Good morning, everyone.
Welcome to your Heat Transfer Experiment Number Four, Combined Heat Transfer by Natural Convection
and Radiation.
In order to do this experiment, you need two equipment.
Number one, the service unit.
Number two, the module of HT14.
This module is called Combined Convection and Radiation Module.
It's actually a hollow cylinder with a fan on the bottom and weights, anemometer, and
a thermal couple in the middle, and with a heater, and heated cylinder, and another thermocouple
on top.
Because this is the natural convection, so we're not going to use the fan.
But we need to keep the plate to be completely open so that air flow could get into the cylinder
and travels in this direction.
And in the middle, we have anemometer.
The anemometer is going to be used to measure the air flow velocity, since this is, again,
the natural convection.
So we do not use this one.
But we do need to know the air flow temperature.
So this is measured by a thermocouple labeled "nine".
So we need to connect this one to T9.
On top, we have a heater, and we have, actually, a small heated cylinder ran through like this
way.
And we'll have another thermocouple labeled T10, labeled as 10, to measure the surface
temperature of the heated cylinder.
So we need to connect this one to T10.
For the heater, we'll also need to provide a voltage and a current, so we need to connect
the heater to the service unit.
So now those HT14 module has been connected to the service unit.
Let's power the service unit on.
And let's turn on the service unit.
So, the purpose of this experiment is called natural convection and radiation.
So you will be able to actually compare the contribution to the heat transfer rate by
natural convection and also by the radiation.
In order to do that analysis, or calculation, you need some information.
The information includes the air flow temperature, which actually will be measured by thermocouple
T9.
So this T9 is also something called T infinity, T sub infinity.
That's the air flow temperature we're going to use for radiation calculation.
And the other information that you also need, that's the surface temperature of the heated
cylinder.
This is in the data analysis, a formula called T sub s.
T sub s means the surface temperature, so this is actually will be measured by a thermocouple
10.
This is T10.
In order to compare the contribution from natural convection and radiation, we actually
need to see how those contributions change with temperature.
So you need to have a different surface temperature.
How you could have different surface temperature?
You need to have different voltage input for the heater.
So in this experiment, you actually will try four different sets of voltage input.
In order to demonstrate over here, I'm going to use a voltage input for group number one
only.
If you are in different group numbers, let's say group number two, group number three,
you need to refer to the manual to get to your voltage input.
So what I'm going to do here is try to use the voltage input for group number one only.
For group number one, the first set of data we need to connect is for voltage input equal
to 5 volts.
So now, let's change the voltage to 5 volts.
This is the voltage input, 5 volts, and you will also be able to get the current, which
is most of time is going to be also constant.
Then you need to turn the knob to T10 over here to carefully monitor the temperature
changes of the surface temperature.
Now if you notice, this one hasn't been changed for 90 seconds.
This means the surface temperature now has reached a steady state.
So this is a steady state temperature value.
So now you will be able to start to collect your first set of data, which includes the
voltage, the current, the surface temperature, T10, and the air flow temperature, T9.
So that's your first set of data.
Then you have to change the voltage input to 8 volts.
Again, this is the voltage input for group number one only.
You need to refer to the manual to get your voltage input.
So this is the voltage input, 8 volts.
Then turn the knob to T10.
You may have to wait for 20 to 30 minutes to let the situation become stable, something
we call steady state.
And once you see this temperature, T10, hasn't been changing for, like, 90 seconds, then
that's going to be a stable temperature.
Then you can start to collect your second set of data, which includes the voltage input,
the current, and the temperature value, T10, and also, again, the air flow temperature,
T9.
So this is going to be your second set of data.
Then you need to repeat the procedure like this for voltage input equal to 12 volts and
voltage input equal to 15 volts.
Again, this is the voltage input for group number one only.
For the other groups, you need to refer to the manual.
Each of those voltage inputs, you may have to wait about 20 to 30 minutes to let the
surface temperature value become stable.
Then you will start collecting your data points for the voltage, and current, and temperature
value, T10, and also temperature value, T9.
So that's going to be your data set number three and data set number four.
Once you have those four sets of data, then you will be able to use the formula to do
the analysis to compare the contribution of the heat transfer rate by natural convection
and by radiation.
That's all for this experiment.