Heat Flowing from Cold to Hot
“Heat Flowing from Cold to Hot without External Intervention” Demystified*):
Thermal-Transformer and Temperature Oscillator
Milivoje M. Kostic
Professor Emeritus at Northern Illinois University, USA
A recent Science Advances paper by Schilling et al*) , claiming “flow of heat from cold to hot without intervention” with “oscillatory thermal inertia” are fundamentally misplaced and dramatized as miraculous, even though compliance with the Second Law of thermodynamics is acknowledged. There is nothing “magical and beyond the proof-of-concept” as claimed. It could have been achieved by any work generating device, stored by any suitable device (superconductive inductor was beneficial but not essential as claimed), and such stored work used subsequently in any refrigeration device to sub-cool the body. Cooling devices work by transforming temperature to desired level by work transfer (thermal transformer and temperature oscillator), by non-thermal, adiabatic processes. However, the “direct heat transfer” is always from higher to lower temperature in all refrigeration components, without exception – it is not to be confused by “net-transport of thermal energy by work” from cold to hot ambients. The unjustified claims are critically analyzed and demystified here.
*) A. Schilling, X. Zhang and O. Bossen. Heat flowing from cold to hot without external intervention by using a “thermal inductor”. Science Advances, 2019. DOI: 10.1126/sciadv.aat9953.
This writing is instigated by the recent publication, “Heat flowing from cold to hot without external intervention by using a ‘thermal inductor’” (1), as well as by other similar, subtle and elusive thermal phenomena. The authors, regardless of acknowledging non-violation of the Second Law, have interpreted their results as a “thermodynamic magic” and made fundamentally-false critical claims. However, it was only an interesting and creative “show-and-tell” innovative application, although impractical, but not miraculous nor unusual and “beyond the-proof-of-concept” as presented. Being published in a reputable journal (1) and along with dramatic news releases (2), followed by intriguing popular articles, “Bending (But not Breaking) the Second Law” (3) and others, it resulted in misleading and unusually widespread publicity, even hype. There is a need to dissect and rectify the published misleading claims and demystify all magic by presenting due critical reasoning and subtle thermodynamic analysis related to above publication and ever-increasing challenges to the Second Law of thermodynamics (4), which is the main objective of this article.
There is nothing wrong with the calculated results using simplified modeling nor with elaborative but very inefficient experimental results, with barely visible outcome of only about 2 oC sub-cooling and negligible efficiency, regardless of use of superconductive inductor (1). However, the fundamentally false claims and dramatic interpretation of the results published in a reputable journal, require objective, phenomenological reasoning and due thermodynamic analysis, beyond the mathematical modeling. The following, fundamentally false claims: (1.) “Heat flow from cold to hot without external intervention, and without any source of power,” (2.) “Direct heat flow (or transfer) from cold to hot in the Peltier TE element,” (3.) “Use of inductor is essential,” and (4.) “Some kind of ‘thermal inertia’,” are demystified in full details here.
As a matter of fact, it would be violation of the Second Law of thermodynamics for “heat to [actually] directly flow from cold to hot” and it never happens in nature, it would be physically impossible to destroy entropy. Without exception, including all classical refrigeration and other cooling devices and their components (evaporators, condensers, etc.) the heat is always, actually transferred from hot to cold, and never otherwise. This is not to be confused with the net-transport of heat from cold to hot ambients, transported with material medium (an electron stream or refrigerant in general) while temperature of the medium is transformed by work, increased or decreased to drive heat transfer as desired (as in all thermal-power generation, cooling or heat pump devices). The Fourier’s, direct heat transfer (from hot to cold only) should not be confused with transport of thermal energy (from any to any temperature level). The heat is actually transferred from the subcooled body to the even lower temperature of the Peltier cold end-plate (as is done from the cold food in a refrigerator to even colder evaporator plate inside), and after being adiabatically transported with temperature increase by electron stream (similar to a refrigerant medium transport and compression in a refrigerator), the heat is then transferred from higher temperature of the Peltier hot end-plate to the lower temperature of a surrounding reservoir (as is done from the hot condenser fins to the colder ambient air outside a refrigerator) -- the heat being always, actually transferred from hot to cold, and never otherwise, see Fig. 1.
