Physics, 30.08.2019 19:30 memester74

Aturbine blade 6.3 cm long with cross sectional area 4.6x10-4 m2 and perimeter 0.12 m is made of stainless steel (k=18 w/mk). the temperature of the root is 482oc. the blade is exposed to a hot gas flow at 871oc with a heat transfer coefficient 454 w/m2k. determine the temperature of the blade tip and the rate of heat transfer at the root of the blade. tip could be assumed to be insulated.

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Answer from: FutureDB

There are two equations to be used for this problem. The firs one is the general formula for heat transfer:

Q = kAΔT
where
Q is the rate of heat transfer
k is the heat transfer coefficient
A is the cross-sectional area
ΔT is the temperature difference

Substituting the values:
Q = (454 W/m²·K)(4.6x10⁻⁴ m²)(871°C - 482°C)
Q = 81.24 W

Thus, the rate of heat transfer is 81.24 W.

We use the Q for the second equation. The radial heat transfer would be:

Q = 2πkL(T₁ - T₂)/ ln (r₂/r₁)
where
L is the length of the turbine
r₂ is the distance of tip blade to the center
r₁ is the distance of root blade to the center
T₂ is temperature at the tip blade
T₁ is temperature at the root blade

Perimeter = 2πr₂
0.12 m = 2πr₂
r₂ = 0.019 m

Cross-sectional area = πr₁²
4.6x10⁻⁴ m² = πr₁²
r₁ = 0.012 m

Substituting to the equation:

81.24 W = 2π(454 W/m²·K)(6.3 cm * 1m/100 cm)(482°C - T₂)/ln (0.019 m/0.012 m)

Solving for T₂,
T₂ = 481.79°C

Answer from: Quest

freezing

deposition

condensation

explanation;

melting also called fusion is the process where solid becomes liquid, sublimation is the process where solid becomes gaseous without first changing to liquid, deposition involves change from gaseous to solid state, freezing involves change from liquid to solid, boiling or evaporation involves change of liquid to gaseous state, while condensation is the change from gaseous state to liquid state.

endothermic reactions involves absorption of heat from the surroundings or the environment while exothermic reactions involves loss of heat energy to the surroundings.

in this case, sublimation, evaporation and melting are endothermic reactions (gain energy from the environment) while, freezing, deposition and condensation are exothermic (loss of energy to the surroundings) reactions.

Answer from: Quest

which piece of furniture will have the most inertia and give the furniture movers the most difficulty in moving?

answer

a 75kg dining table

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