Thermal Dynamics and Heat Transfer

ASTEC
Training Program

Copyright 2007 Insulating Coatings Corporation

Training
Program

1. The Concept of Heat
2. Heat Transfer (I)
3. Heat Transfer (II)
4. Processes in Radiation
5. Term Definitions
6. ASTEC – Thermal Properties
7. ASTEC – The Total Solution

Module 1
Thermodynamics

The Concept of Heat
(Thermodynamics)

Module 1

Module 1
Thermodynamics

Thermodynamics:

1. Energy is always conserved; it is never lost.
2. Heat always travels from a “hot” region to a “colder”
region.

Therefore, the issue is:
• Flow of Heat
• Heat Flow
•Heat Transfer

Module 1
Thermodynamics

Heat Transfer

Radiation ~ Electromagnetic Waves

Conduction ~ Molecule Movement

Convection ~ Air Current

Module 1
Thermodynamics

Heat Transfer Modes

• Conduction Heat transfer for conduction
and for convection is directly
• Convection proportional to the driving
temperature differential.
• Radiation Double the difference to
double the heat transfer
rate ( T1 – T2 )

Module 1
Thermodynamics

Heat Transfer Modes

• Conduction Heat transfer by radiation is
proportional to the fourth
• Convection power of the temperature
difference ( T14 – T24 ).
• Radiation Small changes in temperature
can create relatively large
changes in radiation heat
transfer rates.

Module 2
Heat Transfer (I)

Heat Transfer (I)
(Modes / Electromagnetics)

Module 2

Module 2
Heat Transfer (I)

Heat Flows Only by…

•Conduction Intensity of conduction
•Convection Amount of convection
•Radiation Rate of radiation
[reflectivity, absorption, and
transmissivity]

Module 2
Heat Transfer (I)

CONDUCTION

•Direct heat flow through matter resulting from a
physical contact.

• Transmission of heat by molecular motion.

Module 2
Heat Transfer (I)

CONVECTION

•Transfer or transportation of heat which is within a gas
or liquid.

“Free convection”
“Forced convection”

Module 2
Heat Transfer (I)

RADIATION

•Transmission through space of energy by means of
electromagnetic rays of varying wavelengths (λ)and
cycles (Hertz).

Module 2
Heat Transfer (I)

Wavelength,
λ (μ m) for
c = 3 x 108 m/s

Module 2
Heat Transfer (I)

Terminology

G Irradiation (solar/thermal radiation)
Radiant flux incident per unit area W/m2
ε Emissivity (thermal radiation)
Rate of radiation emanating from Numeric
the surface of an object compared to
the rate of radiation emanating from
a “black body”

Module 2
Heat Transfer (I)

Terminology

ρ (Radiant) reflectance (Numeric)
Ratio of reflected radiant flux ρG
to incident radiant flux

α (Radiant) absorptance (Numeric)
Ratio of absorbed radiant flux αG

τ (Radiant) transmittance (Numeric)
Ratio of transmitted radiant flux τG

Module 3
Heat Transfer (II)

Heat Transfer (II)
(Electromagnetics and Infrared Energy)

Module 3

Module 3
Heat Transfer (II)

RADIATION

The sun radiates energy
to the earth through 93
million miles of space by
means of rays of many
different wavelengths.

186,286 miles/sec or 300,000 km/sec

Module 3
Heat Transfer (II)

SOLAR RADIATION SPECTRUM
Infrared (Heat rays)
Very Low Frequency
• NIR 0.75 to 3
Low Frequency
• MIR 3 to 6
Medium Frequency
• FIR 6 to 15
High Frequency
• XIR 15 to 1000
Very High Frequency
Ultra High Frequency Visible rays
Ultraviolet rays
Super High Frequency
X rays
Extra High Frequency
Gamma Rays
Cosmic Rays

Module 3
Heat Transfer (II)

SOLAR RADIATION SPECTRUM

Radiation
Spectrum

Infrared rays Visible rays Ultraviolet rays
0.76 to 100 μ m 0.75 to 0.4 μ m 0.4 micron to 100 A
(feels warm) (visible light) (causes sunburn)

Module 3
Heat Transfer (II)

Radiation Intensity

• The closer to the sun a body is, the more rays it will intercept.
• Closer to the sun, the intensity can be so great that we could
not survive.

