Thermoacoustic refrigerator driven by a combustion-powered thermoacoustic engine - Demonstrator of device for rural areas of developing countries

This paper presents the design, construction and experimental evaluation of a demonstrator thermoacoustic refrigerator driven by a combustion-powered thermoacoustic engine. The system was developed to be a low-cost device for users based in remote and rural areas of developing countries. It employs a thermoacoustic engine/refrigerator coupling based on a travelling wave looped-tube configuration because of its relatively good thermal performance and construction simplicity. In the present demonstrator, a propane gas burner is used to simulate the thermal input from biomass combustion which is envisaged to be the source of energy for driving the system. Atmospheric air is applied as working fluid, while the operating frequency of the loop is 58.6 Hz. The location of the refrigerator is optimized experimentally to achieve the maximum cooling performance. So far, the lowest temperature achieved at the cold end of the regenerator is -3.6°C, while the maximum COPR achieved is 1.42%

Optimal design of a thermoacoustic system comprising of a standing-wave engine driving a travelling-wave cooler

This paper presents the design and optimisation of a coupled thermoacoustic system comprising of a standing wave thermoacoustic engine and a coaxial travelling wave thermoacoustic cooler in a linear configuration. The overall aim is to propose an economical design of a prototype system which could be used by people living in remote rural areas of developing countries with no access to the electrical grid. The cooler coaxial configuration provides a feedback inertance and compliance to create the required travelling-wave phasing. Compressed air at 10 bar is used as the working fluid. The operating frequency is around 50 Hz. The geometric parameters of both engine and cooler, affecting the overall efficiency of cooling, have been investigated to evaluate the optimal configuration of the system. The most sensitive parameters are the cross sectional areas of the engine and cooler and the hydraulic radii of stack and regenerator

A method of characterising performance of audio loudspeakers for linear alternator applications in low-cost thermoacoustic electricity generators

This paper investigates the feasibility of using commercially available loudspeakers as low-cost linear alternators for thermoacoustic applications, to convert acoustic power to electricity. The design of a purpose built experimental apparatus, in which a high intensity acoustic wave is induced by using a high power woofer, is described. The rig is used to excite loudspeakers (referred here as “alternators”) under test, while a pair of microphones and a laser displacement sensor are used to enable acoustic power measurements. The paper presents a case study in which characteristics of acoustic-to-electric energy conversion of a candidate loudspeaker (alternator) – selected from the viewpoint of general performance, as well as parameters such as: high force factor, low electrical resistance and low mechanical loss – are measured. The measurements of acoustic power absorbed by the alternator and the electric power extracted from it by the load resistor, which allow estimating acoustic-to-electric efficiencies, are presented. The alternator has been tested at different operating frequencies, cone displacements and load resistance values. The measurement results are discussed and compared in detail with the calculations based on the linear acoustics model