Heat Transfer

241. In SI units, fouling factor is expressed in

1. m²°K/W
2. W/m²°K
3. m²°K
4. m°K/W

242. In SI units, thermal conductivity is expressed in

1. Watt/m.°K
2. Watt/m². °K
3. Watt/m². °K
4. Watt/m4. °K

243. In sub-cooled boiling,

1. Temperature of the heating surface is less than the boiling point of the liquid
2. Temperature of the heating surface is more than the boiling point of the liquid
3. Bubbles from heating surface are absorbed by the mass of the liquid
4. Very large vapour space is necessary

244. In the equation Q = UAΔt; Δt is

1. Geometric mean temperature difference
2. Arithmetic mean temperature difference
3. Logarithmic mean temperature difference
4. The difference of average bulk temperatures of hot and cold fluids

245. In the free convection regime of pool boiling, the heat flux is proportional to

1. Δt_1/2
2. Δt₂
3. Δt^5/4
4. Δt

246. In thermal radiation for a black body (where, ε is emissivity and α is absorptivity)

1. α = 1; ε ≠ 1
2. α ≠ 1, ε = 1
3. α ≠ 1, ε ≠ 1
4. α = 1; ε = 1

247. In which mode of heat transfer, the Biot number is important?

1. Transient heat conduction
2. Natural convection
3. Forced convection
4. Radiation

248. Increasing the liquor level in the evaporator results in the

1. Decreased capacity
2. Increase in liquor film co-efficient
3. Decreased effect of hydrostatic head
4. Increased true temperature drop

249. Indirect contact heat exchangers are preferred over direct contact heat exchangers, because

1. Heat transfer co-efficient are high
2. There is no risk of contamination
3. There is no mist formation
4. Cost of equipment is lower

250. Intermittent tube cleaning is possible to be done in case of a _________ evaporator.

1. Basket type
2. Horizontal tube
3. Calandria
4. None of these