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# Strategically Preparing Heat Transfer for GATE Mechanical Engineering

Sangam Gupta will share the right way to prepare Heat Transfer for GATE Mechanical. Sangam secured AIR 199 in GATE 2017 (ME) and is currently working in IOCL.

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In this blog, I will be telling all the Mechanical branch students how to prepare Heat Transfer subject for GATE. As all the mechanical branch aspirants will be aware that Heat Transfer is one of the most important subject for mechanical branch. It is one of the core subjects and the concepts should be clear to prepare for other subjects as well.

So, now question comes that how do you prepare it? How much time to dedicate? What books to use? Which notes to be used? How and how much to practice? And few other questions. I will be answering all these.

Stats from last year GATE papers: –

 Year 2017 2016 2015 2014 2013 2012 2011 2010 Heat Transfer 3.5 7 8 7 11 11 8 4

The above table shows the marks distribution for GATE paper. It can be seen that the range of marks for this subject varies from 4 to 11, average being 7.5 which is 7.5% of total marks. Obviously, the marks distribution also shows, it is one of the most important subject who’s question are mostly easy and you can score 100% in HT

Now let us see how to do the preparation

Books required for Heat Transfer preparation: –

Heat and Mass Transfer: Fundamentals and Applications – by Cengel & Boles

Heat and Mass Transfer- P K Nag

Notes – KRASH (ME), postal study course

Time required for Heat Transfer preparation: –

4 to 7 days (if you have 4 to 5 months of preparation) with 4 to 6 hours daily

Topics: –

• Modes of heat transfer
1. Conduction
1. One dimensional heat conduction
1. Plane slab*
3. Spherical
2. Resistance concept and electrical analogy*
3. Critical thickness*
4. Heat transfer through fins
5. Unsteady heat conduction*
6. Lumped parameter system & Heisler’s charts
2. Convection
1. Difference between Free and forced convection
2. Thermal boundary layer
3. Dimensionless parameters in free and forced convective heat transfer
4. Heat transfer correlations for flow over flat plates and through pipes with and without effect of turbulence.
1. Radiative heat transfer
2. Stefan Boltzmann law
3. Wien’s displacement law
4. black and grey surfaces*
5. View factors* (atleast 1 question is compulsory)
6. Radiation network analysis*.
4. Heat Exchangers*
1. Heat exchanger performance
2. LMTD and NTU methods

The topics marked with * are more important and you have to solve more numericals in these topics.

How to start with Heat Transfer preparations –

Make sure that you have P K Nag as it will help with theory as well as numericals. Keep the notes with you as well. I would suggest keeping an extra note book which you should keep for preparing notes, different kind of notes, where you note down anything which you understand in concepts and formulae. Also keep one separate notebook for solving numericals. I would advise you to solve full length numericals. If you keep full length numericals solved in a notebook that will help you later on while revising. Cengel is a book of advance stage at least try its examples numericals, after doing a fair amount of numericals from Nag. Wherever you get confused in theory, refer the Cengel.

Now I will be telling topic wise how to prepare.

1. Basic concepts (1 day) You will find it in starting chapters of P K Nag. The theory part is necessary for going further ahead with the preparations. Focus only on theory. Solve 5 to 10 solved numericals from P K Nag. That much will be enough. Here you will understand what the difference between HT (heat transfer) and Thermo (Thermodynamics).
2. Conduction This topic starts with Fourier law of conduction and it leads to thermal conductivity and you have to study how it reacts with change in different parameters like Temperature, pressure alloying etc.
3. Convection This topic tells you how the heat moves in fluids, understand the term Diffusion, Free & Forced convection. Give a time to Hydrodynamic Boundary layer & comprehend the uses of various Dimensionless numbers in Free & Forced convection. Learn to use the empirical relations for flow over flat plates and through pipes and these are affected by turbulence. Don’t forget the way how they are derived.
4. Radiation This mode shows its complete significance in high temperatures. Here we have to understand all the terms used in this mode. What are Stefan Boltzmann law, Kirchhoff’s Law and Wien’s displacement law. While studying network analysis be clear about Shape and Surface Resistance, and what is the effect of radiation Shield. Be clear about BLACK, WHITE & GREY BODIES with their characteristics.
5. Heat exchangers It is the machine where all modes are prominent (radiation excluded in our syllabi). There are two approaches to solve its problem for both Counter flow & Parallel flow, i.e. LMTD and NTU. Comprehend where and when to use LMTD and NTU. And how to find the effectiveness.
6. Important Points:
1. HT is the subject of mostly numericals, Do as much you can.
2. Notes are necessary to understand the concept. Normally on your first time preparation of subject, refer both notes and book for theory part. Move to NPTEL by P K Nag only if you have doubt. While revising, only refer the notes and the separate notebook which you have prepared.
3. Once you are done with the subject, solve last 15 year papers. IF you are able to solve 75% or more numericals, you are in right track.
4. You have to remember all the formulas. So, in your separate notebook, keep all the formulas ready and refer them for 10 to 15 minutes every night before sleeping so that you don’t forget them.
5. Do not spend more than 15 days for the whole subject.
6. Give mock tests as soon as you are done with the topic/subject.

If you do this much, it will be more than sufficient for preparation of FM.

Good luck!