Analysis of performance of heat exchangers used in practical micro miniature refrigerators

Narayanan, Sriharini; Venkatarathnam, G.

doi:10.1016/s0011-2275(99)00055-7

Cited by 17 publications

(4 citation statements)

References 3 publications

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“…Several types of heat exchangers for the miniature refrigerators have been proposed [15,[20][21][22] Once the type of a heat exchanger has been selected, the convective heat transfer coefficient can then be determined. In addition to the heat exchanger type and material, the mass flow rate of the working fluid inside the system is also one of the key factors in determining the effectiveness of the heat exchanger.…”

Section: Size Effects Of Miniature Refrigeration and Liquefaction Sysmentioning

confidence: 99%

Size Effects of Miniature Refrigeration and Liquefaction System

Yang¹,

Chung²

2006

Nanoscale and Microscale Thermophysical Engineering

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This article examines the size effects on the performance of miniature refrigerators and liquefiers operated by the Linde cycle. The system sizes are cased into a function of the compressor characteristic length and the heat exchanger length while several cycle operation parameters are held constant. Simplified models of a Hampson-type counterflow heat exchanger and a reciprocating-type compressor were considered in the present analysis.For both the refrigerator and the liquefier, it was found that only for certain ranges of the compressor size is the system able to produce a heat exchanger effectiveness greater than the required minimum value. It was also found that there exists an optimal compressor size for obtaining maximum heat exchanger effectiveness, cooling effect, mass fraction of liquefied product, and coefficient of performance. For the refrigerator, the optimal compressor size for obtaining the maximum heat exchanger effectiveness is different from that for obtaining the maximum cooling effects because of the mass flow rate effect. For the liquefier, the optimal compressor sizes for obtaining the maximum heat exchanger effectiveness, mass fraction of liquefied gas product, and FOM are approximately the same.When the Claude cycle is employed, it is found that it theoretically offers a more satisfactory performance than the Linde cycle in the small size range. The FOM of a mesoscale system with the Claude cycle can reach the range of 20 to 23% with the liquid product temperature ranging from 65 to 90 K.

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Section: Size Effects Of Miniature Refrigeration and Liquefaction Sysmentioning

confidence: 99%

Size Effects of Miniature Refrigeration and Liquefaction System

Yang¹,

Chung²

2006

Nanoscale and Microscale Thermophysical Engineering

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“…13,14 The glass slides are supported by a cylindrical aluminum base that has a rubber O-ring for making a vacuum seal, allowing the cold stage to be enclosed in a vacuum chamber to prevent condensation of atmospheric gases (Fig. Specific performance of a JT micro-refrigerator depends on various dimensions of its construction and has been modeled theoretically.…”

Section: A the Joule-thomson Micro-refrigeratormentioning

confidence: 99%

Use of a Joule–Thomson micro-refrigerator to cool a radio-frequency coil for magnetic resonance microscopy

Wright

Song

Elliott

et al. 2004

Review of Scientific Instruments

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A method is described for cryogenically cooling a rf detector coil, as used in high-resolution magnetic resonance imaging (MRI), to enhance image signal-to-noise ratio (SNR). By incorporating the rf coil into a Joule-Thomson micro-refrigerator, the coil is precision-cooled to 70 K using only a source of high-pressure nitrogen gas at room temperature, avoiding the need for liquid cryogens. The rf coil is insulated by a glass vacuum dewar that permits its use in proximity to biological tissues. Design and operation of the cryogenic system are described and its performance is demonstrated in a 1.5 T clinical MRI scanner with images of a water phantom and a sheep intervertebral disc specimen. SNR gains of two to three times were obtained, compared to a similar coil at room temperature. The potential of this technology for local high-resolution MRI is discussed.

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“…The hydraulic diameter of the etched microchannel is a few to tens of microns. When using N 2 as a refrigerant with the inlet pressure of 10 MPa, it was found that the cooling capacity of the cooler is 250 mW, and the cold‐end temperature is 80 K. Narayanan et al 11 carved a heat exchanger, throttling section and expansion chamber on a stainless steel plate to produce a microchannel J‐T cooler. To decrease the cooler's length, both the heat exchanger and the restriction adopted the structure of the u‐tube.…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical analysis of the multilayer distributed Joule‐Thomson cooler with pillars

Geng

Cui

She

et al. 2020

Intl J of Energy Research

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The conventional Joule-Thomson cooler is not compact in heat exchanger and insufficient in cooling capacity, which is limited in applying integrated electronics. However, microchannels with pillars are effective in increasing the area to volume ratio and enhancing heat transfer through the presence of vortex. Besides, multilayer microchannels are essential to enlarge the mass-flow rate in the cooler. In this study, a multilayer distributed J-T cooler with pillars is investigated. A new mathematical model of the cooler is developed and validated against the experimental data; the relative errors of the temperature and mass-flow rate are both within 5%. Furthermore, the distribution of temperature and pressure in the microchannel is analyzed by the model calculation. Numerical results show that the temperature of the high-pressure fluid decreased slightly under the influence of the heat exchange and distributed J-T effect. When the inlet pressures are 3.00, 4.00 and 5.40 MPa, the cold-end temperatures are 233.0, 185.8 and 161.2 K, respectively, with the cooling capacity reaching 2.25, 3.40 and 3.87 W, respectively. In addition, the influences of the axial heat conduction and heat leakage on the cooling performance are analyzed by using the models. The temperature rise of the cold end increases by 6.8 and 6.2 K at 5.40 MPa, respectively, considering the above two factors. The simulation model provides a useful tool for the J-T cooler.

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Analysis of performance of heat exchangers used in practical micro miniature refrigerators

Cited by 17 publications

References 3 publications

Size Effects of Miniature Refrigeration and Liquefaction System

Size Effects of Miniature Refrigeration and Liquefaction System

Use of a Joule–Thomson micro-refrigerator to cool a radio-frequency coil for magnetic resonance microscopy

Experimental and numerical analysis of the multilayer distributed Joule‐Thomson cooler with pillars

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