Thermal comfort in environments with different vertical air temperature gradients

The use of displacement ventilation for cooling environments is limited by the vertical temperature gradient. Current standards recommend a temperature difference of up to 3 K/m between the head and the feet. This paper reviews the scientific literature on the effect of vertical temperature gradients on thermal comfort and compares this to the results of our own experiments. Early experiments have demonstrated a high sensitivity of dissatisfied test subjects to changes in the temperature gradient between head and foot level. Recent studies have indicated that temperature gradients of 4‐5 K/m are likely to be acceptable, and the mean room temperature may have a greater sensitivity on the percentage of dissatisfied (PD). In new experiments, test subjects have evaluated the thermal comfort of different vertical air temperature gradients in a modular test chamber, the Aachen comfort cube (ACCu), where they have assessed vertical temperature gradients of ΔT/Δy = 1, 4.5, 6, 8, and 12 K/m at a constant mean room temperature of 23°C. The results of the different temperature gradients are in contrast to ANSI/ASHRAE Standard 55 (Thermal Environmental Conditions for Human Occupancy, Atlanta GA, American Society of Heating, Refrigerating and Air Conditioning Engineers, 2013) as the PD increases almost constantly with higher vertical air temperature gradients. The PD for the overall sensation increases by approximately 7% between gradients of 1 and 8 K/m. The evaluation of our own tests has revealed that vertical temperature gradients of up to 8 K/m or higher are likely to be acceptable for test subjects.     

地板送风空调房间数学建模及仿真

结合室内热力分层特性,将地板送风空调房间模型分为2个方面来建立:其一,以能量守恒原理为基础,建立了地板送风空调的黑箱模型,并利用阶跃响应实验确定了房间传递函数的各项参数;其二,在黑箱模型基础上考虑温度分层特性,结合房间的温度经验关系式,建立具有分层特性的地板送风空调房间数学模型。通过MATLAB Simulink进行控制建模及仿真,并利用仿真模型对实验的2种负荷工况进行仿真计算。仿真结果与实验结果吻合较好。     

下送风空调技术原理及应用探讨

本文针对下送风空调的两种主要形式——置换通风和地板送风就其各自工作原理、室内空气分布特性、优点及存在问题等进行了分析比较,并对两种空调送风方式的适用性进行了分析,为合理设计和采用下送风技术提供参考。     

地板送风技术条件与舒适条件的研究

本文阐明了下部送风房间热力分层和垂直温度分布规律，给出了确定垂直温度分布曲线的方法及确定最佳送风量的原理。为了计算冷负荷，作者初步推荐了不同位置热源的负荷系数，并且说明了如何决策送风口的型式与数量和相关数据。最后在实验基础上分析了地板空调的热感觉，其结果说明这种送风系统在适宜的风量与温度下能够提供舒适条件，并使风感百分数低于１５％。     

地板送风与置换通风的差异

探讨了地板送风和置换通风两种下送风方式在概念、机理、主要功能、特性及应用等诸多方面的差异与联系，分析比较了各自的优越性及局限性，提出了地板送风和置换通风各自的适用范围。地板送风作为一种节能空调系统应同时处理好通风换气和温度控制功能；置换通风由于加热和除湿问题，其应用在一定程度上受到了限制，但只要将其应用在恰到好处的场合，也可发挥出优势。     

下送风气流组织影响因素的实验研究

通过人体热舒适试验，分析得出下送风气流组织的4个主要因素即送风口形式、送风口到人体的距离、送风速度、送风温度等对人体热舒适的影响，确定了其合理的取值范围，为下送风气流组织的设计提供了参考依据。     

置换通风热力分层高度的数值研究

根据置换通风系统的工作原理,介绍了置换通风热力分层高度的定义及数值计算方法,并对送风温度、送风速度等因素对热力分层高度的影响作了定性分析.在此基础上拟合出量纲一热力分层高度的经验公式.     

办公室下送风空调方式的应用

随着办公自动化设备的开发与应用，新型办公楼室内布避的变化以及智能建筑的出现，国外下送风空调方式的采用逐渐增加。从这种空调方式的原理出发，综述了国外主要是日本对其在实验室进行的各种测试以及在若干实际工程中的设计研究和应用情况，介绍了这种系统在热环境、空气品质、节能等方面的特点。     

办公楼地板送风系统应用与研究现状

就地板送风的系统特点、室内气流分布、热舒适与室内空气品质、送风静压层的性能、室内冷负荷和风机能耗等方面介绍了国内外的研究现状。指出有待于进一步研究的一些方面。     

办公建筑中旋流风口地板送风系统的设计及实验研究

基于地板送风与置换通风原理的相似性,参考办公室中置换通风的设计方法,结合旋流风口地板送风系统的特性,提出旋流风口地板送风系统的设计方法。通过实验对设计方法进行了验证,并对室内热舒适性进行了评价。     

置换通风几个问题的讨论

分析了讨论下部送风与置通风的关系,热力分层高度的计算财面空气层温升与工作区温升的确定,送风量计算等问题。     

排风口在辐射空调中对于室内热舒适性的影响

以气流组织为研究对象,结合实际工程对有排风口和无排风口的辐射空调系统进行了测试比较,从室内热舒适角度考虑,得出了加设排风口对室内气流温度场和速度场是有影响的。     

置换通风系统室内温度分布的实验研究

实验研究了置换通风系统送风参数和环境参数对室内温度场分布特性的影响.测量了不同送风量、送风温度和夹层空气温度下室内不同测点及人体不同部位上的竖直温度分布,并将实验值与CFD模拟结果进行比较,结果表明二者吻合较好.不同参数条件下的实验结果表明,随着送风量的增大,热分层高度相应提高,但送风量达到一定值后,其对竖直温度梯度的影响明显减小;送风温度的变化只对室内整体温度产生影响,而几乎不影响室内温度梯度;夹层空气温度的升高对室内下部温度影响不大,而上部区域温度升高明显.     

