Heat and mass transfer study of hydraulic refrigeration system and direct contact heat exchanger.

摘要

The conversion of seawater to fresh water by a freezing process has been proven feasible for many years. The practical problems that have been identified are the conventional refrigerant compressors and controlling the freezing process. The compressor problems appear to be the most difficult to resolve. The recent invention of the hydraulic refrigeration system appears to provide an excellent solution to the compressor problems and makes the freeze desalination method more feasible. An investigation was performed to evaluate the performance and efficiency of the hydraulic refrigeration system. Direct-contact heat transfer is the basic of the freezing process. Direct-contact heat transfer between two immiscible liquids has the advantage of eliminating metallic heat transfer surfaces that are prone to corrosion and fouling. The freeze chamber suggested is some variation of the vertical type of direct-contact heat exchanger. A theoretical model was performed to evaluate the performance of such a heat exchanger.;The theoretical modeling of the HRS was modified and performed to predict the performance and efficiency. The experimental results were obtained to compare with the theoretical modeling. The results showed that the addition of iron oxide to the compression loop water did not impact the HRS performance. The computer simulation predicted the experimental HRS performance equally well with or without the presence of additional iron oxide in each compression loop. The simulated refrigeration rates matched the ethylene glycol experimental data well. Although the refrigeration rates appeared to be well predicted, the comparison between simulated and ethylene glycol experimental COP showed considerable disagreement. Finally, the results showed that the computer modeling of the external condensing HRS and the experimental data also agreed well.;The theoretical modeling of the vertical type of direct-contact heat exchanger was performed to predict the performance and efficiency. A comparison between the present theoretical model and the available experimental data on refrigerant droplet evaporation showed reasonably good agreement. The present theoretical modeling was then used to predict the performance of the direct-contact heat exchange freeze chamber with confidence. The model calculation produced the final size of the ice crystal and the required diameter of the heat exchanger.