Inertance Tube Research Articles

Gut churning controls inflammation.

Microbiota The gut is not an inert tube. It undergoes regular contractions called peristalsis. Rolig et al. examined the constant movement in the zebrafish gut and asked whether the enteric nervous system (ENS) plays a role in regulating the microbiota, as well as food flow. If the zebrafish ENS was disabled by knocking out the gene sox10 , intestinal neutrophils accumulated, the gut epithelium proliferated, and inflammation resulted. The inflammation was caused by overgrowth of some bacterial lineages and was resolved by transplantation of ENS precursors or when a well-adapted anti-inflammatory bacterial strain was given to the fish. Thus, peristalsis is important for supressing the growth of poorly symbiotic bacteria, in zebrafish at least. PLOS Biol. 10.1371/journal.pbio.2000689 (2017).

Investigation of the inertance tube of a pulse tube refrigerator operating at high temperatures

1The cooling performance of an inertance pulse tube refrigerator (PTR) is dependent on the impedance at the warm end of the pulse tube provided by the inertance tube. The impedance is influenced by the temperature of the inertance tube. The operation of an inertance tube at a high temperature may be feasible in a PTR, and the effects of a high temperature inertance tube (HIT) on the cooling performance should be investigated. Using theoretical analysis, the dependence of the phase shift ability on the temperature is calculated and analysed. A numerical model of the PTR is built in which different temperatures of the inertance tube are considered to simulate the cooling performance of the PTR with different HITs. Increasing the temperature in the inertance tube decreases the phase shift ability, which weakens the cooling performance. By optimizing the length of the inertance tube, approximately 3.6% and 5.3% decreases in the total input PV power could be obtained for different cooling temperatures when the temperature of the HIT is set at 333 K. Experiments are performed to verify the simulation results.

Studies on the development and efficiency improvement of a 1.5 W at 25 K two stage pulse tube cooler

A high frequency two stage pulse tube cooler (PTC) has been designed using Sage software for a JT-PTC hybrid helium recondensation system. The cold end of the first stage regenerator is anchored at 80 K using a liquid nitrogen supply. Such a thermally coupled design simplifies the design without the need for considering flow distribution between the stages and ensures that entire flow is available to produce cooling power at 25 K. The pulse tube cooler is designed for maximal utilization of the 900 W PV power provided by the Pressure Wave Generator (PWG). With the first prototype, a no load temperature of 40.4 K was achieved at a filling pressure of 24.1 bar. The effect of filling pressure on the acoustic matching of the PTC and PWG was investigated. It is observed that filling pressure has a significant effect on the PWG piston stroke amplitude. Using phasor analysis, it is shown that the phase relationship at different sections of the two stage PTC is detrimentally affected by the pulse tube volume. A scheme for achieving advantageous phasing by reducing the pulse tube volume is proposed. This involves maintaining the hot heat exchanger, inertance tube and buffer volume at 80 K. With the modification it is shown that a beneficial phase reversal across second stage Regenerator is achieved. The method is currently under experimental investigation.

Experimental research on a 12.1 K gas-coupled two-stage high frequency pulse tube cryocooler

High frequency pulse tube cryocoolers (HFPTC) have been widely used in many fields like physics experimental research and aerospace, for no moving part in cold region, low vibration and long life. A gas-coupled two-stage high frequency pulse tube cryocooler with single compressor is introduced in this paper. In the first stage of the cryocooler, double-inlet and multi-bypass has been adopted as phase shifters. To get a better performance in phase shifting the reservoir and the inertance tube of the second stage has been located on the cold head of the first stage. With SS mesh screen as the regenerator of both stage, no-load temperature of 13.5K has been achieved. To improve the heat capacity of the regenerator of the second stage magnetic material Er3Ni has been employed in the second stage as regenerator matrix. With the charge pressure of 1.8MPa, input power of 260W and operating frequency of 23.5 Hz, the no-load temperature of 12.1K has been achieved.

