Probe for Measuring Soil Specific Heat Using A Heat‐Pulse Method

TLDR

Temperature rise measured a short distance from a line heat source can determine volumetric specific heat of soil, which is linearly related to the inverse of that rise. This note describes the construction and performance of a device that measures specific heat using the line source method. The device consists of two 0.813 mm diameter, 28 mm long hypodermic needles spaced 6 mm apart, one serving as a heater and the other as a thermocouple to record temperature rise from heat pulses. The device achieved a coefficient of variation of about 1 % for specific heat on replicate samples, allowing detection of water‑content changes as small as 0.01 % in nonswelling soils.

Abstract

Abstract Temperature rise, measured a short distance from a line heat source, can be used to determine the volumetric specific heat of soil and other materials. Volumetric specific heat is linearly related to the inverse of the temperature rise. The purpose of this note is to describe the construction and performance of a device for measuring specific heat using the line source method. The device was constructed from two hypodermic needles, 0.813 mm in diam. and 28 mm long, and spaced 6 mm apart. One needle contained a heater and the other a thermocouple. The temperature rise from heat pulses given to the heater were measured with the thermocouple. The coefficientof variation (CV) of specific heat on replicate samples was around 1%. Since water is the main variable component of the specific heat in nonswelling soil, changes in water content might be resolved to 0.01 or better in nonswelling soils.