For a heat exchanger, will the overall heat transfer coefficient increase along with an increase in LMTD (log mean temperature difference) around the unit?

For a heat exchanger, will the overall heat transfer coefficient increase along with an increase in  LMTD (log mean temperature difference) around the unit?
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1 Answer

Answer :

The overall heat transfer coefficient is generally weakly dependent on temperature. As the  temperatures of the fluids change, the degree to which the overall heat transfer coefficient will be  affected depends on the sensitivity of the fluid’s viscosity to temperature. If both fluids are water, for  example, the overall heat transfer coefficient will not vary much with temperature because water’s
viscosity does not change dramatically with temperature. If, however, one of the fluids is oil which may  have a viscosity of 1000 cP at 50 °F and 5 cP at 400 °F, then indeed the overall heat transfer coefficient  would be much better at higher temperatures since the oil side would be limiting. Realize that the  overall heat transfer coefficient is dictated by the local heat transfer coefficients and the wall resistances  of the heat exchanger. The local heat transfer coefficients are dictated by the fluid’s physical properties  and the velocity of the fluid through the exchanger. So, for a given heat exchanger, fluid flow rates, and  characteristics of each fluid….the area of the exchanger and the overall heat transfer coefficients are  fixed (theoretically anyway….as the overall heat transfer coefficient does vary slightly along the length of  the exchanger with temperature as I’ve noted and the U-value will decrease over time with fouling).
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Related questions

Log mean temperature difference (LMTD) cannot be used, if (A) Heat transfer co-efficient over the entire heat exchanger is not constant (B) There exists an unsteady state (C) The heat capacity is not constant and there is a phase change (D) None of these

Description : Log mean temperature difference (LMTD) cannot be used, if (A) Heat transfer co-efficient over the entire heat exchanger is not constant (B) There exists an unsteady state (C) The heat capacity is not constant and there is a phase change (D) None of these

Last Answer : (D) None of these

In a parallel flow heat exchanger, if the outlet temperature of hot and cold fluids are the same, then the log mean temperature difference (LMTD) is (A) Minimum (B) Maximum (C) Zero (D) Infinity

Description : In a parallel flow heat exchanger, if the outlet temperature of hot and cold fluids are the same, then the log mean temperature difference (LMTD) is (A) Minimum (B) Maximum (C) Zero (D) Infinity

Last Answer : (C) Zero

Pick out the wrong statement. (A) The controlling resistance in case of heating of air by condensing steam is in the air film (B) The log mean temperature difference (LMTD) for counter flow and parallel flow can be theoretically same when any one of the fluids (hot or cold fluid) passes through the heat exchanger at constant temperature (C) In case of a 1 - 2 shell and tube heat exchanger, the LMTD correction factor value increases sharply, when a temperature cross occurs (D) Phase change in case of a pure fluid at a given pressure from liquid to vapor or vice-versa occurs at saturation temperature

Description : Pick out the wrong statement. (A) The controlling resistance in case of heating of air by condensing steam is in the air film (B) The log mean temperature difference (LMTD) for ... a pure fluid at a given pressure from liquid to vapor or vice-versa occurs at saturation temperature

Last Answer : (C) In case of a 1 - 2 shell and tube heat exchanger, the LMTD correction factor value increases sharply, when a temperature cross occurs

For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it (A) Decreases the pressure drop (B) Decreases the outlet temperature of cooling medium (C) Increases the overall heat transfer coefficient (D) None of these

Description : For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it (A) Decreases the pressure drop (B) ... the outlet temperature of cooling medium (C) Increases the overall heat transfer coefficient (D) None of these

Last Answer : (C) Increases the overall heat transfer coefficient

In a heat exchanger, floating head is provided to (A) Facilitate cleaning of the exchanger (B) Increase the heat transfer area (C) Relieve stresses caused by thermal expansion (D) Increase log mean temperature gradient

Description : In a heat exchanger, floating head is provided to (A) Facilitate cleaning of the exchanger (B) Increase the heat transfer area (C) Relieve stresses caused by thermal expansion (D) Increase log mean temperature gradient

Last Answer : (C) Relieve stresses caused by thermal expansion

In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid (A) Varies directly as the area and the LMTD (B) Directly proportional to LMTD and inversely proportional to the area (C) Varies as square of the area (D) None of these

