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 is defined as, "a passage through which heat energy of steam is converted to kinetic energy by producing a high velocity jet of steam which is used to drive a steam turbine".
Nozzle ↣ Increase velocity at the expense of pressure drop.
Throat ↣ Produce steam jet with high velocity to drive steam turbine.
Types of Nozzles:
Convergent Nozzle ↣ Cross-section decreases continuously from entrance to exit.
Divergent Nozzle ↣ Cross-section increases continuously from entrance to exit.
Convergent-Divergent Nozzle ↣ Cross-section first decreases from entrance to throat, then increase from its throat to exit.
Stagnation State
For a high speed flows (in jet engines), P.e. is negligible but K.e. is not. It is convenient t combine enthalpy and K.e. of the fluid into a single term called Stagnation or Total Enthalpy.
ho = h + 0.5 V^2
Total or Stagnation State ↣ state in which flow is brought to rest isentropically in steady flow, zero adiabatic work output.
Dynamic Temperature ↣ temperature change when molecules are moving.
Velocity of Sound & Mach Number
Sound wave is defined as, "a small pressure disturbance that propagates through a states (gas, liquid, solid)".
Velocity of wave depends on properties of the medium.
Mach Number ↣ the ratio of actual velocity and the velocity of sound.
If M < 1 ↣ Subsonic Flow.
If M = 1 ↣ Sonic Flow.
If M > 1 ↣ Supersonic Flow.
Variation of Fluid Velocity with Flow Area
The last equation concludes that:
Stagnation Property Relations (Critical Pressure Ratio & Choked Flow)
Effect of Back Pressure in Convergent Nozzle
Back Pressure is defined as, "the pressure applied at the nozzle discharge region".
Condition of Flow ↣ pressure difference between inlet and outlet.
Choked Flow ↣ when nozzle operates with maximum mass flow (done by reducing back Pressure to critical pressure).
Critical Pressure ↣ pressure of fluid at a location in the nozzle where M=1 (at throat).
Center of Gravity: It is defined as; The resultant weight of a system which passes through a single point is called Center of Gravity ( G ). Center of Mass: It is defined as; The point at which the whole mass of the system acts. The concept of center of mass is cleared from the video given below: Centroid of a Volume: Objects having three dimensions have the centroid which is its geometric centre. Centroid of an Area: Objects having two dimensions have the centroid which is its geometric centre. Centroid of a Line: Objects having linear dimensions have the centroid which is its geometric centre. Composite Bodies: A composite body consists of a series of connected simpler shaped Bodies which may be rectangular, triangular, semicircular, etc. References: www.youtube.com www.wikipedia.com http://web.aeromech.usyd.edu.au/statics/doc/friction/Friction1.htm From Book Engineering Mechanics sta...
Flywheel It is defined as, " a machine element which serves as reservoir which stores energy during the period when energy supply is more than the requirement and releases it when energy is less than requirement " . Used in IC, reciprocating (compressors or pumps) engines, presses, etc. Excess energy is stored in flywheel and release to crankshaft during other strokes in which no energy is developed. If space is small ↠ use small diameter and solid flywheel . If space is not limited (like for presses, crushing machine, hammering machine) ↠ use large diameter and hollow flywheel . Purpose of flywheel is to: reduce amplitude of speed fluctuation (sinusoidal) for constant power output. reduce maximum torque required. energy stored and release when needed during cycle. Parts of flywheel are Rim ↠ outer portion of flywheel (which is like a wheel). Hub ↠ center part which is installed on shaft. Arms or Needle ↠ rods joining rim to ...
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...
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