FAQ 1.1: Hello sir, my first assumption was exergy is from wasted energy turned into useful energy. But exergy is extracted from useful energy. If that useful energy is used to.. say, make the tyres turn, then the thing that is making the tyres turn is exergy. Is useful energy all along exergy and we only know it now? And wasted energy is totally lost? Cannot be recovered anymore?
FAQ 1.2: My question is related to Example 1.2. if the question given 2 different unit for temperature, celsius and Kalvin. which unit we have to use?
ANS: You need to choose one..depend on the equation that you are used in your solution. In the same equation..let say for the temperature unit..the unit must be the same. Otherwise your calculation is wrong.
FAQ 1.3: I want to ask about the formula for exergy of PE and KE. Which is there are two types of formula Xpe = PE = mgz (kj) and xpe = pe = gz (kj/kg). when we need to used the exergy, X in capital letter and in small letter?
ANS: Depend on the problem...if the problem state the specific unit...you have to choose one of them based on its unit. If the problem does not specific any unit, you can choose either one. The term of capital letter X is refer as exergy (kJ). The term for small letter x is refer as specific exergy or exergy per unit mass (kJ/kg).
FAQ 1.4: What is the different between X in capital letter and small capital letter, and when it is need to use it?
ANS: The difference is the term/terminology or Unit used for X or x. Please refer my previous response above.
FAQ 1.5: Exergy is the maximum useful energy required for an operation. Therefore energy loss or heat loss are not categorised to exergy basically. All heat engine systems would have heat loss or other external waste energy, therefore efficiency is important to determine whether how much heat energy required to produce the useful work. Based on second law of thermodynamics, since not all heat energy can produce work, therefore assumption of useful work should be calculated correctly based on heat source, surrounding temperature, temperature sink. Input temperature will reduce as output temperature for producing work and due to heat loss also.
ANS: I agree with you except your last statement "Input temperature will reduce as output temperature for producing work and due to heat loss also." It depend on the system condition. Most probably the heat loss will effect the output temperature rather than the input temperature. However there are many factors need to be considered. Later, perhaps in difference chapter your understanding will increase about this matter.
FAQ 1.6: Exergy is the ideal energy extracted from energy source whereas in actual case losses will be present due to factors such as heat loss. As for a heater that functions to convert electrical energy to heat, does it has any losses? And why?
ANS: Similar principle apply to the heater. The heater is under the heat pump categories not a heat engine. Heater system must follow the thermodynamics law. The heater must absorb heat and release heat. In actual system, heat loss may occur due to imperfect condition of the system. That why certain part in the heater we can find an insulator in order to minimize the heat loss to surrounding. More heat loss..that mean your heater will be less efficient.
FAQ 1.7: I want to confirm answer for example 1.1...i calculate the value is different.
ANS: Please remind me during our live discussion this week (Week 2). We will look and check if there are any mistakes in my solution. I think I miss decimal point for the air density suppose 1.225 and not 1225. Probably you will obtain slightly higher m dot value..if not mistaken..equal to...1385 kg/s.
FAQ 1.8: Salam Dr. Can explain briefly regarding exothermic and endothermic process. Tq
ANS: For simple explaination....exothermic .....releases energy into the surrounding of the system. However ..endothermic .....absorb energy from the surrounding of the system.
FAQ 1.9: Hi Dr I wonder how many is the accepted efficiency of work is usually accepted by the industrial to prevent excessive wastage?
ANS: The acceptable efficiency depend on the system design. For example in actual power plant..currently the efficiency only 30-40% only. Although the efficiency is low...but it acceptable for our current condition. Increase the effeciency more than that..we cause other effect...such as..the increase of operating cost...component cost and maintenance cost. There are few aspect that we need to consider for acceptable value of efficiency for the industrial system..such as.. current technology available...available component in the market...operating cost.....maintanent process.....consumer capability..and so on...
FAQ 1.10: sir, is it the high temperature for any process of heat energy will affect the heat loss? and how to make sure the efficiency of the work are still in good condition?
ANS: It depend, the amount of heat loss are depend on the system. Less effective or poor design system will cause big amount of heat losses. Main factor of the heat losses is not come from the higher temperature of the heat source. Actually if we increase the heat source temperature of a system is one of the way to increase the system efficiency. In order to maintain the efficiency..we need to make analysis and figure out during the process of any heat engine...whether is there any reduction of efficiency. If there any reduction occur. As an engineer..you have to identify the problem...which part cause losses...than fix it. For example...certain piping line...the insulation are missing or damaged...heat loss will occur...then fix it by replacing with the new one...with better insulation properties.
