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.

Evaluation of the thermal performance of radiant floor heating system with the influence of unevenly distributed solar radiation based on the theory of discretization

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.

Performance simulation and optimization of new radiant floor heating based on micro heat pipe array

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.

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 investigation on heat transfer characteristics of a new radiant floor system with phase change material

In order to improve the heat transfer characteristics of the traditional phase change material（PCM） floor, a new double-layer radiant floor system with PCM is proposed, which can store thermal or cold energy in the off-peak period and use them in the peak period. An experimental setup was developed to study the heat transfer characteristics of the new system under both cooling and heating modes. The experimental results show that the double-layer radiant floor system with PCM can meet both the cold and thermal requirements of users. Moreover, with the same duration of the thermal energy storage process, the increase of water temperature supplied to the system can improve the heat transfer characteristics of the system but lead to the discomfort of users. On the other hand, if the air temperature at the end of the thermal energy storage process is the same under different conditions, the increase of supplied water temperature will decrease the thermal energy storage time and ensure the comfort of users.

Crawlspace heating system in detached house with insulated foundation

Two practical crawlspace heating systems introduced in detached houses have been chosen as a field study. One is the crawlspace warm air heating system and the other is the crawlspace hot water circulation system. Based on the field study result, by using the simulation sol, ware, THERB, the effectiveness of the crawlspace warm air heating system has been examined. The effect of the factors, such as the wind amount circulating between crawlspace and indoor space, foundation insulation condition, and heat amount into the crawlspace, on the indoor thermal environment has been analyzed. Based on these analyses, the measured crawlspace heating system can make the average temperature of the living room above 20℃. These two houses have excellent thermal environment. According to the simulating result, heat amount input into crawlspace, which can make comfortable indoor thermal environment, for every month in heating period has been roughly concluded, and they are 600 W in December and March and 800 W in February and January, respectively.

内埋可变导热管建筑顶面隔热层节能分析

为减少室内空调能耗,文中对目前广泛使用的在建筑顶面之上铺制隔热层的建筑节能方法做进一步优化。文中以北京地区某建筑为例进行计算分析发现,隔热层的高热阻在夜间不利于建筑顶层白天积累的热量向外界排散。为在夏季夜间减小隔热层热阻,加速建筑顶层白天积累热量的排散,提出一种内埋可变导热管的建筑顶面隔热层,即在建筑顶面隔热层内间隔一定距离埋制可变导热管。夏季白天工况,可变导热管不启动,为高热阻状态;夏季夜间工况,可变导热管传热能力强,减小了隔热层热阻,加快了夜间建筑顶层结构热量的向外排散,计算结果表明,按照间隔0.3m铺制可变导热管的隔热层比铺制普通隔热层的空调制冷量下降15.1%;冬季工况热管传热能力非常差,隔热层保持了高热阻状态,避免了室内热量损耗。这种方法节能效果明显,可为建筑节能研究工作提供参考。

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%.

相变蓄热对光伏相变复合围护结构隔热及发电性能的影响

基于光伏发电和相变蓄热耦合特性,提出了光伏相变复合建筑围护结构,并进一步分析相变蓄热对复合围护结构性能的影响规律。首先构建光伏相变复合围护结构热流传递模型,然后探究相变层结构位置、相变温度以及相变厚度对其发电能力和隔热效果的影响。在此基础上,通过对比传统围护结构和复合围护结构的热工特性,阐述复合围护结构调节室内环境负荷及节能潜力。研究表明,相变蓄热对于光伏相变复合围护结构发电和隔热性能具有较大影响。相变材料越靠近室内其隔热效果越好,室内温度表现出向相变温度靠近的趋势;相变材料靠近光伏板意味着可以更充分地储存热量,光伏发电量也就越高。其中相变材料靠近光伏板时发电量为1263.06 J,较光伏围护结构有明显提升。同时相变材料的厚度在40 mm时发电量达到最大值,较10 mm时的工况提升了0.55%。此外,在一个运行周期内,光伏相变复合围护结构显著降低了建筑冷负荷,表现出较好的隔热与节能效果。

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。

相变蓄热地板的研究现状与展望

相变材料(PCM)是一种储能材料,具有高蓄热性能。在建筑领域中,相变材料可用于地板辐射供暖系统中,通过利用相变储能地板能够储存和释放大量的潜热,可以实现削减供热系统负荷峰值的目的,从而达到建筑节能的效果。本文对目前蓄热技术、相变地板辐射采暖技术进行了总结,并简述相变材料物化性、地板结构及封装定形技术对其热性能的影响。最后,对其未来的研究方向进行展望。

