Evaluation of soil heat conductivity with cylindrical test bodies

Different solutions of the temperature increase with time of a heated cylinder are discussed. This increase depends on cylinder geometry, heat conductivity of the medium, and on the ratio of specific heats of cylinder and medium. For compact cylinders and not too fluffy media, the temperature increase is independent of the heat capacity of the medium. This heat capacity, or the thermal diffusivity, cannot be evaluated using compact cylinders, whereas hollow cylinders or plates yield data of the product conductivity × density × specific heat. The heat transfer coefficient of liquids or gases flowing across cylinders shows a certain observed positive value when forced or free flow vanish. These transfer coefficients are explained as being caused by heat flow from the heated cylinder into a quasi-infinite non-moving medium.