Heat is a transfer of energy between objects due to a temperature difference, and always flows from higher to lower temperature. Heat transfer occurs through conduction within an object, convection by moving fluids, or radiation via electromagnetic waves. The rate of heat transfer between objects is determined by the science of heat transfer.

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2. • Heat is a transfer of energy from one object to another due to a
difference in temperature.
• Temperature is a measure of the molecular energy in an object
• Heat always flows from an object of higher temp (TH) to one of lower
temp (TL)
• We are often interested in the rate at which this heat transfer takes
place
• The science that deals with the determination of rates transfer of
heat energy is known as HEAT TRANSFER.
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3. Conduction
• Transfer of Heat from one part of substance to another part of
same substance without appreciable motion of molecules
Convection
• The process of heat convection is due to capacity of moving
matter to carry heat energy
Radiation
• Radiation is the transfer of heat by means of electromagnetic
waves. To radiate means to send out or spread from a central
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6. Net heat Flow into element per unit time in respective
directions
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7. Net heat Flow into element from all directions by conduction in certain time δt will be,
Net heat storage in the element in certain time δt will be,
Net heat Flow into element from all directions + Heat generated within element
=Energy Stored in the
element
According to Energy Balance Equation
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18. for a cylindrical layer
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for a spherical layer

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