The engineer gives us his argumentative point of view on these complementary technologies that are increasingly being implemented in our industries.
By Camilo Botero*
At the request of the Editor of this prestigious magazine, I will make some reflections on the topics of the title of this column, mainly with regard to the digital programs that we use in the air conditioning industry.
Starting with the fundamentals, there is the software to represent the psychrometry of the projects; its properties and thermodynamic states involved, the processes, the mass and energy balances, and finally the calculations of flows, powers, sensible heat factor, bypass factor, available temperature delta, etc.
There are many different types of temperatures, depending on the application, normal air conditioning temperatures, low temperatures for refrigeration, dry bulb temperature scale, with higher values, for drying processes with chemical dehumidification and drying with heating, for example with natural gas, directly to the air flow.
One of the pioneers of applied psychrometry was Eng. Willis Carrier, in 1911, simultaneously with European scientists since the end of the nineteenth century, and nowadays ASHRAE and the great brands of equipment around the world, have developed the theory of psychrometry, and of course the software we use.
In 1981 I took a 300-hour Air Conditioning Design course at Carrier Syracuse NY, Bynum Center. More than half of the course was devoted to the classes of applied psychreometry taught by Professor Carpenter, following his book that I still have; At that time there was no software for this discipline and we used psychrometric charts printed at different heights above sea level: 0, 2500, 5000, 7500 and 10,000 feet altitude, were the most common and for the other heights it was averaged.
As an academic and engineering exercise, I made my own psychrometric chart for an altitude of 1000 meters, approximately 3200 feet, using the learned equations and drawing it in AutoCAD. It turned out to be a good approximation and I still use it as in this recent example.
Psychometry table.
In the 1990s, major companies in the industry developed their own psychrometry software for specific applications; At the same time, calculation programs were developed for various requirements of HVAC projects:
• Piping design for all types of liquids and gases.
• Design of ducts, with all their accessories.
• Duct design by the static regain method.
• Coil selection
• Selection of Air Handling Units, Fan Coils, Cassettes, Energy Recuperators etc.
• Selection of Chillers, Condensing Units, Rooftop, etc.
• Selection of refrigerant compressors and other vapres and gases.
• Pump selection, for multiple applications.
• Selection of fans of all types and applications.
• Gas turbine selection
• Selection of steam turbines.
There are also companies in the USA, Europe and Asia that are dedicated to developing calculation programs for all engineering companies.
I only have one objection regarding the software and that is the Thermal Load calculation programs, because I consider that this function is more an art that depends largely on the experience and fundamentals of air conditioning engineering, than on the Thermal Load Calculation program itself, as they are excellent and very sophisticated; Because many times those who design without experience, or good theoretical bases, psychrometry, thermofluids, thermal inertia, partial loads, climate, etc., make serious mistakes.
When I give this opinion in class, conferences or technical committees, I am more or less labeled a "technological dinosaur", but I know that I am right on this point. I've seen too many failed projects because of bad K for C.T. in excellent software.
Below, I present a recent example of S.C. elaborated in an Excel sheet, which I designed based on Carrier's E-20 form, more than 40 years ago, and which I still use, especially in industrial projects, where the C.T. software used for Air Conditioning usually does not work well.
Table 2. Thermal Load Calculation – ABC Control Walk
Artificial intelligence
Regarding Artificial Intelligence, as fashionable as it is controversial and diffuse, which has invaded our lives and activities; It is no exception in air conditioning and refrigeration, topics such as robotics in the manufacture of equipment, electronics in controls that are increasingly necessary and essential in projects, the Internet of Things incorporated in equipment, for example, in domestic refrigerators, "machine learning", such as pumps that self-control and seek their point of maximum efficiency, Remote operation, real-time weather information through satellites and other aspects are a reality.
To conclude, I will briefly refer to Quantum Computing, in our industry. I have been studying quantum physics as a hobby, and to summarize the result of this learning I will quote a phrase that reassures me because of the lack of understanding of the subject: "Whoever says that he understood quantum physics did not understand".
I bring up this topic, because there is an aspect that is fundamental for quantum computers to be able to work, linked to cooling, and that is that in order to get the subatomic particles to "stay still and in one place", to be able to use them in the quantum computer, very low temperatures are required, in the order of 0.06 degrees K. That is practically absolute zero and the technology to achieve it is very complex.
I had the opportunity to see several years ago at the University of Dresden in Germany, achieving 0.1 degrees K, with a refrigeration system where the coolant was water. My heart raced with excitement at the sight of such a technological feat.
* Camilo Botero was Secretary of the Federation of Ibero-American Associations of Air Conditioning and Refrigeration - FAIAR; He was president of ACAIRE and is president of Camilo Botero Ingenieros Consultores Ltda. He is currently a professor at his CBG Academy. He has also worked as a professor in several Colombian universities, guilds and currently in ACAIRE in diploma courses on air conditioning projects, energy efficiency in air conditioning and refrigeration, cogeneration and trigeneration, applied psychometrics, thermodynamics, fluid mechanics, heat transfer and turbomachinery.
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