Simulation and Optimization of the Fluid Solidification Process in Brazed Plate Heat Exchangers

When a brazed plate heat exchanger is used as an evaporator,the working mass in the channel may undergo soli-dification,thereby hindering the refrigeration cycle.In this study the liquid solidification process and its optimi-zation in a brazed plate heat exchanger are investigated numerically for different inlet velocities;moreover,different levels of corrugation are considered.The results indicate that solidificationfirst occurs around the con-tacts,followed by the area behind the contacts.It is also shown that deadflow zones exist in the sharp areas and such areas are prone to liquid solidification.After optimization,the solidification area attains its smallest value when a corrugation spacingλ=4.2 mm is considered.

Comprehensive comparison of small-scale natural gas liquefaction processes using brazed plate heat exchangers

The brazed plate heat exchanger(BPHE)has some advantages over the plate-fin heat exchanger(PFHE)when used in natural gas liquefaction processes,such as the convenient installation and transportation,as well as the high tolerance of carbon dioxide(CO2)impurities.However,the BPHEs with only two channels cannot be applied directly in the conventional liquefaction processes which are designed for multi-stream heat exchangers.Therefore,the liquefaction processes using BPHEs are different from the conventional PFHE processes.In this paper,four different liquefaction processes using BPHEs are optimized and comprehensively compared under respective optimal conditions.The processes are compared with respect to energy consumption,economic performance,and robustness.The genetic algorithm(GA)is applied as the optimization method and the total revenue requirement(TRR)method is adopted in the economic analysis.The results show that the modified single mixed refrigerant(MSMR)process with part of the refrigerant flowing back to the compressor at low temperatures has the lowest specific energy consumption but the worst robustness of the four processes.The MSMR with fully utilization of cold capacity of the refrigerant shows a satisfying robustness and the best economic performance.The research in this paper is helpful for the application of BPHEs in natural gas liquefaction processes.