Ground source heat pump systems demonstrate significant potential for northern rural heating applications;however,the effectiveness of these systems is often limited by challenging geological conditions.For instance,i...Ground source heat pump systems demonstrate significant potential for northern rural heating applications;however,the effectiveness of these systems is often limited by challenging geological conditions.For instance,in certain regions,the installation of buried pipes for heat exchangers may be complicated,and these pipes may not always serve as efficient low-temperature heat sources for the heat pumps of the system.To address this issue,the current study explored the use of solar-energy-collecting equipment to supplement buried pipes.In this design,both solar energy and geothermal energy provide low-temperature heat to the heat pump.First,a simulation model of a solar‒ground source heat pump coupling system was established using TRNSYS.The accuracy of this model was validated through experiments and simulations on various system configurations,including varying numbers of buried pipes,different areas of solar collectors,and varying volumes of water tanks.The simulations examined the coupling characteristics of these components and their influence on system performance.The results revealed that the operating parameters of the system remained consistent across the following configurations:three buried pipes,burial depth of 20 m,collector area of 6 m^(2),and water tank volume of 0.5 m^(3);four buried pipes,burial depth of 20 m,collector area of 3 m^(2),and water tank volume of 0.5 m^(3);and five buried pipes with a burial depth of 20 m.Furthermore,the heat collection capacity of the solar collectors spanning an area of 3 m^(2)was found to be equivalent to that of one buried pipe.Moreover,the findings revealed that the solar‒ground source heat pump coupling system demonstrated a lower annual cumulative energy consumption compared to the ground source heat pump system,presenting a reduction of 5.31%compared to the energy consumption of the latter.展开更多
The numeric al simulation study on the temperature distribution of underground field for the ground coupled heat pump (GCHP) with vertical spira l coil was carried out by using finite element. The distribution and rec...The numeric al simulation study on the temperature distribution of underground field for the ground coupled heat pump (GCHP) with vertical spira l coil was carried out by using finite element. The distribution and recovery of undergroun d field temperature under different operation ratio and the optimal operation ratio were simulated.The performance parameters, i.e. inlet and outlet temperature of the ground spiral coil in heating and cooling modes were tested, the heat extracted or emitted by the heat pump to the ground was calculated, and the coefficients of performance (COP) of GCHP at heat ing and cooling modes were analyzed.展开更多
Aiming to give some advices on the ground coupled heat pump system design in Siehuan Province, China, a typical ground source heat pump （GSHP） system in Sichuan Province was tested in a whole operational year, and t...Aiming to give some advices on the ground coupled heat pump system design in Siehuan Province, China, a typical ground source heat pump （GSHP） system in Sichuan Province was tested in a whole operational year, and the parameters of temperature and flow rate in different parts of system were measured during this period. The seasonal energy efficiency ratio was calculated and the performance of heat pump system in summer was compared with that in winter. The result shows that the coefficient of performance of the system reaches 3.63 in summer and 3.49 in winter, respectively. The heat balance in underground rock mass is acquired basically throughout the year, and the heat accumulation in the earth tends to be zero.展开更多
Electric field measurement holds immense significance in various domains.The power supply and signal acquisition units of the sensor may be coupled with ground wire interference,which could result in reduced measureme...Electric field measurement holds immense significance in various domains.The power supply and signal acquisition units of the sensor may be coupled with ground wire interference,which could result in reduced measurement accuracy.Moreover,this problem is often ignored by researchers.This paper investigated the origin of ground coupling interference in electric field sensors and its impact on measurement accuracy.A miniature undistorted electric field sensor with wireless transmission was compared with existing D-dot,microelectromechanical systems(MEMS),and optical sensors.The results indicate that MEMS and D-dot exhibit diminished accuracy in measuring electric fields under uniform conditions,owing to interference from ground wires.In the case of transmission lines with non-uniform conditions,the wireless sensor exhibited a measurement error of 5%,whereas the optical sensor showed an error rate of approximately 8%.However,the D-dot sensor displayed a measurement error exceeding 50%,whereas the MEMS sensor yielded an error as high as 150%.This means that the wireless sensor isolates the ground-coupled interference signal and realizes the distortion-free measurement of the electric field.The wireless sensors will find extensive applications in new power systems for intelligent equipment status perception,fault warning,and other scenarios.展开更多
