Operation optimization of prefabricated light modular radiant heating system:Thermal resistance analysis and numerical study

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.

Thermal comfort assessment and energy consumption analysis of ground-source heat pump system combined with radiant heating/cooling

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.

WHY HYDRONIC POWERED RADIANT HEATING AND COOLING ARE A PERFECT MATCH FOR GREEN BUILDING CONSTRUCTION

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.

A simulation Study on the System Combined Solar Energy with Biogas Boiler for Floor Radiant Heating and Fuel

A mathematical model was built for simulating an innovative design system combined solar energy with biogas boiler for floor radiant heating and fuel. Effects of the ambient air temperature on the performance of the system had been examined. And the results also support theoretical feasibility of the system.

Experimental study and energy saving analysis of a novel radiant ceiling heating system

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.

Experimental study of low-temperature electrical radiant floor heating system

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.

Feasibility Analysis on the Integrated Application of Solar Energy, Biogas, Coal-fired Boiler and Radiant Floor Heating for Rural Residence

The feasibility of adopting a balanced energy mix mode (domestic solar energy, biogas, coal-fired boiler and radiant floor heating) was proposed. Taking a typical rural residence in Zhengzhou City for example, the study through theoretical analysis and calculation showed that such a balanced energy mix is an economic way and efficient in saving energy and reducing air pollution, and elaborated the theoretical feasibility of popularizing such a heat supply mode in rural areas.

Assessment of Building External Wall Thermal Performance Based on Temperature Deviation Impact Factor under Discontinuous Radiant Heating

As the variation and timely meeting thermal environment requirement of indoor air temperature has a close relationship with the thermal performance of building external wall under discontinuous radiant heating condition, one appropriate assessment method or index for assessing the building external wall thermal performance is very necessary. In order to reasonably evaluate the thermal performance of external wall under discontinuous radiant heating condition and build the direct connections and interactions among the indoor air temperature, external wall inner surface temperature and outdoor air temperature, the first and second impact factors of temperature deviation were established, based on one mathematical model of room heat transfer. For one experimental room and four types of external walls under discontinuous radiant heating condition, both the influence of the external wall inner surface temperature deviation on the indoor air temperature and that of the outdoor air temperature deviation on the external wall inner surface temperature were determined effectively with the first and second impact factors of temperature deviation. In addition, favourable performance for the self-insulation and inner insulation walls were found, due to their superiority in effectively and timely improving the indoor thermal environment under discontinuous radiant heating condition.

Modeling and Simulation of Heat Transfer Phenomenon from Infant Radiant Warmer for a Newborn Baby

Nowadays death of a newborn baby due to hypothermia is one of the vital factors. To overcome the problem infant radiant warmer has been used in hospitals which helps to prevent excessive heat loss of the baby by maintaining a proper temperature. However, in practice, it is critical to regulating proper thermal stability that is exactly required for a premature baby to conquer the heat loss problem. In this study, we have established a computational model for heat transfer analysis using the Finite Element Method. The heat transfer to the surrounding area skin of newborn with the help of Infant Radiant Warmer (IRW) is simulated to study the best range of light source to overcome the hypothermia. We simulate the efficiency and effect of the infant radiant of the thermal radiation using COMSOL Multiphysics program. For this simulation, we considered the distance between the infant’s mattress and the bottom surface of the heater unit as 70 cm and the heater power 500 watts, and 600 watts. We have investigated mattress temperature, baby temperature and surface radiosity which are important to understand to increase newborn baby body temperature. It is found that the temperature of mattress raises up to 36 - 36.5 degrees Celsius and skin temperature raises up to 37 - 37.5 degrees Celsius.

Study on the Influence of Piloti on Mean Radiant Temperature in Residential Blocks by 3-D Unsteady State Heat Balance Radiation Calculation

Piloti is commonly used in tropical and subtropical climate zones to get high wind velocity and create shadowed areas in order to optimize the living environment of residential blocks,but there are few studies to reveal the influence of piloti on the radiant environment of residential blocks systematically. Taking the city of Guangzhou as an example,using 3-D Unsteady State Heat Balance Radiation Calculation Method,this paper shows that the mean radiant temperature( MRT) under piloti area increases with the increase of piloti ratio,and especially when piloti ratio is equal to 100%,the MRT increase trend becomes sharp. The MRT of exposed area decreases with the increase of piloti ratio,especially when piloti ratio reaches 100%,the decrease trend of MRT becomes sharp,which offers the reference for the study on piloti design in subtropical climate zones and further research on living environment by CFD simulation in residential blocks.

