Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the (A) Surrounding temperature (B) Average temperature of the fin (C) Temperature of the fin end (D) Constant temperature equal to that of the base

Extended heat transfer surface like fins are used to increase the heat

transfer rate. Fin efficiency is defined as the ratio of heat transferred across

the fin surface to the theoretical heat transfer across an equal area held at

the

(A) Surrounding temperature

(B) Average temperature of the fin

(C) Temperature of the fin end

(D) Constant temperature equal to that of the base

by

1 Answer

Answer :

(D) Constant temperature equal to that of the base

by

Related questions

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 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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Pick out the wrong statement. (A) Different solids have different equilibrium moisture curves (B) Total condenser or reboiler is considered equivalent to one theoretical plate in McCabe-Thiele method of theoretical plate calculation for distillation column (C) Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column (D) Even a forced draft cooling tower cannot cool water below the wet bulb temperature

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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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Coefficient of velocity is defined as the ratio of (A) Actual velocity of jet at vena contracta to the theoretical velocity (B) Area of jet at vena contracta to the area of orifice (C) Actual discharge through an orifice to the theoretical discharge (D) None of the above

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Which of the following situations can be approximated to a steady state heat transfer system? (A) A red hot steel slab (having outside surface temperature as 1300°C) exposed to the atmospheric air at 35°C (B) 10 kg of dry saturated steam at 8 kgf/cm2 flowing through a short length of stainless steel pipe exposed to atmospheric air at 35°C (C) Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180°C (D) A sub-cooled refrigerant liquid at 8°C flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35°C

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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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The second law of thermodynamics states that (A) The energy change of a system undergoing any reversible process is zero (B) It is not possible to transfer heat from a lower temperature to a higher temperature (C) The total energy of system and surrounding remains the same (D) None of the above

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Change in internal energy in a closed system is equal to heat transferred if the reversible process takes place at constant  (a) pressure  (b) temperature  (c) volume  (d) internal energy  (e) entropy.

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Change in enthalpy in a closed system is equal to heat transferred if the reversible process takes place at constant  (a) pressure  (b) temperature  (c) volume  (d) internal energy  (e) entropy.

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Which of the following is not applicable to fluidised bed combustion of coal? (A) It cannot burn low grade coal (B) It achieves higher fuel combustion efficiency (C) Less heat transfer surface area is required in boilers (D) None of these

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Co-efficient of discharge (Cd ) is defined as actual discharge/theoretical discharge and is equal to Cc . Cv ; where Cc = Co-efficient of contraction and Cv = co-efficient of velocity. Cd of an orifice is usually about (A) 0.42 (B) 0.62 (C) 0.82 (D) 0.98

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Last Answer : (B) 0.62

Co-efficient of discharge (Cd ) is defined as actual discharge/theoretical discharge and is equal to Cc . Cv ; where Cc = Co-efficient of contraction and Cv = co-efficient of velocity. Cd of an orifice is usually about (A) 0.42 (B) 0.62 (C) 0.82 (D) 0.98

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The product of efficiency & heat transferred to the working fluid is? a. Net temperature change b. Net work done c. Net enthalpy change d. None of the mentioned

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Universal gas constant is defined as equal to product of the molecular weight of the gas and  (a) specific heat at constant pressure  (b) specific heat at constant volume  (c) ratio of two specific heats  (d) gas constant  (e) unity.

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Air is best heated with steam in a heat exchanger of (A) Plate type (B) Double pipe type with fin on steam side (C) Double pipe type with fin on air side (D) Shell and tube type

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A high surface area to volume ratio in cells is important because it (a) Enables efficient transfer of wastes, nutrients and gases across the cell membrane (b) Prevents overproduction of cell proteins due to structural limitations (c) Allows many antigens on the surface for identification of self and non-self (d) Provides for better structural support to cope with external physical pressure

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Value of Nusselt number [Nu = (hD/k)] for the heat transfer byconduction from a droplet or a spherical particle to a surrounding stagnant film is (A) 0.5 (B) 2 (C) 10 (D) 100

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Heat transfer takes place through a liquid medium surrounding the submerged material under heating, in case of a/an (A) Blast furnace (B) Steam boiler (C) Salt bath furnace (D) Annealing furnace