Studies on Phase Shifting Mechanism in Pulse Tube Cryocooler

Pulse Tube cryocoolers (PTC) are being used extensively in spacecraft for applications such as sensor cooling due to their simple construction and long life owing to a fully passive cold head. Efforts at ISRO to develop a PTC for space use have resulted in a unit with a cooling capacity of 1W at 80K with an input of 45watts. This paper presents the results of a study with this PTC on the phase shifting characteristics of an Inertance tube in conjunction with a reservoir. The aim was to obtain an optimum phase angle between the mass flow (ṁ) and dynamic pressure () at the PT cold end that results in the largest possible heat lift from this unit. Theoretical model was developed using Phasor Analysis and Transmission Line Model (TLM) for different mass flow and values of optimum frequency and phase angles were predicted. They were compared with experimental data from the PTC for different configurations of the Inertance tube/reservoir at various frequencies and charge pressures. These studies were carried out to characterise an existing cryocooler and design an optimised phase shifter with the aim of improving the performance with respect to specific power input.

Investigation on phase shifter of a 10 W/70 K inertance pulse tube refrigerator

A 10 W/70 K inertance pulse tube refrigerator (IPTR) has been developed for cooling infrared focal-plane array in a space mission. To investigate the influences of the phase shifter (inertance tube and reservoir) on the cooling performance, simulation models of the IPTR were built and experimental studies were conducted. The effects of reservoir volume and the surface roughness inside the inertance tube on cooling performance of the IPTR were investigated in detail. The optimized parameters of the phase shifter were developed to improve the cooling performance of the IPTR. The results show that a large reservoir volume reduces the optimal operating frequency, decreases the losses in the regenerator and improves the cooling performance of the IPTR. Because of the small surface roughness inside the stainless steel inertance tube, the input electric power of the IPTR is decreased, with a cooling power of 10 W at 70 K. The IPTR achieves 14.75% of the relative Carnot efficiency at 70 K by optimizing the inertance tube and reservoir.

Analysis and comparison of different phase shifters for Stirling pulse tube cryocooler

Investigations of phase shifters and power recovery mechanisms are of sustainable interest for developing Stirling pulse tube cryocoolers (SPTC) with higher power density, more compact design and higher efficiency. This paper investigates the phase shifting capacity and the applications of four different phase shifters, including conventional inertance tube, gas-liquid and spring-oscillator phase shifters, as well as a power recovery displacer. Distributed models based on the electro-acoustic analogy are developed to estimate the phase shifting capacity and the acoustic power dissipation of the three phase shifters without power recovery. The results show that both gas-liquid and spring-oscillator phase shifters have the distinctive capacity of phase shifting with a significant reduction in the inertial component length. Furthermore, full distributed models of SPTCs connected with different phase shifters are developed. The cooling performance of SPTCs using all four phase shifters are presented and typical phase relations are analyzed. The comparison reveals that the power recovery displacer with a more complicated configuration provides the highest efficiency. The gas-liquid and spring-oscillator phase shifters show equivalent efficiency compared with the inertance tube phase shifter. Approximately 10–20% of the acoustic power is dissipated by the phase shifters without power recovery, while 15–20% of the acoustic power can be recovered by the power recovery displacer, leading to a maximum coefficient of performance (COP) above 0.14 at 80K. A merit analysis is also done by presenting the pros and cons of different phase shifters.

Improving Performance of a Switched Inertance Buck Converter Via Positioning of Reservoir Flow Valve

A typical switched inertance buck converter includes digital valves controlling the flow of fluid to the load from the pressure supply and also from the reservoir. These valves are typically located at the same position, often packaged in the form of a single three-way valve, but also sometimes in the form of a two-way high-pressure supply valve and check valve from tank. This results in the situation where attempts to increase flow boosting performance by exploiting reflected pressure waves to draw additional fluid from tank will also tend to draw additional fluid through the valve from the high-pressure supply, causing increased energy loss at the valve. This paper presents a strategy that avoids this tradeoff by locating the tank flow valve along the length of the inertance tube such that the timing of pressure waves arriving at the tank valve can be optimized separately from those arriving at the high-pressure supply valve. A simulation study is presented, in which valve placement and inertance tube resonance are optimized for flow gain or energy efficiency, with results in both cases better than a conventional system with colocated valves. Two strategies for avoiding cavitation are also presented.

