A new ground source heat pump system combined with radiant heating/cooling is proposed, and the principles and the advantages of the system are analyzed. A demonstration of the system is applied to a rebuilt building...A new ground source heat pump system combined with radiant heating/cooling is proposed, and the principles and the advantages of the system are analyzed. A demonstration of the system is applied to a rebuilt building： Xijindu exhibition hall, which is located in Zhenjiang city in China. Numerical studies on the thermal comfort and energy consumption of the system are carded out by using TRNSYS software. The results indicate that the system with the radiant floor method or the radiant ceiling method shows good thermal comfort without mechanical ventilation in winter. However, the system with either of the methods should add mechanical ventilation to ensure good comfort in summer. At the same level of thermal comfort, it can also be found that the annual energy consumption of the radiant ceiling system is less than that of the radiant floor system.展开更多
The utilization of prefabricated light modular radiant heating system has demonstrated significant increases in heat transfer efficiency and energy conservation capabilities.Within prefabricated building construction,...The utilization of prefabricated light modular radiant heating system has demonstrated significant increases in heat transfer efficiency and energy conservation capabilities.Within prefabricated building construction,this new heating method presents an opportunity for the development of comprehensive facilities.The parameters for evaluating the effectiveness of such a system are the upper surface layer’s heat flux and temperature.In this paper,thermal resistance analysis calculation based on a simplified model for this unique radiant heating system analysis is presented with the heat transfer mechanism’s evaluation.The results obtained from thermal resistance analysis calculation and numerical simulation indicate that the thermal resistance analysis method is highly accurate with temperature discrepancies ranging from 0.44℃ to−0.44℃ and a heat flux discrepancy of less than 7.54%,which can meet the requirements of practical engineering applications,suggesting a foundation for the prefabricated radiant heating system.展开更多
In order to have an in-depth understanding of the metal ceiling radiant panel with capillary tubes, a radiant ceiling heating system is constructed to study the actual heating performance and thermal comfort by experi...In order to have an in-depth understanding of the metal ceiling radiant panel with capillary tubes, a radiant ceiling heating system is constructed to study the actual heating performance and thermal comfort by experiments. In addition, the energy saving potential of the novel heating system is discussed in terms of the COP （coefficient of performance） of the ground source heat pump and the exergy efficiency of the radiant terminal. The results indicate that the heating system shows high thermal stability and thermal comfort. When the system reaches a stable condition, the radiant heat transfer accounts for 62.7% of the total heat transfer, and the total heat transfer can meet the heating demands of most buildings. Compared to a radiant floor heating system, it offers advantages in a shorter preheating time, a lower supply water temperature and a stronger heating capability. The COP of the ground source heat pump is increased greatly when the supply water temperature is 28 to 33 ℃, and the exergy efficiency of the metal ceiling with capillary tubes is 1.6 times that of the radiant floor when the reference temperature is 5 ℃ The novel radiant ceiling heating system shows a tremendous energy saving potential.展开更多
To evaluate the thermal performance of a low-temperature electrical radiant floor heating system,an experimental facility equipped with a constant temperature chamber and different specimen floors is designed and buil...To evaluate the thermal performance of a low-temperature electrical radiant floor heating system,an experimental facility equipped with a constant temperature chamber and different specimen floors is designed and built.The heating cable is installed in the floor slab with a unit-rated power of 30 W/m.Twenty-four different schemes are worked out and tested,which include three kinds of composite floor structures and eight kinds of cable distances.The cable distances are 30,40,50,60,80,100,130,150 mm.The main affective factors of the thermal performance and their influencing regularity are discussed.The experimental results show that the system has good stability and reliability,and the ratio of the radiation heat-transfer rate to the gross heat-transfer rate is greater than 50%.When the floor structure and the cable distance are fixed,the gross heat-transfer rate of the upper floor surface has a maximum value at an optimal cable distance.Under the experimental conditions in this paper,the optimal cable distance is 50 mm.展开更多
Hydronic heating and cooling systems are considered the most efficient, greenest technology known to man for the efficient distribution of warmth and cooling;in other words, the ideal human comfort experience. For peo...Hydronic heating and cooling systems are considered the most efficient, greenest technology known to man for the efficient distribution of warmth and cooling;in other words, the ideal human comfort experience. For people who may not know what hydronics are, here’s the definition: Hydronics: A means of transferring the energy required for heating and cooling buildings utilizing water as the primary medium in an effort to maintain good human comfort and conserve energy resources. And while we are in definition mode, allow me to introduce a couple of other terms that are critically important. Comfort: My definition of comfort is being in a state of wellbeing, or not being aware of your surroundings. In this state, you are not hot, nor are you cold. Your sinuses are not too dry, nor is it too humid, and there is not a lot of noise in the background associated with the delivery of comfort. In short, if you have to think about your physical condition, you are probably not comfortable. Simply stated, if you are truly comfortable, you will not be thinking about it. Mean Radiant Temperature: Mean radiant temperature, or MRT for short, is one of those things that cannot (normally) be seen by the