Advances in Radiative Heat Transfer: Bridging Far-Field Fundamentals and Emerging Near-Field Innovations

Abstract

Radiative heat transfer plays a pivotal role in many applications across various length scales, with its behavior significantly altering as systems change from the far-field to the near-field regime. In the far-field, radiative heat transfer is governed by traditional laws such as Planck's and Stefan–Boltzmann's laws, which assume that the gap between objects involved in radiative exchange is larger than the thermal wavelength (λ_th), limiting the energy transfer to propagating electromagnetic waves. However, in the near-field, where distances are smaller than the λ_th, evanescent wave coupling enables heat transfer rates that exceed the blackbody limit by several orders of magnitude. This near-field enhancement opens new avenues for nanoscale thermal management, energy harvesting, and radiative cooling applications. This review synthesizes the key developments in radiative heat transfer theories, experimental advancements, and practical applications, spanning from early traditional studies to modern innovations leveraging fluctuational electrodynamics. Material-specific mechanisms, such as surface phonon polaritons, and their role in enhancing radiative heat transfer are also explored while integrating machine learning techniques to optimize near-field systems. By highlighting these mechanisms and exploring emerging research directions, this work aims to inspire new researchers to enter this dynamic field and provide a roadmap for advancing next-generation technologies in energy efficiency and nanoscale thermal management.