Performance Simulation And Optimization Analysis Of Falling-Film Evaporator With Horizontal Tube Bundle

In air-conditioning and refrigeration applications, the falling-film evaporator possesses the following clear advantages over flooded evaporator: high heat transfer coefficient and low refrigerant charge, however, this kind of evaporator is not widely used. In part, reticence to adopt falling-film technology in these systems is due to difficulties in liquid distribution design. Furthermore, decades of experience with flooded evaporators in this industry has allowed for their heuristic optimization, but heat transfer surface, bundle geometry, and operating strategies have not been so refined for falling-film evaporators. Therefore it will be very important to come up with some theory to conduct the designing and operating of falling-film evaporator by analyzing its performance optimizingly.In this paper, a distributed model is developed for predicting the heat transfer performance of a falling-film evaporator with horizontal tube bundle. In the model, the variation of heat transfer performance along tube side fluid flow direction, tube array vertical and horizontal direction, as well as the effect of dry patch on the performance are considered. Here adopt Roques'correlations based on experimental data to solve heat transfer coefficients of falling-film on horizontal tube surfaces.The model is applied to predict the performances of two commercial horizontal tube falling-film sample evaporators, pass layouts of which are horizontal and vertical respectively. The simulation result agrees well with the experimental data. Moreover, the influences of tube kind, tube bundle layout, refrigerant mass flow rate, pass layout and the flooded level of refrigerant on the evaporators'performances are studied. At last give some measures which may optimize this kind of evaporators'performance.Here refer to the above optimized measures and information of shell-tube heat exchanger design, develop a special initial software for designing horizontal tube falling-film evaporator. Proved the software practicability and optimized function by comparing the operating result with the above vertical pass layout commercial evaporator. And this also verified the practicability of the above given optimized measures which supply theory basis for designing.