bare human eye, but is the primary dictator of excellent human comfort. By definition, MRT is the temperature of those solid items surrounding your body. When the MRT is high, human comfort is achieved with a lower air temperature. When the air temperature is high, good human comfort is achieved with a lower MRT. MRT can be seen using an infrared camera, but most people do not have access to this wonderful technology. Before I go into my dissertation, I want to quickly dispel a myth. People have been taught over the years that “heat rises.” This statement in and of itself is incorrect. Hot fluids rise. Hot air or hot water rise because of their differences in buoyancy compared to cooler surrounding fluids. Radiant energy travels in all directions, through the path of least resistance, including in a downward direction. The best explanation for comparison purposes is to think of being outside on a cool winter day when the sun is shining brightly and you are standing next to a dark colored wall. Your body can sense the radiant energy surrounding your body, and your body feels warmer than it really is due to this exposure to a higher MRT. Another prime example is sitting next to a campfire on a clear starlit night. Even though the ambient air temperature is low, your body can feel the radiation coming from the fire, and it feels warm and comforting on the side that is facing the fire. Your backside that is not facing the fire feels much cooler than the side that is facing the fire, so we rotate in an effort to even out this radiant exposure. If radiant energy only traveled upward, as in “heat rises,” we would have to stand on top of the sun in order to realize any comfort due to radiant energy. As was already proved in our previous statement about MRT, such is not the case. Controlling heat loss from our bodies by manipulating the MRT will guarantee that most people will be comfortable under all conditions. As can be seen from the above graphic, radiational losses account for nearly half of the human body’s heat loss.展开更多
The radiative heat flux of the plume from reusable rockets is a critical parameter during the launch and return processes.This paper proposes a method for calculating radiative heat flux with higher accuracy than prev...The radiative heat flux of the plume from reusable rockets is a critical parameter during the launch and return processes.This paper proposes a method for calculating radiative heat flux with higher accuracy than previously reported for a recoverable nine-engine liquid-propellant rocket.Based on the Radiative Transfer Equation(RTE),this study employs the discrete transfer method to solve the transient RTE problem using physical properties to describe the problem while avoiding the need to directly solve mathematical equations.The proposed method can effectively determine the radiative heat flux of the flow field and is applicable to problems involving various geometries.Calculations reveal that during the ascent phase of the rocket,the radiative heat flux at the base of the vehicle reaches its maximum in the initial stages of the lift-off,reaching a maximum of~50 kW/m^(2),which is 2.24 times the maximum value during the return phase.During the deceleration stage of re-entry into the atmosphere,the maximum radiative heat flux recorded on the sidewall of the rocket is 29.1 kW/m^(2);the maximum heat flux on the bottom surface is approximately 22.3 kW/m^(2),accounting for 76.6%of that on the rocket's sidewall.This provides a basis for the thermal protection design of the rocket's bottom and walls as well as for the thermal management of cryogenic propellant tanks.Future research will involve ground engine testing and flight experiments to further validate the proposed model.展开更多
Building energy consumption is mainly influenced by thermal load,equipment efficiency,service space,and operating time.While extensive research has focused on reducing load and improving efficiency,significant energy-...Building energy consumption is mainly influenced by thermal load,equipment efficiency,service space,and operating time.While extensive research has focused on reducing load and improving efficiency,significant energy-saving potential remains in optimizing time and space of usage.This study proposes a novel convective-radiant desktop-based terminal that integrates personalized environmental control system with convective-radiant terminals,enabling“part-time,localized-space”operations to enhance energy savings.It includes a discussion on the structural design of the device and experimental analysis of its local environmental control and intermittent operation.The design incorporates a convective heat exchanger and radiant panel embedded in a height-adjustable desktop.Experimental results showed that the combination of the radiant panel and air outlet beneath the desktop accumulates heat in this area during heating,creating a“cool head,warm feet”thermal comfort effect.The maximum vertical temperature difference was 0.7℃ in radiation mode.For intermittent operation,the temperature response matching coefficient(TRMC)of the proposed terminal was 3.4 times that of floor heating and 2.1 times that of fan coil units,indicating superior performance.Besides,this novel terminal provides effective thermal comfort in both sitting and standing positions,offering potential energy savings in open-plan offices.By extending the room temperature setpoint to 16–18℃ in winter,the terminal can reduce energy consumption by 3.64%–12.52%.These findings provide a reference for personalized environmental control systems and intermittent heating strategies.展开更多
