Oriented fibers stacks for thermoacoustic devices

The study aims to improve the performance of thermoacoustic engines and heat pumps. These devices are a promising solution to rising energy demand since they work with low-temperature energy sources. By introducing innovative and unconventional stacks called "oriented fibers", onset temperatures are significantly lowered compared to conventional stacks, such as the circular pores. Stability curves are employed to analyse triggering mechanisms and operational stability. The methodology is validated against experimental data of three experimental devices, with different acoustic field conditions: the standing wave, traveling wave, and hybrid device. The results reported in this paper highlight the potential of oriented fibers-based stacks to low onset temperature ratio up to 50% compared to the conventional stacks. Furthermore, while longitudinal fibers stack provides the lowest onset hot temperature, it reveals high-thermal conduction losses. This entails the presence of a trade-off between these factors in order to identify a stack configuration that maximizes efficiency. That configuration depends both on the geometrical characteristics of the devices and thermal properties of the fluid and solid part of the stack, and the input thermal power. The findings of this work provide valuable insights into optimizing the stack design for thermoacoustic devices.