UwzuwjskwmskmwlMnzejnsns

1. Forms of Heat
Transfer

2. Introduction
Have you ever wondered , where does heat transfer occur ? For instance ,how is it that you get
burn or hurt when you touch a hot object or surface or when you stay under the sun .
What are the different mechanisms of heat transfer ? Moreover ,how does this process happen ?
In this presentation , we will explore the forms of heat transfer and depict real life examples for us
to discover .

3. H e a t t r a n s f e r i s t h e f i e l d i n
T h e r m o d y n a m i c s i n c h a r g e o f t h e
s t u d y o f t h e g e n e r a t i o n , c o n v e r s i o n ,
e x c h a n g e a n d u s e o f e n e r g y i n f o r m
o f h e a t ( t h e r m a l e n e r g y ) b e t w e e n
d i f f e r e n t s y s t e m s .
H e a t c a n b e t r a n s f e r r e d u s i n g s e v e r a l
m e c h a n i s m s s u c h a s c o n d u c t i o n ,
c o n v e c t i o n , a n d r a d i a t i o n
Heat Transfer

4. Conduction Convection Radiation
Modes of Heat Transfer

5. Conduction
Conduction is the transfer of thermal energy
by crashing between surrounding atoms or
molecules. Conduction happens more easily in
solids and liquids considering the particles are
in closer proximity than in gases because the
particles are positioned further apart.

6. CONDUCTION
T h e m o s t t y p i c a l s o r t o f h e a t
t r a n s m i s s i o n o c c u r s w h e n t w o t h i n g s
c o m e i n t o c o n t a c t w i t h o n e a n o t h e r .
F o r i n s t a n c e , d u r i n g c o o k i n g , w h e n w e
s t i r h o t f o o d w i t h a c o n d u c t i v e o b j e c t ,
l i k e a s p o o n , w e f e e l t h e h e a t a t t h e
l e a d i n g e d g e o f t h e s t i r r e r / s p o o n
b e c a u s e h e a t i s t r a n s p o r t e d f r o m t h e
s o u r c e o f h e a t t o t h e f o o d b y
c o n d u c t i o n . T h e p r o c e s s o f h e a t
c o n d u c t i o n i s w h a t c a u s e s t h i s .
H e a t c a n m o v e f r o m p e r s o n t o p e r s o n , a n i m a l t o
a n i m a l a n d o b j e c t t o o b j e c t . W h e n c r e a t u r e s
h u g , h e a t f r o m t h e w a r m e r b o d y m o v e s t o t h e
c o l d e r b o d y . I n a h u g , h e a t i s t r a n s f e r r e d f r o m
o n e b o d y t e m p e r a t u r e t o a n o t h e r f r o m t h e
p e r s o n w h o i s w a r m e r t o t h e o t h e r .
Cooking
Hug

7. W h e n p l a c e d o n a p e r s o n ' s h a n d ,
i c e c u b e s m e l t m o r e q u i c k l y . T h i s
o c c u r s a s a r e s u l t o f h e a t e n e r g y
b e i n g t r a n s f e r r e d f r o m t h e s k i n ' s
s u r f a c e t o t h e i c e c u b e s .
C o n d u c t i o n c a u s e s t h e h e a t
e n e r g y i n t h e h a n d s t o b e
t r a n s m i t t e d t o t h e i c e , h e a t i n g i t
u p a n d m e l t i n g i t .
C o n d u c t i o n i s t h e m a i n m e a n s o f h e a t t r a n s f e r
w h e n i r o n i n g c l o t h i n g . T h e f a c t t h a t t h e i r o n i s
m a d e o f m e t a l , a g o o d c o n d u c t o r , c a u s e s i t t o
h e a t u p v e r y q u i c k l y . H e a t i s i m m e d i a t e l y
t r a n s f e r r e d t o t h e g a r m e n t w h e n t h e m e t a l i s i n
c o n t a c t w i t h i t .
Melting ice on
the hands
Ironing clothes

8. Convection
Convection is the transfer of thermal energy
by particles moving through a fluid (either a
gas or a liquid). The moving fluid carries
energy with it. The fluid flows from a high
temperature location to a low temperature
location.

