One of the most critical variables in the field of thermal comfort measurements is the mean radiant temperature which is typically measured with a standard 150 mm black globe thermometer. This is also the reference instrument required for the assessment of heat stress conditions by means of the well-known Wet Bulb Globe Temperature index (WBGT). However, one of the limitations of this method is represented by the relatively long response time. This is why in recent years there has been a more and more pressing need of smart sensors for controlling Heating Ventilation and Air Conditioning (HVAC) systems, and for pocket heat stress meters (e.g., WBGT meters provided with table tennis balls). Although it is widely agreed that there is a clear advantage of small probes in terms of response times, their accuracy is a still a debated matter and no systematic studies aimed at metrologically characterizing their performances are actually available, due to the difficulty of reproducing measuring conditions such as a black enclosure at uniform temperature. In this paper the results of a metrological analysis of two small globes (38 and 50 mm diameter) carried out by means of an experimental apparatus specifically designed to reproduce a black uniform enclosure are presented and discussed. Experimental results revealed a systematic underestimation of the mean radiant temperature predicted by small globes of more than 10 °C in forced convection and at high radiative loads.

中文翻译：

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强制对流条件下通过小黑球的平均辐射温度测量

在热舒适性测量领域中，最关键的变量之一是平均辐射温度，该温度通常是用标准的150毫米黑球温度计测量的。这也是通过众所周知的湿球温度指数（WBGT）评估热应力条件所需的参考仪器。但是，该方法的局限性之一是响应时间相对较长。这就是为什么近年来越来越需要智能传感器来控制加热通风和空调（HVAC）系统以及袖珍热应力计（例如，配备有乒乓球的WBGT计）。尽管人们普遍认为小探针在响应时间方面有明显的优势，它们的精度仍是一个有争议的问题，由于难以再现测量条件（例如在均匀温度下的黑色外壳），因此实际上尚无法进行旨在对其性能进行计量表征的系统研究。本文介绍并讨论了通过专门设计用于再现黑色均匀外壳的实验设备对两个小球体（直径分别为38和50 mm）进行的计量分析结果。实验结果表明，在强制对流和高辐射负荷下，超过10°C的小球所预测的平均辐射温度被系统低估了。由于难以再现测量条件（例如在均匀温度下的黑色外壳）的困难。本文介绍并讨论了通过专门设计用于再现黑色均匀外壳的实验设备对两个小球体（直径分别为38和50 mm）进行的计量分析结果。实验结果表明，在强制对流和高辐射负荷下，超过10°C的小球所预测的平均辐射温度被系统低估了。由于难以再现测量条件（例如在均匀温度下的黑色外壳）的困难。本文介绍并讨论了通过专门设计用于再现黑色均匀外壳的实验设备对两个小球体（直径分别为38和50 mm）进行的计量分析结果。实验结果表明，在强制对流和高辐射负荷下，超过10°C的小球所预测的平均辐射温度被系统低估了。