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The image above represents energy transfer by radiation.

To compute for energy transfer by radiation, three essential parameters are needed and these parameters are Emissivity (ε₁), Absorbivity (α₁) and Emissive Power of Black Body (e_b).

The formula for calculating energy transfer by radiation:

q_net = e_b(ε₁ – α₁)

Where:

q_net = Energy Transfer by Radiation
ε₁ = Emissivity
α₁ = Absorbivity
e_b = Emissive Power of Black Body

Let’s solve an example;
Find the energy transfer by radiation when the emissivity is 30, the absorbivity is 10 and the emissive power of black body is 4.

This implies that;

ε₁ = Emissivity = 30
α₁ = Absorbivity = 10
e_b = Emissive Power of Black Body = 4

q_net = e_b(ε₁ – α₁)
q_net = 4(30 – 10)
q_net = 4(20)
q_net = 80

Therefore, the energy transfer by radiation is 80 J.

Calculating the Emissivity when the Energy Transfer by Radiation, the Aborbivity and the Emissive Power of Black Body is Given.

ε₁ = (^q_net / _eb) + α₁

Where:

ε₁ = Emissivity
q_net = Energy Transfer by Radiation
α₁ = Absorbivity
e_b = Emissive Power of Black Body

Let’s solve an example;
Find the emissivity when the energy transfer by radiation is 28, the absorbivity is 3 and the emissive power of black body is 7.

This implies that;

q_net = Energy Transfer by Radiation = 28
α₁ = Absorbivity = 3
e_b = Emissive Power of Black Body = 7

ε₁ = (^q_net / _eb) + α₁
ε₁ = (²⁸ / ₇) + 3
ε₁ = 4 + 3
ε₁ = 7

Therefore, the emissivity is 7

Calculating the Aborbivity when the Energy Transfer by Radiation, the Emissivity and Emissive Power of Black Body is Given.

α₁ = ε₁ – (^q_net / _eb)

Where:

α₁ = Absorbivity
q_net = Energy Transfer by Radiation
ε₁ = Emissivity
e_b = Emissive Power of Black Body

Let’s solve an example;
Find the absorbivity when the energy transfer by radiation is 8, the emissivity is 18 and the emissive power of black body is 4.

This implies that;

q_net = Energy Transfer by Radiation = 8
ε₁ = Emissivity = 18
e_b = Emissive Power of Black Body = 4

α₁ = ε₁ – (^q_net / _eb)
α₁ = 18 – (⁸ / ₄)
α₁ = 18 – 2
α₁ = 16

Therefore, the absorbivity is 16.

Calculating the Emissive Power of Black Body when the Energy Transfer by Radiation, the Emissivity and Absorbivity is Given.

e_b = ^q_net / _{ε1 – α1}

Where:

e_b = Emissive Power of Black Body
q_net = Energy Transfer by Radiation
ε₁ = Emissivity
α₁ = Absorbivity

Let’s solve an example;
Find the emissive power of black body when the energy transfer by radiation is 50, the emissivity is 15 and the absorbivity is 10.

This implies that;

q_net = Energy Transfer by Radiation = 50
ε₁ = Emissivity = 15
α₁ = Absorbivity = 10

e_b = ^q_net / _{ε1 – α1}
e_b = ⁵⁰ / _{15 – 10}
e_b = ⁵⁰ / ₅
e_b = 10

Therefore, the emissive power of black body is 10.

Nickzom Calculator – The Calculator Encyclopedia is capable of calculating the energy transfer by radiation.

Now, Click on Radiation Heat Transfer under Materials and Metallurgical

Now, Click on Energy Transfer by Radiation under Radiation Heat Transfer

The screenshot below displays the page or activity to enter your values, to get the answer for the energy transfer by radiation according to the respective parameter which is the Emissivity (ε₁), Absorbivity (α₁) and Emissive Power of Black Body (e_b).

Now, enter the values appropriately and accordingly for the parameters as required by the Emissivity (ε₁) is 30, Absorbivity (α₁) is 10 and Emissive Power of Black Body (e_b) is 4.

Finally, Click on Calculate

As you can see from the screenshot above, Nickzom Calculator– The Calculator Encyclopedia solves for the energy transfer by radiation and presents the formula, workings and steps too.