Description : In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid (A) Varies directly as the area and the LMTD (B) Directly proportional to LMTD and inversely proportional to the area (C) Varies as square of the area (D) None of these

Last Answer : (A) Varies directly as the area and the LMTD

In a 1-1 concurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is (A) ∞ (B) 0 (C) Equal to the difference between hot and cold fluids inlet temperature (D) Equal to the difference between hot fluid inlet temperature and cold fluid outlet temperature

Description : In a 1-1 concurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is (A) ∞ (B) 0 ... temperature (D) Equal to the difference between hot fluid inlet temperature and cold fluid outlet temperature

Last Answer : (B) 0

LMTD correction factor which is to be applied for a cross-flow heat exchanger increases with increase in the number of shell passes. Its value for a single pass cross flow heat exchanger is (A) 0 (B) 1 (C) > 1 (D) < 1

Description : LMTD correction factor which is to be applied for a cross-flow heat exchanger increases with increase in the number of shell passes. Its value for a single pass cross flow heat exchanger is (A) 0 (B) 1 (C) > 1 (D) < 1

Last Answer : (D) < 1

Out of the following four assumptions used in the derivation of theequation for LMTD[LMTD = (∆t1- ∆t2)/ln(∆t1/∆t2)], which one is subject to the largest deviationin practice ?(A) Constant overall heat transfer co-efficient.(B) Constant rate of fluid flow(C) Constant specific heat(D) No partial phase change in the system

Description : Out of the following four assumptions used in the derivation of theequation for LMTD [LMTD = (∆t1 - ∆t2 )/ln(∆t1 /∆t2 )], which one is subject to the largest deviation in practice ? (A) Constant ... (B) Constant rate of fluid flow (C) Constant specific heat (D) No partial phase change in the system

Last Answer : (B) Constant rate of fluid flow

The outlet temperature of cooling water in a heat exchanger is generally not allowed to exceed above 50°C in industrial practice mainly to avoid (A) Its evaporation loss (B) Excessive corrosion (C) Uneconomic LMTD (D) Decrease in heat exchanger efficiency

Description : The outlet temperature of cooling water in a heat exchanger is generally not allowed to exceed above 50°C in industrial practice mainly to avoid (A) Its evaporation loss (B) Excessive corrosion (C) Uneconomic LMTD (D) Decrease in heat exchanger efficiency

Last Answer : (B) Excessive corrosion

In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always (A) < 1 (B) > 1 (C) 1 (D) ∞

Description : In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always (A) < 1 (B) > 1 (C) 1 (D) ∞

Last Answer : (A) < 1

LMTD for counter-flow and parallel flow heat exchanger will be the same, when the (A) Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid) (B) Outlet temperature of both the hot and cold fluid are same (C) Outlet temperature of hot fluid is less than the outlet temperature of the cold fluid (D) None of these

Description : LMTD for counter-flow and parallel flow heat exchanger will be the same, when the (A) Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid) (B) Outlet temperature of ... temperature of hot fluid is less than the outlet temperature of the cold fluid (D) None of these

Last Answer : (A) Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid)

It is not recommended to use a 1-2 shell and tube heat exchanger for a particular heat duty, whenever the LMTD correction factor is (A) > 0.75 (B) < 0.75 (C) < 0.50 (D) < 0.25

Description : It is not recommended to use a 1-2 shell and tube heat exchanger for a particular heat duty, whenever the LMTD correction factor is (A) > 0.75 (B) < 0.75 (C) < 0.50 (D) < 0.25

Last Answer : (B) < 0.75

LMTD can't be used as such without a correction factor for the (A) Multipass heat exchanger (B) Baffled heat exchanger (C) Condensation of mixed vapour in a condenser (D) All (A) (B) and (C)

Description : LMTD can't be used as such without a correction factor for the (A) Multipass heat exchanger (B) Baffled heat exchanger (C) Condensation of mixed vapour in a condenser (D) All (A) (B) and (C)

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

For a multipass shell and tube heat exchanger, the LMTD correction factor is always (A) 1 (B) > 1 (C) < 1 (D) Between 1 & 2