9. T h e s t o v e b u r n e r i s t h e h e a t s o u r c e . T h e s t o v e b u r n e r h e a t s
t h e m e t a l p o t t h a t c o n t a i n s t h e w a t e r . T h e m e t a l s t a r t s t o
c o n d u c t h e a t t o t h e w a t e r a s i t g e t s h o t . T h e w a t e r h e a t s u p
w h e r e i t m e e t s t h e m e t a l p a n . W h e n h e a t e d , f l u i d s e x p a n d
a n d l o s e d e n s i t y . A s a r e s u l t , t h e d e n s i t y o f t h e w a t e r a t t h e
b o t t o m o f t h e p o t d r o p s a s i t g e t s h o t t e r . C i r c u l a t i o n
c u r r e n t s d e v e l o p g r a d u a l l y a s a r e s u l t o f d i f f e r e n c e s i n
w a t e r d e n s i t y b e t w e e n t h e p o t ' s t o p a n d b o t t o m . T h e c o l d e r
w a t e r t h a t w a s p r e v i o u s l y i n t h e p o t i s b e i n g r e p l a c e d w i t h
h o t w a t e r a s i t s t a r t s t o r i s e t o t h e t o p . A n d t h e w a t e r t h a t
w a s p r e v i o u s l y a t t h e t o p o f t h e p o t , w h e r e i t w a s c o l d e r ,
g o e s d o w n t o t h e b o t t o m , w h e r e i t i s h e a t e d a n d s t a r t s t o
r i s e . O v e r t i m e , t h e s e c i r c u l a t i o n c u r r e n t s g r a d u a l l y f o r m
a n d g i v e h e a t e d w a t e r a m e c h a n i s m t o m o v e e n e r g y f r o m
t h e p o t ' s b o t t o m t o t h e s u r f a c e .
CONVECTION
Boiling Water

10. C o n v e c t i o n a l s o o c c u r s I n s i d e o f a h o t a i r
b a l l o o n b y h e a t i n g t h e i n s i d e o f t h e a i r w i t h a
b u r n e r l o c a t e d a t t h e b o t t o m o f t h e b a l l o o n ,
t h i s t h e n m a k e s t h e a i r i n s i d e o f t h e b a l l o o n
l e s s d e n s e o r l i g h t e r t h a n t h e c o o l e r a i r o n t h e
o u t s i d e , c a u s i n g t h e b a l l o o n t o f l o a t u p w a r d s .
T h i s i s a f o r m o f b u o y a n c y c o n v e c t i o n .
Hot Air Balloon

11. • S u m m e r d a y s e x h i b i t s e a b r e e z e s b e c a u s e t h e l a n d
w a r m s u p m o r e q u i c k l y t h a n t h e w a t e r .
D u e t o i t s l o w e r d e n s i t y t h a n c o o l e r a i r , w a r m a i r r i s e s .
C o o l e r a i r f r o m t h e o c e a n m o v e s o v e r l a n d t o r e p l a c e
t h e w a r m a i r a s i t r i s e s . A s e a b r e e z e i s c a u s e d b y t h i s
a l t e r n a t i n g f l o w o f w a r m a n d c h i l l y a i r .
O n t h e o t h e r h a n d , d u r i n g n i g h t t h e l a n d s u r f a c e c o o l s
m o r e q u i c k l y t h a n t h e s e a s u r f a c e . C o o l e r l a n d a i r m o v e s
o u t t o s e a t o r e p l a c e t h e w a r m e r o c e a n a i r a s i t r i s e s
A i r c o n d i t i o n e r s a r e c o n t i n u o u s l y u t i l i z e d o n a w a r m s u m m e r
d a y . T h e v e r y c o n c e p t o f c o n v e c t i o n i s u s e d i n t h e c o o l i n g
p r o c e s s o f a i r i n a i r c o n d i t i o n e r s . T h e p r i m a r y m e t h o d o f
c o o l i n g i s r e f r i g e r a t i o n , a f o r m o f c o n v e c t i v e h e a t t r a n s f e r .
A i r c o n d i t i o n e r s d i s c h a r g e t h e c o o l e d a i r i n t o t h e
e n v i r o n m e n t . N o w t h a t i t i s d e n s e r t h a n t h e w a r m a i r , t h e
c o l d a i r s i n k s . L e s s d e n s e t h a n c o o l a i r , w a r m a i r r i s e s a n d i s
p u l l e d i n b y t h e a i r c o n d i t i o n e r . A c o n v e c t i o n c u r r e n t i s
c r e a t e d a s a r e s u l t , c o o l i n g t h e s p a c e .
Breeze Air Conditioning

