Designofan Expander for Internal Power Recoveryin Cryogenic Cooling Plants

МИНИСТЕРСТВО НАУКИ И ВЫСШЕГО ОБРАЗОВАНИЯ РФ

ФЕДЕРАЛЬНОЕ ГОСУДАРСТВЕННОЕ БЮДЖЕТНОЕ ОБРАЗОВАТЕЛЬНОЕ УЧРЕЖДЕНИЕ ВЫСШЕГО ОБРАЗОВАНИЯ

 «ДАГЕСТАНСКИЙ ГОСУДАРСТВЕННЫЙ ТЕХНИЧЕСКИЙ УНИВЕРСИТЕТ»

Кафедра иностранных языков

Реферативный перевод

на тему:

Designofan Expander for Internal Power Recoveryin Cryogenic Cooling Plants

Выполнил:

аспирант 1-го года обучения

научной специальности 13.06.01-

«Электро-и теплотехника»

Магомедов Г.Г.

Махачкала 2023

Designofan Expander for Internal Power Recoveryin Cryogenic Cooling Plants

H.S. Cao1, S. Vanapalli1, H.J. Holland1, C.H. Vermeer2,

T. Tirolien3, H.J.M. ter Brake1

1University of Twente, 7500 AE, Enschede, The Netherlands

2SuperACT, 7559 AJ Hengelo, The Netherlands

3European Space Agency, 2200 AG, Noordwijk, The Netherlands

ABSTRACT

Joule-Thomson (JT) cryocoolers have no moving parts and therefore are vibration-free. These are attractive for cooling small optical detectors in space for earth observation missions. JT cryo- coolers produce cooling by expanding high-pressure gas through a JT restriction. This, however, is a highly irreversible entropy-generating process. If work could be extracted during the expansion process, the efficiency of the cooling cycle would be significantly improved. In this paper, a JT cooling cycle with an additional ejector is proposed. The high-pressure gas, as the primary fluid of the ejector, is used to compress the low-pressure gas leaving the evaporator, thus reducing the cold- end temperature or/and the input power of the compressor. Compared to a basic JT cycle, the im- provement in the COP of the cycle with an ideal ejector is analyzed. The effects of frictional and mixing losses on the real performance of an ejector are estimated through numerical simulations, which aids the understanding of ejector theory and provides information for optimizing the ejector under certain operating conditions.

INTRODUCTION

Joule-Thomson cryocoolers have been used in many applications including cooling of infrared detectors and high-electron-mobility transistor-based devices in space [1], low-noise amplifiers for radio telescopes [2], and cryosurgery [3], among others due to their special features such as compact geometry and absence of moving parts. In a normal JT expansion process, the energy of the high- pressure gas is converted into directed kinetic energy, which is not utilized as work or discharged, but instead is dissipated as heat. This cancels out a large amount of the expansion cooling potential in the gas. Only the Joule-Thomson cooling effect below the inversion temperature remains. Ejectors can use the directed kinetic energy, which is completely wasted in the normal JT expansion, to entrain and compress the low-pressure gas to an intermediate pressure.

Ejectors can be used to reduce the pressure of the evaporator and thereby lower the temperature of the evaporator. Alternatively, ejectors can be used to lift the pressure of the evaporator to a medium pressure and thus reduce the required pressure ratio of the compressor, resulting in less required work of compression. Therefore, an ejector can be used either to lower the pressure (tem- perature) of the evaporator of a JT cooler, or boost the outlet pressure of a JT cooler. The use of an ejector in a JT cryocooler was first proposed by Rietdijk [4] to create subatmospheric pressure in a

[pic 1]

[pic 2][pic 3][pic 4]

[pic 5]        [pic 6]

Figure 1. Schematic of Linde-Hampson cycle with an ejector (left) and corresponding temperature versus entropy diagram (right).

liquid helium evaporator. Daney et al. [5] added an ejector to a JT cryocooler with nitrogen gas as the working fluid. An assemble type ejector was used to characterize the performance of an ejector at different dimensions. Both the primary nozzle and the mixing tube-diffuser were exchangeable. There were three primary nozzles with diameters of 0.58, 0.57 and 0.46 mm and three secondary nozzles with diameters of 6.35, 7.54 and 8.73 mm. Several combinations were tested and the best ejector gave a suction pressure of 0.27 bar and an associated saturation temperature of 67.7 K. Most recent studies regarding the use of ejectors in JT cycle systems are on thermodynamic analysis [6, 7]. Very few of these were experimentally verified. It is known that the performance of an ejector not only depends on the system operating conditions (pressure and environment temperature), but also on its geometry and the working fluid. Many researchers have tried to investigate and describe the flow in an ejector in order to develop a high performance ejector [8-10]. However, not all mysteries in the operation of an ejector have been completely cleared. In this paper, the performance improve- ment of a JT cooler resulting from the addition of an ejector is analyzed. In order to design a JT cooler with an ejector, its performance under certain operating conditions is simulated by means of dynamic modeling. The effects of the operating conditions and the geometry on the ejector perfor- mance are discussed.

OPERATING PRINCIPLE

Figure 1 shows the schematic of a Linde-Hampson cycle with an ejector and corresponding temperature versus entropy diagram. In the cycle, the high-pressure gas flows through the counter flow heat exchanger I (CFHX I), then is split into two streams (at point 2). One stream flowing through CFHX II is expanded through the restriction (between points 3,4) and the other stream flows to the ejector as the so-called primary flow. In the ejector, the high-pressure gas (the primary fluid) expands through the nozzle to create low pressure, and then mixes with the secondary fluid from the CFHX II (at point 6) in the mixing section. The mixed gas increases in pressure in the diffuser section and flows to the CFHX I at the medium pressure (at point 7), rather than at the low pressure of the evaporator.