对流强化式辐射板实验与性能分析

测试了一种对流强化式辐射板的供冷性能,分析了其供冷量的影响因素,具体计算了辐射板与各个表面的辐射换热量,与周围空气的对流换热量及表面传热系数。分析计算了该辐射板在不同温度环境中的供冷量。     

高大空间空气载能辐射末端热环境与传能研究

本文以内设空气载能辐射空调系统的某火车站候车厅为研究对象,利用FLUENT数值模拟的方法,分析研究了房间人体活动区域内空气工况参数和系统传能过程。模拟结果显示,该房间室内空气温湿度分布较均匀,未出现结露现象。且在传能过程中,系统总冷负荷约为119 KW,空气载能辐射空调系统承担92%的冷负荷;其中,辐射换热占房间总负荷64.2%,对流换热占29.1%,由此可得系统以辐射换热为主;相较于金属平板辐射空调系统,该系统新增的对流换热量包括载能空气与辐射孔板间的对流换热量以及循环流动的交换能量;经计算,在相同模拟条件下,该系统总换热量较金属平板辐射空调系统超出约10%以上。综上,该系统在理论上基本符合高大空间建筑夏季负荷大,强调舒适节能的要求。     

采用周线积分法计算人体与辐射板的辐射角系数

辐射角系数是计算人体与辐射板间辐射换热量的一个重要参数,针对人体与辐射板之间辐射角系数问题求解的复杂性,使用长方体模型代替站立姿态时的人体形状,进行辐射角系数的计算。以辐射顶板为例,运用周线积分法和代数法建立了任意位置下人体与辐射板之间辐射角系数的数学表达式,并对结论的合理性进行了验证。     

陶瓷板红外线燃气灶节能效果的分析

分析了陶瓷板红外线燃气灶热效率比大气式燃气灶高的原因：具有陶瓷板辐射体，辐射效率高；燃气燃烧需要的过剩空气系数小，致使理论燃烧温度高，增强了换热，减少了排烟损失；锅支架高度小，有利于增加换热量和减小向周围的辐射散热损失。     

干式地板辐射供冷结合置换通风复合式系统实验研究

本文针对干式地板辐射供冷结合置换通风复合式系统进行了实验研究,测量了从系统开启到关闭的室内温度、地板表面温度、围护结构表面温度等参数,分析了系统运行过程中地板表面温度、距地面0.1 m处空气露点温度和湿度、系统换热量、温度场和湿度场以及热舒适性变化.结果表明:置换通风系统的引入可有效地避免地面结露;系统稳定运行时,室内空气温度在竖直方向分布均匀;辐射换热量占总换热量的27.8%;水系统提供的辐射换热量有限,系统稳定时,热舒适性较差,这是由于系统供水温度偏高引起的,可通过降低供水温度得到改进.     

电加热辐射地板传热特性的实验研究

本文利用组合式电热辐射板实验研究了电加热地板采暖辐射板内的传热特性。研究结果表明:辐射板的结构材料及其物性参数对表面温度分布和采暖能耗具有重要的影响。即使在实验条件下加热板内各层温度,使其呈周期性波动,但室内地板表面温度分布仍然非常均匀。在辐射板的热量损失中,通过辐射板下表面的损失热量接近辐射板全部的热量损失。     

室内遮挡物条件下人体对壁面角系数简化算法

辐射角系数的求解是研究人体与各辐射壁面换热量的关键.由于人体形状复杂,计算人体与辐射面的角系数较困难.并且在对辐射空调房间进行热舒适评价时,家具、屏风等遮挡的影响不可忽略.本文将人体简化为立方体,提出遮挡条件下,人体对壁面角系数的简化算法.将计算结果与CFD模拟结果进行对比,误差小于10％.绘制出无遮挡时人体与壁面角系...     

