Design Optimization and Analysis of Thermoacoustic Refrigerators

Abstract

Thermoacoustic refrigeration, a novel technology, uses eco-friendly gases like helium, air or the mixture of noble gases as working substances in the absence of moving parts. The design, optimization and analysis of thermoacoustic refrigerators using helium and air as oscillating gases are discussed. Pure helium is chosen since it is proven as the best and economical working gas compared to the alternate pure or the mixture of noble gases. Air is chosen since it is abundant in nature and the least cost of the pressurized dry air cylinders. The design optimization strategies discussed in this paper serve as a guide for aspiring researchers in the design and development of thermoacoustic coolers. Cooling power as a function of stack diameter is discussed. Theoretical results of the optimized coolers are compared with DeltaEC simulation results for validation and are in agreement with each other.

Theoretical evaluation of stack-based thermoacoustic refrigerators

“…In this section the design and optimization of the stack, cold and ambient heat exchangers having spiral geometry with 85% porosity to minimize acoustic field disturbances to improve cooler performance compared to 75% porosity is discussed [7,8]. The geometry and cross section of the stack and heat exchangers is same except the length.…”

“…It is found that the ambient heat exchanger rejects heat nearly twice the heat supplied by the cold heat exchanger [4,5,15]. Hence, (7) 2x 1 = 2P a sin(cx) ρuω the length of the ambient heat exchanger l 2 is equal to 2l 4 . The normalized critical temperature gradient Γ calculated for both helium and air for the four SLCC are found to be less than one (Table 6), confirms the spiral stack behaves as refrigerator [4,5,13,[15][16][17].…”

“…Also, the performance of the spiral geometry expressed in terms of half stack spacing distance y and thermal penetration depth δ k is on par with parallel plate geometry at y = 2δ k for helium and y = δ k for air [6]. The cooling capacity of the refrigerator increases with increase in size of the refrigerator and at the same time performance of the stack and refrigerator decreases, and vice versa [7]. The stack center position X is the distance between the loudspeaker position and the mid-point of the stack length l 3 .…”

“…In this paper, an attempt is made to explain the method of optimizing stack-heat exchangers system in terms of the normalized stack length and center positions with helium and air considering the performance of the stack, cooling power and power density of the refrigerator compared to the published literature [5][6][7][8]. The spiral geometry is chosen for the stack-heat exchangers system because of its simplicity and ease of construction during fabrication compared to other geometries (parallel plate, circular, pin array, etc.)…”

“…Hence, the presence of the small length of the stack will offer minimum resistance for the oscillating gas, leading to improvement in the performance of the stack as found in the published literature [4,8]. In the published literature [3,4,7,8], the stack-heat exchangers system is optimized by choosing the stack length and center position merely based on the highest performance of the stack. This makes the device compact and improves power density with poor cooling capacity of the refrigerator.…”