A. Aluminium foil
B. Coal dust
C. Refractory bricks
D. Iron plates
Correct Answer: Aluminium foil ✔
Last Updated: March 03, 2019
Related MCQs
- Convective heat transfer, in which heat is transferred by movement of warmed matter is described by__________?
- If h1 = inner film co-efficient and /h2 = outer film co-efficient, then the overall heat transfer co-efficient is__________?
- In an extended surface heat exchanger, fluid having lower co-efficient__________?
- The critical radius ‘r’ of insulation on a pipe is given by__________?
- In an interphase heat transfer process, the equilibrium state corresponds to equality of temperature in the two phases, while the condition for equilibrium in an interphase mass transfer process is equality of__________?
- A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2.°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be__________?
- Sensible heat of hot industrial flue gases cannot be recovered by a/an__________?
- In case of a vertical tube evaporator, with increase in the liquor level, the __________ is increased?
- The heat flux in the nucleate boiling regimes is proportional to (where, ΔT = excess temperature) ?
- In a multiple effect evaporator, the effect of boiling point elevation is to__________?
- Film condensation is promoted on a/an __________ surface?
- In a boiling curve, the peak heat flux is called the __________ point?
- 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__________?