In fact, since the heat could be net-transferred, i.e., transported from any-to-any temperature level using relevant thermal cycles and related devices (e.g., heat engines, other thermal-work generators, refrigerators and heat pumps), they may be considered as “thermal transformers,” where the temperature level could be transformed to any desired level, like the voltage is in electrical transformers.
There is a need to further illuminate and demystify thermodynamic facts from confusion and mystique, since there are many puzzling issues still surrounding thermodynamics and the nature of heat, including subtle definitions and ambiguous meanings of some very fundamental concepts (5, 6).
The nature of heat was intriguing since its introduction, starting from Lavoisier, who presumed that caloric as a weightless substance is conserved, to Sadi Carnot (7) who erroneously assumed that work is extracted while caloric is conserved, to modern day researchers who argue that thermal energy is an indistinguishable part of internal energy, to the generalization of entropy and challengers of the Second Law of thermodynamics (4, 8). In fact, all other forms of energies are ultimately dissipated in thermal heat, the omnipresent and universal phenomena, quantified with perpetual and irreversible generation of entropy, i.e., the thermal displacement (9). Sometimes, highly accomplished scientists in their fields and even some thermodynamicists, do not fully comprehend the essence of the Second law of thermodynamics, and misrepresent the elusive thermal phenomena, let alone the surrounding publicity and even hype, resulting in speculative challenges of the Second Law of thermodynamics (4).
The authors of “Heat flowing from cold to hot ...” (1) present a very creative physical application, albeit inefficient and impractical, to self sub-cool a hot body relative to intermediate ambient temperature using its own initial, thermal work potential stored within. However, the results have been presented in somewhat spectacular and misleading ways, including dramatic news releases followed by wide publicity in a number of media, as evidenced by a Google search titled “Thermodynamic magic enables cooling without energy consumption,” or “Heat flowing from cold to hot without external intervention.” The following authors’ statements instigated the follow up wide publicity bordering with magics: “Intriguingly, the process initially appears to contradict the fundamental laws of physics … appear at first sight to challenge the second law of thermodynamics … Theoretically, this experimental device could turn boiling water to ice, without using any energy … With this very simple technology, large amounts of hot solid, liquid or gaseous materials could be cooled to well below room temperature without any energy consumption … At first sight, the experiments appear to be a kind of thermodynamic magic, thereby challenging to some extent our traditional perceptions of the flow of heat… etc.". The unusually widespread media coverage, implying magical phenomena, is mostly due to the lack of full comprehension of the still elusive Second Law of thermodynamics and subtle issues related to thermal phenomena.
INTRODUCTION ( above and at: arXiv:2001.05991 )
SELF COOLING OF HOT BODY AND CARNOT CYCLE LIMITATIONS
The cooling (Stage 1) and sub-cooling (Stage 2) of a hot body
Comments on “Relations to the second law of thermodynamics (1)”
HEAT IS TRANSFERRED FROM HOT TO COLD WITHOUT EXCEPTION
THERMAL TRANSFORMER AND TEMPERATURE OSCILLATORS
DISCUSSIONS AND CONCLUSIONS
Summary of the fundamentally false claims in (1):
1. “Heat flow from cold to hot without external intervention, and without any source of power,” is false claim since the sub-cooling the body below ambient temperature by a Peltier element (Fig. 2), Stage 2(C) process, was driven by the “external intervention” using electrical work retrieved from stored EM energy in the inductor (external to the Peltier element), stored in the prior Peltier generation process, Stage 1(G), while cooling the body to ambient-temperature. There is nothing miraculous in Stage 1(G) power generation process, and the EM energy stored is indeed an “external intervention” by all standards of thermodynamics, when used in Stage 2(C) Peltier cooling process, see Fig. 2.
