Wind chill factor

WORST 1 No written procedures, or standard way of performing tasks Not integrated with training High levels of noise Poor lighting High or very low temperatures and high humidity or wind chill factors... 

Cold injury (frostbite and hypothermia) and impaired ability to work are dangers at low temperatures and when the wind-chill factor is low. To guard against them, the personnel at an industrial site should (a) wear appropriate clothing, (b) have warm shelter readily available, and (c) carefully schedule work and rest periods, and monitor workers physical conditions. 

The temperature at the surface of the droplet is determined by the evaporation rate obtained from simultaneous mass and heat transfer equation (8.10). (This temperature is the same as the wind chill factor discussed in weather forecasts, which can be calculated with equation (8.10) assuming the form of a moist sphere the size of the average human head.) Under some drying conditions, the heat transfer is the slow step, limiting evaporation, and in others the mass transfer is the slow step. In either case the evaporation rate, dRJdt, can be written as... 

Fur heal transfer purposes, a standing man can be modeled as a 30 Cm diameier, 170 cm-loag vertical cylinder with both the top and botiom surfaces insulared and with the side surface at an average temperature of 34"C. For a convection heat transfer coefficient of 15 W/m "C, deiemiine the rale of heat loss from ihis man by convection in still air al 20°C. What would your answer be if the convection heal transfer coefficient is Increased to 50 W/m °C as a result of winds What is the wind-chill factor in this case Ansuers 336 W, 11 0 W, 3 .7 C... 

We are familiar with the cooling effect of wind and rain on our own exposed skin weather forecasters refer to the wind chill factor . The data in Table 5.1 shows the effectiveness of water sprays in removing heat from the surface of extruded plastic pipes. Consequently, the pipe cooling rate is limited by the transient conduction within the plastic the melt surface can be treated as if kept at the water temperature, and the analysis of the last section be used. 

Whereas the Humidex accounts for the effect of humidity on how the body perceives temperatures above 20 °C, the wind chill factor accounts for the enhanced cooling effect caused by wind. The sensation of temperature depends... 

In cold air, the body loses heat principally by radiation from exposed skin surfaces and a small amount of convection or conduction. The rate of heat loss increases with movement of air across the exposed skin, which produces a cooling effect. The heat lost from skin exposed to a 10-mile-per-hour wind when the ambient temperature is 10°F will be the same as that from skin in still air at -9°F. The wind chill factor is an indication of relative heat loss only. Freezing of tissue will not occur unless the temperature is 32°F or lower. For example, the wind chill factor for a 15-mile-per-hour wind at an ambient temperature of 40°F is 22°. Tissue and blood will not freeze, but the body will compensate for the added heat loss. 

Wind-Chill Factor—Wind or air movement causes the body to sense coldness beyond what a thermometer actually registers as the temperature. 

The effects of cold stress should also be considered where appropriate. At a critical level it can lead to increasing lethargy and apathy, and poor control of movement. There are obviously areas and jobs where cold stress is a problem. This is a product of air temperature and airflow (the wind chill factor). Jobs where this is a concern include ... 

Wind chill factor can be derived from the Siple Passel formula (source Slater K, J. Text. Inst. 1986 77(3) 157-171) ... 

The skin temperature under calm conditions is taken as 33 °C. The significance of the wind chill factor may be understood by reviewing its effect on the freezing time of exposed flesh. At a wind chill factor of 1000, an individual would feel very cold and at 1200, bitterly cold. When the wind ehill factor is 1400, the exposed flesh would freeze in 20 min, at a wind chill factor of 1800, the exposed flesh would freeze in 10 min, and when the wind ehill faetor is 2400, exposed flesh freezes in 1 min only. 

CHILL FACTOR - Calculated number based on temperature and wind velocity. 

Prolonged exposure to freezing temperatures can result in health problems as serious as trench foot, frostbite, and hypothermia. When body temperature drops even a few degrees below its normal temperature of 98.6°F, the blood vessels constrict, decreasing peripheral blood flow to reduce heat loss from the surface of the skin. The four environmental factors that contribute to cold-related stress include low temperatures, high/cool winds, dampness, and cold water. Wind chill, a combination... 

Finally, cold weather can also present hazards when working at height particularly when the cold weather is accompanied by wind which will produce a chill factor and an apparent temperature that is lower than the actual... 

The advantage of calendering and extrusion methods is that they generally do not use any solvents—a factor making more economical production possible. The most common method for producing film (and sheet) is by extrusion from a melt. Virtually any thermoplastic can be extruded into film and sheet with an extruder, air knife, chill roll, and turret take-up winding. When used with an appropriate film die, materials up to 6 ft wide can be extruded at thickness as low as 0.001 in. The material can then be stretched to produce thickness as low as 0.00025 in. 

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