Experimental investigation of reciprocity of temperature response across two layer samples by flash method.

The reciprocity of heat transfer is a fundamental principle. However, there are few experimental studies to verify this principle. In this paper, we measured two layer samples made of ordinary metal by the laser flash method to verify the reciprocity principle. We heated and detected the different surfaces of each two layer sample to observe the reciprocal response. We also made use of areal heat diffusion time to analyze the temperature rise of two layer samples to enable to extend analysis for future multi-layer samples. This study is an important starting point to discuss whether characteristic materials obey the reciprocal principle.