A. Prandtl number
B. Grashoff number
C. Thermal conductivity
D. Viscosity
Correct Answer: Prandtl number ✔
Last Updated: March 03, 2019
Related MCQs
- 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__________?
- The main function of baffles provided in a shell and tube heat exchanger is to__________?
- Steam side heat transfer co-efficient in an evaporator is in the range of __________ kcal/hr.m2°C?
- The ratio of total radiating power to the absorptivity of the body depends upon the __________ as per Kirchoff‟s law?
- For small temperature difference, the heat transfer rate as per Newton’s law of cooling is proportional to (where, Δt = excess temperature) ?
- Overall heat transfer co-efficient for cooling of hydrocarbons by water is about__________?
- Intermittent tube cleaning is possible to be done in case of a __________ evaporator?
- In case of vertical tube evaporator, with increase in liquor level, the overall heat transfer co-efficient__________?
- In evaporators, lowering the feed temperature__________?
- Shell side pressure drop in a shell and tube heat exchanger does not depend upon the__________?
- The most conducive surface for dropwise condensation to occur is the __________ surface?
- Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be__________?
- The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) ?
- Analogy between mass and heat transfer is not applicable in case of__________?
- An evaporator while concentrating an aqueous solution from 10 to 40% solids evaporates 30000 kg of water. The amount of solids handled by the system in kg is__________?
- Steady state one dimensional heat flow by conduction as given by Fourier’s low does not assume that__________?
- Heat transfer co-efficient (h1) for liquids increases with__________?
- Multiple effect evaporators ar used to__________?
- In natural convection heat transfer, the correlating parameter is the__________?
- Correction is applied to LMTD for __________ flow?
- Increasing the liquor level in the evaporator results in the__________?
- In case of a shell and tube heat exchanger, the minimum and maximum baffle spacing is respectively (where, D = inside diameter of the shell) ?
- Double pipe heat exchangers are used__________?