Improving the Performance of a Thermal Compressor in a Steam Evaporator via CFD Analysis

Ejectors have been widely used in many applications such as water desalination, steam turbine power generation, refrigeration systems, and chemical plants. The advantage of an ejector system lies in its extremely reliable and stable operation due to the complete absence of moving parts. However, the performance depends on a number of factors, among which the flow channel configuration/arrangement is very critical. A comprehensive study mainly focusing on the sensitivity of performance on the geometric arrangement was conducted in this paper to improve an existing thermal compressor performance in a steam evaporator. The performance is measured by the suction (secondary) flow rate of the primary steam jet from a low-pressure vapor plenum. Numerical simulation is employed to investigate the thermalflow behavior. It is observed that any downstream resistance will seriously impede the suction flow rate. In addition, the suction rate is found to be sensitive to the location of the jet exit, and there is an optimum location where the jet should be issued. A well-contoured diffuser can increase the suction rate significantly. However, the size of suction opening to the plenum is less important, and a contoured annular passage to guide the entrained flow shows little effect on the overall performance. Based on the numerical results the steam suction rate of the best case in the confinement of the current study is approximately 430% the jet flow rate, while some cases with mediocre design can only produce an entrainment of 24% the jet flow.