Temperature sensations

Effective temperature (ET ) is a single number representing those combinations of temperature and humidity which are equivalent in terms of comfort. It is defined as the dry-bulb temperature of the environment at 50% relative humidity. Standard effective temperature loci for normally clothed, sedentary persons are plotted on Eigure 3. The sensation of comfort depends in part upon the wetness of one s skin. Thus, as a person becomes more active the effective temperature lines become more hori2ontal and the influence of relative humidity is more pronounced. 

Flavor. The sensation produced by a material taken into the mouth, perceived principally by the senses of taste and smell, but also by the common chemical sense produced by pain, tactile, and temperature receptors in the mouth. 

The walkthrough should focus on uneven temperatures, persistent odors, drafts, sensations of stuffiness. You may find that occupants are attempting to compensate for an HVAC system that doesn t meet their needs. Look for propped-open corridor doors, blocked or taped-up diffusers, popped-up ceiling tiles, people using individual fans/heaters or wearing heavier (or lighter) clothing than normal. 

The sensation of warmth or coldness is caused by temperature. Adding heat to a substance not only raises its temperature, but also produces changes in several other qualities. The substance expands or contracts its electric resistance changes and in the gaseous form, its pressure changes. Five different temperature scales are in use today Celsius, Fahrenheit, Kelvin, Rankine, and international thermodynamic. 

The temperatures monitored in Fig. 5.2 are used by the brain to regulate shivering, blood flow to the skin, and sweating. The sensed temperatures also contribute to our overall feelings of warmth and other thermal sensations. 7 hermal sensation (TS) can be predicted over a wide range of activities (0.8 to 4 met) from simple deviations in the mean body temperature (T j,) from the mean bodv temperature when the person feels neither warm or cool but neutral (Fig. 5.2). 

During transients the rate of change of mean body temperature can have a strong effect on thermal sensation. 

FIGURE 5.2 Temperature sensors for ternperature regulation and thermal sensation. 

FIGURE S.3 Schematic of skin and core temperatures for a neutral thermal sensation. 

The consequence of the relationships of Table 5.3 and Fig. 5.2 is that for a neutral thermal sensation, at steady state, the core temperature increases while the skin temperature decreases with increased metabolic activity (Fig. 5.3). The increase in metabolism causes sweating which decreases skin tem-perature. 

The clothing insulation necessary for comfort or a neutral thermal sensation (TS = 0) in a thermally uniform 50% RH still-air environment is graphed in Fig. 5.5. The slope of the graph is such that comfort temperature is decreased about 0.6 °C for each 0.1 do increase in clothing insulation. The... 

FIGURE 5.S Clothing imulation necessary for neutral thermal sensation of sedentary persons (I met) In a thermally unifonri still-air envrronment with 50% relative hurnidity. For higher activity levels the temperature at a do level can be reduced about 1.4 °C per met increase. ... 

In general, when a person is thermally comfortable, the person s thermal sensation for the whole body is at or near neutral as depicted in Fig. 5.7a. As we have seen, the thermal conditions necessary for comfort are affected by clothing insulation. Figure 5.7b shows the range of temperatures and humidities... 

Optimum comfort would be in the center of each zone. Moving away from the center, some people would be expected to have thermal sensations approaching - 0.5 and -i-0.5 at the cooler and warmer ET borders. The zones of Fig. 5.7b are for sedentary or slightly active ( M 1.2 met) people. If the activity level is higher than that, then the ET" line borders can be shifted about 1.4 K lower per met of increased activity. Similarly, if the clothing is different than the 0.9 and 0.5 do vales of Fig. 5.7a, the temperature boundaries can be decreased about 0.6 K for each 0.1 do increase in clothing insulation. Another, similar way to adjust the comfort zone for both different activity levels and do values is to shift the zone centered on the optimum temperature at... 

Conditions that are warmer than the applicable still-air comfort zone of Fig. 5.7b can often be made comfortable by increasing the air speed. If the conditions are 1 to 6 °C warmer than the still-air comfort zone of Fig. 5.7b, the necessary air speed v) to restore thermal balance and comfort can be estimated from Fig. 5.8, where Tis the temperature difference between the environment and the still-air comfort temperature. Though the increased air speed will bring the whole-body thermal sensation to the comfort level, air motions above 0.8 m/s or so may cause other kinds of discomfort frojn... 

Nevins, R., Gonzalez, R. R., Nishi, Y, and Ciagge, A. P. (1975). Effect of changes in ambient temperature and level of humidiry on comfort and thermal sensations. ASHRAE Trans., 81(2). 

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. 

Figure 6.1 applies for a relative humidity of 50% however, in moderate environments the air humidity has only a modest impact on the thermal sensation. Typically, a 10% increase in relative humidity is experienced as equally warm as a 0.3 °C increase in operative temperature. 

Body thermal sensation The response of the body to changes in the thermal environment, relating to moisture, air movement, or temperature. 

Scales of sensation A simple numerical scale used to report the response of a person to temperature, humidity, air velocity, air purity, noise, light, taste, etc. 

Wind chill index An empirical scale that correlates well with the sensation of bare dry skin due to the chilling effect of the outdoor air temperature and wind speed. 

Promoting an Optimal Response to Therapy Before instillation of otic preparations, die nurse holds the container in the hand for a few minutes to warm it to body temperature. Cold and warm (above body temperature) preparations may cause dizziness or other sensations after being instilled into the ear. 

Jupiter s moon Europa has only been the subject of intense scientific investigation in recent years it is considered to be a member of that small group of heavenly bodies which could perhaps accommodate life (or a precursor of life). About 20 years ago, the Voyager passes afforded sensational pictures of Europa. These showed a network of linear bands, of differing breadths, on a very bright surface. The mean density was calculated as 3,018 35 kg/m3, and the surface temperature measured was 90-95 K. Circumstantial evidence points to either a surface consisting of water ice, or the presence of liquid water or warm ice under the surface. Three models were proposed (Oro et al., 1992) ... 

Prebiotic chemistry must cope with many problems a particularly difficult one is contamination. Prebiotic experiments often lead to the formation of important molecular species in extremely low concentrations. The successes of the synthesis may sometimes appear sensational, but there is always the danger that artefacts may be involved. Control experiments carried out with ultrapure deionised water showed that, at higher temperatures (>373 K), synthetic polymers in components of the apparatus could provide a source of organic contaminants such as formate, acetate or propionate ions. Stainless steel had a catalytic effect on the decomposition of formate, so that the use of titanium alloys in the apparatus is recommended. 

Neurturin (NRTN) plays a critical role in supportingpara-sympathic neurons innervating peripheral target tissues. NRTN is required for the survival and function of enteric neurons and a subset of ganglionic sensory neurons, particularly those mediating temperature sensation. 

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