顶棚辐射结合下送风供冷系统运行特性实验研究

本文基于对室内温度、围护结构内表面温度、风口参数等实测数据,分析了顶棚辐射结合下送风供冷系统运行过程中系统换热量、人体热舒适性变化规律,以及操纵量、扰动量对被控量的影响。研究结果表明:系统净辐射换热量、对流换热量和总换热量在系统开启的前1.5 h内递增,之后趋于稳定,系统稳定时,辐射换热量占总换热量的43%,余下57%冷量由风系统承担,此时,PMV和PPD值均在ISO7730的推荐值范围内。室内空气温度和作用温度随着扰动量和操纵量的增加而增加;当室外空气温度相对较低或较高时,室内发热量或平均水温较低时,室内空气温度和作用温度的增加率较小;室内空气温度和作用温度随着送风温度呈近似线性增加。     

空气源热泵“三联供”机组节能分析

空气源热泵"三联供"机组(供冷、供暖、供热水)可将通常空调在制冷时往外排放的废热加以回收利用,制成生活用热水,减少了热量向空气中的排放。单供热水将机组切换到制热模式,此时机组两板换产生的都是热水。机组工作,压缩机启动,高温高压工质通过第一个板式换热器,工质在板换内冷凝,放出热量,被板换里的水吸收,作为生活用热水。同时,经过第一板换的工质还有部分热量,通过四通     

新型装配式辐射供冷顶板性能的数值模拟研究

为提高装配式辐射顶板的供冷性能,本文建立了一种采用特殊气体层进行热量交换的新型直接蒸发式防凝露辐射供冷顶板的传热模型,利用CFD数值模拟的研究方法,分析了不同管间距,气体层厚度,管径大小,制冷剂流速及蒸发温度对辐射顶板供冷性能的影响.研究表明:随着管间距,气体层厚度的增大及管径的减小,辐射板供冷能力呈下降趋势.当结构参...     

辐射板供冷性能影响因素与计算方法

通过对现有计算方法的分析,提出了以室内等效辐射温度作为辐射换热计算参数的方法。通过实例计算定量地分析了室内热源环境对辐射板供冷能力的影响。提出将辐射板热阻作为衡量辐射板供冷性能优劣的参数。     

Evaluating the low exergy of chilled water in a radiant cooling system

In this paper, in order to make guidelines for designing a low-energy radiant cooling system with an air-handling unit (AHU) for dehumidification, we investigated the impact of various air-conditioning parameters on the exergies of chilled water supplied to radiant panels and a cooling coil. The cooling load, thermal comfort index PMV, relative humidity, area of radiant panels, sensible heat factor (SHF), temperature and air-flow rate of supply air of the AHU, and presence/absence of total heat exchanger were considered. We used computational fluid dynamics (CFD) code in order to analyze the indoor air-flow and thermal environments, and added models for the calculation of thermal transfer to radiant panels and a cooling coil. Furthermore, a feedback control algorithm was introduced to calculate the surface radiant panel temperature, targeting the average PMV of the task area in an office room. As a result, the impact of various air-conditioning parameters on the exergies of chilled water were demonstrated quantitatively. As an example, by reducing the cooling load rate from 100% to 57% and 27%, the exergy of chilled water decreased by 47% and 67%, respectively.     

新风除湿辅助毛细管辐射供冷房间流场模拟

建立毛细管辐射供冷系统传热模型。对分别采用单纯毛细管辐射供冷系统、新风除湿辅助毛细管辐射供冷系统的空调房间内的温度场、速度场进行模拟。采用新风除湿辅助毛细管辐射供冷系统,室内可达到更为舒适的温度范围,在工作区内无吹风感。     

地板辐射供冷-置换通风的实验研究

为了研究地板辐射供冷的热工性能,测试了北京地区不同室外气温下地板辐射供冷系统的运行工况,得到了该系统的制冷量,地板表面温度,室内温度场分布等参数,并且把单独地板辐射供冷系统的运行参数与地板辐射供冷-置换通风复合式系统进行了对比,提出了将地板辐射供冷与置换通风配合用于夏季空调室内供冷除湿的新型空调方式,置换通风系统在近地面处形成干燥空气层,可有效防止夏季热湿天气在地板表面出现结露现象,并且使这种新型空调系统条件下地面与室内的换热得到强化.通过理论分析和实验研究指出这是一种舒适、节能的空调方式.     

