Thermal comfort difference

Thermal comfort is defined as the condition of mind that expresses satisfaction with the thermal environment. Dissatisfaction may be caused by thermal discomfort of the body as a whole as expressed with the PMV and PPD indices, or it may be caused by unwanted cooling (or heating) of a particular part of the body. Due to individual differences, it is impossible to specify a thermal environment that will satisfy everybody. There will always be a percentage of dissatisfied occupants, but it is possible to specify an environment predicted to be acceptable by a certain percentage of the occupants. 

The flow field created within the protection zone depends mainly on the density difference between supply air and room air (Fig. 10.90). With vertical flow the supply air should be isothermal or cooler than ambient air. If it were warmer, the extension of the controlled flow would be reduced due to buoyancy effects, resulting in the supply air not reaching the operator s breathing zone. As the. supply air cannot be used for heating, the operator s thermal comfort should be maintained, preferably with radiant heaters in cold environments. If the supply air temperature is lower than the room air, the denser supply air accelerates down to the operator, and for continuity reasons the supply flow contracts. Excessive temperature differences result in a reduced controlled flow area with thermal discomfort, and should only be used in special cases. 

V Different ventiiation-opening control strategies in terms of compliance with thermal comfort requirements... 

In industrial ventilation the majority of air velocity measurements are related to different means of controlling indoor conditions, like prediction of thermal comfort contaminant dispersion analysis adjustment of supply airflow patterns, and testing of local exhausts, air curtains, and other devices. In all these applications the nature of the flow is highly turbulent and the velocity has a wide range, from O.l m in the occupied zone to 5-15 m s" in supply jets and up to 30-40 m s in air curtain devices. Furthermore, the flow velocity and direction as well as air temperature often have significant variations in time, which make measurement difficult. 

It should be noted that no Ihcnnal environment will please everyone. No matter what we do, some people will expres.s some discomfort. Tire thermal comfort zone is based on a 90 percent acceptance rate. Thai is, an environment is deemed comfortable if only 10 percent of the people are dissatisfied with it. Metabolism decreases somewhat with age, but it has no effect on the comfort zone. Research indicates that there is no appreciable difference between ihe environments preferred by old and young people. Experiments also show that uieu and women prefer almost the same envirorunent. The metabolism rate of women is somewhat lower, but lliis is compensated by their slightly lower skin lemperature and evaporative loss. Also, there is no significant varialion in the comfort zoue from one part of the world to another and from winter to summer. Therefore, the same thermal coinfort conditions can be used llirouglwut the world in any season. Also, people cannot acclimatize themselves to prefer different comfort conditions. 

Note that the operative temperature will be the arithmetic average of the ambient and surrounding surface temperatures when the convection and radiation heat transfer coefficients are equal to each other. Another environmental index used in thermal comfort analysis is the effective temperature, which combines the effects of temperature and humidity. Two environments with the same effective temperature evokes the same thermal response in people even though they are at different temperatures and humidities. 

Figure 7.4 Thermal sensation (top) and thermal comfort (bottom) for a normal firefighting suit, a suit with cool pads inside and a water-perfused top (a perfused significantly different from control b cool pad significantly different from control c cool pad significantly different from perfused).

That thermal comfort is different than thermal sensation... 

Bakkevig, M.K., Nielsen, R., 1995. The impact of activity level on sweat accumulation and thermal comfort using different underwear. Ergonomics 38, 926-939. 

Two workwears composed from either aramid or from a hre-resistant viscose/merino wool underwear and a viscose/aramid outerwear [96] were used for the study. The workwears showed no signihcant differences with respect to exhaustion, core temperature, and thermal comfort. However, the sweat distribuhon differed significantly in both workwears. For economic reasons, it has been suggested that the viscose/merino wool blended underwear favor the use of fire-resistant viscose blended fabrics in workwears. 

One will recall from Equations 18-2and 18-4 that air velocity is one of the key physical parameters contributing to control of heat stress. Air velocity strongly influences convective and evaporative cooling. When it is warm indoors and cool outdoors, we may open a window in a building to let in clean air. Not only is there a temperature difference, but there is air movement. We turn on a fan or set a fan in a window to increase air velocity. Most often we use thermal comfort ventilation to provide cooling. However, if the conditions are right, ventilation can warm a space and its occupants. 

Most diapers currently available are bulk stmctures. A typical diaper is composed of three main components nonwoven layers (top sheet or facing sheet keep the surface dry to facilitate good skin care conditions, back sheet, and distribution layer that prevents leakage and give a cloth-like feel to the external surface), core layer (fluff pulp, tissue, and polymer transfer fluid from the surface, absorb, and hold excretes), and breathable film. Each has a different contribution to the thermal comfort property of the multilayered diaper, (llhan, ingik, im ek, 2015). 

Comparison of different medieal elothing used in Operating Rooms (OR s)—the importance of thermal comfort at work... 

ABSTRACT The analysis of a thermal comfort or to a thermal stress situation can be achieved using diverse techniques, models and numerical simulations. The main purpose of this paper is to use a human thermal software to analyze the human response to different thermal environmental conditions. The human thermal model is based on equations of heat and mass transfer and, based on the parameters of thermal environment that influence comfort, it can predict the temperatures and humidity at the human body and clothing. A simulation was done using the experimental data obtained from a field investigation at an industrial plant. Results indicate that the software can differentiate body parts concerning its thermal behavior according to their adaptability and in all cases, the temperature values tend to stabilization. A verification of the coefficients of heat transfer between the cloth and the environment is required being pointed as future work. 

Sampath, M., Aruputharaj, A., SenthiUcumar, M., Nalankilli, G., 2012. Analysis of thermal comfort characteristics of moisture management finished knitted fabrics made from different yams. J. Ind. Text. 42, 19-33. 

By using the manikin tests and human trials, many researchers have assessed thermal comfort performance of different types of regular and specialized clothing (Barker, 2008 Bhattacharjee and Kothari, 2009 Famworth, 1983 Hes et al., 1996 Huck and... 

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