Modeling and simulation of under-floor electric heating system with shape-stabilized PCM plates

A model is developed to analyze the thermal performance of a room applying a new kind of under-floor electric heating system with shape-stabilized phase change material (PCM) plates, which is verified by our experimental data. This system can charge heat by using cheap nighttime electricity and discharge the heat stored at daytime. The thermal performance of the heating system and the effects of various factors on it are analyzed through simulation. The results show that the heating system can be used in various climates if its structure is properly designed. The model and the discussion are helpful to design such kind of under-floor electric heating systems.     

关于电热膜供暖系统的探讨

通过对电热膜供暖系统的介绍 ,就电热膜供暖系统的供电设计和应用中的利弊等方面问题做了进一步分析 ,鉴于电热膜供暖系统的诸多优点 ,指出其必将拥有更广阔的应用前景     

电热地面供暖系统简介

对电热地暖系统进行了介绍，阐述了电热地暖系统的原理、特点及经济性。指出电热地暖系统在未来的供暖工程中具有潜在的发展前景。     

Preparation,thermal performance and application of shape-stabilized PCM in energy efficient buildings

Shape-stabilized phase change material (PCM) is a kind of novel PCM. It has the following salient features: large apparent specific heat for phase change temperature region, suitable thermal conductivity, keeping shape stabilized in the phase change process and no need for containers. The preparation for such kind material was investigated and its thermophysical properties were measured. Some applications of such material in energy efficient buildings (e.g., in electric under floor space heating system, in wallboard or floor to absorb solar energy to narrow the temperature swing of a day in winter) were studied. Some models of analyzing the thermal performance of the systems were developed, which were validated with the experiments. The following conclusions are obtained: (1) the applications of the novel PCM we put forward are of promising perspectives in some climate regions; (2) by using different paraffin, the melting temperature of shape-stabilized PCM can be adjusted; (3) the heat of fusion of it is in the range of 62–138 kJ kg⁻¹; (4) for PCM floor or wallboard to absorb solar energy to narrow the temperature swing in a day in winter, the suitable melting temperature of PCM should be a little higher than average indoor air temperature of the room without PCM for the period of sunshine; (5) for the electric under-floor space heating system, the optimal melting temperature can be determined by simulation; (6) PCM layer used in the aforementioned application should not be thicker than 2 cm; (7) the models developed by us are helpful for applications of shape-stabilized PCM in buildings.     

蓄热式电锅炉供暖工程设计介绍

该工程采用直热式和蓄热式电热锅炉联合供暖方式，介绍了方案选择，设备选型，锅炉运行方式，锅炉房工艺布置和供暖负荷计算。该工程可以充分利用低谷电蓄热供暖，实际运行效果良好。     

新型气动PCM控制系统的试验研究

本对采用三个气源的新型气动控制系统，进行了详细地试验研究，针对试验中出现的问题，提出了一些解决措施，试验结果表明：新型气动ＰＣＭ控制系统能获得±０．３ｍｍ的定位精度，并具有较好的跟踪性能。     

碰撞射流通风供暖房间热环境实测研究

在人工气候室内,对不同送风状态下的碰撞射流通风和混合通风的供暖效果进行了实验研究,分析了送风速度和送风温度对2种通风模式供暖房间热环境的影响,并对室内热舒适性进行了分析比较。结果表明:由于碰撞射流通风热风直接送入房间底部,室内温度梯度小于混合通风模式,并且室内温度分布对送风参数变化的敏感度亦小于混合通风,这对减小建筑供暖能耗有重要意义;尽管碰撞射流在送风口附近的近地面气流速度较大,造成人员吹风感的风险大于混合通风,但在本文研究的送风参数范围内,热环境参数均在可接受的范围内。     

采用超导液的地板电采暖系统的实验研究

阐述了一种采用超导液的地板电采暖系统的工作原理,实验研究和分析了该系统的热性能,并与传统的电热地缆采暖系统进行比较,结果表明,其节能高效,热舒适性好。     

住宅热水支管自控温电伴热系统探讨

支管自控温电伴热是一种相对节能、适用范围较广的住宅热水支管保温方式。本文主要探讨住宅热水支管自控温电伴热系统的特点、自控温及保温的工作原理,并结合工程实例,从管路布置、系统能耗、投资维护等三个方面进行比较分析和提出了相关结论,以供同行交流与参考。     

Energy-economy with electric radiant heating

Direct electric heating is normally considered a ? wasteful ? form of energy use, but this attitude is strongly contested by the author based on experience in Norway and Western Germany. Electric ceiling heating with electronic control gives better response to load demands and exploits the availability of ? free ? heat, he argues.     

钢板加固木梁的试验研究

进行了三种联结方式的钢板加固木梁的抗弯性能试验,分析了其破坏特性、极限荷载、刚度、应变等性能,得出了一些有益的结论,可为实际工程应用提供参考.     

