Heat Transfer

Question 1

What is the formulaic representation of heat current?

Answer 1

Heat Current is given by:

ΔQ/ΔT= K A(T1-T2)/x ; K is thermal conductivity of the material

Question 2

What is the conceptual form of Thermal Resistance?

Answer 2

The quantity x/KA is called Thermal Resistance R

Question 3

What is the formulaic representation of Emissive Power according to Kirchoff/s Law?

Answer 3

Emmisive Power is given by:
E= ΔU / (ΔA) (Δω) (Δt) ;
ΔA is area
Δt is time
Δω is solid angle
ΔU is energy radiated

Question 4

What is the conceptual form of Absorptive Power?

Answer 4

Absorptive Power α = Energy absorbed/ Energy incident

Question 5

What is the conceptual form of Wien’s Displacement Law?

Answer 5

Wien’s Displacement Law is given by:
λm T= b
; b= Wien Constant, Its value is 0.288 cmK

Question 6

What is the formulaic representation of Stephan Boltzmann Law?

Answer 6

Stephan Boltzmann Law is given by:
u= σAT^4
; T is its temperature
σ= Stephan Boltzmann Constant

Question 7

What is the formulaic representation of net loss of thermal energy per unit time according to Stephan Boltzmann Law?

Answer 7

Δu = eσA(T^4 - T°^4)

Question 8

What is the conceptual definition of Newton’s Law of cooling?

Answer 8

According to Newton’s Law of Cooling, the rate of cooling of the body is directly proportional to the temperature difference and surface area to the temperature exposed?

Question 9

What is the fomulaic representation of Newton’s Law of Cooling?

Answer 9

Newtons Law of Cooling is given by:
dT/dt = -bA(T-T°)
; A is surface Area
T is absolute temperature
b is constant 
T° is surrounding temperature