This paper presents a comprehensive experimental and numerical investigation of radiant floor heating(RFH)systems integrated with phase changematerial(PCM)-based thermal energy storage(TES).The study compares two unde...This paper presents a comprehensive experimental and numerical investigation of radiant floor heating(RFH)systems integrated with phase changematerial(PCM)-based thermal energy storage(TES).The study compares two underfloor pipe configurations:double serpentine and spiral.It also looks at how well a paraffin wax PCM system works with compact heat exchanger-type TES units during winter in Iraq.Key performance indicators including discharge temperature,heat transfer rate,liquid fraction evolution,and temperature uniformity were assessed through in situ experimental measurements and ANSYS fluent simulations.Results demonstrate that the spiral design provides slightly more uniform temperature distribution on the tile surface at an inlet water temperature of 55℃,with an average difference of approximately 0.5%,the serpentine layout exhibits higher slab temperature distribution by about 0.66%.Notably,the serpentine configuration shows superior thermal homogeneity and heat distribution,with a 15.05%increase in heat gain at a 55℃ inlet temperature compared to the spiral design.The performance gap between the two layouts narrows as the inlet temperature increases from 50℃ in 5℃ increments by approximately 4.1%,3.7%,and 1.7%,respectively.Higher inlet temperatures also improve PCM discharging and charging rates,improving energy storage utilization.The findings provide significant design guidelines for sustainable heating systems for cold climates.展开更多
This paper proposes two new radiant floor heating structures based on micro heat pipe array(MHPA),namely cement-tile floor and keel-wood floor.The numerical models for these different floor structures are established ...This paper proposes two new radiant floor heating structures based on micro heat pipe array(MHPA),namely cement-tile floor and keel-wood floor.The numerical models for these different floor structures are established and verified by experiments.The temperature distribution and heat transfer process of each part are comprehensively obtained,and the structure is optimized.The results show that the cement-tile floor has the better heat transfer performance of the two.When under the same inlet water temperature and flow rate,the keel-wood floor's surface temperature distribution is about 2℃ lower than that of the cement-tile floor.The inlet water temperature of cement-tile floor is about 10℃ lower than that of keel-wood structure when the floor surface temperature is the same.During a longitudinal heat transfer above MHPA,the floor surface temperature decreases by 0.5℃ for every 10 mm filling layer increase.In order to reduce the non-uniformity of the floor's surface temperature and improve the thermal comfort of the heated room,the optimal structure for a floor is given,with the maximum surface temperature difference reduced by 3.35℃.We used research focusing on new radiant floor heating,with advantages including high efficiency heat transfer,low water supply temperature,simple waterway structure,low resistance and leakage risk,to provide theory and data to support the application of an effective radiant floor heating based on MHPA.展开更多
In the building with many transparent envelopes,solar radiation can irradiate on the local surface of floor and cause overheating.The local thermal comfort in the room will be dissatisfactory and the thermal performan...In the building with many transparent envelopes,solar radiation can irradiate on the local surface of floor and cause overheating.The local thermal comfort in the room will be dissatisfactory and the thermal performance of radiant floor will be strongly affected.However,in many current calculation models,solar radiation on the floor surface is assumed to be uniformly distributed,resulting in the inaccurate evaluation of the thermal performance of the radiant floor.In this paper,a calculation model based on the theory of discretization and the RC thermal network is proposed to calculate the dynamic thermal performance of radiant floor with the consideration of unevenly distributed solar radiation.Then,the discretization model is experimentally validated and is used to simulate a radiant floor heating system of an office room in Lhasa.It is found that with the unevenly distributed solar radiation,the maximum surface temperature near the south exterior window can reach up to 35.6℃,which exceeds the comfort temperature limit and is nearly 8.5℃higher than that in the north zone.Meanwhile,the heating capacity of the radiant floor in the irradiated zone can reach up to 171 W/m^(2),while that in the shaded zone is only 79 W/m^(2).The model with the assumption of uniformly distributed solar radiation ignores the differences between the south and north zones and fails to describe local overheating in the irradiated zones.By contrast,the discretization model can more accurately evaluate the thermal performance of radiant floor with the influence of real solar radiation.Based on this discretization model,novel design and control schemes of radiant floor heating system can be proposed to alleviate local overheating and reduce heating capacity in the irradiated zone.展开更多
As one of the core components of aero-engine,the thermal protection scheme of combustion chamber has an important impact on its service life.In order to improve the design level of high-performance combustion chamber,...As one of the core components of aero-engine,the thermal protection scheme of combustion chamber has an important impact on its service life.In order to improve the design level of high-performance combustion chamber,the radiation heat transfer characteristics of combustion chamber are studied by experimental method.The following results are obtained:1)With the increase of oil-gas ratio,the gas temperature increases first and then tends to be stable,the radiant heat flow increases gradually,the convective heat flow increases gradually and then tends to be stable,and the proportion of radiant heat flow remains basically unchanged;2)With the increase of the inlet temperature,the gas temperature increases gradually,the radiant heat flow,especially in the flame barrel head area,increases significantly,the convective heat flow remains basically unchanged,and the proportion of radiant heat flow increases significantly;3)With the increase of the combustion chamber pressure,the gas temperature increases gradually.When the combustion chamber pressure is low,the radiant heat flow increases sharply with the increase of the pressure;When the combustion chamber pressure is high,the radiant heat flow increases slowly with the increase of the pressure.The convective heat flow gradually decreases and tends to be stable,and the proportion of radiant heat flow gradually increases and tends to be stable.This study is of great significance to improve the calculation accuracy of radiant heat flow of combustion chamber and the reliability design of thermal protection scheme of combustion chamber.展开更多
