| Summary: | 碩士 === 國立臺北科技大學 === 能源與冷凍空調工程系碩士班 === 100 === In the present study, numerical investigation of mixed convection and pressure drop in a shell and double helical coiled heat exchanger is reported. Water is the working fluid and inlet temperature is fixed at 288K. Changing wall temperature (296~321K), inlet velocity (0.5~5 m/s), coil diameter (96mm, 142mm), and coil pitch (21, 31.08mm) to determined heat transfer and pressure drop inside helical tubes. In addition, shell side heat transfer and overall heat transfer coefficient are investigated with various shell side inlet temperature and velocity and fixed tube side inlet temperature and flow rate. For fixed shell side and tube side mass flow rate of 1.18, 0.95, respectively, fixed inlet temperature at 288, 333 K, respectively. Single and double helical tubes are compared. The results of the present numerical study indicate that double helical tubes yields lager greater heat exchange rate as a result of larger heat transfer surface area, although it also results in a smaller heat transfer coefficient. The tube side pressure drop is significantly decreased as a result of the split of liquid flow, while only minor influence of shell side pressure drop is found. The helical tube pressure drop increases with decreasing curvature radius, and increasing fluid velocity. This study was asked the empirical formula of the coefficient of friction within the coil, and the tube and shell side heat transfer empirical formula. Based on the results of numerical simulation for various parameters, empirical correlations of pressure drop and heat transfer of both tube side and shell side of a shell and double coil heat exchanger are proposed.
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