地板送风系统中无量纲数对室内CO2浓度的影响

本文对地板送风系统进行数值模拟,通过分析室内温度场、速度场以及不同工况下CO2浓度随空间高度的变化,结果表明不同工况下的CO2排除效率有所不同,通过比较热长度尺度Lm/H和阿基米德数Ar与CO2排除效率的关系曲线,指出热长度尺度Lm/H与阿基米德数Ar都与分层高度有关,当阿基米德数Ar越小,CO2的排除效率变化越明显,当阿基米德数Ar很大的时候,CO2的排除效率几乎不变;而热长度尺度Lm/H不论变大还是变小,其CO2的排除效率都变化很明显。     

地板辐射与置换通风空调系统运行参数

建立了基于EnergyPlus的地板辐射供冷加置换通风空调系统模型,模拟得到的室内温度和辐射地板所承担冷量与实验结果的误差小于±7%。在此模型基础上,改变送风参数和供水参数,得到置换通风供冷量、辐射地板供冷量、地板表面温度、室内空气平均温度、AUST温度等参数的变化规律。结合热舒适性模型,得到满足室内热舒适性(-0.5≤PMV≤0.5)条件下,置换通风的送风参数和辐射地板的供水参数范围,为复合系统设计和应用提供依据。     

置换通风与冷却顶板

介绍了冷却顶板和置换通风的基本原理，以及两者在提高人体热舒适性和室内空气品质方面的优越性，并指出两者的结合使用可带来明显的节能效果。     

Thermal pleasure in built environments: spatial alliesthesia from air movement

In recent years there has been a shift in research focus away from the negative effects of draught towards the positive benefits of air movement, particularly in the context of personal environmental control (PEC) systems. Thermal perception under targeted air movement is different from exposures in airflow uniformly distributed across the body, but is less well understood. Specification of performance criteria for PEC systems remains unresolved, as there are no clear conclusions regarding optimum target area, velocity ranges or patterns of velocity dynamics. This paper examines the effects of different local air-velocity profiles on thermal sensation and thermal pleasure experienced by human subjects near the upper boundary of the comfort zone, and interprets the findings within the theoretical framework of spatial alliesthesia. It was found that positive thermal pleasure can be achieved when contrasting relationships between local and global skin temperatures trends are established. The substantial body of research literature on local thermal discomfort can be coherently interpreted within the theoretical framework of spatial alliesthesia; local discomfort represents thermal alliesthesia with the incorrect polarity between local and global thermal states. Spatial alliesthesia therefore provides a conceptual framework to understand PEC systems and their potential to minimize occupant thermal dissatisfaction.     

基于小空间多工况的层式通风热舒适性研究

层式通风自2005年提出以来成为众多学者的研究对象,相关机构有针对性地进行各种试验。层式通风与传统的数种通风方式有所区别。基于已经开展的多种工况下小空间层式通风实验比较分析可知,层式通风相较其他数种通风方式,达到同样热舒适性(温湿度、CO2浓度、空气质量)能耗更少,空气质量也更好。本研究特别针对换气次数进行了能耗、热舒适性和空气品质研究,据此也得出需进一步深入研究层式通风的热舒适性以及高大空间、半室外空间不同工况的应用研究。     

Chilled ceiling and displacement ventilation aided with personalized evaporative cooler

This paper aims at studying the energy impact of a chilled ceiling displacement ventilation CC/DV system aided with a personalized evaporative cooler (PEC) directed towards the occupant trunk and face. A simulation model is developed for integrating the personalized cooler with the ascending thermal plume. The thermal model of the conditioned room air around the person is integrated with a segmental bioheat and thermal comfort model to predict the human thermal comfort.The model is validated with experimental data on the vertical temperature distribution in the room, and the recorded overall comfort perceived by surveyed subjects. Experimental results agreed well with predicted values of temperature and comfort level. When using personalized cooling, the DV supply air temperature can be as high as 24 °C while the PEC at flow rates of 3–10 l/s achieved similar comfort with a DV system at supply temperature of 21 °C. At equal thermal comfort level, the integrated CC/DV system, PEC model resulted in up to 17.5% energy savings compared to the CC/DV system without a PEC. When mixed air is used in the CC/DV system additional 25% savings in energy is realized when compared with energy used for the 100% fresh air without the PEC.     

风口侧上置置换通风的热舒适性实验研究

以小型办公室为实验模型,采用了5组对比工况进行了实验,并将实验值与模拟值进行了比较,结果二者吻合较好。分析了侧墙上置风口置换通风的热舒适性。结果表明风口侧上置置换通风在各设计工况下,其负荷承担能力要大于传统置换通风,并且不论是吹风感、吹风温度还是室内头脚垂直温差都满足人体热舒适。这也证实风口上置置换通风与传统置换通风一样,可以在室内形成良好的热力分层现象,并且其能很好地满足人体的热舒适性需求,具有置换通风系统的特性。