Description : For a multipass shell and tube heat exchanger, the LMTD correction factor is always (A) 1 (B) > 1 (C) < 1 (D) Between 1 & 2

Last Answer : (C) < 1

Hot water (0.01 m3 /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m3 /min) of density 800 kg/m3 and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately (A) 32 (B) 37 (C) 45 (D) 50

Description : Hot water (0.01 m3 /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m3 /min) of density 800 kg/m3 and specific heat of ... mean temperature difference in °C is approximately (A) 32 (B) 37 (C) 45 (D) 50

Last Answer : (A) 32

Terminal point temperature differences between fluids in case of a heat exchanger is termed as (A) Approach (B) Log mean temperature difference (C) Arithmetic mean temperature difference (D) Geometric mean temperature difference

Description : Terminal point temperature differences between fluids in case of a heat exchanger is termed as (A) Approach (B) Log mean temperature difference (C) Arithmetic mean temperature difference (D) Geometric mean temperature difference

Last Answer : (A) Approach

Pick out the wrong statement. (A) The condensing film co-efficient is about 3 times lower for vertical condenser as compared to the equivalent horizontal condenser for identical situation (B) Film co-efficient for vaporisation decreases as a result of vapor binding (C) In industrial practice, sub-cooling of condensate is required, when thecondensate is a volatile liquid and is to be transferred for storage(D) Overall heat transfer co-efficient in a heat exchanger is controlled by thevalue of the film co-efficient, which is higher

Description : Pick out the wrong statement. (A) The condensing film co-efficient is about 3 times lower for vertical condenser as compared to the equivalent horizontal condenser for identical situation ( ... in a heat exchanger is controlled by the value of the film co-efficient, which is higher

Last Answer : (D) Overall heat transfer co-efficient in a heat exchanger is controlled by the value of the film co-efficient, which is higher

Give the unit of overall heat transfer coefficient in SI and MKS.

Description : Give the unit of overall heat transfer coefficient in SI and MKS.

Last Answer : Unit of overall heat transfer coefficient 1. In SI : W/m2K 2. In MKS : kcal/hr m2K

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

Description : 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

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

H2S is being absorbed in a gas absorber unit. The height of the transfer unit based on the overall mass transfer coefficient on the gas side is 0.4 m. The equilibrium data is given by, y = 1.5 x. The bulk concentration of H2S has to be reduced from 0.05 to 0.001 mole fraction in the gas side. The height of the tower (in metres) corresponding to an operating line given by, y = 5x + 0.001 is (A) 2.0 (B) 1.56 (C) 1.0

Description : H2S is being absorbed in a gas absorber unit. The height of the transfer unit based on the overall mass transfer coefficient on the gas side is 0.4 m. The equilibrium data is given by, y = 1.5 x. The bulk concentration of H2S ... by, y = 5x + 0.001 is (A) 2.0 (B) 1.56 (C) 1.0

Last Answer : (A) 2.0

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

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

Description : 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

Last Answer : (C) Both (A) and (B)

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

Description : 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 ... surface heat exchangers, when the direction of fluid flow is parallel to the axis of the tube

Last Answer : (C) S.I. unit of fouling factor is Watt/m2 .°K

For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area (A) Increases (B) Decreases (C) Remain constant (D) Passes through a maxima

Description : For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area (A) Increases (B) Decreases (C) Remain constant (D) Passes through a maxima

Last Answer : (D) Passes through a maxima

Pick out the wrong statement. (A) The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one (B) Sherwood number for flow in pipes can be expressed as the ratio of the concentration gradient at wall to the overall concentration difference (C) According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by DAB(B)P - 3, Q - 2 (D) The z-component of the total mass flux of a component A in binary mixture of A and B is given by - Dab'.dCA/dz

Description : Pick out the wrong statement. (A) The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one (B) Sherwood number for flow in pipes can be expressed ... flux of a component A in binary mixture of A and B is given by - Dab'.dCA/dz

Last Answer : (C) According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by DAB(B)P - 3, Q - 2

In case of a multipass shell and tube heat exchanger, providing a baffle on the shell side __________ the heat transfer rate. (A) Increases (B) Decreases (C) Does not affect (D) May increase or decrease, depends on the type of baffle

