introduction_to_heat_transfer.pdf

7/27/2019 INTRODUCTION_TO_HEAT_TRANSFER.pdf

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TRANSPORT PROCESS CLD 20402MDM AIZA SYUHANIZ SALLEH

LEC ROOM 3

EXT: 2023EMAIL: [email protected]


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1.01.0 IntroductionIntroduction toto HHeateat TransferTransfer

Application o

f Heat Transfer inIndustry


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What is HE@T?Heat transfer (or heat)

Heat is the form of energy that can be transferred from one system to another as a result of temperature difference.The science that deals with the determination of therates of energy transfers is heat transfer. Whenever there exists a temperature difference in a medium or between media, heat transfer must occur.The larger the temperature gradient, the higher the

rate of heat transfer.


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Heat (energy) always move from war

mer substance to cooler substance

HOT COLDHeat will continue to move until both substances are the same temperature.

HOT

HOT


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To study the rate of he

at being transferred

or

How long the process takes place to transfer such

amount of heat from one e

q. state to another as a res

ult of temperature differen

ce.

WhyWhy toto ststudyudyheatheat trantransfer?sfer?


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Differences between..

Thermodynamics

Only an amount of energy(heat)

Makes no referencesto how long the process will take

Deals with systems i

n equilibrium

Heat Transfer

Rate of heat transfer The times of cooling

& heating


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Applicationsof Heat Transfer


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Heat Transfer Equipments

Heat Exchanger Boiler Condenser Radiator Heater Furnace Solar collectors


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Engineeringin Heat TransferHT can be studied experimentallyor analytically

Experiment

actual physical system but expensive, time consuming, impractical

Analytical numerical approach, fast & inexpensive, results sub

ject to accuracy of the assumption


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Heat

Total energy,E - sum of all energies Internal Energy,u - energy at molecular str

ucture

Sensible heat - internal energy of a systemassociated with kinetic energy of molecules

Latent heat - internal energy associated wit

h phase of the system

= >T and heat???


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Specific heats of liquids, gases and solids Specific heat

- The energy required toraise the temperature

of a unit mass of a subs

tance by 1 degree


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Specific heat: Cv and Cp

Cv- The energy required to raise the temperature of a unit mass of a substance by 1 degree as the volume is held constant

Cp- The energy required to raise the temperature of a unit mas

s of a substance by 1 degree as the pressure is held constant

Normally : Cp > CvIdeal Gas : Cp = Cv + R

Incompressible susbtanceS (solid & liquid): Cp Cv C


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Energy transfer

2 ways: Heat, Q and Work, W Q an energy is heat transfer if the driving f

orce is temperature

- heat transfer rate (per unit time. J/s) W- energy other than above; rotating shafts,

moving piston


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Modes of heat transfer


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EXAMPLES.

Touch the black car in the summer and the heat from the car transfers into your hand.

A breeze makes you fe

el cooler because the wind transfers heat awayfrom your body.


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Industrial Applications

Food Tech

HeatTransfer

Application

Chemical

Tech

Bio Tech

EnvironmentTech

PolymerTech


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Chemical technology

Distillation


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Heat exchanger


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Furnace


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Biological technology

Autoclave


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Bioreactor


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Incinerator

Environment


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Cooling tower


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Food Technology

Refrigerator

Microwave


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Polymer technology

Injection Moulding Extrusion


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HEAT & WEATHER

THE END..

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