View Factor Orientation (or View factor or shape factor) plays an important role in radiation heat transfer. View factor is defined as, "fraction of radiation leaving surface 'i' and strike 'j' ". Summation Rule (View Factor) If there is are similar surfaces 'i' and 'j' , then: Blackbody Radiation Exchange Radiation Exchange between Opaque, Diffuse, Gray surfaces in an Enclosure 1. Opaque 2. Surfaces 3. Two surface enclosure Radiation Shield It is used to protect surfaces from radiation act like a reflective surface. References: Material from Class Lectures + Book named Fundamentals of Heat and Mass Transfer by Theodore L. Bergman + My knowledge. Photoshoped pics are developed. Some pics and GIF from Google. Videos from YouTube ( Engineering Sights ).
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Friction
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Friction And it's Characteristics:
It is defined as;
A force which resists the movement of two contacting surface that slide relative to one another.
The force always acts tangent to the point of contact and is directed opposite to the existing motion between the surfaces.
Types of Dry Friction Problems:
There three types of problems of Dry Friction:
1. No Apparent Impending Motion:
The body is about to slip. For the body not to slip Fs ≥ Us N, otherwise the body may slip. Only equilibrium equations are used.
2. Impending Motion at all Points of Contact:
In this scenario, equilibrium equations as well as frictional motion equation are used.
3. Impending Motion at some Points of Contact:
The body might get slip. In this scenario, number of unknowns are less than the equilibrium and frictional motion equation.
Impending Motion:
Impending motion refers to the state just before the surfaces start to slip.
Tipping Effect:
The effect in which body rotate and fall on its side when the moment due to pushing force becomes greater than the moment due to the force of gravity.
Mpushing force ＞ Mgravity force
Difference Between Slipping and Tipping of a Body:
1. Slipping Effect:
When the pushing force will exceed the maximum static friction force and the box will begin to slide across the surface.
Fpushing force ＞ Ffrictional force
2. Tipping Effect:
When the pushing force and the friction force will create a strong enough couple that the box will rotate and fall on its side.
Mpushing force ＞ Mgravity force
Tipping Point:
When a body's center of gravity is above the area formed by the support base, the normal force can provide the necessary moment to remain in rotational equilibrium.
TAPING CORRECTIONS There are two types of corrections depending upon the type of errors in tape due to the different conditions. 1. Systematic Errors : Slope Erroneous tape length Temperature Tension Sag 2. Random Errors : Slope Alignment Marking & Plumbing Temperature Tension & Sag 1. Temperature Correction It is necessary to apply this correction, since the length of a tape is increased as its temperature is raised, and consequently, the measured distance is too small. It is given by the formula, C t = 𝛼 (T m – T o )L Where, C t = the correction for temperature, in m. 𝛼 = the coefficient of thermal expansion. T m = the mean temperature during measurement. T o = the tempe...
Projection: The term Projection is defined as: Presentation of an image or an object on a surface. The principles used to graphically represent 3-D objects and structures on 2-D media and it based on two variables: Line of Sight. Plane of Projection. Line of Sight & Plane of Projection: Line of sight is divided into 2 types: Parallel Projection Converging Projection & A plane of projection is an imaginary flat plane upon which the image created by the lines of sight is projected. Orthographic Projection: When the projectors are parallel to each other and perpendicular to the plane of projection. The lines pf sight of the observer create a view on the screen. The screen is referred to as the Plane of Projection (POP). The lines of sight are called Projection lines or projectors. Rules of Orthographic Projection: Edges that are parallel to a plane of projection appear as lines. Edges that are incl...
Diffusion It is defined as, " The transportation of one atom from one state into other state " . Used for hardening of surfaces like die parts, gear, bolt, machine element. Hardening can be done using Temperature-Heat treatment ( diffusion couple ). There are two types of diffusion: Inter-diffusion ↔ in which atoms tend to migrate from region of high concentration to low concentration . Self-diffusion ↔ in which atoms migrate within a solid. Diffusion Mechanism There can be two conditions of moving atoms Empty spaces between adjacent sites. Atoms have sufficient energy to break bond with neighbors atoms which cause lattice distortion during displacement. If we rise temperature, small fractions of atoms is capable of diffusive motion (which cause lattice distortion). Types of Diffusion 1. Vacancy Diffusion It is defined as, " interchange of an atom from a normal lattice position to the adjacent vacant lattice site " . Extent of vacancy diffusion is a function...
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