In this paper,the performance of a solar thermal system with a focus on space heating was investigated.A 70 m^(2) detached house was considered in the weather conditions of the city of Tehran,Iran.A thermosyphon solar...In this paper,the performance of a solar thermal system with a focus on space heating was investigated.A 70 m^(2) detached house was considered in the weather conditions of the city of Tehran,Iran.A thermosyphon solar water heater with a flat plate collector combined with an auxiliary electrical heater supplies the heating demand of the house.The proposed system was modeled and analyzed using TRNSYS software.In this regard,the TRNBuild module was employed for the building load calculation.The model has been simulated for one year of operation.The effects of the solar collector’s surface area and storage volume were assessed.The results show that for a solar collector with a 15 m^(2) surface area,the solar fraction is 0.29 in January,during which the solar radiation is the lowest.Using solar collectors of10 m^(2) and 5 m^(2) surface areas,the solar fraction falls to 0.23 and 0.14,respectively in January.Besides,two cases of 150 L and 300 L storage tanks are taken into account.Eventually,it is found that using a 15 m^(2) solar collector and a 150 L storage tank can appropriately provide the building’ s heating demand taking the thermal performance and economic aspects into consideration.展开更多
From the viewpoints of environmental conservation and energy efficiency,seawater-source heat pump system(SWHP) to provide district cooling and heating is applied in coastal areas.Based on the system,a heat transfer mo...From the viewpoints of environmental conservation and energy efficiency,seawater-source heat pump system(SWHP) to provide district cooling and heating is applied in coastal areas.Based on the system,a heat transfer model was established for cast heat exchanger(CHE) adopted by SWHP systems.The CHE consists of pipes immersed in the seawater and used for transferring heat between the seawater and the heat exchanger pipes of SWHP system.An experimental study was carried out to test the validity of the model.A program was developed in VB language and the effects of inlet temperature,flow rate of the secondary refrigerant and length of CHE on the results were investigated.The results of the numerical simulation are in consistence with the experiments in both winter and summer conditions.As a result,application of SWHP systems with CHE in coastal areas in China is feasible due to the favorable geographical conditions and environment.展开更多
Thermal performance is the most important factor in the development of a borehole heat exchanger utilizing geothermal energy.The thermal performance is affected by many different design parameters and different operat...Thermal performance is the most important factor in the development of a borehole heat exchanger utilizing geothermal energy.The thermal performance is affected by many different design parameters and different operating conditions such as bleeding.This eventually determines the operation and cost efficiency of the borehole heat exchanger system.The thermal performance of an open standing column well (SCW) type geothermal heat exchanger was assessed under the influence of bleeding.For this,a thermal response test rig was established with line-source theory.The test rig also had a bleeding function by releasing fluid while taking additional underground water through the heat exchanger.The thermal response test was performed with an additional constant input heat source.Effective thermal conductivity and thermal resistance were obtained from the measured data.From the measurement,the effective thermal conductivity is found to have 1.47 times higher value when bleeding is applied.The thermal resistance also increases by 1.58 times compared to a non-bleeding case.This trend indicates enhanced heat transfer in the SCW type heat exchanger with a bleeding function.Bleeding,therefore,could be an effective method of achieving a high heat transfer rate in the SCW type heat exchanger with sufficient underground water supply.展开更多
文摘In this paper,the performance of a solar thermal system with a focus on space heating was investigated.A 70 m^(2) detached house was considered in the weather conditions of the city of Tehran,Iran.A thermosyphon solar water heater with a flat plate collector combined with an auxiliary electrical heater supplies the heating demand of the house.The proposed system was modeled and analyzed using TRNSYS software.In this regard,the TRNBuild module was employed for the building load calculation.The model has been simulated for one year of operation.The effects of the solar collector’s surface area and storage volume were assessed.The results show that for a solar collector with a 15 m^(2) surface area,the solar fraction is 0.29 in January,during which the solar radiation is the lowest.Using solar collectors of10 m^(2) and 5 m^(2) surface areas,the solar fraction falls to 0.23 and 0.14,respectively in January.Besides,two cases of 150 L and 300 L storage tanks are taken into account.Eventually,it is found that using a 15 m^(2) solar collector and a 150 L storage tank can appropriately provide the building’ s heating demand taking the thermal performance and economic aspects into consideration.
基金Project(2006BAJ04A15-03) supported by the National Science and Technology Pillar Program during the Eleventh Five-year Plan Period
文摘From the viewpoints of environmental conservation and energy efficiency,seawater-source heat pump system(SWHP) to provide district cooling and heating is applied in coastal areas.Based on the system,a heat transfer model was established for cast heat exchanger(CHE) adopted by SWHP systems.The CHE consists of pipes immersed in the seawater and used for transferring heat between the seawater and the heat exchanger pipes of SWHP system.An experimental study was carried out to test the validity of the model.A program was developed in VB language and the effects of inlet temperature,flow rate of the secondary refrigerant and length of CHE on the results were investigated.The results of the numerical simulation are in consistence with the experiments in both winter and summer conditions.As a result,application of SWHP systems with CHE in coastal areas in China is feasible due to the favorable geographical conditions and environment.
基金Project supported by the Second Stage of Brain Korea 21 Projects and Changwon National University in2011-2012
文摘Thermal performance is the most important factor in the development of a borehole heat exchanger utilizing geothermal energy.The thermal performance is affected by many different design parameters and different operating conditions such as bleeding.This eventually determines the operation and cost efficiency of the borehole heat exchanger system.The thermal performance of an open standing column well (SCW) type geothermal heat exchanger was assessed under the influence of bleeding.For this,a thermal response test rig was established with line-source theory.The test rig also had a bleeding function by releasing fluid while taking additional underground water through the heat exchanger.The thermal response test was performed with an additional constant input heat source.Effective thermal conductivity and thermal resistance were obtained from the measured data.From the measurement,the effective thermal conductivity is found to have 1.47 times higher value when bleeding is applied.The thermal resistance also increases by 1.58 times compared to a non-bleeding case.This trend indicates enhanced heat transfer in the SCW type heat exchanger with a bleeding function.Bleeding,therefore,could be an effective method of achieving a high heat transfer rate in the SCW type heat exchanger with sufficient underground water supply.
