METHOD OF MEASUREMENT OF COEFFICIENT OF THERMAL EXPANSION OF CONDUCTIVE LIQUIDS Russian patent published in 1997 - IPC

FIELD: thermal physics. SUBSTANCE: proposed method can be used for examination of materials in those regions of states where strong temperature dependence of coefficient of thermal expansion, for example, close to phase transitions is observed. Examined liquid filling cell with nonconductive walls is subjected to action of pressure periodically changing in time. These variations of pressure cause temperature variations in liquid recorded by means of thermocouple (or by any other means). Simultaneously electric current is passed through liquid. Frequency of oscillations of power of current coincides with frequency of variations of pressure. Phase of oscillations of electric current is shifted relative to variations of pressure so that temperature variations emerging in liquid due to Joule heating will be in counterphase to temperature variations caused by periodic changes of pressure. Changing amplitude of temperature variations of current one seeks for amplitude of temperature variations in liquid be equal to zero thanks to mutual compensation of actions of periodic pressure and varying electric current. In this case coefficient of thermal expansion of examined liquid is found by formula , where α is coefficient of thermal expansion; W_~ is amplitude of variations of power of Joule heating; ν is line frequency; V is volume of examined liquid; P_~ is amplitude of pressure variations; T is absolute temperature of examined liquid. EFFECT: enhanced authenticity of method. 1 dwg