Description : In case of a multipass shell and tube heat exchanger, providing a baffle on the shell side __________ the heat transfer rate. (A) Increases (B) Decreases (C) Does not affect (D) May increase or decrease, depends on the type of baffle

Last Answer : (A) Increases

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

Description : 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

Last Answer : (C) Increase the shell side heat transfer co-efficient

Use of transverse baffles in a shell and tube heat exchanger is done to increase the (A) Rate of heat transfer (B) Flow velocity (C) Turbulence of shell side fluid (D) All (A), (B) and (C)

Description : Use of transverse baffles in a shell and tube heat exchanger is done to increase the (A) Rate of heat transfer (B) Flow velocity (C) Turbulence of shell side fluid (D) All (A), (B) and (C)

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

Water is a better coolant than a gas (like CO2 , He, N2 etc.), because it (A) Is a better neutron moderator as well (B) Require comparatively smaller pumps and heat exchanger for a given heat transfer rate (C) Has a better heat transfer characteristics, and it can be pressurised to attain a high temperature (D) All (A), (B) and (C)

Description : Water is a better coolant than a gas (like CO2 , He, N2 etc.), because it (A) Is a better neutron moderator as well (B) Require comparatively smaller pumps and heat exchanger for a given heat transfer rate ... , and it can be pressurised to attain a high temperature (D) All (A), (B) and (C)

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

In a shell and tube heat exchanger, floating head is used for (A) Large temperature differentials (B) High heat transfer co-efficient (C) Low pressure drop (D) Less corrosion of tubes

Description : In a shell and tube heat exchanger, floating head is used for (A) Large temperature differentials (B) High heat transfer co-efficient (C) Low pressure drop (D) Less corrosion of tubes

Last Answer : (A) Large temperature differentials

. If a single tube pass heat exchanger is converted to two pass, then for the same flow rate, the pressure drop per unit length in tube side will (A) Increase by 1.8 times (B) Decrease by 2 2 (C) Increase by 2 16 (D) Remain unchanged

Description : . If a single tube pass heat exchanger is converted to two pass, then for the same flow rate, the pressure drop per unit length in tube side will (A) Increase by 1.8 times (B) Decrease by 2 2 (C) Increase by 2 16 (D) Remain unchanged

Last Answer : (C) Increase by 2 16

The rate of heat transfer is a product of overall heat transfer co￾efficient, the difference in temperature and the (A) Heating volume (B) Heat transfer area (C) Nusselt number (D) None of these

Description : The rate of heat transfer is a product of overall heat transfer co￾efficient, the difference in temperature and the (A) Heating volume (B) Heat transfer area (C) Nusselt number (D) None of these

Last Answer : (B) Heat transfer area

case of condensers & evaporators operating under given terminal conditions, LMTD (logarithmic mean temperature difference) for counter flow as compared to that for parallel flow is (A) More (B) Less (C) Equal (D) Much more

Description : case of condensers & evaporators operating under given terminal conditions, LMTD (logarithmic mean temperature difference) for counter flow as compared to that for parallel flow is (A) More (B) Less (C) Equal (D) Much more

Last Answer : Option C

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

Description : 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

Last Answer : (B) Decreases

In a counter flow heat exchanger, hot fluid enters at 170°C & leaves at 150°C, while the cold fluid enters at 50°C & leaves at 70°C. The arithmetic mean temperature difference in this case is __________ °C. (A) 20 (B) 60 (C) 120 (D) ∞

Description : In a counter flow heat exchanger, hot fluid enters at 170°C & leaves at 150°C, while the cold fluid enters at 50°C & leaves at 70°C. The arithmetic mean temperature difference in this case is __________ °C. (A) 20 (B) 60 (C) 120 (D) ∞

Last Answer : (D) ∞

In a plate type heat exchanger, heat transfer plates are never made of (A) Stainless steel (B) Cast iron (C) Titanium (D) Hastelloy C

Description : In a plate type heat exchanger, heat transfer plates are never made of (A) Stainless steel (B) Cast iron (C) Titanium (D) Hastelloy C

Last Answer : (B) Cast iron

. In a shell and tube heat exchanger, the tube side heat transfer co￾efficient just at the entrance of the tube is (A) Infinity (B) Zero (C) Same as average heat transfer co-efficient for tube side (D) None of these

