Jingtao Liang

Development of a single-stage pulse tube refrigerator capable of reaching 49 K

Abstract The orifice pulse tube refrigerator is a new type of cryocooler which was reported to be capable of reaching 60 K. The present authors have achieved a temperature of 49 K for the first time with a single-stage orifice pulse tube refrigerator by improving the regenerator, the hot end heat exchanger and the insulation of the low temperature sections. A refrigeration power of 12 W could be obtained at 77 K at the cold end. The relation between the ratio of regenerator volume to pulse tube volume and the minimum temperature of the orifice pulse tube refrigerator was experimentally investigated. Methods for further improving the performance of the orifice pulse tube refrigerator are discussed.

Study on miniature pulse tube cryocooler for space application

Abstract Pulse tube refrigerator (PTR) is a new type of mechanical cryocooler with the potential of long-term operation in space. Theoretical and experimental studies are currently on the way in the Cryogenic Laboratory of Chinese Academy of Sciences (CL/CAS) in order to develop a 85 K/250 mW class pulse tube cryocooler to be used to cool space-borne infrared devices. A theoretical model is established based on the analyses of the thermodynamic behavior of gas parcels in oscillating flow regenerators. It helps us to understand the cooler and can be used to study the influence of DC flow on the refrigeration performance. The flow resistance of the regenerator is an important factor for the cooler performance. A test bench, including a hot-wire anemometer has been set up to investigate the flow resistance characteristics of regenerators with oscillating flow. The results of measurement are correlated and served for practical design. The Oxford type linear pressure wave generator with flexure bearings is also under development in CL/CAS. The prototype miniature pulse tube cryocooler, driven by a linear pressure wave generator of 1.06 cm 3 maximum swept volume, provides at present 200 mW net cooling power at 81 K with 28.4 W input power. Improvements are being made to further increase the cooling power and reduce the input power.

A demonstration HTS base station sub-system for mobile communications

A demonstration sub-system for mobile communications was developed. In this system, a high-temperature superconducting (HTS) microstrip bandpass filter on r-plane sapphire substrate was designed to have a quasi-elliptic function response, which was aimed at covering the whole receive band of DCS 1800 base station, i.e. 1710–1785 MHz. This filter was then integrated with a low noise amplifier (LNA) and a pulse tube cryocooler, forming a demonstration sub-system. Satisfactory performance of this system was achieved.

Experimental study on a high frequency miniature pulse tube refrigerator with inertance tube

It is generally considered that the use of an inertance tube in a high frequency pulse tube refrigerator (PTR) improves the phase shift between the pressure and the mass flow rate. In order to investigate the effects of inertance tubes on the performance of a miniature PTR, experiments on the high frequency miniature PTR with inertance tube, orifice and bypass have been carried out. Inertance tubes with various inner diameters of 0.5 mm, 1 mm, 1.5 mm, 2 mm and different lengths from 1 m to 7 m were tested. Two fine needle valves were adapted as the orifice and the bypass. The experiments were performed under a charge pressure of 2.5 MPa. The operating frequency is varied from 20 Hz to 50 Hz. Experimental results show that the inertance tube with inner diameter of 1.5 mm and length of 2 m is proper for the miniature PTR at high frequency. The benefit of using only an inertance tube is not apparent in miniature PTR. The lowest temperature achieved by the PTR with inertance tube is only 107.3 K, which is hig...

Oscillating Flow Characteristics of a Regenerator under Low Temperature Conditions

An experimental system was designed and constructed to investigate the oscillating flow characteristics of a regenerator under low temperatures. Experimental data on the pressure drops of a regenerator subject to oscillating flow under low-temperature conditions have been obtained. It is found that the value of the cycle-averaged pressure drop of the oscillating flow in the regenerator under liquid nitrogen temperatures is 5~6 times higher than that of a steady flow at the same Reynolds number based on the cross-sectional mean velocity. A correlation equation for the friction factor at liquid nitrogen temperatures has been obtained, and a comparison is made with that obtained at ambient temperatures. Because the test conditions are very close to the operating conditions of practical high frequency cryocoolers, the experimental data should be useful for the prediction of performance and design of cryogenic regenerators.

