Available Energy (Exergy) Calculation
I am stuck in between a problem. Part of where I am doubtful is as follows.
400KJ of energy is transferred from a source at 1000K to a 2 kg gas contained in an enclosed vessel. The gas temperature is 350K and atmospheric temperature is 300K. What is the available energy of gas?
The solution is-
1. Calculate change in entropy of gas (ds).
2. From that calculate unavailable energy= 300*ds.
3. available energy= 400-300*ds.
But what I think is- available energy= Energy of gas at 350K+400-300*ds.
where 300=atmospheric temperature.
#-Link-Snipped-# sir can you help?
400KJ of energy is transferred from a source at 1000K to a 2 kg gas contained in an enclosed vessel. The gas temperature is 350K and atmospheric temperature is 300K. What is the available energy of gas?
The solution is-
1. Calculate change in entropy of gas (ds).
2. From that calculate unavailable energy= 300*ds.
3. available energy= 400-300*ds.
But what I think is- available energy= Energy of gas at 350K+400-300*ds.
where 300=atmospheric temperature.
#-Link-Snipped-# sir can you help?
Replies
-
Ramani AswathSince the gas is already at 350 degK, it already has some available energy = 2 x (350-300) x sp.Ht.
You have added another 400kJ.
Add this to the above, which should give you the total available energy.
Have I missed something here? -
ISHAN TOPRE
Yeah, this is what I think too, but the text says do not consider energy of system i.e., (350-300)*sp heat. Calculate from 400KJ.bioramaniSince the gas is already at 350 degK, it already has some available energy = 2 x (350-300) x sp.Ht.
You have added another 400kJ.
Add this to the above, which should give you the total available energy.
Have I missed something here?
Will check once again and clear the confusion. -
Ramani Aswath
Usually available energy refers to the energy available above the ambient temperature, since this can be harvested. If this is correct then mCpdelT cannot be ignored.IssueYeah, this is what I think too, but the text says do not consider energy of system i.e., (350-300)*sp heat. Calculate from 400KJ. Will check once again and clear the confusion.
You are reading an archived discussion.
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