Jinghui Cai

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.

Pulse tube refrigerator with low temperature switching valve: concept and experiments

The concept of a new type of pulse tube refrigerator, termed pulse tube refrigerator with low temperature switching valve, is proposed. It is suitable for industrial applications that require larger 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. Methods for increasing the adiabatic efficiency are discussed.

DYNAMIC CHARACTERISTICS OF OSCILLATING FLOW IN PULSE TUBE COOLERS

A dynamic measuring system is set up to measure the mass flow rates and pressure waves inside pulse tube coolers. An in-line orifice type pulse tube cooler is tested. Phase shift angles for different input powers are measured and compared. Difference of gas flow characteristics under small perturbation and larger pressure wave condition is discussed.

Experimental Flow Characteristics Study of a High Frequency Pulse Tube Regenerator

In this paper, a one-dimensional regenerator hydrodynamic model has been developed. In the model, the definition of regenerator friction factor under oscillating flow is different from that for steady flow. A dynamic experimental apparatus has been designed and constructed to investigate the oscillating-flow characteristics of regenerators. In the prototype experimental system, a linear compressor was used to generate the oscillating pressure wave. Three different length regenerators were tested. Detailed experimental data have been obtained for the oscillating pressure and velocity wave that define the flow amplitude and the phase shift characteristics of a high frequency pulse tube cryocooler regenerator. The operational frequency of the system was run at 30 Hz, 40 Hz, 50 Hz and 60 Hz. The oscillating flow friction factor at these operational frequencies is shown in the experimental data. It was found that the relationship between the friction factor under oscillating flow and steady flow varied with the value of the instantaneous Reynolds numbers during one cycle. The ratio is not simply a scaler-multiple relationship as has been reported in other References. The results can be used to predict the performance of a pulse tube cryocooler and should be helpful in the design of a cryogenic regenerator using numerical simulation models.

Development of 40–80K Linear-Compressor Driven Pulse Tube Cryocoolers

Along with the commercialization of HTS devices in fields such as mobile communications, and the development of far infrared devices for space and military applications, there arises a strong demand for compact and reliable cryocoolers working at 40–60K. The pulse tube cryocooler driven by a linear pressure wave generator has the potential to achieve high reliability and very long lifetime because of the absence of moving parts at low temperature. The ability of this kind of pulse tube cryocooler to achieve efficiencies comparable with Stirling cryocoolers has been theoretically and practically proven1-3. Hence, pulse tube cryocoolers appear a good choice to meet the abovementioned requirements.

On the development of co-axial miniature pulse tube coolers for space applications

Cryocoolers for cooling infrared sensors in space applications require high reliability, long lifetime, low power and minimum weight. In this paper we report work on a miniature pulse tube cooler specifically designed for such applications. A series of engineering model co-axial miniature pulse tube coolers with a flexure bearing linear compressor of 1 cc swept volume have been designed and fabricated in our laboratory. A theoretical model is established based on the analyses of thermodynamic and hydrodynamic behaviors of oscillatory flows in regenerator, for performance prediction, optimization and as a rough guide in the early stages of system design. An experimental apparatus, including a hot wire anemometer, has been set up to study the flow resistance of regenerators under oscillatory flow conditions. The co-axial, multi-bypass, and symmetric nozzle structure has been used in the coolers. We will present here the performance of two sizes of coolers with 9 mm and 8 mm diameter of cold fingers. The 9 m...

Miniature pulse tube cooler at 100HZ

Miniature pulse tube coolers operating at 100Hz have been designed and manufactured. The regenerator is designed by REGEN 3.2, and the inertance tube is simulated by DeltaE. An in-line prototype is manufactured according to the theoretical design parameters initially. On that basis, a coaxial cooler is developed and with double inlet it gains higher cooling performance.

Experimental investigation of a u-shape pulse tube cryocooler with one regenerator and two pulse tubes

In this paper, two normal U-shape pulse tube cryocoolers named U-PTC1 and U-PTC2, with different connecting tube locations, have been described. Based on the U-PTC1 and U-PTC2, two U-shape pulse tube cryocooler prototypes with two pulse tubes named U-DPTC1 and U-DPTC2 have been designed and manufactured. The prototype U-DPTC1 was able to gain 120K@6W cooling power with 80W electric power. This experiment demonstrated the feasibility of individual phase-shifting and DC flow could occur under general phase-shifting, reducing the performance of the cryocooler.

INVESTIGATION ON THE OSCILLATING GAS FLOW ALONG AN INERTANCE TUBE BY EXPERIMENTAL AND CFD METHODS

To investigate the oscillating gas flow along an inertance tube used in pulse tube coolers, a CFD model is set up for FLUENT and an experimental measuring cell is designed and optimized by CFD results. Some characteristics of oscillating flow are demonstrated and discussed. Then, the flow status along an inertance tube is measured by the optimized measuring cell. The experimental results validate the simulating results.

AN INTEGRATED MINIATURE PULSE TUBE CRYOCOOLER AT 80K

Two integrated models of coaxial miniature pulse tube coolers based on an experimental model are manufactured. Performance of the integrated models is compared to that of the experimental model. Reliability and stability of an integrated model are tested and improved.