Aimed at unbalance of soil temperature field of ground source heat pump system, solar aided energy storage system was established. In solar assisted ground-source heat pump (SAGSHP) system with soil storage, solar ene...Aimed at unbalance of soil temperature field of ground source heat pump system, solar aided energy storage system was established. In solar assisted ground-source heat pump (SAGSHP) system with soil storage, solar energy collected in three seasons was stored in the soil by vertical U type soil exchangers. The heat abstracted by the ground-source heat pump and collected by the solar collector was employed to heating. Some of the soil heat exchangers were used to store solar energy in the soil so as to be used in next winter after this heating period; and the others were used to extract cooling energy directly in the soil by circulation pump for air conditioning in summer. After that solar energy began to be stored in the soil and ended before heating period. Three dimensional dynamic numerical simulations were built for soil and soil heat exchanger through finite element method. Simulation was done in different strata month by month. Variation and restoration of soil temperature were studied. Economy and reliability of long term SAGSHP system were revealed. It can be seen that soil temperature is about 3 ℃ higher than the original one after one year's running. It is beneficial for the system to operate for long period.展开更多
This paper uses FLUENT software building the three-dimensional unsteady state model of ground source heat pump single U and double U underground pipe to study on heat exchange of underground pipe system in the conditi...This paper uses FLUENT software building the three-dimensional unsteady state model of ground source heat pump single U and double U underground pipe to study on heat exchange of underground pipe system in the condition of unsteady state long-term continuous running, analyzes the change of soil temperature filed around underground pipe and performance of underground pipe heat exchange between single U and double U pipe system. The results show that double U pipe system is better than single U system, which can improve unit depth heat exchange efficiency, reduce the number of wells and reduce the initial investment.展开更多
Energy piles have attracted increasing interest for application in ground source heat pumps,because it is environment-friendly,energy-efficient,and without additional drilling cost.However,when there is a large dif-fe...Energy piles have attracted increasing interest for application in ground source heat pumps,because it is environment-friendly,energy-efficient,and without additional drilling cost.However,when there is a large dif-ference between the heating and cooling loads,the system will suffer from a soil thermal imbalance which may further decline the system performance and even cause a system failure.A hybrid ground source heat pump sys-tem that integrates auxiliary equipment can solve the problem,however,it needs additional investment and a complicated control strategy.In this paper,the zoning operation of energy piles can effectively improve the tem-perature recovery ability of soil in the energy pile group and thus alleviate the soil thermal imbalance.Specifically,a heating-dominated residential building in Beijing is selected for a case study,with 144 energy piles arranged in a 12×12 layout.An analytical model of the spiral-coil energy pile group with seepage will be adopted,which can consider the groundwater flow,the geometry of spiral coils,and the thermal interaction among different energy piles,achieving high calculation accuracy and fast calculation speed.Based on this analytical energy pile model,a system model will be built to investigate the system performance influenced by different zoning operation strategies.Results show that intensive heat injection into the center of the pile group(Strategy 2 and Strategy 3)or heat extraction from the outer layer of the pile group(Strategy 4)can relieve the cold accumulation.Strategy 2 can relieve the outlet temperature decline from 5.54℃ to 4.46℃ and improve the heating COP from 3.297 to 3.423 compared to the conventional full operation strategy.Although the annual heat pump COP of Strategy 2 is a little lower than that of conventional full operation strategy,Strategy 2 has the shortest unmet heating or cooling time.Therefore,the proposed zoning operation strategy can achieve good system efficiency and excellent system reliability compared to the conventional strategy.展开更多
A simplified numerical model of heat transfer characteristics of horizontal ground heat exchanger (GHE) in the frozen soil layer is presented and the steady-state distribution of temperature field is simulated. Numeri...A simplified numerical model of heat transfer characteristics of horizontal ground heat exchanger (GHE) in the frozen soil layer is presented and the steady-state distribution of temperature field is simulated. Numerical results show that the frozen depth mainly depends on the soil′s moisture content and ambient temperature. The heat transfer loss of horizontal GHE tends to grow with the increase of the soil′s moisture content and the decrease of ambient temperature. Backfilled materials with optimal thermal conductivity can reduce the thermal loss effectively in the frozen soil. The applicability of the Chinese national standard “Technical Code for Ground Source Heat Pump (GB 50366-2005)” is verified. For a ground source heat pump project, the feasible layout of horizontal GHE should be determined based on the integration of the soil′s structure, backfilled materials, weather data, and economic analysis.展开更多
基金Project(GC06A316) supported by the Key Technologies Research and Development Program of Heilongjiang Province, China Project(11531038) supported by the Program of the Educational Commission of Heilongjiang Province of China.