Innovative phase shifter for pulse tube operating below 10 K

Stirling type pulse tubes are classically based on the use of an inertance phase shifter to optimize their cooling power. The limitations of the phase shifting capabilities of these inertances have been pointed out in various studies. These limitations are particularly critical for low temperature operation, typically below about 50K. An innovative phase shifter using an inertance tube filled with liquid, or fluid with high density or low viscosity, and separated by a sealed metallic diaphragm has been conceived and tested. This device has been characterized and validated on a dedicated test bench. Operation on a 50–80K pulse tube cooler and on a low temperature (below 8K) pulse tube cooler have been demonstrated and have validated the device in operation. These developments open the door for efficient and compact low temperature Stirling type pulse tube coolers. The possibility of long life operation has been experimentally verified and a design for space applications is proposed.

Impact of coiled type inertance tube on performance of pulse tube refrigerator

An inertance tube is widely used to provide a phase shift between mass flow and pressure wave in pulse tube refrigerator (PTR). The inertance tube is usually coiled around the outer surface of a liner compressor or in a reservoir to reduce installation space. The performance of PTR is strongly influenced by different coiled types of inertance tube. Based on 1-D model (DeltaEC) and 3-D model (CFD), a coupling model is proposed to simulate the cooling performance of a PTR. The characteristics of phase shift and energy flow in the PTR are also analyzed in detail. The simulation results show that the phase shift ability of inertance tube would decrease while increasing the number of coiling turns, which would cause the increase of average mass flow rate within the regenerator. Therefore, more PV power would be consumed for the same cooling capacity. In order to improve the cooling performance of the PTR, it is necessary to adjust the length of the inertance tube when it is coiled. At last, the simulation results are verified by the test results.

The Future of Vascular Biology and Medicine.

During the past several decades, landmark discoveries in the field of vascular biology have evolved our understanding of the biology of blood vessels and the pathobiology of local and systemic vascular disease states and have led to novel disease-modifying therapies for patients. In 1980, Furchgott and Zawadzki1 radically changed our focus in blood vessel research with the discovery of endothelium-derived nitric oxide and its effects on vascular tone. This seminal discovery redefined blood vessels as dynamic organs with autocrine, paracrine, and endocrine functions that are capable of regulating their own environment. The later recognition that many risk factors associated with vascular disease perturb nitric oxide-mediated homeostatic mechanisms lent further credence to the concept of blood vessels as complex organs rather than inert tubes. In the decades to follow, research in vascular biology predominantly targeted 3 facets of vascular function: vasomotor tone, inflammation, and the balance between thrombosis and thrombolysis. This occurred because atherosclerotic cardiovascular disease reached epidemic levels and atherothrombosis was found to feature disturbances in these functions that preceded visible pathology and clinical manifestations of the disease. Furthermore, modification of responsible causal factors reversed impaired vascular function (eg, lowering levels of low-density lipoproteins in atherosclerosis), and clinical studies began to validate the importance of preclinical vascular biology research in the treatment of hypertension, atherosclerosis, pulmonary vascular disease, erectile dysfunction, Raynaud phenomenon, and neointimal proliferation after mechanical vascular intervention. More recently, advances in molecular biology and –omics technologies have facilitated in vitro and in vivo studies that revealed that blood vessels regulate their own redox milieu, metabolism, mechanical environment, and phenotype, in part, through complex interactions between cellular components of the blood vessel wall and circulating factors. These interactors include stem, progenitor, and differentiated cells; microRNAs, long noncoding RNAs, and DNA; and, hormones, proteins, and lipids. Dysregulation of these …

CFD modeling and experimental verification of a single-stage coaxial Stirling-type pulse tube cryocooler without either double-inlet or multi-bypass operating at 30–35 K using mixed stainless steel mesh regenerator matrices

