Peter H. Ceperley

Bio: Peter H. Ceperley is an academic researcher. The author has contributed to research in topics: Acoustic wave & Stirling engine. The author has an hindex of 3, co-authored 5 publications receiving 544 citations.

A pistonless Stirling engine—The traveling wave heat engine

Abstract: The propagation of acoustical waves through a differentially heated regenerator results in gas in the regenerator undergoing a Stirling thermodynamic cycle. One direction of wave propagation results in amplification of the waves and conversion of thermal energy into acoustical energy. The opposite direction results in acoustical energy being used to pump heat. The ideal gain and maximum energy conversion rates are derived in this paper. Low power gain measurements were made which verify the derived gain equation. Practical engines and heat pumps using this principle are discussed.

Gain and efficiency of a short traveling wave heat engine

Abstract: Gain and efficiency equations are derived and evaluated for a traveling wave heat engine having a regenerator of short length compared with an acoustic wavelength. A traveling wave heat engine is a modified Stirling engine in which acoustic waves replace the usual pistons and energy is transferred between thermal and acoustic forms, depending on the wave direction [P. H. Ceperley, J. Acoust. Soc. Am. 66, 1508–1513 (1979)]. This paper is similar to another paper on gain and efficiency [P. H. Ceperley, J. Acoust. Soc. Am. 72, 1688–1694 (1982)] except that the present paper assumes that the wave impedance is not determined by the regenerator's properties, but instead by the acoustic circuit exterior to the regenerator. For acoustic impedance of freely propagating traveling waves in air, the efficiency is limited to 11% of Carnot efficiency due to visious heating in the regenerator. This can be greatly increased by going to higher impedances; e.g., 79% is possible at ten times greater impedance.

Gain and efficiency of a traveling wave heat engine

Abstract: Gain and efficiency equations are derived for a traveling wave heat engine, a device in which acoustic traveling waves force gas within a differentially heated regenerator to undergo a Stirling thermodynamic cycle and transform energy between thermal and acoustic forms. This derivation assumes nonturbulent flow conditions, a linear drag coefficient, a constant heat exchange coefficient, and neglects regenerator end effects. The complex characteristic impedance, gain, and efficiency are calculated for a thin slice of the regenerator in terms of dimensionless variables. With a Prandlt number of 0.7, the equations predict an efficiency of 70% that of an ideal Carnot cycle, and gain of 85% of that of theoretical maximum gain when fN ≡ωτ=0.003 and T′N≡ (dT/dx)T−1CIτ=0.4, where ω is the acoustic angular frequency, τ is the thermal time constant for the heat exchange process, dT/dx is the regenerator temperature gradient, and CI is the isothermal velocity of sound. In general, the equations predict that efficien...

Observation of single‐point excitation and shocking of rotating acoustic waves.

Abstract: In a cylindrically symmetric resonator or a ring resonator, the proper combination of standing wave modes results in a rotating wave field. Such a field has the appearance of a traveling wave chasing its tail, a constant field profile rotating in space. However, unlike traveling waves, rotating waves are limited to distinct modes. Rotating waves offer the clearest insight into angular momentum and rotary motion in wave fields. The following observations will be reported: (1) rotating acoustic waves in a concentric ring resonator and in a cylindrical resonator; (2) single‐point excitation of these waves [P. H. Ceperley, ‘‘Split mode traveling wave ring resonator,’’ U.S. Patent 4,686,407 (1987)]; and (3) weak shocking of the wave fronts at acoustic amplitudes near 1 kPa. These all relate to one atmosphere, air‐filled resonators. [Work supported by ONR.]

Acoustic spiral wave field

Abstract: While most low‐amplitude acoustic waves in uniform media can be considered to travel straight from source to receiver, the energy flow and propagation directions in a spiral wave field change as the wave moves away from its source [P. H. Ceperley, Am. J. Phys. 60, 938–942 (1992)]. Thus, one would expect that directional microphones and acoustic imaging systems would give false information as to the location of the source in such a wave field. Two synchronized oscillators, four small speakers, and a horn were used to create a spiral wave in the laboratory. A table top robot arm and microphone were used to map out this sound field, which was then displayed in color using MathCad. The apparent propagation direction was measured using a directional microphone. [Work supported by ONR.]

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.

Thermoacoustic Engines and Refrigerators

Abstract: We ordinarily think of a sound wave in a gas as consisting of coupled pressure and displacement oscillations. However, temperature oscillations always accompany the pressure changes. The combination of all these oscillations, and their interaction with solid boundaries, produces a rich variety of “thermoacoustic” effects. Although these effects as they occur in everyday life are too small to be noticed, one can harness extremely loud sound waves in acoustically sealed chambers to produce powerful heat engines, heat pumps and refrigerators. Whereas typical engines and refrigerators have crankshaft‐coupled pistons or rotating turbines, thermoacoustic engines and refrigerators have at most a single flexing moving part (as in a loudspeaker) with no sliding seals. Thermoacoustic devices may be of practical use where simplicity, reliability or low cost is more important than the highest efficiency (although one cannot say much more about their cost‐competitiveness at this early stage).