Theoretical and experimental study on the lifting performance of bubble pump with variable cross-section lift tube

Abstract

Albert Einstein invented a refrigeration cycle more than eight decades ago. However, the key component (bubble pump) in this cycle has not been well investigated. In order to solve the problems existing in the simple structure, which are low efficiency and poor working stability, a bubble pump with variable cross-section lift tube (BPVC) was proposed and the generator outlet was modified in this paper. A theoretical model for the bubble pump was established. The bubble pump's working characteristics were analyzed in adiabatic slug flow pattern. The theoretical results were compared with the experimental results. In addition, the lifting performance of BPVC was experimentally compared with that of bubble pump with uniform cross-section lift tube (BPUC). The results showed that the experimental values were in reasonable agreement with the theoretical values when the submergence ratio was less than 0.3 and the gas flow rate was 0.05–0.15 g/s. However, beyond this range, the differences between experimental and theoretical values increased, due to the transition of flow pattern. The lifting efficiency of BPVC was 12.8 percent higher than that of BPUC when the heating power was 250–350 W. These results demonstrate that the application of upright tube with variable cross-section and the modified generator outlet are beneficial to improve the working performance of the bubble pump, and show the possibilities of the bubble pump to be driven by low-grade thermal energy. The study achievements provide theoretical guidance for the optimal design and performance enhancement of the bubble pump.