| In the severe cold area,the heat exchanger freezes and cracks in the air conditioning system and the unit shuts down frequently due to the freezing of heat exchanger.In this paper,a diesel engine test building is taken as the research object,the actual measurement is carried out,the existing problems of the air conditioning system are summarized and the reasons are analyzed,and the anti-freezing transformation strategy of the air conditioning system is proposed.The optimization method of anti-freezing reconstruction scheme of air conditioning system was studied,and the evaluation index system of anti-freezing reconstruction scheme of air conditioning system was constructed by selecting evaluation indexes.The interlocking control system of electric heating and side ventilation pipes was proposed,and the system energy consumption model and indoor thermal comfort model were established.The operation optimization parameters of the system were calculated when the energy consumption was minimum and the comfort level was highest simultaneously.The TRNSYS simulation platform of the interlocking control antifreeze system of electric heating and side ventilation pipe was established to simulate the operation of the optimized transformation scheme of the airconditioning system,and analyze the antifreeze effect after the transformation and the change of energy consumption and thermal comfort value after the optimization of operating parameters.Firstly,a diesel engine test house is measured and the related parameters are calculated,and the existing problems are analyzed.Firstly,the anti-freezing performance of the existing air conditioning system is not considered in the design,so it is easy to shut down under the extreme temperature,and the air conditioning system is not designed properly.Second,in order to prevent freezing,the air conditioning system adopts the operation strategy of low fresh air volume,which leads to insufficient indoor fresh air volume,poor thermal environment and improper operation strategy.Suggestions are put forward to solve two problems: firstly,the existing air conditioning system should be reformed to protect the heat exchanger with effective anti-freezing air conditioning system;Using frequency conversion water pump and intelligent control system,make effective anti-freezing operation strategy.Secondly,the evaluation index system of air-conditioning system renovation is established and the weights of the first and second indexes are established.By combining the traditional antifreeze method of electric heater preheating method and bypass method,a new antifreeze system with auxiliary electric heating and interlocking control of bypass duct is proposed,which achieves the purpose of antifreeze by changing the pre-heat of fresh air and adjusting the air flow through the heat exchanger.The grey relational degree method is used to evaluate the electric heating-by-pass antifreeze system and other two comparative improvement schemes.The calculation results of the relational degree of the three schemes are as follows: scheme A0.7512,scheme B0.7254 and scheme C0.6760,and the optimal scheme is scheme A.An energy consumption model composed of the energy consumption of the electric heater,heat exchanger,hot water pump,the main fan and the induced draft fan of the side duct was established for the coupled control air conditioning system with electric heating and side ventilation ducts.PMV and PPD were selected as the indoor thermal environment evaluation indexes from the evaluation indexes of thermal comfort.To characterize the indoor personnel are not satisfied with the environment percentage index PPD thermal comfort model is established,through the establishment of energy consumption-both thermal comfort multiobjective optimization model,rules on the constraint conditions,using non dominated sorting genetic algorithm(NSGA II)on the multi-objective optimization computation,it is concluded that the system energy consumption minimum and optimal operation parameters of the highest comfort.Finally,through building load model and TRNSYS module of each equipment of air conditioning system,the TRNSYS simulation platform of electric heating and side ventilation interlocking control of fresh air anti-freezing system is established.TRNSYS simulation platform was used to simulate the optimal operating parameters of the air conditioning system,which confirmed the feasibility of the optimization scheme of the air conditioning system reconstruction.Compared with the original system,its antifreeze performance was improved.Compared with the original operating parameters,the optimized operating parameters make the energy consumption-thermal comfort of the system reach the comprehensive optimum. |
