For the hot shops, in which heat comes mainly from industrial furnaces, the coefficient m can not accurately be determined depending on the ratio of area occupied by the furnace (or other sources of intense release of heat convection), the gross floor area of the room. Table. 15 shows the data to determine the coefficient m depending on the ratio between the area of heat to the floor surface F.
must bear in mind that the values of m are listed in Tab. 11 and 15, are averages. They may vary depending on the location of equipment, methods of feeding fresh air, roof insulation, number and power of recurrent jets and the like, and.
Now instead of "Guidelines for construction design enterprises, buildings and facilities engineering industry" SN 118-60 published SP 118-68. in which (prilozh. 1) presents recommendations for plants of all profiles with the unit na shops and office ventilation system, how to feed and removing air and values of m, which determines the fraction of heat affecting the air temperature in the working area.
In the second method the whole difficulty lies in determining the correct air temperature coming from the upper band.
The greater the value of x, the lower the temperature of outgoing air, and vice versa.
For chemical, food and other businesses continue to enjoy well-known formula of the temperature gradient. Thus, to determine / bpm depending on h.; and the height of the room can use a formula, where x is the height of the room from floor to center of vent holes in the m;
A temperature gradient of 1 m in height in В° C.
The quantity A purely empirical and depends on many factors, including the method of feeding the supply air. In typical cases, for industrial buildings the value of A ranges from 0.3 to 1. Only in rare cases, take the values of A to 1.2. For areas with less than 4 meters high temperature increase in height can be ignored.
More recently, believed that the temperature gradient does not depend on the height of the room. It appeared that the higher the room, the higher the temperature of the exhaust air is obtained. This is incorrect. Studies have shown that increasing the height of the room, at constant temperature of excess heat in the upper zone of a few drops. This is logical, as the temperature rising thermal jet decreases with distance from source of heat due to suction of air. The temperature of outgoing air Hood can not be above the temperature of the thermal jet at the level of exhaust vents.
Since the rate of temperature increases vary depending on the height, at the same excess heat build-up temperature is more intense in the low room than in the higher. Therefore, ceteris paribus the value of the gradient for low room more than for high.
In addition, the temperature gradient depends on the capacity and number of heat sources (their "density"), the intensity of the circulation and the method of air exchange. High density of heat sources increases the number of thermal jets, caused by more than a brisk circulation flows. As a consequence, is more intensive exchange between the air of the upper and lower zones and the temperature difference between the working and upper zones decreases. In other words, when a large number of heat sources were rank gradient of A decreases. This explains, in particular, the small value of the temperature gradient for such shops as electrolysis, in which the sources of heat (hot baths) are located in almost the entire floor area.