## Shortcomings of textbooks

Apart from the shortcomings of books on thermodynamics, and there are many, similar shortcomings exist in other textbooks because of lack of being precise that discuss, for example, heat transfer which is an applied course heavily dependent on thermodynamic principles. The student is learning from the textbooks; therefore, they trust the contents as they must. However, if the topics are not precisely covered, then they learn the wrong material.

As an example, we will consider condensation phenomena since it is an important process in thermodynamics, as we have discussed above in the case of the Clausius-Clapeyron equation and the steam experiment, and since we must design condensers for technological purposes, using heat transfer. When one considers the condensation phenomenon as discussed in textbooks, also as was done by Arnas et al. (2004), there are many assumptions that are made to be able to analyze the physical situation. Unfortunately in all of these, the assumptions that are made are not justified for the final result. The final result is the same in all of the references, the only thing different are the symbols used. However, the student does not know if a given situation actually satisfies all the assumptions made. Therefore, for all situations, the only design equation is the one found in the texts and that one is used blindly. It is indeed possible to find situations where any one of these conditions is not met which would make the equation useless. In Arnas e t al. (2004) not only is the result obtained very rigorously and in a very clear and analytical fashion, the conditions under which the result is valid are also very clearly given so that the user, the student, the researcher, or the design engineer is able to ascertain if the problem actually fits the final design equation for convection in condensation.

In another study by Arnas et al. (1980), it was shown that the two-phase flow design equations are not usable under all conditions since they tend to decrease the entropy generation for certain combinations of flow rates and geometries, a condition that violates the second law of thermodynamics. Naturally, methodology given above, it is indeed very simple to show that the analytical re-

under those conditions the equations cannot be used for design purposes and other correlations must be searched.

What has been attempted here is to show the importance of correct use of precise thermodynamics in teaching of thermodynamics as well as in all other fields of science and technology. If it is not used precisely, errors are made that could affect the designed equipment or lead to disastrous situations in extreme cases. In engineering we cannot make mistakes since, unlike the doctor, we do not kill one person at a time! Our failures are watched and seen by the whole world, for example the Space Shuttle disaster. We must teach well, in a correct way, and precisely and demand of our students at all levels the same precision in their work, Arnas (2005). Only in that fashion can we be sure that the next generation of engineers/scientists understands the critical ramifications of what is at stake. This is more important than anything else that we can teach our students, their understanding and appreciation of the importance of their precise work.