Research Papers

What is Heat?*

[+] Author and Article Information
Gian Paolo Beretta

Università di Brescia,
Brescia, Italy

Elias P. Gyftopoulos

Massachusetts Institute of Technology,
Cambridge, MA 02139

*Proceedings of the Winter Annual Meeting of the American Society of Mechanical Engineers, Dallas, TX, November 25–30, 1990, in Education in Thermodynamics and Energy Systems, edited by G. Tsatsaronis, M. J. Moran, and A. Bejan, ASME book G00567, AES-Vol. 20, pp. 33–41 (1990). Reprinted with permission.

J. Energy Resour. Technol 137(2), 021006 (Mar 01, 2015) (8 pages) Paper No: 06-BerettaGyftopoulos-AS; doi: 10.1115/1.4026382 History: Online November 18, 2014

We define heat as a particular kind of nonwork interaction that involves only energy and entropy transfers, and that is entirely distinguishable from work. The existence of heat interactions is a consequence of the first and second laws of thermodynamics. The requirement that heat be entirely distinguishable from work implies strict conditions on the end states of the interacting systems, and guarantees a definite relation between such states and the energy and entropy transfers. We illustrate these conditions by using energy versus entropy graphs. Many experiences can be represented as heat interactions, including the exchanges between two black bodies at temperatures that differ infinitesimally. We discuss the latter point in a companion paper at this conference.

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