Відео

N is an angle parameter in the calculation of the equation of time (EOT). See Equation 7-4 of the textbook Heating, Ventilating, and Air Conditioning Analysis and Design, 6th Ed., by McQuiston, et al.

@@bing9u0 Thank you

Thank you for catching the typo. It should be "additional process(es)". Example: An ideal gas system can undergo an isentropic compression process to reach a new state. Then from the new state, the system could further undergo an isochoric heat addition process, an isentropic expansion process and finally an isochoric heat rejection process to return to the initial state. By now the system would have completed an Otto cycle.

@@bing9u0 Thank you very much sir for clarification and such comprehensive explanation.🙏🏼😊

Star can+ if I recall correctly

That is a very technical question and the answer depends on the CFD program that you use. Even if you use the same product that I used, the product might have evolved so that options may no longer available. I am afraid you will have to figure that out on you own.

@@bing9u0 Many thanks for your quick reply. yes I am using STAR CCM+, but seems that it has been changing from the version you used. Also I have another question regarding the video , you mentioned that if we have already the simulated flow field we have to freeze solver setting related to the flow. so we have to freeze the flow as well? or I am misunderstood you

I believe it is this: Heating, Ventilating, and Air Conditioning: Analysis and Design, 6th Edition Faye C. McQuiston, Jerald D. Parker, Jeffrey D. Spitler ISBN: 978-0-471-47015-1

Yes, Indeed great video! he won't share I believe

@@abhijeetsingh5143 what a jew

Grateful for cc now because I have hearing difficulty. 🦻🏻

You still need help?

@@Kurosaka can you please help me

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Inta I'd plz

For all practical purposes, we consider the gas system to be under quasi equilibrium if the expansion or compression is slow comparing to the speed of sound in the gas. When the system is expanding or being compressed, strictly speaking it is not in equilibrium. However, if the system's boundary (such as the inside surface of the piston) moves much slower than the speed of sound, the deviation of the system from equilibrium is very small, and the system is in quasi equilibrium.

@@bing9u0 Thanks for your response. I thought I understand this but now I feel like I dont, this concept is so confusing. Back to the expansion of the combustion gas inside the cylinder, how is the system still remained in equilibrium when there is chemical reactions occurs throughout the process? This is what I learned: A Quasiequalibrium process is, first of all, a thermodynamic equilibrium ( satisfy all these: thermal equilibrium, mechanical equilibrium and chemical equalibrium). I would guess that the system satisfy the first two( thermal and mechanical equilibrium), but why chemical equilibrium? Isn't the gas combustion is chemical reactions?

@@Kay-dx8vm In the context of a typical thermodynamics course offered to Mechanical Engineering students, the chemical reactions in an internal combustion engine are not considered in detail. Instead, the reactions, which lead to the release of chemical energy, are modeled as a heat addition process. Further, the "heat addition" process is typically modeled as either an instantaneous (and hence isochoric) process for the Otto cycle or a constant-pressure process for the Diesel cycle.

@@bing9u0 I see, that makes sense. Thank you so much for your help

Generally yes. The higher the isentropic efficiency of a compressor, the less work it consumes to achieve the same compression outcome.

@@bing9u0 but what if my isentropic efficiency is high, but my coefficient of performance is low?

@@wt3377lyn I assume you are referring to the isentropic efficiency of a compressor in a vapor compression refrigeration cycle. The compressor's isentropic efficiency does affect the COP of the cycle. However, the temperatures of the hot reservoir and the cold reservoir also affect the COP. Begin with a "perfect" compressor that has 100% isentropic efficiency, and see what the COP of a cycle is; then study the case where compressor isentropic efficiency is less than 100% (the cycle will be different than first case even if you keep the lower and upper pressure limits constant). Your professor or a good tutor should be able to help you do this comparison with an example problem.

@@bing9u0 thank you

Thank you! Comments like yours keep me going.

When we talk about equilibrium or quasi-equilibrium in thermodynamics, we are talking about a system - a system being in equilibrium or quasi-equilibrium. As for the piston you referred to, it typically appears as part of a piston-cylinder enclosure, which contains some gas that you can add heat to or remove heat from. In this case, the gas is the SYSTEM. The piston and the cylinder are the surroundings of the system (the gas). Assuming no leakage between the piston and the cylinder, the gas is a closed system, which can be involved in doing boundary work or receiving boundary work (and possibly heat addition or removal), as the piston moves. In most engineering applications, the gas (the system) can be considered in quasi-equilibrium. If the system is in quasi-equilibrium when it undergoes a process, that process is also called quasi-equilibrium or quasi-static process.