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).
Reynolds Number: Reynolds Number is the ratio of Inertial forces to the Viscous forces. By knowing this number, one can describe the flow whether the flow is laminar, turbulent or transitional flow. There are three possibilities of the range of Reynolds Number: If Reynolds number < 2100 or 2300 ⟺ Laminar Flow If Reynolds number > 4000 ⟺ Turbulent Flow If 2300 < Reynolds number < 4000 ⟺ Transitional Flow In case of different shapes other than circle, the formula for Reynolds Number remain the same however diameter involves in the formula become Hydraulic Diameter which is given by: For pipe: Critical Reynolds Number ⟾ The Reynolds number at which the flow becomes turbulent Re cr For different shapes, the hydraulic diameters are given by: Completely Filled Flow In Closed Channel: If pipe is is considered to filled completely with closed channel, then following are the conditions which...
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 ).
Mechanical Injection System: Used to inject fuel into the combustion chamber. Fuel speed > air speed at delivery point to atomize fuel. Amount of fuel delivered into the air stream going into the engine is controlled by pump which forces the fuel under pressure. A device used to initiate and control the combustion process is called Mechanical Injection System. Functional Requirements of Injection System: Metering of Fuel: Used to control fuel to meet speed and load requirements of the engine. Injection Timing: Have proper injection timing to obtain max. power, fuel economy and proper burning. It is done by Camshaft or Push rod (Rocker Arm) Mechanism . Proper Control of Injection Rate: To get desired heat release pattern during combustion. Proper Atomization of Fuel: Proper making of droplets to make best Air/Fuel mixture. Proper Spray Pattern: Distribution of droplets to ensure rapid mixing of fuel & air. Uniform Distribut...
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