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.

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.

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.

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.

Thermal Protective Performance of Heat and Flame Resistant Fabrics in Different Radiant and Convective Heat Exposures

The thermal protective performance (TPP) is important for heat and flame resistant fabrics. In this study, fabrics which are made of flame resistant cotton, Nomex, polybenzimidazole (PBI), polysulfonamide (PSA), kermel, and blend of kermel with rayon fiber are investigated on high intensity of different radiant and convective heat source. The mechanism of heat transfer in different situations is discussed. It is identified that exposed condition has an important effect on thermal protective performance. TPP rating increases with the increasing percentage of convective heat.

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.

Duty Cycle of a Radiant Ceiling Heating System under Extremely Cold-Temperature Conditions:A Theoretical Assessment

This work focuses on the estimation of a duty cycle of a radiant ceiling heating system with a panel surface temperature of 35℃and a heat flux of 65 W/m2 that corresponds to a thermal comfort for sedentary occupants.The results obtained are based on the theoretical heat transfer equations that govern the radiant and natural convection heat exchange mechanisms,and experimental heat transfer coefficients available in the literature.The results of the examined radiant heating system with specific conditions showed that a duty cycle of 6.46 min alternated by 13.36 min in shutting-down position is required to assure an acceptable thermal comfort for the enclosure space occupants.In addition,the study showed that for extremely cold-temperature conditions the heating system requires a daily operating load of about 61.2%which clearly proves the efficiency of these radiant heating systems in terms of energy consumption.

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。

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。

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。

高密度立交出入口区段车流量对驾驶人精神负荷影响

要为明确高密度互通立交行驶环境下,主线车流量对出入口区段驾驶人精神负荷间的影响,在重庆市内环快速路高密度互通立交群进行自然驾驶实车试验,使用Physiolab生理检测仪连续采集驾驶人在行驶过程中的心电数据,用于统计各驾驶人的心率指标变化情况。本次试验基于主成分分析法选择心率变异率指标RMSSD(root mean square of successive differences)、LFnorm(low frequency norm)、HFnorm(high frequency norm)、LF(low frequency)/HF(high frequency)以及心率突变率指标HRMR(heat ratemutation rate)作为驾驶人精神负荷的评价指标,记为主成分F 1和主成分F 2,并建立评价模型。结果表明:驾驶人在小净距立交出入口区段行驶时,立交主线车流量的大小会影响驾驶人的精神负荷;当驾驶人驶入立交主线时,三次模型对入口段车流量与主成分F 2的拟合效果最好,呈开口向上的三次曲线,曲线谷值点出现在2级流量水平处,模型显著;当驾驶人驶出立交主线时,一次线性模型对出口段车流量与主成分F 1的拟合效果最好,模型显著。

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。

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.

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.

风速与风向对人体热交换影响的CFD仿真模拟

为了提升灾害环境中人体热损伤评估精度并保障应急救援人员的生命安全,首先将暖体假人进行三维激光扫描得到数值假人,并按照人体生理构造将其划分为20个区块,通过ICEM软件建立气候室,设置0°~180°的风向;然后通过FLUENT软件计算得到0.2~5.0 m/s风速时的人体显热换热量和辐射换热量,在此基础上求得对流换热量;最后将模拟结果与文献中数据进行对比验证,并分析不同风速与风向对人体热交换的影响。结果表明:提出的计算流体动力学(CFD)仿真模拟方法可有效模拟人体不同部位的换热量;风速的增加会促进人体与环境之间的热交换,当风速从0.2 m/s增加到5.0 m/s时,人体整体对流换热量从56 W/m^(2)增加到360 W/m^(2);人体表面局部部位之间对流换热量有明显的差异,其中四肢部位与环境之间的热交换受风速影响更为明显;风向对人体整体对流换热几乎没有影响,但躯干部位对流换热量受风向的影响较大;在非对称风向(45°、90°、135°)下,人体对流换热量呈现非对称式分布。本研究可为人员安全评估、极端环境下人体热反应建模、防护装备研发等提供基础数据。

船舶机舱火灾热烟分布特性仿真及安全评估

机舱是船舶输出动力的关键舱室,同时也是火灾危险源集中分布的火灾事故高发区。为了评估某船机舱区域的火灾事故特性,针对该船发电机舱开展了油池火典型火灾场景的大涡模拟仿真,并使用烟气温度、辐射热通量两项指标对火灾发生后的机舱环境进行了安全评估。结果显示:火灾发生后机舱内平台甲板下方烟气温度可快速升至200℃以上;火灾发生后74 s,舱内部分电子设备出现永久性损伤;火灾发生后180 s左右,对于消防人员与机舱设备而言机舱处于危险状态,同时舱内绝大部分电子设备发生永久性损伤。本研究结果对船舶机舱设计与消防策略制定具有指导意义。

辐射空调系统供暖特性试验研究

为探究辐射空调系统供暖特性,搭建辐射空调系统试验台,进行7 d的系统间歇运行试验,对两级新风机组送风温湿度,空气源热泵主机制热量、能效比,以及系统能耗和能效比进行分析。结果表明,在设定参数下,两级新风机组稳定时送风温湿度分别为27℃和35%左右,空气源热泵主机平均制热量为4.5 kW,制热性能系数(COPU)为4.10;辐射空调系统耗电量为1.5 kW·h,系统性能系数(COPS)为3.02。试验结果可为系统的进一步优化和推广提供参考。

加热炉排烟热量损失和炉体散热损失探讨

提高加热炉热效率需要进一步降低排烟热量损失、减少炉体散热损失。文中对负荷相当的两台加热炉进行计算分析。当排烟温度为80℃时,排烟热量损失占比约为3%;若要将排烟热量损失占比降为2%,则排烟温度接近空气的露点温度,会产生大量凝结水,将会出现露点腐蚀等问题。当设计外壁温度为80℃时,系统总散热损失可能大于放热量的3%,其中余热回收系统散热损失占比大于1%;在环境风速为2 m/s的工况下,系统总散热损失占比约增加0.3百分点。当设计外壁温度为65℃时,系统总散热损失占比约为2.5%,其中余热回收系统散热损失占比约为1%。加热炉热强度越高,炉体结构尺寸越小,散热损失越小,实际运行时加热炉热效率越高。

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。