FAQ 1.11: What is the example or related system of exergy in the real life?
ANS: The exergy is consider as the maximum capability of a system. Like an imaginary value of max. energy that can be achieve to produce useful work. This value use as a guide to know the condition of any system with the maximum one. This properties is important in design process and so on. If we can develop a system that is very close to the exergy value..it mean that we already create a system that is almost perfect.
FAQ 1.12: Why is exergy important? And what is example for exergy in real life ?
ANS: The exergy is consider as the maximum capability of a system. Like an imaginary value of max. energy that can be achieve to produce useful work. This value use as a guide to know the condition of any system with the maximum one. This properties is important in design process and so on. If we can develop a system that is very close to the exergy value..it mean that we already create a system that is almost perfect.
FAQ 1.13: In example 1.2, why do we need to use the nth = W dot net / Q dot in formula
ANS: for the formula it depend on data given in the question. You also can use W/Q....w/q..or Wdot/Qdot..the most important is..both parameter must have the same unit. Because the units will be cancelled out during the calculation.
FAQ 1.14: Salam Dr, in example 1.2, for the formula nth, rev that involve Tout/Tin, why do we need to minus 1?
ANS: You have to look at the original equation of the thermal efficiency...where nth =wnet/qin = (qin-qout)/qin = 1- (qin/qout)...when analyse the area under the curve for reversible cycle (Carnot)...the term of (qin/qout) will change to (TL/TH)..or Tin/Tout for this case.
FAQ 1.15: For example question if the question give unit for temperature, celsius , we must convert to Kelvin or can use in celsius too ?
ANS: Depend on the equation that you use. Normally for the equation involve with ideal gas ...the equation will use Kelvin for temprerature unit....because Kelvin is the SI unit for temperature.
FAQ 1.16: For case 1 and case 2 in note, is it just for compare which one is exergy?
ANS: Yup... just to show an analogy in order to describe or explain the concept of exergy for mechanical energy or system and also for heat energy or system.
FAQ 1.17: For the heat energy, according to Thermodynamic Law 2, heat energy will never produce 100% work. Is there any chances where the loss heat energy can be recycle, for example a furnace that is used for metal forging, has a pool of water surrounding it to absorb the loss heat energy, heats up the water and the steam produced is used to generate electricity?
ANS: Yup...you will never get 100%...but you can put some effort...in term of proper design of the system..so that...the work produce close to the maximum value. Yes of course by using the method that you mention (recycle the heat), this way will consider as a method to reduce the heat release from the system. When the heat release reduce. You already increase the efficiency of the system. When you learn about the power plant later on..the process is call reheating process...which is try to fully utilize the heat that suppose release to the environment.
FAQ 1.18: Hi Dr and assalamualaikum, I want to ask it is possible to achieve 0% heat loss for heat energy in vacuum conditions?
ANS: Waalaikummussalam...the condition violate the thermodynamics law. For heat system, part of energy from it heat source must be released for a complete cycle of thermodynamic to be done. In Vacuum, heat can transfer through radiation heat transfer.
FAQ 1.19: Why it is devided into exergy and energy? And which from both of them is more important?
ANS: Exergy is some sort like imaginary energy that describe the maximum potential of energy that produce useful work. The exergy properties can be use as comparison or standard to know how good or efficient in term of performance compare to it maximum capability. For example went we create a steam engine. First, we calculate what is the maximum performance for the engine (involve exergy). Then calculate..for actual condition of the engine when running. If the engine performance is far below the max. performance, we know that the engine is not good enough, so some improvement need to be done to reduce losses occur. We will get better engine if the performance close to the maximum one.
FAQ 1.20: Dr, I have question. Is maximum power is also known as maximum possible work? Is it the same?
ANS: Power is derive from the work...work is in kJ...power is in kJ/s or kW. Power is equal to rate of work. Maximum power is not equal to maximum work because the value will be different for the same system due to different units used
FAQ 1.21: Is the immediate surroundings and environment will always be the same ? Or it may vary according to the how the energy transferred ?
ANS: There is immediate surrounding if the temperature of a body (in this case the potato) is different from the environment. However, If the body temperature is in equilibrium with the environment which is the body temperature equal to environment temperature. Thus, by definition there will be no immediate surrounding.
