Thermal comfort is a subjective evaluation of a person’s satisfaction with the surrounding thermal environment (ISO 7730), mainly divided into three aspects: physical, physiological, and psychological.
The evaluation indicators mainly include Bayesian scale, ASHRAE scale, and ISO standard.
Jiantong Technology JT2180 indoor thermal comfort measurement instrument adopts ISO standard evaluation method (corresponding to China: GB/T18049)
ISO has developed the ISO 7730 standard based on the research results of Professor PO Fanger from Denmark, in which the PMV-PPD index is used to describe and evaluate the thermal environment. This indicator comprehensively considers six factors, including human activity level, clothing thermal resistance, air temperature, air humidity, average radiation temperature, and air flow velocity, in order to meet the thermal balance equation of the human body. The subjective sensation level of the vast majority of people is determined through subjective sensation experiments. The above research results and corresponding standards form the basis for designing comfortable thermal environments in the future.
PMV index
The full English name of PMV is Predicted Mean Vote, which means predicting the average number of votes.
The PMV value is an evaluation index proposed by Professor P.O. Fanger of Denmark to characterize the human body’s thermal response (cold and hot sensation), representing the average of the cold and hot sensation of most people in the same environment. The PMV-PDD thermal comfort model is the earliest digital model for human body temperature regulation, with seven levels of sensation, namely:
Cold (-3)//Cool (-2)/Slightly cool (-1)//Neutral (0)//Slightly warm (+1)//Warm (+2)//Hot (+3).
PPD index
PPD English full name prsdicted percentage of dissatisfied people
The PPD index is the average voting value of the group expected to be dissatisfied with the thermal environment. The PPD index can predict whether the population feels too warm or too cold, “according to a vote on the seventh level of heat sensation
The percentage of people who are hot (+3), warm (+2), cool (-2), or cold (-3).
Measurement function for JT2180 measurement content
Measurement indicators: air temperature Ta, black bulb temperature Tg, wet bulb temperature Tnw, relative humidity RH, air flow rate Va, carbon dioxide CO2, particulate matter PM2.5
Calculation indicators: PMV, PPD, DR, Td, Tu, tr, WBGT, IREQ, DLE, RT, WCI
Extended measurement: Noise (dB), Illuminance (Lux)
The indoor environment of quality should fully consider other physical factors, among which noise and lighting are the most influential physical factors besides thermal comfort. In China’s green building evaluation standard “GB/T50378-2019”, PMV, PPD, acoustic environment, and light environment are important quantitative indicators.
In addition, comfort, lighting, and sound environment are also important indicators in the WELL certification system,
Measurement Application
In the assessment of indoor environmental quality in buildings, PMV-PPD is one of the most important indicators. It fully considers human factors rather than just objective conditions. PMV-PPD prediction data also plays a crucial role in building design. In addition to buildings, other fields are increasingly using PMV-PPD indicators for thermal comfort evaluation of spaces, such as high-speed railway carriages, subway carriages, helicopter cabins, car carriages, etc.
Design and Research on Comfort of Automobile Driver’s Cabin
Car interior comfort design
The thermal environment inside the car cab is severely affected by solar radiation and outdoor air temperature and humidity. By monitoring the comfort indicators inside the car, the operation of the automatic air conditioning system can be better controlled.
Comfort Control and Research of High Speed Rail Carriage
Environmental Control in High Speed Rail Cars
In the development of high-speed trains, due to the improvement of operating speed and the requirements for train service quality, the thermal comfort requirements inside the train have also increased accordingly. By using the PMV-PPD index in the ISO7730 standard to evaluate the thermal comfort inside the passenger compartment of high-speed trains, a recommended range of set values that meet the requirements for thermal comfort inside the train will be obtained.
Comfort monitoring of public areas (shopping malls, subway stations, terminals, etc.)
China stipulates in GB/T 18204.1 “Methods for Testing Public Place Hygiene” physical factor testing that the PMV value of comfort in public places is measured and evaluated according to the method of GB/T 18049. densely populated public places include shopping malls, subway stations, airports, high-speed rail stations, etc. Through comfort testing, air conditioning equipment can be adjusted in real time, quickly improving the spatial environment, and maximizing energy-saving optimization.