The Research Of Heat And Mass Transfer On Heat Recovery Of Mine Exhaust Air

Mine exhaust air contains abundantly residual heat that can utilize the coupledsystems, which consist of Mine Exhaust Air Heat Recovery System (MEAHRS) andWater Source Heat Pump system, to extract the useful energy source. Considering themajor problems of the Heat and Mass Transfer Unit (HMTU) and analyzingsimultaneous heat and mass transfer of the air-water two phase flow, this paper hasproposed an approach to evaluate its performance, a method to maximize heat transferoutput and a way to design its structure. This research can provide theoretical andexperimental foundations for heat and mass transfer.The traditional double-efficiency method to evaluate the performance of theHMTU in terms of the informed assessment index for diffusion tower and spray airwashers is inadequate, therefore an evaluation index which is applicable to heat andmass transfer inside HMTU between the moist air which the relative humidity is near90%and water is present and another expression of heat exchange efficiencycorrelation is developed for specific HMTU design.On the basis of the force balance on water droplet, the motion theory of waterdroplet inside counterflow and upstream-spray HMTU is explicitly derived, Therequirement about how to avoid water loss by drift and water droplets suspension isproposed and the water’s initial conditions which influenced the droplets’ trajectory isanalyzed, and the calculation approach of the distance between the drift eliminatorsand the nozzle of the upstream spray is represent. At specified conditions, increasedthe air inlet velocity can prolong the water droplets’ heat exchange time.Combining the equation of water droplet motion, heat and mass transfer and theexergy and entransy analysis models of moist air and water, after solving the equationby numerical method and researching the influence factor and driven power of heatand mass transfer inside HMTU, the optimum process of heat and mass transfer whichcan reduce the irreversibility is developed.Utilize CFD software to reform the physical model of the UMTU in terms of theabove theoretical foundations and to design a UMTU which its interior flow field is more suitable.Summarizing the research outcomes, a design approach which is reliable forcounterflow HMTU on MEAHRS is recommended, and this also can support todesign engineering application.