Figure 1: Temperature gradient of conduction through a wall
Figure 2: Picture showing the movements of the regions
Figure 3: Diagram showing the boundary layers of forced flow over a cylinder.
Figure 4: Surfaceradiating heat to the surroundings
1
3
2
4
e
ating Element with matte black finish placed in the duct. (3)Heat transfer service unit H110 used to show the various data. (4) Thermocouple that can be adjusted.
T
9
Anemometer
T
10
Heating Element
Throttle Plate
y
turning thermocouple, we are able to determine the local heat transfer around the duct.
diation H110. Air flows upwards through the duct and eventually across the heating element. Its temperature recorded at T
9
and T
10
.
Table 1: Data collated for free convection
Table 2: Data collated for forced convection at medium flow
Figure 8: Comparisons between the three correlations (Q
conv
vsQ
total
)
Table 3: Data collated for free convection
ure 9: Graph showing how h varies with angle for natural convection
Table 4: Data collated for forced convection at medium flow
re 10: Graph showing how h varies with angle for forced convection
NANYANG TECHNOLOGICAL UNIVERSITY
COMBINED HEAT TRANSFER BY FREE CONVECTION AND RADIATION
1.
OBJECTIVES
The objectives of this laboratory project are to:
•
Determine the combined (radiation and convection) heat transfer (Q
rad
+ Q
conv
)
from a horizontal cylinder, under natural and forced convection conditions, over a
wide range of power input and corresponding surface temperatures.
•
Explore the effects of locations of measurement in determining the local heat
transfer around the duct.
P3.22
COMBINED HEAT TRANSFER BY FREE CONVECTION AND RADIATION
NANYANG TECHNOLOGICAL UNIVERSITY
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View Full DocumentNANYANG TECHNOLOGICAL UNIVERSITY
COMBINED HEAT TRANSFER BY FREE CONVECTION AND RADIATION
2.
INTRODUCTION
There are three fundamental modes to heat transfer, namely conduction, convection
and radiation. Each of the modes of transfer has its own unique way of transferring
thermal energy. Each of them also has their own equations that characterize the flow
of heat and also their respective heat transport coefficient terms.
All three modes of heat transfer are generally present in varying degrees in almost
physical problems concerning heat transfer.
The next three subchapters will briefly explain some of the concepts in heat transfer.
2.1
CONDUCTION
Conduction deals with the transfer of thermal energy through a
material without itself moving. It is described as the flow of heat due to interactions
between molecules in a material. When this happens, there is a transfer of energy
between more energetic molecules (due to being in a region of higher temperature)
and molecules possessing higher energy (due to being in a region of lower
temperature). This phenomenon is fundamentally a diffusion process that occurs at a
microscopic level. Whenever a temperature gradient exists in a medium, heat
conduction will almost definitely occur.
At a more macroscopic level, the heat transfer per unit area normal to the direction of
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 Spring '09
 LOH
 Physics, Convection, Force, Heat, Radiation, Heat Transfer, Nanyang Technological University

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