散热器和低温水辐射采暖系统不同连接方式及控制策略动态仿真

散热器和低温水辐射采暖系统最佳连接方式一直是业界探讨的重要课题之一。本文以动态模型为手段,模拟和分析直接、混水泵及间接连接方式系统动态响应和能耗。仿真结果表明,地板热情性的提高延长了室内温度达到稳态时间;地暖系统直接连接方式是不适宜的;混水泵和间接连接系统可节省燃料消耗约17％。从控制角度看,间接连接系统具有更好的稳定性和控制精度。     

Experimental studies on the indoor electrical floor heating system with carbon black mortar slabs

A room using carbon black mortar slabs (CBMS) as the electrical floor heating element has been built in our lab. Studies showed that an electrical power of about 123.8 W/m² resulted in the indoor temperature rise of 10 °C within 330 min. Temperature distribution along the height of the room was uniform. Temperature rise was slightly higher if floor tiles rather than the wood flooring was used. In the process of heating, self-heating of CBMS has consumed more than 30% of the generated heat by Joule effect, which was advantageous for the stability of the thermal state. The indoor air absorbed over 50% of the generated heat. Results derived from repeated tests show that the electrical power of the CBMS system was stable during several cycles of heating. Further, the procedure and power consumption for the system to maintain a certain indoor temperature were studied. Continuous tests for 72 h has shown that the higher the indoor controlled temperature was, the longer the working time and the shorter the rest time in every cycle of heating were required. Accordingly, the power consumption to maintain the heat state increased with the controlled temperature increasing.     

Design of an individually controlled system for an optimal thermal microenvironment

Individually controlled microenvironment has potential to satisfy more occupants in a space compared to a total volume uniform environment typically used at present. The performance of an individually controlled system comprising a convection-heated chair, an under-desk radiant heating panel, a floor radiant heating panel, an under-desk air terminal device supplying cool air, and a desk-mounted personalized ventilation as used and identified by 48 human subjects was studied using a thermal manikin at room temperatures of 20 °C, 22 °C and 26 °C. At a room air temperature of 20 °C, the maximum whole-body heating effect of the heating chair, the under-desk heating panel, and the floor heating panel corresponded to the effect of a room temperature increase of 5.2 °C, 2.8 °C, and 2.1 °C, respectively. The effect was 5.9 °C for the combination of the three heating options. The higher the room air temperature, the lower the heating effect of each heating option or heating combination. The maximum whole-body cooling effect of the tested system was only −0.8 °C at a room air temperature of 26 °C. The heating and cooling capacity of the individually controlled system were identified. These results, analyzed together with results obtained from human subject experiments, reveal that both the heating and the cooling capacity of the individually controlled system need to be increased in order to satisfy most occupants in practice.     

地板辐射与散热器供暖系统经济性分析

对两种供暖系统进行了初投资和年运行费用比较,同时对其各自的优缺点进行了分析,在肯定了低温地板辐射供暖系统的优点后,得出了散热器供暖系统经济性优于地板辐射供暖系统的结论。     

散热器对流采暖与地板辐射采暖的比较分析

对散热器对流采暖与地板辐射采暖的散热机理、室内温度的垂直分布、对室内风速分布的影响以及对建筑节能的作用等进行了分析,指出了地板辐射采暖优于传统散热器对流采暖。     

Floor heating and cooling combined with displacement ventilation: Possibilities and limitations

Design guidelines envisage that floor heating can be used together with displacement ventilation (DV), provided that the supply air is not overly heated before it can reach heat and contaminant sources. If this is not controlled a mixing flow pattern could occur in the room. The use of floor cooling with DV is also considered possible, although draught risk at ankle level and vertical air temperature differences must be controlled carefully, because they could increase.Few studies on these topics were found in the literature.An indoor environmental chamber was set up to obtain measurements aimed at analysing the possibilities and limitations of combining floor heating/cooling with DV. Air temperature profiles, air velocity profiles, surface temperatures and ventilation effectiveness were measured under different environmental conditions that may occur in practice. These values were compared to equivalent temperature measurements obtained using a thermal manikin.The measurements show that floor heating can be used with DV, obtaining high ventilation effectiveness values. A correlation between the floor heating capacity and the air temperature profile in the room was found. Measurements showed that floor cooling does not increase draught risk at ankle level, although it does increase vertical air temperature differences.     

