Simulation Analysis And Evaluation On The Thermal Performance Of A Combined Cooling Heating And Power System

At present,the contradiction between energy demand and environmental protection pressure is becoming increasingly prominent in China.Improving energy efficiency and reducing pollution gas emissions are effective ways to solve this contradiction.As a new form of energy utilization,the combined cooling heating and power?CCHP?system has attracted more and more attention because of its high-energy utilization rate,clean and environmental protection.Due to the diversity of energy utilization modes and the complexity of conversion process in CCHP system,the inadequate recovery of low-grade waste heat such as cylinder liner water and low temperature flue gas waste heat in the system leads to the decrease of overall thermal and economic performance.The utilization mode of waste heat in the system and the corresponding thermal performance analysis need to be further studied.Therefore,this paper puts forward an operation scheme of CCHP system with internal combustion engine as the power engine.Considering the influence of integration scheme,power of internal combustion engine,the temperature of waste heat and external environmental factors on thermal performance,the thermal performance of the system is studied and evaluated,which provides some reference suggestions on the way of utilizing waste heat in CCHP,improving primary energy utilization rate and waste heat utilization rate,and has the certain practical application value.The researches carried out in this paper are as follows:?1?An operation scheme of CCHP system with internal combustion engine as the power engine is proposed.The power subsystem is the internal combustion engine;the refrigeration subsystem consists of two heat exchangers and a single-effect lithium bromide refrigerator.The heat exchanger recovers the waste heat of cylinder liner water and flue gas successively,and heats the driving heat source water of lithium bromide refrigerator;the heating subsystem includes two heat exchangers,one air preheater and air source heat pump,which recovers the waste heat of cylinder liner water and high temperature flue gas.It can also recover the waste heat of low temperature flue gas to improve the utilization rate of waste heat.?2?According to the above-mentioned operation scheme,the mathematical model of the internal components of the system is constructed,and the physical models of the refrigeration subsystem and the heating subsystem are modeled respectively by using simulation software Aspen Plus.The thermodynamic performance and variation law of the system are simulated and analyzed when the internal combustion engine is running from start-up to full load.The variation rules of the system parameters such as waste heat utilization rate,energy supply and heat pump performance coefficient are studied when the power changes.The results show that the system can realize deep recovery of high-grade and low-grade waste heat,and has obvious advantages in improving energy supply,waste heat recovery rate and performance coefficient of the system.?3?Combining the working results of the refrigeration subsystem and the heating subsystem,the energy conversion flow process under different operating modes of the system is analyzed,and the traditional distribution system is taken as a reference system,to evaluate and study the thermal,environmental and economic aspects of the CCHP system in this paper.The thermal evaluation mainly includes the proportion of waste heat ratio,primary energy utilization ratio,heat-power ratio and cold-power ratio with power;CO₂ emission reduction rate is selected as the index of environmental protection evaluation;and operation cost saving rate is selected as the index of economic evaluation.The results show that the operation scheme of CCHP system with internal combustion engine as the power engine proposed in this paper,it can improve energy utilization,reduce CO₂ emissions and improve economy in a certain load area.