文摘Aimed at unbalance of soil temperature field of ground source heat pump system, solar aided energy storage system was established. In solar assisted ground-source heat pump (SAGSHP) system with soil storage, solar energy collected in three seasons was stored in the soil by vertical U type soil exchangers. The heat abstracted by the ground-source heat pump and collected by the solar collector was employed to heating. Some of the soil heat exchangers were used to store solar energy in the soil so as to be used in next winter after this heating period; and the others were used to extract cooling energy directly in the soil by circulation pump for air conditioning in summer. After that solar energy began to be stored in the soil and ended before heating period. Three dimensional dynamic numerical simulations were built for soil and soil heat exchanger through finite element method. Simulation was done in different strata month by month. Variation and restoration of soil temperature were studied. Economy and reliability of long term SAGSHP system were revealed. It can be seen that soil temperature is about 3 ℃ higher than the original one after one year's running. It is beneficial for the system to operate for long period.
文摘This paper uses FLUENT software building the three-dimensional unsteady state model of ground source heat pump single U and double U underground pipe to study on heat exchange of underground pipe system in the condition of unsteady state long-term continuous running, analyzes the change of soil temperature filed around underground pipe and performance of underground pipe heat exchange between single U and double U pipe system. The results show that double U pipe system is better than single U system, which can improve unit depth heat exchange efficiency, reduce the number of wells and reduce the initial investment.
基金The authors gratefully acknowledge the funding support from Sun Yat-Sen University(76140-18841230 and 2021qntd15)Guangdong Basic and Applied Basic Research Foundation(2021A1515011739,2020A1515110391 and 2020B1515120083).
文摘Energy piles have attracted increasing interest for application in ground source heat pumps,because it is environment-friendly,energy-efficient,and without additional drilling cost.However,when there is a large dif-ference between the heating and cooling loads,the system will suffer from a soil thermal imbalance which may further decline the system performance and even cause a system failure.A hybrid ground source heat pump sys-tem that integrates auxiliary equipment can solve the problem,however,it needs additional investment and a complicated control strategy.In this paper,the zoning operation of energy piles can effectively improve the tem-perature recovery ability of soil in the energy pile group and thus alleviate the soil thermal imbalance.Specifically,a heating-dominated residential building in Beijing is selected for a case study,with 144 energy piles arranged in a 12×12 layout.An analytical model of the spiral-coil energy pile group with seepage will be adopted,which can consider the groundwater flow,the geometry of spiral coils,and the thermal interaction among different energy piles,achieving high calculation accuracy and fast calculation speed.Based on this analytical energy pile model,a system model will be built to investigate the system performance influenced by different zoning operation strategies.Results show that intensive heat injection into the center of the pile group(Strategy 2 and Strategy 3)or heat extraction from the outer layer of the pile group(Strategy 4)can relieve the cold accumulation.Strategy 2 can relieve the outlet temperature decline from 5.54℃ to 4.46℃ and improve the heating COP from 3.297 to 3.423 compared to the conventional full operation strategy.Although the annual heat pump COP of Strategy 2 is a little lower than that of conventional full operation strategy,Strategy 2 has the shortest unmet heating or cooling time.Therefore,the proposed zoning operation strategy can achieve good system efficiency and excellent system reliability compared to the conventional strategy.
基金Supported by Tianjin Scientific Development Foundation (No.013112811-1) .
文摘A simplified numerical model of heat transfer characteristics of horizontal ground heat exchanger (GHE) in the frozen soil layer is presented and the steady-state distribution of temperature field is simulated. Numerical results show that the frozen depth mainly depends on the soil′s moisture content and ambient temperature. The heat transfer loss of horizontal GHE tends to grow with the increase of the soil′s moisture content and the decrease of ambient temperature. Backfilled materials with optimal thermal conductivity can reduce the thermal loss effectively in the frozen soil. The applicability of the Chinese national standard “Technical Code for Ground Source Heat Pump (GB 50366-2005)” is verified. For a ground source heat pump project, the feasible layout of horizontal GHE should be determined based on the integration of the soil′s structure, backfilled materials, weather data, and economic analysis.
