Heat Transfer

191. In a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will

1. Increase
2. Decrease
3. Remain unchanged
4. Either increase or decrease; depends on the coolant flow rate

192. In a cooling tower, water becomes cool by

1. Loosing sensible heat
2. Heat transfer to surroundings
3. Vaporisation due to heat loss to air
4. Loosing latent heat

193. In a forward feed multiple effect evaporator unit

1. Viscosity of liquid is highest in first effect
2. Transfer from effect to effect is done by pumps
3. No pump is required to withdraw the product from the last effect
4. None of these

194. In a forward feed multiple effect evaporator, the pressure is

1. Highest in last effect
2. Lowest in last effect
3. Same in all effects
4. Dependent on the number of effects

195. In a forward feed multiple effect, the pressure build up will be

1. Least at the inlet of the first effect
2. Least at the outlet of the last effect
3. Highest at the inlet of the last effect
4. Highest at the outlet of the last effect

196. In a gas-liquid shell and tube heat exchanger, the

1. Presence of a non-condensable gas decreases the condensing film co-efficient
2. Gases under high pressure are routed through the tube side, because high pressure gases are corrosive in nature
3. Gases to be heated/cooled is normally routed through the shell side, because the corrosion caused by the cooling water or steam condensate remain localised to the tubes
4. All 'a', 'b' & 'c'

197. In a heat exchanger with steam outside the tubes, a liquid gets heated to 45°C, when its flow velocity in the tubes is 2 m/s. If the flow velocity is reduced to 1 m/s, other things remaining the same, the temperature of the exit liquid will be

1. Less than 45°C
2. More than 45°C
3. Equal to 45°C
4. Initially decreases and remains constant thereafter

198. In a heat exchanger, floating head is provided to

1. Facilitate cleaning of the exchanger
2. Increase the heat transfer area
3. Relieve stresses caused by thermal expansion
4. Increase log mean temperature gradient

199. In a heat exchanger, one transfer unit means

1. A section of the exchanger in which change in temperature of one stream equals the average driving force in the section
2. The size of the exchanger in which heat transfer rate is 1 kcal/hr
3. Both (A) and (B)
4. None of these

200. In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid

1. Varies directly as the area and the LMTD
2. Directly proportional to LMTD and inversely proportional to the area
3. Varies as square of the area
4. None of these