Biography
Biography: L Q Wang
Abstract
Unlike the past century that was blessed with ever-abundant cheap oil, this century energy has been rated as the single most important issue faced by humanity. Over 80% of all the energy we are using today is produced in or through the form of heat. Engineering heat-transfer process and medium with super thermal performance is thus vital for addressing the terawatt challenge faced by us. Driving force for heat transfer can be direct or indirect. The former is temperature gradient with conduction, convection and radiation as its three fundamental ways of heat transport. The latter comes from cross-coupling among different transport processes in the medium and transports heat in thermal waves which can be in various forms and tunable via manipulating the cross coupling. The first part of this talk is on developing a universal relation between heat flux and temperature gradient in temperature-gradient-driven heat transfer by finding both the necessary and sufficient conditions in a systematic, rigorous way for a heat transfer process to satisfy fundamental laws like the second Law of Thermodynamics. This leads to a generalized Fourier law that provides effective means for engineering temperature-gradient-driven heat-transfer processes with super thermal performance. It is normal that two or more transport processes occur simultaneously in heat-transfer media. Examples include mass, heat, chemical, electrical and magnetic transports. These processes may couple (interfere) and cause new induced effects of flows occurring without or against its primary thermodynamic driving force, which may be a gradient of temperature, or chemical potential, or reaction affinity. Two classical examples of coupled transports are the Soret effect (also known as thermodiffusion) in which directed motion of a particle or macromolecule is driven by flow of heat down a thermal gradient and the Dufour effect that is an induced heat flow caused by the concentration gradient. While the coupled transport is well recognized to be very important in thermodynamics, it has not been well appreciated yet in the society regarding its potential of generating and manipulating thermal waves and resonance. In the second part of this talk, I will summarize our work on examining such a potential and show some unique, super features of heat transport with cross-coupling-driven thermal waves and thermal resonance from our experiments with thermal-wave fluids consisting of specially-designed multiphase materials with multi-scale inner structures of micro-, nano- and subnano- sizes.
