Review of
GasVapor Mixtures and AirConditioning
We will be concerned with the mixture of dry air and water vapor. This mixture is
often called atmospheric air.
The temperature of the atmospheric air in airconditioning applications ranges from
about 10
REFRIGERATION
It is artificial "industrial"
process to keep a certain
space at temperature less
than ore higher than the
surroundings
1 Refrigeration cycles

Carnot refrigeration cycle.
A vapor compression refrigeration
cycles:
i simple saturation
AIR CONDITIONING
It is artificial process.
The target of this process is
an environmental control to
satisfies a human comfort,
industrial or production
conditions
Environment control
Du i g ai o ditio i g A C the follo i g
parameters must be controlled:
Extended surfaces fins
x
i
Sec ii
Q
i
Root
Tip
Modeling
Definitions
Where;
P
area of fin cross section normal to
conduction direction
perimeter of fin cross section
normal to conduction direction
Apply first law of Th.D
=
+
=
=

=
+
Since
=
Special
Design conditions:
1 External design conditions:
External design conditions depend on:
i the building location and
ii Season
The external design conditions for some
cities in USA are listed in table 43, text
book.
The external design conditions for KS
HEAT TRANSFER BY
CONVECTION
What is convection
It is a mode of heat transfer occurs
between a solid boundary
(
surface) and fluid.
If the fluid is forced to move against
the boundary this type of
convection is named
forced
co ectio
What is convection _c
Spherical wall conduction
One dimensional conduction
through radial direction only:
Notes:
Sphere surface area=
Spherical shell volume=
Where, r sphere radius and r
spherical shell radius thickness.
r
r+ r
Energy stored within the spherical shell
Rate of
Conduction #2
Cylindrical wall:
Conduction through
radial direction
r
r+ r
The tube length along its axis is Z
For steady conduction without internal
heat generation and constant thermal
conductivity
(3)
From equation #3
B.C.
1)
T=T1 at r =r1
2) T=T2
Conduction
Conduction with internal heat
generation
1 Plain wall
The general one dimensional conduction
equation in a plain wall is written as;
(1)
For steady state conduction with constant
thermal conductivity equation (1) re write as;
(2)
The solut
Conduction
Fourier equation
Q A
Q 1/L
Q T (T1T2)
Q A T/ x
Q=K A T/ x
T2
T1
x
Q
Heat at a point
T
(a)
T
q
(b)
q
X
Q is ve
is +ve
X
Q is + ve
is ve
General conduction equation
Plain wall:
Assume a plain wall with height H, width W,
thermal conductivity
Akhbar Elyom
Academy
Faculty of Engineering
Mechanical
Engineering Dept.
3 rd year Production & printing Tech.
Heat transfer &
Air conditioning
Contents
1 Heat transfer:
i) Introduction to heat transfer
ii) Introduction to conduction
iii) One dimens