This paper presents the CFD modeling and experimental verifications of a single-stage inertance tube coaxial Stirling-type pulse tube cryocooler operating at 30–35K using mixed stainless steel mesh regenerator matrices without either double-inlet or multi-bypass. A two-dimensional axis-symmetric CFD model with the thermal non-equilibrium mode is developed to simulate the internal process, and the underlying mechanism of significantly reducing the regenerator losses with mixed matrices is discussed in detail based on the given six cases. The modeling also indicates that the combination of the given different mesh segments can be optimized to achieve the highest cooling efficiency or the largest exergy ratio, and then the verification experiments are conducted in which the satisfactory agreements between simulated and tested results are observed. The experiments achieve a no-load temperature of 27.2K and the cooling power of 0.78W at 35K, or 0.29W at 30K, with an input electric power of 220W and a reject temperature of 300K.

A novel coupled VM-PT cryocooler operating at liquid helium temperature

This paper presents experimental results on a novel two-stage gas-coupled VM-PT cryocooler, which is a one-stage VM cooler coupled a pulse tube cooler. In order to reach temperatures below the critical point of helium-4, a one-stage coaxial pulse tube cryocooler was gas-coupled on the cold end of the former VM cryocooler. The low temperature inertance tube and room temperature gas reservoir were used as phase shifters. The influence of room temperature double-inlet was first investigated, and the results showed that it added excessive heat loss. Then the inertance tube, regenerator and the length of the pulse tube were researched experimentally. Especially, the DC flow, whose function is similar to the double-orifice, was experimentally studied, and shown to contribute about 0.2K for the no-load temperature. The minimum no-load temperature of 4.4K was obtained with a pressure ratio near 1.5, working frequency of 2.2Hz, and average pressure of 1.73MPa.

10 K high frequency pulse tube cryocooler with precooling

A high frequency pulse tube cryocooler with precooling (HPTCP) has been developed and tested to meet the requirement of weak magnetic signals measurement, and the performance characteristics are presented in this article. The HPTCP is a two-stage pulse tube cryocooler with the precooling-stage replaced by liquid nitrogen. Two regenerators completely filled with stainless steel (SS) meshes are used in the cooler. Together with cold inertance tubes and cold gas reservoir, a cold double-inlet configuration is used to control the phase relationship of the HPTCP. The experimental result shows that the cold double-inlet configuration has improved the performance of the cooler obviously. The effects of operation parameters on the performance of the cooler are also studied. With a precooling temperature of 78.5K, the maximum refrigeration capacity is 0.26W at 15K and 0.92W at 20K when the input electric power are 174W and 248W respectively, and the minimum no-load temperature obtained is 10.3K, which is a new record on refrigeration temperature for high frequency pulse tube cryocooler reported with SS completely used as regenerative matrix.

Modelling of pulse tube refrigerators with inertance tube and mass-spring feedback mechanism

Most of the current Stirling-type pulse tube refrigerators (PTRs) adopt inertance tubes with large reservoirs for phase shifting. Recovering the acoustic power dissipated in the inertance tube provides a great potential for improving the efficiency of a PTR. In this study, an inertance tube PTR is modified by replacing the dissipative inertance tube and reservoir with a mass-spring displacer directly coupled to a compression space. Numerical simulations are conducted on both the PTRs based on a validated one-dimensional computational fluid dynamics model. Optimization of the inertance tube PTR shows that the coefficient of performance (COP) is limited within 0.103 at the cooling temperature of 77K. The simulation of the PTR with the feedback mechanism indicates that COP can be significantly improved due to the extra power recovered by the mass-spring displacer. The parametric analyses of the moving mass, spring stiffness, mechanical resistance, piston diameter, and working frequency of the mass-spring displacer are finally performed. The phase relations at both ends of the regenerator are significantly influenced by the geometric and operating parameters, which further affect the performance. The designing parameters have been optimized, COP reaches about 0.13–0.14 with the relative Carnot COP of around 0.4. It demonstrates that adopting the mass-spring displacer to feed the expansion power back into the compression space is an effective way of improving the performance of PTRs. This work provides comprehensive understanding of the mechanisms and characteristics of the PTRs with the mass-spring displacer. It would be helpful for future designs of such systems.

