Researches On The Performances Of Bubble Pumps In The Diffusion Absorption Heat Transformer

The diffusion absorption heat transformers can improve the temperature of low-grade heat,and it has great research significance because it is driven by heat completely,without solution pumps and electric input.The system can be divided into refrigerant generation/absorption side and diffusion generation/absorption side.The operation performances of bubble pumpes on both sides are the important factor affecting COP and temperature lift performance of the system.In this paper,H₂O was used as the refrigerant and HCOOK was used as the refrigerant absorbent in the bubble pump at the refrigerant generation/absorption side,R134a was used as the diffusion gas and TEGDME was used as the diffusion gas absorber in the bubble pump at the diffusion generating/absorption side,theoretical and experimental researches were carried out.The main contents and conclusions were as follows:1)On the basis of previous studies,this paper improved the experimental rig,by cutting off the refrigerant generation/absorption side and the diffusion generation/absorption side through the valve,and carried out the experiment separately;replaced the oil-free piston compressor for the refrigerant generation/absorption side,and solved the corrosion and sealing problems by packaging the compressor in a closed cylinder;replaced the metal tube float mass flow meter for the diffusion generation/absorption side,and then the measurement accuracy of gas phase mass flow rate was improved.2)On the improved test bench of the double entrances and exits bubble pump with single lift tube,the following experimental results were obtained:with the increase of diffusion gas mass flow rate,the refrigerant mass flow rate increases;with the increase of solution concentration,the refrigerant mass flow rate,gas mass flow rate,solution mass flow rate,liquid gas ratio and generating power decrease;with the increase of moving head,the solution mass flow rate and liquid gas ratio increase significantly;with the increase of generating temperature,the refrigerant mass flow rate,gas mass flow rate and generating power increase significantly;with the increase of system pressure,the mass flow rate of refrigerant and gas mass flow rate decreases.3)The generation correction factor g_m and friction correction coefficient f_m were introduced into the model of the double entrances and exits bubble pump with single lift tube.The absolute average value of the relative error between the predicted refrigerant mass flow rate and the solution mass flow rate were taken as the fitting objective function to reduce the prediction error.The empirical formulas are fitted,and the error between the predicted refrigerant mass flow rate and the solution mass flow rate is 36.56%and 4.04%,respectively.4)On the improved test bench of the single entrance and exit bubble pump with multiple lift tubes,the following experimental results were obtained:With the increase of generating power,the gas mass flow rate increases;with the increase of solution concentration,the gas mass flow rate,solution mass flow rate and pressure difference increase,while the temperature decreases slightly;with the increase of moving head,the gas mass flow rate,solution mass flow rate,pressure and temperature increase significantly.5)The generation correction coefficient g_k and friction correction coefficient f_kwere introduced into the model of the single entrance and exit bubble pump with multiple lift tubes.The number of lift tubes was introduced into the model as a variable.Due to a pressure difference on this side,the immersion ratio formula was modified.The absolute average value of the relative error between the predicted gas mass flow rate and the solution mass flow rate was taken as the fitting objective function.The empirical formulas were fitted,and the error between the predicted gas mass flow rate and the solution mass flow rate is 6.79%and 5.38%,respectively.