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A hollow sphere and a solid sphere of the same material and equal radii are heated to the same temperature. In this case, (A) The cooling rate will be the same for the two spheres and hence the two spheres will have equal temperatures at any instant (B) Both the spheres will emit equal amount of radiation per unit time in the beginning (C) Both will absorb equal amount of radiation from the surrounding in the beginning (D) Both (B) & (C)

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Pick out the correct statement. (A) If an insoluble gas is passed through a volatile liquid placed in a perfectly insulated container, the temperature of the liquid will increase (B) A process is irreversible as long as Δ S for the system is greater than zero (C) The mechanical work done by a system is always equal to∫P.dV (D) The heat of formation of a compound is defined as the heat of reaction leading to the formation of the compound from its reactants

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What is an energy that can be transferred from one object to another causing a change in temperature of each object?  A. Power  B. Heat transfer  C. Heat  D. Work

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Otto cycle efficiency is higher than Diesel cycle efficiency for the same compression ratio and heat input because in Otto cycle  A. combustion is at constant volume  B. expansion and compression are isentropic  C. maximum temperature is higher  D. heat rejection is lower

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According to first law of thermodynamics  (a) work done by a system is equal to heat transferred by the system  (b) total internal energy of a system during a process remains constant  (c) internal energy, enthalpy and entropy during a process remain constant  (d) total energy of a system remains constant

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Rate of low temperature oxidation of coal due to bad storage conditions (A) Decreases with increase in surface area (B) Does not vary with increase in surface area (C) Is more for low volatile coal compared to high volatile coal (D) Is accelerated by storage in large heaps with small surface to volume ratio

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The following heat engine produces power of 100,000 kW. The heat engine operates between 800 K and 300 K. It has a thermal efficiency equal to 50% of that of the Carnot engine for the same temperature. The rate at which heat is absorbed from the hot reservoir is (A) 100,000 kW (B) 160,000 kW (C) 200,000 kW (D) 320,000 kW

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Last Answer : (D) 320,000 kW

A thin, flat & square plate measuring 2 m × 2 m is freely hanging in ambient air at 25°C. It is exposed to the solar radiation falling on one side of the plate at the rate of 500 W/m2. The plate temperature will remain constant at 30°C, if the convective heat transfer co-efficient is __________ W/m2 °C. (A) 50 (B) 100 (C) 150 (D) 200

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In a Carnot cycle, heat is transferred at  (a) constant pressure  (b) constant volume  (c) constant temperature  (d) constant enthaply  (e) any one of the above.

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In a heat exchanger, one transfer unit means (A) A section of the exchanger in which change in temperature of one stream equals the average driving force in the section (B) The size of the exchanger in which heat transfer rate is 1 kcal/hr (C) Both (A) and (B) (D) None of these

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Last Answer : (A) A section of the exchanger in which change in temperature of one stream equals the average driving force in the section

What is defined as the ratio of the net electrical power output to the rate of fuel energy input?  A. Combustion efficiency  B. Thermal efficiency  C. Overall efficiency  D. Furnace efficiency

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In counter flow compared to parallel flow, (A) LMTD is greater (B) Less surface area is required for a given heat transfer rate (C) Both (A) and (B) (D) More surface area is required for a given heat transfer rate

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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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Convective heat transfer, in which heat is transferred by movement of warmed matter is described by (A) Fourier's law (B) Newton's law of cooling (C) Fick's law (D) None of these

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. The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C-1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2 .°C-1 . The rate of heat loss from the outer surface in W.m-2 is (A) 165.4 (B) 167.5 (C) 172.5 (D) 175

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With increase in compression ratio, the efficiency of the otto engine (A) Increases (B) Decreases (C) Remain constant (D) Increases linearly

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Pick out the wrong statement. (A) Heat transfer by radiation cannot occur across an absolute volume (B) In case of a shell and tube heat exchanger, the pressure drop through the shell is proportional to the number of times the fluid crosses the bundle between baffles (C) Propagation velocity for travel of heat radiation through vacuum is equal to the velocity of the light (D) The amount of heat involved in the condensation or vaporisation of 1 kg of a fluid is the same

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Oxygen enrichment of combustion air does not result in increase of the (A) Flame temperature (B) Oxygen in the flue gas (C) Stack loss (D) Heat transfer rate in the furnace

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Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer co-efficient is ‘3k/l’. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade?(A) 35.5 (B) 43.75 (C) 81.25 (D) 48.25

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