Experimental Study Of Water Conservation Performance Of Mechanical Draft Counter Flow Saltwater Cooling Tower

In consideration of the high heat transfer performance of the wet cooling tower, utilization of salt water as the circulating cooling medium on a prototype mechanical-draft counter flow cooling tower in order to suppress the evaporation loss, reduce the circulation cooling water consumption of power plant and maintain stable operation of cooling tower has been proposed in this paper.Sufficient data on heat and mass transfer of saltwater cooling tower under different salinity has been obtained by this experiment, and four variable models have been adopted to analyze these data. Firstly, in order to improve the precision of the calculation, physical properties of saltwater and moist under different mass fractions and temperatures have been detailed calculated. Secondly, according to the characteristic of saltwater cooling tower, the coefficients of heat and mass transfer and nondimensional parameters Re、Nuy、Shy have been defined. The experiments were performed on a prototype mechanical-draft counter flow cooling tower at different salinity (calcium chloride aqueous solution of6,12,16,25,34wt.%), circulating water mass flow (3.1～4.7kg/s) and air mass flow (1～5.8kg/s) under the different inlet saltwater temperature of28to50℃. Results mainly focus on the following aspects:The average values of NuyPr-1/3and ShvSc-1/3, which change with the saltwater mass fractions but have nothing to do with Re number, decrease by a maximum of51.5%and increase by a maximum of45.8%respectively when the mass fraction increased from6%to34%. The results can be proposed two experimental correlations.It has been discussed that the influence of inlet water temperature, gas-water ratio, inlet air dry bulb temperature, inlet air humidity, salt water salinity to heat rejection, evaporation and evaporation per unit heat rejection of cooling tower. The heat and mass transfer coefficient are calculated based on the experimental correlations mentioned above, and then the heat rejection and evaporation of the cooling tower are calculated. The evaporation per unit heat rejection has been adopted to measure the effect of cooling tower water conservation. Meanwhile, these parameters are compared with the measured value.Finally, the evaporation per unit heat rejection of power plant has been calculated at different salinity by the actual working of the2×300MW units conditions. The results indicate that the evaporation per unit heat rejection decreases40.2%when the mass fractions increased from6%to34%. The power plant can save water by a maximum of2.51million tons, and its economic benefit is1.51million Chinese Yuan. Nevertheless, packing volume of cooling tower will increase450%. It’s a promising water conservation method to apply saltwater cooling tower to the power plant.