H.E. Bass

Bio: H.E. Bass is an academic researcher from ASTRON. The author has contributed to research in topics: Thermoacoustics & Acoustic wave. The author has an hindex of 1, co-authored 1 publications receiving 774 citations.

Thermoacoustic engines

Abstract: Thermoacoustic engines (TAEs) can be used to pump heat using a sound wave or pump a sound wave using a temperature gradient. The basic arrangement is a gas-filled acoustic resonator with appropriately positioned thermoacoustic elements. Two types of thermoacoustic elements are used in these engines: (1) heat exchangers used to communicate heat between the gas and external heat reservoirs; and (2) the TAE, also known as a stack. The TAEs are sections of porous media that support the temperature gradient, transport heat on the acoustic wave between the exchangers, and produce or absorb acoustic power. Previous results have been developed for TAEs with circular or parallel slit pore geometries. The theory is extended for gas-filled TAEs to include pores of arbitrary cross-sectional geometry. An approximate analysis of energy flow and acoustical measurements of a thermoacoustic prime mover are given. >

A thermoacoustic Stirling heat engine

Abstract: Electrical and mechanical power, together with other forms of useful work, are generated worldwide at a rate of about 1012 watts, mostly using heat engines. The efficiency of such engines is limited by the laws of thermodynamics and by practical considerations such as the cost of building and operating them. Engines with high efficiency help to conserve fossil fuels and other natural resources, reducing global-warming emissions and pollutants. In practice, the highest efficiencies are obtained only in the most expensive, sophisticated engines, such as the turbines in central utility electrical plants. Here we demonstrate an inexpensive thermoacoustic engine that employs the inherently efficient Stirling cycle1. The design is based on a simple acoustic apparatus with no moving parts. Our first small laboratory prototype, constructed using inexpensive hardware (steel pipes), achieves an efficiency of 0.30, which exceeds the values of 0.10–0.25 attained in other heat engines5,6 with no moving parts. Moreover, the efficiency of our prototype is comparable to that of the common internal combustion engine2 (0.25–0.40) and piston-driven Stirling engines3,4 (0.20–0.38).

A thermoacoustic-Stirling heat engine: detailed study

Abstract: A new type of thermoacoustic engine based on traveling waves and ideally reversible heat transfer is described. Measurements and analysis of its performance are presented. This new engine outperforms previous thermoacoustic engines, which are based on standing waves and intrinsically irreversible heat transfer, by more than 50%. At its most efficient operating point, it delivers 710 W of acoustic power to its resonator with a thermal efficiency of 0.30, corresponding to 41% of the Carnot efficiency. At its most powerful operating point, it delivers 890 W to its resonator with a thermal efficiency of 0.22. The efficiency of this engine can be degraded by two types of acoustic streaming. These are suppressed by appropriate tapering of crucial surfaces in the engine and by using additional nonlinearity to induce an opposing time-averaged pressure difference. Data are presented which show the nearly complete elimination of the streaming convective heat loads. Analysis of these and other irreversibilities show which components of the engine require further research to achieve higher efficiency. Additionally, these data show that the dynamics and acoustic power flows are well understood, but the details of the streaming suppression and associated heat convection are only qualitatively understood.

Development of the pulse tube refrigerator as an efficient and reliable cryocooler

Abstract: This paper presents a review of the pulse tube refrigerator from its inception in the mid-1960s up to the present. Various factors are discussed which brought it from a laboratory curiosity to the point where it is now the most efficient of all cryocoolers and reliable enough to be used on space missions. Carnot efficiencies as high as about 20% at 80 K and temperatures as low as 2 K have been achieved in pulse tube refrigerators. The operating principles for the different types of pulse tube and thermoacoustic refrigerators are described. Pulse tube refrigerators operate with oscillating pressures and mass flows and have no moving parts in the cold end. For large industrial systems the mechanical compressor can be replaced with one of two types of thermoacoustic drivers to yield a refrigerator with no moving parts. Recent advances in understanding and reducing losses in various components are described that have led to the improved efficiencies. The major problems associated with cryocoolers are listed, and it is shown that pulse tube refrigerators have begun to overcome many of these problems. As a result, they are now being used or considered for many different applications. Some of these applications as well as example pulse tube refrigerators are described.

General formulation of thermoacoustics for stacks having arbitrarily shaped pore cross sections

Abstract: Theoretical treatments of thermoacoustics have been reported for stacks with circular pore and parallel plate geometries. A general linear formulation is developed for gas‐filled thermoacoustic elements such as heat exchangers, stacks, and tubes having pores of arbitrary cross‐sectional geometry. For compactness in the following, F represents the functional form of the transverse variation of the longitudinal particle velocity. Generally, F is a function of frequency, pore geometry, the response functions and transport coefficients of the gas used, and the ambient value of the gas density. Expressions are developed for the acoustic temperature, density, particle velocity, pressure, heat flow, and work flow from knowledge of F. Heat and work flows are compared in the short stack approximation for stacks consisting of parallel plates, circular, square, and equilateral triangular pores. In this approximation, heat and work flows are found to be greatest for the parallel plate stack geometry. Pressure and spe...