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 ).
It is defined as, "Laminar flow of viscous fluid in the space between two parallel plates (one of which is moving relative to the other)".
Flow is driven by:
Viscous drag force acting at the fluid.
Applied pressure gradient parallel to the plates.
Application are:
Hydro-static lubrication
Viscosity pumps
Turbine
Applied to Journal bearings (used in mechanical systems).
3. Steady, Incompressible & Laminar Flow in a Circular Tube
It is defined as, "Steady, incompressible and laminar flow through a straight circular tube of constant cross-section". It is also called Hagen-Poiseuille Flow.
Lubrication
Navier-stokes equation used to find out the velocity profile inside a bearing. There are 3 types of lubrication:
Full Film Lubrication ↦ Bearing surfaces are fully separated by a film of lubricant.
Boundary Lubrication ↦ Bearing surfaces physically come into contact.
Mixed Film Lubrication ↦ Combination of partial lubricant films and some asperity (roughness/difficult to endure) contact between the surfaces.
Full film lubrication is further divided into the following:
Hydrostatic ↦ Surfaces are separated by an externally pressurized lubricant.
Hydrodynamics ↦ Surfaces are separated by a dynamic film of lubricant.
Elastohydrodynamic ↦ Characterized by elastic deflections of the surfaces under very high pressures within the contact zone with an increase in viscosity of the fluid.
Hydrodynamic Lubrication
It is governed by Reynold's equation of Classical Lubrication Theory which came into existence by assuming:
Liquid flowing through thin region separated by 2 moving surfaces.
Pressure does not vary across the film.
Appropriate boundary conditions required for Reynold's equation solution.
Reynold's Equation
It is defined as, "Analysis of Momentum Transport and Continuity equations leads to a single elliptic DE".
Analysis served as a basis of designing hydrodynamically lubricated bearings.
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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