Single-Effect Thermal Vapor-Compression Desalination Process: Thermal Analysis

Abstract

A mathematical model is developed to analyze a single-effect thermal vapor-compression (TVC) desalination process. The model considers the effect of various thermodynamic losses on the system preformance ratio, the specific heat transfer area, and the specific flow rate of cooling water. The losses contemplated are the boiling-point elevation, the nonequilibrium allowance, and the temperature depression corresponding to the pressure drop in the demister and during the vapor-condensation process. The model takes into consideration the dependence of the physical properties of the seawater on temperature and salt concentration. In addition, the model considers the effects of the fouling factors and the presence of noncondensable gases on the heat transfer coefficients in the evaporator and the condenser. The system performance is analyzed in terms of parameters controlling the cost of product water, which include the performance ratio, the specific heat transfer area, and the specific flow rate of cooling water. The performance ratio is found to have values close to 2 at low boiling temperature, low compression ratio, and high pressure for the motive steam. On the other hand, the specific heat transfer area and the specific cooling-water flow rate are found to decrease at higher boiling temperatures, higher compression ratios, and lower pressures for the motive steam.