Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

E2 – RADIANT HEAT TRANSFER
Objectives
In this experiment we will demonstrate some of the laws of radiant transfer (StefanBoltzmann Law, Area Factor) as we measure heat energy from the heat source
...
Of the three methods, radiation is different because it describes
energy transfer that needs no medium or conductor
...

Description of Apparatus
Figure 1 shows a diagram of radiant heat transfer, with heat and light sources at the ends
...
A Control Box provides on/off controls for the
heater source and a control to vary power of the heater
...

Heat Source

Filter
Holder

Filter
Holder

Heat Flux
Sensor

Light
Source

Lux
Meter

Control Box

Scale

Figure 1: Arrangement of radiant transfer apparatus
Theory of Radiant Heat Transfer
As the radiation from a source hits the surface of an object, its energy will split into three
parts: (1) some radiation may be transmitted through the body leaving the body unaltered;
(2) some may be absorbed by the body raising its temperature; and (3) some may be
reflected
...
m-2), Ta is ambient temperature (K or oC),
Tb is the temperature of a black body (absolute) (K or oC), P is power (W), Ab is the area
of black body (m2), and 𝜎 is the Stefan-Boltzmann Constant (5
...
m-2
...

Area Factor

As shown in Figure 3 (a), an aperture reduces the normal radiation on the surface (Ee1) to
a new lower value (Ee2)
...


Experiments

𝐴𝑓 =

𝐸 𝑒2
𝐸 𝑒1

(5)

The experiments are split into two parts: in part 1, the measurement of Stefan-Boltzmann
law and part two, measurement of area factor
...

Procedure:
1
...

3
...

5
...

7
...


Create a table similar that Table 1 shown in Appendix A
...

Fit a Filter Holder between the heat source and the Heat Flux Sensor (near to the
Heat Flux Sensor)
...
This will work to hide the
sensor, blocking the heat from the source reaching the sensor
...

Switch on the heat source and adjust its control to 8% to give T1 around 40 degrees
at the heater and wait for the heater temperature reading to settle
...

Remove the Filter Holder and fit the Heat Flux Sensor to its position, and then move
the Heat Flux Sensor exactly 100 mm (0
...
Wait for its reading to reach a peak value, and then note the value
...


Move the Heat Flux sensor back to the far end of the frame and wait for its reading
to return to zero
...

Again move the Heat Flux sensor, to 100 mm (0
...

Continue hiding and exposing the sensor for heater temperatures in 20°C steps up
to a maximum T1 of 130°C
...


10
...

12
...
Convert the temperature into Kelvin and find its value to the power 4
...
Create a chart of irradiance (vertical axis) against T4 (See Equation 3)
...

3
...

Procedure:
1
...

3
...

5
...

7
...


9
...

11
...

13
...

Fit the Heat Flux Sensor as far away on the frame as possible from the heat
source (towards the light source)
...

Fit the shiny-shiny absorption plate to Filter Holder l
...

Fit Filter Holder 2 (empty) at 120 mm away from the heat source
...

Adjust its control to 61 % to give T1 of approximately 130°C, and wait for the
readings to settle
...
2 m) away from the heat source to
expose directly to the heat source
...

Move the Heat Flux sensor back to the far end of the frame and wait for the sensor
reading to return to zero
...

Move the Heat Flux Sensor exactly 200 mm (0
...
Wait for its reading to reach a peak value, then note the
value
...

Repeat for the other apertures as follows: 10, 15, 20, 25, 30, and 35 mm
...

2
...


Calculate the area of each aperture from its diameter
...

Create a chart of area factor (vertical axis) against aperture size
...


Comment on your results
...


References
1
...
, Heinemann
International Literature & Textbooks, UK
...
McCabe W, Smith J, Harriott P, Unit Operations of Chemical Engineering, 7th Ed
...


Appendix A
Table 1: Results table for Stefan-Boltzmann Law

Table 2: Results table for Area Factor

4



---