Study Of The Temperature Distribution Model And Designing Method For Efficient Shell-and-Tube Heat Exchangers

For heat exchangers in the process industry, the physical properties of fluids often vary depending on the changing temperature. Especially in the condensing process, the temperature, vapour-liquid compositions and vapour fractions of fluids might change, which would result in different flow patterns from inlet to outlet of the condenser. When designing and rating a heat exchanger, therefore, it is critical to accurately predict and simulate the static temperature field of the heat exchanger.The present study mainly focused on both the single phase and condensing temperature distributions of heat exchangers with multi-tubesides and different flow arrangement. The single phase temperature model was established based on the differential theory. In terms of the baffle numbers(Nb) and tube passes(n), a heat exchanger was divided into (Nb+1) cells and then (Nb+1)n small sub-cells. The fluid in tubeside flows through the sub-cells in sequence, while the fluid in shellside flows through the cells in parallel. Assuming the condensing curve had been acquired, the condensing temperature model was established by deducing the coolant temperature distribution in graphical method, according to the proportional relationship between the temperature and heat load in the condensing side. Based on the above temperature model, a novel method of designing heat exchanger margin was studied by computing the local and total Effective Mean Temperature Difference(EMTD). Two cases of BEU and AES heat exchangers were analyzed to demonstrate the application and accuracy of the single phase model in temperature distribution prediction compared with the Cell model and HTRI method. A condenser was simulated by the present condensing model. The availability of the model was proved in comparison with the HTRI method.