Performance Analysis Of Central Heating Systems Boosted By Absorption Heat Pumps

As a class of heat-driven heat pumps,absorption heat pumps can effectively improve the heating capacity and exergy efficiency of the central heating systems.Existing studies have focused on the advantages of the absorption heat pump in improving the heating capacity of the primary-network side.Most of them ignored the impact on heating parameters of the secondary-network side.This paper develops a simulation algorithm for absorption heat pumps first.Based on parameter analysis,we analyzed the effect of an absorption heat pump on the heating temperature and heating load of the secondary-network side,further elucidating the impact of absorption heat pumps on the overall performance of heating systems of the substation.Firstly,this paper conducted the exergy analysis of the typical combined secondary-network side heating system(abbreviated as the combined heating system)and separate secondary-network side heating system(abbreviated as the separate heating system)and compared them with the conventional heating systems of the substation.The results showed that the absorption heat pump could increase the heating load of the primary-network side by about 64% and increase the exergy efficiency by about 13% under the same working conditions.Secondly,this paper analyzed how the combined heating system and separate heating system performance change with heating parameters of the primary and secondary networks.The combined heating system that distributes heat load is characterized by all users sharing one secondarynetwork pipeline.The heating demand of the original users using this system only could be kept by increasing the supply water flow rate on the secondary-network side.Meanwhile,the supply water temperature of the original users is bound to be lower than the previous level,which is to exchange the "quality" decline for the "quantity" increase.For the cases of high supply water temperature and high flow rate of the primarynetwork side,the new users can obtain a higher heat load,and original users require less secondary supply water flow rate to maintain the heat load.But the higher supply water temperature and flow rate of the primary-network side have no significant effect on the supply water temperature of the secondary network.The heat load distribution ratio between the new users and the original users is about 9:5,with setting the same equipment parameters for the separate heating system as the combined heating system and the same return water temperature and flow rate of new users as original users on the secondary-network side,t.That ratio increases with the increase of the primary network diversion ratio,the supply water temperature and flow rate of the primary network,the return water flow rate of the new users on the secondary-network side,and decreases with the increase of the return water flow rate of the original users on the secondary-network side.The separate heating system has the same capacity for expanding the primary network as the combined heating system.But under the same working conditions,the supply water temperature of the original users is 6℃ lower than that of the combined heating system.Moreover,the supply water temperature of the new users is about 3°C higher than that of the combined heating system,which can reach the secondary water supply temperature when the conventional heating system is in place,65°C.The separate heating system can obtain a higher heat load for the cases of higher supply water temperature and flow rate of the primary network.It also significantly increases the temperature of secondary supply water.