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This paper deals with the design and analysis of a quarter-wavelength, 10 W capacity, thermoacoustic refrigerator using short stack boundary layer approximation assumptions. The effect of operating frequency on the performance of the refrigerator is studied using dimensional normalization technique. The variation of stack diameter with average gas pressure and cooling power is discussed. The resonator optimization is discussed and the calculation results show a 9% improvement in the coefficient of performance and 201% improvement in power density for the optimized quarter-wavelength resonator compared to published optimization studies. The optimized resonator design is tested with DeltaEC software and the results show better performance compared to past established resonator designs.

Thermoacoustic refrigerators are environmentally friendly cooling systems that use no refrigerants. Optimization of the performance of any cooling system is crucial for an efficient energy management. Most of the optimization techniques in thermoacoustic systems utilized to date involved experimental and numerical parametric studies which are generally limited to the variations of the parameters to be optimized at discrete values. This study reports on the optimization of a thermoacoustic refrigerator using multi-objective genetic algorithm (MOGA). The study introduces the ability of MOGA to optimize four different variables which are length of stack, center position of stack, blockage ratio and drive ratio simultaneously. The four variables are optimized to achieve the two objectives; a maximum cooling and minimum acoustic power required at the stack and provide the optimum coefficient of performance, COP. The results show that the optimum COP = 1.35 with a cooling power of Q_c = 6.57 W, acoustic power of W_n = 4.86 W and with the resonator diameter of D = 3.8 cm.

Although thermoacoustic devices comprise simple components, the design of these machines is very challenging. In order to predict the behavior and optimize the performance of a thermoacoustic refrigerator driven by a standing-wave thermoacoustic engine, considering the changes in geometrical parameters, two analogies have been presented in this paper. The first analogy is based on CFD analysis where a 2D model is implemented to investigate the influence of stack parameters on the refrigerator performance, to analyze the time variation of the temperature gradient across the stack, and to examine the refrigerator performance in terms of refrigeration temperature. The second analogy is based on the use of an optimization algorithm based on the simplified linear thermoacoustic theory applied for designing thermoacoustic refrigerators with different stack parameters and operating conditions. Simulation results show that the engine produced a high-powered acoustic wave with a pressure amplitude of 23kPa and a frequency of 584Hz and this wave applies a temperature difference across the refrigeration stack with a cooling temperature of 292.8K when the stacks are positioned next to the pressure antinode. The results from the algorithm give the ability to design any thermoacoustic refrigerator with high performance by picking the appropriate parameters.

Environmental regulations have turned their focus on controlling and mitigating air emissions that contribute to abundant air pollution. The primary pollutants found in air emissions from stack discharges are NO_x, SO_x, particulates and smog. With continued federal action by the EPA, coupled with action from state and local regulatory agencies, mitigation of air pollution containing harmful pollutants can be achieved to a certain scale. This chapter will focus on the harmful effects of sulfur dioxide (SO₂), considered the most harmful intentionally discharged air pollutant to the environment. Due to its impact in the form of acid rain and, on a larger scale, ozone depletion, SO₂ mitigation is a high priority. Additionally, methods and equipment used as well as being developed for use will be discussed for their ability to effectively treat stack discharges and mitigate SO₂ pollution.