Study On Evaporative Cooling Energy Saving Technology Used In Ventilating And Air Conditioning Equipment

Evaporative cooling systems are finding increasing application in northwest area of China since the 1990s, which are applied to replace with traditional mechanical refrigerator. Since 2002, cell-unit direct evaporative cooling air conditioners are widely used in Guangdong province, which served as ventilating and cooling down equipment in big industry building.Today, energy crisis is approaching and threatening mankind's survival.There are a large numbers of big industry buildings in our country. The temperature in industry building is usually rather high and some production process brings poisonous and noxious matter. With the establishment of some standards such as GBZ1—2002, the method of nature ventilating and cooling down in industry buildings can not meet the demand, moreover, traditional mechanical refrigeration will bring higher investment, operation expense and poor air quality. However, evaporative cooling equipment (air conditioner) has it's superiority, it can bring better effect than that of nature ventilating equipment and traditional mechanical refrigerator.On the other hand, with fast economic growth, many skyscrapers have appeared in big cities of China. Lighting, heating, and air conditioning strain energy supplies, to the extent that skyscrapers become lavish consumers, and wasters, of electric power. Worse of all, those reflective glass coated with silver or gold mirror films raise the temperature of the surrounding air. In this condition, the superiority of evaporative cooling equipment combining with traditional mechanical refrigerator is becoming important.For above reasons, a lot of theoretical and experimental research on heat and mass transfer phenomenon of evaporative cooling process in pads is carried out here. The main work is as follows:1. On the basis of analyzing previous models, this paper presents a two-dimension nondimensional mathematical model, which can describe all types of evaporative cooling pads. The mathematical model is described with three partial differential equations. As soon as the product of (α_aA) is obtained, the mathematical model can be calculated. Computed numerical results tally with experimental results.2. A back-propagation neural network is created, is trained with part of experimental data, and the trained neural network is verified with another part of experimental data. Result shows that the neural network can well predict the performance of the equipment under various working condition. Secondly, since the effect of momentum source is taken into account, the boundary layer theory mathematical model is more accuracy.3. An experimental apparatus of evaporative cooling pads is set up to check the reliability of theoretical model and to have a deep understanding of heat and mass transfer of practical evaporative cooling process. We have experimentally examined the effects of input air temperature, input air relative humidity, air velocity, circulating water temperature, static pressure drop across pad, and pad thickness on evaporative cooling performance. The experimental results show that higher efficiencies are obtained with slower air velocities, and thicker pads, however, slower air velocities result in smaller air flow, and thicker pads result in higher pressure drop across pad. Experimental results also show the cooling efficiency mainly has relation with air velocities and pad. Maintaining the evaporative cooling pad saturation by maintaining enough water flow, we should pay attention to the distribution of water flow across the pad. These conclusions tally with the numerical results.4. Practical application conditions of cell-unit evaporative cooling equipment in arid and humid area of China are introduced. The performance analysis results show that evaporative cooling equipment is an energy saving, environment protection, economical equipment, and can be used as ventilating and air conditioning equipment in industry workshop of humid area.5. Optimized measures are brought forward to improve the performance of evaporative cooling equipment and evaporative cooling systems.The above study provides the design and application of evaporative cooling air conditioner with some theoretical basis and foundation.