Experimental Research On Heat Transfer Performance Of Closed Cooling Tower With Packing Material

During the12th Five-Year Plan, our country’s energy and water resources problems are faced with great challenge. In order to achieve energy-saving and emission reduction targets and water-saving society construction of the National12th Five-Year Plan, we must develop circular economy energetically and promote low-carbon technology.Compared with other traditional heat transfer equipment, closed cooling tower is a high efficient and energy-saving cooling equipment combined with water cooling type cooler and cooling tower, which belongs to the energy-saving and emission reduction product. It uses renewable energy in unsaturated air dry and wet bulb temperature difference of the natural environment,through heat and moisture exchange between the water and air to exclude the medium heat inside coil. This is the concrete practice of evaporative cooling technology, set in one of the advantages of air cooling and water cooling, heat transfer and mass transfer.Compared with traditional closed cooling tower with single coil, closed cooling tower with packing material (i.e., closed cooling tower with packing material and coil), through the secondary heat transfer of the large specific surface area packing, make outlet temperature of the fluid medium in the pipe is lower, can get the good operation effect and relative lower manufacturing cost. Also the maintenance is more convenient, spray water discharge amount is lower, and manufacture and operation cost is reduced further. In addition coil surface fouling gets clear improvement, prolonging the maintenance cycle.In this paper with closed cooling tower with packing material as the research object, on the basis of the heat and mass transfer theory, through reasonable hypothesis, 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 coil section and the packing area were established in the closed cooling tower with packing material and coil.Meanwhile through the design of closed cooling tower with packing material and the construction of closed cooling tower test platform, the performance experiment has been carried on, and the research of the influence rule of closed cooling tower with packing material and coil on air dry and wet bulb temperature, cooling water flow rate and inlet temperature, air flow and spray density was introduced. For the closed cooling tower with packing material and coil or with single coil of fixed structure, air wet bulb temperature and air flow has the most significant influence on the cooling performance, cooling water flow rate and inlet temperature has a great influence, air dry bulb temperature has only a minor influence, and the influence of spray density is essentially unchanged after it achieves the best value. Due to the addition of packing material, the best spray density of closed cooling tower with packing material and coil compared with closed cooling tower with single coil is relatively small, can be between0.025～0.035kg/(m·s). For the closed cooling tower with single coil, it is suggested that the best spray reach to0.040-0.060kg/(m·s).Through the perfonnance experimental study of the three different structural types closed cooling tower, the differences on cooling water outlet temperature, cooling capacity, spray water temperature, cooling efficiency, etc. between the three different structural types closed cooling tower were analysed in detail under the influence of air dry and wet bulb temperature, cooling water flow rate and inlet temperature, air flow and spray density. The experimental results show that the cooling performance of closed cooling tower with packing material on top and coil underneath and closed cooling tower with coil on top and packing material underneath is obviously better than closed cooling tower with single coil in7%～18.4%, and the cooling performance of closed cooling tower with packing material on top and coil underneath is slightly better than closed cooling tower with coil on top and packing material underneath in0%～4.9%.Experimental comparison analysis on perfonnance influence of cooling water parallel&counter-flow for three different structural types closed cooling tower was introduced under the action of air dry and wet bulb temperature, cooling water flow rate and inlet temperature, air flow and spray density. In the same conditions the cooling performance of closed cooling tower with packing material on top and coil underneath and closed cooling tower with coil on top and packing material underneath when cooling water parallel-flow is better than it when cooling water counter-flow in3.2%-9.6%, and the cooling performance of closed cooling tower with single coil when cooling water parallel-flow is slightly better than it when cooling water counter-flow in1.4%～4.9%.