2. “Direct heat transfer from cold to hot in the Peltier TE element,” is false claim since the heat cannot actually transfer from cold to hot (would be destruction of entropy and violation of the Second Law). It only can be transported with material medium (a refrigerant or electron stream) while temperature of the medium is transformed by work, increased or decreased to drive heat transfer as desired (as in all thermal-power, cooling or heat pump devices). Heat transfer (from hot to cold only) should not be confused with transport of thermal energy (from any to any temperature level). The heat is actually transferred from the subcooled body to the even lower temperature of the Peltier cold end-plate, and after being adiabatically transported with temperature increase by electron stream (similar to a refrigerant medium transport and compression), the heat is then actually transferred from higher temperature of the Peltier hot end-plate to the lower temperature of the ambient air, see Fig. 1 & 3. There are no reported temperature measurements of the Peltier cold and hot end-plates (1), to compare with hot body and ambient temperatures, respectively (regardless how small temperature difference was). The authors might be deceived by negligibly small inductor energy (smaller than 0.01% of transported heat, but due to low Carnot’s and extremely low experimental irreversible efficiencies) and mistakenly thought “that some miraculous flow of heat from cold to hot is taking place in Peltier-inductor circuit without external or internal intervention.”
3. The “thermal inertia” is false claim since the underdamped oscillations were driven by external, non-thermal but adiabatic “inductor magnetic inertia,” driving temperature oscillations in Peltier element, followed by dissipative, non-inertial per se, heat transfer oscillations. Only if the work potential is not fully dissipated (as is during actual, direct heat transfer), but if it is extracted and stored to provide adiabatic, non-thermal inertia to force temperature oscillations followed by non-inertial heat transfer oscillations or only sub-cooling as desired.
4. “Use of inductor is essential,” is false claim since, although the high efficiency of the superconducting coil was beneficial, but the thermal oscillations are not essential, actually not desirable at all, since the first half of the cycle (Stages 1 & 2 on Fig. 2) provide the maximum sub-cooling, the oscillations being non-essential (actually adverse) by-product of the inductor-Peltier circuit oscillations. The same effect could have been achieved with any work-energy storage if efficient. Supper-conductive inductor provides high efficiency and “magnetic inertia” (not “thermal inertia”), also passive reversal of stored energy (capacitor switching would be required) to run Peltier element as a cooling device. The sub-cooling could be achieved with other work-storage devices, therefore the inductor per se is not essential, see Fig. 2 that demonstrate subcooling processes in general.
1. A. Schilling, X. Zhang and O. Bossen. Heat flowing from cold to hot without external intervention by using a “thermal inductor”. Science Advances, 2019. DOI: 10.1126/sciadv.aat9953.
2. Thermodynamic magic enables cooling without energy consumption, by University of Zurich, 19 April 2019 News release, https://phys.org/pdf474877749.pdf * https://phys.org/news/2019-04-thermodynamic-magic-enables-coolingenergy.html (accessed on 7 July 2019).
3. A. Schilling, Bending (But Not Breaking) The Second Law Of Thermodynamics Using A “Thermal Inductor”, Science Trends, May 2, 2019. https://sciencetrends.com/bending-but-not-breaking-the-second-law-of-thermodynamics-using-a-thermal-inductor/ (accessed on 7 July 2019)
4. V. Capek, D.P. Sheehan, Challenges to the Second law of Thermodynamics: Theory and Experiment, (Fundamental Theories of Physics), Springer, Dordrecht, Netherlands, 2005. 366 pp. ISBN 1-4020-3016-0.
5. R. Clausius. The Mechanical Theory of Heat (English translation by W.R. Browne), McMillan and Co., London 1879. Available online: https://sites.google.com/site/professorkostic/energy-environment/clausius-theory-of-heat (accessed on 7 July 2019).
6. M. Kostic, Nature of Heat and Thermal Energy: From Caloric to Carnot’s Reflections, to Entropy, Exergy, Entransy and Beyond. Entropy 2018, 20(8), 584; https://doi.org/10.3390/e20080584 (accessed on 7 July 2019).
7. S. Carnot, Reflections on the Motive Power of Heat; Thurston, R.H., Translator; Chapman & Hall, Ltd.: London, UK, 1897; Available online: https://sites.google.com/site/professorkostic/energy-environment/sadi-carnot (accessed on 7 July 2019).
8. M. Kostic, Revisiting the Second Law of Energy Degradation and Entropy Generation: From Sadi Carnot’s Ingenious Reasoning to Holistic Generalization. AIP Conf. Proc. 2011, 1411, 327. [Google Scholar] [CrossRef] (accessed on 7 July 2019).