Clothing Insulation Rate and Metabolic Rate Estimation for Individual Thermal Comfort Assessment in Real Life

Satisfactory indoor thermal environments can improve working efficiencies of office staff. To build such satisfactory indoor microclimates, individual thermal comfort assessment is important, for which personal clothing insulation rate (Icl) and metabolic rate (M) need to be estimated dynamically. Therefore, this paper proposes a vision-based method. Specifically, a human tracking-by-detection framework is implemented to acquire each person’s clothing status (short-sleeved, long-sleeved), key posture (sitting, standing), and bounding box information simultaneously. The clothing status together with a key body points detector locate the person’s skin region and clothes region, allowing the measurement of skin temperature (Ts) and clothes temperature (Tc), and realizing the calculation of Icl from Ts and Tc. The key posture and the bounding box change across time can category the person’s activity intensity into a corresponding level, from which the M value is estimated. Moreover, we have collected a multi-person thermal dataset to evaluate the method. The tracking-by-detection framework achieves a mAP50 (Mean Average Precision) rate of 89.1% and a MOTA (Multiple Object Tracking Accuracy) rate of 99.5%. The Icl estimation module gets an accuracy of 96.2% in locating skin and clothes. The M estimation module obtains a classification rate of 95.6% in categorizing activity level. All of these prove the usefulness of the proposed method in a multi-person scenario of real-life applications.

HVAC CFD Analysis of Air Flow and Temperature Distribution Inside Passenger Compartment

The thermal environment and air quality in a passenger car can affect driver's and passengers' health, performance and comfort. Due to spatial and temporal variation of state variables and boundary conditions in the vehicle cabin, the heating, ventilating and air-conditioning (HVAC) does not have to be designed to provide a uniform environment. This are due to individual differences regarding to physiological and psychological response, clothing insulation, activity, air temperature and air movement preference. Experimental study in vehicle HVAC system can be very costly to be conducted. In order to analyze the air flow and temperature distribution in passengers compartment, a numerical simulation was used in this study to analyze the air flow and temperature distribution of HVAC unit inside Proton Exora passengers compartment, with the air blower speed and air temperature used as parameter, to evaluate the airflow behavior and temperature distribution in the compartment. The simulation data obtained is then compared to the experimental data, showing good agreement between these two methods.

Heat Balance When Climbing Mount Everest

Background: Mountaineers must control and regulate their thermal comfort and heat balance to survive the rigors of high altitude environment. High altitudes feature low air pressure and temperatures, strong winds and intense solar radiation, key factors affecting an expedition’s success. All these climatic elements stress human heat balance and survival. We assess components of human heat balance while climbing Mt. Everest.Materials and Methods: We calculated climbers’ heat balance using the Man-ENvironment heat EXchange model (MENEX-2005) and derived meteorological data from the National Geographic Expedition’s in situ dataset. Three weather stations sited between 3810 and 7945 m a.s.l. provided data with hourly resolution. We used data for summer (1 May–15 August 2019) and winter (16 October 2019–6 January 2020) seasons to analyze heat balance elements of convection, evaporation, respiration and radiation (solar and thermal).Results: Meteorological and other factors affecting physiology—such as clothing insulation of 3.5–5.5 clo and activity levels of 3–5 MET—regulate human heat balance. Elevation above sea level is the main element affecting heat balance. In summer two to three times more solar radiation can be absorbed at the summit of the mountain than at the foot. Low air pressure reduces air density, which reduces convective heat loss at high altitude by up to half of the loss at lower locations with the same wind speed and air temperature.Conclusion: 1. Alpinists face little risk of overheating or overcooling while actively climbing Mt. Everest, despite the potential risk of overcooling at extreme altitudes on Mt. Everest in winter. 2. Convection and evaporation are responsible for most of the heat lost at altitude. 3. Levels of physical activity and clothing insulation play the greatest role in counteracting heat loss at high altitude.

