Thermal Conductivity Measurements on Inert Media using Internal Calorimetry

Abstract

INTERNAL calorimetry¹, developed for the measurement of blood flow, is basically a method for thermal conductivity determination. It uses a fine-gauge heated thermocouple embedded in the organ or medium under examination. In simple media a steady heating current applied to the filament raises the temperature recorded by the thermocouple. Temperature equilibration is rapid. Heat exchanges² are governed by Carslaw's equation³: I²R = 4π.r.θ.k, where k is the thermal conductivity of the medium, I the heating current, R the resistance of the heater, r the radius of a thermodynamically equivalent sphere and θ the temperature increment. Thus the relation between I² and θ is linear when k is constant; 4πr/R is a constant for any given recorder and constitutes its standardization factor (F), the experimental determination of which has been fully described elsewhere⁴.