FAQ 1.22: Assalamualaikum dr, may I know the difference between both exergy formula (X in capital letter and x in small letter)?And my next question, is there any possible chances where the loss heat energy can be recycle?
ANS: The difference is the term/terminology or Unit used for X or x. Please refer my previous response above. Yes of course by using the method that you mention (recycle the heat), this way will consider as a method to reduce the heat release from the system. When the heat release reduce. You already increase the efficiency of the system. When you learn about the power plant later on..the process is call reheating process...which is try to fully utilize the heat that suppose release to the environment.
FAQ 1.23: Hi, sir I have two questions. (1) At min 12.28, I don't quite understand how we get the equations for the expansion and compression process. Is it important to know how it is derived? (2) At min 19.33. Same nature as previous question. How do we get those equations for work producing device and work consuming device. is it important to understand later on or just take it as it is?
ANS: 12:28 : The equation actually come from the energy balance equation (Ein-Eout = Delta Esystem) for closed steady flow device (in this case is piston cylinder device). For the formula the direction or work is important. Wb for compression is downward and Wsurr also in downward direction. So that why you will get Wu = Wb + Wsurr. However, Wb for expansion is upward and Wsurr is in downward direction. So that why you will get Wu = Wb - Wsurr. For derivation of equation...not need to memorize..but it is good if your can understand how the equation derived. So that you can appreciate. Later on...if your future work involve with programming or research and so on...how the equation is derived is important to know. 19:33: Same goes to this....This involve with first law of thermo dynamic...for steady process..Ein=Eout....We know that...Wrev is the maximum value....Wu is the actual work...So..Wrev=Wu + I (losses) ..then we can calculate the losses....where the lossess is represent by irrevesibility in that case. The difference for consuming and producing device..is ...for work producing device (exp: Turbine). Wu produced is lower than Wrev..that why I= Wrev-Wu.....otherwise we will get negative value of I..which is imposibble in thermo. For work consuming device (exp: Pump). Wrev is lower than Wu provided..that why I= Wu-Wrev.....otherwise we will also get negative value of I..which imposibble in thermo.
FAQ 1.24: In example 1.3, does it matter whether to put on the symbol work with dot? (does Ẇ the same as W?)
ANS: Ẇ is not the same with W. Both symbols use different units. The unit for . However, the unit for W is kJ. Since the question as about power, you need to use Ẇ because the unit of power is kJ/s or kW.
FAQ 1.25: WHAT IS DEAD STATE ?
ANS: Dead state mean..the final state of the system is equal to the environment condition. For example... if the air temperature in piston cylinder device is 100C at initial state. Let say over the time...due to heat release...the temperature will reduce..to..90...80...70....until 25 C. Which is now equal to environment temperature 25 C. This final state considered as the dead state. Similarly with the temperature.
FAQ 1.26: (a) Does the boundary work will change due to the volume change only or there are other factors considered? (b) Why the surrounding work moves downwards in the system (is it compulsory to know the actual direction of each work produced?) (c) Could Dr explain what is irreversibility in detail? I am quite confusing about the terms, does it mean the work is no more useful?
ANS: (a) Yes boundary work change due to boundary volume change..If you look to the boundary work equation..you will see...volume difference term in the equation. The boundary work only exist for the system with moving boundary. The system with fix boundary will have no work boundary. (b) The surrounding work actually cause by the atmospheric pressure...the direction of the pressure actually are perpendicular to any surface. The pressure is act at all surface of the piston cylinder including the cylinder walls from the right...left..and the bottom..and above...however the wall doesn't move. So..not contribute to any work. The only direction that contribute to work is the pressure that act on the piston surface. Because the piston is freely move when any pressure or force act to it, the pressure direction downward as in the figure in my lecture note...will contribute to the work in the system. (c) In a simple meaning..Irreversibility...is involve with the factor that cause losses in the process of a system..such as..heat loss...chemical reaction...friction...temperature drop..pressure drop..etc...Process that involve irrevesibility in not an ideal process...and considered as actual process or real process. If the irreversibility of a process is zero. The process is consider as an ideal process..or in other word is a reversible process.
FAQ 1.27: Do reversible work really occur in industrial? Since most of the working machines will undergo wear and tear which cause difference between initial and final states.
ANS: In our real life the processes involve are actual process. Most of the process will involve irreversiblity factors such..friction..chemical reaction..wear..heat loss and so on. So in real world most of the process are irreversible process...however we can create the process close to the reversible process a.k.a ..the ideal process by proper control the irreversibility factor that might be occur in our system. That why..the term of Efficiency come into our discussion....
