R. Bao

Thermoacoustically driven pulse tube refrigeration below 80K by introducing an acoustic pressure amplifier

A copper tube of 3.3m in length and 8mm in inner diameter, acting as an acoustic pressure amplifier, was incorporated in a standing-wave thermoacoustically driven pulse tube refrigerator system. The enhancement of pressure ratio from 1.129 to 1.152 by the acoustic pressure amplifier has been obtained. As a result, a cooling temperature as low as 79.7K and a tripled coefficient of performance improvement at 120K were reached.

He-H2 mixture and Er3NiHx packing for the refrigeration enhancement of pulse tube refrigerator

The computation with the theory of modified Brayton Cycle indicates that higher cooling power and coefficient of performance for a pulse tube refrigerator can be achieved with He-H2 mixture as working gas than those with pure He in the temperature region of 30 K. In addition, it is found that Er3Ni, a regenerative material, is able to absorb H2 and produces Er3NiHx. The computation presents that the regenerative performance of Er3NiHx is better than that of Er3Ni due to its higher volume specific heat. Experimental results show that the pulse tube refrigeration performance in 30 K temperature region is enhanced greatly with He-H2 mixture and Er3NiHx packing.

Theoretical prediction on the coupling of thermoacoustic prime mover and RC load

Publisher Summary This chapter investigates a thermoacoustic prime mover to use it to drive a load, such as a pulse tube refrigerator or a thermoacoustic refrigerator etc. When the load is connected to the prime mover, the coupling between them is of great importance for the performance of the thermoacoustic system. To investigate the coupling relation, a standing wave thermoacoustic prime mover connected with an RC (resistance and capacitance) load is simulated with linear thermoacoustics. The coupling of thermoacoustic prime mover and its load is of great importance for the performance of thermoacoustic system. A standing wave thermoacoustic prime mover with RC load is simulated, and the influence of RC load and dimensions of the resonance tube on the behavior of the thermoacoustic system is discussed according to the computed results. The computed results indicate that the behavior of the thermoacoustic system is greatly influenced by the impedance of the load and the dimensions of the resonance tube. C of RC load is a key influencing factor when 1/ωC is larger than R, while R is of great importance, when 1/ωC is less than R. The maximum acoustic power output can be achieved when 1/ωC equals to R, while pressure amplitude is the minimum and hot end temperature of the stack is the highest.

Thermoacoustically driven pulse tube refrigeration below 90K

Publisher Summary This chapter focuses on the matching between thermoacoustic prime mover and pulse tube refrigerator, especially the frequency matching. Recent modification has been made to improve the refrigeration performance of thermoacoustically driven pulse tube refrigerator, and a refrigeration temperature as low as 88.6K, with helium filling of 2.1MPa as the working fluids, is achieved. The onset temperature is reduced about 200oC (from 550oC to 340oC) by the simple operation of the double inlet valve which would broaden the utilization of low-grade heat energy. With helium as working fluid (filling pressure of 2.1MPa), an 8 m resonant tube results in a resonance frequency of 44 Hz (the input power is 2200 Watts), and a refrigeration temperature of 88.6K is obtained in self-made thermoacoustically driven pulse tube refrigerator system while the mean pressure and the pressure ratio are 2.64MPa and 1.128, respectively. The simple operation on the double inlet valve, which was closed before the onset of acoustic oscillation and turned to the optimal value as soon as the oscillation started, could decrease the onset temperature of the system greatly. It would broaden the access of utilizing the low-grade heat energy.

Chapter 65 – Influence of He-H2 Mixture Proportion on the Performance of Pulse Tube Refrigerator*

Publisher Summary This chapter explores the influence of mixture working fluids on the pulse tube refrigeration performance. The performance of pulse tube refrigerator (PTR) can be improved by using mixtures as its working fluid. Based on an experimental work on a two-stage PTR with He-He 2 mixture whose hydrogen percentage rising from 0% to 100%, an optimal proportion of H 2 in the He-He 2 mixture for the cooling temperature around 30K is found. The pulse tube refrigeration performance with He-H 2 mixtures is better than that with pure helium in 30K cooling temperature region when the hydrogen fraction is less than about 80%. A 30–45% increment of both the cooling power and COP has been obtained with 60–70% H 2 in He-H 2 mixtures. The great performance improvement of the PTR may be attributed to not only the excellent cycle thermodynamic performance and the reasonable heat transfer and flow properties of He-H 2 mixtures, but also the high volume specific heat of Er 3 NiH x regenerative materials.

Influence of He-H 2 Mixture Proportion on the Performance of Pulse Tube Refrigerator

Publisher Summary This chapter explores the influence of mixture working fluids on the pulse tube refrigeration performance. The performance of pulse tube refrigerator (PTR) can be improved by using mixtures as its working fluid. Based on an experimental work on a two-stage PTR with He-He 2 mixture whose hydrogen percentage rising from 0% to 100%, an optimal proportion of H 2 in the He-He 2 mixture for the cooling temperature around 30K is found. The pulse tube refrigeration performance with He-H 2 mixtures is better than that with pure helium in 30K cooling temperature region when the hydrogen fraction is less than about 80%. A 30–45% increment of both the cooling power and COP has been obtained with 60–70% H 2 in He-H 2 mixtures. The great performance improvement of the PTR may be attributed to not only the excellent cycle thermodynamic performance and the reasonable heat transfer and flow properties of He-H 2 mixtures, but also the high volume specific heat of Er 3 NiH x regenerative materials.