Module 3
Heat Transfer (II)

Radiation Exposure
• A 7 story building is exposed to more
radiation on the walls than on the roof.
• A single story building receives 70% of
it’s radiation on the roof.

Module 3
Heat Transfer (II)

Radiation: Solar and Thermal

•Solar
•Emanating from the sun
•High energy content
•Short wavelength, High frequency

•Thermal
•Emanating from every object in the universe
•Low energy content
•Long wavelength, Low frequency

Module 3
Heat Transfer (II)

Every Exposed Surface

…Of every object
…In the universe
…With a temperature
…Above absolute zero
…Gives off infrared rays
…In varying amounts

Module 3
Heat Transfer (II)

Absolute Zero

Module 3
Heat Transfer (II)

ABSOLUTE ZERO

Module 3
Heat Transfer (II)

Everything Above
Absolute Zero…

Radiates Energy in
the form of infrared
heat rays.

Module 3
Heat Transfer (II)

Infrared (thermal) heat rays travel…
•Away from every point on
the surface.
•In a straight line.
•In any direction.
•With the greatest
intensity perpendicular to
the surface.
•With the least intensity
parallel with the receiving
surface (zero intensity).

Module 3
Heat Transfer (II)

The radiation from a metal roof, a concrete surface
or other opaque material originates within a few
microns of the surface; hence emissivity (the rate of
radiation emitted by a given surface) is a function of
the surface state of a material rather than of its bulk
properties.

For this reason, the emissivity of a coated or painted
surface is characteristic of the coating rather than of
the underlying surface.

Module 4
Processes in
Radiation

Processes in Radiation
(ρ, α, τ, and ε)

Module 4

Module 4
Processes in
Radiation

Reflectivity
Absorptivity
Transmissivity

Module 4
Processes in
Radiation

What’s a Black Body?

•A theoretical body
•With properties such that…
•It will absorb all (100%) radiation falling on its
surface
•Reflecting and transmitting none
•But it will emit radiation depending on its
absolute temperature.

Module 4
Processes in
Radiation

Black Body Radiation
•Allows no convection
•Reflects no radiation In-coming irradiation
•Transmits no radiation (energy)

Emits radiation Absorbs all radiation
(depending on its (energy converts to heat)
absolute temperature)

(Absorptivity) + (Reflectivity) + τ (Transmissivity) = 1

Module 4
Processes in
Radiation


A+R+T=1

Since there is no Reflectivity R=0
&
Since there is no Transmissivity T=0
Then
Absoptivity must equal one A=1

Module 4
Processes in
Radiation

•No Reflectivity In-coming irradiation
•No Transmissivity (G)
•No Convection

Absorbs all radiation
Emits ( ε ) all radiation (energy converts to heat)

If all in-coming G (energy) is absorbed,
then all in-coming G (energy) is emitted, therefore ε = 1

Kirchoff’s Identity

Module 4
Processes in
Radiation

Emissivity ( ε )
• The rate at which radiant heat energy is emitted by
a given surface.
• “The ratio of the thermal radiation from unit
area of a surface to the radiation from unit area
of a full emitter (black body) at the same
temperature”
• It is a physical property… just like weight, color,
shape, etc.
• All materials have an emissivity ranging from
zero to one (100%).

Module 4
Processes in
Radiation

Emissivity ( ε )
• The rate of radiation emanating from a surface.
(the emissivity of an object’s surface is related to the
ability of that surface to absorb heat rays.)