Experimental Investigation of a G-M Type Coaxial Pulse Tube Cryocooler

A G-M type coaxial pulse tube cryocooler is first optimized from three aspects: the dimensional layout of the pulse tube and regenerator, the filling materials in the regenerator, and the structure of the cold end heat exchanger. Three different types of phase shifters: needle valves, capillaries and asymmetry-nozzles are then employed at the hot end of the pulse tube for the adjustment of the phase between the gas mass flow and the pressure oscillations. The influences of DC flow are investigated experimentally. It is found that a proper positive DC flow has positive effects on the cooling performance of the coaxial pulse tube cryocooler.

Thermodynamic Analysis of a Mixed-Refrigerant Auto-Cascade J-T Cryocooler with Distributed Heat Loads

In this paper, an effort is made to go further into the thermodynamic process of the Auto-Cascade refrigeration cycle using multicomponent zeotropic mixtures as working fluids. The exergy method is employed to analyze the thermodynamic characteristics of components and the whole refrigeration cycle. Specially, the condition that there are extra-distributed heat loads along the heat exchangers is considered. Extensive comparison is made between the single stage J-T cycle and a typical Auto-Cascade cycle at the same condition. At the calculation conditions presented in this paper, the total exergy gained in the MARC is 6.6% better than the single stage cycle, and 9.5% better in the situation with distributing heat loads. The results show that using appropriate Auto-Cascade cycle can improve the performance of the refrigerator.

Pulse Tube Refrigerator with low Temperature Switching Valve

Publisher Summary This chapter proposes a new method for achieving large refrigeration powers for some industrial applications. It proposes a new type of pulse tube refrigerator, termed pulse tube refrigerator with low temperature switching valve. Pulse tube refrigerator has been developing at an amazing speed Its refrigeration performance is now becoming comparable to that of G-M refrigerator or Stirling refrigerator. Therefore pulse tube refrigerator is finding more and more applications. It is suitable for industrial applications that require large refrigeration powers. In this kind of pulse tube refrigerator a recuperative heat exchanger instead of a regenerator is used and a switching valve is installed at the cold end of an orifice pulse tube. The adiabatic expansion efficiency of the orifice pulse tube with low temperature switching valve, which actually works as a new type of expander, has been experimentally investigated. Adiabatic efficiencies higher than 40% have been achieved in the preliminary experiments.

Experimental Investigation of an Efficient Closed-Cycle Mixed-Refrigerant J-T Cooler

The thermodynamic performance of a closed-cycle Joule-Thomson cryocooler with gas mixtures is experimentally investigated. Good refrigeration performances have been achieved with rather low pressure ratios. The high pressure of the two-stage oil-free compressor ranges from 2.5MPa to 4.5MPa, but the low pressure of the compressor is fixed as 0.1MPa. And the temperature of the inlet of high pressure flow for heat exchanger is fixed as 300K. In the experiment, two kinds of gas mixtures are used. The first one is N e + CH 4 + C 2 H 6 + C 3 H 8 + i − C 4 H 10 and the second one is N e + C 2 H 4 + C 2 H 6 + C 3 H 8. Under the above-mentioned operating conditions, the mixed-refrigerant J-T cooler achieved the lowest temperatures of around 69K–70K and 25W–35W of cooling capacity at liquid nitrogen temperature. The excergy efficiency of the whole cooling system is about 5–9%. The experimental results show that using gas mixtures as working substance is indeed a very potential way to improve the efficiency of Joule-Thomson cryocooler.

The Role of the Orifice and the Secondary Bypass in a Miniature Pulse Tube Cryocooler

This paper focuses on the phase shifting role of the orifice and the secondary bypass in a miniature pulse tube cryocooler. Firstly, the equation of the mass flow rate through the valve is extended into the Fourier series to investigate the phase difference between dynamic pressure in the pulse tube and mass flow rate at the hot end of the pulse tube. The analytical results show that the orifice opening has weak effect on the phase difference between the pressure and the mass flow rate at hot end when the secondary bypass is closed. And the mass flow rate at the hot end of the pulse tube is almost in phase with the dynamic pressure in the pulse tube. The introduction of the secondary bypass will make the pressure in the pulse tube always lead the mass flow rate at the hot end. For the orifice pulse tube cryocooler, the experiments show that with the orifice opening increasing, the phase difference is increasing but less than 3 degree for the opening of the orifice within the range from 0.2 to 2 turns. Based on the optimum orifice opening, the phase difference between the pressure in the pulse tube and the mass flow rate at the hot end increases as the opening of the secondary bypass increases. The experimental result agrees with the analytical result qualitatively.