CFD analysis of thermal comfort in hospital operation room with different air distribution design and operative temperature

The operation room is one of the most critical regions in hospital that require extra attention in air ventilation and prevention of dangerous pollutants contamination. A good level of ventilation will help to raise the productivity of workers in terms of performance and ensuring a safe surgery operation. It is obvious that today's operation rooms are completely equipped with mechanical ventilation systems. However, despite the fact that they meet the acceptable comfort standards, surgical workers have complained about thermal discomfort during operation which gives negative impact on their performance. Thermal comfort can be achieved by controlling the temperature, relative humidity and air movement. In this study, the operation room models are simulated to analyze the comfort conditions of surgical workers under 3 different air velocities at 0.2 ms-1, 0.25 ms-1 and 0.35 ms-1 and under 5 different temperatures between 16℃ to 20℃. Additionally, there are two 3D models created with different position of exhaust vent. The thermal comfort of surgical workers is measured using Predicted Mean Vote (PMV) and Predicted Percentage Dissatisfied (PPD) approaches using CBE Thermal Comfort Tool. The PMV and PPD results show that most surgical workers were outside the acceptable range value of -0.5 to +0.5 stated in ASHRAE Standard 55-2020. According to thermal scale index, most of the surgical workers were in a cool and slightly cool state despite the fact that the computational analysis shown an acceptable simulation validated with previous research studies. Finally, it has been discovered that clothing insulation, metabolic rate, mechanical equipment and air distribution design play a significant influence in providing comfort to the surgical workers.

Analysis of heat transfer and factors affecting the thermal propertieson rib 1x1 knitwear

Clothing comfort is very important feature which is considered as a result of different process of heat exchange between human body, clothing and environment. The purpose of this paper is to analyse the impact of clothing insulation on the heat transfer. The measurements were carried out on commercially 1x1 RIB knitted fabrics used for the production of next-to-skin shirts. The one group of samples are made from 100% cotton yarn and another with 96% cotton and 4%lycra. It is noticed that knitted material composition affected the change in heat resistance. Also, this paper presents and verifies the correlation between the measured values of thermal resistance (Rct) and the knitwear thickness (dpl), the covering factor (K), the porosity of the twists (e) and the surface coefficient (dp). Based on these results, a mathematical model for calculating thermal resistance is proposed. Comparing the results obtained with the proposed equation and the measured results, we can see that the deviations are minimal. The highest deviation for sample C4 is 0.05%,while the largest deviation for sample CL4 is 4.6%.

Study on adaptive comfort behaviours in mixed-mode residential buildings in Tianjin, China

This paper presents results of a longitudinal field study which aims to investigate adaptive comfort behaviours (i.e. turning on air-conditioner, turning on fans and opening windows or doors) in residential buildings. Field measurements were conducted in 43 homes in Tianjin, northern China, from Spring through early Winter in 2016. Occupants' ‘right-here-right-now' thermal perception and adaptive comfort behaviours were collected through online questionnaires delivered to their smartphones. Results indicated that clothing insulation adjustment was the requisite adaptive behaviour to attain thermal comfort. Clothing insulation was more climate-responsive in Tianjin's autumn than in summer. Statistical models were developed to predict the likelihood of various thermally adaptive behaviours with regard to outdoor air temperatures. An outdoor air temperature of 25.2°C was associated with maximum use of windows/doors for comfort ventilation and minimum use of air conditioning (AC). When outdoor air temperature exceeded 32.5°C, 50% of occupants turned on AC for cooling.

Ergonomic Evaluation of Thermal Stress in a Tunisian Steel Industry

This work aims to assess thermal stress based on the various measurable thermal stress parameters (wet bulb temperature, air speed, radiation temperature, black globe temperature…). A cross-sectional study was carried in a steel company. The evaluation of thermal stress was made by physical parameters measurment (air temperature, relative humidity, air velocity, globe temperature, clothing insulation, metabolism of work) and analyzed according to the International Standard Organization (ISO) 7933 “Analytical determination and interpretation of heat stress using calculation of the predicted heat strain”. Eighty male workers were mean ageed of 37.9 ± 9.25 years. The climatic conditions category was three (meaning a Long-term stress) in 68.18% of the workers and four (Short-term stress meaning the occurrence of health problems within 30 to 120 minutes of exposure) in 30.3% of workers. The long and short-term thermal stress identified in this study spearhead a prevention strategy (automation of manufacturing processes, improvement of the organization of tasks, and the strengthening of medical surveillance of workers).