Far infrared(FIR)radiation(3-100µm)is an electromagnetic spectrum commonly studied for biological effects.This article aims to discuss using Far infrared radiation with sub-division(4-24µm)of this waveband t...Far infrared(FIR)radiation(3-100µm)is an electromagnetic spectrum commonly studied for biological effects.This article aims to discuss using Far infrared radiation with sub-division(4-24µm)of this waveband to stimulate tissues and cells and is considered an effective therapeutic modality for specific medical disorders.The IR application as a medical therapy has advanced rapidly in recent years.For example,IR therapy like IR-emitting apparel and materials that can be run solely by body heat(does not need an external power supply)have been developed.New methods for providing FIR radiation to the human body have emerged due to technological advancements.Specialty saunas and lamps that emit pure FIR radiation have become effective,safe,and widely used therapeutic sources.Fibers infused with thermide,FIR emitting ceramic nanomaterials and knitted into fabrics are used as clothes and apparel to produce FIR radiation and benefit from its effects.A deeper understanding of FIR's significant innovations and biological implications could aid in improving therapeutic efficacy or developing new methods that use FIR wavelengths.展开更多
The effect of pressure on combustion and heat transfer is analyzed. The research is based on the basic combustion and heat transfer theorem. A correction for the heat calculation method for pressurized furnace is made...The effect of pressure on combustion and heat transfer is analyzed. The research is based on the basic combustion and heat transfer theorem. A correction for the heat calculation method for pressurized furnace is made on the basis of the normal pressure case. The correction takes the effect of pressurizing into account. The results show that the correction is reasonable and the method is applicable to combustion and heat transfer of the marine supercharged boiler.展开更多
Flame heat transfer blockage occurs as fuel vapors, soot and products of combustion near a burning fuel surface block much of the heat feedbacks （including external radiative heat flux） to the fuel surface of a burn...Flame heat transfer blockage occurs as fuel vapors, soot and products of combustion near a burning fuel surface block much of the heat feedbacks （including external radiative heat flux） to the fuel surface of a burning object. Blockage clearly affects burning rates and heat release rates of fires. This needs to be included when calculating flame heat transfer in fire growth models. An understanding of bttrning of materials in small scale fires is of broad and vital importance for predicting their burning performance in large scale fires. The blockage phenomenon was clearly observed and quantitatively measured in experiments that took advantage of the unique capability of the Fire Propagation Apparatus （FPA） of being able to vary the ambient oxygen concentrations. An indirect measurement approach was established which provides an experimental understanding of the concept of the blockage. The measurements were further explained by a one-dimensional steady-state model of a diffusion flame, which focuses on the radiant absorption and emission by the gas-soot mixture of flames. The theoretical model provides a greater understanding of the fundamental knowledge of the blockage. The overall heat transfer blockage factor can be up to 0.3 -0.4 for PMMA and POM. The factor and its components are nearly independent of the external radiation, but increase as the ambient oxygen concentration rises. A comparison between experimental data and model prediction shows a good agreement.展开更多
The R-value is defined as,“a measure of the resistance of an insulating or building material to heat flow,expressed as R-11,R-20,and so on;the higher the number,the greater the resistance to heat flow(Random House,20...The R-value is defined as,“a measure of the resistance of an insulating or building material to heat flow,expressed as R-11,R-20,and so on;the higher the number,the greater the resistance to heat flow(Random House,2016).”The first thermodynamic principle violated by the R-value is the singular use of the word heat flow.Heat flow,or transfer,occurs in three distinct ways;conduction,convection,and radiation.The R-value test will only measure a bulk insulations resistance to conductive heat transfer.This type of heat flow is almost undetectable in the built environment,regardless of climate or season-resulting in the R-value myth.In winter,the stack effect will cause convective flows through the home as warm air under pressure rises and escapes through the top,requiring an equal amount of cold replacement air to infiltrate at the bottom.On hot sunny days,the exterior of the home absorbs long wave ultra violet(UV)rays from the sun and reemits this radiant heat energy into the residence.The thermodynamics of an occupied structure under varying atmospheric conditions is not well understood,leading to major inefficiencies.The goal of this conceptual study is to reveal the shortcomings of current insulation practices at the residential level,conceptualize a series of related issues for future study and develop a preliminary methodological concept for resolutions to the problems identified.Conclusions indicate that further research needs to be dedicated to replacing the R-value rule with a realistic metric that considers the efficiency,health,and safety of the entire building.展开更多
基金The National Natural Science Foundation of China(No. 51036001 )the Natural Science Foundation of Jiangsu Province(No. BK2010043)
文摘A new ground source heat pump system combined with radiant heating/cooling is proposed, and the principles and the advantages of the system are analyzed. A demonstration of the system is applied to a rebuilt building： Xijindu exhibition hall, which is located in Zhenjiang city in China. Numerical studies on the thermal comfort and energy consumption of the system are carded out by using TRNSYS software. The results indicate that the system with the radiant floor method or the radiant ceiling method shows good thermal comfort without mechanical ventilation in winter. However, the system with either of the methods should add mechanical ventilation to ensure good comfort in summer. At the same level of thermal comfort, it can also be found that the annual energy consumption of the radiant ceiling system is less than that of the radiant floor system.