Heat emission from thermal skirting boards

The performance of three hydronic skirting heating systems was investigated. The main focus of the study was to ascertain whether thermal skirting boards served by low-temperature supply flow were able to suppress strong downdraught. The evaluation was made for a two-person office room with mechanical ventilation. Computational Fluid Dynamics (CFD) simulations and three different draught rating models were employed to predict the level of thermal discomfort inside the room. CFD results were validated against several analytical calculations and four sets of experimental data presented in previous studies. Numerical simulations showed that all three skirting heating arrangements were able to cover transmission and ventilation thermal losses of the office room. Horizontal and vertical heat distribution inside the room was uniform for all heating systems. CFD simulations also showed that thermal skirting boards served by 40 and 45 °C supply flow had difficulty in reducing the velocity of the downdraught at ankle level. Consequently the draught rating in this region was around or slightly above 15% for these cases. In contrast, heat-emitting skirting boards supplied by 55 °C hot water showed a better ability to suppress downdraught, and the proportion of people sensing draught at 0.1 m above the floor was low. The conclusion of this study was that thermal performance of hydronic skirting heaters with low-temperature water supply must be improved in order to counter strong downdraughts, in particular where such systems may be combined with heat pumps of other low-valued sustainable energy sources.     

Flow patterns and thermal comfort in a room with panel,floor and wall heating

Thermal comfort aspects in a room vary with different space heating methods. The main focus in this study was how different heating systems and their position affect the indoor climate in an exhaust-ventilated office under Swedish winter conditions. The heat emitters used were a high and a medium–high temperature radiator, a floor heating system and large wall heating surfaces at low temperature. Computational fluid dynamics (CFD) simulations were used to investigate possible cold draught problems, differences in vertical temperature gradients, air speed levels and energy consumption. Two office rooms with different ventilation systems and heating needs were evaluated. Both systems had high air exchange rates and cold infiltration air.     

Design considerations with ventilation-radiators: Comparisons to traditional two-panel radiators

Performance of heat emitters in a room is affected by their interaction with the ventilation system. A radiator gives more heat output with increased air flow along its heat transferring surface, and with increased thermal difference to surrounding air. Radiator heat output and comfort temperatures in a small one-person office were studied using different positions for the ventilation air inlet. In two of the four test cases the air inlet was placed between radiator panels to form ventilation-radiator systems. Investigations were made by CFD (Computational Fluid Dynamics) simulations, and included visualisation of thermal comfort conditions, as well as radiator heat output comparisons. The room model was exhaust-ventilated, with an air exchange rate equal to what is recommended for Swedish offices (7 l s⁻¹ per person) and cold infiltration air (−5 °C) typical of a winter day in Stockholm.Results showed that under these conditions ventilation-radiators were able to create a more stable thermal climate than the traditional radiator ventilation arrangements. In addition, when using ventilation-radiators the desired thermal climate could be achieved with a radiator surface temperature as much as 7.8 °C lower. It was concluded that in exhaust-ventilated office rooms, ventilation-radiators can provide energy and environmental savings.     

四种供暖方式的分析比较

对目前使用的散热器供暖、地板供暖、天花板和踢脚板供暖方式的室内温度场和流场作了数值模拟,定量分析了上述供暖方式的特点和对室内热环境的影响,认为踢脚板供暖方式的室内温度场和流场相对均匀,其次是地板供暖、天花板供暖和散热器供暖方式。     

太阳辐射照度对供暖热过程影响研究

模拟了低温地板辐射供暖与对流散热器供暖系统在不同太阳辐射照度下的动态热过程.对比了室内温度及供暖耗热量等指标,结果表明在高太阳辐射照度地区地板辐射供暖系统室内过热现象更明显,地板辐射供暖能耗与散热器供暖能耗比值随太阳辐射照度的增大而增加,因此选择高太阳辐射照度地区的供暖形式时应优先采用热响应较快的散热器供暖形式.     

新建居住建筑采暖节能小议

阐述了新建居住建筑采暖的两种基本形式：双立管水平串联式散热器采暖系统和低温热水地板辐射采暖系统,介绍了居住建筑采暖节能的主要方向和措施,以实现节约能源的目的。     

间歇供暖负荷计算方法研究

以夏热冬冷地区、寒冷地区和严寒地区典型城市的居住建筑和办公建筑为研究对象,分别采用DeST和DesignBuilder软件模拟分析了围护结构、换气次数及散热器和地板辐射两种供暖方式对间歇供暖热负荷的影响,给出了间歇供暖相对于连续供暖的供暖热负荷附加率,确定了合理的间歇供暖模式。结果显示,窗墙面积比对间歇供暖热负荷的影响可以忽略;换气次数每增加0.5h-1,间歇供暖热负荷附加率约增加5%;采用地板辐射供暖的间歇热负荷附加率比散热器供暖小3%～10%。     

两种采暖方式室内温度稳定性分析

通过分析影响室内温度变化的各因素,间歇供暖的变室温热过程,对采用地板辐射采暖和散热器对流采暖方式的典型房间,建立房间围护结构内表面热平衡方程和室内空气热平衡方程,用Visual Basic语言编制计算程序,利用高斯-约当消去法进行线性方程组的求解,得到了不同室外空气温度、间歇供暖的不同供暖时间下各种典型房间的室内空气温度,进而得到一系列室温波动曲线。     

