coefficient on the gas side is estimated to be 60W/m2K for all exposed extemal surfaces. (i) Show that heat exchange between the gas and the water is controlled by conditions on the gas side of the exchanger. Hence, estimate the overall heat transfer coefficient for the exchanger. [30%] (ii) Show that the maximum gas flowrate that can be processed in this heat exchange system is 30kg/s approximately. [50%] The efficiency, , of a fin of rectangular cross-section is given by =mLtanhmLwherem=kAhC h is the gas-side heat transfer coefficient, k is the thermal conductivity of the fin material and L,C, and A are respectively the radial length, perimeter, and cross-section of the fin