Description : . In a shell and tube heat exchanger, the tube side heat transfer co￾efficient just at the entrance of the tube is (A) Infinity (B) Zero (C) Same as average heat transfer co-efficient for tube side (D) None of these

Last Answer : (A) Infinity

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

Description : 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

Last Answer : (A) Keeping the heat transfer surface clean

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

Description : 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 ... The amount of heat involved in the condensation or vaporisation of 1 kg of a fluid is the same

Last Answer : (A) Heat transfer by radiation cannot occur across an absolute volume

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

Description : 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 ... ) Horizontal heat exchanger with steam on tube side (D) Horizontal heat exchanger with steam on shell side

Last Answer : (B) Vertical heat exchanger with steam on shell side

A fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter 'd'. For a fixed mass flow rate, the tube side heat transfer co￾efficient for turbulent flow conditions is proportional to (A) d 0.8 (B) d -0.2 (C) d -1 (D) d -1.8

Description : A fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter 'd'. For a fixed mass flow rate, the tube side heat transfer co￾efficient for turbulent flow conditions is proportional to (A) d 0.8 (B) d -0.2 (C) d -1 (D) d -1.8

Last Answer : (B) d -0.2

The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by __________ times, when the number of tube passes is increased to 8. (A) 2 0.8 (B) 4 0.8 (C) 4 0.4 (D) 2 0.4

Description : The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by __________ times, when the number of tube passes is increased to 8. (A) 2 0.8 (B) 4 0.8 (C) 4 0.4 (D) 2 0.4

Last Answer : (B) 4 0.8

Air is to be heated by condensing steam. Two heat exchangers are available (i) a shell and tube heat exchanger and (ii) a finned tube heat exchanger. Tube side heat transfer area are equal in both the cases. The recommended arrangement is (A) Finned tube heat exchanger with air inside and steam outside (B) Finned tube heat exchanger with air outside and steam inside (C) Shell and tube heat exchanger with air inside tubes and steam on shell side (D) Shell and tube heat exchanger with air on shell side and steam inside tubes

Description : Air is to be heated by condensing steam. Two heat exchangers are available (i) a shell and tube heat exchanger and (ii) a finned tube heat exchanger. Tube side heat transfer area are equal in both ... steam on shell side (D) Shell and tube heat exchanger with air on shell side and steam inside tubes

Last Answer : (B) Finned tube heat exchanger with air outside and steam inside

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)

Description : 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)

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

For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it (A) Occupies smaller space (B) Is more economical (C) Is easy to operate and maintain (D) All (A), (B) and (C)

Description : For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it (A) Occupies smaller space (B) Is more economical (C) Is easy to operate and maintain (D) All (A), (B) and (C)

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

The advantage of using a 1 - 2 shell and tube heat exchanger over a 1 - 1 shell and tube heat exchanger is (A) Lower tube side pressure drop (B) Lower shell side pressure drop (C) Higher tube side heat transfer co-efficient (D) Higher shell side heat transfer co-efficient

Description : The advantage of using a 1 - 2 shell and tube heat exchanger over a 1 - 1 shell and tube heat exchanger is (A) Lower tube side pressure drop (B) Lower shell side pressure drop (C) Higher tube side heat transfer co-efficient (D) Higher shell side heat transfer co-efficient

Last Answer : (C) Higher tube side heat transfer co-efficient

Extremely large or small volumes of fluids are generally best routed through the shell side of a shell and tube heat exchanger, because of the (A) Less corrosion problems (B) Flexibility possible in the baffle arrangement (C) Low pressure drop (D) High heat transfer co-efficient

Description : Extremely large or small volumes of fluids are generally best routed through the shell side of a shell and tube heat exchanger, because of the (A) Less corrosion problems (B) Flexibility possible in the baffle arrangement (C) Low pressure drop (D) High heat transfer co-efficient

Last Answer : (B) Flexibility possible in the baffle arrangement

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

Description : 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 ... vertical evaporators, area of central downtake is about 50 to 100% of the total tube cross-sectional area

Last Answer : (C) Heat transfer co-efficient during nucleate boiling is not influenced by the agitation imparted