A nuclear reactor with its core constructed of parallel vertical plate...
Calculating Maximum Heat Dissipation from a Nuclear Reactor
Given parameters:
- Height of the vertical plates = 2.25 m
- Width of the vertical plates = 1.5 m
- Maximum surface temperature of the plate = 975°C
- Lowest allowable temperature of bismuth = 325°C
- Correlation for convection coefficient = Nu = 0.13 (Gr Pr)1/3
To estimate the maximum possible heat dissipation from both sides of each plate, we need to follow the below steps:
1. Calculate the average temperature of the plate:
The average temperature of the plate can be calculated using the formula:
Avg. Temperature = (Max. Temperature + Min. Temperature) / 2
= (975°C + 325°C) / 2
= 650°C
2. Calculate the Grashof number:
The Grashof number can be calculated using the formula:
Gr = gβΔT L3 / ν2
where g = acceleration due to gravity = 9.81 m/s2
β = coefficient of thermal expansion of bismuth = 1.24 x 10-4 K-1
ΔT = temperature difference = 650°C - 325°C = 325°C
L = height of the vertical plate = 2.25 m
ν = kinematic viscosity of bismuth = 2.9 x 10-7 m2/s
Substituting the values in the formula, we get:
Gr = 9.81 x 1.24 x 10-4 x 325 x (2.25)3 / (2.9 x 10-7)2
= 1.53 x 1013
3. Calculate the Prandtl number:
The Prandtl number can be calculated using the formula:
Pr = ν / α
where α = thermal diffusivity of bismuth = 1.22 x 10-5 m2/s
Substituting the values in the formula, we get:
Pr = 2.9 x 10-7 / 1.22 x 10-5
= 0.0238
4. Calculate the Nusselt number:
The Nusselt number can be calculated using the correlation given:
Nu = 0.13 (Gr Pr)1/3
Substituting the values in the correlation, we get:
Nu = 0.13 (1.53 x 1013 x 0.0238)1/3
= 1,082.8
5. Calculate the heat transfer coefficient:
The heat transfer coefficient can be calculated using the formula:
h = k Nu / L
where k = thermal conductivity of bismuth = 15.8 W/mK
Substituting the values in the formula, we get:
h = 15.8 x 1,082.8 / 2.25
= 7,593.2 W/m2K
6. Calculate the maximum heat dissipation:
The maximum heat dissipation can be calculated using the formula:
Qmax = h A (Max. Temperature - Avg. Temperature)
where A = surface area of the plate = height x width = 2.25 x 1.5 = 3.375 m2
Substituting the values in the formula, we get:
Qmax