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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Engine Cycles
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Air-Standard Cycle Assumptions:
The actual cycle is rather more complicated so we deduce it by considering following assumptions:
The working fluid is air which continuously flow in a closed loop and act as ideal gas.
Combustion process is replaced by Heat addition process.
Exhaust process is replaced by Heat rejection process.
Here we are discussing 4 main cycles, namely:
Otto Cycle or Constant Volume Heat Addition Cycle
Diesel Cycle or Constant Pressure Heat Addition Cycle
Dual Cycle
Brayton Cycle
1. Otto Cycle or Constant Volume Heat Addition Cycle:
The information about the diagram is given by:
1 ➤ 2: Isentropic Compression
2 ➤ 3: Constant Volume Heat Addition
3 ➤ 4: Isentropic Expansion
4 ➤ 1: Constant Volume Heat Rejection
A. Efficiency of Otto Cycle:
The efficiency of Otto Cycle is given by clicking the picture below:
B. Work Output of Otto Cycle:
The work output of Otto Cycle is given by:
C. Mean Effective Pressure:
The ratio of Work Output to the change in volume of the cylinder that means swept volume is called Mean Effective Pressure. MEP of Otto Cycle is given by:
2. Diesel Cycle or Constant Pressure Heat Addition Cycle:
The figure shows:
1 ➤ 2: Isentropic Compression
2 ➤ 3: Constant Pressure Heat Addition
3 ➤ 4: Isentropic Expansion
4 ➤ 1: Constant Volume Heat Rejection
A. Efficiency of Diesel Cycle:
The efficiency of Otto Cycle is given by clicking the picture below:
B. Work Output of Diesel Cycle:
The work output is given by:
C. Mean Effective Pressure:
Mean Effective Pressure is the ratio of work output to the swept volume. The mean effective pressure is given by:
3. Dual Cycle or Mixed Cycle:
The figure shows:
1 ➤ 2: Isentropic Compression
2 ➤ 3: Constant Volume Heat Addition
3 ➤ 4: Constant Pressure Heat Addition
4 ➤ 5: Isentropic Expansion
5 ➤ 1: Constant Volume Heat Rejection
A. Efficiency of Dual Cycle:
Efficiency is the ratio of work output and the heat input. Thermal efficiency of Dual Cycle is given by:
B. Work Output:
Work Output for Dual Cycle or Mixed Cycle is given by:
C. Mean Effective Pressure:
It is the ratio of work output to the change in volume that is swept volume. The mean effective pressure is given by:
Comparison Of Cycles (Otto, Diesel & Dual):
1. Same Compression Ratio & Heat Addition:
Since, Qout (4 → 1) in Otto Cycle is lesser than Qout (4' → 1) in diesel cycle, therefore
ηotto > ηdual > ηdiesel
2. Same Compression Ratio & Heat Rejection:
Since, Qin (2 → 3) in Otto Cycle is greater than Qin (2 → 3') in diesel cycle, therefore
ηotto > ηdual > ηdiesel
3. Same Peak Pressure, Peak Temperature & Heat Rejection:
Since, Qin (2 → 3) in Otto Cycle is lesser than Qin (2 → 3') in diesel cycle, therefore
ηotto < ηdual < ηdiesel
4. Same Maximum Pressure & Heat Input:
Since, Qout (4 → 1) in Otto Cycle is greater than Qout (4' → 1) in diesel cycle, therefore
ηotto < ηdual < ηdiesel
5. Same Maximum Pressure & Work Output:
Since, Qout (4 → 1) in Otto Cycle is greater than Qout (4' → 1) in diesel cycle, therefore
ηotto < ηdual < ηdiesel
4. Brayton Cycle:
The figure shows:
1 ➤ 2: Isentropic Compression
2 ➤ 3: Constant Pressure Heat Addition
3 ➤ 4: Isentropic Expansion
4 ➤ 1: Constant Pressure Heat Rejection
Brayton cycle is completely explained in the video given below:
Efficiency of Brayton Cycle:
Efficiency is the ratio of work output to the heat input. The efficiency of Brayton Cycle is given by:
Brayton Cycle with Regeneration:
The exhaust gas leaving the turbine (state 4) is higher than the temperature of the gas leaving the compressor.
Therefore heat can be transferred from the exhaust gases to the high pressure gas leaving the compressor using a Counter-Flow Heat Exchanger called Regenerator.
The extent to which regenerator reaches an ideal regenerator is called the Effectiveness ϵ, which is given by:
When cold-air standard assumptions are utilized, it reduces to
The question is if there is no ideal condition that means no isentropic condition. So do why we use isentropic conditions while dealing with these IC engine cycles?
If we deal IC engine cycles without any condition then it is hard to analyze problems because if we don't have IC engine cycles then how we calculate power to be produced by car, work done to overcome friction, fuel to be injected to produce normal engine operations, selection of cooling pump? On the other hand, if we use Isentropic condition for analysis of engine cycles, then it is easier to calculate power, work done and other more. Hope I can make you understand the basic concept.
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...
Solid Mechanics OR Mechanics of Materials OR Strength of Materials: It is the study of mechanics of body i.e. forces and their effects on deformable solids under different loading conditions. Deformable Body Mechanics: It is the study of non-rigid solid structures which deform under load. Deformation/Distortion ⇾ change of shape and size OR have some relative displacement or rotation of particles. It happens when we apply combined load. Rigid Body Motion ⇾ Translation or rotation of particles but having constant distance between particles. Since deformation occur at particular load. Below this load, every body is considered as rigid body . Types of Load: Point Load ⇾ Load apply on a single point i.e. concentrated load. Uniformly Distributed Load (UDL) ⇾ Load remains uniform throughout an area of element like beam. Varying Distributed Load (VDL) ⇾ Load varies with length with constant rate. Moment ⇾ It measures the tend...
Strain Transformation Principal Strain and stresses can occur in the same directions. Material Properties Relation (Young, bulk Rigidity Modulus) ⇼ Hooke's Law General State of Strain ⇼ Є X , Є Y , Є Z and ૪ X , ૪ Y , ૪ Z . Stress (normal or shear)/ Strain (normal or shear) ⇼ vary with element orientation. Transformation equations for Plane strain derived from: Interpretation of Experimental measurements Represent in graphical form for plane strain (Mohr's Circle). Geometry and independent of material properties. Mohr's Circle It is defined as., " A graphical method for determining normal and shear Shear stresses without using the stress transformation equations " . While considering the circle CCW ⇼ Shear strain positive upward & Normal strain positive towards right. The construction of Mohr's circle (with normal and shear stresses are known) is quite easy which include following steps: Draw a set o...
The question is if there is no ideal condition that means no isentropic condition. So do why we use isentropic conditions while dealing with these IC engine cycles?
ReplyDeleteIf we deal IC engine cycles without any condition then it is hard to analyze problems because if we don't have IC engine cycles then how we calculate power to be produced by car, work done to overcome friction, fuel to be injected to produce normal engine operations, selection of cooling pump?
DeleteOn the other hand, if we use Isentropic condition for analysis of engine cycles, then it is easier to calculate power, work done and other more.
Hope I can make you understand the basic concept.