Study On Performance Optimization Of Coupled Central Heating Of Solar Collector Driven By Absorption Heat Pump

With the development of Chinese economy,the heating system depended on traditional fossil energy has made exhausted energy and caused serious environmental pollution.Therefore,solar heating systems are favored.However,the performance of the system is affected directly by meteorological conditions and heat requirement of users,problems such as high return water temperature leading to low heat collection efficiency and low water supply temperature leading to small heating radius exist in the operation of solar energy heating system,especially in large solar energy central heating system.The more the load contradiction between the solar energy collection side and the user side is,the more serious the problem is.Even though the thermal storage system could alleviate this problem to some extent,the search for a new system for improving efficiency is a basic way to solve this problem fundamentally.Based on these problems,this paper proposes a coupled solar heating system of absorption heat pump and solar energy heat collection system.In this system,the medium temperature collector（concentrating collector）is used as the driving heat source of the absorption heat pump,so as to reduce the inlet temperature of the low temperature collector（flat-plate collector）,improve the heat collection efficiency and increase the heating capacity.According to the working principle of the system,the physical model of the absorption heat pump-solar collector coupling heating system is established in this paper.On the basis of theoretical analysis,a running program of the lithium bromide absorption heat pump is written using MATLAB software according to the thermophysical properties of the lithium bromide solution with MATLAB software,which is called in TRNSYS software to simulate the system.Besides,taking Lhasa city as an example,the heating performance of the coupling system is comprehensively analyzed,and the influence of concentrating collector area,absorption heat pump capacity,storage tank volume and collector flow rate on the performance of coupling system are studied.In addition,the differences in thermal performance,economy,energy saving and environmental protection of absorption heat pump-solar coupling heating system,flat-plate collector heating system and plate–concentrating collectors series heating system are compared and analyzed.Finally,Lhasa,Xi’an,Xining and Yinchuan,the typical cities in the solar energy rich area in western China,are selected to study the performance characteristics of the system in different regions.The simulation results show that increasing the area of the concentrating collector,increasing the capacity of the absorption heat pump,decreasing the flow rate of the collector and reducing the volume of the heat storage tank can reduce the inlet temperature of the flat-plate collector,increase the heating temperature of the system,increase the heat collection efficiency,increase the heating capacity and improve the performance of the system.In addition,under the same heat collecting areas,compared with the flat-plate collector solar heating system and the flat-plate and concentrating collectors series heating system,the coupled heating system could effectively reduce the inlet temperature of flat-plate collector,improve the heat collection efficiency,increase heat collection and supplied heat,reduce energy consumption（coal usage）and CO₂ emissions at a time.In terms of economy,compared with the flat-plate collector solar heating system,the initial investment of the absorption heat pump coupled solar heating system increases by about 14.7%,while the system income increases by 30%.Compared with the flat-plate and concentrating collectors series heating system,the initial investment of the absorption heat pump solar coupled heating system increases by about 2.3%,and the system income increases by 10%.Due to the influence of solar radiation intensity and outdoor weather conditions,the performance of coupled solar heating system varies in these four regions.In Lhasa,where the solar radiation intensity is the highest,the coupled system has the best performance,the highest water supply temperature,the lowest collector inlet temperature,and the highest heat collection efficiency and solar energy utilization rate.Through the above theoretical analysis and numerical simulation,the performance of the absorption heat pump and solar coupled heating system is obtained under different operation parameters.The influence of area of the concentrating collector,the capacity of the absorption heat pump,the volume of storage tank,and the flow rate of concentrating collector on the inlet temperature of flat-plate collector,heat collection efficiency,and heating temperature is clarified,and the operation effect of the coupled system in different regions is mastered.This study provides a new system scheme for the efficient and safe operation of large-scale solar central heating system in the solar energy rich area,and plays a certain role in promoting the development and popularization of solar central heating system.