A. Logarithmic mean area
B. Arithmetic mean area
C. Geometric mean area
D. None of these
Correct Answer: Logarithmic mean area ✔
Last Updated: March 03, 2019
Related MCQs
- The rate of emission of radiation by a body does not depend upon the__________?
- In a cooling tower, water becomes cool by__________?
- Out of the following four assumptions used in the derivation of the equation for LMTD [LMTD = (Δt1 – Δt2)/ln(Δt1/Δt2)], which one is subject to the largest deviation in practice ?
- What is the logarithmic mean of r1 and r2 ?
- The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is__________?
- The overall resistance for heat transfer through a series of flat resistance, is the __________ of the resistances?
- Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re 0.8. Pr n, is not valid, if the value of __________?
- An ejector is used to__________?
- In a laboratory test run, the rate of drying was found to be 0.5 x 10-3 kg/m2.s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry basis. A tray dryer is used to dry 100 kg (dry basis) of the same material under identical conditions. The surface area of the material is 0.04 m2/kg of dry solid. The time required (in seconds) to reduce the moisture content of the solids from 0.3 to 0.2 (dry basis) is__________?
- Peclet number (Pe) is given by__________?
- In Fourier’s law, the proportionality constant is called the__________?
- When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is __________?
- The units of resistance to heat transfer is __________?
- For hot feed, forward feeding as compared to backward feeding results in __________ economy?
- In sub-cooled boiling ?
- Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer cannot take place__________?
- The thickness of condensate layer in filmwise condensation depends on the__________?
- The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation?
- Steam economy in case of a triple effect evaporator will be __________?
- In a forward feed multiple effect evaporator unit__________?
- Dropwise condensation is promoted on a/an __________ surface?
- Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger ?
- It is desired to concentrate a 20% salt solution (20 kg of salt in 100 kg of solution) to a 30% salt solution in an evaporator. Consider a feed of 300 kg/min at 30°C. The boiling point of the solution is 110°C, the latent heat of vaporisation is 2100 kJ/kg and the specific heat of the solution is 4 kJ/kg.K. The rate at which the heat has to be supplied in (kJ/min) to the evaporator is__________?
- Fqra cold viscous feed, backward feed gives __________ than forward feed?
- The Graetz number is concerned with the__________
- The unit of conductance in SI unit is__________?
- Which of the following has the lowest Prandtl number ?
- In case of a multipass shell and tube heat exchanger, the temperature drop in the fluid __________?
- The capacity of double-effect evaporator is less than half of the capacity of two single effects, each of which is operating over same terminal temperature difference, when the__________ ?
- Nusselt number is a function of Prandtl number and __________ number of fluid in natural convection heat transfer?
- Radiation energy is emitted by all the substances, which are above__________?
- The dimensionless group in mass transfer that is equivalent to Prandtl number in heat transfer is__________?
- Loss of heat from untagged steam pipe to the ambient air is by __________?
- In Biot number, the characteristic length used is the ratio of the __________ of the solid?
- Boiling point elevation for a strong and concentrated solution is found by Duhring’s rule, which states that at the same pressure, the boiling point of a solution is a linear function of the __________ of pure water?
- Stefan-Boltzmann law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in °C T = absolute temperature in ° K) ?
- The equation, (NSt × N2/3 Pr) = f/2, is the __________ analogy ?
- The range of electromagnetic spectrum important in heat transfer by radiation is __________ microns?
- Boiling point of a solution according to Duhring’s rule is a linear function of the __________ of water?
- Prandtl number for most of dry gases is about__________?
- 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__________?
- The purpose of providing expansion bellows in the shell of tubular exchanger is to __________?
- Multipass heat exchangers are used__________?
- 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__________?
- Finned tube heat exchangers__________?
- Fruit juice (a heat sensitive material) can be concentrated in a __________ evaporator?
- The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter D. as __________?
- For heat flow through very thick walled cylinder, use __________mean radius?
- In a shell and tube heat exchanger, the shell side fluid velocity can‟t be changed by changing the__________?
- LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counter-flow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the __________ flow?
- The maximum heat transfer co-efficient from steam heating will be attained when the steam is__________?