Heat and they create excess heat in the room the most common harmful. Although the well-being in a strong degree of envy of the temperature conditions, yet because of the body's ability to thermoregulation person is relatively easy to adapt to "an abnormal temperature. However, prolonged exposure to high temperatures worsen health and reduce disability.
Determination of the amount of heat entering into the indoor air, produced by the formulas and graphs, given in references for ventilation. Let us here only for some special cases.
Heat from the machines is usually calculated by the formula
Q - Ny - 860 (kcal / h) (1)
where Ny installed capacity of electric motors;
x - utilization of installed capacity
(Usually 0,9-0,7) p: load factor, taking into account the difference between
hourly power consumption and maximum (range from 0,9 to 0,4);
Of --- simultaneity factor of equipment (ranging from 1 to 0.3) u4 - coefficient of heat transfer in the area (ranging from 0 1 to 0,95).
For machine shops at permanent work and normal load at work without emulsion
Q = A/u-860-0 ,8-0 ,75-0 ,7-0, 6, Ny-860-0, 25 [kcal / h]. (2)
For those plants, but when working with the emulsion of the heat consumed by evaporation. With accuracy sufficient for practice can be considered
Q -= L/u-860-0, 2 [kcal / h]. (3)
In the presence of suction at the local machine (eg, plastics processing)
Q "= / Vy-860-0, 15 [kcal / h]. (4)
For instrumental, mechanical assembly and repair shops due to generally lower load equipment should be considered accordingly:
Q h \ -860-0,22 [kcal / h \ - (5)
Q - L/u-860-0, 18 [kcal / h].
For the experimental machine shops, where the coefficient at the same time an average of about 0,4,
Q = L/u-860-0, 15 [kcal / h], (6)
Q - L/u-860-0, 12 [kcal / h].
Note. Reduced coefficient of radiation is taken to be 3.
For other values of the Cp value of al can
be easily converted by multiplying the value of 3.
for vertical surfaces tabulated values of ak must be multiplied by the ratio of
Heat from people sitting in a room, depending on the type of work they do and the ambient temperature. Heat emitted by man is made up of clear, given out by the "dry heat" of the body, and a hidden, ie heat of water vapor entering the premises during respiration and evaporation from the skin surface.
Table. 2 shows the apparent heat and moisture - the selection of one person under different conditions. Apparent heat release q in kcal / h and vlagovydeleniya d in g / h from a single
Sometimes it is necessary to determine the amount of heat entering the premises of the cooling in it material or product. This heat in the case of transition from one physical state to another (hardening) is calculated by
Q - A [kcal / h], (15) where the G-weight of the cooling in the premises of the material in kg;
with [c-2 - specific heat of the material in liquid and solid states within the considered temperature kka.g / kg deg;
/ "Is the initial temperature of the material in В° C;
n-1 - the melting temperature of the material in В° C;
tK-final material temperature in В° C;
i - the latent heat of melting of the material in kcal / kg;
ft - experienced coefficient taking into account the intensity of heat over time and depends on the structure of the material and the size of his pieces (in the case of cooling of any product ratio ft depends on the weight and shape of products).
Calculation by formula (15) would be fine if we knew the value of ft, but, unfortunately, there are almost no experimental data to determine this factor. Therefore, for periodic flows in a room heated material and cooling it for a few hours to calculate teplopostupleniya take the first hour: in the first hour of the most intense heat and ranges from 30 to 100% of the total heat released during cooling of the material.
Can recommend the following indicative values of the ft:
a) during the cooling of molten material in the form of large masses (in crucibles, ladles, large blanks): weighing more than 300 kg.
during the cooling of solid materials or products: weighing over 200 kg
B = 0,5 0,6;
Accepted but corresponding directories
50-7-100 kg weight
ft - 0, 7: 0,8;
up to 50 kg
b -0,9: 1.
This applies to cases of recurrent revenue in the room heated materials, when the intervals between successive portions over 1 h. They sang the same hot or molten material enters the room continuously and uniformly or periodically, at intervals of less than 1 h, the amount of heat is calculated using the same formula (15), with the coefficient ft = l. In this case, the weight of incoming material G is expressed in kg / h.
Here is an example of calculation of heat release from the cooling of slag inside the smelter.
Every 3 h produced G = Ute slag at / - 1300 В° C. The slag cools the room to <, (= 100 В° C and a ladle with a capacity of 2,000 kg / melt = 1000 В° C / ~ 45 kcal / kg; Ci = 0,22 kcal / kg вЂў deg C 2 = 0.18 kcal / kg вЂў deg.
For this case take the coefficient ft = 0,3.
Number of heat released by (15)
Q = 10 000-0,3 [0.22 (1300 - 1000) - 45 +
- 0,18 (1000 - 100)] l. 820,000 kcal / h.
Teplopostupleniya the premises of solar radiation are taken into account in the heat balance at ambient temperatures 10 В° C and above.
The amount of heat entering the building from solar radiation is determined by the formulas: for glass surfaces
- Fo (loAo [kcal / h] (16)
Ql - FltquKn [kcal / h], (17)
where f * (, n Fn-surface glazing PLI coatings in M1;
/ N - quantity of radiation in kcal / m-h in 1 ml glass surfaces, depending on the orientation of the cross country world, with / and - the quantity of radiation in kkal/m2-ch after 1 M1 surface coating; A0 - coefficient depending on the characteristics of glazing;
Kn - heat transfer coefficient of the coating. When counting teplopostupleniya from solar radiation should be greater of two values:
teplopostuplenie through windows, located by a wall of a room, in the amount of teplopostupleniem through the coating and the lantern;
teplopostuplenie through windows located in two perpendicular walls of the room, by a factor of 0.7 in the amount of teplopostupleniem through the coating and the lantern.