The presentation includes heat flux, mathematical expression, examples, Radiation and total surface heat flux.

2. SURFACE HEAT FLUX

3. Engineer Muhammad Tanveer
GROUP NO. 07
PRESENTED TO
Muhammad Sajid Liaqat 14083123-022
Faran Hassan 14083123-023

4. CONTENTS
EXPLAIN
EXAMPLE
FORMULA
HEAT
FLUX

5. “Heat flux is defined as the amount
of heat transferred per unit area per unit time
from or to a surface”.
In SI system its units are
W/ m2
or J/ m2s
Heat rate is a scalar quantity, while heat flux is
a vector quantity.

6. Ts = Surface temperature
Tm = Mean fluid temperature
hx = Local heat transfer coefficient
qs = Surface heat flux

7. This effect can be observed in several
situations like when a tube or a pipe is
subjected to:
1. Radiation
2. Electrical heating resistance
(Uniform from all directions)

8. Radiation

9. Let a pipe exposed to radiation and it has a
constant surface heat flux and different inlet
and exit temperature as shown in figure
Radiation

10. For constant surface heat flux the rate of heat
transfer can be written as
And from general thermal analysis we also
have
So,

11. Variation of the pipe surface temperature and
mean temperature fluid can be easily
observed from following graph

12. Developing region
LMT

13. From previous equations mean fluid
temperature at the exit of tube can be written
as
The surface temperature in case of constant
surface heat flux can also be calculated from

14. By re-arranging it can be written as
In fully developed region, the surface
temperature will also increase linearly in the
flow direction and h is constant so,

15. THANK YOU!