Calculating the parameters of the ground shock induced by an underground explosion is a complex energy coupling problem.It is difficult to establish a unified ground shock coupling law from limited test data.This pape...Calculating the parameters of the ground shock induced by an underground explosion is a complex energy coupling problem.It is difficult to establish a unified ground shock coupling law from limited test data.This paper summarizes the research results obtained at home and abroad and systematically analyzes the coupling mechanism of craters formed by an underground explosion and the ground shock.The differences between the concepts of"closed-explosion critical depth"and"equivalent closed-explosion critical depth"are clearly explained.The spreading of the ground shock energy is attributed to the explosive expansion of the air cavity,revealing a linear relationship between the volume of the cavity region(or the volume of the crack region)and the ground shock energy associated with the underground explosion.The proportionality factor is related to the mechanical properties of the medium and is independent of the magnitude of the explosion equivalent.Based on this,a theoretical calculation formula and conversion method for the ground shock coupling coefficient were established.Explosion tests were conducted in clay and Plexiglass under varying burial depths.The test results were consistent with the theoretically calculated results.Our study provides a theoretical basis for the design of explosion-resistant structures in underground engineering.展开更多
Deep geothermal heat exchangers(DGHEs)have emerged as a potential approach to exploiting geothermal energy as a stable high-temperature heat source for ground-coupled heat pumps.This study aimed to offer insights into...Deep geothermal heat exchangers(DGHEs)have emerged as a potential approach to exploiting geothermal energy as a stable high-temperature heat source for ground-coupled heat pumps.This study aimed to offer insights into the heat transfer of DGHEs by systematic numerical simulations.This study first created a finite-volume model(FVM)for the heat transfer of DGHEs,which uses the governing equations of circulating fluid inside the borehole as a time-varying boundary condition for the borehole wall.The FVM model was verified by comparison with several reported models.The heat transfer analysis emphasized the validity of the homogeneous-medium assumption about the ground and the time-varying characteristics of the heat flux on the borehole wall.The homogeneous-medium assumption seems to be only acceptable in cases of limited thermal conductivity differences between the ground layers(e.g.,<2.0 W/m·K).Not only the heat flux on the borehole wall varies linearly with borehole depth,but the slope and the interception of the line are linear functions of the logarithm of time.展开更多
基金supported by 2024 Central Guidance Local Science and Technology Development Fund Project"Study on the mechanism and evaluation method of thermal pollution in water bodies,as well as research on thermal carrying capacity".(Grant 246Z4506G)Key Research and Development Project in Hebei Province:"Key Technologies and Equipment Research and Demonstration of Multiple Energy Complementary(Electricity,Heat,Cold System)for Solar Energy,Geothermal Energy,Phase Change Energy"(Grant 236Z4310G)the Hebei Academy of Sciences Key Research and Development Program"Research on Heat Transfer Mechanisms and Efficient Applications of Intermediate and Deep Geothermal Energy"(22702)。
文摘Ground source heat pump systems demonstrate significant potential for northern rural heating applications;however,the effectiveness of these systems is often limited by challenging geological conditions.For instance,in certain regions,the installation of buried pipes for heat exchangers may be complicated,and these pipes may not always serve as efficient low-temperature heat sources for the heat pumps of the system.To address this issue,the current study explored the use of solar-energy-collecting equipment to supplement buried pipes.In this design,both solar energy and geothermal energy provide low-temperature heat to the heat pump.First,a simulation model of a solar‒ground source heat pump coupling system was established using TRNSYS.The accuracy of this model was validated through experiments and simulations on various system configurations,including varying numbers of buried pipes,different areas of solar collectors,and varying volumes of water tanks.The simulations examined the coupling characteristics of these components and their influence on system performance.The results revealed that the operating parameters of the system remained consistent across the following configurations:three buried pipes,burial depth of 20 m,collector area of 6 m^(2),and water tank volume of 0.5 m^(3);four buried pipes,burial depth of 20 m,collector area of 3 m^(2),and water tank volume of 0.5 m^(3);and five buried pipes with a burial depth of 20 m.Furthermore,the heat collection capacity of the solar collectors spanning an area of 3 m^(2)was found to be equivalent to that of one buried pipe.Moreover,the findings revealed that the solar‒ground source heat pump coupling system demonstrated a lower annual cumulative energy consumption compared to the ground source heat pump system,presenting a reduction of 5.31%compared to the energy consumption of the latter.