基金Project(NB-2020-JG-07)supported by the Research and Engineering Application of Key Technologies for New Building Industrialization Project of China Northwest Architectural Design and Research Institute Co.,Ltd.Project(2023-CXTD-29)supported by the Key Scientific and Technological Innovation Team of Shaanxi Province,ChinaProject supported by the K.C.Wong Education Foundation。
文摘The utilization of prefabricated light modular radiant heating system has demonstrated significant increases in heat transfer efficiency and energy conservation capabilities.Within prefabricated building construction,this new heating method presents an opportunity for the development of comprehensive facilities.The parameters for evaluating the effectiveness of such a system are the upper surface layer’s heat flux and temperature.In this paper,thermal resistance analysis calculation based on a simplified model for this unique radiant heating system analysis is presented with the heat transfer mechanism’s evaluation.The results obtained from thermal resistance analysis calculation and numerical simulation indicate that the thermal resistance analysis method is highly accurate with temperature discrepancies ranging from 0.44℃ to−0.44℃ and a heat flux discrepancy of less than 7.54%,which can meet the requirements of practical engineering applications,suggesting a foundation for the prefabricated radiant heating system.
基金The National Natural Science Foundation of China(No.51106023)the National Key Technology R&D Program during the12th Five-Year Plan Period(No.2011BAJ03B14)
文摘In order to have an in-depth understanding of the metal ceiling radiant panel with capillary tubes, a radiant ceiling heating system is constructed to study the actual heating performance and thermal comfort by experiments. In addition, the energy saving potential of the novel heating system is discussed in terms of the COP （coefficient of performance） of the ground source heat pump and the exergy efficiency of the radiant terminal. The results indicate that the heating system shows high thermal stability and thermal comfort. When the system reaches a stable condition, the radiant heat transfer accounts for 62.7% of the total heat transfer, and the total heat transfer can meet the heating demands of most buildings. Compared to a radiant floor heating system, it offers advantages in a shorter preheating time, a lower supply water temperature and a stronger heating capability. The COP of the ground source heat pump is increased greatly when the supply water temperature is 28 to 33 ℃, and the exergy efficiency of the metal ceiling with capillary tubes is 1.6 times that of the radiant floor when the reference temperature is 5 ℃ The novel radiant ceiling heating system shows a tremendous energy saving potential.
文摘To evaluate the thermal performance of a low-temperature electrical radiant floor heating system,an experimental facility equipped with a constant temperature chamber and different specimen floors is designed and built.The heating cable is installed in the floor slab with a unit-rated power of 30 W/m.Twenty-four different schemes are worked out and tested,which include three kinds of composite floor structures and eight kinds of cable distances.The cable distances are 30,40,50,60,80,100,130,150 mm.The main affective factors of the thermal performance and their influencing regularity are discussed.The experimental results show that the system has good stability and reliability,and the ratio of the radiation heat-transfer rate to the gross heat-transfer rate is greater than 50%.When the floor structure and the cable distance are fixed,the gross heat-transfer rate of the upper floor surface has a maximum value at an optimal cable distance.Under the experimental conditions in this paper,the optimal cable distance is 50 mm.
