Performance evaluation of a standing wave thermoacoustic refrigerator using normalized sensitivity coefficients

The sensitivity analysis using normalized sensitivity coefficient (NSC) can be used to identify important model parameters affecting the device performance by allowing one-to-one comparison. The results are highlighted in the form of order of magnitudes change in output for a unit change in input variable. In this study, the sensitivity analysis of a small capacity standing wave thermoacoustic refrigerator (SWTAR) has been performed using NSC. Specialized tool DELTAEC has been used to generate the results for the subsequent sensitivity analysis. Three key performance parameters, i.e., temperature difference achieved (ΔT), coefficient of performance (COP), and relative coefficient of performance (COPR) have been analyzed for perturbations in number of device variables, namely, oscillating pressure amplitude, two different stack material properties and four stack geometric parameters, i.e., stack length, stack center position, stack plate thickness, and half stack spacing. Sensitivity results are obtained for a wide range of mean operating pressures (P_m), mean operating temperature (T_m), and drive ratios (DRs). It has been found that performance parameters are most sensitive to the perturbations in oscillating pressure amplitude and least affected by the perturbations in the stack length. With respect to the oscillating pressure amplitude, maximum NSC of 24.12 has been reported for ΔT at mean pressure of 5 bar.