Intermediate Thermodynamics Questions & Answers  




I guess what you mean is whether the water mixes with the butane. The answer is no, the water remains in the cooling jacket and does not mix with the fuel or the combustion products (the combustion takes place in one duct, while the water flows in another duct surrounding the first one). I already explained this in class... I'll give you 0.5 point bonus boost for this question.




Hm, the question doesn't make sense. Explain better what is the problem — I didn't mention about the volume but the mass flow rates. Also, typeset your mathematics correctly.




I strongly recommend not to use theories that I have not covered in class... All problems in the assignments and exams can be solved using the theory shown in class — do that and you'll score very well on the test! I will not give you a bonus boost for this question because it is out of the scope of this course.




Your question is not so clear, you should give more details. But I think the problem in this case is that you are mixing two strategies together. To find $\overline{v}_2$ and $T_2$ try to use only one strategy: you can use either Van der waals or the generalized compressibility charts, but try to avoid using both on top of each other. The generalized compressibility charts is the strategy that is the most accurate and should be preferred in this case. I'll give you 1 point bonus for this question.




There is a mistake in your reasoning. You define correctly the mixture enthalpy as used in the psychrometric chart: $$ \tilde{h}_{4}=\frac{\dot{m}_{v4} h_{v4} + \dot{m}_{A4} h_{A4}}{\dot{m}_{A4}} = \frac{\dot{m}_{mix4} h_{mix4}}{\dot{m}_{A4}} $$ But you must express $h_{\rm A4}=C_P T_{\rm A4}$ with $T_{\rm A4}$ in Celcius. Also, when calculating the other air enthalpy $h_{\rm A3}$ you must use Celcius degrees, not Kelvin. Celcius must be used and not Kelvin because those who made the psychrometric chart defined their enthalpies this way. Try it again ;) I'll give you 1.5 point bonus boost for this question. 



You can only use the two expressions you are mentioning when the gas is calorically perfect and thermally perfect... Unfortunately, when using the Van der Waal equation of state, the gas is not thermally perfect and the latter can not be used.. You need to find another way to solve the problem. I'll give you 1 point bonus boost for this question.




Yes you are correct. The 9% error comes from the fact that we assumed $\bar{q}\approx\sqrt{\overline{q^2}}$. Very good observation. But for completeness you should explain what the definition of $f(v_x)$ is.




Great, this makes your previous post clearer!




Parts per million of species X means number of molecules/atoms of species X per millions of molecules/atoms in the mixture.



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