Theoretical Analysis And Experimental Verification On Cooling Performance Of Closed Cooling Tower With Packing

China’s water resources are extremely deficient, while energy situation is also not optimistic.Aiming at the above problems, in order to complete the binding target about energy saving andemission reduction in the national economic and social development12th five-year plan outline,we must strive to develop the recycling cooling water technology and evaporative coolingtechnology. Closed cooling tower have the above two kinds of core technology, the use ofclosed-cycle can reduce the loss of cooling water and energy, at the same time, the coolingmechanism of closed cooling tower is mainly evaporation cooling, therefore, its application inmodern industry is increasingly widespread.The spray water evaporation and mass transfer process of early packless closed cooling toweris completely in coil surface. In order to achieve adequate amount of evaporation and heatexchange, the larger area coil need to be adopted. It increases the metal material usage, whichresults in higher cost, and the equipment is heavier. While the closed cooling tower with packingis a collection of advantages of open type cooling tower and non-filler closed cooling tower. Likenormal open type cooling tower by setting the large specific surface area of packing to increasearea for heat and mass transfer enhancement, it can make a lower outlet temperature of the fluidmedium in the coil; Meanwhile it can also keep medium in the coil cleanliness like non-fillerclosed colling tower, reduce the discharge capacity of spray water, obviously improve coil surfacescaling phenomena, and reduce the manufacturing, operation and maintenance costs.In this paper on the basis of the heat and mass transfer theory, through Poppe and Merkelhypothesis, the mass and energy balance of the coil section and the packing area were analysed,and the heat transfer and mass transfer mathematical model of the non-filler and closed coolingtower with packing were established. Meanwhile the closed cooling tower test platform wereconstructed, the research of the influence rule of closed cooling tower with packing material andcoil on air wet bulb temperature, air flow, cooling water flow rate, cooling water inlet temperatureand spray density was conducted to contrast with computed results.By contrasting the computing result based on two kinds of method with experiment result,the cooling performance of non-filler type and closed cooling tower with packing is of a consistenttrend under the influence of same performance parameters. For the non-filler closed cooling tower, the maximum error of cooling water outlet temperature between computing value based on Poppemethod and experimental results is only0.99%~1.9%, the maximum error of air outlet enthalpy isbetween2.2%~4.9%; the maximum error of the cooling water outlet temperature betweencomputing value on Merkel method and experimental results is1.4%~2.4%, the maximum error ofthe air outlet enthalpy can be3.7%~5.6%. For the closed cooling tower with packing, themaximum error of cooling water outlet temperature between computing value based on Poppemethod and experiment results is2.7%~3.9%, the maximum error of air outlet enthalpy is6.3%~9.2%; the maximum error of the cooling water outlet temperature between computing valueon Merkel method and experimental results is2.7%~6.3%, the maximum error of the air outletenthalpy reach to13.5%~18.1%. Thus computing value on Poppe method is more close toexperiment value than that on Merkel method. Meanwhile, the cooling water outlet temperature ofclosed cooling tower are more been concerned in the project, thus, by only contrasting the coolingwater outlet temperature between the simulation results and the experiment results, the modelcalculations of non-filler type and closed cooling tower with packing meet the engineeringaccuracy requirements based on Poppe and Merkel method. Therefore, the Merkel method canreplace the Poppe method in actual engineering calculation.By contrasting the computing value and experiment results in the same conditions, thecooling water outlet temperature of closed cooling tower with packing is respectively lower thanthat of non-filler closed cooling tower by0.7769°C~1.8068°C,0.961°C~2.5084°C and0.4°C~0.9°C; Cooling tower efficiency is respectively higher than7.47%~17.37%,6.3%~24.12%and3.85%~8.66%. Thus, in the same conditions, the cooling performance of closed cooling towerwith packing is obviously better than no filler closed cooling tower.Meanwhile, by analysising the influence of cooling water flow direction on the coolingperformance of closed cooling tower with packing, it’s shown that cooling water outlettemperature of cooling water inflow from below is lower than that of cooling water inflow fromtop by0.6007°C~1.5665°C,0.6464°C~1.8919°C and0.2°C~0.4°C, cooling tower efficiency isrespectively higher than5.79%~17.3%,6.22%~18.19%and1.92%~4.25%. Therefore, the coolingperformance of cooling water inflow from below (i.e. cooling water and air flow in parallelwith the same direction, and in opposite to the spray water) is obviously better than that ofcooling water inflow from top (i.e. cooling water and spray water flow in parallel with thesame direction, and in opposite to air).