文摘The numeric al simulation study on the temperature distribution of underground field for the ground coupled heat pump (GCHP) with vertical spira l coil was carried out by using finite element. The distribution and recovery of undergroun d field temperature under different operation ratio and the optimal operation ratio were simulated.The performance parameters, i.e. inlet and outlet temperature of the ground spiral coil in heating and cooling modes were tested, the heat extracted or emitted by the heat pump to the ground was calculated, and the coefficients of performance (COP) of GCHP at heat ing and cooling modes were analyzed.
基金Project(50838009) supported by the National Science Key Foundation 1 tem
文摘Aiming to give some advices on the ground coupled heat pump system design in Siehuan Province, China, a typical ground source heat pump （GSHP） system in Sichuan Province was tested in a whole operational year, and the parameters of temperature and flow rate in different parts of system were measured during this period. The seasonal energy efficiency ratio was calculated and the performance of heat pump system in summer was compared with that in winter. The result shows that the coefficient of performance of the system reaches 3.63 in summer and 3.49 in winter, respectively. The heat balance in underground rock mass is acquired basically throughout the year, and the heat accumulation in the earth tends to be zero.
基金supported in part by the National Key Research and Development Program of China under Grant 2022YFB3206800in part by the National Natural Science Foundation of China under Grant 52125703.
文摘Electric field measurement holds immense significance in various domains.The power supply and signal acquisition units of the sensor may be coupled with ground wire interference,which could result in reduced measurement accuracy.Moreover,this problem is often ignored by researchers.This paper investigated the origin of ground coupling interference in electric field sensors and its impact on measurement accuracy.A miniature undistorted electric field sensor with wireless transmission was compared with existing D-dot,microelectromechanical systems(MEMS),and optical sensors.The results indicate that MEMS and D-dot exhibit diminished accuracy in measuring electric fields under uniform conditions,owing to interference from ground wires.In the case of transmission lines with non-uniform conditions,the wireless sensor exhibited a measurement error of 5%,whereas the optical sensor showed an error rate of approximately 8%.However,the D-dot sensor displayed a measurement error exceeding 50%,whereas the MEMS sensor yielded an error as high as 150%.This means that the wireless sensor isolates the ground-coupled interference signal and realizes the distortion-free measurement of the electric field.The wireless sensors will find extensive applications in new power systems for intelligent equipment status perception,fault warning,and other scenarios.
基金funded by the National Natural Science Foundation of China(Grant No.52279120).
文摘Calculating the parameters of the ground shock induced by an underground explosion is a complex energy coupling problem.It is difficult to establish a unified ground shock coupling law from limited test data.This paper summarizes the research results obtained at home and abroad and systematically analyzes the coupling mechanism of craters formed by an underground explosion and the ground shock.The differences between the concepts of"closed-explosion critical depth"and"equivalent closed-explosion critical depth"are clearly explained.The spreading of the ground shock energy is attributed to the explosive expansion of the air cavity,revealing a linear relationship between the volume of the cavity region(or the volume of the crack region)and the ground shock energy associated with the underground explosion.The proportionality factor is related to the mechanical properties of the medium and is independent of the magnitude of the explosion equivalent.Based on this,a theoretical calculation formula and conversion method for the ground shock coupling coefficient were established.Explosion tests were conducted in clay and Plexiglass under varying burial depths.The test results were consistent with the theoretically calculated results.Our study provides a theoretical basis for the design of explosion-resistant structures in underground engineering.
基金supported by the Natural Science Foundation of Hunan Province(Grant Number:2022JJ30725).
文摘Deep geothermal heat exchangers(DGHEs)have emerged as a potential approach to exploiting geothermal energy as a stable high-temperature heat source for ground-coupled heat pumps.This study aimed to offer insights into the heat transfer of DGHEs by systematic numerical simulations.This study first created a finite-volume model(FVM)for the heat transfer of DGHEs,which uses the governing equations of circulating fluid inside the borehole as a time-varying boundary condition for the borehole wall.The FVM model was verified by comparison with several reported models.The heat transfer analysis emphasized the validity of the homogeneous-medium assumption about the ground and the time-varying characteristics of the heat flux on the borehole wall.The homogeneous-medium assumption seems to be only acceptable in cases of limited thermal conductivity differences between the ground layers(e.g.,<2.0 W/m·K).Not only the heat flux on the borehole wall varies linearly with borehole depth,but the slope and the interception of the line are linear functions of the logarithm of time.
