Theoretical and experimental research on the performance of a refrigerant generating bubble pump with a high-accuracy semi-empirical model

Abstract

Refrigerant generating bubble pump (RGBP) is the main component of diffusion absorption heat transformer (diffusion AHT), which is of great significance for waste heat recovery and lack of theoretical and experimental investigations. In present work, a high-accuracy semi-empirical model with H2O-CaCl2-R134a of good thermal stability has been firstly proposed by introducing generation and friction coefficients, which correlated geometry and operational parameters. The performance of RGBP with five independent operational parameters was calculated by the model. Moreover, experiments with five independent operational parameters were conducted by a closed setup, to validate the availability of the semi-empirical model. In the theoretical and experimental analyses, the refrigerant flow rate was used to evaluate generating performance, while the solution flow rate and pumping ratio were used to evaluate pumping performance. The results were concluded that: (1) the mean relative errors of refrigerant and solution flow rates between experimental and theoretical results were rapidly reduced from 103.34 % and 340.66 % to 18.29 % and 5.46 % by using the semi-empirical model; (2) higher generating temperature, larger diffusion gas flow rate, smaller concentration and lower system pressure promoted refrigerant generation; (3) higher motive head and smaller diffusion gas flow rate led to the increase of the solution flow rate and pumping ratio. The investigations may partially reveal the operation mechanism of RGBP, and the semi-empirical model is useful to predict performance of RGBP and choose suitable conditions of RGBP for the diffusion AHT with better performance.