Development Of Calculation Program For Design Of Coil Wound Heat Exchangers With Phase-change

Coil wound heat exchanger is a special kind of compact heat exchanger, which belongs to shell and tube heat exchanger with a large heat transfer area in each unit volume. Nowadays it is mainly used in low temperature areas, especially in the Rectisol process. Domestic and foreign manufacturers have adopted the Rectisol Wash to remove acid gases. Typically,5to6coil wound heat exchangers are used in this process. Heat exchangers are the main components in chemical industry. In air separation units and Liquefaction of Natural Gas plants, they represent20-30%of the investment costs. In addition, their performance affects the sizing and designing of other major equipments, namely compressors and their power drivers. Therefore, reasonable choice and design of the coil wound heat exchangers are important to the energy use and the investment of factory.In order to improve the design accuracy and efficiency of the coil wound heat exchanger in Rectisol process, an user-friendly calculation program compiled by Fortran language for the design of coil wound heat exchanger with phase change was developed presently, giving full consideration of the impact of boiling and condensation heat transfer on heat transfer coefficient and pressure drop. A new heat exchanger design method called segmented design method was also proposed in the present work by taking into account of the variation of fluid properties of the hot and cold fluids with respect to the temperature. In this method, the whole heat exehanger is firstly divided into several parts. Based on the energy conservation principle, the connection conditions between each part are established. Applying the initial condition and the connection conditions leads to the inlet and outlet temperatures of each part. The application of LMTD method gives rise to the heat transfer surfaces. Thus the whole design of the heat exchanger is completed. Since the segmented design method reflects the reality of heat transfer process, it should yield a more accurate design result.The accuracy of the rating calculation is verified by comparing the original design values of El, E6and E10with the calculation results. The results show that the model of coil wound heat exchangers is basically reasonable, which may be helpful for further optimization and design of coil wound heat exchangers.