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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Fluidized Bed Combustion Technology
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Fluidized Bed Combustion Technology
Fluidized bed combustion (FBC) is defined as, "a combustion technology used to burn solid or low grade fuels".
Fuel particles are suspended in a hot bed of particulate materials (like ash, sand, limestone).
Since this allows coal plants to burn at cooler temperatures, less NOx is also emitted.
We have large coal reservoirs but it has high Sulphur content ↣ to deal with this issue, we have Fluidized Bed Combustion Technology.
This technology is used because:
Sulphur emission decreases by Lime.
NOx emission decreases by decrease in temperature.
Circulating Type Fluidized Bed Boiler
It is defined as, "a boiler which works on the fluidized bed combustion technology for producing heat". There are two types of Circulating Type Fluidized Bed (CFB) Boiler:
Circulating Type ↣ Particle velocity ranges between 5 - 10 m/s.
Bubbling Type ↣ Particle velocity ranges between 1 - 3 m/s.
Construction
Bed Drain Tube ↣ used to remove ash.
Grid Plate ↣ where combustion occurs.
Submerged Tube Bank ↣ for producing steam.
Plenum Chamber ↣ used for storing air.
Working
Air from fan enters furnace↣ pass through bed of finely divided particles (sand) ↣ air velocity increases, sand particles vibrate (which heat air)↣ desired fuel is added (first secondary then primary fuel is added) ↣ when self sustained temperature of coal is added, we cut primary fuel ↣ then coal is added ↣ initial combustion starts ↣ unburned coal particles leaves furnace ↣ Primary cyclone capturing then back into furnace.
Loop Seals ↣ maintains the pressure balance between the furnace and exit of the separators allowing the solid to flow back into the furnace.
High Performance particle steam heat exchanger ↣ Interax which extracts high temperature heat from hot particles in CFB to produce high temperature superheated steam.
Ques: What does fluidized means?
Ans: When air (or gas) is passed through finely divided bed of solid particles (sand), the particle remain undisturbed at low velocity. As velocity increase, particles start to vibrate remain suspended in air stream.
Fluidized combustion ↣ (840 - 950)℃ much lower than ash fusion temperature, ash and NOx reduces.
Ash can be used as Cement Raw Material.
Advantages
Very low quality fuel is used. Like coal, biomass, tyres).
Coal is used in coarse phase (not in powdered form).
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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