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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Furnaces For Casting Process
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Furnaces For Casting Process:
Furnaces are used for heating and melting of metals to be poured into the mold for casting.
The most important thing is the selection of furnaces which depends on:
Casting alloy melting and pouring temperature.
Capacity reqiurement of furnace.
Variety of metals or alloys to be melted.
Costs of investment.
Fuel and maintenance.
Environment Pollution.
Types of Furnace Used in Casting:
There are many furnaces among them we are discussing 5 of them:
1. Cupolas:
A type of furnace which is vertical cylinder furnace equipped with tapping spout near base.
Steps involved in this process are as follows:
Only used for cast iron.
It consist of a steel plate lined with refractory.
The charge consisting of iron, coke, flux, and alloying metal is loaded through a charging door located less than halfway up height of cupola.
Coke is used as fuel.
Forced air is introduced for combustion of coke.
Flux (limestone) is used to form slag.
2. Direct Fuel-Fired Furnaces (or Reverberatory Furnace):
Charge is heated in a small open-hearth by natural gas fuel burners located on the side of furnace.
Flame is reflecting down by the furnace roof.
Molten metal is released from the tap hole located at the bottom of hearth.
Natural gas is used as fuel.
Only for non-ferrous metal like copper-base alloys and aluminium.
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 temperature at which the tape is standardized. L = the measure length in m. For Foot Unit : C t = 6.45×10^-6 (T m – 68 )L For Metric Unit : C t = 1.16
Flexible Mechanical Elements Flexible mechanical elements are defined as, " I nelastic elements to transmit power over large distances " . Purpose of using FME's is to simplify the design of a machine and reduce the cost . Used as replacement for gears, shafts, bearings, other rigid power-transmission devices. It can absorb shock loads and vibrations. Positive Drive ⇛ no slip between driver and driven component. Element Life ⇛ no infinite life and should be replaced at the first sign of deterioration (check wear, aging, loss of electricity). Performance of Different Transmission Types Belts or Belt Drives Belts are used where center distance between shafts is large. Pulley axes must be separated by a certain minimum distance (depend upon belt type and size) to operate properly. Because of belt flexibility and damping capability ⇛ reduce the transmission of unwanted shock and vibration between shafts. Power and torque capacities are limited by COF and inter
Bulk Forming Processes: Bulk refers to workparts with low surface area to volume ratio. Bulk Forming uses heavy machine to apply three dimensional stresses. There are 4 basic operations used for bulk deformation: Rolling Forging Extrusion Wire & Bar Drawing 1. Rolling: Deformation process in which work thickness is reduced by compressive forces exerted by two opposite rolls. Variations in rolling are described ahead: A. Types of Rolling Based on Workpiece Geometry: I. Flat Rolling: It is used to reduce thickness of a rectangular cross-section. II. Shape Rolling: It is used to deform workpiece into contoured cross-section. B. Types of Rolling Based on Work Temperature: I. Hot Rolling: The material is heated to a uniform elevated temperature to achieve significant deformation. Parts are free from residual stresses. II. Cold Rolling: Hot materials (like plates or sheets) are further flatten by cold rolling to prepare them
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