Entropy is not a state variable, and there is a physical difference between it and internal energy.
In the textbook, the ideal gas entropy: S = n * Cv * In (T) +nR * In (V);
There are two problems:
1. The natural logarithm In(x) will submerge the unit system of volume and temperature [m3], [K].
2. The unit of temperature may be [K], or [mK]; the unit of volume may be [m3], or [cm3]. The results are different and the calculation lacks stability.
Entropy is only a process quantity: DS = n * Cv * In (T2/T1) + nR * In (V2/V1); it has physical significance.
Internal energy is a state quantity, and entropy is only a process quantity. There are physical differences between them.
Internal energy U is conserved and can have the meaning of total differential dU = Ut * dT + Uv * dV - correct.
Entropy is only a process quantity, not a state quantity. Total differential is meaningless: dS = St * dT + Sv * dV - - incorrect.
Entropy is not conservative, even in reversible cycles, it can increase or decrease.
Thermodynamics has some problems in describing ideal gases.
Arguments of logarithmic functions should be dimensionless.
The entropy of the ideal gas is given by the famous Sackur-Tetrode equation,
i.e. it can be expressed in terms of the internal energy.
Indeed, I see no need to revise the thermodynamic description of an ideal gas.
Thank you for your reply.
1. From the thermodynamic definition (dS = dQ / T), the denominator position of temperature necessarily leads to S = n * Cv * In (T) + nR * In (V).
2. Sackur-Tetrode formula is based on the statistical definition of entropy. I don't like to use statistical definition to solve the problem of thermodynamic definition.
3. Okay, let's put aside the discussion of conceptual issues and discuss how to deduce Carnot efficiency = 1-T1/T2 from the second law of thermodynamics. This is Clausius'and Kelvin's thesis and the content of thermodynamics textbooks.
************************
Logical error of the second law of thermodynamics:
1. There are many kinds of type 2 perpetual motion machines. Behind each type is a natural phenomenon.
Machine A: against the irreversibility of thermodynamics (diffusion, heat conduction, friction, etc) - dynamics;
Machine B: Utilizing the Difference of Carnot Efficiency (Reversible Thermodynamics) - Thermodynamics
2. A and B belong to different disciplines. There is a parallel relationship between them, and there is no logical mutual inevitability.
Heat 2 Logic: Experience induction, deny that A machine==》 B machine can not be manufactured==》 All material Kano efficiency: 1-T1/T2.
3. Logical of the second law of thermodynamics violates the physical logic that A and B cannot be inferred from each other.
4. the second law of thermodynamics elevates the "irreversibility", but it is only a kinetic experience.
5. See the annex for details.
The second law of thermodynamics is far too out of line with the deviation rate of 10-80 times？
1. Doctor asked me to build a perpetual motion machine, so I won't be fooled.
In 1905, Einstein put forward the theory of relativity. The atomic bomb was produced in 1945. After 1905, scientists quickly recognized the theory of relativity. There is no need to wait 40 years. Human beings have brains and rationality.
2. Reality has a perpetual motion.
**********************************************
3. When the second law of thermodynamics is applied to capillary phenomena, there is Kelvin's formula.
3.1, P1 - capillary liquid surface vapor pressure
P--Horizontal liquid surface vapor pressure
ro ---- Steam Density
h ---- height of liquid column.
3.2, theoretical results of the second law of thermodynamics: P1 = P 0 - ro*g*h
Experiments: P1=P-(10-80)ro*g*h
4.The second law of thermodynamics is far too out of line with the deviation rate of 10-80 times.
5. The capillary experiment negates the Kelvin formula and the second law (that an isolated system must have an equilibrium state).
6. It is easy to imagine that the gas evaporates from the horizontal liquid surface, enters the capillary from the outside (gas phase), condenses, and returns to the horizontal position from the liquid phase, and starts again and again.
7. See the attached drawings for details.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Thermodynamics