Responses To Criticisms of The Constructal Law
Bejan has responded to this criticism by noting that the constructal law is not about what flows, but about the physics phenomenon of how any flow system acquires its evolving configuration (design) in time. The constructal law is not about optimality (max, min, opt)—it is the definition of “life” in physics terms, and of the time direction of the changes in flow configuration.
Bejan also noted that the phenomenon governed by the constructal law (design in nature) is macroscopic (finite size, not infinitesimal). It is the birth of design and evolution of design in all the parts together. It is dynamic, not static. The evolution never ends. There is no end design, no destiny (max, min, opt).
Bejan and Lorente expanded on this by explaining the difference between a law of physics (e.g., the constructal law) and the many invocations of the law, which underpin many theories based on the law. In the section titled “The constructal law versus the second law of thermodynamics” they noted that the constructal law and the second law are first principles. The constructal law is a useful reminder not only of what was missing in physics and thermodynamics (the law of design and evolution) but also of what is present. For example, contrary to the critic’s view, the first and second laws of thermodynamics did not require any “proof based on simplified systems of statistical physics.”
The constructal law is a statement of a natural tendency—the time direction of the phenomenon. It is as non-mathematical as the original statements of the second law:
Clausius: No process is possible whose sole result is the transfer of heat from a body of lower temperature to a body of higher temperature.
Kelvin: Spontaneously, heat cannot flow from cold regions to hot regions without external work being performed on the system.
A new law does not have to be stated in mathematical terms. The mathematization of the second law statement (and of thermodynamics) came later. The constructal law underwent the same evolution. The 1996 statement was followed in 2004 by a complete mathematical formulation of constructal-law thermodynamics .
Like any other law of physics, the constructal law is a concise summary of observed facts: the natural tendency of flow systems to evolve toward configurations that provide easier access over time. The word “access” means the ability to move through a confined space such as a crowded room. This mental viewing covers all the flow design and evolution phenomena, animate and inanimate, because they all morph to enter and to flow better, more easily.
Read more about this topic: Constructal Theory
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