1. Thermal balance of the human body
Marianna Luoma
Literature:
Achieving the desired indoor climate, pages 91-92
Therelkeld, J.L., Thermal Environmental Engineering
Seppänen, O., Ilmastointitekniikka ja sisäilmasto

2. Thermal comfort
Thermal comfort means conditions in which the person is satisfied with the thermal conditions
In practise: The person can not say whether he would prefer warmer or cooler environment
The core temperature of the body should be ºC, although the temperature of the environment would have great variations
The body core temperature can be measured with a thermometer
The skin temperature may vary more

3. Introduction Human body is like a heat engine
The body converts the chemical energy of its food into work and heat
The harder we work, the greater is the amount of heat we reject (отбр|а́сывать)
Heat rejection occurs primarily from the body surface
Through blood circulation, heat is transported to the skin
From the skin the heat is transported to the environment

4. The heat balance equation of the human body
Heat exchanges between the body and the environment
M - W = E + R + C + K + S, where
M = energy gained from metabolism (обме́н веще́ств)
W = work accomplished
E = evaporation exchange
R = radiant exchange
C = convection exchange
K = conductive exchange
S = heat energy stored in the body
(for heat balance S=0)

5. Estimates of metabolic rate for various types of activities
Unit met (1 met = 58 W/m2)
Sleeping
Sitting quietly
Light work
Moderate work
Heavy work, etc.

6. Body regulatory process against heat or cold
The body has regulation means for adjusting itself to heat or cold.
The basic purpose of these adjustments is to prevent chance of body interior temperature which would impair the vital organs.

7. Neutral zone
For a man exercising with moderate rate, there is a narrow range of atmospheric conditions in which the body needs to take no action to maintain its heat balance.
The body is neutral to feelings of heat or cold.

8. Conditions colder than neutral zone
The body decreases the blood flow at the body surface and by additional heat prduction.
Blood vessels adjacent to the skin constrict, preventing flow of blood and transport of heat to the immediate outer surface.
Through spontaneous increase of activity and by shivering (дрожь), body heat production is increased.
Beyond this range of conditions, the body is unable to combat cooling.
-30 ºC

9. +27 ºC

10. Conditions warmer than neutral zone
Surface blood vessels dilate (расш|иря́ть) and allow blood flow as close as possible to the outer surface.
The skin temperature increases, providing a greater temperature difference for loss of heat by convection and radiation.
The sweat glands (потова́я железа́) become highly active and drenching (пром|а́чивать) the body surface with perspiration (поте́ние).
This is the last line of defense.

11. Clothing
Clothing assists the body to maintain its proper heat balance.
Body temperature is greater than skin temperature
Skin temperature is greater than temperature of clothing surface
Temperature of clothing surface is greater than environmental temperature

12. Clothing insulation It is property of the clothing itself.
It represents the resistance to heat transfer.
Clo unit
One Clo unit is the thermal insulation required to keep a sedentary (сидя́чий) person comfortable at 21 ºC and 0,1 m/s.