IntroductionThis reportdiscusses the heat transfer between a Forced Convection Heat Transfer apparatusand its surroundings, complete with calculations using the steady-flow energyequation. Once a value for the heat transfer is obtained, the importance of theright-hand values in the steady-flow energy equation will be considered andevaluated.Theexperiment was performed to analyse the heat transfer between the apparatus andits surroundings.
It was important to analyse this inorder to see how efficient the system is whilst it is in use. Thefollowing table details the aims of this experiment and how I plan on achievingthem: Aims Objectives To estimate the heat transfer between a Forced Convection Heat Transfer system and its surroundings. · Measure values for terms in the steady-flow energy equation. · Calculate each term of the steady flow energy equation. · Rearrange the steady-flow energy equation in order to calculate the value for “Qin”. · Substitute my values for each term into the equation.
To examine the relative importance of the right-hand terms of the steady-flow energy equation. · Examine each term individually in order to compare them to each other. · Discuss what each value contributes to the overall equation. I predict that the value of Q? will be a negative value as Ibelieve that there will be some heat loss to the surroundings, as there is nosuch thing as a perfect system.
Background TheoryThere are several fundamental rules regarding thethermodynamic behaviour of materials that have been established over the yearsas a result of many years of analysis of thermodynamic experiments carried outby both scientists and engineers alike. These rules are known as the “Laws ofThermodynamics”.The first law of thermodynamics directly applies to thisexperiment and is known as the “Conservation of Energy”. The law states that the total energy of an isolatedsystem is constant; meaning energy can change state, but cannot be creatednor destroyed.There are two flow processes: non-flow and steady-flow.
Thisreport will focus on the use of the law regarding steady-flow processes only.Steady-flow processes involve mass flow across their boundaries (unlikenon-flow processes), where work is required to push the mass into or out of thecontrol volume. This work is known as the flow work or flow energy and isnecessary for maintaining a continuous flow through a control volume. It isimportant to note that in steady-flow systems, the mass flow of a fluid at anysection is the same as in any other section. Thermodynamic systemsare categorised as being open, closed or isolated. The system that will be usedin the experiment is an open system, meaning it is able to exchange energy andmatter with its surroundings. A closed system exchanges energy but not matterwith its surroundings; and an isolated system does not exchange either with itssurroundings.
However, in reality, there is no such thing as a perfectlyisolated system as all systems transfer energy to their surroundings throughloss of heat energy, regardless of how well insulated they are. Methods and proceduresIn order to complete the experiment, the following equipmentwill be needed:· Forced Convection Heat Transfer apparatus· Measuring tape· Vernier calliper The following details therecommended experimental procedure:1. Turn on the power switch on the instrument panel. 2. Record the ambient temperature indicated on thetemperature indicator. (Assume this to be the ambient air temperature at the faninlet.
)3. Turn on the fan by pressing the GREEN button on theinstrument panel for the fan. 4. Turn on the heater by pressing the GREEN button on theinstrument panel for the heater. 5. Adjust the power control until the ammeter on theinstrument panel reads “4 Amperes”.
6. Record the corresponding voltage value indicated by thevoltmeter on the instrument panel. 7. Turn the thermocouple selector to position 7 whichindicates the discharged air temperature at the pipe outlet. 8.
Whilst waiting for the temperature to stabilise, recordother measurements needed using the equipment provided. 9. Once the temperature has stabilised, record its finalvalue. 10.
Finally, record the value of the water column on theOrifice Plate Pressure Drop Manometer. Once the experiment is complete, turn off the heater firstand allow the airflow to continue for a while before turning off the fan. Analysis and DiscussionFrom my calculations, I obtained a value of -1362.5J for . As the value is a negative value, thisindicates to me that there is some heat lost to the apparatus’s surroundings. Iam not surprised at this because as discussed earlier, there is no such thingas a perfectly isolated system.In order to analyse the importance of the right-hand terms ofthe equation, we must first understand the value of each term.
The right-handterms of the steady-flow energy equation are as follows: The first term, isthe difference in the specified enthalpy of the fluid at the air inlet andoutlet. In terms of this experiment, this value is 40.7kJ/kg. The second term, isthe difference in velocity of the air at the inlet and outlet (where each valueis squared) halved.
This value of is 314.36m/s.The third term, isthe value of gravity multiplied by the difference in height of the air inletand outlet. In terms of this experiment, this value is 8.76. From what the values contribute to the equation, for thissystem, I would rank the terms in this order (most important to leastimportant):I have ranked them in this order as I believe that velocity is alarge contributing factor to the efficiency of a thermodynamic system becausethe system must be able to cope with a high velocity of a fluid and must beable to run effectively. ENTHALPY.
I ranked the heightterm last as I do not think that this is a significant contributing factor tothe equation. I inputted various numbers of a large range into the equation tosee how it would affect the outcome, but even with a large number (e.g. 1000),there was not a huge difference. ConclusionsIn conclusion, from carrying out the experiment and therequired calculations, Iobtained a value of -1362.5J for ,meaning that there was heat lost to the surroundings, just as I expected therewould be. From using the steady-flow energy equation and analysing my results, Iwas then able to examine the importance of the right-hand terms of theequation.
I believe that the experiment was successful as my results wereas I predicted and I met all of my aims and objectives that were set out at thebeginning of this report. I also completed thorough research into thebackground theory of the equation which contributed to my overall understandingof the topic.
