Analysis and comparison of distribution performance of two entrance forms used in plate-fin heat exchangers

Key words:  gas-liquid two phase flow  plate-fin heat exchanger  standard deviation of flow rates  non-uniformity of distribution

Abstract:

For the traditional entrance form (form A) used in plate-fin heat exchangers, gas and liquid flows were mixed together before entering the header to be distributed. A novel form (form B) was designed, in which distribution was prior to mixing by using a gas-liquid distributor. Numerical simulation of the gas-liquid flow distribution was carried out for the two different entrance forms by computational fluid dynamics method, respectively. The non-uniformity and standard deviation of the gas-liquid flow distribution in entrances of the plate-fin heat exchanger were analyzed under different conditions of flow rate (0.078-0.291kg/s) and liquid mass fraction (7.8%-91.4%). The calculation results show that the non-uniformity of gas-liquid flow distribution is smaller for the form B than that for the form A under the same flow conditions. The non-uniformity is more serious with the increase of mass flow rate, and the non-uniformity for the form A increases even greater. For the form B, the non-uniformity of gas-liquid flow distribution slightly rises with the increase of liquid mass fraction. Conversely, it reduces for the form A. The non-uniformity of gas-liquid flow distribution for the form B remains a lower value, which is smaller than that for the form A. The way of "distribution prior to mixing" can improve the uniformity of the fluid flow distribution in plate-fin heat exchangers effectively.