文摘Hydronic heating and cooling systems are considered the most efficient, greenest technology known to man for the efficient distribution of warmth and cooling;in other words, the ideal human comfort experience. For people who may not know what hydronics are, here’s the definition: Hydronics: A means of transferring the energy required for heating and cooling buildings utilizing water as the primary medium in an effort to maintain good human comfort and conserve energy resources. And while we are in definition mode, allow me to introduce a couple of other terms that are critically important. Comfort: My definition of comfort is being in a state of wellbeing, or not being aware of your surroundings. In this state, you are not hot, nor are you cold. Your sinuses are not too dry, nor is it too humid, and there is not a lot of noise in the background associated with the delivery of comfort. In short, if you have to think about your physical condition, you are probably not comfortable. Simply stated, if you are truly comfortable, you will not be thinking about it. Mean Radiant Temperature: Mean radiant temperature, or MRT for short, is one of those things that cannot (normally) be seen by the bare human eye, but is the primary dictator of excellent human comfort. By definition, MRT is the temperature of those solid items surrounding your body. When the MRT is high, human comfort is achieved with a lower air temperature. When the air temperature is high, good human comfort is achieved with a lower MRT. MRT can be seen using an infrared camera, but most people do not have access to this wonderful technology. Before I go into my dissertation, I want to quickly dispel a myth. People have been taught over the years that “heat rises.” This statement in and of itself is incorrect. Hot fluids rise. Hot air or hot water rise because of their differences in buoyancy compared to cooler surrounding fluids. Radiant energy travels in all directions, through the path of least resistance, including in a downward direction. The best explanation for comparison purposes is to think of being outside on a cool winter day when the sun is shining brightly and you are standing next to a dark colored wall. Your body can sense the radiant energy surrounding your body, and your body feels warmer than it really is due to this exposure to a higher MRT. Another prime example is sitting next to a campfire on a clear starlit night. Even though the ambient air temperature is low, your body can feel the radiation coming from the fire, and it feels warm and comforting on the side that is facing the fire. Your backside that is not facing the fire feels much cooler than the side that is facing the fire, so we rotate in an effort to even out this radiant exposure. If radiant energy only traveled upward, as in “heat rises,” we would have to stand on top of the sun in order to realize any comfort due to radiant energy. As was already proved in our previous statement about MRT, such is not the case. Controlling heat loss from our bodies by manipulating the MRT will guarantee that most people will be comfortable under all conditions. As can be seen from the above graphic, radiational losses account for nearly half of the human body’s heat loss.
文摘The radiative heat flux of the plume from reusable rockets is a critical parameter during the launch and return processes.This paper proposes a method for calculating radiative heat flux with higher accuracy than previously reported for a recoverable nine-engine liquid-propellant rocket.Based on the Radiative Transfer Equation(RTE),this study employs the discrete transfer method to solve the transient RTE problem using physical properties to describe the problem while avoiding the need to directly solve mathematical equations.The proposed method can effectively determine the radiative heat flux of the flow field and is applicable to problems involving various geometries.Calculations reveal that during the ascent phase of the rocket,the radiative heat flux at the base of the vehicle reaches its maximum in the initial stages of the lift-off,reaching a maximum of~50 kW/m^(2),which is 2.24 times the maximum value during the return phase.During the deceleration stage of re-entry into the atmosphere,the maximum radiative heat flux recorded on the sidewall of the rocket is 29.1 kW/m^(2);the maximum heat flux on the bottom surface is approximately 22.3 kW/m^(2),accounting for 76.6%of that on the rocket's sidewall.This provides a basis for the thermal protection design of the rocket's bottom and walls as well as for the thermal management of cryogenic propellant tanks.Future research will involve ground engine testing and flight experiments to further validate the proposed model.
基金supported by the Postdoctoral Fellowship Program of CPSF under Grant Number GZB20240379the National Natural Science Foundation of China(Grant No.52394223,52425801,52130803,and 52408102)the Natural Science Foundation of Jiangsu Province(Grants No.BK20241348).
文摘Building energy consumption is mainly influenced by thermal load,equipment efficiency,service space,and operating time.While extensive research has focused on reducing load and improving efficiency,significant energy-saving potential remains in optimizing time and space of usage.This study proposes a novel convective-radiant desktop-based terminal that integrates personalized environmental control system with convective-radiant terminals,enabling“part-time,localized-space”operations to enhance energy savings.It includes a discussion on the structural design of the device and experimental analysis of its local environmental control and intermittent operation.The design incorporates a convective heat exchanger and radiant panel embedded in a height-adjustable desktop.Experimental results showed that the combination of the radiant panel and air outlet beneath the desktop accumulates heat in this area during heating,creating a“cool head,warm feet”thermal comfort effect.The maximum vertical temperature difference was 0.7℃ in radiation mode.For intermittent operation,the temperature response matching coefficient(TRMC)of the proposed terminal was 3.4 times that of floor heating and 2.1 times that of fan coil units,indicating superior performance.Besides,this novel terminal provides effective thermal comfort in both sitting and standing positions,offering potential energy savings in open-plan offices.By extending the room temperature setpoint to 16–18℃ in winter,the terminal can reduce energy consumption by 3.64%–12.52%.These findings provide a reference for personalized environmental control systems and intermittent heating strategies.
