Thermal environment indices

ISO EN 7730 Ciomfort evaluation in moderate environ-nienrs Mode.tate thermal environments Deterrnina tion of the PMV and PPD index and specification of the conditioirs for thermal comfoi r... 

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. 

A computer program is provided for ease of calculation and efficient use of the standard. This rational method of assessing hot environments allows identification of the relative importance of different components of the thermal environment, and hence can be used in environmental design. The WBGT index is an empirical index, and it cannot be used to analyze the influence of the individual parameters. The required sweat rate (SW. ) has this capability, but lack of data may make it difficult to estimate the benefits of protective clothing. 

ABSTRACT Individuals spend most of their time in work environments and because of this reason their workplaces should be provided with optimal work conditions in order to increase performance and avoid work accidents. Thermal discomfort is one of the causes of work dissatisfaction which lead to individuals behavior changes as well as works accidents. This paper aims to study a manufacturing industry inner space affected by heat thermal environments in order to identify the most critical areas regarding two thermal indexes, EsConTer and THI, in which their interpretations valorize workers thermal sensation. From the color maps developed to facilitate indexes analysis the most critical areas of the space in study were easily identified as well as the most critical workstations near those areas. The health and safety department of the industry in study valorized the results in order to develop measures that may improve the occupational health of the occupants due to the approximation of the indexes results to workers thermal sensation. 

As previously, the color maps from both indexes suggest the same conclusions. This fact was demonstrated by the calculation of the correlation coefficient between both indexes, 0.9954, showing a strong agreement between EsConTer index and THE The circles with number on both color maps represent the workstations most affected by heat thermal environments. 

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 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... 

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. 

The PMV index predicts the mean value of the thermal preferences of a large group of people exposed to the same environment. But individual votes are scattered around this mean value, and it is useful to predict the number of people likely to feel uncomfortably warm or cool. The PPD (predicted percentage of dissatisfied) index establishes a quantitative prediction of the number of thermally dissatisfied people. The PPD predicts the percentage of a large group of people likely to feel too warm or cool, i.e., voting hot (-t-. , warm (4-2), cool (-2), or cold (-3) on the 7-point thermal sensation scale. 

Oilfields in the North Sea provide some of the harshest environments for polymers, coupled with a requirement for reliability. Many environmental tests have therefore been performed to demonstrate the fitness-for-purpose of the materials and the products before they are put into service. Of recent examples [33-35], a complete test rig has been set up to test 250-300 mm diameter pipes, made of steel with a polypropylene jacket for thermal insulation and corrosion protection, with a design temperature of 140 °C, internal pressures of up to 50 MPa (500 bar) and a water depth of 350 m (external pressure 3.5 MPa or 35 bar). In the test rig the oil filled pipes are maintained at 140 °C in constantly renewed sea water at a pressure of 30 bar. Tests last for 3 years and after 2 years there have been no significant changes in melt flow index or mechanical properties. A separate programme was established for the selection of materials for the internal sheath of pipelines, whose purpose is to contain the oil and protect the main steel armour windings. Environmental ageing was performed first (immersion in oil, sea water and acid) and followed by mechanical tests as well as specialised tests (rapid gas decompression, methane permeability) related to the application. Creep was measured separately. 

Some experiments have failed to demonstrate an effect of maternal odors on stressed offspring. The heart rate rose in rat pups removed from their home cage and placed in an unfamiliar environment this was taken as an index of fear. Tests with mothers and soiled bedding from mothers or other rat pups showed that tactile and thermal stimuli reduced fear in 16-day old pups, but olfactory cues from the mother or odors from the home cage did not (Siegel et ah, 1988). 

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. 

Features Tough engineering resin with high abrasion resist, and stability in harsh thermal, chem., and UV environments readily melt processable Properties Sp.gr. 1.78 melt flow 3-7 g/10 min m.p. 141-145 C ref. index 1.41 tens. str. 3500-6000 psi (break) tens, elong. 10-20% (yield), 400-500% (break) Izod impact 12-18 ft Ib/in. notch Shore hardness D65-70 water absorp. 0.03% distort, temp. 40-50 C (1.8 MPa) sp. heat 1.26-1.42 y/kg K flamm. V-0. 

For the physical thermal tests, the surgical gowns were tested over a standard surgical ensemble on a thermal manikin in an environment chamber (ASTM F 1291) (4). The resistance to dry and evaporative heat transfer and the permeability index values were measured according to procedures given by McCullough et al. (6). 

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