The Feasibility Research On Retrofit Scheme Of The Air-conditioning System And The Optimal Design Research Of Direct-Fired Chillers Assist With Solar Collectors And Waste Heat Recovery Unit At No.4 College Building

The lithium bromide absorption direct-fired chillers,which are widespread used in our country,are grown rapidly during the past years due to power shortage.While, low energy efficiency and poor economy performance make the use of direct-fired chillers to be questioned.In addition,with the natural gas price rising,the problem will be even worse.The introduction of renewable energy into direct-fired chillers and improve it's energy efficiency are great significance to gas saving and environmental protection.This paper,begin with building energy analysis,the cooling and heating load and annual energy consumption of the the building are calculated,which use the energy analysis software,Energyplus,based on the establishment of the building computing model.From the energy simulation result,one of the units is able to meet the requirements,while the heating and cooling source of No.4 building in Donghua University is composed of two direct-fired chillers.So,a new direct-fired chillers assist with solar collectors and waste heat recovery unit is bring forward inorder to improve the original system's energy efficiency and economy performance,and the feasibility of it's used for heating is analysised.Solar collection and waste heat recovery capacity are calculated based on the requirements of the system and the characteristic of solar radiation and waste heat contained in direct-fired chiller's exhaust gas.A new optimization model,which minimum annual cost as the objective function is established.With the help of Matlab optimization toolbox,we can know the minimum annual cost of the new system is 109,6000 yuan,higher than the former, 1,042,300 yuan.The results show that the new system is not economic,while energy-saving effect is significantly,which gas consumption reduced 7.3×103 Nm~3 and the exergetic efficiency value improved 1.1%.Main factors sensitivity analysis shows that the new system will reflect good economy,which means the new system's annual cost lower than the original one, when the system running time is up to 1184.5 hours.Also,the price of gas and solar collectors will affect the new system's economy.The optimization results show that after the gas price raise to 3.08 yuan/m~3 or the solar collectors price fall down to 442.0 yuan/m~2 the new system will show good economy,when the system running time is 828 hours.From the analysis we can know that gas prices have higher sensitivity affect than solar collectors price.From the point view of efficient and conservation use of energy,direct-fired chillers change to direct-fired chillers assist with solar collectors and waste heat recovery unit is an ideal choice.The conclusion of this paper that the new system reflect no economy because the inefficient use of the system.Once the rational use in summer is taken in consideration,the new system will bring economic improvement.The newly proposed direct-fired chillers assist with solar collectors and waste heat recovery unit provided a new way of thinking to direct-fired chillers reform, which can reduce not only the gas consume,but also environmental pollution.