Thermal comfort indices

Toftum, J. (2005). Thermal comfort indices. In N.A. Stanton, A. Hedge, K. Brookbuis, E. Salas, and H. Hendrick. (Eds.), Handbook of Human Eactors and Ergonomics Methods (pp. 590-603). Boca Raton, FL CRC Press. 

The guarded hot-plate method can be modified to perform dry and wet heat transfer testing (sweating skin model). Some plates contain simulated sweat glands and use a pumping mechanism to deUver water to the plate surface. Thermal comfort properties that can be deterrnined from this test are do, permeabihty index (/ ), and comfort limits. PermeabiUty index indicates moisture—heat permeabiUty through the fabric on a scale of 0 (completely impermeable) to 1 (completely permeable). This parameter indicates the effect of skin moisture on heat loss. Comfort limits are the predicted metaboHc activity levels that may be sustained while maintaining body thermal comfort in the test environment. 

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. 

According to the subjectivity associated to thermal comfort, there are many intervals in literature review to interpret this index. In this case-study the limits referred by Talaia et al. (2013), which regard human-being thermal sensation were adopted. According to the authors, 21 C < THI < 24 C is associated to a comfortable thermal sensation 24 C < THI < 26 C wind needed for comfort and THI > 26°C occupants feel too hot. 

The EsConTer Index, a very new thermal index, was developed by Talaia Simoes (2009). This index has being suggest the particularity in interpreting, so far, more clearly and easily thermal comfort, once its results are associated to 7-point... 

ABSTRACT Any human activity is influenced by the working environment in which it is developed. The opinion of employees is, nowadays, an important factor to consider because their perception may be related to their behavior. The satisfaction of all individuals housed in a thermal environment is an almost impossible task because a thermally comfortable environment for one person may be uncomfortable for another. Therefore, it would be ideal to create a thermal environment that satisfied the largest number of workers. As such, the evaluation of thermal comfort implies a certain degree of subjectivity and requires the analysis of two aspects physical (thermal environment) and subjective (state of mind of the individual). This study aims to analyze the pattern of thermal sensation of a packaging section of quick-frozen desalted codfish, discover the location of the most vulnerable workstations to thermal stress and assess the real thermal sensation of workers. The data were collected using a measurement instrument named Center 317—temperature humidity meter . For the analysis of thermal sensation the follow indexes were applied Temperature Humidity Index (THI), Thermal Comfort Scale (EsConTer) and Predicted Percentage of Dissatisfied (PPD). A set of standards were created for each variable and the results obtained indicate the most vulnerable workstations. Intervention strategies were considered. 

The EsConTer index (Talaia Simoes, 2009) was also used in this study. It is based on a color scale Es), considers the comfort sensation Con) and is a Thermal Ter) index, calculated using the followed expression ... 

The occupational environment can be neutral, cold or hot. A combined action between the four environmental parameters (temperature, relative humidity, velocity and radiant heat) and the two individual parameters (clothing worn by the occupants and their activity) can lead to a thermal comfort, discomfort, or to a thermal stress situation (Parsons, 2013). The integration of these parameters can be done in a thermal index in a way that will provide a single value that is related to the effects on the occupants. Three types of indices can be identified empirical, rational and derived. According to Parsons (2000), rational indices are derived from mathematical models that describe the behavior of the human body in thermal environments. The analysis of these situations can be achieved using diverse techniques and comfort models, such as Computation Fluid Dynamics (CFD) and other numerical simulations (Murakami et ah, 2000). The human thermal software (Teixeira et al., 2010) is based on differential... 

ISO EN 7730 standardizes the PMV-PPD index as the method for evaluation of moderate thermal environments. To quantify the degree of comfort, the PMV (predicted mean vote) index gives a value on a 7-point thermal sensation scale -t-3 hot, +2 warm, +1 slightly warm, 0 neutral, -I slightly cool, -2 cool, -3 cold. An equation in the standard calculates the PMV index based on the six factors (clothing, activity, air and mean radiant temperatures, air speed, and humidity). 

The PMV index can be used to check whether a given thermal environment complies with specified comfort criteria and to establish requirements for different levels of acceptability. By setting PMV = 0, an equation is established that predicts combinations of activity, clothing, and environmental parameters that will provide a thermally neutral sensation. Figure 6.1 shows the optimal operative temperature as a function of activity and clothing for different levels of acceptability. 

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