A. High viscosity
B. High co-efficient of thermal expansion
C. Low temperature gradients
D. Low density change with temperature
Correct Answer: High co-efficient of thermal expansion ✔
Last Updated: March 03, 2019
Related MCQs
- Reynold’s analogy states that (where, St = Stanton number f = friction factor) ?
- A dephlegmator is a__________?
- Film boiling is usually not desired in commercial equipments, because__________?
- The advantage of backward feed multiple effect evaporators over forward feed units is that__________?
- In case of a multipass shell and tube heat exchanger, providing a baffle on the shell side __________ the heat transfer rate?
- With the increase of temperature, the Col-burn jH factor__________?
- Electromagnetic radiations propagate in vacuum with a velocity of __________ metre/second?
- In a heat exchanger, floating head is provided to__________?
- Which of the following accessories is provided in the vapor line of an evaporator for removing the entrained liquid ?
- The equivalent diameter for pressure drop is __________ that for heat transfer?
- As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient ?
- Fouling factor__________?
- If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid__________?
- The unit of heat transfer co-efficient in SI unit is__________?
- Which type of heat exchanger is preferred for heavy heat loads ?
- With increase in porosity, the thermal conductivity of a solid substance__________?
- Vacuum is generally maintained in the vapour space of an evaporator mainly to__________?
- The number of kg vaporised per kg of steam fed to the evaporator is defined as__________?
- Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone?
- Which of the following is unimportant in forced convection ?
- Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively) ?
- Dittus-Boelter equation cannot be used for molten metals mainly due to its very low__________?
- The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K = 0.04 W/m.°K and thickness 0.16m is 10 W/m2. The temperature of the inside wall is – 5°C. The outside wall temperature is__________?
- In a multipass shell and tube heat exchanger, tube side return pressure loss is equal to __________ the velocity head?
- Heat produced when a steady state current, I passes through an electrical conductor having resistance, ‘R’ is__________?
- The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by__________?
- Fourier’s law applies to the heat transfer by__________?
- As per Kirchoff‟s law, the ratio of the total radiating power to the absorptivity of a body depends on the__________?
- When vaporisation takes place directly at the heating surface, it is called__________?
- Thermal conductivity of a conducting solid material depends upon its__________?
- 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__________?
- The actual temperature drop across the heating surface in an evaporator depends on the__________?
- Heat flux is the time rate of heat transfer per unit__________?
- The steam ejector is used to__________?
- 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__________?
- Which of the following is generally considered as opaque surface towards radiations ?
- Fourier’s law of heat conduction applies to __________ surfaces?
- 200 kg of solids (on dry basis) is subjected to a drying process for a period of 5000 seconds. The drying occurs in the constant rate period with the drying rate as, Nc = 0.5 × 10-3 kg/m2.s. The initial moisture content of the solid is 0.2 kg moisture/kg dry solid. The interfacial area available for drying is 4 m2/1000 kg of dry solid. The moisture content at the end of the drying period is (in kg moisture/kg dry solid)?
- Harmonic mean temperature difference is given by__________?
- If average heat transfer co-efficient is ha and the local coefficient at the end of the plate is hl then in case of heat transfer to a fluid flowing over a flat plate, heated over its entire length__________?
- The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ΔT) between wall and outside bulk. The proportionality is given as__________?
- Heat transfer occurs by natural convection because change in temperature causes difference in__________?
- A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m3 and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m2.K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is__________?
- The ratio of momentum diffusivity to thermal diffusivity is the __________ number?
- What is the thermal conductivity of a perfect heat insulator ?
- The value of Stefan-Boltzmann constant in SI unit is__________?
- A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m2.K. The Biot number is __________?
- Air is best heated with steam in a heat exchanger of__________?
- Which is the most suitable for the concentration of foamy & frothy liquors ?
- The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2. The approximate surface temperature (K) is (Stefan-Boltzmann constant = 5.67 × 10-8 W/m2.K4) ?
- Boiling point elevation of an ideal solution__________?