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 obtains its power by utilizing the energy of burnt gases and air which is at high temp and pressure by expanding through the several ring of fixed and moving blades.
It is similar to Steam Turbine but it uses Gas instead of Steam.
Turbine drives the compressor (as they are coupled to each other by a shaft).
Compressor absorbs power produced by turbine (lowers efficiency).
Compressor utilizes 40-45% of total power produced by Turbine.
A simple gas turbine cycle consists of:
Compressor
Combustion Chamber
Turbine
Steps:
Inlet (air comes in) → Compressed to a very high pressure (by compressor, Cpair) → which goes to combustion chamber where it burns (Cpgas) → produce combustion gases → hit turbine blades → it starts rotating → electricity produce → flue gases leaves the gas turbine.
Limitations:
When burning not started, compressor is run by an external source.
Small size, mass and initial cost per unit output.
Quick starting (as low as 10 Seconds) or Remote Control.
It uses variety of liquids/gases fuels including gasified coal, synthesis fuels.
Disadvantages:
Large compressor work input.
Brayton Cycle
It is the Ideal cycle for Gas Turbine Engines.
Notes:
Common design, pressure ratio of gas turbines (rp) ranges from 11 to 16.
In gas turbine powerplants, "Ratio of Compressor Work to Turbine Work is called Back Work Ratio" is very high.
Mostly,
Compressor Work Output = 0.5 x Turbine Work Output
Types of Gas Turbines
Open Cycle Gas Turbine → No Condenser (Cooler/Heat Exchanger), less efficient, greater emissions.
Closed Cycle Gas Turbine → Have Condenser.
Combined Cycle Power Plant
It couples two power cycles such that the energy discharged by heat transfer from one cycle is used partly as the input for the other cycle.
Temperature in a dry bottom cycle does not exceed 600℃ (Exit Boiler Temp).
High thermal irreversibility and a decrease in availability because of heat transfer from combustion gases to steam through such a large temp difference.
Types of Combined Cycle Power Plant
Gas Turbine-Steam Turbine Power Plant (GT-ST Power Plant)
Gas Turbine-Stirling Engine Power Plant
Diesel-Steam Turbine Power Plant (mostly in Textile Industry)
GT-ST Combined Cycle Power Plant With Supplementary Fuel Combustion
Major components used in GT-ST Power Plant:
Gas Turbine
Heat Recovery Steam Generator (HRSG)
Steam Turbine
Brayton Cycle is at the Top (High temp gas turbine power plant) while Rankine Cycle is at the bottom (Lower temp steam turbine power plant).
Steam Turbine utilizes the energy from the gas turbine exhaust as its input.
If temperature of the exhaust gas from GT is not up to mark (for desired power output), we use combustion chamber called Supplementary Combustion of Fuel.
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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