FAQ 1.28: Irreversibility work is the difference between Wrev and Wu. My question is if the Irreversible,I is equal to zero, does it will become reversible work?
ANS: Yes ..correct...If I=0..the process is reversible
FAQ 1.29: Salam Dr, sorry because I do not understand in the piston system, how can the piston will expand or compress? or is the density of the atmospheric air and density in the system play role in determining the process?
ANS: Salam..in the piston. The density is the outcome of the expansion and compression. Any gas that go through the compression process..the density will be increase...however when go through the expansion process the density will be decrease...due to the compactness of the molecules inside the medium volume. In the example for heat system..the expansion is due to the heat provided to the system,,,due to the increase of molecule kinetic energy..the air expand and the piston move upward. However for compression, the heat source will be remove to allow heat release to surrounding. So that the volume of air or gas reduce and the piston will move downward. In the slide i did not include the heat because some system not needto use heat for the expansion process..for example...we just make an inlet at the cylinder wall and add in additional gas or air in to the cylinder. Thus, the schematic diagram just want to shows the general condition of expansion and compression.
FAQ 1.30: Is it a irreversibility is same concept with heat loss?
ANS: Irreversibility is considered for any type of losses such as friction, chemical reaction, etc...including the heat loss.
FAQ 1.31: It is possible for a system to achieve zero exergy destruction in actual situation?
ANS: No. If Exergy Destroyed is zero..the system or process will have no losses...no irreversibility. The system considered as a perfect or ideal system or reversible process. But we can try to minimize the value by proper design the system.
FAQ 1.32: Salam dr, I do not know much about isentropic process, can you give me a terminology or example about it?
ANS: Isentropic mean the value of entropy (s) is same at initial and final condition of a process. You have to go back to chapter entropy in your thermo 1. The entropy actually is a properties that hard to explain because it is an abstract properties. However, the entropy can describe how chaotic the movement of a molecules of a substance. Where this condition have relation with temperature and heat transfer. If we increase the temperature of a substance, the molecule in the substance in term of chaotic level will be increase....more friction..collision between molecules and so on. Thus this condition cause higher value of entropy. By decrease the temperature..the chaotic lecel of molecule will be reduce..thus the value entropy also reduce. For the isentropic process..we can say that the chaotic level of molecules of a substance is constant for the initial and final. Thus the entropy value also constant. At this condition we consider no losses during the process.
FAQ 1.33: Is there any process or condition that benefits from irreversibility rate?
ANS: If we want to get benefit from the irreversibility..we need to reduce the value..by improving our system.
FAQ 1.34: Are there any natural processes that are reversible?
ANS: Maybe can be done for certain system in a vacuum. Such as pundulum in a vacuum. Let me know if get some information about that.
FAQ 1.35: Dr, I did not clear on how to determine the useful work and boundary work. What is the difference?
ANS: Useful work..can be the combination of different type of work. In these case the boundary word and the surrounding work are contribute to the useful work value.
FAQ 1.36: I cant really understand the terms where irreversibility equal to exergy destroyed. is it the exergy destroyed through out the process between the specified initial and final state?
ANS: In a simple meaning..Irreversibility...is involve with the factor that cause losses in the process of a system..such as..heat loss...chemical reaction...friction...temperature drop..pressure drop..etc...Process that involve irrevesibility in not an ideal process...and considered as actual process or real process. If the irreversibility of a process is zero. The process is consider as an ideal process..or in other word is a reversible process. Any process involve with irreversibility, there will be the exergy destroyed....exergy destroyed..also mean the loss of energy potential.
FAQ 1.37: If the exergy is destroyed, the energy is converted into another type of energy right ? Exergy destroyed gives meaning that there’s no energy that can be extracted from the energy source. Is my understanding regarding “exergy destroyed” correct?
ANS: Exergy Destroyed involve with energy loss or irreversibility. Suppose the energy can convert into work. Initially the energy also have potential to produce useful work..due to irreversibility factors during the process. This energy is loss to surrounding and not use to produce useful work. So the potential of the energy to produce work was destroyed or wasted. In simple meaning..The Exergy destroyed is how much the potential of energy to produce useful work was destroyed or wasted.
FAQ 1.38: I don't understand on the "not isentropic process". In adiabatic process, Q=0 so is this the reason where it does not involve heat loses or involve heat loses?