直流燃烧室内气体辐射换热特性研究

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.

Magnetic Oil Thermal Behavior under Electromagnetic Induction for Energy Efficient Heating System Design

This study describes thermal behavior of magnetic lubricant oil under electromagnetic induction. Experimental set up include oil pump, oil tank, induction heating unit, and heat exchanger. It is a closed loop system where the oil pump circulates oil through oil tank to the system, at the same time induction heating unit heats up to the heat exchanger where the lubricant oil thermal behavior is examined. The unit has been largely studied and tested both magnetic and regular motor oil in a laboratory environment and promising results have been obtained for an actual indoor floor to space heating system design.

Research on Radiant Carrier of Matching Radiant Type Far Infrared Textiles

This paper deals with the radiation effects of different kinds ofradiant carriers used in making far infrared textile materials.From two radiation experiments,methods of testing radiation ef-fects of carriers have been found,results of the experiments arediscussed.Finally,some conclusions for choosing appropriateradiant carrier are drawn.

考虑平均辐射温度的室外作业人员热应激研究

为了准确预测室外高温环境下作业人员的热应激水平,研究了作业人员核心温度和最大允许暴露时长的影响。基于平均辐射温度和代谢率的计算方法对预测热应激(Predicted Heat Strain,PHS)模型进行改进,研究不同平均辐射温度和代谢率对作业人员的核心温度的影响,并分析了直肠温度和出汗量确定的最大允许暴露时长的变化规律。结果显示:人体核心温度随平均辐射温度和代谢率的增加而增大,当代谢率≥419 W/m^(2)时,人体核心温度随作业时间快速上升并达到阈值;代谢率和平均辐射温度对出汗量确定的最大允许暴露时长影响较小,直肠温度确定的最大允许暴露时长随着代谢率的增加而显著降低。研究结果可为室外高温作业人员热安全评估提供指导。

热辐射特征参数对快堆锥形顶盖空间换热特性影响的研究

池式钠冷快堆的钠池内充满高温液态钠,其上方覆盖有氩气,高温液态钠主要通过辐射换热及对流换热的方式向快堆主容器上部结构及氩气空间传递热量,其换热特性及其影响因素十分复杂。辐射发射率及液态钠蒸发形成的气溶胶层对主容器上部结构的热工水力特性会造成一定影响。因此,为保证主容器上部结构在不同温度载荷下的安全性与稳定性,十分必要获取不同辐射发射率及不同气溶胶层分布下的温度分布。本研究建立大型池式钠冷快堆主容器上部锥形顶盖空间(以下简称“锥顶盖”)数值计算模型,开展数值模拟计算,得到不同发射率及气溶胶层厚度影响下锥顶盖的温度场。研究结果表明,发射率越高,锥顶盖斜肩及氩气空间温度越高;当气溶胶层存在于靠近钠液面的高度范围时(0~0.2 m),增加其厚度可使氩气空间局部温度升高,但对锥顶盖斜肩温度影响有限。发射率增高53%,则辐射换热量增加31.47%,格拉晓夫数(Gr)减少19.29%,辐射换热效果增强,自然对流效果减弱;气溶胶层高度由0增加到0~0.1 m时,对辐射换热量的吸收增加22.68%,格拉晓夫数(Gr)减少19.29%,气溶胶层高度由0~0.1 m增加到0~0.2 m时,透过气溶胶层的辐射换热量减少了0.04%,格拉晓夫数(Gr)增加了0.9%,辐射换热效果减弱,自然对流效果加强。

高原铁路站房地板辐射系统的分区供暖效果

为了解决高原铁路站房部分区域在强太阳辐射的影响下出现过热、地板辐射供暖系统能耗浪费的问题,以某高原铁路车站为研究对象,根据站房内太阳照射情况对地板辐射系统提出了分区供暖方案;利用建筑能耗模拟软件Energyplus对该铁路站房进行模拟分析,对比了地板辐射系统分区前后站房内的热环境和系统供暖量.结果表明:地板辐射系统采用统一的设计及运行控制方案供暖时,站房内太阳直射影响区的平均操作温度在日间最高可达27℃,与非直射影响区之间的温差超过5℃;在地板辐射系统分区供暖时,直射影响区的平均操作温度最高为26℃,室内温度分布更为均匀,局部过热现象得到缓解;在保证站房热舒适性的前提下,地板辐射系统的分区供暖方案能够使直射影响区整个供暖季的供暖量降低38.2%.

