Temperature comfort

The boom in suburban home building also had other effects on energy resources. As large-scale builders cleared the land of trees, the new homes were subject to more heat and more cold, increasing the energy that was required to keep the temperature comfortable inside. 

Is this a climaw-controllcd area Is the temperature comfortable ... 

Eundamental to the design of any air conditioning system is the determination of the operating conditions of temperature and humidity. Worker comfort must also be considered. 

Process Requirements. Typical inside dry-bulb temperatures and relative humidities used for preparing, processing, and manufacturing various products, and for storing both raw and finished goods, are Hsted in Table 1. In some instances, the conditions have been compromised for the sake of worker comfort and do not represent the optimum for the product. In others, the conditions Hsted have no effect on the product or process other than to increase worker efficiency. 

The temperature and humidity should be maintained at comfort conditions consistent with the operator s expected level of activity in order to minimise perspiration. Constant temperature and humidity may also be required in machine rooms to prevent the etching or corrosion of machine parts. If perspiration causes only minor damage to the product and results in few rejects, then inside design conditions at 27°C and 40% rh are satisfactory. Where even small amounts of perspiration cause extreme damage to precision-machined parts and result in a high amount of rejects, inside design conditions of 21°C and 40% rh are recommended. 

Eigure 3 shows the winter and summer comfort zones plotted on the coordinates of the ASHRAE psychrometric chart. These zones should provide acceptable conditions for room occupants wearing typical indoor clothing who are at or near sedentary activity. Eigure 3 appHes generally to altitudes from sea level to 2150 m and to the common case for indoor thermal environments where the temperature of the surfaces (/) approximately equals air temperature (/ and the air velocity is less than 0.25 m/s. A wide range of environmental appHcations is covered by ASHRAE Comfort Standard 55 (5). Offices, homes, schools, shops, theaters, and many other appHcations are covered by this specification. 

Fig. 3. Comfort 2ones at 6% of population predicted dissatisfied from ref 4. RH lines are valid only when the air temperature equals the average temperature of the surfaces, (a) Operative temperature range where ET is effective temperature as defined in text, (b) Comfort 2one detail. To convert...

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. 

Fig. 4. Comfort lines, ambient air temperature equals mean radiant temperature (4). To convert watts to kcal/min, multiply by 0.143.

Low temperature formabiHty and resiHence are key properties in the area of shoe components, ie, box toes and counters. These ionomer components are not seen by the purchaser of the finished article, but provide comfort and durabiHty in high quaHty footwear. 

A guarded hot-plate method, ASTM D1518, is used to measure the rate of heat transfer over time from a warm metal plate. The fabric is placed on the constant temperature plate and covered by a second metal plate. After the temperature of the second plate has been allowed to equiUbrate, the thermal transmittance is calculated based on the temperature difference between the two plates and the energy required to maintain the temperature of the bottom plate. The units for thermal transmittance are W/m -K. Thermal resistance is the reciprocal of thermal conductivity (or transmittance). Thermal resistance is often reported as a do value, defined as the insulation required to keep a resting person comfortable at 21°C with air movement of 0.1 m/s. Thermal resistance in m -K/W can be converted to do by multiplying by 0.1548 (121). 

Comfort. In the past, the evaluation of fabric or garment comfort has been a subjective process influenced by such variables as temperature, insulating efficiency, moisture absorption, drying speed, softness, bulk, fabric constmction, and air permeability. Human factors must also be considered. 

Requirements. Automotive brakes must satisfy a certain set of consumer expectations, which iacludes safety, comfort, durabiUty, and reasonable cost. In technical terms, these expectations are translated iato a set of specific requirements such as high and stable friction, no or minimal vibration and noise, and low wear rates for the friction material and rotor mating surfaces, all of which have to be achieved simultaneously at a reasonable cost. Particularly, the performance has to be stable under varying appHcation conditions over extremes ia temperature, humidity, speed, and deceleration rate for occasional or many consecutive stops. The requirements for use ia machines are less stringent. 

Indirect refrigeration systems are more prevalent in the chemical industiy than in the food industiy, commercial refrigeration, or comfort air-conditioning. This is even more evident in the cases where a large amount of heat is to be removed or where a low temperature level is involved. Advantage of an indirect system is centrahzation of refrigeration equipment, which is specially important for relocation of refrigeration equipment in a nonhazardous area, both for people and equipment. 

HVAC the HVAC system is not able to control existing air contaminants and ensure thermal comfort (temperature and humidity conditions that are comfortable for most occupants). 

In contrast, variable air volume (VAV) systems condition supply air to a constant temperature and ensure thermal comfort by varying the airflow to occupied spaces. Most early VAV systems did not allow control of the outdoor air quantity, so that a decreasing amount of outdoor air was provided as the flow of supply air was reduced. More recent designs ensure a minimum supply of outdoor air with static... 

Check temperature and/or humidity to see whether the complaint area is in the comfort range Take more than one measurement to account for variability over time and from place to place. Check thermostat operation. Check whether the supply air temperature corresponds to the design criteria. Use a hygrothermograph (if available) to log temperature and humidity changes in the complaint area. 

Humans seek and want thermal comfort, even at work in industrial settings. Clothing, activities, posture, location, and shelter are chosen, adjusted, altered, and sought consciously and unconsciously to reduce discomforts and enable us to focus more on the other tasks of life. Discomfort can contribute to mistakes, productivity decreases, and industrial accidents. " Thermal discomfort results from the physiological strain of thermoregulation. The strain can be in the form of altered body temperatures, sweating and excessive skin moisture, muscle tension and stiffness, shivering, and loss of dexterity. A small... 

Humans and the other warm-blooded animals have developed thermoregulatory systems to carefully control body temperature to levels that enable them to function and survive effectively. In general, thermal comfort occurs when the physiological effort to control body temperature is minimized for the activity. Table. 5.1... 

NEUTRAL comfort, minimized effort, (mean body temperature). 36.2 C... 

Clothing affects heat and moisture loss. Increasing the thickness or number of layers of clothing increases its insulating capability and reduces body heat loss. Clothing insulation is usually described with the do unit. Originally, t do was defined as the thermal resistance necessary for comfort while sedentary in a uniform still air environment of 21 °C. In conventional SI nomenclature I do has a thermal resistance of 0.155 K m-/W. Some ensembles do values and associated comfort temperatures are shown in Fig. 5.4. 

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 S.4 Some clothing ensembles with associated do values and comfort temperatures. 

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... 

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