101 a Temp. and Thermal Environment Flashcards
Thermal comfort is affected by more than just the room temperature. Whether or not a person feels too hot or too cold depends on a combination of:
Environmental factors, including the air temperature, radiant temperature, relative humidity and air velocity. Personal factors such as the level of physical activity and the amount of clothing being worn
The first classic text on the subject was Thermal Comfort (1970) by Povl Ole Fanger, a Danish scientist. Fanger first recognised that it was the combined effect of the six basic parameters which determines human thermal comfort. Fanger stated that three conditions needed to be met for a person to be in whole body thermal comfort:
(1) The body is in heat balance. (2) The sweat rate is within comfort limits. (3) The mean skin temperature is within comfort limits.
The predicted mean vote (PMV) represents
the mean response of a large group of people, in a particular environment, as to how they would rate their ‘thermal sensation’.
Thermal balance is obtained when
the internal heat production in the body is equal to the loss of heat to the environment
The predicted percentage dissatisfied (PPD) is
an index that establishes a quantitative prediction of the percentage of thermally dissatisfied people, who feel too cool or too warm.
The human body operates within a narrow core temperature band between
36.8°C and 37.2°C
The heat balance equation may be expressed as:
M + W + K + C + R – E = S M = Rate of metabolic heat production W = External work performed by the body K = Conductive heat loss or gain C = Convective heat loss or gain R = Radiant heat loss or gain E = Evaporative heat loss S = Heat gained or lost by the body
Factors Affecting Heat Gain 3
(a) Physical Activity(c) Radiant Heat(b) Air Temperature
Factors Affecting Heat Loss 5
(a) Sweating(c) Air Movement(d) Humidity(e) Clothing includingProtective Clothing(b) Acclimatisation
