Evaluating the thermal comfort performance of heating systems using a thermal manikin with human thermoregulatory control

© International Society of the Built Environment. © The Author(s) 2014. The evaluation of the local thermal comfort and application of thermal manikins can further assist the design and selection of heating systems. This study aimed at evaluating the thermal comfort performance of different heating systems using a newly developed thermal manikin with an enhanced thermal control. The heating systems for a workstation, included a conventional radiator (convector) mounted under the window, heated floor in the occupied zone and an infrared heater mounted to the ceiling. The experiments were conducted in a test room with a façade attached to a climate chamber to simulate outdoor winter conditions. In these experiments, the supplied power for the different systems was kept constant to independently quantify the differences in their thermal comfort performance at same energy consumption. The thermal manikin was deployed in the occupied zone to evaluate the local and overall thermal comfort under each system using the equivalent temperature (Teq) approach. The thermoregulatory control used in the manikin operation is based on a model of human thermoregulation that interacts accurately with the surrounding environment through real-time measurements. The results showed that at the same energy consumption of the different systems, the variations in local thermal comfort levels were up to 1 on the comfort scale

Ventilation rates in naturally ventilated primary schools in the UK; Contextual, Occupant and Building-related (COB) factors

Indoor Air Quality (IAQ) in classrooms is assessed by CO2 levels and Ventilation Rates (VRs). Factors affecting VRs fall into Contextual, Occupant and Building (COB) related factors. This study investigates how VRs are affected by COB factors in 29 naturally-ventilated classrooms in the UK during Non-Heating and Heating seasons. Building-related factors classify classrooms with high or low potentials for natural ventilation, with 45% of classrooms having high potentials. Contextual factors including season, operative temperature (Top), outdoor temperature (Tout), ‘Top-Tout’ and air density can limit or increase VRs. Occupant-related factors classify occupant's good or poor practice of environmental adaptive behaviours. ‘Open area’ as a reflection of all COB factors is strongly correlated with ventilation rates. Results show that 12% and 19% of variations in ventilation rates are explained by open areas during non-heating and heating seasons, respectively. Findings highlight that to have VR of 8 ± 1.28 l/s.p during non-heating seasons and VR of 8 ± 1.07 l/s.p during heating seasons, average open areas of 3.8 m2 and 2 m2 are required, respectively. This difference can mostly be explained by temperature difference between inside and outside. Results show COB factors need to be considered holistically to maintain adequate VRs. Classrooms in which all COB factors are met provide average VR of 11 l/s.p and classrooms in which none of COB factors are met provide average VR is 3.1 l/s.p. This study highlights that 40% of classrooms according to EN 13779 and 80% of classrooms according to ASHRAE Standard fail to provide adequate VRs

A Method to Protect Mine Workers in Hot and Humid Environments

Background: Work comfort studies have been extensively conducted, especially in the underground and meteorological fields resulting in an avalanche of recommendations for their evaluation. Nevertheless, no known or universally accepted model for comprehensively assessing the thermal work condition of the underground mine environment is currently available. Current literature presents several methods and techniques, but none of these can expansively assess the underground mine environment since most methods consider only one or a few defined factors and neglect others. Some are specifically formulated for the built and meteorological climates, thus making them unsuitable to accurately assess the climatic conditions in underground development and production workings. Methods: This paper presents a series of sensitivity analyses to assess the impact of environmental parameters and metabolic rate on the thermal comfort for underground mining applications. An approach was developed in the form of a “comfort model” which applied comfort parameters to extensively assess the climatic conditions in the deep, hot, and humid underground mines. Results: Simulation analysis predicted comfort limits in the form of required sweat rate and maximum skin wettedness. Tolerable worker exposure times to minimize thermal strain due to dehydration are predicted. Conclusion: The analysis determined the optimal air velocity for thermal comfort to be 1.5 m/s. The results also identified humidity to contribute more to deviations from thermal comfort than other comfort parameters. It is expected that this new approach will significantly help in managing heat stress issues in underground mines and thus improve productivity, safety, and health. Keywords: maximum sweat rate, skin wettedness, thermal comfort models, tolerable worker exposure times, underground mine environmen