Evaluation and comparison of thermal comfort of convective and radiant heating terminals in office buildings

Radiant heating systems are increasingly widely utilized in buildings for its energy conservation potential and enhanced thermal comfort. This paper presented an experiment to compare the thermal comfort performance of radiant heating system with convective heating system through objective measurement and subjective survey. Six physical parameters which might influence occupants' thermal satisfaction, including the Mean Radiant Temperature(MRT), humidity, air movement, A-weighted sound level,temperature fluctuation and vertical temperature difference, were measured. In addition, 97 subjects participated in the subjective survey part of this experiment, experiencing all the three environments heated by air source heat pump, radiator and floor heating.And they were asked to vote in six thermal comfort related aspects, i.e. thermal sensation, humidity, draught, local discomfort,overall thermal satisfaction and overall preferences, plus the acoustic environment, since the operation noise of heating system might lead to complains of the occupants. It was found that in continuous heating, no significant difference between radiant and convective heating system was observed in the Mean Radiant Temperature(MRT), indoor humidity and noise issue. Though radiant heating systems resulted in lower draught risk and less local discomfort complains in the feet region due to the less significant temperature fluctuations and vertical temperature gradients, radiant heating did not have significantly higher overall thermal satisfaction votes and was not significantly more preferred by occupants.     

集中供热系统二次网供暖参数优化研究

目前我国集中供热系统的二次网供回水温度存在设计参数高、运行参数低的现象,同时集中供热系统应用形式呈现出多样性的特点。如何在不同的燃料价格和设备基价背景下,优化选择二次网供暖设计参数值得深入研究。调研了国内外集中供热系统的二次网供暖设计参数和我国部分城市二次网供暖运行参数情况,建立了二次网供暖设计参数影响集中供热系统技术经济性的分析模型,通过模拟分析得出了散热器和地面供暖系统的二次网供暖优化设计参数。     

Application of the control methods for radiant floor cooling system in residential buildings

In applying radiant floor cooling, its control system must prevent the floor surface condensation in hot and humid weather conditions. With no additional dehumidification system, only the radiant floor cooling system prevents floor condensation. In this case, the effects of the control of the cooling system on the indoor conditions can be changed because of the thermal inertia of the systems. Also different types of control system can be composed according to the control methods, which can affect the construction cost in the design stage. Therefore, the control methods for the radiant cooling system with respect to floor surface condensation must be studied. Furthermore, because Korean people's lifestyle involves sitting on the floor, it is necessary to evaluate if a floor cooling system will influence the thermal comfort of the occupants. This study intends to clarify the control methods of the radiant floor cooling system and to analyze the control performance and applicability of each control method with regard to the floor surface condensation and comfort by computer simulations and experiments on the control methods of the radiant floor cooling system. The results of computer simulations and experiments show that water temperature control is better than water flow control with respect to temperature fluctuations in controlling room air temperature. To prevent floor surface condensation, the supply water temperature could be manipulated according to the dew point temperature in the most humid room, and in individual rooms, the water flow rate (on/off control) can be controlled. Also, the results of radiant cooling experiments show that the floor surface temperature remained above 21 °C, the temperature difference among surfaces remained below 6 °C, and the vertical air temperature difference remained below 1.9 °C, conforming well to comfort standards.     

Performance evaluation of a hybrid photovoltaic thermal double pass facade for space heating

This paper presents the performance evaluation of a hybrid photovoltaic thermal (Semi transparent PVT) double pass facade for space heating. The thermal model has been developed by using the energy balance equations of the proposed hybrid photovoltaic thermal double pass facade under quasi-steady state condition. Numerical computations have been carried out for the composite climate of New Delhi, India. An analysis has been carried out to calculate annual energy and exergy gain for the hybrid photovoltaic thermal double pass facade. On the basis of numerical results it has been observed that the annual thermal and electrical energy are 480.81 kWh and 469.87 kWh respectively. The yearly overall thermal energy generated by the system has been calculated as 1729.84 kWh. It is also observed that the room air temperature increases by 5-6 °C than the ambient air temperature for a typical winter day.     

地板辐射采暖与风机盘管采暖实验对比研究

为了考察低温热水地板辐射采暖在成都地区的应用效果,进行了地板辐射采暖和盘管对流采暖对比实验。结果表明,地板采暖空气竖向温、湿度梯度小,热量传递以辐射换热为主,辐射散热量占59.8%,在相同工况下,地板采暖的有效采暖时间是盘管采暖的2.7倍,地板采暖既舒适,也更经济节能。该对比实验研究为低温热水地板辐射采暖在夏热冬冷地区的推广应用提供了一定的依据。     

热水地面供暖与散热器分户计量供暖对比分析

从室内空间、加热能力、初投资、动态调节、热舒适性等方面，对比分析了热水地面供暖与散热器供暖存在的差异，指出热水地面供暖具有的一些天然优势，更适宜分户计量供暖的推广。