A new PCM storage system for managing simultaneously solar and electric energy

A new hybrid thermal energy storage system (HTESS), using phase change materials, is proposed for managing simultaneously the storage of heat from solar and electric energy. Solar energy is stored during sunny days and released later at night or during cloudy days and, to smooth power demands, electric energy is stored during off-peak periods and later used during peak periods. A heat transfer model of the HTESS is developed and validated with experimental data. Simulations carried out for a period of 4 consecutive winter months indicate that, with such a system, the electricity consumption for space heating is reduced by nearly 32%. Also, more than 90% of the electric energy is consumed during off-peak hours. For electricity markets where time-of-use rate schemes are in effect, the return on the investment in such a thermal storage system is very attractive.     

Experimental study of radiation and free convection in an enclosure with a radiant ceiling heating system

Participation of the radiation and free convection in the heat transferred from the ceiling surface of a room to other internal surfaces has been investigated in this study. A model enclosure representing a room was constructed and equipped with a radiant ceiling heating system. In order to have a thermal map over both internal and external surfaces of the enclosure, 108 elements were specified over the walls, floor and ceiling of the enclosure. Temperatures at both sides of the elements were measured using an infrared thermometer and k-type thermocouples under steady state heat flow condition. Using the measured temperatures, conductive heat transfer through the compartment elements was first calculated. A model based on the net-radiation method was employed to compute the radiation exchanges between internal surfaces of the elements. Convection participation was also specified using radiation and conduction for each element. Based on the results, more than 90% of the heat is transferred by the radiation from the heated ceiling to the other surfaces of enclosure. The participation of the radiation increases slightly as the ceiling temperature is increased.     

Experimental investigation of PCM cold storage

This article presents an experimental analysis of cooling buildings using nighttime cold accumulation in a phase change material (PCM), otherwise known as the “free-cooling principle”. Studies of the ceiling and floor free-cooling principle, as well as passive cooling, are presented. The free-cooling principle is explained and some of the types of PCMs suitable for summer cooling are listed. An experiment was conducted using paraffin with a melting point of 22 °C as the PCM to store cold during the nighttime and to cool hot air during the daytime in summer. Air temperatures and heat fluxes as a function of time are presented for different air velocities and inlet temperatures.     

Experimental study and analysis of air heating system using a parabolic trough solar collector

An experimental study of air heating system was carried out using a parabolic trough collector with a U-tube aluminium heat exchanger. An evacuated tube placed at the focal length of the parabolic trough collected the solar radiations reflected from the surface of parabolic trough. The air was used as a working fluid, which was heated by passing it through a U-shaped aluminium heat exchanger placed inside the evacuated tube. It was found that efficiency of the parabolic trough collector depends on the mass flow rate, solar intensity and use of fins. It was observed that by using fins at a high mass flow rate of 4.557?kg/h, the maximum temperature of 126°C was achieved which is 13.27% more than the maximum temperature obtained without fins. Furthermore, for a low-mass-flow rate of 1.69?kg/h, the maximum temperature obtained was 149°C.     

Experimental study of using PCM in brick constructive solutions for passive cooling

This work presents the results of an experimental set-up to test phase change materials with two typical construction materials (conventional and alveolar brick) for Mediterranean construction in real conditions. Several cubicles were constructed and their thermal performance throughout the time was measured. For each construction material, macroencapsulated PCM is added in one cubicle (RT-27 and SP-25 A8). The cubicles have a domestic heat pump as a cooling system and the energy consumption is registered to determine the energy savings achieved. The free-floating experiments show that the PCM can reduce the peak temperatures up to 1 °C and smooth out the daily fluctuations. Moreover, in summer 2008 the electrical energy consumption was reduced in the PCM cubicles about 15%. These energy savings resulted in a reduction of the CO₂ emissions about 1-1.5 kg/year/m².     

供热锅炉蒸汽湿度的实验研究

通过试验及分析，对供热锅炉蒸汽湿度的测定方法提出了建议，认为可采用开孔取样管装置取样测定饱和蒸汽湿度；当给水用钠离子交换处理时，采用碱度法或氯根法分析均可。所给出的简易测试法为准确测量锅炉热效率提供了方便。     

粘钢加固混凝土梁受剪性能试验研究

通过对11个普通钢筋混凝土（RC）梁试件及4个部分预应力混凝土（PPC）梁试件采用U形钢板箍加固的抗剪试验和数值分析,研究不同损伤程度、剪跨比、配箍率、钢板箍间距、预应力水平、钢板厚度等因素对粘钢加固混凝土梁受剪性能的影响。结果表明：采用U形钢板箍对RC梁进行抗剪加固能够有效抑制斜裂缝的开展,提高加固梁斜截面受剪承载能...     

电供热发展简析

指出电直接供热是能源的低效应用，但可以作为其他供热方式的补充或用于建筑局部供热。认为热泵和电蓄能供热是电供热的发展方向，提出要增强建筑节能和提高供热系统管理水平，倡导冷热电联供和多能源综合利用。     

相变储热轻质围护结构夏季隔热节能的实验研究

采用复合相变材料和聚苯乙烯泡沫板制成了轻质板结构,克服了轻质材料墙体储热能力差的缺陷.在重庆地区对该复合板作围护结构的轻质实验房夏季炎热环境下的隔热及空调节能进行了实验研究,结果表明该相变材料轻质墙体能够有效地利用昼夜温差储放热,有效地阻止热量进入室内,非空调工况下可明显降低室内温度,具有较好的节电效果.