Heat Transfer

441. Water is normally used as a coolant in the heat exchange equipments mainly because of its

1. Abundance & high heat capacity
2. Low density
3. Low viscosity
4. High fluidity

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442. Wavelength corresponding to the maximum energy is inversely proportional to the absolute temperature. This is _________ law.

1. Stefan's
2. Dalton's
3. Wien's
4. Kirchoff’s

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443. What is Nusselt number?

1. CP. μ/k
2. hD/k
3. h. CP/μ
4. C_P. μ/h

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444. What is the absorptivity of a black body?

1. 1
2. 0
3. 0.78
4. 0.95

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445. What is the emissivity of a black body?

1. 0
2. 1
3. 0.5
4. 0.9

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446. What is the geometric mean of two heat transfer areas A1 and A2?

1. √(A₁ . A₂)
2. √(A₁ + A₂)
3. ½ √(A₁ . A₂)
4. 2 √(A₁ . A₂)

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447. What is the logarithmic mean of r₁ and r₂?

1. (r₁ - r₂)/ln(r₁/r₂)
2. (r₁ - r₂)/ln(r₂/r₁)
3. (r₂ - r₁)/ln(r₁/r₂)
4. (r₁ - r₂)/-ln(r₁/r₂)

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448. What is the steam economy in case of a single effect evaporator system?

1. 1
2. > 1
3. < 1
4. 0.1

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449. What is the thermal conductivity of a perfect heat insulator?

1. Zero
2. One
3. ∞
4. Between 0 and ∞

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450. What is the unit of thermal conductivity?

1. Kcal/hr. m² °C
2. Kcal/hr.m.°C
3. Kcal/hr.m
4. Kcal/hr. °C

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