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 ).
Several processing operations are done for the manufacturing gears, which are as:
Performing of Blank (with or without) ↠ important part of gears.
Annealing of Blank (Forged or Cast steel)
Machining of Gear Blank
Producing Teeth or Machining of Teeth
Finishing of Teeth (by shearing, grinding) ↠ if required
Full or Surface Hardening of Machined Gear ↠ case hardening
Inspection and Testing of Finished Gears
Manufacturing process involves following categories:
Forming ↠ shaping of plastic deformation in which volume remains constant (approx.) before and after the process. E.g.: Direct casting, rolling, powder metallurgy, injection molding, drawing, extrusion, stamping, forging, etc.
Machining ↠ shaping of parts by removing material (involves roughing, finishing operation). E.g.: Cutting, Shaping, Planning, Slotting, Broaching, Milling, Grinding, Hobbing, etc.
Forming Methods for Gear Manufacturing
Following are the methods for forming gears:
Sand Casting ↠ cast tooth are produced by melting and pouring into the mold cavity.
Die Casting ↠ casted tooth are produced by injecting material into mold cavity using high pressure.
Rolling ↠ deformation process in which thickness is reduced by compression forces exerted by two opposing rolls.
Powder Metallurgy ↠ pressing of metal powder in dies final shape.
Injection Molding ↠ producing teeth by injecting molten material into a mold.
Cold Drawing ↠ forming teeth from steel rods by drawing (pulling) them through hardened dies.
Extrusion ↠ shaping of teeth by pushing rod through a die having gear shape.
Stamping ↠ a cutting process in which sheet metal is placed between portions of die which removes the gear from the sheet.
Forging ↠ material shaping process by the application of localized compressive forces with power hammers, presses.
Machining Methods for Gear Manufacturing
Gears are manufactured in several routes:
Blanks are performed through machining, finishing and then teeth are produced.
Full Gears with teeth are made by different processes and then finished by further machining and grinding.
Accurate gears in finished form are directly produced by Near-Net-Shape process like rolling, plastic molding, powder metallurgy.
Machining methods for gear manufacturing are:
Forming (or Form-Cutting or Copying or Profiling Method) ↠ teeth profiles is obtained as the replica of the form of cutting tool (milling, shear cutting, teeth cutting).
Generation ↠ complicated tooth profile is provided by much simpler form cutting tool (edges) through rolling type, tool-work motion (Hobbing, gear shaping).
Hydrographic Survey Hydrography is the science which determines the physical features and the navigable portions of the Earth's surface adjoining coastal areas. Surveyors study bodies of water to see what the floor looks like. Techniques and Instruments used in Hydrographic Survey : Many instruments are used in hydrographic survey like multibeam sonars, LIDAR, multibeam echo sounders(MBES), global positioning system (GPS), laser scanners etc. Among these instruments some are discussed ahead which are mostly used. 1. Light Detection and Ranging: LIDAR is used to measure the elevation or the depths of water bodies by analyzing the reflection of laser light off an object or seafloor. Bathymetric LIDAR is used to determine is used to determine the depths of water bodies by measuring the time delay between the pulse of transmission and its return signals. 2.Multibeam Sonars: Multibeam echo sounders(MBES) or sonar systems transmit sound energy which strike seafloor a
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
Rankine Cycle Rankine cycle is an ideal cycle for Vapour Power Cycles and is normally used for Electricity Generation. The Rankine cycle consist of following steps: 1 ↝ 2 : Isentropic Compression in Pump. 2 ↝ 3 : Constant Pressure Heat Addition in Boiler. 3 ↝ 4 : IsentropicExpansion in Turbine. 4 ↝ 1 : Constant Pressure Heat Rejection in Condenser. Energy Balance: Since, all the devices which Rankine Cycle posses are steady flow devices, so the energy balance for Rankine cycle is: 》For Pump ( q = 0 ): 》For Boiler ( w = 0 ): 》For Turbine ( q = 0 ): 》For condenser ( w = 0 ): The thermal efficiency of Rankine Cycle is: How can we Increase the Efficiency of A Rankine Cycle: The efficiency of a Rankine cycle can be increased: Increasing the avg. temperate at which heat is added Decreasing the avg. Temperature at which heat is rejected. The above two objectives can be achieved by following three methods: 1. By
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