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PRACTICAL WORK №5

                             DETERMINATION OF THE HUMAN THERMAL STATE


                         1 OUTCOMES
                         Become  familiar  with  the  methodology  of  determination  of  the  human
                  thermal state.

                         2 DURATION OF CLASS
                         The class duration is two academic hours.

                         3 BASIC THEORY
                         Normal  thermal  health  occurs  when  body  heat  release  (biology  heat
                  production)  Q   is  fully  perceived  by  environment  Q ,  i.e.  when  there  is  a  heat
                                  hb
                                                                                e
                  balance. Heat balance equation of "human-environment" is as follows:
                                                Q   q   q cloth .    q rad .    q s .g .    q ,                                 (5.1)
                                                                                . b
                                                   . c
                                           hb
                  where q – convection (heat) due to the flowing of air around the body;
                           c
                         q cloth.   –  heat  conduction  (diathermancy,  thermal  conductivity)  through
                  clothing;
                         q rad.  - radiation to the surrounding surface;
                         q  – heat release through sweat glands;
                           s.g.
                         q – heat through respiration (air-breathing).
                           b.
                         Convective heat transfer is determined by Newton's law:
                                                            q  . c   F e t surf .  t   amb . ,                                     (5.2)
                                                    . c
                  where α  – convection heat transfer coefficient (at normal microclimate parameters
                           c.
                                 2 о
                  α =4,06W/m · С);
                   c.
                                                                               о
                         t surf.  – temperature of the human body's surface,  С;
                                                         о
                         t amb.  – ambient temperature,  С;
                         F  – effective surface of the human body (the size of the effective surface of
                           е
                  the  body  depends  on  its  position  in  space  and  is  approximately  50–80%  of  the
                  geometrical external surface of the human body); for practical calculations is taken
                            2
                  F =1,8m .
                    е
                         The size (value) and direction of convective heat transfer from the human to
                  environment  is  mainly  determined  by  the  ambient  temperature,  atmospheric
                  pressure, mobility and relative humidity of the air.
                         Diathermancy  (heat  conduction)  through  clothing  is  determined  by  the
                  equation of Fourier:
                                                         
                                                                              )
                                                           q cloth .    0    F e (t surf .   t amb . ,                                  (5.3)
                                                          0
                  where α  – thermal conductivity of the fabrics of clothing of person, W/(m∙°С);
                           0
                         ∆  – fabric’s thickness of the human clothing, m.
                           0
                         Radiation  to  the  surrounding  surfaces:  thermal  energy  from  the  hot  body
                  surface is converted into a radiant energy and transmitted through the air to another
                  colder surface, where, in turn, is converted again into the heat. Radiant flux (flux
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