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High power Stirling-type pulse tube cryocoolers are considered as one of the ideal candidates for cooling high temperature superconducting devices for its high reliability and high efficiency. The inhomogeneity of flow in a large-diameter pulse tube is one of the main obstacles to develop an efficient cryocooler. In this paper, a Stirling-type pulse tube cryocooler with 100 W-class cooling power at 77 K was developed and tested. A screen-filled secondary water-cooled heat exchanger is used at the hot end of the pulse tube to suppress thejet steaming. Then, attentions were focused on the influence of the pulse tube configurations on the cooling performance. Pulse tubes with different size and taper angle were investigated. With a 100 mm-long cylindrical pulse tube, a cooling power of more than 100 W at 77 K was obtained, and with a 75 mm-long tapered pulse tube of 2.8°, the relative Carnot efficiency of the cryocooler from acoustic work to cooling power reached 29.8%. If the efficiency of the compressor is 80%, the relative Carnot efficiency of the whole system could reach about 24%, showing great attraction to HTS applications. [ABSTRACT FROM AUTHOR]

In this paper, a thermally-driven thermoacoustic refrigerator without any moving parts is reported. This refrigeration system consists of a thermoacoustic Stirling heat engine and a thermoacoustic Stirling refrigerator. Both the subsystems are designed to operate on traveling-wave mode. In the experiment, it is found that the Gedeon DC-flow has significant negative effect on both the heat engine and the refrigerator. To suppress these DC-flows, two flexible membranes were inserted into the two subsystems. The experiment demonstrates that they have worked very well. Then extensive experiments had been made to test the influence of various parameters on refrigeration performance of the whole system. The system has so far achieved a no-load temperature of -65°C, a cooling capacity of about 270 W at -20°C and 405 W at 0°C. In summary, the thermoacoustic refrigeration technology reported here shows a good prospect in room-temperature cooling such as food refrigeration and air-conditioning. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The past two decades have seen great development in thermoacoustic heat engines from standing wave thermoacoustic refrigerators to traveling wave thermoacoustic engines, from small scale thermoacoustically driven pulse tube coolers to large scale gas liquefiers, etc. In the meantime, thermoacoustic theory has also improved, which may be used to generalize the working principles in all oscillating flow heat engines. While thermoacoustic theory has been proved to be very useful in analyzing and modeling thermoacoustic heat engines, there are still some important basic points which are misleading or ambiguous and easily cause confusion. This article clarifies these issues by discussing enthalpy flow, entropy flow, work flow and Gedeon DC flow loss. The clarification is important because it helps one to understand the thermodynamics in thermoacoustic systems and to correctly simulate the system performance, especially when the thermoacoustic theory is extended into a non-linear field considering gas non-linearity, high order thermoacoustic terms, etc. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

In previous thermoacoustically driven pulse tube coolers, the coolers are directly connected to the thermoacoustic engines with connecting tubes as short as possible for less power dissipation. This coupling method limits the amplitude of the pressure waves available to the coolers, which in turn limits the lowest obtainable temperatures. Through our analysis, if we use a connecting tube with length comparable to one quarter wavelength, the pressure wave coming from the thermoacoustic engine will be greatly amplified and drive the cooler to reach a much lower temperature. Experiments have been done on thermoacoustically driven single-stage and two-stage pulse tube cooler and successfully proved the effectiveness of this idea. The pressure ratios of 1.3 and 1.24 were obtained on the single-stage and two-stage pulse tube coolers, respectively, which are much higher than the pressure ratios of 1.1 and 1.13 provided by the thermoacoustic engine itself. With the amplified pressure ratio, the no-load lowest temperatures reached 65.2K and 41K, respectively. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Mixed-gases throttling refrigeration cycles are recuperative cycles. The refrigeration system has at least one heat exchanger and from zero to three or more phase separators. Detailed discussions are made in this paper on the thermodynamic performance of several cycles, including extensive simulations and optimizations of mixtures, operating parameters of pressures, and flow configurations. The results show that the mixed refrigerant is the most important design parameter that influences the performance of the system. From a thermodynamic point of view, the configurations that were studied can all achieve about the same efficiency with an appropriate selection of the mixture and operating pressures. [ABSTRACT FROM AUTHOR]

In this paper, an experimental set up is established to investigate the behavior of the heat exchanger with multi-components mixtures based on a real mixture refrigeration system. Two tube-in-tube heat exchangers with different configurations are tested extensively with different mixtures operating at three typical temperature ranges, such as 80K-100K, 120K-150K, and 180K-200K temperature ranges. The two heat exchangers are fabricated specially to be able to measure the temperatures and pressures distributions. With the measurement of the mixture compositions, temperatures, and pressures, the thermodynamic and hydraulic behaviors of the two heat exchangers are studied extensively. Finally, the heat transfer characteristics are obtained, which is useful in future design of the mixture refrigeration system. [ABSTRACT FROM AUTHOR]

An experimental system is developed to investigate the dynamic characteristics of the mixture composition variations in the closed throttling refrigeration cycle. The experimental results show that the mixture compositions vary at different operating periods of the cycle. The maximum change of the compositions is up to 6% for different operating periods. The unevenness of the mixture compositions at different positions of the system may be up to 12%, or even more. The experimental results will be helpful in the modification of the existing simulation model of the mixture refrigeration cycle as well as the fabrication of mixture coolers. [ABSTRACT FROM AUTHOR]

A new type of mixture refrigeration cycle with reflux exchanger is presented in this paper. In this cycle, a new type of L-V separator with inner heat and mass transfer is employed to replace the combination of conventional L-V separator or complicated rectifier and succeeding heat exchanger used in traditional auto-cascade cycle or Kleemenko cycle. A prototype is developed based on this refrigeration cycle. The thermodynamic performance is discussed as well as some other specifications such as cost, reliability, etc. The experimental results show that this prototype can reach 74W at 135K and 265W at 171K with a nominal input power of 1.5HP. [ABSTRACT FROM AUTHOR]