Exam help regarding heat exchanger, forced convection questions

[Hammad]

hello,

im in bachelors mechanical engineering programme and my thermodynamics papers are in few days

one question is related to heat exchangers or forced convection, but our professor has hinted that in the exam the question regarding heat exchanger, forced convection will be a case study of a power cycle where a heat exchanger will be attached to it, forced convection will be part of it. issue is we have been taught powercycles and heat exchangers/forced convection independently and we have not done any questions on powercycles and heat exchangers/forced convection together.

mainly we have done shell tube heat exchangers using both LMTD and NTU methods and not other heat exchangers like regenerator, power collectors, cooling towers etc.In forced convection, we have simply used reynold's analogy, mcadams equaion, prandtl, nusselt, reynolds number to calculate the rate of heat transfer.

our professor has told us that we won't have to calculate enthalpies, entropies but the question will be mainly about input and output for the heat exchanger (i think he is talking about Qin and Qout). he says that it will be case study about a power cycle where they will zoom into heat exchanger.

i have asked our professor to give us any example, so that we can have some idea regarding the data given, the questions asked and how the calculations for heat exchanger and power cycle can be relatable, but so far he has not given us anything.

so can you guys help me understand how to relate the powercycles and heat exchangers and any example to show what questions can be asked and what things to know to answer the questions.

an example question i found from internet is this one:

i also don't know if there will be one or more than one heat exchanger.

 

[Chestermiller]

Well, for power cycles, you are going to be talking condensers and boilers. So, in your heat transfer book, look for problems involving these.

 

[andrewtirtawijaya]

Well, from my opinion you will ask to design a heat exchanger that will give some output of fluid heat regarding to the fluid input from the power cycle

 

[Hammad]

Well, from my opinion you will ask to design a heat exchanger that will give some output of fluid heat regarding to the fluid input from the power cycle

can you please give any example or elaborate on possible question which will give input values of power cycle and output values for heat exchanger?

i have a design question related to heat exchanger but there is no power cycle involved here is the question

the solution of this question is very scary to say the least. The above user stats that it will be about boiler and condenser, i don't know which one to prepare.

 

[Chestermiller]

can you please give any example or elaborate on possible question which will give input values of power cycle and output values for heat exchanger?

i have a design question related to heat exchanger but there is no power cycle involved here is the question

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the solution of this question is very scary to say the least. The above user stats that it will be about boiler and condenser, i don't know which one to prepare.

Let's see you solve this problem. What have you done so far?

 

[Hammad]

Let's see you solve this problem. What have you done so far?

i already have the solution, but such a lengthy qoestion won't come i guess.

 

[Chestermiller]

i already have the solution, but such a lengthy qoestion won't come i guess.

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This looks pretty good. Is this your solution, or is it a solution that was provided for you. Could you do it yourself? If so, then you should have no difficulties with an exam problem.

If the exam problem involves a condenser in a power cycle, then the working fluid is going to be condensing (pretty much at constant temperature). So the problem will involve heat transfer coefficients from condensing vapors (i.e., high heat transfer coefficients). If the problem involves a boiler, then there will be a hot gas passing through the tubes of the heat exchanger, and a boiling liquid outside the tubes. The tubes will be bare, and not in a shell.

 

[Hammad]

hello guys,

i just want to thank chestermiller and andrewtirtawijaya, for your input, you were correct that there would be design question, although i left the question on choice, but i appreciate the help i got.

This forum is a very nice forum and i have got spot on help for all the issues i have tried to address.

thanks again