To study active heat insulation roadway in high temperature mines,the typical high temperature roadway of−965 m in Zhujidong Coal Mine of Anhui,China,is selected as prototype.The ANSYS numerical simulation method is u...To study active heat insulation roadway in high temperature mines,the typical high temperature roadway of−965 m in Zhujidong Coal Mine of Anhui,China,is selected as prototype.The ANSYS numerical simulation method is used for sensitivity analysis of heat insulation layer with different thermal conductivity and thickness,as well as surrounding rock with different thermal conductivity and temperature on a heat-adjusting zone radius,surrounding rock temperature field and wall temperature.The results show that the heat-adjusting zone radius will entirely be in the right power index relationship to the ventilation time.Decrease in thermal conductivity and increase in thickness of insulation layer can effectively reduce the disturbance of airflow on the surrounding rock temperature,hence,beneficial for decreasing wall temperature.This favourable trend significantly decreases with ventilation time,increase in thermal conductivity and temperature of surrounding rock,heat-adjusting zone radius,surrounding rock temperature field,and wall temperature.Sensitivity analysis shows that the thermal physical properties of surrounding rock determine the temperature distribution of the roadway,hence,temperature of surrounding rock is considered as the most sensitive factor of all influencing factors.For the spray layer,thermal conductivity is more sensitive,compared to thickness.It is concluded that increase in the spray layer thickness is not as beneficial as using low thermal conductivity insulation material.Therefore,roadway preferential consideration should be given to the rocks with low temperature and thermal conductivity.The application of the insulation layer has positive significance for the thermal environment control in mine roadway,however,increase in the layer thickness without restriction has a limited effect on the thermal insulation.展开更多
When a historic façade needs to be preserved or when the seismic considerations favor use of a concrete wall system and fire considerations limit exterior thermal insulation,one needs to use interior thermal insu...When a historic façade needs to be preserved or when the seismic considerations favor use of a concrete wall system and fire considerations limit exterior thermal insulation,one needs to use interior thermal insulation systems.Interior thermal insulation systems are less effective than the exterior systems and will not reduce the effect of thermal bridges.Yet they may be successfully used and,in many instances,are recommended as a complement to the exterior insulation.This paper presents one of these cases.It is focused on the most successful applications of capillary active,dynamic interior thermal insulation.This happens when such insulation is integrated with heating,cooling and ventilation,air conditioning(HVAC)system.Starting with a pioneering work of the Technical University in Dresden in development of capillary active interior insulations,we propose a next generation,namely,a bio-fiber thermal insulation.When completing the review,this paper proposes a concept of a joint research project to be undertaken by partners from the US(where improvement of indoor climate in exposed coastal areas is needed),China(indoor climate in non-air conditioned concrete buildings is an issue),and Germany(where the bio-fiber technology has been developed).展开更多
Utilization of high temperature cooling sources or natural energy sources can potentially contribute to improving energy efficiency in buildings.In this study,a dual-cavity window with gravity-driven cooling mechanism...Utilization of high temperature cooling sources or natural energy sources can potentially contribute to improving energy efficiency in buildings.In this study,a dual-cavity window with gravity-driven cooling mechanism(GDC window)was proposed to integrate the low-grade cooling sources into the glazing system for improving the thermal performance of the window.The embedded pipes circulated with low-grade cooling water are the key component of GDC window,which can remove the absorbed solar heat and reduce the heat gain through the window.A numerical model based on CFD simulation was developed to analyze the flow characteristic and heat transfer within the GDC window.Model validation was conducted by comparing the simulation results with measurement data obtained from previous study.Numerical simulations were carried out to compare the thermal performance of GDC window with that of conventional blinds window.Sensitivity analysis was performed to evaluate the influence of some design parameters on the flow characteristic and thermal performance of GDC window.The simulated results show that compared with the blinds window,the GDC window reduces 57.4%and 40.4% of heat gain in summer for the low-grade cooling water of 18℃ and 25℃;respectively.Reducing the flow resistance within the GDC window is significant for improving the heat removal performance of the embedded pipes.This study provides an alternative solution to integrate the low-grade cooling sources into the glazing system for enhancing the energy-efficiency and decreasing the building energy demand in cooling-dominated buildings.展开更多
The high-frequency pulse tube cryocooler(HPTC)has been attracting increasing and widespread attention in the field of cryogenic technology because of its compact structure,low vibration,and reliable operation.The gas-...The high-frequency pulse tube cryocooler(HPTC)has been attracting increasing and widespread attention in the field of cryogenic technology because of its compact structure,low vibration,and reliable operation.The gas-coupled HPTC,driven by a single compressor,is currently the simplest and most compact structure.For HPTCs operating below 20 K,in order to obtain the mW cooling capacity,hundreds or even thousands of watts of electrical power are consumed,where radiation heat leakage accounts for a large proportion of their cooling capacity.In this paper,based on SAGE10,a HPTC heat radiation calculation model was first established to study the effects of radiation heat leakage on apparent performance parameters(such as temperature and cooling capacity),and internal parameters(such as enthalpy flow and gas distribution)of the gas-coupled HPTC.An active thermal insulation method of cascade utilization of the cold energy of the system was proposed for the gas-coupled HPTC.Numerical simulations indicate that the reduction of external radiation heat leakage cannot only directly increase the net cooling power,but also decrease the internal gross losses and increase the mass and acoustic power in the lower-temperature section,which further enhances the refrigeration performance.The numerical calculation results were verified by experiments,and the test results showed that the no-load temperature of the developed cryocooler prototype decreased from 15.1 K to 6.4 K,and the relative Carnot efficiency at 15.5 K increased from 0.029%to 0.996%when substituting the proposed active method for the traditional passive method with multi-layer thermal insulation materials.展开更多
基金This work was supported by the National Natural Science Foundation of China(51774011)Funding Project of Anhui University of Science and Technology(QN2019115)Introduced Research Funding of Anhui University of Science and Technology(13190022).
