Study On Characteristics Of Oscillating Heat Exchanger In Thermoacoustic Engine

Thermoacoustic engine is a new kind of energy conversionequipment, which is based on the thermoacoustic effect. It is valued bymany researchers because of its many advantages, such as no movingparts, simplicity of structure, no-pollution, high reliability, using of thelow-grade energy and so on.Thermoacoustic engine is mainly made up of hot heat exchanger,cold heat exchanger, regenerator and the resonant tube. The role of hotand cold heat exchanger in the system is to make both ends of theregenerator form a temperature gradient in order to maintain thethermoacoustic effect. It is always been researched as emphases anddifficult points to the two components in thermoacoustic. At present,there are only a few methods of theoretical analysis and numericalsolution in the research of thermoacoustic oscillation heat transfer heatexchanger. However, most of the design of heat exchanger wascalculated according to the correlation equation of steady flow, which isnot applicable to oscillatory fluid heat exchanger. Basing on thepredecessors’ research, author of this article continue the study inthermoacoustic heat exchanger on the following aspects:According to wave theory, the hyperbolic model with double timedelay is established. The transverse temperature distribution inside themicro-channel of circular and parallel plate heat exchanger isinvestigated. And the heat is compared to different structures of the heatexchanger. The results show that the transverse temperature distributionis greatly affected by boundary conditions and thermal penetration depth.In practice, in order to improve the efficiency of the heat exchanger wegenerally make the value of the dimensionless r₀/δ_αbetween1and2forthe circular heat exchanger and dimensionless r₀/δ_αbetween1.5and2.5for parallel plate’s heat exchanger. The performance of parallel plateheat exchanger is superior to the circular heat exchanger, and for the thickness of heat exchanger, the thinner the better.Two kinds of thermoacoustic heat exchanger entropy productionexpression are derived according to the velocity and temperaturedistributions of the linear approximate conditions of low pressure ratioand small amplitude oscillations as well as the first law ofthermodynamics. The entransy dissipation number of the thermoacousticoscillation flow heat exchanger is derived by entransy dissipation theory.The relationship between the relevant characteristics of the oscillatingflow heat exchanger and entransy dissipation number is discussed withthe theoretical analysis and numerical simulation. It is showed that, ithas been a great impact on heat exchanger entropy production andentransy dissipation number with the geometric structure of heatexchanger, operating conditions and characteristic parameters. The heatexchanger should be designed that NTU＞1, and the countercurrententropy production rate is less than the downstream entropy productionrate, the thermal contact resistance inside the heat exchanger should bereduced as much as possible.Based on the test stand of our research group, it is studied that theheating temperature is making an impact on the resonant frequency,pressure wave amplitude and dimensionless oscillation temperature. Theexperimental results reveal that, the higher the heater temperature, thelarger the pressure amplitude, resonant frequency and the dimensionlessoscillation temperature. The improvement of these parameters is in favorof enhancing overall performance of thermoacoustic devices. Thenumerical calculation results of oscillation temperature are verified.