An analytically based method to estimate the effective thermal diffusivity of a heat pipe

Abstract

An analytically based method is proposed to estimate the equivalent thermal diffusivity (α) of a heat pipe. This novel method, which enables real-time screening, features simple, fast, inexpensive and accurate characteristics in obtaining the corresponding α value. Different from the traditional Angstrom method, which uses a sinusoidal pulse heating source for measuring the offset of two separate waves triggered in an intermittent time span; the proposed method merely uses a water bath as the heating source with the derived closed-form solution as a core computing algorithm, and the correct α value can be obtained. The examination process only takes less than 30 s and can be deployed in production lines for real-time screening. The closed-form analytical solution is associated with an infinite power series and is validated with heat pipes of 6 mm in diameter and 260 mm in length. The equivalent thermal diffusivity of the heat pipe is 0.00382 m2 s−1, which is about 35 times higher than copper and 3.6 times higher than graphite. The analytical predictions are in line with experimental results for the transient temperature rise of the heat pipe.