基于CFD的辐射冷顶板与风扇耦合系统性能优化

吸音板用来解决辐射式天花板供冷系统的噪声问题,但其阻碍了辐射换热。本文提出通过风扇的调风作用来优化辐射冷顶板与风扇耦合系统,基于CFD模拟讨论了耦合系统的室内气流分布、热舒适及换热系数变化,研究了吸音板安装方式、风扇转速和风扇转向对辐射天花板性能的影响。结果表明:风扇的加入增大了顶板的对流换热系数和总换热系数;随着风扇转速的增大,室内的空气温度和人体热舒适性评价指标(PMV)降低;风扇向上吹风的效果优于向下吹风,吸音板竖直安装优于水平安装。

光伏组件布置方式对光伏温室温光环境的影响研究

在温室结构中引入光伏组件会对温室内部的光、热环境产生积极影响,为探究各季节屋顶光伏对温室内部环境的影响,获得最佳覆盖率,进而在改善光伏温室内光热环境的同时提高光伏发电量,建立温室内辐射得热模型并通过实验验证模型的准确性。结合所提出的光伏温室系统,对典型日下对某顶部面积为420 m2的光伏温室在不同光伏组件覆盖率下的室内辐照量、室内气温及光伏发电量进行模拟分析。结果表明,与不铺设光伏组件相比,光伏组件的覆盖率每增加12.5%,春分日、夏至日、秋分日、冬至日的室内辐照量分别降低2.79%、5.8%、2.90%、0.70%,白天室内气温分别降低1.19%、0.54%、0.49%、1.12%。通过对植物生长所需的光、温条件进行分析,得出各典型日的最佳光伏组件覆盖率分别为62.5%、50%、62.5%、25%。

不同供暖末端办公建筑室内热环境和人体热舒适调研

为明确寒冷气候区办公建筑辐射供暖和对流供暖模式下的室内热环境参数是否能满足人体热舒适需求,本研究选取西安市不同供暖模式的办公建筑为调研对象,同时进行了室内物理环境测试和人体热舒适主观问卷调查,调研期间共获得1 120份有效问卷。结果显示:对流供暖模式下室内空气温度和竖直温差显著高于辐射供暖,且室内存在过热现象;辐射和对流供暖的中性温度分别为17.4℃和20.4℃,较高的室内空气温度形成了较高的中性温度和可接受温度上限。

绿色高层建筑室内太阳辐射热量估算仿真研究

绿色建筑窗体太阳辐射热量预测实时性低且准确性差,为解决上述问题,提高研究的实用性,基于外环境数据处理,在相关性分析与聚类分析的基础上,提出一种数据处理与数据预测相融合的建筑室内太阳辐射热量预测算法,即PKM_SVR算法。算法首先对外环境数据进行预处理,然后在Dynamic Daylighting中构建房屋建筑主体;接着对室外环境数据进行匹配,通过选则窗体透射率,计算该状态下室内逐块辐射热量;然后对室内辐射热量与室外环境数据进行相关性分析与聚类处理,并将处理后的数据划分成训练、测试集;最后基于交叉验证的方法构建优化PKM_SVR室内辐射热量初始预测模型。仿真结果表明,十折交叉算法对模型优化效率最高,此时G=0.692、C=5.824,且R^(2)=0.925;对比仿真结果表明,较其它基线算法模型相比,PKM_SVR模型具有最低的RMSE指标参数,较ANN与SVM模型相比,分别降低了23.1%和31.3%,且具有较高的R^(2)指标参数,平均提升了10.7%。综上所述,PKM_SVR算法有效的提升了室内热量预测的准确率,具有重要的仿真价值。