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.

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.

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.

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.

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。

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。

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。

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%.

城市下垫面辐射热作用过程差异分析

为了研究城市不同下垫面辐射热作用过程的差异,选取4种下垫面(草地、混凝土、铺面砖、沥青)为研究对象,测量不同下垫面反射的短波辐照度、向上的长波辐照度、地表热流强度以及空气温度、风速等环境参量。分析对比不同下垫面辐射热传递过程中的差异。结果表明:大气逆辐照度占下垫面吸收辐射热的65%以上,4种下垫面以长波辐射的形式释放热量均在75%以上;下垫面与空气间的换热主要以辐射换热的方式进行;夏季草地热稳定性最好,混凝土下垫面的热稳定性最差;冬季混凝土的热稳定性最好,铺面砖的热稳定性最差。

下垫面反射特性对外墙辐射得热量影响研究

墙体辐射得热量是影响围护结构传热性能的主要因素,基于下垫面反射特性研究代表性城市建筑墙体辐射得热尤为重要。选取哈尔滨、北京和兰州3个城市草地和砖地下垫面,以太阳直接辐射量和天空散射辐射量之和为对照组,探讨了下垫面反射特性对室外空气综合温度、不同城市辐射能、反射辐射能占总辐射能比重及对建筑墙体总辐射能的影响。结果表明:与对照组相比,下垫面反射会对室外空气综合温度和外墙体辐射得热量产生不同程度的影响,3个城市室外空气综合温度增大2.5℃以上的小时数均为4 h,增值范围为0.51~5.23℃;下垫面反射会加剧建筑墙体辐射得热,不论是草地还是砖地,不同下垫面反射辐射占总辐射能的比重由大到小依次为兰州>北京>哈尔滨;夏季砖地的反射辐射比草地分别多77.6 MJ/m^(2)、84.2 MJ/m^(2)和87.6 MJ/m^(2),冬季则分别为23.0 MJ/m^(2)、30.8 MJ/m^(2)和32.4 MJ/m^(2)。对进一步改善建筑周边热环境及合理布局建筑室外下垫面提供理论基础。

地面局部辐射供暖典型热环境特征化表征研究

局部精细化采暖是满足室内人员舒适前提下降低采暖能耗、实现采暖能源高效利用的重要方式之一.为提高采暖效率,给精细化辐射供暖提供方法参考,本文选取具有显著工位布局要求的办公场所作为对象,对地面局部辐射供暖模块影响下,室内不同区域热环境分布情况进行典型化研究分析,得到了不同局部模块供暖工况下室内非均匀热环境分布特征.分析结果表明,局部辐射面积为16.7%时辐射区域与非辐射区域平均辐射温度相差3℃以上,具有明显的局部环境营造效果;地面局部辐射供暖辐射区域与非辐射区域不对称辐射温度差异显著;将局部辐射源设置在靠近外墙区域,可以提高整体平均辐射温度,使室内平均辐射温度分布更为均匀.本研究初步给出基于地面局部辐射供暖的典型化热环境共性特征表述,可为后续局部辐射供暖系统的精细化设计提供参考.

居住建筑集中供暖用户散热器改地暖相关问题调研与探究

近年来,既有居住建筑中部分散热器用户改造为地板辐射供暖的情况时有发生,且有逐渐增多之势。由于两种供暖末端的水力特性及设计供、回水温度迥然不同,并且地暖系统的循环阻力比散热器增大很多,因此地暖系统与散热器系统并网后会影响整个供暖系统的水力平衡,进而引发热力失调。通过调研北京市地区居住建筑集中供暖用户散热器改造为地板辐射供暖的典型改造方式及实际工程案例,分析不同热用户改造后遇到的问题和对其他用户产生的影响,为后续供暖用户进行地暖改造提供参考。

消防员灭火防护服减层结构及其热防护性能评价

介绍了消防员灭火防护服减层结构的实现方式,运用国内外不同的热防护性能评价方法,对标准4层组合面料及3层、2层减层结构组合面料进行评价,并采用热人仪测试不同组合面料制成的灭火防护服的防护效果。结果表明,3层和2层减层结构组合面料能达到标准4层组合面料的性能,满足消防员灭火防护服要求,符合轻质化发展趋势。