文摘To study active heat insulation roadway in high temperature mines,the typical high temperature roadway of−965 m in Zhujidong Coal Mine of Anhui,China,is selected as prototype.The ANSYS numerical simulation method is used for sensitivity analysis of heat insulation layer with different thermal conductivity and thickness,as well as surrounding rock with different thermal conductivity and temperature on a heat-adjusting zone radius,surrounding rock temperature field and wall temperature.The results show that the heat-adjusting zone radius will entirely be in the right power index relationship to the ventilation time.Decrease in thermal conductivity and increase in thickness of insulation layer can effectively reduce the disturbance of airflow on the surrounding rock temperature,hence,beneficial for decreasing wall temperature.This favourable trend significantly decreases with ventilation time,increase in thermal conductivity and temperature of surrounding rock,heat-adjusting zone radius,surrounding rock temperature field,and wall temperature.Sensitivity analysis shows that the thermal physical properties of surrounding rock determine the temperature distribution of the roadway,hence,temperature of surrounding rock is considered as the most sensitive factor of all influencing factors.For the spray layer,thermal conductivity is more sensitive,compared to thickness.It is concluded that increase in the spray layer thickness is not as beneficial as using low thermal conductivity insulation material.Therefore,roadway preferential consideration should be given to the rocks with low temperature and thermal conductivity.The application of the insulation layer has positive significance for the thermal environment control in mine roadway,however,increase in the layer thickness without restriction has a limited effect on the thermal insulation.
文摘When a historic façade needs to be preserved or when the seismic considerations favor use of a concrete wall system and fire considerations limit exterior thermal insulation,one needs to use interior thermal insulation systems.Interior thermal insulation systems are less effective than the exterior systems and will not reduce the effect of thermal bridges.Yet they may be successfully used and,in many instances,are recommended as a complement to the exterior insulation.This paper presents one of these cases.It is focused on the most successful applications of capillary active,dynamic interior thermal insulation.This happens when such insulation is integrated with heating,cooling and ventilation,air conditioning(HVAC)system.Starting with a pioneering work of the Technical University in Dresden in development of capillary active interior insulations,we propose a next generation,namely,a bio-fiber thermal insulation.When completing the review,this paper proposes a concept of a joint research project to be undertaken by partners from the US(where improvement of indoor climate in exposed coastal areas is needed),China(indoor climate in non-air conditioned concrete buildings is an issue),and Germany(where the bio-fiber technology has been developed).
基金This research has received the support from the National Natural Science Foundation of China(No.51808239)the Hong Kong Scholars Program(No.XJ2019044).
文摘Utilization of high temperature cooling sources or natural energy sources can potentially contribute to improving energy efficiency in buildings.In this study,a dual-cavity window with gravity-driven cooling mechanism(GDC window)was proposed to integrate the low-grade cooling sources into the glazing system for improving the thermal performance of the window.The embedded pipes circulated with low-grade cooling water are the key component of GDC window,which can remove the absorbed solar heat and reduce the heat gain through the window.A numerical model based on CFD simulation was developed to analyze the flow characteristic and heat transfer within the GDC window.Model validation was conducted by comparing the simulation results with measurement data obtained from previous study.Numerical simulations were carried out to compare the thermal performance of GDC window with that of conventional blinds window.Sensitivity analysis was performed to evaluate the influence of some design parameters on the flow characteristic and thermal performance of GDC window.The simulated results show that compared with the blinds window,the GDC window reduces 57.4%and 40.4% of heat gain in summer for the low-grade cooling water of 18℃ and 25℃;respectively.Reducing the flow resistance within the GDC window is significant for improving the heat removal performance of the embedded pipes.This study provides an alternative solution to integrate the low-grade cooling sources into the glazing system for enhancing the energy-efficiency and decreasing the building energy demand in cooling-dominated buildings.
基金This work was supported by the National Key R&D Program of China(Grant No.2018Y FB0504603)the National Natural Science Foundation of China(Grant No.U1831203)+2 种基金the Strategic Pilot Projects in Space Science of China(Grant No.XDA15010400)the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(Grant No.QYZDY-SSW-JSC028)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2019030).
文摘The high-frequency pulse tube cryocooler(HPTC)has been attracting increasing and widespread attention in the field of cryogenic technology because of its compact structure,low vibration,and reliable operation.The gas-coupled HPTC,driven by a single compressor,is currently the simplest and most compact structure.For HPTCs operating below 20 K,in order to obtain the mW cooling capacity,hundreds or even thousands of watts of electrical power are consumed,where radiation heat leakage accounts for a large proportion of their cooling capacity.In this paper,based on SAGE10,a HPTC heat radiation calculation model was first established to study the effects of radiation heat leakage on apparent performance parameters(such as temperature and cooling capacity),and internal parameters(such as enthalpy flow and gas distribution)of the gas-coupled HPTC.An active thermal insulation method of cascade utilization of the cold energy of the system was proposed for the gas-coupled HPTC.Numerical simulations indicate that the reduction of external radiation heat leakage cannot only directly increase the net cooling power,but also decrease the internal gross losses and increase the mass and acoustic power in the lower-temperature section,which further enhances the refrigeration performance.The numerical calculation results were verified by experiments,and the test results showed that the no-load temperature of the developed cryocooler prototype decreased from 15.1 K to 6.4 K,and the relative Carnot efficiency at 15.5 K increased from 0.029%to 0.996%when substituting the proposed active method for the traditional passive method with multi-layer thermal insulation materials.