基于蒸发冷却的地板辐射供冷能力探讨

基于蒸发冷却的地板辐射供冷空调系统供冷能力,从其主要影响因素的管间距和覆盖层传热阻进行对比分析,进而指出其供冷能力的变化规律,同时结合了工程实例进一步阐明了该供冷能力变化规律在工程设计中的具体应用,以期使更多的工程设计人员了解该新型复合式空调系统的特性及设计思路,为工程设计人员提供有益的参考.     

Numerical simulation of radiant floor cooling system: The effects of thermal resistance of pipe and water velocity on the performance

Using the existing floor heating system, the radiant floor cooling system can be used as an alternative to the conventional all-air cooling systems. In this paper, a numerical model for the radiant floor cooling system is built using finite volume method. The objective of this study is to research the effects of the thermal resistance of pipe and water velocity on the performance of the radiant floor cooling system. In order to provide better heat transfer simulation in the pipe, composite grids are used in the model. The numerical floor surface temperature and the heat flux are in agreement with the measured results. The results illustrate that the pipe has effect on the performance of the radiant floor cooling system when the thermal conductivity of the pipe is low. However, the effect of the water velocity on the performance of the cooling system is not great. The model is helpful to calculate and design such kind of radiant floor cooling systems.     

A quasi-steady-state model of attic heat transfer with radiant barriers

During the cooling season, heat transfer from the attic into the conditioned space of a residence can represent a significant portion of the total envelope heat transfer. Radiant barriers are one method used to reduce this heat transfer. A quasi-steady-state model was developed for predicting attic heat transfer in residences with radiant barrier systems. The model was used to estimate the reduction in cooling load that would occur with a radiant barrier and to identify important construction and environmental parameters that influence this cooling load reduction. The model's output consisted of hourly ceiling heat fluxes inside the house based on hourly weather data inputs. Model results were compared with detailed experimental results from two small test houses. The model predicted typical summer heat flux reductions of between 35 and 43% with different radiant barrier configurations and levels of insulation. These compared to measured heat flux reductions of between 29 and 37% in attics under the same conditions. Sensitivity studies were also conducted to show the effect of uncertainty in several of the important physical attic parameters on the final heat flow predictions of the model.     

辐射空调冷负荷算法和传统谐波法对比研究

由于辐射空调在舒适性上的优越性,在工程上运用越来越多。在计算其冷负荷时,工程师普遍使用传统的空调冷负荷计算方法。而辐射空调与传统供冷房间存在着传热机理和系统形式的差异,所以传统负荷计算方法不一定适用于辐射空调。首先通过提供一种辐射供冷房间冷负荷计算方法,并通过实验进行验证其合理性,然后对该方法和传统谐波反应法冷负荷计算方法进行模拟对比分析。     

Experimental investigation of the influence of the air jet trajectory on convective heat transfer in buildings equipped with air-based and radiant cooling systems

The complexity and diversity of airflow in buildings make the accurate definition of convective heat transfer coefficients (CHTCs) difficult. In a full-scale test facility, the convective heat transfer of two cooling systems (active chilled beam and radiant wall) has been investigated under steady-state and dynamic conditions. With the air-based cooling system, a dependency of the convective heat transfer on the air jet trajectory has been observed. New correlations have been developed, introducing a modified Archimedes number to account for the air flow pattern. The accuracy of the new correlations has been evaluated to±15%. Besides the study with an air-based cooling system, the convective heat transfer with a radiant cooling system has also been investigated. The convective flow at the activated surface is mainly driven by natural convection. For other surfaces, the complexity of the flow and the large uncertainty on the CHTCs make the validation of existing correlations difficult.