Investigation of the Flow Distribution for Supercritical Carbon Dioxide Fluid in a Plate Heat Exchanger
The present study proposes a plate heat exchanger model that is capable of simulating the supercritical fluids like CO2. The plate heat exchanger is of U-type configuration, and the size of the plate is 600 mm wide and 218 mm in height. Simulations are carried out for both isothermal and non-isothermal cases with water-to-water and water-to-CO2 plate heat exchanger. The proposed model was first compared with some existing water-to-water plate heat exchanger data. Generally, the predicted water flow distributions are in line with the experimental data. Yet the simulation results of temperature distribution alongside the plate agree excellently with other predicted model. For the plate heat exchanger in the water side, it is found that a detectable mal-distribution and the flowrate shows a consistent decline from the first to last plate. Basically, larger mal-distribution is seen when the inlet flowrate is increased or when the plate number is increased. The simulation indicates that the inlet temperature of water casts negligible influence on the water flowrate distribution. This is because the density variation for water is quite small with the temperature. By contrast, it is found that the inlet temperature difference for the CO2 side may raise significant changes of thermodynamics and transport property of CO2, and result in a great difference in flow distribution. Generally the mal-distribution of the CO2 is much less severe due to more even pressure difference between the intake and exhaust manifold. The effect of pressure on heating capacity for the water-CO2 plate heat exchanger also depends on the ratio of heat capacity flow.