| Through the research of development characteristics and design methods on the existing ground source heat pump system,this article notices that,in the current design scheme,the horizontal circuit header’s heat transfer in vertical borehole Ground source heat pump system hasn’t been considered at all during heating period.With the increasing scale of ground source heat pump system design in China,it is worth to exploring and paying attention on what influences it will bring.Based upon the actual design and the accumulation of basic data in the tes ted project,this work puts forward several possible key factors that may influence the horizontal circuit header’s heat transfer.By establishing mathematical model and discretely analyzing for the horizontal circuit header,the influence and the relation of primary and secondary that several factors may put on the horizontal circuit header’s heat loss can be obtained.Inspired by the analysis of influence factors,this paper focuses on several office buildings in the typical city of Tianjin.After the c onversion of the horizontal circuit header connection model,simulation analysis can be reached based on its specific application in office buildings.In the case of Tianjin in winter,with different length of the horizontal circuit header,simulation resu lts are shown as follows:When both sides,namely inflow and outflow,of the horizontal circuit header’s length is below 50 meters,the COP of units fells less than 7% and can be ignored in project.Thus directly buried installation method can be employed without taking any measures to the horizontal circuit header.When the length of both the inflow and outflow of the horizontal circuit header is 75 meters,the COP of units fells 6%~9% caused by the outflow side.It is better to take measures to reduce the loss of heat dissipation.Mean while the percentage of the COP falls slightly by the inflow side units,to have a positive influence on the system,taking no measures on the inflow side of the horizontal circuit header and strengthening the heat transfer of this part are appropriate.When the length of the inflow and outflow of the horizontal circuit header is 100 meters long on both sides,the outflow side makes a drop between 7% and 10.8% on the COP of units.Some measures should be taken to reduce the h eat dissipation on the outflow side.At the same time,since the percentage of the COP falls obviously by the inflow side units,heat transfer strengthening without heat preservation measures.When the length of both horizontal circuit header is 200 meters,the COP of units fells 11.5%~5.2% caused by the outflow side.In this case,we must take measures to reduce the heat dissipation on the outflow side.On the other hand,the percentage of the COP has a significant reduction by the inflow side units.To have a positive influence on the system,taking no heat preservation measures and strengthening the heat transfer are suitable.Besides the research conclusions above,combined with the analysis on the influence factors of energy loss of horizontal circuit header,this paper also further discusses methods of avoiding energy loss of horizontal circuit header,such as increasing buried depth or thermal insulation layer to reduce the negative impact on the system and the heat pump units during the heating perio d.Then,by analyzing a project measured data,the reliable effect of adding thermal insulation layer is also illustrateed in this paper. |
