[Abstract]
The Joule-Thomson cooler (JTC) is a key component of the hybrid cryocooler dedicated to achieving and maintaining the operating temperature of around 2–4 K extensively used in quantum computing and commu nications. To clarify the energy conversion mechanism during the throttling process of the JTC and to improve throttling performance at 2–4 K, a numerical model is developed in which the effect of the complex real physical properties of liquid helium is considered, and the modified Lee phase change model is proposed to meet the operating conditions from supercritical to saturation. The results show that the phase change causes the cooling effect during the throttling process. The larger total energy loss in orifice leads to a higher liquefaction ratio. The liquefaction ratio increases with the increasing orifice thickness and the decreasing orifice diameter and inlet pressure. Given a constant inlet and refrigeration temperature difference, the liquefaction ratio increases with the increase of inlet temperatures. The maximum liquefaction ratio of 93.80% is achieved with orifice thickness of 0.8 mm, orifice diameter of 30 μm, and inlet pressure of 0.32 MPa, assuming an inlet temperature of 4 K and a refrigeration temperature of 3.43 K.
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