Research On Optimal Control Of Ethylene Glycol Heat Exchanger In Communication Center

Energy saving and emission reduction have been one of the hot problems all over the world with the increasingly rigorous energy crisis. The consumption of communication equipment in which the internal units of communication center and communication base station have large amounts of heat dissipation and need refrigeration year-round without intermission to control the indoor temperature occupies a large part of total energy consumption. In addition, there is strict requires for some environment parameters, such as humidity and cleanliness, in the normal operation of communication equipment. At present, air-condition which power consumption account for about45%of the total power consumption of communication center and produce greenhouse gases is the main temperature control equipment in communication center. The ethylene glycol heat exchanger which works with the difference in temperature between the ambient energy and inside can screen the effect of dust, impurities and moisture outside air. However, the ethylene glycol heat exchanger does not replace the air condition due to the boundedness that the operation premise of ethylene glycol heat exchanger is temperature difference. The energy saving goal of communication center can be achieved with the linkage control of ethylene glycol heat exchanger and air condition system. In this paper, the research of ethylene glycol heat exchanger focuses on following aspects.1) After the in-depth study of utilization of ambient energy in different climate zones, the simulation model of communication center which is built in terms of actual communication center is systematically analyzed on structure characteristics and heating load characteristics in different climate zones. The results show that the suited building envelope of communication center for Harbin is brick37and color plate50, the suited building envelope of communication center for Beijing, Wuhan, Nanning and Kunming is brick24and color plate50, air condition heating load of communication center exists in Harbin’s winter and the communication center of Beijing, Wuhan, Nanning and Kunming need refrigeration year-round, the available time of ambient energy for Harbin is9months, for Beijing, Wuhan and Nanning is about bmonths and for Nanning is3months, the ambient energy technology in communication center which share the most cooling load for air condition and shorten the working time of air condition can save the energy consumption of air condition and the theory of ethylene glycol heat exchanger is feasible by means of the analysis of ambient energy utilization.2) The simulation model parameters of ethylene glycol heat exchanger are analyzed and calculated on two aspects. One is the physical characteristics analysis of fluid in heat exchanger, including the density, specific heat, thermal conductivity and dynamic viscosity of glycol solution. Another is the calculation of heat parameter, including the preliminary scheme and geometric parameters calculation of heat exchanger structure, the flow velocity of heat exchanger secondary refrigerant, the air quantity outside and inside, the mean temperature difference of heat exchanger outside and inside, the heat transfer coefficient of tube film inside and outside, the fin efficiency, the coefficient and appearance structure of heat transfer and the type selection of draught fan and circulating pump. The results show that in Harbin, the suited refrigerant of heat exchanger is50%volume concentration glycol solution, in Beijing, the value is40%volume concentration, in Wuhan and Kunming, the refrigerant of heat exchanger is20%volume concentration glycol solution and0%volume concentration is needed in Nanning where the temperature is above the freezing point of water year-round. The heat exchanger model is suit for ccmmimication center of five representative areas.3) The control parameters of ethylene glycol heat exchanger are optimally designed and the power model which satisfies the constraint is built in terms of the theoretical analysis and calculation. The optimal solution of power model on discrete temperature difference points is obtained with the genetic algorithm and effective set algorithm. And then, the power characteristics and frequency characteristics of continuous temperature difference are forecasted with Elman neural network to get the power and frequency model with the50%,40%,20%and0%volume concentration glycol solution as the refrigerants. The error analysis between heat transfer and consumed power of pump and draught fan from model which can control frequency conversion parameter and actual data obtaining from the simulation environment in heat balance laboratory is done to get the results that the absolute error which is controlled in5%can meet the actual frequency conversion controlling requirement. Therefore, the energy conservation of heat exchanger pump and draught fan is precise and reliable with frequency conversion parameter which is controlled by power model.4) With the comprehensive analysis of energy conservation with ethylene glycol heat exchanger in communication center, with linkage system of ethylene glycol heat exchanger and air condition and the annual energy consumption with independent control of air condition among the suited building envelop in communication center of five representative areas can be obtained by building the energy efficiency ratio model of ethylene glycol heat exchanger. Then the energy conservation rate and annual utilization time of ethylene glycol heat exchanger are figured out. The results show that energy consumption with ethylene glycol heat exchanger is significantly smaller than energy consumption with air condition under the same cooling load conditions in center. The utilization times with ethylene glycol heat exchanger in the five representative areas are about9months in Harbin, more than6months in Beijing, more than5months in Wuhan, about3months in Nanning and6months in Kunming. In Harbin, the annual energy conservation rate can reach31.9%under the linkage system of ethylene glycol heat exchanger and air condition with brick37building envelope, moreover, in Beijing, Wuhan, Nanning and Kunming, the annual energy conservation rate can separately reach24%,20.5%,10.5%, and33.5%under the linkage system of ethylcne glycol heat exchanger and air condition with brick24building envelope. In Harbin, Beijing, Wuhan, Nanning and Kunming, the annual energy conservation rate can separately reach42.7%,35.4%,28.4%,12.9%and34.5%under the linkage system with plate50building envelope. Therefore, on the energy conservation application of China’s communication centers, the ethylene glycol heat exchanger can express great potential.In this paper, the research applies the theory and application foundation for the energy conservation of ethylene glycol heat exchanger in communication, especially, offering the technology supply on heat exchanger design and frequency conversion control theory. Meanwhile, the comprehensive and in-depth research of region characteristics and energy conservation efficiency on the ambient energy utilization of ethylene glycol heat exchanger open up vast potential for future development for the green energy conservation of communication.