Numerical study of the pressure drop phenomena in wound woven wire matrix of a Stirling regenerator

Friction pressure drop correlation equations are derived from a numerical study by characterizing the pressure drop phenomena through porous medium of both types namely stacked and wound woven wire matrices of a Stirling engine regenerator over a specified range of Reynolds number, diameter and porosity. First, a finite volume method (FVM) based numerical approach is used and validated against well known experimentally obtained empirical correlations for a misaligned stacked woven wire matrix, the most widely used due to fabrication issues, for Reynolds number up to 400. The friction pressure drop correlation equation derived from the numerical results corresponds well with the experimentally obtained correlations with less than 5% deviation. Once the numerical approach is validated, the study is further extended to characterize the pressure drop phenomena in a wound woven wire matrix model of a Stirling engine regenerator for a diameter range from 0.080 to 0.110 mm and a porosity range from 0.472 to 0.638 within the same Reynolds number range. Thus, the new correlation equations are derived from this numerical study for different flow configurations of the Stirling engine regenerator. The results indicate flow nature and complex geometry dependent friction pressure drop characteristics within the present Stirling engine regenerator system. It is believed that the developed correlations can be applied with confidence as a cost effective solution to characterize and hence to optimize stacked and woven Stirling engine efficiency in the above specified ranges

Numerical study of the heat transfer in wound woven wire matrix of a Stirling regenerator

Nusselt number correlation equations are numerically derived by characterizing the heat transfer phenomena through porous medium of both stacked and wound woven wire matrices of a Stirling engine regenerator over a specified range of Reynolds number, diameter and porosity. A finite volume method (FVM) based numerical approach is proposed and validated against well known experimentally obtained empirical correlations for a random stacking woven wire matrix, the most widely used due to fabrication issues, for Reynolds number up to 400. The results show that the numerically derived correlation equation corresponds well with the experimentally obtained correlations with less than 6% deviation with the exception of low Reynolds numbers. Once the numerical approach is validated, the study is further extended to characterize the heat transfer in a wound woven wire matrix model for a diameter range from 0.08 to 0.11 mm and a porosity range from 0.60 to 0.68 within the same Reynolds number range. Thus, the new correlation equations are numerically derived for different flow configurations of the Stirling engine regenerator. It is believed that the developed correlations can be applied with confidence as a cost effective solution to characterize and hence to optimize stacked and wound woven wire Stirling regenerator in the above specified ranges

Experimental and numerical flow investigation of Stirling engine regenerator

This paper presents both preliminary experimental and numerical studies of pressure drop and heat transfer characteristics of Stirling engine regenerators. A test bench is designed and manufactured for testing different regenerators under oscillating flow conditions, while three-dimensional (3-D) numerical simulations are performed to numerically characterize the pressure drop phenomena through a wound woven wire matrix regenerator under different porosity and flow boundary conditions. The test bench operating condition range is initially determined based on the performance of the commercial, well-known Stirling engine called WhisperGen™. This oscillating flow test bench is essentially a symmetrical design, which allows two regenerator samples to be tested simultaneously under the same inflow conditions. The oscillating flow is generated by means of a linear motor which moves a piston in an oscillatory motion. Both the frequency and the stroke of the piston are modified to achieve different test conditions. In the numerical study, use of a FVM (finite volume method) based CFD (computational fluid dynamics) approach for different configurations of small volume matrices leads to a derivation of a two-coefficient based friction factor correlation equation, which could be later implemented in an equivalent porous media with a confidence for future regenerator flow and heat transfer analysis

Experimental and numerical flow investigation of Stirling engine regenerator

This paper presents both preliminary experimental and numerical studies of pressure drop and heat transfer characteristics of Stirling engine regenerators. A test bench is designed and manufactured for testing different regenerators under oscillating flow conditions, while three-dimensional (3-D) numerical simulations are performed to numerically characterize the pressure drop phenomena through a wound woven wire matrix regenerator under different porosity and flow boundary conditions. The test bench operating condition range is initially determined based on the performance of the commercial, well-known Stirling engine called WhisperGen™. This oscillating flow test bench is essentially a symmetrical design, which allows two regenerator samples to be tested simultaneously under the same inflow conditions. The oscillating flow is generated by means of a linear motor which moves a piston in an oscillatory motion. Both the frequency and the stroke of the piston are modified to achieve different test conditions. In the numerical study, use of a FVM (finite volume method) based CFD (computational fluid dynamics) approach for different configurations of small volume matrices leads to a derivation of a two-coefficient based friction factor correlation equation, which could be later implemented in an equivalent porous media with a confidence for future regenerator flow and heat transfer analysis