Study On The Co-efficiency Of Performance Of Soil Source Coupled With Other Source Heat Pump System Of Office Buildings

The ground heat exchanger is the one of most important heat transfer exchangersof the soil source heat pump system. Its heat transfer performance seriously impactsthe co-efficiency of performance of soil source heat pump system. Because of theintermittent using of the office buildings and the limitation of the soil energy balanceof the rejection and absorption of soil, soil source heat pumps need to be combinedwith other auxiliary cooling equipments. Thus, the load and distribution characteristicsof the ground heat exchangers ultimately affect the performance of the energyefficiency of the soil source and multi source composite heat pump systems. Factorsaffect the efficiency characteristics of soil source and multi-source composited heatpump system were studied in this paper, and new ground source multi-sourcecomposite heat pump systems with higher co-efficiency of performance wereproposed.Calculation models according to the heat transfer mechanism of ground heatexchangers were built. Taking ground heat exchangers borehole wall as the boundary,the ground heat exchangers were divided into internal and external parts; the internalpart used the analytical calculation models and the external part used the numericalcalculation model. The two parts were analyzed symmetrically to simplify the externalmodels and reduce the number of times to be calculated.MATLAB software was chosen to program and calculate the external models, andthe2012summer conditions measured data of Dushizhimen was taken as the heatinput values for programming and calculating. Rejecting gross errors, the average error between the calculated results and the measured data was1.7%, while the relativeerrors were within5%, verifying the correctness of the ground heat exchanger models.DeST software was used to calculate the cooling and heating load of the officeproject to be built in Xi’an. Calculated load was carefully distributed to differentseasons by proposed methods and using this load distribution and after the operation ofground heat exchangers for8760hours, the average soil temperature only increased by0.19℃, and thus ensured the heat transfer performance of the ground heat exchangers.Intermittent operation of office buildings played an important role in improvingthe ground heat exchangers heat transfer performance. The outlet temperature ofground heat exchanger no matter in winter or summer did not cause the alarm becauseof too high or too low temperatures. After heat pump units are turned off for11hoursin winter/summer condition, the borehole wall temperature respectively reversed by2.65/2.16℃.Whether it is summer conditions or winter conditions, running a24-hourcycle, soil temperature rise or fell only within0.02℃, and when the heat pump unitswere turned on the next day, the whole soil temperature was nearly equal to the soiltemperature when the heat pump units are turned on this day.This paper proposed an innovative dual-source coupled heat pump system usingthe soil source and sewage source and its operation principle. By calculation, this newheat pump system, in winter conditions, could save as much as30%energy thantraditional conditioning system. In summer conditions, this new heat pump systemcould save11.9%and9.5%energy than traditional cooling tower and soil source andcooling tower coupled heat pump system respectively. This paper provides somereference for the design of the air conditioning systems of office buildings.