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Flashcards in Conduction Deck (16):
1

Types of conduction

1) steady state conduction
2) unsteady state conduction

2

Steady state conduction

No accumulation of heat

Q constant throughout

3

Unsteady conduction

Heat gets accumulated

Heat generation and heat consumption

Parabolic type of profiles

4

Thermal conductivity

Independent of temperature gradient except porous solids where radiation can affect

Dependent on temperature

Usually an average k value from both the temperatures are used

5

Thermal conductivity of metals

Decreases with increase in temperature since the mean free path for the free electrons to move reduces because of particle vibration

Decreases with impurities example alloys have less conductivity than pure metals

6

Thermal conductivity of liquids

Decreases with temperature except water which reaches a maximum

7

Thermal conductivity of gases

Incresases with increase in temperature

Proportional to square of T for mono atomic gases

Decreases with increase in molecular weight

8

Resistance

Length/ conductivity * area

K/W

Conductance

9

Log mean area of cylinder

Log mean radius of cylinder

Geometric mean area of sphere

Geometric mean radius of sphere

10

Unsteady state Heat conduction

Heat generation

Heat consumption

11

Dimensional number associated with unsteady state heat transfer

Biot number

Fourier number

12

Biot number

Conductive resistance of solid/ convective resistance of fluid

hL/k

13

Bi < 0.1

Lumped system

14

Bi > 0.1

Distributed system

15

Fourier number

Conduction rate/ storage rate

16

Unsteady state conduction type

Heat transfer with constant surface temperature

Heat transfer with non uniform surface temperature