• Total Emissive Power of a Black Body:

Eb = σT4

Module 4
Processes in
Radiation

Total Emissive Power of a
Black Body
Eb = σT4
q = quantity of heat ( J ) Joule ( 1 J = 1 Watt/s )

σ = Stefan – Boltzmann Sigma: a constant =
constant 0.1714 x 10-8 Btu/h-ft2 or
5.669 x 10-8 W/m2
T = temperature K˚ or
temperature R˚ K˚ = Celsius ˚ + 273.15˚ or
R ˚ = Fahrenheit ˚ + 459.7˚

Module 4
Processes in
Radiation

Common Power Units

1 watt = 3.412 Btu/hr
1 Watt/s = 1 Joule
1 Btu/s = 1.055 Watts
1 Cal/s = 4.19 Watts
1 Ft-lb./s = 1.36 Watts
1 Btu = 1050 Joules
1 Joule = 0.2389 Cal
1 Cal = 4.186 Joules

Module 4
Processes in
Radiation

Grey Body Radiation
•A grey body is a non-ideal emitter or an
imperfect radiator.
•A grey body will:
•absorb some of the energy it will receive.
•reflect some of the energy it will receive.
•emit the energy it absorbs.
•A grey body is opaque: τ = 0

Module 4
Processes in
Radiation

Model of a Grey Body Radiation
In-coming irradiation (G) Reflected energy

Absorbs all radiation
(energy converts to heat)

Emitted ( ε ) energy Convected energy

Module 4
Processes in
Radiation

Grey Body Radiation
A+R+T=1
Since there is no Transmissivity T=0
then
Reflectivity + Absorptivity = 1 A+R=1
Since there is Reflectivity R=>0
then
Absorptivity must be: A=<0
therefore
Emissivity must be less than 1 ε=<1

Module 4
Processes in
Radiation

Emissive Power of a Grey Body
•Real surfaces emit less radiation than ideal
“black body” surface.

•The ratio of actual emissive power [E] to the
emissive power of a black body at the same
temperature [Eb] is called the emissivity.

•It is defined by
ε = E/Eb

Module 4
Processes in
Radiation

Energy Economics
•Office worker requires 200 ft2

•Salary: $30,000/yr
•Value of services: $150/ ft2

•Cost of Energy: $2.25/ ft2 (1985 $)

Module 5
Term Definitions

Term Definitions
(Physics)

Module 5

Module 5
Term Definitions

Definitions of Terms
•Absorptivity
•British Thermal Unit (Btu)
•Conductance (C factor)
•Conductivity (K factor)
•Emissivity
•Reflectivity
•Resistance (R factor)
•U Factor

Module 5
Term Definitions

Absorptivity
• The fraction of thermal radiation incident on a
surface which is absorbed.

Module 5
Term Definitions

British Thermal Unit
• The amount of heat needed to raise the temperature
of 1lb. Water 1 degree Fahrenheit.

Conductance (C Factor)
• The rate of heat flow in Watts per square meter
Kelvin (W/m2K) of any material whether
homogeneous or non-homogeneous.

Module 5
Term Definitions

Conductivity (k Factor)
• Thermal conductivity, k, is the rate of conduction
heat transfer per unit area for a temperature gradient
of 1˚ C/m ( or 1˚ F/ft).

•The units for k are W/(m ˚C) *or Btu/(h ft ˚F)+.

•Thermal conductivity (k) measures the rate of heat
transfer through a material from face to face.
Calculate for any material by multiplying the thickness
in meters by the appropriate k value.

Module 5
Term Definitions

Emissivity
• Ratio of the radiation emitted by a surface to the
radiation emitted by a black body at the same
temperature.

Reflectivity
• The fraction of thermal radiation incident on a
surface which is reflected.

Module 5
Term Definitions

Resistance (R Factor)
• Resistance to heat flow is the reciprocal of C, k, or U:

• 1/C, 1/k, 1/U

•The smaller the C, k, or U factor fraction, and the
larger the R factor, the better the insulation against
heat transfer by conduction.

Module 5
Term Definitions

U Factor
• The rate of heat flow or “overall coefficient of heat
transmission” in Btus in one hour through one sq. ft.
area of the entire depth of ceiling, roof, wall, or floor,
including insulation if any, which will result from a 1˚ F
temperature difference between the air inside and the
air outside.

