Numerical Thermal Analysis and 2-D CFD Evaluation Model for An Ideal Cryogenic Regenerator.

Natheer Almtireen,Jürgen J Brandner,Jan G Korvink

doi:10.3390/mi11040361

Natheer Almtireen, Jürgen J Brandner + Show 1 more

Open Access

https://doi.org/10.3390/mi11040361

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Abstract

Regenerative cryocoolers such as Stirling, Gifford–McMahon, and pulse tube cryocoolers possess great merits such as small size, low cost, high reliability, and good cooling capacity. These merits led them to meet many IR and superconducting based application requirements. The regenerator is a vital element in these closed-cycle cryocoolers, but the overall performance depends strongly on the effectiveness of the regenerator. This paper presents a one-dimensional numerical analysis for the idealized thermal equations of the matrix and the working gas inside the regenerator. The algorithm predicts the temperature profiles for the gas during the heating and cooling periods, along with the matrix nodal temperatures. It examines the effect of the regenerator’s length and diameter, the matrix’s geometric parameters, the number of heat transfer units, and the volumetric flow rate, on the performance of an ideal regenerator. This paper proposes a 2D axisymmetric CFD model to evaluate the ideal regenerator model and to validate its findings.

Highlights

The growth in a large number of low-temperature applications led to huge developments in cryogenics and cryocoolers over the past few decades
A MATLAB R code was developed to study the thermal interaction between the working gas and the matrix material in a regenerator element, a component of a closed-cycle regenerative cryocooler
The presented algorithm was a discretization of the ideal regenerator thermal equations

Summary

Introduction

The growth in a large number of low-temperature applications led to huge developments in cryogenics and cryocoolers over the past few decades. Analytical and numerical analyses of critical components are required for the development of more efficient pulse tube cryocoolers, to replace potentially conventional concepts in existing or emerging application fields [7,8,9,10] These numerical analyses and thorough experimental works are very significant in providing better interpretation of the thermal interaction between the working gas and the matrix material in the regenerator. This paper presents a numerical approximation for the thermal interaction between the gas and the matrix material by only solving the energy conservation equations for both the matrix and the gas; the assumptions involve uniform one-dimensional longitudinal flow, with infinite radial thermal conduction and zero longitudinal thermal conduction in the matrix It numerically solves the idealized general thermal equations for the working gas and the matrix based on finite-difference techniques and predicts the output temperature profiles for the working gas and the matrix material. Micromachines 2020, 11, 361 solves the mass, momentum, and energy equations for the porous regenerator zone and provides more accurate results to compare it with the ideal regenerator model and examine its soundness

Regenerator System

Ideal Regenerator Model and Numerical Solution

Model Convergence

Model Application

Ideal Regenerator

Conclusions