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。

外加剂及EPS对保温隔声砂浆性能的影响

为解决人们对住宅楼地面保温隔声性能的要求,减少建筑使用的能耗与污染,探究了外加剂对石膏基楼板保温隔声砂浆施工性和保水性的影响,以及聚苯乙烯发泡颗粒(EPS)对砂浆性能的影响。结果表明,纤维素醚(HPMC)和胶粉最佳掺量分别为3.6‰和7.2‰。石膏基楼板保温隔声砂浆的标稠用水量随着EPS掺量的增加而增大;EPS对降低砂浆的干密度作用明显,掺量为4.2%时,硬化体干密度降至290 kg/m^(3);28 d抗压强度随EPS掺量增加而降低。EPS掺入对提高砂浆的保温性能和隔声性能效果显著,在掺量为4.2%时的导热系数和撞击声压级最低,分别为0.076 W(/m·K)和63.1 dB。

建筑内热源滞后冷负荷监测模型研究

准确获取内热源实时冷负荷对于制定供暖空调系统节能调控策略及降低建筑运行能耗具有重要意义,而辐射热传递过程产生的滞后冷负荷是内热源冷负荷计算的难点,为此,基于围护结构蓄放热规律、热传递特性及传递函数原理等建立内热源滞后冷负荷监测模型,该模型为10阶传递函数。为了简化计算过程、提高计算精度,利用辐射时间系数对该模型进行参数辨识及降阶分析,最终得到2阶传递函数。建立试验系统对模型进行验证,结果显示,模型的平均绝对百分比误差为8.19%。内热源滞后冷负荷监测模型可依托能耗监测平台实现负荷的在线监测,对描述滞后冷负荷的时间延迟规律及幅度衰减特性具有理论意义,为制定供暖空调系统节能调控策略提供理论依据。

夏热冬冷地区低温辐射地板供暖影响因素的正交试验

为了研究夏热冬冷地区低温辐射地板供暖影响因素,采用L25(56)的正交试验方法探究供水温度、管间流速、管径、管间距、填充层厚度5因素对地板表面平均温度和均匀度的影响,获得各因素对试验指标的影响趋势、显著性程度和组合的最优解。研究表明:对地板表面平均温度的影响程度为供水温度>管间距>管径>填充层厚度>管间流速,对均匀度的影响程度为管间距>供水温度>填充层厚度>管径>管间流速,最优水平组合为:供水温度取35℃,管间流速取0.4 m/s,管径取16 mm,管间距取100 mm,填充层厚度取75 mm。试验结果为夏热冬冷地区辐射供暖设计提供借鉴,亦可对数值分析软件与统计学的结合提供思路。

地板新风+地板辐射供暖房间空气环境的实测分析

文章对安装了地板新风+地板辐射供暖系统的住宅样板房主卧室的空气温度和CO_(2)浓度进行实测,分析了房间的室内热环境及污染物浓度分布特征。结果表明,辐射供暖系统开启后房间温度在190 min左右升至最高,此后逐渐趋于稳定,且温度值略低于设定温度。室内温度呈下高上低分布,坐姿头足温差和站姿头足温差随系统运行逐渐增大,稳定时分别趋于0.3℃和0.6℃。辐射地板温度和室外温度是影响室内温度的主要因素。室内高度方向的CO_(2)浓度分布主要受室内人员位置和新风口位置的影响,辐射供暖房间内地板新风系统的排污效率与ASHRAE 62.1标准规定的推荐值相符。

东北地区农房采暖需求及围护结构节能改造方案研究

东北地区清洁取暖改造工作正处于关键时期,围护结构节能改造是保障该项工作顺利实施的重要环节,但现有关于东北地区农房围护结构节能改造技术节能率及经济性的综合性研究较为缺乏,难以指导技术方案选取。通过实地调研获取东北地区典型户型、围护结构特点和采暖需求特征,利用DeST建模计算多种围护结构节能改造技术的节能率,并综合考虑节能效果和经济效益确定适宜当地的围护结构节能改造方案。结果表明,当地农房主要为三间半式和两间半式户型,采暖房间数主要为2-3间,且70%的农户主要在1间有炕的卧室活动,呈现部分时间全部采暖空间为主的采暖特征。简易阳光房+30mm北墙EPS保温的围护结构节能改造方案,节能率达到17.4%,总改造费用最低,仅为2354元,是兼顾节能与经济的优选方案。研究结果可为东北地区农房围护结构节能改造和清洁取暖工作提供理论和数据支撑。

不同截面地暖管传热性能和节能分析

针对面积相同的三角形、梯形、长方形、正方形和圆形截面地暖管低温热水辐射采暖利用Fluent模拟了表面温度分布、地面平均温度等,并计算了表面温度不均匀度以及摩擦阻力、进出口压差和热效率。结果表明,流量在110cm3/s下,三角形(倒置)截面管道的地表平均温度比传统圆形提高了1.1℃;梯形(倒置)的表面温度不均匀度传统圆形截面管道优化了12.27%;在热效率方面,由高到低依次为三角形(倒置)>三角形(正置)>梯形(倒置)>矩形(宽高比为0.785)>矩形(宽高比为1)>矩形(宽高比为1.27)>圆形>梯形(正置),其中三角形(倒置)截面管道的热效率比传统圆形提高了17.9%。