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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Introduction and Basic Concepts about Thermodynamics
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THERMODYNAMICS
Thermodynamics actually includes all aspects of energy, energy transformation and relationship among the properties of matter.
Applications of Thermodynamics:
There are many applications of thermodynamics bit some of them are :
1. Human body
2. Refrigeration system
3. Air-conditioning system
4. Aeroplanes
5. Power Plants
6. Automobiles, etc.
SYSTEM AND CONTROL VOLUME:
System is any thing which is under consideration.
Volume of system or under boundary is called control volume.
TYPES OF SYSTEM:
1. OPEN SYSTEM:
System through which mass and energy can cross the boundary is called open system.
2. CLOSE SYSTEM:
System through which energy can transfer but mass cannot cross the boundary.
3. ISOLATED SYSTEM:
System through which mass and energy cannot transfer.
PROPERTIES OF A SYSTEM :
Any characteristic of a system defines property of a system. They are divided into several types:
1. INTENSIVE PROPERTIES:
Properties which does not depend upon the size and quantity of system. For exaqmple: temperature, pressure, density, etc.
2. EXTENSIVE PROPERTIES:
Properties which does depend upon the size and quantity of system. For example: mass, volume, mole, etc.
3. SPECIFIC PROPERTIES:
It is defined as;
Extensive properties per unit mass.
For example:
1. specific volume = volume / mass
2. Specific energy = energy / mass
3. Specfic weight = weight / volume, etc.
CONTINUUM APPROACH:
Consideration of continuity of matter that there are no holes between molecules is called Continuum Approach.
Note: At high altitudes, mean free path becomes much greater so continuum approach is not applicable. For this Rare-fied Gas Flow Theory is used.
RELATIVE DENSITY or SPECIFIC GRAVITY:
Density of solids relative to standard liquid's density that is water.
Specific Gravity = S.G. = Density of substance/Density of water
STATE OF A SYSTEM:
If a system is in equilibrium, then properties give the state of a system.
EQUILIBRIUM:
It imlpies the state of balance. A system ion equilibrium rxperiences no change.
For example:
* Thermal equilibrium: No change in temperature.
*Mechanical equilibrium: No change in pressure.
*Chemical equilibrium: No change in composition.
THE STATE POSTULATE:
It states that;
The state of a simple compressible system is completely specified by two independent intensive properties.
SIMPLE COMPRESSIBLE SYSTEM:
A system in the absence of electrical, mechanical, gravitational motion and surface tension effects is called Simple Compressible System.
PROCESS AND CYCLES:
Process is defined as;
Any change that a system undergoes from one equilibrium state to another.
Cycle is defined as;
If a system returns to its initial state at the end of the process.
QAUSI-EQUILIBRIUM PROCESS OR QUASI-STATIC:
When a process proceeds in such a manner that the system remains infinitesimally close to an equilibrium state at all times is called Quasi-equilibrium process.
ZEROTH LAW OF THERMODYNAMICS:
It states that;
If two bodies are in thermal equilibrium with the third body then they are also in thermal equilibrium with each other.
Principle Of Linear Impulse And Momentum : The basis of principle of linear impulse and momentum is given by: The above equation can be written as: The above equation is called Principle of Linear and Momentum. Impulse measures the effect of force during small time period 'dt'. Momentum (is the strength of motion ) is associated with the states of process. Impulse are associated with process caused by external force. For System Of Particles: For system of particles, the principle of linear impulse and momentum is written as the summation for number of particles: Here, Individual Particle Velocity (Vi) = Velocity of center of mass (Vg). Summation Of individual particle (mi) = Total mass of body (m). Conservation Of Linear Momentum For System Of Particles : If the sum of external impulse of the system of particles is zero, then Principle of linear momentum and impulse becomes: There are two types of force on the basis of Impulse whic
Cotter Joints A temporary fastener used to connect rigidly two co-axial rods (or bars) which are subjected to axial tensile or compressive forces. Cotter ↣ A flat wedge shaped piece of rectangular cross-section of uniform thickness and its width is tapered for an easy adjustment.It is made of steel . Used in connecting piston rod to cross-head of reciprocating steam engine. Inserted ⊥ to the axis of shaft. Strength of key < Cotter strength ↣ because of removing material . We add taper on top of key while we add taper on top, bottom but along width side of cotter. Types of Cotter Joint 1. Sleeve and Cotter Joints Simplest of all cotter joints and is used to fasten two round rods/bars . Rectangular cross-section area, tapered both sides along width. We add cotter pin ⊥ to the axis of shaft and add sleeve to shaft and then add pin. It has better strength than Socket and Spigot Cotter joint . Taper in cotter is 1 in 24 . 2. Gib and Cotter Joints It is used to join two square rod
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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