A critical review of non-Fourier heat transfer theories with phase lag in bio-heating: Explaining the variations in reported phase lag coefficients

Accurate modeling of bio-heat conduction is critical in many disciplines where thermal processes play a decisive role in outcomes. As these applications demand precise temperature control in complex biological materials, the limitations of classical Fourier heat conduction have led researchers to explore advanced non-Fourier models. The aim of this study is to establish a convergence among non-Fourier bioheating investigations, since after three decades of research, no consensus has yet been achieved regarding the reported values of phase lag parameters. To this end, 110 papers published over the past 30 years employing the Cattaneo–Vernotte (single phase lag), dual phase lag, and three phase lag models were systematically reviewed. The numerical values of the phase lag terms and the reasons provided for their selection were critically examined and compared. The findings revealed a lack of consistency across the literature, with reported phase lag values ranging from near zero up to 32 s. Studies reporting excessively large phase lag values were found to face substantial theoretical and experimental challenges, whereas more reliable results were consistently obtained in works adopting smaller phase lag values. It is therefore concluded that clearer experimental validation and standardization are required to justify the application of non-Fourier models in bioheat transfer analyses and to achieve convergence in this field.