Answered: What four processes are involved in…

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.78P: What are the important modes of heat transfer for a person sitting quietly in a room? What if the...

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What four processes are involved in heat transfer?

Expert Solution

Step 1 Conduction & convection mode of heat transfer.

Generally, there are 4 modes of heat transfer:-

Conduction
Convection
Radiation
Evaporation

Conduction:-

It is a transfer of energy from more energetic particle of a substance to the adjacent less energetic ones as a result of interaction between particles. For example, heat generated inside an enclosure is transferred to the outer surface by means of conduction.
It can take place in solid/liquid/gas.
Rate of conduction is given by Fourier's law:-

$q_{c o n d .} = - K A (\frac{d T}{d x}) w h e r e, K = t h e r m a l c o n d u c t i v i t y o f t h e m a t e r i a l i n W / m - K A = N o r m a l a r e a a c r o s s h e a t t r a n s f e r d i r e c t i o n$

Convection:-

Convection is a mode of heat transfer that involves the combined effect of conduction & advection(it is a bulk flow of molecules). There are basically two types of convection i.e., Natural convection & forced convection.
Rate law of convection is governed by Newton's law of cooling:-

$q = h A (T_{s} - T_{\infty}) w h e r e, h = c o n v e c t i v e h e a t t r a n s f e r c o e f f i c i e n t i n W / m^{2} - K A = s u r f a c e a r e a o f t h e p l a t e / o b j e c t T_{s} = t e m p e r a t u r e o f s u r f a c e i n K T_{\infty} = s u r r o u n d i n g t e m p e r a t u r e i n K$

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