12. Radiation
Radiation is the transfer of heat energy
through space by electromagnetic radiation.
Most of the electromagnetic radiation that
comes to the earth from the sun is invisible.
Only a small portion comes as visible light.
Light is made of waves of different
frequencies

13. RADIATION
R a d i a t i o n a l s o t r a n s f e r s t h e r m a l e n e r g y b e t w e e n
b o d i e s s e p a r a t e d b y a c o l d e r m e d i u m . T h e s u n ’ s r a y s
w a r m t h e E a r t h e v e n a f t e r p a s s i n g t h r o u g h t h e
c o l d e s t p a r t o f E a r t h ’ s a t m o s p h e r e , t h e m e s o s p h e r e .
T h e S u n e m i t s e n e r g y i n t h e f o r m o f s h o r t - w a v e
r a d i a t i o n , w h i c h i s w e a k e n e d i n t h e a t m o s p h e r e b y
t h e p r e s e n c e o f c l o u d s a n d a b s o r b e d b y g a s m o l e c u l e s
o r s u s p e n d e d p a r t i c l e s . A f t e r p a s s i n g t h r o u g h t h e
a t m o s p h e r e , s o l a r r a d i a t i o n r e a c h e s t h e o c e a n i c a n d
c o n t i n e n t a l l a n d s u r f a c e a n d i s r e f l e c t e d o r a b s o r b e d .
Sunlight

14. T h e t h e r m a l r a d i a t i o n f r o m t h e f i r e s p r e a d s o u t i n
a l l d i r e c t i o n s a n d i s a b l e t o r e a c h y o u . T h i s t h e r m a l
r a d i a t i o n i s m o s t l y i n t h e f o r m o f i n f r a r e d w a v e s
a n d v i s i b l e l i g h t . I n c o n t r a s t , t h e c a m p f i r e h e a t
t r a n s f e r r e d v i a c o n v e c t i o n s h o o t s s t r a i g h t u p i n t o
t h e s k y a n d n e v e r r e a c h e s y o u ( i . e . h o t a i r b i l l o w s
u p w a r d s ) . T h e r e f o r e , w h e n y o u a r e s i t t i n g b e s i d e a
c a m p f i r e , a l m o s t a h u n d r e d p e r c e n t o f t h e h e a t t h a t
y o u r e c e i v e f r o m t h e f i r e i s t r a n s f e r r e d t h r o u g h
t h e r m a l r a d i a t i o n . T h i s i s w h y t h e s i d e o f y o u r b o d y
f a c i n g t h e f i r e g e t s h o t w h i l e t h e s i d e f a c i n g a w a y
f r o m t h e f i r e s t a y s c o l d .
Campfire
RADIATION

15. Reference
•https://flexbooks.ck12.org/cbook/ck-12-middle-school-physical-science-flexbook-2.0/section/15.6/primary/lesson/convection-
ms-ps/
References :
•https://www.weather.gov/jetstream/heat#:~:text=Radiation%20is%20the%20transfer%20of,of%20waves%20of%20different%2
0frequencies.
•https://www.wtamu.edu/~cbaird/sq/mobile/2015/02/26when-i-sit-by-a-campfire-how-does-its-hot-air-heat-
me#:~:text=The%20thermal%20radiation%20from%20the,i.e%20hot%20air%20billows%20upwards).
•https://conceptgroupllc.comglossarywhat-is-radiation-heat-
transfer#:~:text=Radiation%20heat%20transfer%20occurs%20via,separated%20by%20a%20colder%20medium.
•https://www.britannica.com/science/thermal-radiation
•https://www.engproguides.com/hvac-heat-
transfer.html#:~:text=keep%20it%20simple.-,Convection,surface%20at%20a%20different%20temperature.
•https://physicsmax.comland-and-sea-breezes-6562
•https://hotairflyer.com/is-balloon-conduction-convection-radiation/
•https://www.physicsclassroom.com/class/thermalP/Lesson-1/Methods-of-Heat-Transfer