A. Nusselt
B. Leidenfrost
C. Boiling
D. Burnout
Correct Answer: Leidenfrost ✔
Last Updated: March 03, 2019
Related MCQs
- In case of __________ boiling, the bubbles formed on a submerged hot surface get absorbed in the mass of the liquid?
- Nusselt number (for forced convection heat transfer) is a function of the __________ number?
- The separation of liquid droplets from the vapor is done by a/an __________ in the evaporators?
- For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is__________?
- In forced circulation, the heating element is injected__________?
- According to Reynolds analogy, Stanton number is equal to (where, f = Fanning friction factor) ?
- The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body)?
- The equivalent diameter for the annulus of a double pipe heat exchanger, whose inner pipe has fins on the outside is __________ compared to the same size pipes without fins?
- A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because__________?
- 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__________?
- Grashoff number, which is defined as g . β (Ts – T∞) ρ2. L3/μ2, is proportional to the ratio of buoyancy force to __________ force?
- If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows __________ law?
- Viscous & heat sensitive liquids are concentrated in __________ evaporators?
- In case of surface condensers, a straight line is obtained on plotting 1/U vs. __________ on an ordinary graph paper?
- Viscosity of gases __________ with increase in temperature?
- During crystallisation, formation of crystal can occur in __________ solution only?
- When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids ?
- Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m2.°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the__________?
- A cube, sphere & a thin circular plate (all having same mass and made of same material) are all heated to 300°C and allowed to cool in natural air. Which one will cool the slowest ?
- A steel sphere of radius 0.1 m at 400°K is immersed in an oil at 300°K. If the centre of the sphere reaches 350°K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions? Assume that the conductive heat transfer co-efficient is infinitely large ?
- Presence of a non-condensing gas in a condensing vapour__________?
- The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe) ?
- A process stream of dilute aqueous solution flowing at the rate of10 Kg.s-1 is to be heated. Steam condensate at 95°C is available for heating purpose, also at a rate of 10 Kg.s-1. A 1 – 1 shell and tube heat exchanger is available. The best arrangement is__________?
- Natural convection is characterised by__________?
- The unit of heat transfer co-efficient is__________?
- In Joule’s experiment, an insulated container contains 20 kg of water initially at 25°C. It is stirred by an agitator, which is made to turn by a slowly falling body weighing 40 kg through a height of 4 m. The process is repeated 500 times. The acceleration due to gravity is 9.8 ms-2. Neglecting the heat capacity of agitator, the temperature of water (in °C) is__________?
- Multiple effect evaporators are commonly used in the manufacture of P. Paper Q. Superphosphate R. Sugar S. Fats ?
- 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__________?
- Heat exchanger tubes are never made of__________?
- The variation of thermal conductivity of a metal with temperature is often correlated using an expression of the form K = K0 + at, where, K is the thermal conductivity and T is the temperature (in °K). The units of ‘a’ in SI system will be__________?
- Colburn analogy is applicable for the value of Prandtl number from__________?
- For what value of Prandtl number, the Col-burn analogy is valid ?
- The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are __________?
- Heat transfer rate per unit area is called__________?
- Tube pitch is the __________ of tube diameters and the clearances?
- A black body when hot, emits heat radiation of __________ wavelengths?
- With increase in temperature, the thermal conductivity of non-metallic amorphous solids__________?
- Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger ?
- Value of Nusselt number [Nu = (hD/k)] for the heat transfer by conduction from a droplet or a spherical particle to a surrounding stagnant film is__________?
- The main purpose of providing fins on heat transfer surface is to increase the__________?
- When vaporisation takes place through a blanketting film of gas, the phenomenon is termed as __________ boiling?
- The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the right face is 10 W/m2.K. At steady state, the temperature of the right face in °C is__________?
- Agitated film evaporator is suitable for concentrating __________ liquids?
- Kirchoff’s law is applicable to__________?
- The Dittus-Boelter equation for convective heat transfer [(i.e. h = 0.023 (K/D) (Re)0.8 (Pr)0.4] cannot be used for__________?
- The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m2. The flux, when the element temperature is increased to 1000°C for the same furnace temperature is__________?
- A composite flat wall of a furnace is made of two materials ‘A’ and ‘B’. The thermal conductivity of ‘A’ is twice of that of material ‘B’, while the thickness of layer of ‘A’ is half that of B. If the temperature at the two sides of the wall are 400 and 1200°K, then the temperature drop (in °K) across the layer of material ‘A’ is__________?
- In forced convection, the heat transfer depends on __________?
- Kg of liquid evaporated per hour in an evaporator is defined as its__________?
- In SI units, fouling factor is expressed in __________?
- Radiation heat losses from satisfactorily insulated high pressure boiler may be about __________ percent?