Improving the specific cooling capacity of a thermoacoustic refrigerator requires either increasing the cooling capacity and/or reducing the total volume. The cooling capacity is a function of the delivered acoustic power delivered to the thermoacoustic core. Hence, reducing the acoustic power losses will lead to an increase in the cooling capacity. The first two objectives of the project aim to quantify the acoustic power losses due to both turbulence generation and flow discontinuities. The third objective is to design a compact acoustic driver to reduce the total volume of thermoacoustic refrigerators.

To achieve the above stated objectives, the project is divided into three work packages (WP) detailed in the following sections.

This WP focuses mainly on understanding the effects of changing flow regimes on acoustic energy losses (i.e. viscous resistance coefficient). The scientific approach adopted in this WP is a combined experimental-numerical approach to enrich our understanding of the physics underlying this problem. The proposed experimental activities span the macro (acoustic measurements) and micro (flow dynamics) aspects of the problem.  The activities of this WP are organized into three main tasks, which are:

• T1.1: Acoustic transfer matrix and flow regimes;
• T1.2: Mechanism of acoustic energy losses;
• T1.3: Numerical simulations of acoustic flow at different flow regimes.

The milestones of this work package are:

• M1.1: Developing an experimental setup capable of achieving high acoustic velocity amplitudes and allowing for measuring the transfer matrix;
• M1.2: Defining the numerical model that exhibits closer agreement with the experimental results, based on the results obtained in T1.3.

In this work package, the effects of discontinuities (cross-section change or direction) on acoustic energy losses (known as minor losses) will be investigated. A combined experimental-numerical approach will be adopted to provide a clear understanding of the addressed problem. Also, the proposed experimental activities provide the possibility of adopting both the phenomenological approach (flow dynamics) and the macro approach (microphone measurements) in analyzing the outcomes. The activities of this WP are organized into three main tasks, which are:

• T2.1: Measuring the minor loss coefficient of different flow discontinuities;
• T2.2: Mechanism of acoustic energy losses;
• T2.3: Numerical simulations of acoustic flow through discontinuities.

The milestones of this work package are:

• M2.1: Providing a glossary for the values of  for different discontinuities configurations.

This work package aims to design, fabricate, and test a compact and symmetrical acoustic source for thermoacoustic applications. The developed source will be a milestone for a new generation of compact thermoacoustic refrigerators as it will significantly increase the specific cooling capacity. The activities of this WP are organized into three main tasks, which are:

• T3.1: Design and manufacturing of double-acting acoustic source;
• T3.2: Measuring the performance of the developed acoustic source;
• T3.3: Integrating the acoustic source in a simple thermoacoustic refrigerator.

The milestones of this work package are:

• M3.1: Designing and manufacturing a double-acting acoustic source.