Heat Transfer Exam Question

[alexdouglas1969]

Exam question:

Heat transfer takes place whenever there is a:

a Pressure difference
b Temperature difference
c Specific heat difference
d Latent heat difference


Any thoughts on this question would be very welcome, thanks.
Thanks
:)

[Brian_UK]

The answer has to be 'B' surely.

It doesn't matter what the type of heat is it's the fact that there is a difference that makes the transfer occur.

[alexdouglas1969]

Well our tutor would agree with you but thinking of the psychrometric chart - I would say 'C' is more correct - after all, temperature is not heat...

Anyone else got an opinion?

[Brian_UK]

OK, I'll pose this question...

How do you quantify the difference between two items of different latent heat?

(Latent Heat is defined as the heat (http://www.taftan.com/thermodynamics/HEAT.HTM) which flows to or from a material without a change to temperature. The heat will only change the structure or phase of the material. e.g. melting or boiling of pure materials)

(The amount of heat transferred delta Q is proportional to the temperature difference delta T between the objects and the heat capacity c of the object.)

[Pooh]

The answer is "B" as you need a Delta T for either specific heat or latent heat to be absorbed or given up.

So I agree with Brian on this one, without this principle which is the second Law of Thermodynamics we all would be out of a job.

Ian

[alexdouglas1969]

Have given this some more thought now - obviously not C as specific heat is amount of energy per unit mass to raise by one degree (or temperature unit) so C just does not make sense - I agree B is correct. Thanks for the help, I was stuck on the definition of temperature - for example the same level of heat can be given by different temperature scales, therefore a difference in temperature does not necessarily cause flow of energy... what a muddle... thanks... !!!11

[frank]

The temperature scale (Fahrenheit, Celcius, Rankine, Kelvin) is a MEASURE of temperature (heat energy) from a base point, whereas Specific heat or Latent heat are a measure of heat carrying capacity.

Pressure has nothing to do with temperature in this instance.

[Pooh]

Frank
specific heat is a measure of heat carrying capacity whereas latent heat is the amount of heat required to change phase so not really heat carrying potential, or am I being a tad pedantic.

Ian

[frank]

Hi Ian

Nit Picking, hmm, maybe. Seems we've covered it now though :D

You know what I was trying to say ;)

[SURESH YADAV]

Heat tranfer depends only where, there is difference in temprature.......

[Gary]

There is no transfer if there is no temperature difference.

The answer is B.