Module 6
ASTEC Thermal
Properties

ASTEC Thermal Properties

Module 6

Module 6
ASTEC Thermal
Properties


Reflectivity: 86.9%

Module 6
ASTEC Thermal
Properties


Absorptivity: 13.1%

Module 6
ASTEC Thermal
Properties


Emissivity: 90.1%

Module 7
ASTEC
The Total Solution

ASTEC
The Total Solution

Module 7

Module 7
ASTEC
The Total Solution

Heat Transfer
• The best way to reduce heat transfer:
Prevent it from entering the building.

• The best wat to manage heat transfer:
Re-emit it quickly.

Module 7
ASTEC
The Total Solution

Customer Requirements
• Energy saving radiant heat barrier
•Reduced heat transfer
•Better heat management
•Reduced cooling load
•Protection against ultra-violet degradation
• Long lasting waterproofing protection

Module 7
ASTEC
The Total Solution

• Roof structural integrity
• No chipping, no cracking, no flaking
• Corrosion control
• Environmentally friendly products
• Economical solutions
•Attractive and clean finish
•Long life cycle

Module 7
ASTEC
The Total Solution

• Low installation cost
• Brand name recognition
• Low roof maintenance
• Product warranty
• Labor warranty
• Increased roof longevity

Module 7
ASTEC
The Total Solution

Meeting Customer’s Needs
• ASTEC is more than a mere coating:
•Exterior Radiant Insulation & Finish System

• ASTEC greatly reduces radiant heat transfer:
•High solar reflectivity of 0.87

• ASTEC efficiently manages heat transfer
•High thermal emissivity of .91

Module 7
ASTEC
The Total Solution

ASTEC’s radiant heat barrier…

• Reduces surface temperatures by as much as 20˚ C

• Reflects between 80% and 87% or radiant heat (p = 0.80
to 0.87)

• Limits radiant heat absorption between 15% and 20% (α
= 0.14 to 0.20)

• Reduces energy consumption by as much as 40%

Module 7
ASTEC
The Total Solution

• ASTEC’s high density ceramic components:
• Resists ultra-violet degradation
• Maintains its color

• ASTEC products are water based

•ASTEC provides an aesthetic architectural appearance.

Module 7
ASTEC
The Total Solution


• ASTEC’s metal primer seal inhibits corrosion and
prevents oxidation from air and humidity.

• ASTEC’s waterproofing membrane retains its flexibility
and monolithic structural integrity.

Module 7
ASTEC
The Total Solution


• ASTEC’s lower surface temperature provides:
• Thermal shock protection
• Longer roof life cycle

• ASTEC is a world leader
• Applied on structures in more than 30 countries.

Module 7
ASTEC
The Total Solution

• ASTEC is easy to maintain and easy to repair

•Ten (10) year warranty

•ASTEC is applied by trained and authorized applicators
only

•Astec Dealers offer an optional “certified” roof
maintenance program

Module 7
ASTEC
The Total Solution

Cost Analysis / Financial Benefits

• Cost effective installation

•Low cost maintenance

•Easy do-it-yourself repair

•Energy Conservation

Module 7
ASTEC
The Total Solution

Cost Analysis / Financial Benefits

• Lower roof repair cost
• Longer roof life
• Environmentally friendly materials
• Fire safe products: self extinguishing
• Sound attenuation features
• Mildew resistant qualities

Module 7
ASTEC
The Total Solution

ASTEC Strengths

• Over 20 year proven performance

•Over 300 million square feet of applied products

• Fully tested in independent laboratories

• Accepted, approved and specified by several
government agencies in various countries.

•ISO 9001 – 2000 Registered Manufacturing

Module 7
ASTEC
The Total Solution

ASTEC Strengths
• Prestigious client references
•Industrial sector
•Commercial sector
•Petrochemical sector
•Residential Sector
•Military sector

• All marketing claims are scientifically substantiated

Module 7
ASTEC
The Total Solution

ASTEC Strengths
• All dealers are professionally trained

• ASTEC Dealers have full time dedicated staff

• Labor and Product warranty

• Worldwide leadership and international recognition

Module 7
ASTEC
The Total Solution

Next Steps
• Check our references

• Verify our claims

• Compare us with the competition

• Contact your local ASTEC Dealer for a free estimate

Thermal Dynamics and Heat Transfer

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