Four operation modes of a pulse tube machine with a step piston compressor

An inertance tube pulse tube refrigerator with a step piston compressor is a reversible refrigerator which means that it can be operated as a refrigerator, a cold engine, a heat engine, and a heat pump. We call it as a pulse tube machine. In this paper, a numerical simulation is conducted on an inertance tube pulse tube machine with a step piston compressor. The result shows that the pulse tube machine can work as a refrigerator, a cold engine, a heat engine, and a heat pump, depending on the swept volume ratio of the step piston compressor.

Heterogeneous Catalytic Polymerization of Ethylene in Microtubular Reactor Systems

AbstractThe feasibility of using a microtubular reactor for heterogeneous polymerization of ethylene was investigated experimentally. Chemically inert polymer tubing of 800–2300 μm in inner diameter was fabricated and used as a polymerization reactor. Nonporous silica nanoparticles with a diameter of 400 nm were synthesized and used as support for the high‐activity rac‐ethylene(indenyl)2ZrCl2 catalyst with methylaluminoxane as cocatalyst and toluene as diluent. Large‐diameter microtubular reactors were also successfully used to conduct heterogeneous polymerization of ethylene in continuous reaction operations. High initial catalyst activity was obtained and the overall polymerization activity per volume or reactor length was quite high. No particle fragmentation occurred and the polymer particles were covered with small subgrains or nanofibrils with a diameter of 30 nm.

Investigation on thermal coupled three stage pulse tube cryocooler

Pulse Tube Cryocoolers (PTCs) have been investigated in recent times with the focus on achieving much lower temperature and reliable operation. Lower temperatures can be obtained by cascading the stages of the PTC. These stages can either be gas coupled or thermal coupled. This paper presents the design and development of two different configurations of three stage thermal coupled PTC, one with room temperature phase shifting mechanism (PSM) and the other with cold phase shifting mechanism. For room temperature PSM, the first and second stage are provided with inertance tube, while that for the third stage is provided with inertance tube and a double inlet valve. For the cold PSM, only an inertance tube is used as a phase shifter. In case of PTC with room temperature PSM, a minimum temperature of 19.61 K is achieved with a refrigerating effect of 220 mW at 30 K at the cold end of the third stage pulse tube, with an input power of 600 W. While for the PTC with cold PSM, a minimum temperature of 32.41 K is achieved. A reliability test is carried out; the PTC performed well during the entire operation and the repeatability is established.

Performance of an adjustable, threaded inertance tube

The performance of the Stirling type pulse tube cryocooler depends strongly on the design of the inertance tube. The phase angle produced by the inertance tube is very sensitive to its diameter and length. Recent developments are reported here regarding an adjustable inertance device that can be adjusted in real time. The inertance passage is formed by the root of a concentric cylindrical threaded device. The depth of the threads installed on the outer screw varies. In this device, the outer screw can be rotated four and half turns. At the zero turn position the length of the passage is 1.74 m and the hydraulic diameter is 7 mm. By rotating the outer screw, the inner threaded rod engages with additional, larger depth threads. Therefore, at its upper limit of rotation, the inertance passage includes both the original 1.74 m length with 7mm hydraulic diameter plus an additional 1.86 m length with a 10 mm hydraulic diameter. A phase shift change of 24° has been experimentally measured by changing the position of outer screw while operating the device at a frequency of 60 Hz. This phase angle shift is less than the theoretically predicted value due to the presence of a relatively large leak through the thread clearance. Therefore, the distributed component model of the inertance tube was modified to account for the leak path causing the data to agree with the model. Further, the application of vacuum grease to the threads causes the performance of the device to improve substantially.

Raytheon Advanced Miniature Cryocooler Characterization Testing

The Raytheon Advanced Miniature (RAM) cryocooler is a flight packaged, high frequency pulse tube cooler with an integrated surge volume and inertance tube. Its design has been fully optimized to make use of the Raytheon Advanced Regenerator, resulting in improved efficiency relative to previous Raytheon pulse tube coolers. In this paper, thermodynamic characterization data for the RAM cryocooler is presented along with details of its design specifications.