this presentation provides a basic and brief knowledge about heat transfer methods, and also a quick lock about heat exchanger design and types.

1. HEAT TRANSFER
and
HEAT EXCHANGERS
Collected and Rearranged
By
Mohamed Saad – Mohamed Adel

2. HEAT TRANSFER LAW APPLIED TO HEAT EXCHANGERS

3. Heat Transfer by Conduction
• The transfer of energy
between objects that are in
physical contact
• Transfer of energy by touch

4. Thermal Conductivity of solids

5. Thermal Conductivity of gases

6. Thermal conductivity of liquids

7. The Heat Conduction Equation
Rate of heat
generation
inside control
volume
Rate of energy
storage inside
control volume
Rate of heat
conduction
into control
volume
+ =
Rate of heat
conduction
out of control
volume
+

8. Heat Transfer by Convection
The transfer of energy between
an object and its environment,
due to fluid motion

9. Natural Convection
• Convection – heat
transferred by the
circulation of a fluid (or
gas), such as in a heating
system at home; important
near the surface of the Sun.
• Hot air rises cool
air falls

10. Heat Transfer by Radiation
The transfer of energy to or
from a body by means of the
emission or absorption of
electromagnetic radiation
q = ε σ (Th4 - Tc4) Ac
Th = hot body absolute temperature (K)
Tc = cold surroundings absolute temperature (K)
Ac = area of the object (m2)
σ = 5.6703 10-8 (W/m2K4)
The Stefan-Boltzmann Constant

11. Emissivity coefficient for several selected material
Surface Material
Emissivity Coefficient
- ε -
Aluminum Commercial sheet 0.09
Aluminum Foil 0.04
Aluminum Commercial Sheet 0.09
Brass Dull Plate 0.22
Brass Rolled Plate Natural Surface 0.06
Cadmium 0.02
Carbon, not oxidized 0.81
Carbon filament 0.77
Concrete, rough 0.94
Granite 0.45
Iron polished 0.14 - 0.38
Porcelain glazed 0.93
Quartz glass 0.93
Water 0.95 - 0.963
Zink Tarnished 0.25

12. Heat Exchanger
• A heat exchanger is a piece
of equipment built for efficient
heat transfer from one
medium to another
The main concept is “heat economy”

13. 1) Double pipe heat exchanger
The simplest design for heat exchanger
 consist of two concentric pipes
One fluid flow inside the small pipe and the second
fluid flows in the space between the two pipes

14. 2) Shell and tube heat exchanger
• Shell and tube heat exchangers consist of a
series of tubes. One set of these tubes
contains the fluid that must be cooled.
The second fluid runs over the tubes that are
being heated so that it can absorb the heat
required

17. Baffle type and spacing

18. General design consideration
Factor Tube-side Shell-side
Corrosion More corrosive fluid Less corrosive fluids
Fouling Fluids with high fouling
and scaling
Low fouling and scaling
Fluid temperature High temperature Low temperature
Operating pressure Fluids with low pressure
drop
Fluids with high pressure
drop
Viscosity Less viscous fluid More viscous fluid
Stream flow rate High flow rate Low flow rate

20. 3) plate and frame heat exchanger
• the plate heat exchanger is composed of
multiple, thin, slightly separated plates that have
very large surface areas and fluid flow passages
for heat transfer. This stacked-plate arrangement
can be more effective, in a given space, than the
shell and tube heat exchanger.

21. 4) Spiral heat exchangers :

22. Temperature profile for different types of
heat exchangers

23. Thank you for attention