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.
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...
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...
Moving Boundary Work: The expansion and compression work associated with a piston cylinder device in which boundary moves is called Moving Boundary Work. Area under the Process curve on a PV Diagram: From the above figure, the differential area is the product of pressure and differential volume. So the area under the Process curve is given by: The area under the Process cure on a PV Diagram is Moving Boundary Work. Moving Boundary Work in A constant Volume Process: Moving boundary work is given by: Moving Boundary Work for a Constant Pressure Process: Moving Boundary Work is given by: Moving Boundary Work for an Isothermal Process: A thermodynamic process in which temperature remains constant durine the heat transfer is called Isothermal Process. Moving Boundary Work is given by: Where; PV = mRT If temperature is constant,then PV = c P = c/V Moving Boundary Work for P...
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