Guobang Chen

Thermodynamic performance prediction of pulse tube refrigeration with mixture fluids

Abstract A refrigeration cycle with two isentropic and two isobaric processes, referred to as the modified Brayton cycle, is introduced for predicting the thermodynamic performance of pulse tube refrigeration with a binary mixture refrigerant. The corresponding theoretical expressions of cooling power, thermodynamic efficiency and required work of a refrigeration cycle are established. Based on the prediction calculations for a number of cryogenic fluids, promising mixture pairs of working refrigerants are recommended. The computed results show that 9.5% of the coefficient of performance (COP) and 6.7% of the cooling power at 80 K could be gained if a mixture pair of 10% nitrogen and 90% helium is used instead of pure helium for the pulse tube refrigeration. The minor mixture pairs which have a positive effect on pulse tube refrigeration at temperatures near 80 K, including hydrogen–helium, argon–helium and neon–helium, are also discussed.

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.

Discussion on refrigeration cycle for regenerative cryocoolers

Based on review and analysis of thermodynamic efficiency e of the Carnot cycle and the cycle with two isothermal and two polytropic processes, another thermodynamic cycle with two isentropic and two polytropic processes, which can achieve the Carnot value of thermodynamic efficiency, is testified theoretically. Thermodynamic efficiency expressions of a number of ideal regenerative refrigeration cycles are derived, including the ideal pulse tube refrigeration cycle. A classified branch chart and a plot of ideal thermodynamic efficiency of regenerative refrigeration cycles are given for the purpose of comparison.

Modification test of staged pulse tube refrigerator for temperatures below 4 K

Structure modification tests of a staged pulse tube refrigerator have been carried out for the purpose of increasing the performance and simplicity. The influence of operation parameters on cooling effect has been tested. To reach liquid helium temperatures by a two-stage pulse tube refrigerator, a double-orifice configuraton is utilized for enhancing the phase shift effect. Experimental results and a discussion are also presented.

Performance of multilayer insulation with slotted shield

Abstract Thermal and evacuating performance can be improved by means of slotting a number of one dimension slots on reflection shields of the multilayer insulation (MLI). The influence of slots on thermal radiation and gas conduction heat fluxes are theoretically studied. Based on the analysis and test, the optimum slot rate and length have been obtained. Experiments also show that the performance of MLI with slotted shield will be further improved if a combination of slotted shields with different slot rate can be used to fit the interstitial pressure distribution.

Experimental results of the internal process of a double inlet pulse tube refrigerator

Abstract This paper presents the test results of the internal process of a double inlet pulse tube refrigerator, the main objective is to reveal the effects of some important parameters, such as by-pass valve and orifice opening, operating frequency and mean pressure, on the amplitude shift and phase shift of three dynamic pressures at three different points (the hot end of the regenerator, pulse tube and reservoir)

Investigation on a two-stage solvay refrigerator with magnetic material regenerator

Abstract This paper describes experimental results that the no-load temperature of a two-stage Solvay refrigerator has been reached in liquid helium temperature region from the original 11.5 K by using magnetic regenerative material instead of lead. The structure and technological characteristics of the prototype machine are presented. The effects of operating frequency and pressure on the refrigerating temperature have been discussed in this paper.

13 K thermally coupled two-stage Stirling-type pulse tube refrigerator

Stirling-type pulse tube refrigerators have attracted academic and commercial interest in recent years due to their more compact configuration and higher efficiency than those of G-M type pulse tube refrigerators. In order to achieve a no-load cooling temperature below 20 K, a thermally coupled two-stage Stirling-type pulse tube refrigerator has been built. The thermally coupled arrangement was expected to minimize the interference between the two stages and to simplify the adjustment and optimization of the phase shifters. A no-load cooling temperature of 14.97 K has been realized with the two-stage cooler driven by one linear compressor of 200 W electric input. When the two stages are driven by two compressors respectively, with total electric input of 400 W, the prototype has attained a no-load cooling temperature of 12.96 K, which is the lowest temperature ever reported with two-stage Stirling-type pulse tube refrigerators.

Study of the minimum refrigeration temperature of regenerative cryocoolers

Abstract Based on the principles of thermodynamics, the relation between the isentropic expansion coefficient μs and the isobaric specific heat Cp has been found. The values of μs at different temperatures and pressures are calculated. From theoretical and experimental values of Cp of helium in the supercritical area, the minimum refrigeration temperature which may be reached by traditional regenerative cryocoolers is theoretically demonstrated. It is pointed out that this boundary is just the lambda line of helium. In order to obtain temperatures lower than the lambda line, a new type of regenerative cryocooler which can work in the helium II region is proposed. The working principle, schematic diagram and theoretical refrigeration temperature of this new cryocooler are discussed.

Comparison test of two-valved and valveless puise tube refrigerator

Abstract The performance of valved and valveless pulse tube refrigerator is studied and compared experimentally under the fixed configuration in a single-stage pulse tube refrigerator. The results indicate that two-valved pulse tube refrigerator may obtain better refrigeration performance with the correct on-off timing.