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Energy Efficient Air Conditioning and Mechanical Ventilation
Published in Clive Beggs, Energy: Management, Supply and Conservation, 2010
Mean radiant temperature is the average surface temperature of all the surfaces ‘seen’ in a room space. It can be either measured indirectly using a globe thermometer or calculated from surface temperatures. For most cuboid-shaped rooms, the mean radiant temperature in the centre of the room can be expressed as: tr=∑(As. ts)∑As
Hot and Cold Environments: Temperature Extremes
Published in Martin B., S.Z., of Industrial Hygiene, 2018
Mean radiant temperature can be evaluated by measuring globe temperature. Globe temperature is measured using a black globe thermometer: a 15-cm (6 in.) hollow copper sphere painted a matte black, with a temperature sensor placed in the center of the globe. This device is often referred to as the Vernon globe thermometer, and the resultant reading the Vernon globe temperature (VGT). The globe thermometer must be given sufficient time to stabilize in a particular environment or measurements may be in error. Usually, a minimum of 15 minutes is required for this probe to reach stability, although the ACGIH recommends a 25-minute stabilization period.
Human Heat Stress
Published in Ken Parsons, Human Heat Stress, 2019
In summary, an estimate of heat transfer by radiation (R), can be calculated from the difference between the fourth powers of the absolute temperatures of mean skin (or clothing) temperature and the mean radiant temperature for the shape of the person at the position of the person. This is multiplied by a term called the (human) heat transfer coefficient for radiation (hr) which is a combination of the emissivity, projected radiation surface area, and the Stefan–Boltzmann constant (5.67 × 10−8 W m−2 K−4). An important environmental parameter, essential for assessing heat stress, is therefore the mean radiant temperature.
Applying a comfort model to building performance analysis
Published in Architectural Science Review, 2020
Mark Luther, Olubukola Tokede, Chunlu Liu
Another significant contribution to changing and controlling the mean radiant temperature is through glazing selection and shading devices. No doubt one of our biggest problems in commercial office buildings is the expansive area of glazing on the façade and the temperature of the glass as well as its solar transmittance. The manner in which this is dealt with can have a tremendous effect on thermal comfort (Anderson and Luther 2012). For the two case studies examined, the glass shading systems proved effective as it accounted for 51.4% reduction in PPD for the Block House, and 5% reduction in PPD for the Elevated House. Cho, Yoo, and Kim (2014) also corroborated that appropriate use of shading can enhance thermal comfort and minimize energy consumption. Although, dynamic shading systems in facades has been suggested for substantiating indoor thermal comfort, they tend to be relatively costly and still remain a subject of research (Moloney et al. 2019).
A field study on indoor environmental quality and energy savings of an office building integrated with underfloor air conditioning system in India
Published in Science and Technology for the Built Environment, 2023
Ramesh Krishnan Lakshmanan, Gangadhara Kiran Kumar Lachireddi
The globe thermometer measures the mean radiant temperature despite the non-uniform thermal radiation in space. Figure 3(c) illustrates the relationship between the indoor air temperature and mean radiant temperature. The linear regression scatter plot describes the strong correlation between indoor air temperature and mean radiant temperature (R2 = 0.783, R = 0.88, slope = 0.97, intercept = 1.24 and P < 0.05). The present study indicates that the mean radiant temperature effect was insignificant in the indoor environment study space. For that reason, most of the field studies (Tewari et al. 2019; Dhaka and Mathur 2017) on Indian air-conditioned buildings suggested using room air temperature as an operative temperature.
Modelling the thermal microenvironment of footwear subjected to forced ventilation
Published in Ergonomics, 2022
Figure 1 shows a model of the insulation elements that compose the total dry-heat insulation between the foot skin and the ambient environment with forced ventilation. This model is based on the four-layer clothing model (Lotens 1993), but we consider only three layers, i.e. the trapped air layer, the footwear fabric layer, and the adjacent air layer, and exclude the sock layer. The mean radiant temperature of the surrounding environment is assumed to equal the ambient air temperature. This model requires many geometrical parameters of the foot, footwear, and footwear cavity to be defined (Table 1).