Narrow Results

This paper deals with the basic insight of thermoacoustic refrigeration concepts, and the working principle, history and the role of linear thermoacoustic theory in designing a thermoacoustic refrigerator system are discussed. Resonator design optimization procedure for a 10W cooling power thermoacoustic refrigerators is discussed. The optimized resonator designs proposed in this paper are found to be efficient compared to published resonator designs. The effects of drive ratio on the theoretical performance by varying dynamic pressure amplitude from 0.2 bar to 0.4 bar in the steps of 0.05 bar on the optimized resonator designs are discussed. Performance simulation results for the optimized resonator designs using DeltaEC software are discussed. Simulation results are in agreement with theoretical results.

In this paper, the design of a loudspeaker driven 10W cooling power stack-based thermoacoustic refrigerator at 3% drive ratio for a temperature difference of 80K using helium as working fluid is discussed. The refrigerator is designed using linear thermoacoustic concepts. Using linear thermoacoustic equations, a theoretical minimum cold heat exchanger temperature is estimated at 75% porosity of stack-heat exchanger system. This paper focuses on the comparative analysis of the present design with the similar 10W thermoacoustic refrigerator designs found in the literature. The theoretical performance comparison of TSDH, TDH and CDH resonators designed at 2% and 3% drive ratio is discussed. The resonator designs are validated using DeltaEC software and the results are discussed. DeltaEC simulation results show that the diameter of the vibrating diaphragm of the loudspeaker equal to the diameter of the stack-heat exchangers system has higher electroacoustic efficiency (74.7%) and better performance compared to the smaller diaphragm (42.6%) used in the past research.

In this paper, the construction and performance of the 10W cooling power thermoacoustic refrigerators designed for a temperature difference of 120 K at 3% drive ratio are discussed. The construction and assembly procedure of the optimized thermoacoustic refrigerator components viz. spiral stack, heat exchangers, 0.28$\lambda$-taper, small diameter tube and divergent section with hemispherical end (TSDH) and 0.24$\lambda$-taper and divergent section with hemispherical end (TDH) resonator designs and loudspeaker found in the published literature, and instrumentation are discussed. The performance of the 0.28$\lambda$-TSDH, and 0.24$\lambda$-TDH resonator designs, and the uncertainties involved in the experimental measurements are discussed. Both the resonator designs show good behavior. A decent low temperature of $-$11.3${}^{\circ }$C and $-$8.7${}^{\circ }$C at 10W cooling power is achieved at the cold heat exchanger for the 0.28$\lambda$-TSDH and 0.24$\lambda$-TDH resonator designs, respectively. The comparative analysis of the experimental results with the theoretical and DeltaEC results is discussed.

In this paper, the design of 50 W thermoacoustic refrigerators operating with air as working substance at 10 bar pressure and 3% drive ratio for a temperature difference of 28 K is described. The design strategies discussed in this paper help in design and development of low cost thermoacoustic coolers compared to helium as the working substance. The design and optimization of spiral stack and heat exchangers, and the promising 0.2$\lambda$ and 0.15$\lambda$ resonator design with taper and divergent section with hemispherical end are discussed. The surface area, volume, length and power density of the hemispherical end design with air as working substance is found better compared to the published 10 and 50 W coolers using helium as the working substance. The theoretical design results are validated using DeltaEC software simulation results. The DeltaEC predicts 51.4% improvement in COP (1.273) at the cold heat exchanger temperature of $-2.7^{\circ }$C with air as working substance for the 50W 0.15$\lambda$TDH resonator design compared to the published 50W 0.25$\lambda$TDH resonator design with helium as working substance.

This paper deals with the design of thermoacoustic refrigerators using linear thermoacoustic theory. The refrigerator components are designed at 3% drive ratio by considering the practical limitations of providing sufficient spacing for attaching the loudspeaker to the resonator tube and accommodating instrumentation. The effects of spiral stack spacing in terms of thermal penetration depth on the theoretical performance of refrigerator using helium and air as working substances are discussed. The quarter-wavelength resonator designs with taper and divergent section terminated with hemispherical end are optimized with helium and air for better performance. Theoretical results are validated with DeltaEC software results and are in agreement with each other. Helium shows better performance compared to air but lacks power density. The DeltaEC predicts COP 0.514 at the cold heat exchanger temperature of $-30^{\circ }$C with helium compared to air (COP 0.616 at $8.8^{\circ }$C) for the 50W cooling power 100mm diameter quarter-wavelength resonator designs.