Mode: Mixed
Recognising the fundamental importance of Newton’s law of cooling in convective heat transfer, people may still ask: was/is it accurate enough? The answer might vary depending on what applications and when it was/is applied to. It is noted that Newton’s 1701 paper attributed to the Law was published anonymously, (unlike his other major scientific publications). It is also known that Sir Issac Newton apparently had never used the term ‘Heat Transfer Coefficient (HTC)’, arguably the most researched and used parameter in the whole field of convective heat transfer! What do these mean in terms of the applicability/uncertainty of the law as we know it, particularly when applied to modern advanced thermal management in 2020s?
The primary issue of interest is the applicability of the cooling law for a non-isothermal wall (with non- uniform surface temperatures). A general Green’s function-based framework exists but there has been no working computational method for implementation. A first-principle analysis indicates that the law of cooling and the directly solved Green’s function are both restricted by a structural modelling limitation: a range of physically relevant and numerically resolvable length scales are missing as a consequence.
The present development effort takes a different pathway. Instead of resolving the local-local influence and response, a new Spectral Heat Transfer Coefficients (SHTC) method sets up and solves global-to-local temperature-heat flux influences for a small number of spectral modes of wall temperature disturbances in a range of physically relevant and numerically resolvable length scales.
Two aerothermal regimes (linear & nonlinear) are considered respectively. First the SHTC approach is described and applied for an incompressible flow where the energy equation is decoupled from the rest eqs, and behaves linearly. Then, the corresponding temperature field is passively dictated by the velocity field. Secondly, the methodology is extended to a nonlinear regime, where the temperature field actively interact with (rather than passively influenced by) the velocity field (as in a compressible flow).
Given the time contraint, the talk serves to provide an overview/highlight of the main findings of the following recent publications on the topic:
He, L. (2023) “Spectral Heat Transfer Coefficient for Convection”, International Journal of Heat and Mass Transfer, Vol.216, 124557 (https://doi.org/10.1016/j.ijheatmasstransfer.2023.124557).
He L. (2023) “Chapter 2 – Conjugate Heat Transfer: Some Fundamentals and Recent Progress”, Advances in Heat Transfer, Elsevier (https://doi.org/10.1016/bs.aiht.2023.02.002).
He, L. (2025) “Spectral Heat Transfer Coefficient for Thermal Design Analysis – PartI: Augmenting the Cooling Law for Non-Isothermal Wall”, ASMEJ. of TURBO. 147(6), (https://doi.org/10.1115/1.4066671). (the 2024 ASME Turbo Expo Congress Heat Transfer Best Paper Award).
He, L. (2025) “Spectral Heat Transfer Coefficient for Thermal Design Analysis – Part II: Leveraging Diabatic Wall Conditioning for Nonlinear Regime”, ASMEJ. TURBO. 147(6), (https://doi.org/10.1115/1.4066672).
Professor Li He was trained in aeronautical engineering (BSc 1982 & MSc 1984 at Beihang; Ph.D 1990 at Cambridge). He has worked in general engineering departments ofthe three oldest universities in England (Cambridge 1990- 1993, Durham 1993-2008 and Oxford 2008-2025), retiring as Statutory Chair Professor of Computational Aerothermal Engineering at Oxford. Having researched both applied and fundamental sides in Aerodynamics, Aeroelasticity and Heat Transfer, Professor He tends to take a closer look at the interplays/interactions among disciplines/components/scales in general, and those between Fluid Dynamics and Heat Transfer in particular.
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