Studies On Load Features Of Air Conditioning System And Novel Central Air Conditioning System In Cigarette Factory

Tobacco industry is an important sector of national economy in China because of its scale and output. The energy consumption in tobacco factory is huge and there is great potential of energy saving in tobacco enterprises because less attention has been paid in this area. Air conditioning system contributes30%-50%of the annual total energy consumption in cigarette factory, so more and more attention should be paid to finding ways of conserving energy in the system. The purpose of the dissertation is to find the main reasons which contribute to the unreasonable energy consumption by field test and simulation, and to propose a novel air conditioning system which can eliminate the disadvantages of existing air conditioning system. The main contributions and conclusions of the dissertation are as follows:Firstly, the energy consumption of different sectors and cooling/heating load was investigated in several cigarette factories. A calculation model for cooling/heating load was built and verified by the test results. The annual cooling/heating load in five typical cities was calculated by this model and the features were summarized. After analyzing the test and simulation results, the main reasons that contribute to high energy consumption of existing air conditioning system were summarized as follows:(1) unnecessary cooling offset by reheating;(2) low efficiency of high grade energy;(3) low energy efficiency of chillers under partial cooling load;(4) much higher capacity of fans and pumps than the needed causing "large air volume, small enthalpy difference " and "large water flow rate, small temperature difference";(5) high energy consumption of fans caused by long distance distribution of return air. Energy can be saved by increasing the temperature of supplied chilled water to some extent, but the efficiency improvement of the chiller is restricted to the requirement of the terminal which needs the lowest temperature of chilled water. The application of free-cooling by cooling tower can also save energy in cool season, but the fluctuated temperature of cooling water from the cooling tower limits the energy saving ratio because of the constant temperature and humidity required in the whole year in most workshops of cigarette factory.Secondly, a new method of analyzing annual sensible and latent load was proposed to learn the load features in cigarette factory thoroughly. In this method, the hourly sensible load and latent load are taken as ordinate scale and horizontal axis separately. The positive sensible and latent load is defined as cooling and dehumidification, and the negative as heating and humidification. The distribution of hourly sensible load and latent load figures out the tasks of the air conditioning system in the whole year and helps people to design and select the air handling equipment conveniently. The proper annual air handling processes applied in different workshops can be obtained after the annual load of cigarette factory is analyzed by this sensible-latent load method.Thirdly, a novel central air conditioning system based on energy-bus and integrated refrigeration system with thermosyphon function for cigarette factory is proposed. This system takes water loop as the energy distribution bus and the terminals are direct-expansion water cooling/heating AHUs with thermosyphon. The main advantages of the novel system is as follows:(1) no chilled water and decentralized terminals make the system be designed and adjusted flexibly according to the requirements of different workshops instead of centralized production of chilled water;(2) the water temperature in water loop is closer to the ambient than that of chilled water and high temperature heat source so that the heat rejected in building can be recovered easily and the cooling/heating loss during the distribution process can be reduced;(3) the direct-expansion water cooling/heating equipments with thermosyphon can effectively utilize the low grade natural source and high grade heat source.Finally, the energy consumption of the new system applied in different cities was simulated and the energy saving rate compared to all-air system was analyzed. It is shown that the new system has great potential in energy saving. According to the distribution of the cigarette production, the new central air conditioning system has great application prospect in cigarette factory in China.