A comprehensive analysis of bioheat transport through a double layer and multilayer biological media is presented in this work. Analytical solutions have been developed for blood and tissue phase temperatures and overall heat exchange correlations, incorporating thermal conduction in tissue and vascular system, blood-tissue convective heat exchange, metabolic heat generation, and imposed heat flux, utilizing both local thermal nonequilibrium and equilibrium models in porous media theory. Detailed solutions as well as Nusselt number distributions are given, for the first time, for two primary conditions, namely, isolated core region and uniform core temperature. The solutions incorporate the pertinent effective parameters for each layer, such as volume fraction of the vascular space, ratio of the blood, and the tissue matrix thermal conductivities, interfacial blood-tissue heat exchange, tissue/organ depth, arterial flow rate and temperature, body core temperature, imposed hyperthermia heat flux, metabolic heat generation, and blood physical properties. Interface temperature profiles are also obtained based on the continuity of temperature and heat flux through the interface and the physics of the problem. Comparisons between these analytical solutions and limiting cases from previous works display an excellent agreement. These analytical solutions establish a comprehensive presentation of bioheat transport, which can be used to clarify various physical phenomena as well as establishing a detailed benchmark for future works in this area.
Characterization and regulation of isothermal surfaces are key issues in a number of thermal management devices. The surface temperature uniformity can be controlled utilizing a variable area channel heat exchanger filled with a porous medium. A comprehensive analytical investigation of forced convection through a generic variable area channel is carried out to design a compact heat exchanger in producing an isothermal surface subject to a constant heat flux, which may be required in the biological, electronics, optical, laser, manufacturing, and solidification applications. Exact solutions for the fluid and solid phases and the wall surface temperature distributions as well as the Nusselt number correlations are established while incorporating local thermal nonequilibrium and transverse conduction contributions. The channel temperature field is adjusted utilizing either an adiabatic or a constant temperature on the inclined surface. The effects of the pertinent physical parameters, such as channel inlet/outlet thickness, inclination angle, Biot number, ratio of fluid and matrix thermal conductivities, working fluid properties, and imposed heat flux, on the fluid and solid temperature fields and the isothermal surface are thoroughly investigated. The results indicate that utilizing proper pertinent parameters, an isothermal surface is achieved. The validity of the utilization of the local thermal equilibrium model is also investigated and error maps are presented.
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