Author: haroonkhan
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Stefan–Boltzmann Law of Thermal Radiation
The law states that the rate of radiation heat transfer per unit area from a black surface is directly proportional to fourth power of the absolute temperature of the surface and is given by, where Ts is absolute temperature in K; and σ is proportionality constant and called as Stefan–Boltzman constant equal to 5.67 × 10− 8 W/m2K4. The heat…
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Stefan–Boltzmann Law of Thermal Radiation
The law states that the rate of radiation heat transfer per unit area from a black surface is directly proportional to fourth power of the absolute temperature of the surface and is given by, where Ts is absolute temperature in K; and σ is proportionality constant and called as Stefan–Boltzman constant equal to 5.67 × 10− 8 W/m2K4. The heat…
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Radiation
All matter continuously radiates electromagnetic radiation unless its temperature is absolute zero. It is observed that the higher the temperature then the greater amount of energy is radiated. If two bodies at different temperatures are so placed that the radiation from each body is intercepted by the other, then the body at the lower temperature…
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Convection
Convection is the term used for heat transfer mechanism which takes place in a fluid because of a combination of conduction due to the molecular interactions and energy transport due to the macroscopic motion of the fluid itself. In the above definition, the motion of the fluid is essential otherwise the heat transfer mechanism becomes…
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Conduction
Conduction is the heat transfer from one part of a substance to another part of the same substance, or from one substance to another in physical contact with it, without appreciable displacement of the molecules forming the substance. On the elementary particle level, the conduction is visualized as the exchange of kinetic energy between the…
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INTRODUCTION
This deals with different modes of heat transfer which are usually classified as conduction, convection and radiation. From the second law of thermodynamics, we know that the heat flows whenever there is existence of temperature difference or temperature gradient. Heat is a form of energy which is transferred from one body to another body at…
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ENGINE PERFORMANCE PARAMETERS
There are several parameters to indicate the performance of an IC engine, for example, indicated thermal efficiency (ηith), brake thermal efficiency (ηbth), mechanical efficiency (ηmech), volumetric efficiency (ηv), relative efficiency of efficiency ratio (ηrel), mean effective pressure (Pm), mean piston speed (Sp), specific power output (Ps), specific fuel consumption (sfc), and air fuel ratio (A/F).…
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DUAL CYCLE
For same compression ratio, Otto cycle is more efficient but delivers less power than the diesel cycle. Therefore, in dual cycle partly heat is added at constant volume and partly at constant pressure as shown in Figure 6.17. Figure 6.17 ρ−V and T−s Diagrams for Dual Cycle Example 6.6: An air standard dual cycle has a compression ratio of 18 and…
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DIESEL CYCLE
In a diesel cycle, heat is added at constant pressure and rejected at constant volume as shown in Figure 6.16. During heat addition, to maintain the constant pressure piston starts to move towards BDC. At point 3, injection is stopped which is known as cut-off point. Figure 6.16 Indicator Diagrams for Diesel Cycle Putting the value of T2, T3 and T4 in the…
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OTTO CYCLE
In Figure 6.15, ideal P−V, actual P−V, and T−s diagrams are shown. There are some basic differences in ideal and actual indicator diagrams as valves do not open or close at sharp points practically. Valves start to open just before the point and close just after the points as shown in Figure 6.15b. The process 0−1 shows the suction of the charge…