Performance Study Of Combined Cooling,heating And Power System Based On Natural Gas Engine And Absorption Chiller

Energy is the material basis of human society's development and directly promotes the progress of human civilization and world economy.Throughout the human's history,every great change of society comes along with the improvement and replacement of energy.Today,faced with increasingly serious resource and environment problems,all the countries in the world are particularly focusing on energy conservation and emissions reduction.To solve this problem,in addition to develop new energy vigorously,but how to save conventional energy and improve the efficiency of single equipment,especially the system energy comprehensive utilization rate,is the top priority.Due to the advantages of fuel diversity,high energy efficient utilization,flexible system composition,distributed energy systems attract broad attention throughout the world.In this paper,the performance of the main equipments of CCHP system(natural gas engine,exhaust gas-water heat exchanger and lithium bromide absorption chiller)are researched by experimental study and simulation analysis.The main research contents are as follows:1)Analysis all kinds of waste heat flux characteristics and the potential of waste heat recovery through the experimental study on the thermal equilibrium of the gas engine.The maximum engine thermal efficiency of the gas engine is nearly to 40%,which appears nearby the maximum torque speed(1400r/min)and the exergy efficiency of the effective work is above 30% in the high load of the whole speed range.Exhaust waste heat energy reaches a maximum value of 217.6 kW in the full load working conditions of calibration speed,which accounts for about 28% of the total fuel energy.Exhaust exergy efficiency increases with the increase of engine speed and reaches nearly 20% under the conditions of high speed and high load.Engine cooling water energy increases with the increase of engine speed and the maximum value is about 189.9 kW in the full load working conditions of calibration speed,which accounts for about 24% of the total fuel energy.The exergy efficiency of cooling water is only about 5% under all the working conditions.Inter-cooler energy increases with the engine speed and reaches a maximum percentage about 5.4% in the calibration speed.The exergy efficiency is below 2% under all the working conditions.2)Calculate the thermal physical properties of engine exhaust gas under different working conditions,and then establish an exhaust gas-water heat exchanger model,at last simulate the flow field and temperature field with software Fluent.With the improvement of engine speed and load rate,both of the water temperature difference and heat transfer increased gradually.At the speed of 2100r/min,the temperature difference between in and out water is the largest,about 7.3? and heat transfer is nearly 50 kw.3)The thermal physical property equations of lithium bromide aqueous solution and water and water vapor are obtained by computer software programming.On this basis,establish the mathematical model of the LiBr absorption chiller and analyze the performance of the refrigeration unit with the change of heat source water inlet temperature and cooling water inlet temperature according to the results of simulation.With the increase of heat source water inlet temperature,the thermal load of heat exchanger decreases slightly,and the rest parts of the unit are in linear growth,and COP increases from 0.65 to 0.75.With the increase of cooling water inlet temperature,the trend of the equipment's thermal load are just the opposite,and COP decreases from 0.84 to 0.33.4)Establish the mathematical models of the separated system and CCHP system.Analyze the primary energy saving ration(PESR)and carbon dioxide reduction ratio(CRR)under the same exports of electricity,cooling and heating.From the test bench analysis and calculation can be seen that,PESR of the system increase with the increase of engine load under the same speed.Test system is not energy saving at low load working conditions of all the different speeds and has better PESR under the low speed conditions than high speed.However,system's CRR is much better than PESR and above zero under all of the working conditions.This shows that the CCHP system with natural gas has great advantage in carbon emissions.