Design of plate fin heat exchanger with offset strip fins for the liquefaction of natural gases

Abstract

In the cryogenic systems such as liquefier, cryo-coolers, etc. the heat exchangers are one of the most critical components. The heat exchanger used in cryogenic applications must have high effectiveness to produce a proper refrigerating effect and it should not be less than 85%. It has already experimented that if the value of the effectiveness of the heat exchangers falls below the design value, then the no liquid will be produced. On a general basis, there are so many heat exchangers available in the industry which are used in the cryogenic works but there is a special category of the heat exchangers that are available, which are now used widely because of there because of their compactness, low weight, and high effectiveness. These heat exchangers are known as the compact heat exchangers. The objective of this work is to design a plate fin heat exchanger, which is when used in the liquefaction cycle must be able to liquefy the natural gases and to produce 1000 Kg liquid ih a day, which can be transported easily for the various purposes through various ways. This work has been carried on the plate fin heat exchanger with selecting the offset strip fin, which is the most reliable fin design in the liquefaction applications. The work includes the two cryogenic fluids, one is methane and the other is propane. Propane is used as the coolant to bring down the temperature of methane to this close that when passed through the expander or by precooling in the liquefaction cycle it gets liquefied easily. Catia software was used to model the component and Matlab programming has also been done to design a plate fin heat exchanger. As the geometry were too complex to analyse in the software because of the physical memory limitation, a small symmetric part of the heat exchanger model were imported in the analysis software called Ansys 18.1 for the validation of the results and it can be concluded from the observations that the model is capable to do the desired function. A small variation in the calculation and analysis results has been observed, and the effectiveness of the heat exchanger was found to be above 90 %. Aluminium 3003 has been used as the material for the fins strips and for separating plate.