文摘This paper presents a comprehensive experimental and numerical investigation of radiant floor heating(RFH)systems integrated with phase changematerial(PCM)-based thermal energy storage(TES).The study compares two underfloor pipe configurations:double serpentine and spiral.It also looks at how well a paraffin wax PCM system works with compact heat exchanger-type TES units during winter in Iraq.Key performance indicators including discharge temperature,heat transfer rate,liquid fraction evolution,and temperature uniformity were assessed through in situ experimental measurements and ANSYS fluent simulations.Results demonstrate that the spiral design provides slightly more uniform temperature distribution on the tile surface at an inlet water temperature of 55℃,with an average difference of approximately 0.5%,the serpentine layout exhibits higher slab temperature distribution by about 0.66%.Notably,the serpentine configuration shows superior thermal homogeneity and heat distribution,with a 15.05%increase in heat gain at a 55℃ inlet temperature compared to the spiral design.The performance gap between the two layouts narrows as the inlet temperature increases from 50℃ in 5℃ increments by approximately 4.1%,3.7%,and 1.7%,respectively.Higher inlet temperatures also improve PCM discharging and charging rates,improving energy storage utilization.The findings provide significant design guidelines for sustainable heating systems for cold climates.
基金The authors gratefully acknowledge the financial support provided by the National Natural Science Foundation of China(No.51778010),“Optimization design method of BIPV/T and solar heat pump coupled energy supply system”.
文摘This paper proposes two new radiant floor heating structures based on micro heat pipe array(MHPA),namely cement-tile floor and keel-wood floor.The numerical models for these different floor structures are established and verified by experiments.The temperature distribution and heat transfer process of each part are comprehensively obtained,and the structure is optimized.The results show that the cement-tile floor has the better heat transfer performance of the two.When under the same inlet water temperature and flow rate,the keel-wood floor's surface temperature distribution is about 2℃ lower than that of the cement-tile floor.The inlet water temperature of cement-tile floor is about 10℃ lower than that of keel-wood structure when the floor surface temperature is the same.During a longitudinal heat transfer above MHPA,the floor surface temperature decreases by 0.5℃ for every 10 mm filling layer increase.In order to reduce the non-uniformity of the floor's surface temperature and improve the thermal comfort of the heated room,the optimal structure for a floor is given,with the maximum surface temperature difference reduced by 3.35℃.We used research focusing on new radiant floor heating,with advantages including high efficiency heat transfer,low water supply temperature,simple waterway structure,low resistance and leakage risk,to provide theory and data to support the application of an effective radiant floor heating based on MHPA.
基金This research work was financially supported by the Natural Science Foundation of Sichuan Province(No.2022NSFSC1944)the National Natural Science Foundation of China(No.51708453).
文摘In the building with many transparent envelopes,solar radiation can irradiate on the local surface of floor and cause overheating.The local thermal comfort in the room will be dissatisfactory and the thermal performance of radiant floor will be strongly affected.However,in many current calculation models,solar radiation on the floor surface is assumed to be uniformly distributed,resulting in the inaccurate evaluation of the thermal performance of the radiant floor.In this paper,a calculation model based on the theory of discretization and the RC thermal network is proposed to calculate the dynamic thermal performance of radiant floor with the consideration of unevenly distributed solar radiation.Then,the discretization model is experimentally validated and is used to simulate a radiant floor heating system of an office room in Lhasa.It is found that with the unevenly distributed solar radiation,the maximum surface temperature near the south exterior window can reach up to 35.6℃,which exceeds the comfort temperature limit and is nearly 8.5℃higher than that in the north zone.Meanwhile,the heating capacity of the radiant floor in the irradiated zone can reach up to 171 W/m^(2),while that in the shaded zone is only 79 W/m^(2).The model with the assumption of uniformly distributed solar radiation ignores the differences between the south and north zones and fails to describe local overheating in the irradiated zones.By contrast,the discretization model can more accurately evaluate the thermal performance of radiant floor with the influence of real solar radiation.Based on this discretization model,novel design and control schemes of radiant floor heating system can be proposed to alleviate local overheating and reduce heating capacity in the irradiated zone.
