•A new type pulse tube cryocooler driven by the thermal-compressor was experimentally studied.•A minimum no-load temperature 4.9 K was obtained, and the cooling power was 30 mW@5.6 K.•The multi-bypass was firstly used in the low-frequency Stirling type pulse tube cryocooler.•The calculated total input power was no more than 450 W.VM type pulse tube cryocooler is a new type pulse tube cryocooler driven by the thermal-compressor. This paper presented the recent experimental results on a novel single-stage VM type pulse tube cryocooler with multi-bypass. The low temperature double-inlet, orifice and gas reservoir, and multi-bypass were used as phase shifters. With the optimal operating frequency of 1.6 Hz and optimal average pressure of 1.4 MPa, a no-load temperature of 4.9 K has been obtained and 30 mW@5.6 K cooling power has been achieved. It was the first time for the single-stage VM-PTC obtaining liquid helium temperature reported so far. Moreover, it was also the first time for the multi-bypass being used in the low-frequency Stirling type pulse tube cryocooler.

•A numerical method based on finite volume method was carried and verified.•It showed the waves in TCP no longer obeyed the linear thermoacoustics theory.•The influence of operating parameters on the performance of TCP was studied.•The RC load method was used to study the thermoacoustics characteristics of TCP.•The output performances of TCP were optimized by using this numerical model.Thermal compressor, different from the linear compressor, is one kind of compressor utilizing heat power directly to generate a pressure wave. Combining with the pulse tube cryocooler, it could become a new type high efficiency 4 K cryocooler. In present work, a numerical method based on finite volume method was carried out to study the characteristics of thermal compressor. The simulation results were verified by experiments at first. Then the no-load performance of thermal compressor was studied and the results showed that the waves in the thermal compressor no longer obeyed the linear thermoacoustics theory. And then, the RC load method was used to study the output thermoacoustics characteristics of thermal compressor. With a RC load, the wave mode in the thermal compressor would convert into the traveling wave from standing wave. The results showed that thermal compressor was preferable to drive the capacitive load and the best impedance of orifice valve was about 5 × 109 Pa s/m3. According to the optimum load impedance optimized above, we can design a suitable PTC for the TCP.

The pulse tube refrigerator (PTR) is a promising small-scale cryocooler. This paper first briefly introduces the history of the pulse tube refrigerator. It has pointed out that technology improvements and theoretical developments of the pulse tube refrigerator closely relate with the internal streaming effects. Then the discovering history and classification of the streaming or DC (direct current) flow effect are summarized. It proposes for the first time that the physical significance of the streaming contains the driving mechanisms and the transport mechanisms. It demonstrates that the driving mechanisms are the asymmetry of fluid flow and temperature while the transport mechanisms are a loop or vorticity, which transmits nonlinear dissipations. The important advancements have been made over the past two decades all over the world in research of streaming of the pulse tube refrigerator including Gedeon DC flow, Rayleigh streaming, the third type of DC flow and the regenerator circulation. With regard to Gedeon DC flow, theoretical and experimental analyses have been made and different suppression methods are summarized. In the aspect of Rayleigh streaming, it mainly focuses on the analytical solution of the second-order mass flow and the research of tapered pulse tubes. In particular, limited research on the third type of DC flow and regenerator circulation is presented. The experimental measurement techniques of streaming also are summarized. Finally, this paper briefly discusses the key scientific and technical issues of the current research, and foretells the future development trends of streaming research in PTR.

DC gas flow in pulse tube cryocooler (PTC) is a crucial problem both in theory and application which considerably affects the refrigeration performance. We have experimentally discovered and verified the third type of DC gas flow in PTC which is formed due to hydrodynamic and thermodynamic asymmetry of the regenerator and other flow channels. This new type of DC gas flow is possible to be identified in other regenerative engines or refrigerators. We also introduced a highlighting method which can suppress this kind of DC gas flow effectively in most cases, with the best result of 30 K temperature drop at the cold end of the PTC.

We present a two-stage pulse tube cryocooler working at 300 Hz driven by a thermoacoustic engine. Compared to the previous experimental results, the combined inertance tube with different diameters that is used in the second stage is found to play the key role in phase shifting and to lead to superior cooling. Two different wall thickness tubes are tested in the experiments. After the optimization, the second-stage cold end achieves a no-load temperature of 57.9 K with an average pressure of 3.8 MPa, and a cooling capacity of 0.5 W at 81.88 K.

•We present a novel hybrid wind-solar-compressed air energy storage system.•Wind and solar power are transformed into stable electric energy and hot water.•The system output electric power is 8053 kWh with an exergy efficiency of 65.4%.•Parametric sensitivity analysis is presented to optimize system performance.Wind and solar power have embraced a strong development in recent years due to the energy crisis in China. However, owing to their nature of fluctuation and intermittency, some power grid management problems can be caused. Therefore a novel hybrid wind-solar-compressed air energy storage (WS-CAES) system was proposed to solve the problems. The WS-CAES system can store unstable wind and solar power for a stable output of electric energy and hot water. Also, combined with organic Rankin cycle (ORC), the cascade utilization of energy with different qualities was achieved in the WS-CAES system. Aiming to obtain the optimum performance, the analysis of energy, exergy and parametric sensitivity were all conducted for this system. Furthermore, exergy destruction ratio of each component in the WS-CAES system was presented. The results show that the electric energy storage efficiency, round trip efficiency and exergy efficiency can reach 87.7%, 61.2% and 65.4%, respectively. Meanwhile, the parameters analysis demonstrates that the increase of ambient temperature has a negative effect on the system performance, while the increase of turbine inlet temperature has a positive effect. However, when the air turbine inlet pressure varies, there is a tradeoff between the system performance and the energy storage density.