ANS: Isentropic process and adiabatic process are two separate process. For Adiabatic process, due to the whole system is well insulated, thus the process will not allow any heat transfer in to the system or any heat transfer out from the system. So, heat in any direction is zero, Q=0. Isentropic mean the value of entropy (s) is same at initial and final condition of a process. You have to go back to chapter entropy in your thermo 1. The entropy actually is a properties that hard to explain because it is an abstract properties. However, the entropy can describe how chaotic the movement of a molecules of a substance. Where this condition have relation with temperature and heat transfer. If we increase the temperature of a substance, the molecule in the substance in term of chaotic level will be increase....more friction..collision between molecules and so on. Thus this condition cause higher value of entropy. By decrease the temperature..the chaotic lecel of molecule will be reduce..thus the value entropy also reduce. For the isentropic process..we can say that the chaotic level of molecules of a substance is constant for the initial and final. Thus the entropy value also constant. At this condition we consider no losses during the process.
FAQ 1.39: Energy cannot be created or destroyed. Can Dr tell me , how this relates to the ability of reversible and irreversibility of the heat energy?
ANS: Energy cannot be created or destroyed related to the first law. The total energy transfer in the system = Energy change of the system. For example ..a heat engine involve with irreversibility (Heat loss)...simple equation....Heat Source = Heat Release+ Heat Loss + Work Produced. Energy just change in term of type. The total energy is the same. If you the same equation for reversible process..the equation ignore the heat loss...now the equation will be...Heat Source = Heat Release+Work Produced.
FAQ 1.40: Salam dr, I want to ask what kind of industry that use reversible work and irreversibilty.
ANS: All industry that particular about performance and efficiency will use these concept.
FAQ 1.41: Assalamualaikum dr, could you explain more in details what does it means by irreversibility? Does it means the work is no more useful since irreversibility is equal to energy destroyed?
ANS: Waalaikummussalam...Exergy Destroyed involve with energy loss or irreversibility. Suppose the energy can convert into work. Initially the energy also have potential to produce useful work..due to irreversibility factors during the process. This energy is loss to surrounding and not use to produce useful work. So the potential of the energy to produce work was destroyed or wasted. In simple meaning..The Exergy destroyed is how much the potential of energy to produce useful work was destroyed or wasted.
FAQ 1.42: My assumption for "Higher Performance" terms is the value of thermal efficiency is close to its maximum efficiency. However, how it relate with Second Law of Thermodynamics that stated "Quality of Energy is reference to the best possible performance"? It is mean that higher performance system also produces the higher quality of energy?
ANS: Quality is something subjective properties. We have to have a standard to know whether certain system or product is better than others. The standard to be compare must have almost or perfect value or properties. By having this standard we will know...product A is better than product B by comparing to the standard. For example we have steel ball A and steel ball B, we want to determine the best properties in term the roundness of the steel ball shape. In order to decide, we have to refer the high standard steel ball roundness standard. That how the quality of a steel ball can be determined by comparing steel A and B with the standard steel ball.
FAQ 1.43: For the last question about the electrical resistance heater, it is showing that the performance of the heater is not good although the efficiency is 100%, does it mean the higher COP value will get us the lower value of second law of efficiency for any situation or there is another factor to influence the variables? Does it also mean that the nII will get higher if the temperature for TH and TL are quite large different (since it can work better, like it is wasting the We).
ANS: The higher COP value will give us the higher value of second law of efficiency because the value will be approaching the max value of COP. Remember that COP value can be more than 100%..200..1000 and so on...for the example max COP that can be achieved is 2670%. COP for the heater can be calculated for this equation...COP=Qh/Win. Thus..both Heat release from the heater and electric current provide to the heater will influence the COP. The effect of TH and TL to the nII is depend on the both value. In this case if we look to the equation of nth,rev...the important parameter is the TL/TH ratio. Let say out COP for actual process is fix. TL/TH is smaller. The we will get small COPrev. Thus nII will be higher. But if TL/TH is bigger. The we will get bigger COPrev. Thus nII will be smaller.
FAQ 1.44: Hi sir, I am basing my question based on min 34.00. Is the exergy that is recovered means that the exergy is reversible?
ANS: exergy recovered means the max potential of energy required for the specific system. One of the criteria for the exergy is the process must be reversible.
FAQ 1.45: Salam Dr, how we can know when to use the exergy per unit mass formula if it is not stated in the question?
ANS: Salam ..if the question not state any...you can choose to use kJ or KJ/kg. If the question state the specific unit, you have to use the same unit state by the question
FAQ 1.46: How do we set the boundaries ? From the video, the closed system boundary includes the electric heater while in the open system excludes the electric heater.
