A tomography-based effective thermal conductivity model for ceramic fiber insulation. (October 2020)

• Record Type: Journal Article
• Authors: Curran, David; Porter, Jason M.
• Is Part Of: International journal of heat and mass transfer. Volume 160(2020)
• Publication Date: 2020-10
• Subjects: Radiation heat transfer -- Fibrous ceramic -- Thermal conductivity -- Porous media -- Tomography; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2020.120224
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: Tomographic reconstruction informs fiber size and orientation distributions. Critical parameters of manufacture are identified by optimizing distributions. Tortuosity-weighted conduction highlights direction of thermal conductivity. Radiation and conduction model predict thermal conductivity from 300-1673K. Abstract: Ceramic fiber insulation is widely used in thermal systems due to its high temperature limits and light weight. In high temperature applications, radiation is the main mechanism of heat transfer in these materials due to high porosity (greater than 95 %), and orientation of the fibers in the construction of the insulation. A combined radiation and conduction computational model has been developed to calculate thermal conductivity in ceramic fiber materials using the Rosseland diffusion approximation to evaluate thermal radiation transfer, and a tortuosity-weighted effective thermal conductivity to evaluate gas and solid phase conduction. Tomographic reconstructions of sample insulation material were analyzed to determine fiber size and orientation distributions as well as tortuosity and volume fraction of the solid and void fraction. The model is validated by manufacturer data. Together, the conduction and radiation model accurately predicted effective thermal conductivity of ceramic fiber materials in the temperature range of 300–1673 K. The tortuosity-weighted conduction approach allows the model to capture the directional dependence of thermal conductivity in the highly an-isotropic fibrous structure. Critical parameters of fibrous ceramics to maximize insulating properties are also identified.