Guoyao Yu

300Hz thermoacoustically driven pulse tube cooler for temperature below 100K

This letter introduces a thermoacoustically driven pulse tube cooler system working at around 300Hz. In the system, a thermoacoustic standing-wave engine is used to drive a Stirling-type pulse tube cooler. Besides the design considerations for key components in each subsystem, the benefits of using the acoustic amplifier tube to couple the engine and the cooler have been analyzed through both calculations and experiments. So far, a lowest no-load temperature of 95K has been obtained on the system with the acoustic amplifier tube being used. Since high frequency operation of the system could lead to a much reduced system size, the result shows the potential of using the system in small-scale cryogenic applications.

Influence of acoustic pressure amplifier tube on a 300 Hz thermoacoustically driven pulse tube cooler

High frequency thermoacoustically driven pulse tube coolers (PTCs) have the advantages of high energy density, compact structure, and high reliability. Through a series of improvements, the 300 Hz thermoacoustically driven PTC in this paper achieved a fourfold increase in the cooling power compared with that in our last report. A cooling power of 1.04 W at 80 K and a no-load temperature of 63 K are obtained with 500 W heating power. In the system, the acoustic pressure amplifier tube (APAT) plays an important role in coupling the thermoacoustic engine and the PTC. The effects of APAT on the system performance are investigated here through both numeric simulations and experiments. The simulation indicates that length of the APAT is limited due to impedance match requirement between the PTC and the engine, which is partly evidenced by experiments. Calculation also gives a good agreement between calculated pressure wave amplification ratio and experimental values. APAT with different lengths and diameters ar...

Investigation on a free piston stirling cryocooler with large cooling capacity

Cryocoolers with large cooling powers at 80 K are very promising as they could find important applications in superconducting field such as cooling cables, transformers and fault current limiters. The pulse tube cryocooler has attracted attention due to its virtue of no moving components in the cold region. However, as the cooling power increases, problems inside the thermal buffer tube, such as difficulty in obtaining good flow straightening, existence of Rayleigh streaming, the gravity effect etc., present big obstacles to achieving high thermal efficiency. On the other hand, a free piston Stirling cryocooler, though more complicated due to the existence of the displacer, could avoid these problems with the elimination of the thermal buffer tube. Meanwhile, the efficiency is better than the pulse tube cryocooler around 80 K due to its capability of recovering the acoustic work. In this article, a free piston Stirling cryocooler with about 300 W cooling power at 80 K is designed with our simulation based on thermoacoustic theory. The theoretical analysis and numeric model are given in detail. The phase shift effect of the displacer and the internal energy loss mechanism are discussed. From our calculation, a relative Carnot efficiency of about 50% at 80 K has been obtained analytically.

Design of a large-capacity multi-piston pulse tube cryocooler

ercial high temperature superconductors, two designs for a pulse tube cryocooler have been developed. In the first design, three parallel-arrayed inertance pulse tube cryocoolers are driven by one twinopposed linear compressor. It is hard for this system to obtain a relative Carnot efficiency of higher than 25%. In the other design, it includes three pulse tube cryocoolers and three linear compressors. The inertance tube and reservoir of each pulse tube cryocooler are omitted. The compression chamber of each compressor is connected in series through a pulse tube cryocooler to the expansion chamber of another compressor. With this configuration, the acoustic work coming out of the secondary water-cooled heat exchanger can be recovered and it is much easier for the pulse tube cryocooler to obtain better acoustic field, so the relative Carnot efficiency of this system could be higher than 35%. It should be one of the best candidates for the cryocooler in high temperature superconductor power grid.

Thermoacoustically driven triboelectric nanogenerator: Combining thermoacoustics and nanoscience

A thermoacoustic heat engine (TAHE) is a type of regenerative heat engine that converts external heat into mechanical power in the form of an acoustic wave with no moving mechanical components. One significant application of the TAHE is the generation of electricity by coupling an acoustic-to-electric conversion unit such as a linear motor or a piezoelectric ceramic assembly. However, present-day conversion technologies have considerable drawbacks, including structural complexity, high cost, and low reliability. The advent of triboelectric nanogenerators (TENGs) offers an alternative means to overcoming these shortcomings. In this paper, we propose a thermoacoustically driven TENG (TA-TENG) that continuously harvests external heat. A test rig involving a standing-wave TAHE and a contact-separation mode TENG was fabricated to demonstrate this concept. Currently, the TA-TENG produces a maximum output voltage of 10 V and a corresponding output power of 0.008 μW with a load of 400 MΩ, demonstrating the viabil...

Performance of a 260 Hz pulse tube cooler with metal fiber as the regenerator material

Pulse tube coolers operating at higher frequency lead to a high energy density and result in a more compact system. This paper describes the performance of a 300 Hz pulse tube cooler driven by a linear compressor. Such high frequency operation leads to decreased thermal penetration, which requires a smaller hydraulic diameter and smaller wire diameter in the regenerator. In our previous experiments, the stainless steel mesh with a mesh number of 635 was used as the regenerator material, and a no-load temperature of 63 K was obtained. Both the numerical and experimental results indicate this material causes a large loss in the regenerator. A stainless steel fiber regenerator is introduced and studied in this article. Because this fiber has a wide range of wire diameter and porosity, such material might be more suitable for higher frequency pulse tube coolers. With the fiber as the regenerator material and after a series of optimizations, a no-load temperature of 45 K is acquired in the experiment. Influenc...

Suppression of harmonics in a high frequency standing‐wave thermoacoustic engine

A thermoacoustic engine converts heat into acoustic power and could be used to driven a cooler for refrigeration purposes or to drive a piston for electric power generation. Due to non‐linear effects inside the system, higher order harmonics could be generated which may deteriorate the thermal performance of the whole system. In this report, a 500Hz standing wave thermoacoustic engine has been built. The occurrence of higher order acoustic oscillations has been closely observed. A series of experiments has been done to investigate the influence of resonance tube configuration on this phenomenon. The influence on the related thermal performance is also reported.