ANS: We can choose any boundary for our analysis....but normally we will use the boundary that very close to the wall of the system...the implementation of energy balance will be the same. The difference are the types of energy need to be include or exclude in the equation, where this must based on the basic principle where the energy must cross the boundary. In this example, i show 2 different boundaries to show the difference of energy selected in the equation based on the cross boundary principle.
FAQ 2.1: Salam dr, saya kurang faham term sink temperature dalam contact heat transfer sebab biasanya klau dalam engine dia berkaitan cooling system dekat radiator.
ANS: Sink tu merujuk medium dimana tenaga haba di bebaskan....radiator sebagai alat untuk membebaskan haba dari engine..haba seterusnya di bebaskan ke persekitaran...persekitaran dikira sebagai medium dimana haba dibebaskan (Sink)
FAQ 2.2: In carnot cycle, how does the base of the cylinder changes it properties from insulated to not insulated (allowing/disallowing heat transfer)
ANS: The schematic diagram just use to explain the process in the P-V and T-s diagram...where involve many assumption in order to simplified the actual anaylisis. In actual one no such process involve (install and remove insulation).
FAQ 2.3: For the heat engine, do we use the heat addition process to do the analysis for the combustion process or we use both combustion and heat addition process to do the analysis? I’m just confuse either we should substitute the process or compare the process to do the analysis.
ANS: For the heat engine, use the heat addition process to do the analysis for the combustion process .
FAQ 2.4: Hi sir i want to ask regarding the last slide of part 3 where the question asked us to determine the MEP of each engine. So i want to ask is the V in the formulae represents volume of the cylinder? since the question only provides the date of the diameter. Thanks!!
ANS: V refer to the volume of the cylinder relative to the piston position. If the problem only give you the diameter, so you need to calculate the volume by using cylinder formula. You need to have one more parameter to calculate the volume..which is the height of the cylinder relative to the piston position.
FAQ 2.5: What is the difference between Carnot cycle and Otto cycle in term of analysis?
ANS: Carnot is the best performance of heat engine cycle that can be achieved by the otto cycle or the diesel cycle. Same concept when we learn about the exergy, the max potential of a heat engine is the carnot cycle performance.
FAQ 2.6: Assalamualaikum Dr, even though this is basic term but I can't get what is the isentropic that Dr keep repeating in the video. can Dr give me the simplest sense of the isentropic. Thanks in advance.
ANS: Waalaikummussalam...isentropic mean....the value of entropy (s) does not change through the process. The isentropic process will considered as an ideal process. For example isentropic compression process for a compressor. Through out the compression process of the compressor the value of entropy at the inlet and at the outlet are the same. The performance of the compressor is 100% for the isentropic process.
FAQ 2.7: Assalamualaikum Dr, for example 2.5, why we need to find the mass (m)?I mean why use capital Qin instead of qin? I tried to repeat that part for few times but still didnt get it.
ANS: Waalaikummussalam....it is depend on the question. For this example..it doesn't matter if you want to use Qin or qin...just beware about the unit..Qin in kJ.....qin in kJ/kg. m determination due to..in the example i use Qin. But if you want to use qin...no need to determine m. However if the problem ask use to answer the question in kJ unit...so you have to use Qin and find mass. And vice versa.
FAQ 3.1: (1) why does work occur when isentropic is constant, sir? and also, why does heat in/out occur when volume is constant? Is that true for all systems (Otto/Diesel)? (2) at min 51.29, sir why use square root of 8? I don't understand.
ANS: as explained during our live session.
FAQ 4.1: Assalam Dr. I would like to ask about Example 4.2 in slide. From my understanding, we need to refer to Saturated Water Table for State 1. Data given for state 1 is temperature and pressure. So which table we need to refer as Saturated Water Table has for temperature table and pressure table.
ANS: In the example, state 1 is in compressed liquid region. However the data is not available for the pressure given. Minimum pressure for compressed liquid table is 15 MPa. Thus for pressure less than 15 MPa, we need to make an assumption, where the closest assumption to compressed liquid is saturated liquid which is still 100% liquid. Due to this assumption, we need to refer Saturated Water Table based on temperature, to minimize the calculation error. Saturated Water table based on pressure will cause more error in your calculation. But if the original condition for state 1 is already saturated liquid, both saturated water table based on temperature and pressure can be used. This is because both tables will give you the same data.
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