-
-
-
-
Chetankumar Mohane
MemberCheck out the NPTEL video lectures on Thermal Engineering by PK Das. The video lectures are really very good giving out basic knowledge of Thermal Engg.
Here are the links:
Lecture 1 : Introduction & Definition
Lecture 2 : First Law of Thermodynamics (Open System)
Lecture 3 : First Law of Thermodynamics (Closed System)
Lecture 4 : Second Law of Thermodynamics
Lecture 5 : Second Law & carnot Principle
Lecture 6 : Properties of Pure Substances
(Guys do use InI community regularly)
Nov 29, 2011 at 1:57 pm
-
-
-
Inspire N Ignite
ParticipantThanks Chetankumar this really helpful.
Nov 29, 2011 at 2:13 pm
-
-
-
Chetankumar Mohane
Member@I n I : Its my Pleasure…
Dec 02, 2011 at 7:36 am
-
-
-
Ritesh Das
Member@chetan…for a closed system constant volume process work done will “always” be zero!!…is that correct!!!???
Dec 11, 2011 at 3:04 pm
-
-
-
Chetankumar Mohane
Member@Ritesh: Absolutely it is always be zero. Work = Integration of P*dV. Now as Volume is constant it means change in volume is zero i.e. dV is zero, which results in zero work done.
Lets took it in this way. Consider the standard “Piston-Cylinder” example. Whatever u do in the system (either change pressure or Temp.) but its volume is going to be same as it is Constant Volume process. So if u remember the definition of “Work” ; it is Force*Displacement. So it requires “Displacement”
In this process there is no displacement of the piston because it will change the Volume of the cylinder so it will violet our essential requirement of “Constant Volume”. And also as it is “Closed System” no mass can cross the boundary of system so that there is no chance of Work to be done on the mass so it could cross the boundary.
So moral of the story is “For a Closed System Constant Volume process work done will ALWAYS be zero”Dec 12, 2011 at 4:46 pm
-
-
-
Ritesh Das
Memberthanks yaar…that was a good explanation!!!…
Dec 13, 2011 at 9:21 am
-
-
-
Chetankumar Mohane
MemberThanks!!!! I know I am not so good to Explain something but still I tried my best.
Dec 14, 2011 at 3:35 am
-
-
-
Ritesh Das
MemberTdS= dU+pdV…according to pk nag this equation holds good for any process(reversible or irreversible)…but how is that possible??…the term “pdV” is only used for quasi-static process or a reversible process!!!!!
Dec 17, 2011 at 12:30 pm
-
-
-
Chetankumar Mohane
Member@Ritesh, Can you please give the full sentence exactly given by PK Nag in the book.
Also give in what concern this equation comes in the book?
I am waiting for your reply…Dec 18, 2011 at 11:37 am
-
-
-
Ganesh V Iyer
Member@all,i am finding convection part of heat transfer difficult bcos of various formulae for various conditions.Any suggestions??
Dec 19, 2011 at 4:03 pm
-
-
-
Ritesh Das
Member@chetan…its from PK nag(4th edition)…page number 180…chapter name-entropy..sub-topic-“first law and second law combined”..
Dec 19, 2011 at 5:30 pm
-
-
-
Chetankumar Mohane
Member@Ganesh, Yes I agree, Heat Transfer is difficult subject. Up to conduction it is quite easy but after that is becomes more difficult because of very long & complex formulas & conditions as you said.
But we have to remember those formulas exactly; we dont have any choice for this 🙁
Only thing we can do is write those formulas in systematic way & try to remember them.
Also if you solve many problems on it you are getting used to remembering those formulas.
All the best..Dec 20, 2011 at 1:29 pm
-
-
-
Ganesh V Iyer
Member@chetan,thanx a lot.
Dec 20, 2011 at 1:58 pm
-
-
-
Chetankumar Mohane
Member@Ritesh,
According to PK Nag,
“TdS= dU+pdV this equation can be applied in all the processes undergone by closed system” is true provided that there is no other forms of major energies (like KE, PE, viscuos, Electical) involved in the process.
You will get the answer after you can understands how actually this equation comes.
The original equation is,
dQ-dW=dE …………1 … (from First law of thermodynamics)
where dQ=small change in heat
dW=small change in work
dE=small change in total energy
now, dE=dU+dKE+dPE+dE+…..
where, dU,dKE,dPE,dE are small change in internal energy, K.E., P.E., Electrical energy resp.
we no for many processes we can neglect dKE,dPE&dE & other minor energies.
Also we know dS=dQ/T
& dW=pdV…. this is the work done on the system or by the system
so equ 1 becomes,
TdS= dU+pdVSo the term “pdV” represents the work done on the system or by the system & it have no mean whether the process is reversible or irreversible.
Hope you understands it. 🙂
Dec 20, 2011 at 2:12 pm
-
-
-
Rahul Ranjan
Member@RITESH you should go for lectures by PROF. S.K.SOM(basic thermodynamics) for clearification of doubts like one u have asked
Dec 20, 2011 at 6:14 pm
-
-
-
Ritesh Das
Memberthank you chetan for ur reply…and sorry for being late…actually i read pk nag again…cleared my doubt…only for reversible process we integrtae the term pdv and get p(v2-v1)…whereas for irreversible process we cant do the same…but we can use the term pdv for both the processes…and yeah nptel videos of prof. s k som were very helpful too..:)
Jan 02, 2012 at 4:20 pm
-
-
-
Chetankumar Mohane
Member@Ritesh, there are many more very good NPTEL videos to clear our concepts but unfortunately as now we don’t have that much time. May be after exam we could watch them!!!
Jan 05, 2012 at 12:47 pm
-
-
-
tell steve
ParticipantOct 22, 2024 at 1:46 pm
-
-
You must be logged in to reply to this topic.
Ask any difficulties about Heat Transfer, Thermodynamics, Fluid Mechanics & Applications here.. Let help others & get helped from others also. What do you think?