Near-field radiative heat transfer between macroscopic planar surfaces

TL;DR

This paper reports experimental measurements of near-field radiative heat transfer between macroscopic sapphire plates, confirming theoretical predictions and demonstrating heat transfer across small vacuum gaps without contact.

Contribution

First experimental verification of near-field radiative heat transfer between macroscopic surfaces over a range of separations and temperatures.

Findings

Heat transfer increases as gap decreases.

Agreement with theoretical models is observed.

Evanescent waves enable heat transfer without contact.

Abstract

Near-field radiative heat transfer allows heat to propagate across a small vacuum gap in quantities that are several orders of magnitude greater then the heat transfer by far-field, blackbody radiation. Although heat transfer via near-field effects has been discussed for many years, experimental verification of this theory has been very limited. We have measured the heat transfer between two macroscopic sapphire plates, finding an increase in agreement with expectations from theory. These experiments, conducted near 300 K, have measured the heat transfer as a function of separation over mm to $\mu$m and as a function of temperature differences between 2.5 and 30 K. The experiments demonstrate that evanescence can be put to work to transfer heat from an object without actually touching it.