The process in which heat moves from a high-temperature body to a low-temperature body is called heat transfer. As we know, heat is a kinetic energy parameter introduced by the particles in the given system. When the temperature of a system increases then the kinetic energy of particle in the system also increase. The transfer of particle energy from one system to another system through contact of two systems is entirely it.

The following equation shows heat transfer from one system to the other.

Where

Q = Heat supplied to the system
m = mass of the system
c = Specific heat capacity of the system and
ΔT = Change in temperature of the system

The process of transferring heat can take place in three different forms. They are as follows:

Conduction
Convection
Radiation

Conduction:

The amount of heat transferred using conduction can be represented in the following formula,

Q = Conductivity

K = Thermal conductivity

THOT = Hot temperature

TCOLD = Cold Temperature

t = Time

A = Area of the surface

d = Thickness of the material

Convection:

Heat transferred by the process of convection can be given as,

Here, Hc is the heat transfer coefficient.

Radiation:

The Heat transferred by the process of radiation can be given as,

Here σ is known as Stefan Boltzmann Constant.

Derivation:

From the definition of specific heat capacity, we can say that, it is the total amount of heat that is to be supplied to a unit mass of the system, so as to increase its temperature by 1 degree Celsius.

Now, the total heat to be supplied to the system can be given as,

Real-Life Example: Let us take one pitcher of water which needs to be heated up to 100 degrees Celsius from room temperature. In this scenario, when we know the mass of water and its specific heat at the given conditions, using the above formula we can easily get the amount of heat added.

Solved Problem

Example 1: Let us consider two water columns at different temperatures, one being at 40oC and the other being at 20oC. As both the water columns are separated by a glass wall of area 1m by 2m and a thickness of 0.003m. Calculate the amount of heat transfer. (Thermal Conductivity of glass is 1.4 W/mK)

Solution:

According to question,

Thermal Conductivity of glass = 1.4 W/mK.

Also, the temperature of the first column is Th=400 C and

The temperature of the second column is Tc=200 C.

Area of the wall separating both the columns = 1m × 2m = 2 m2

heat transfer equation for conduction,

Example 2: A 5 Kg system was heated from its initial temperature of 30ᵒC to its final temperature of 60ᵒC. Determine the total heat gained by the system. (Specific heat of the system = 0.45 kJ/Kg K)

Solution:

According to question,

The Initial temperature of the system, Ti = 30ᵒC

The Final temperature , Tf = 60ᵒC

The Mass of the system, m = 5 kg

The total heat gained by the system will be calculated with the given formula for heat transfer.

Q = 5×0.45×30

Q = 67.5 J

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