Research And Analysis On Heat Transfer Performance Of Closed-type Heat Source Tower Under The Frost Prevention Condition

For the special climate conditions in south area of China in winter, such as rainy, cold, damp, high humidity air, the traditional air-cooled heat pump is frosting severely in winter and the use of fossil fuels for auxiliary heating is not sanitary and environmental pollution. Therefore, a new type of technology of heat source tower heat pump is developed. In winter, the freezing point of the solution is lower than 0℃.This kind of solution can be utilized to efficiently extract the low grade heat energy from the high relative humidity air in low temperature environment, so as to meet the heating demand by achieving the transfer of energy from high temperature heat energy to low temperature heat energy. In summer, it is used as a highly efficient cooling tower. The heat is released to the air for achieving refrigeration by evaporation and cooling of water.Taking the closed-type heat source tower as the research object, the article adopts the method of combining experimental research and numerical simulation. Under working condition of frost prevention, the article researches system of analysis theory of heat and mass, heat transfer performance, the systematic energy efficiency ratio, the liquid-gas ratio optimal value is investigated. The main work is as follows:1. This article introduces the concept and classification of the closed-type heat source tower and its structure and working principle. As a new type of cold and heat source, the closed-type heat source tower has better adaptability and stability in hot-summer and cold-winter area.2. The heat and mass transfer process of the coil of finned coil region of the closed-type heat source tower is analyzed under working condition of frost prevention. In order to establish the mathematical model of finned coil region of the closed-type heat source tower, the mass and energy balance equation of heat and mass transfer process of the coil of finned coil region of the closed-type heat source tower under working condition of frost prevention are built by through reasonable hypothesis. An d through analyzing and solving the model, outlet temperature of the solution, the distribution functions of outlet temperature of the solution in the coil, outlet temperature of the spray solution and the air outlet enthalpy under working condition of frost prevention have gotten.3. Through the experimental test and numerical simulation, the effect of the air temperature and relative humidity, the solution in the coil, air volume on heat absorption of the closed-type heat source tower and the energy effic iency ratio of this system. The heat absorption of the closed-type heat source tower and the energy efficiency ratio of this system increase with the increasing of air temperature, relative humidity. The best energy efficiency ratio of this system should b e considered in the solution flow rate in the coil and air volume. The effective use of latent heat can increase the total heat absorption, but the latent heat is generally not more than 35% of the total heat absorption4. By changing the liquid-gas ratio of the closed-type heat source tower, heat absorption capacity of the solution in the coil is compared and analyzed under different conditions of air temperature and relative humidity. It is concluded that the best liquid-gas ratio of this closed-type heat source tower range between 0.2~0.32.5. For the existing problem of the heat source tower such as the inconvenience of drainage, liquid collection and the condition transformation, to optimize the structure and operation of the spray system.