Performance study on layered microchannel distributed throttling cryocooler with different working fluids

doi:10.11949/0438-1157.20250135

Abstract

Abstract:

Considering the small number of channels and low cooling capacity of current microchannel throttling cryocoolers, a multi-layer, multi-channel parallel printed circuit board microchannel throttling cryocooler is designed. The channel structure of the cryocooler is a combination of microchannels with different cross-sectional sizes to achieve different functions. It is used for reheating and pre cooling in a heat exchange channel with an equivalent diameter of 0.46 mm, and distributed throttling cooling and regenerative pre cooling coupling within a throttling channel with an equivalent diameter of 0.12 mm. Analyze the refrigeration performance of the cryocooler under different inlet pressures of 2.01—8.02 MPa using Ar as the working fluid. The results show that under various operating conditions, the heat exchange of the heat recovery device is relatively sufficient, and the distributed throttling components have significant cooling ability. When the inlet pressure of Ar gas is 8.02 MPa, the lowest temperature of 158.5 K can be reached, and the temperature gradient of the pre cooling section and throttling section reaches 0.79 and 1.04 K/mm, respectively. When the inlet pressure of Ar is 6.00 MPa, the cold end temperature is 196.7 K, accompanied by a parasitic cooling capacity of 2.73 W. At a cold end temperature of 219.8 K, it has a total cooling capacity of 6.08 W, which is significantly improved compared to similarly sized throttling cryocooler. Comparing the experimental results of Ar and N₂ in microchannel throttling cryocooler, the cold end temperature that Ar can reach is always lower than that of N₂ under similar operating conditions. But at the same outlet pressure, N₂ has the potential to reach a lower limit temperature. In addition, the operating characteristics of distributed throttling are analyzed through the J-T effect. The coupling effect of heat exchange and J-T effect shows that the thermal and heat transfer processes have different rules. Compared with adiabatic throttling, the throttling process has a higher system completion degree and increased J-T efficiency, which can alleviate the heat exchange pressure of the pre-cooling mechanism before throttling.

Key words: microchannels, throttling refrigeration, Joule-Thomson effect, heat transfer, hydrodynamics

摘要：

针对目前微通道节流制冷器通道数量少、制冷量小的特点，研究开发了一款多层、多流道并行印刷电路板式微通道节流制冷器。该制冷器内不同截面尺寸的微槽道相搭配以实现不同功能，在当量直径为0.46 mm的换热通道内回热预冷，在当量直径0.12 mm的节流通道内分布式节流降温与回热预冷耦合。以氩气为工质，分析2.01~8.02 MPa不同入口压力下制冷器的制冷性能。结果表明，各工况下，回热装置换热较充分，分布式节流部件具有显著的降温能力。当入口压力为8.02 MPa时，可达到158.5 K的最低温度，回热段与节流段温降梯度分别达到0.79和1.04 K/mm；当入口压力为6.00 MPa时，冷端温度为196.7 K，并伴随有2.73 W的寄生制冷量；在219.8 K的冷端温度下具有6.08 W的总制冷量，相较于相似特征尺寸的节流制冷器，有了显著提高。对比氩气和氮气在微通道节流制冷器中的实验结果，氩气所能达到的冷端温度总是低于相似工况下的氮气；但在相同出口压力下，氮气具有达到更低极限温度的潜力。另外，通过J-T效应分析分布式节流的运行特征，换热与J-T效应的耦合作用，热力和传热过程有不同规律，相较于绝热节流，节流过程系统完成度更高，J-T效率增加，可以缓解节流前预冷机构的换热压力。

关键词: 微通道, 节流制冷, Joule-Thomson效应, 传热, 流体动力学

CLC Number:

TB 61⁺1

Hailong SHE, Guangzhong HU, Xiaoyu CUI, Zhongbin LIU, Di PENG, Hang LI. Performance study on layered microchannel distributed throttling cryocooler with different working fluids[J]. CIESC Journal, 2025, 76(8): 4017-4029.

佘海龙, 胡光忠, 崔晓钰, 柳忠彬, 彭帝, 李航. 不同节流工质下叠层微通道分布式节流制冷器性能研究[J]. 化工学报, 2025, 76(8): 4017-4029.

Figures/Tables 22

Fig.1 Schematic diagram of throttling refrigeration

Fig.2 T-S diagram of throttling refrigeration

Fig.3 Physical picture of microchannel throttling cryocooler

Fig.4 Structure of microchannel throttling cryocooler

Table 1 Structural parameters of microchannel throttling cryocooler

位置	尺寸
入/出口段	10 mm
高压回热段	0.55 mm × 0.40 mm × 105 mm
高压节流段	0.15 mm × 0.10 mm × 40 mm
低压回热段	0.55 mm × 0.40 mm × 145 mm
膨胀腔	10 mm, 150°
整体长度	165 mm

Fig.5 Rotation temperature of gases

Fig.6 Relationship between J-T coefficients of various gases and changes in pressure and temperature

Fig.7 Experimental system

Fig.8 Layout of temperature measuring points

Table 2 Accuracy and range of instruments

测量设备	精度	量程
入/出口热电偶(T1/T9)	± 0.5 K	73~573 K
T型热电偶(T2~T8)	± 0.2 K	113~373 K
入口压力传感器	± 0.5%	0~10 MPa
出口压力传感器	± 0.5%	0~1.5 MPa
质量流量计	± 1.0%	0~300 SLPM

Fig.9 Temperature of measuring point versus time

Fig.10 Mass flow and outlet pressure versus time

Fig.11 Temperature distribution of each measuring point along the length

Fig.12 Stable temperature distribution at each measuring point under different loads

Fig.13 The effect of loads on cold end temperature and mass flow

Fig.14 Cooling capacity under different loads

Fig.15 The cold end Temperature of N2 and Ar versus time

Fig.16 Comparison of stable cold end temperatures of Ar and N2 under different pressures

Fig.17 Comparison of J-T coefficients between N2 and Ar

Fig.18 Comparison of saturation Parameters between N2 and Ar

Fig.19 J-T coefficient varies with temperature and pressure during different throttling processes

Fig.20 J-T coefficient varies with temperature and pressure

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