Modification of heat transfer concentrating model for the effective heat conductivity of particle beds within the full range of heat conductivity ratio

Predicting the heat conductivity of solid-gas particle beds precisely has great meaning on the accurate designs of corresponding thermal-systems. In this study, the heat transfer concentrating (HTC) model for the heat conductivity of particle beds is modified within the full range of heat conductivity ratio k by bed heat transfer analysis. Validations indicate the predicting precision of HTC model decreases obviously except k between 485 and 8915. Then, in the extremely high k situation, a 3D analysis model is established to consider the heat transfer by particles contact, whose contribution exceeds 2% when k reaches 40,000, indicating its significant influence. When k is low, the effect of particle diameter on the HTC phenomenon is remarkable. Finally, the complete form of modified HTC model is obtained, and the comparisons show its precision and applicability are excellent within the full range of k with the mean predicting errors lower than 10%.