discusses the heat transfer between a Forced Convection Heat Transfer apparatus
and its surroundings, complete with calculations using the steady-flow energy
equation. Once a value for the heat transfer is obtained, the importance of the
right-hand values in the steady-flow energy equation will be considered and
experiment was performed to analyse the heat transfer between the apparatus and
its surroundings. It was important to analyse this in
order to see how efficient the system is whilst it is in use.
following table details the aims of this experiment and how I plan on achieving
To estimate the heat transfer between a Forced Convection Heat Transfer system and its surroundings.
for terms in the steady-flow energy equation.
term of the steady flow energy equation.
steady-flow energy equation in order to calculate the value for “Qin”.
values for each term into the equation.
To examine the relative importance of the right-hand
terms of the steady-flow energy equation.
term individually in order to compare them to each other.
each value contributes to the overall equation.
I predict that the value of Q? will be a negative value as I
believe that there will be some heat loss to the surroundings, as there is no
such thing as a perfect system.
There are several fundamental rules regarding the
thermodynamic behaviour of materials that have been established over the years
as a result of many years of analysis of thermodynamic experiments carried out
by both scientists and engineers alike. These rules are known as the “Laws of
The first law of thermodynamics directly applies to this
experiment and is known as the “Conservation of Energy”. The law states that the total energy of an isolated
system is constant; meaning energy can change state, but cannot be created
There are two flow processes: non-flow and steady-flow. This
report will focus on the use of the law regarding steady-flow processes only.
Steady-flow processes involve mass flow across their boundaries (unlike
non-flow processes), where work is required to push the mass into or out of the
control volume. This work is known as the flow work or flow energy and is
necessary for maintaining a continuous flow through a control volume. It is
important to note that in steady-flow systems, the mass flow of a fluid at any
section is the same as in any other section.
are categorised as being open, closed or isolated. The system that will be used
in the experiment is an open system, meaning it is able to exchange energy and
matter with its surroundings. A closed system exchanges energy but not matter
with its surroundings; and an isolated system does not exchange either with its
surroundings. However, in reality, there is no such thing as a perfectly
isolated system as all systems transfer energy to their surroundings through
loss of heat energy, regardless of how well insulated they are.
Methods and procedures
In order to complete the experiment, the following equipment
will be needed:
Forced Convection Heat Transfer apparatus
The following details the
recommended experimental procedure:
1. Turn on the power switch on the instrument panel.
2. Record the ambient temperature indicated on the
temperature indicator. (Assume this to be the ambient air temperature at the fan
3. Turn on the fan by pressing the GREEN button on the
instrument panel for the fan.
4. Turn on the heater by pressing the GREEN button on the
instrument panel for the heater.
5. Adjust the power control until the ammeter on the
instrument panel reads “4 Amperes”.
6. Record the corresponding voltage value indicated by the
voltmeter on the instrument panel.
7. Turn the thermocouple selector to position 7 which
indicates the discharged air temperature at the pipe outlet.
8. Whilst waiting for the temperature to stabilise, record
other measurements needed using the equipment provided.
9. Once the temperature has stabilised, record its final
10. Finally, record the value of the water column on the
Orifice Plate Pressure Drop Manometer.
Once the experiment is complete, turn off the heater first
and allow the airflow to continue for a while before turning off the fan.
Analysis and Discussion
From my calculations, I obtained a value of -1362.5J for
. As the value is a negative value, this
indicates to me that there is some heat lost to the apparatus’s surroundings. I
am not surprised at this because as discussed earlier, there is no such thing
as a perfectly isolated system.
In order to analyse the importance of the right-hand terms of
the equation, we must first understand the value of each term. The right-hand
terms of the steady-flow energy equation are as follows:
The first term,
the difference in the specified enthalpy of the fluid at the air inlet and
outlet. In terms of this experiment, this value is 40.7kJ/kg.
The second term,
the difference in velocity of the air at the inlet and outlet (where each value
is squared) halved. This value of is 314.36m/s.
The third term,
the value of gravity multiplied by the difference in height of the air inlet
and outlet. In terms of this experiment, this value is 8.76.
From what the values contribute to the equation, for this
system, I would rank the terms in this order (most important to least
I have ranked them in this order as I believe that velocity is a
large contributing factor to the efficiency of a thermodynamic system because
the system must be able to cope with a high velocity of a fluid and must be
able to run effectively. ENTHALPY. I ranked the height
term last as I do not think that this is a significant contributing factor to
the equation. I inputted various numbers of a large range into the equation to
see how it would affect the outcome, but even with a large number (e.g. 1000),
there was not a huge difference.
In conclusion, from carrying out the experiment and the
required calculations, I
obtained a value of -1362.5J for
meaning that there was heat lost to the surroundings, just as I expected there
would be. From using the steady-flow energy equation and analysing my results, I
was then able to examine the importance of the right-hand terms of the
I believe that the experiment was successful as my results were
as I predicted and I met all of my aims and objectives that were set out at the
beginning of this report. I also completed thorough research into the
background theory of the equation which contributed to my overall understanding
of the topic.