Heat Transfer T...

An insulating material with a thermal conductivity, k = 0.12 W/mK is used for a pipe carrying steam. The local coefficient of heat transfer (h) to the surroundings is 4 W/m²K. In order to provide effective insulation, the minimum outer diameter of the pipe should be

The view factors F₁₂ and F_21, for the sphere of diameter d and a cubicle box of length l = d as shown in the figure, respectively, are

The heat conduction equation for 3D, steady state without heat generation is,

A fin is exposed to an environment where h₁ = 25 W/m²K. The effectiveness of the fin is ϵ₁. If the surrounding medium is changed and the value of changed h₂ = 10 W/m²K, the effectiveness is ϵ₂. The ratio \(\frac{{{\epsilon }_{1}}}{{{\epsilon }_{2}}}\) is ________

If the average Stanton number of a flow system is 5.585×10^-3 and Prandtl number is 0.7, the skin friction coefficient is _____×10^-3

The temperature variation in a body with negligible temperature gradient in unsteady state heat conduction is______

Match the following.

List 1 (Type of wall)	List 2(Temperature distribution)
1. Plane wall	a. Logarithmic
2. Cylindrical wall	b. hyperbolic
3. Spherical wall	c. parabolic
	d. straight line
	e. exponential

A grey body (ϵ = 0.8) emits the same amount of heat as black body at 1075 K. Find out the required temperature of the grey body

For transient heat transfer, fourier number is defined as ratio of

The heat flow rate through parallel walls of thickness L₁, L₂ and L₃, having surface areas A₁, A₂ and A₃, thermal conductivities k₁, k₂, and k₃, respectively, with the first and last walls maintained at temperatures t₁ and t₂ will be

For a given heat flow and for the same thickness, the temperature drop across the material will be maximum for

The specific heat ratio in a parallel flow heat exchanger is 0.420. The lower capacity rate is 800 W/K and the overall heat transfer coefficient is given as 800 W/m²K. To get the effectiveness of 0.52, what should be the area of heat exchanger (m²)?

The temperature distribution along a pin fin was found to varying with distance ‘x’ as:

T = 6x² - 5x + 3, where x is in meter.

Take thermal conductivity of fin material as 0.75 W/m K. The heat transfer from the base of the fin is ____________W/m². (Correct up to two decimal places)

A fluid of specific gravity 0.97 is being heated in a pipe whose diameter is 20 mm. The fluid flows with a velocity of 2 m/s at 283 K and the convective heat transfer coefficient at the outside surface of the pipe is 12 kW/m²K. If the length of the pipe is 7 m and the properties of water at mean temperature are given as: μ = 4 × 10^-4 kg/m-s and Pr = 2.54, then calculate the overall heat transfer coefficient in W/m²K

(Use k = 0.345 W/mK)

Steady two-dimensional heat conduction takes place in the body shown in the figure below. The normal temperature gradients over surfaces P and Q can be considered to be uniform. The temperature gradient  at surface Q is equal to 10 k/m. Surfaces P and Q are maintained at constant temperatures as shown in the figure, while the remaining part of the boundary is insulated. The body has a constant thermal conductivity of 0.1 W/m.K. The values of  and  at surface P are:

A plane wall is 25 cm thick with an area of 1 m², and has a thermal conductivity of 0.5 W/mK. If a temperature difference of 60°C is imposed across it, what is the heat flow?

A pin fin of length 40 cm, diameter 2 mm is fabricated of aluminum alloy (k = 140 W/mK). The base temperature of the fin is at 50°C and the surrounding air is at 25°C and h = 1000 W/m²K. The heat transfer rate from the fin assuming an adiabatic tip condition is _______ W.

The local heat transfer coefficient over a flat plate is given as h_x = Ax^-0.2. Find the ratio of average heat transfer coefficient to the local heat transfer coefficient at x = L.

A 100 W electric bulb has filament temperature of 3000° C. Assuming the filament to be black body, calculate the diameter of the wire if the length is 250 mm.

Which one of the following expresses the thermal diffusivity of a substance in terms of thermal conductivity (k), mass density (ρ) andspecific heat (c)?

In a heat, exchanger steam is condensing at 110˚C and heating the air flowing at 5 kg/s from 20˚C to 75˚C. It is desired to double the airflow at the same time to achieve an air outlet temperature of 75˚C by increasing the steam condensing temperature. The new condensing temperature is ____°C.

A gray and opaque surface at 0˚C in an environment at 250˚C. The surface has an emissivity of 0.8. If irradiation is 240 W/m², the radiosity of the surface is ______

The ratio of laminar hydrodynamic boundary layer thickness to a thermal boundary layer thickness of 2 fluids A and B on the flat plate is ½ and 2. Reynold's number of both plates is same.

For plate A: Prandtl number: 1/8, Nusselt number: 35

Find Prandtl number and Nusselt number of fluid B over a plate.

Select the correct answer using the codes given below:

A circular horizontal hot plate(T_wall = 70˚C) with a diameter of 70 mm is cooled with free convection in the atmosphere at 25˚C. Nusselt number is related to Rayleigh number as, Nu = 0.15 (Ra)^1/3, Pr = 0.7, ρ=1.21, ν = 15.52 × 10^-6 m²/s, k= 0.02435 W/mK. Find the heat transfer coefficient.