lecture 2 -Concepts in Thermal Comfort.pdf

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1. CONTROL SYSTEMS I

2. Maryam Siddiq
[email protected]
B.Arch.
M.Arch.
PhD

3. Environmental Control Systems-1
Fundamentals of Thermal Comfort
In Passive Architectural Design

4. PASSIVE ARCHITECTURAL DESIGN
Architecture, which involves minimizing the building energy
consumption, has recently gained momentum to become the
current fashion and the main stream in architectural practice and
is called passive architectural design.
PASSIVE-------INERT, INACTIVE, SUBMISSIVE
Passive design Systems use structural and design elements to
minimize the solar gain and therefore keep the indoor
atmosphere comfortable. They are implemented by architects to
minimize the amount of mechanical cooling (air conditioning, for
example) needed to keep the occupants comfortable. Major
factors in Passive Cooling are the facades of a building and the
sun's azimuth angle and angle of altitude.

5. MODERN DAY TERMONOLOGY :
•GREEN ARCHITECTURE
•SUSTAINABLE ARCHITECTURE
•ENGERY EFFICIENT ARCHITECTURE

6. Thermal Comfort
Thermal qualities –such as:
warm, cool, humid, breezy, radiant, cozy
are important experiential qualities of any
architectural space.
They not only influence what people choose to do
there, but how they feel about a space.

13. CONDUCTION
Thebodyconductsheattowhatevertheskinisindirectcontact
with.Conductiveheatlossoccurswhentheskinissubjectedto
eithercoldairorwater,butitisespeciallycriticalinwater,as
yourbodylosesheatabout25timesfasterinwaterthaninairof
thesametemperature.

14. Human Body: Heat Loss
The skin is cooled by conduction through
physical contact with a cooler surface. Like
submerging in a pool of cold water, the body
loses most of its heat in a process called
hypothermia.

15. Convection isheat transferby
mass motion of a fluid such as
air or water when the heated
fluid is caused to move away
from the source of heat,
carrying energy with it.
Convection above a hot surface
occurs because hot air expands,
becomes lessdense, and rises .
Hot water is likewise less dense
than cold water and rises,
causing convection currents
which transport energy.
Convection

16. Heat Loss via convection
The skin is cooled by convection as
surrounding cooler air flows across the skin.
The greater the temperature difference, the
greater the transfer.

17. Radiation
Theheatgeneratedfrom
withinthebodyisgiven-off
tosurroundingatmosphere.
Theskiniscooledby
radiationasheatfrom
theskinislosttothe
surroundingswithoutthe
aidofcoolerairstriking
theskin.

21. HOMEOSTASIS
Most mammals, specially humans, maintain a
constant body temperature by a process known as
homeostasis.
It is necessary for
the body to exactly
balance its total
heat exchange, so
that:

22. Human Body: Heat Gain
Body heat is normally gained through activities such as
exercise and shivering, andalso with the application of
external heat sources.
Human body generates heat through a biochemical
process natural to all mammals, called metabolism.
Metabolism chemically breaks down food and
harnesses energy through cellular respiration.

23. Human Body: Heat Gain
Another heat source for the body is activity

24. Human Body: Heat Gain
Another heat source for the body is activity

29. Physiological Adaptation to Thermal
Stress
ACCLIMATIZATION
Human body tends to regulate its comfort level
in accordance to its surroundings. In cold
regions, the body adapts to a cooler comfort
level. Similarly, in hot weather, the body adapts
to a warmer comfort level.
This creates a range of temperature, humidity and other
factors into something called a “comfort zone”.

30. RELATIVE HUMIDITY:
Relative Humidity is the most commonly used
measurements of moisture content in the air.The key to
understanding relative humidity is to understand that it is
a measure of the ‘actual humidity’, relative to maximum
possible humidity at a given temperature.
APPLICATION:
Relative Humidity readings are used to :
determine human and animal comfort levels,
predict the likelihood of certain crop diseases, and is used
in certain manufacturing environments
effectiveness of crop spraying is also determined by the
relative humidity in conjunction with wind and other
climatic variables.

31. Relative Humidity
Relative humidity (or RH) in % is defined as
the amount of moisture in air compared to
the maximumamount that can exist at a
given temperature without condensation.
For example,
80% RH at 32 degree Celsius means the
moisture content is 80% compared to the
maximum that can exist at this temperature
without condensation.

32. Relative Humidity
The relationship between relative humidity and room temperature
is shown in this graph: