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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Clutch
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Clutch
It is defined as, "a machine element component used to connect driver shaft to a driven shaft".
It will stop driven shaft without altering driven shaft using lever.
Driver ↔ anything which produces power is called Primover or Driver.
Driven Machinery ↔ anything which consume this power is called Load or Driven Machinery.
Design Considerations
Design consideration factors are described ahead:
Coefficient of Friction ↔ should be high enough to hold load and minimum amount of axial force.
Moment of Inertia ↔ clutch moving components should have less weight to minimize inertia load at high speed.
Heat Generated at Contact Surfaces ↔ heat should dissipate rapidly.
Wearing of surfaces ↔ provision for taking up the wear of contact.
Cover Projecting Parts ↔ guard projecting parts for the provision of easy repair.
Material Requirement
The actual friction surface is friction lining which gets in severe rubbing operation. Qualities of material of friction surfaces are:
It should have high coefficient of friction.
It should have high resistance (prowear).
It should withstand a high compression load.
It should be chemically inert which means oil or air has no effect on them.
It should have high heat conductivity.
Have excellent compatibility with cast iron facing.
Types of Clutches
There are two types of Clutches which are discussed below
1. Positive Type Clutch
It is used when there is no slip between driver and driven shaft (means both have same speed under any condition).
Power is transmitted using interlock of jaws (or teeth).
Used where synchronous power transmission required.
Engagement is not possible at high speed (limited to 600 rpm).
There are two types of Positive Type Clutch:
Square Jaw Clutch ↔ It transmitted power in both direction (CW or CCW).
Spiral Jaw Clutch ↔ Transmit power in one direction (left or right handed).
2. Friction Type Clutch
Power is transmitted due to friction between surfaces (clutch disk and plane surfaces).
The driver shaft get contact with other shaft by means of compression springs.
It consist of inner curve which is attached to the driven shaft and follow cone.
Male cone is movable and can axially move over the driven member.
Inner side of female cone (fixed) fits outer side of male cone.
Slope of cone is small which gives high normal force (angle 8-15 degrees).
Fork lever is used to dis-engage clutch.
b. Centrifugal Clutch
It is used to disengage driven shaft at a particular speed.
It is used engine which has trouble in starting under load.
It has number of shoes or friction pads arranged radically in symmetric position inside a rim.
Working of Centrifugal Clutch
Spring produce inward force to kept in original position.
As speed increase ↔ centrifugal force increases.
If centrifugal force = spring force ↔ shoes start floating.
If spring force < centrifugal force ↔ shoes moves outward and touch the surface of drum ↔ torque is transmitted.
As load increases, speed decreases ↔ shoes come to original position.
c. Plate or Disc Clutch
It consist of two flanges. One of them is lined with high friction material and rigidly keyed with driven shaft while the other is free to move along driven shaft due to splined connection.
Compression springs used to push these flanges against each other.
Torque is transmitted by friction.
Parts of Plate or Disc Clutch
Clutch Plate ↔ Main component. Single thin metallic disc having both sides frictional surfaces (friction lining) . It is assembled between flywheel and flange.
Pressure Plate ↔ to maintain proper contact between flywheel and clutch plate by means of spring.
Springs ↔ used to move clutch plate towards the flywheel to ensure proper contact between flywheel and clutch plate.
Flywheel ↔ connected to engine output shaft and used to transmit power.
Working of Disc Clutch
Single plate is mounted on spline clutch shafts. Flywheel is mounted on engine crankshaft. When paddle is pressed clutch shaft moves in, spring loosen shaft disengaged.
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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