Study On Heat And Mass Transfer Characteristics Of Hollow Fiber Membrane Accumulator

Concentration difference nondestructive energy storage is an effective way to improve the adaptability of variable heat source in the refrigeration system driven by the solar energy under the conditions of contradictory problem between the relatively stable demand of refrigeration load and unstable solar energy heat source in the Lithium Bromide absorption refrigeration system and for the crystallization problem caused by the too high solution concentration in the ordinary lithium bromide concentration difference accumulator. The tentative idea of the membrane structure of the accumulator is put forward connecting with the membrane technology. The membrane was used as the accumulator skeleton, and it frames out the mass transfer channels of water vapor and Lithium Bromide solution. Water vapor will permeate through the membrane pores into the thick Lithium Bromide solution to dilute solution under the steam pressure difference on both sides of the membrane, and to release heat heating solution at the same time in order to realize the purpose of melting crystal rapidly.The mathematical model of heat and mass transfer of micro-porous fiber membrane accumulator is presented by using Matlab and Fluent softwares for simulation. The dynamic characteristics of the solution’s parameters are studied according to the calculation results, such as the membrane flux and the mass fraction and temperature of solution. The feasibility of membrane accumulator is proved at the same time. Results are as follows:The verification experiment result shows that the calculation results have good consistency with the experimental results. The maximum of the average temperature difference is 0.327%, and the largest average mass fraction difference is 3.46%, it verifies the feasibility and the reliability of the simulation results of membrane accumulator further.The membrane flux has a connection with the temperature and mass fraction of membrane surface solution. The mass fraction is greater, the membrane flux is larger at the constant temperature; the temperature is the higher, the membrane flux is the greater at the constant quality score.The temperature of the Lithium Bromide solution rises with the increasing of time after absorbing solution heat of the water vapor quickly, the temperature gradient is the largest at the membrane surface, solution temperature declines as the X axis coordinate becomes large; the change rate of temperature decreases with the X axis coordinate values increasing at different time, the solution temperature will slow down with the increasing of the Z axis coordinate values.The solution quality score will reduce quickly after water vapor through the membrane surface, the change rate of solution mass fraction on the membrane surface is the largest, the solution quality score is incremental change trend as X coordinate values; the mass fraction of solution rate decreases with the X axis coordinate values increasing at different time, and mass fraction with the increment of the Z axis coordinate values.Changing initial conditions of the calculation model, analyzing and summarizing the intensification method of heat and mass transfer process inside membrane accumulator: reducing the initial mass fraction of the solution, increasing the initial temperature of water vapor, reducing membrane tube spacing and so on. This means that this new type of membrane structure accumulator has the higher work efficiency, effect is more prominent, and it is more suitable for improving concentration difference of solution energy storage, increasing the energy storage density of accumulator for the higher the concentration of Lithium Bromide solution.