POTENTIALITY OF INSTABILITY OF A THERMAL SYSTEM CONTAINING 2 TEMPERATURES OF REFERENCE

This paper deals with thermal instabilities occurring in a mixed conve ction phenomenon for a flow in a uniformly heated horizontal duct. The se instabilities manifest themselves through the appearance of large a mplitude temporal fluctuations in the wall temperature. The physical m echanism governing these instabilities has been described elsewhere, s o here a thermodynamical concept is proposed which allows justificatio n of the occurrence of such fluctuations. This concept is based upon t he representative temperatures of the system and the reference tempera tures, It is shown how a system which is represented by only one tempe rature, and containing two reference temperatures. adopts a non-statio nary behaviour in order to eliminate sporadically one of the two refer ence temperatures. (C) 1997 Elsevier Science Ltd.