Prandtl number effect on offset fin heat exchanger performance: predictive model for heat transfer and pressure drop

Laminar models are described which predict heat transfer and pressure drop performance of liquid-cooled offset fin cold plates. These models are developed based on a surface contribution analysis of energy and momentum balances in a unit cell of the offset fin geometry. The Prandtl number was found to have a significant influence on offset fin heat transfer. The Prandtl number effects on heat transfer are categorized into two perspectives: fin perspective and array perspective. The fin perspective Prandtl number effects explain the dependence of the periodic fully developed Nusselt number on Prandtl number. The array perspective is analogous to the thermal entry length perspective in duct flow. Array perspective Prandtl number effects yield higher Nusselt numbers in the entrance region of the offset fin array. The models predict liquid-cooled experimental data within ± 20%, as compared with heat transfer and pressure drop data for Prandtl number ranging from 0.7 to 150 and Reynolds number from 10 to 2000.