基金National Science and Technology Major Project of China(No.2017-Ⅲ-0003-0027)。
文摘As one of the core components of aero-engine,the thermal protection scheme of combustion chamber has an important impact on its service life.In order to improve the design level of high-performance combustion chamber,the radiation heat transfer characteristics of combustion chamber are studied by experimental method.The following results are obtained:1)With the increase of oil-gas ratio,the gas temperature increases first and then tends to be stable,the radiant heat flow increases gradually,the convective heat flow increases gradually and then tends to be stable,and the proportion of radiant heat flow remains basically unchanged;2)With the increase of the inlet temperature,the gas temperature increases gradually,the radiant heat flow,especially in the flame barrel head area,increases significantly,the convective heat flow remains basically unchanged,and the proportion of radiant heat flow increases significantly;3)With the increase of the combustion chamber pressure,the gas temperature increases gradually.When the combustion chamber pressure is low,the radiant heat flow increases sharply with the increase of the pressure;When the combustion chamber pressure is high,the radiant heat flow increases slowly with the increase of the pressure.The convective heat flow gradually decreases and tends to be stable,and the proportion of radiant heat flow gradually increases and tends to be stable.This study is of great significance to improve the calculation accuracy of radiant heat flow of combustion chamber and the reliability design of thermal protection scheme of combustion chamber.
文摘Far infrared(FIR)radiation(3-100µm)is an electromagnetic spectrum commonly studied for biological effects.This article aims to discuss using Far infrared radiation with sub-division(4-24µm)of this waveband to stimulate tissues and cells and is considered an effective therapeutic modality for specific medical disorders.The IR application as a medical therapy has advanced rapidly in recent years.For example,IR therapy like IR-emitting apparel and materials that can be run solely by body heat(does not need an external power supply)have been developed.New methods for providing FIR radiation to the human body have emerged due to technological advancements.Specialty saunas and lamps that emit pure FIR radiation have become effective,safe,and widely used therapeutic sources.Fibers infused with thermide,FIR emitting ceramic nanomaterials and knitted into fabrics are used as clothes and apparel to produce FIR radiation and benefit from its effects.A deeper understanding of FIR's significant innovations and biological implications could aid in improving therapeutic efficacy or developing new methods that use FIR wavelengths.
文摘The effect of pressure on combustion and heat transfer is analyzed. The research is based on the basic combustion and heat transfer theorem. A correction for the heat calculation method for pressurized furnace is made on the basis of the normal pressure case. The correction takes the effect of pressurizing into account. The results show that the correction is reasonable and the method is applicable to combustion and heat transfer of the marine supercharged boiler.
文摘Flame heat transfer blockage occurs as fuel vapors, soot and products of combustion near a burning fuel surface block much of the heat feedbacks （including external radiative heat flux） to the fuel surface of a burning object. Blockage clearly affects burning rates and heat release rates of fires. This needs to be included when calculating flame heat transfer in fire growth models. An understanding of bttrning of materials in small scale fires is of broad and vital importance for predicting their burning performance in large scale fires. The blockage phenomenon was clearly observed and quantitatively measured in experiments that took advantage of the unique capability of the Fire Propagation Apparatus （FPA） of being able to vary the ambient oxygen concentrations. An indirect measurement approach was established which provides an experimental understanding of the concept of the blockage. The measurements were further explained by a one-dimensional steady-state model of a diffusion flame, which focuses on the radiant absorption and emission by the gas-soot mixture of flames. The theoretical model provides a greater understanding of the fundamental knowledge of the blockage. The overall heat transfer blockage factor can be up to 0.3 -0.4 for PMMA and POM. The factor and its components are nearly independent of the external radiation, but increase as the ambient oxygen concentration rises. A comparison between experimental data and model prediction shows a good agreement.
文摘The R-value is defined as,“a measure of the resistance of an insulating or building material to heat flow,expressed as R-11,R-20,and so on;the higher the number,the greater the resistance to heat flow(Random House,2016).”The first thermodynamic principle violated by the R-value is the singular use of the word heat flow.Heat flow,or transfer,occurs in three distinct ways;conduction,convection,and radiation.The R-value test will only measure a bulk insulations resistance to conductive heat transfer.This type of heat flow is almost undetectable in the built environment,regardless of climate or season-resulting in the R-value myth.In winter,the stack effect will cause convective flows through the home as warm air under pressure rises and escapes through the top,requiring an equal amount of cold replacement air to infiltrate at the bottom.On hot sunny days,the exterior of the home absorbs long wave ultra violet(UV)rays from the sun and reemits this radiant heat energy into the residence.The thermodynamics of an occupied structure under varying atmospheric conditions is not well understood,leading to major inefficiencies.The goal of this conceptual study is to reveal the shortcomings of current insulation practices at the residential level,conceptualize a series of related issues for future study and develop a preliminary methodological concept for resolutions to the problems identified.Conclusions indicate that further research needs to be dedicated to replacing the R-value rule with a realistic metric that considers the efficiency,health,and safety of the entire building.
