Study of Operative Temperature Using the Novel Detail Approach in Determining Mean Radiant Temperature – Comparison Between Wall-Mounted Convector and Conventional Radiator

Abstract

SummaryMost of the physical parameters that are used to assess the satisfaction with the ambient thermal condition in a mathematical way are contained within the definition of operative temperature. This temperature, which can be used as a representative of indoor thermal comfort, is a function of the air temperature, the mean radiant temperature and the relative air velocity.In this paper, the room air, mean radian temperature and indoor air velocity were determined experimentally for wall-mounted convector and conventional radiator at controlled room conditions. The room air temperature and indoor air velocity were continuously measured at several positions and heights (0.75 m and 1.5 m) using calibrated T-type thermocouples and hot wire probes, while mean radiant temperature was calculated using the thermograms captured by the IR thermal camera and numerically computed radiation view factors. Each wall was divided into several sections with approximately similar temperatures (differences < 0.5 °C) for which view factors were determined. Thermal heat output of the tested heat emitters was derived according to EN 442-2:2014. Obtained results were analysed and conclusions about the achieved thermal comfort and related energy saving were made accordingly. Key words:Mean radiant temperature, operative temperature, thermal comfort, thermography, heat emitters IntroductionEuropean and national regulations based on EPBD (Energy Performance of Buildings Directive) seek to decrease energy consumption in buildings, without decreasing the thermal comfort, to achieve goals which include emission control and reduction of primary energy consumption. Prevision and assessment of energy consumption in households are essential items in achieving these goals. Heating, ventilation and air conditioning systems (HVAC) account for over 60% of total energy consumption in buildings [1]. High energy consumption of traditional HVAC systems is based on the aspirations to achieve and maintain uniform air temperature in rooms, preferably at an interval of 2°C [2]. However, recent research has shown that the overall satisfaction with thermal comfort was accomplished in only 11% of buildings [2].

A Field Survey on Indoor Climate in Land Transport Cabins of Buses and Trains

“…The calibration session occurred during a 10-hour test in a room with controlled IEQ conditions, varying slowly and continuously. Considering the discussions and findings of previous studies [53][54][55] on operative temperature, the similarity of the IEQ multiprobe device used in the current study to the grey sensor was evaluated by [56]. Moreover, in the recent findings of Broday et al (2021) [57], it was adequate to employ the IEQ multiprobe device for the measurement of T O since this solution ensures less uncertainty than the calculation of the T O based on air temperature, mean radiant temperature, and air velocity, where there are three sources of error.…”

Variation of Mean Radiant Temperature in Rooms for Summer and Winter Conditions

“…For seated posture, the element b for vertical surfaces in the lower sections is 0.6 m, whereas for standing posture, it is 1 m, as shown in Figure 1. There have been subsequent studies on the determination of MRT from the calculation of angle factors [14][15][16][17].…”

An Environmental Quality Assessment of Office Buildings: The Impact of a Glass Façade on Users in Different Climate Contexts in Croatia

“…Users are usually able to control the inside air temperature. Most standards use operative temperature (a function of the air temperature, the mean radiant temperature, and the relative air velocity) as a representative of the indoor thermal comfort [17,18]. Other environmental factors are physiologically associated with overheating, including a lack of air movement and high humidity.…”