Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean surface). (A) U1 - U2 (B) 1/U1 - 1/U2 (C) 1/U2 - 1/U1 (D) U2 - U1

Fouling factor for a heat exchanger is given by (where, U1 = heat
transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean
surface).
(A) U1
- U2
(B) 1/U1
- 1/U2
(C) 1/U2
- 1/U1
(D) U2
- U1
by

1 Answer

Answer :

(B) 1/U1
- 1/U2
by

Related questions

Overall heat transfer co-efficient of a particular tube is U1 . If the same tube with some dirt deposited on either side has coefficient U2 , then (A) U1 = U2 (B) U2 > U1 (C) U1 > U2 (D) U1 = dirt factor - U2

Description : Overall heat transfer co-efficient of a particular tube is U1 . If the same tube with some dirt deposited on either side has coefficient U2 , then (A) U1 = U2 (B) U2 > U1 (C) U1 > U2 (D) U1 = dirt factor - U2

Last Answer : (A) U1 = U2

Pick out the wrong statement. (A) Superheated steam is preferably not used for process heating because of its low heat transfer film co-efficient (B) In a shell and tube heat exchanger, the shell pressure drop is maximum for orifice baffles (C) S.I. unit of fouling factor is Watt/m2 .°K (D) Longitudinal fins are used in extended surface heat exchangers, when the direction of fluid flow is parallel to the axis of the tube

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The overall heat transfer co-efficient for a shell and tube heat exchangerfor clean surfaces is U0 = 400 W/m2.K. The fouling factor after one year ofoperation is found to be hd0 = 2000 W/m2.K. The overall heat transfer co￾efficient at this time is(A) 1200 W/m2.K(B) 894 W/m2.K(C) 333 W/m2.K(D) 287 W/m2.K

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Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger? (A) Tube side pressure drop and the heat transfer rate (B) Convective heat transfer co-efficient (C) Effective tube surface area for convective heat transfer (D) All (A) (B) and (C)

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Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling? (A) Square pitch (B) Triangular pitch (C) Diagonal square pitch

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Steam is to be condensed in a shell and tube heat exchanger, 5 m long with a shell diameter of 1 m. Cooling water is to be used for removing the heat. Heat transfer co-efficient for the cooling water, whether on shell side or tube side is the same. The best arrangement is (A) Vertical heat exchanger with steam on tube side (B) Vertical heat exchanger with steam on shell side (C) Horizontal heat exchanger with steam on tube side (D) Horizontal heat exchanger with steam on shell side

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Baffles in the shell side of a shell and tube heat exchanger (A) Increase the cross-section of the shell side liquid (B) Force the liquid to flow parallel to the bank (C) Increase the shell side heat transfer co-efficient (D) Decrease the shell side heat transfer co-efficient

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Pick out the wrong statement. (A) 'Solvates' are chemical compounds formed by solute with their solvents. When water is the solvent, then it is called a 'hydrate' (B) In heat exchanger calculations (Δt) weighted is used in place of Δt, when it involves more than one sequence of heating or cooling i.e., desuperheating & condensation or condensation & sub-cooling (C) Heat transfer co-efficient during nucleate boiling is not influenced by the agitation imparted (D) In case of short tube vertical evaporators, area of central downtake is about 50 to 100% of the total tube cross-sectional area

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Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger? (A) Corrosiveness (B) Fouling characteristic (C) Viscosity (D) None of these

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Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger? (A) Corrosiveness & fouling characteristics (B) Pressure (C) Viscosity (D) Density

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Heat transfer efficiency leading of energy conservation in a heat exchanger can be achieved by (A) Keeping the heat transfer surface clean (B) Enhancing the fluid pumping rate (C) Increasing the tube length (D) None of these

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Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m2 .°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the (A) Higher condensing film co-efficient is desired (B) Condensate is corrosive in nature (C) Lower pressure drop through the exchanger is desired (D) Temperature of the incoming vapor is very high Answer: Option B

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Last Answer : (B) Supersaturated

For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of (A) 1 (B) 1.74 (C) 6.1 (D) 37

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Heat exchangers operating, when the asymptotic range is reached, (A) Provide very large heat transfer co-efficient (B) Results in making part of the heating surface inactive (C) Results in abruptly increased velocity (D) None of these

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The main purpose of providing fins on heat transfer surface is to increase the (A) Temperature gradient (B) Mechanical strength of the equipment (C) Heat transfer area (D) Heat transfer co-efficient

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Last Answer : (A) 165.4

Even though heat transfer co-efficient in boiling liquids is large, use of fins is advantageous, when the entire surface is exposed to __________ boiling. (A) Film (B) Nucleate (C) Transition (D) All modes of

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Last Answer : Option A

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Last Answer : (C) Accounts for additional resistances to heat flow

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Last Answer : (D) All (A), (B) and (C)

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Last Answer : (A) Penetration

Mass transfer co-efficient is directly proportional to DAB according to the __________ theory. (A) Film (B) Penetration (C) Surface-renewal (D) None of these

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Last Answer : (D) Be free from radiation damage and non-corrosive

. A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because (A) Total heat transfer area of all the effects is -less than that in a single effect evaporator system (B) Total amount of vapor produced per Kg of feed steam in a multiple effect system is much higher than in a single effect (C) Boiling point elevation in a single effect system is much higher than that in any effect in a multi-effect system (D) Heat transfer co-efficient in a single effect is much lower than that in any effect in a multi-effect system

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As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient (A) Continues to increase (B) Continues to decrease (C) Goes through a minimum (D) Goes through a maximum

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The unit of heat transfer co-efficient in SI unit is (A) J/M2°K (B) W/m2°K (C) W/m°K (D) J/m°K

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Last Answer : (D) Highly turbulent

Controlling heat transfer film co-efficient is the one, which offers __________ resistance to heat transfer. (A) No (B) The least (C) The largest (D) Lower

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Last Answer : (C) 50 -100 BTU/hr. ft. 2°F

In case of vertical tube evaporator, with increase in liquor level, the overall heat transfer co-efficient (A) Increases (B) Decreases (C) Is not affected (D) May increase or decrease; depends on the feed

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