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Coaxial Pulse Tube Cryocoolers

Coaxial Pulse Tube Cryocoolers

Coaxial Pulse Tube Cryocoolers

The University of Sussex

SCHOOL OF ENGINEERING & INFORMATICS

Cover sheet for Year 3 Individual Project

Interim report

CANDIDATE NUMBER:

118521

 

 DEPARTMENT:  ENGINEERING

 
TITLE OF MODULE:

H1043 INDIVIDUAL PROJECT

 

 
TITLE OF ASSIGNMENT:

INTERIM REPORT

 
Date due:     01.12.16

 

 Date submitted: 01.12.16
 

DECLARATION:

In making this submission I declare that my work contains no examples of misconduct, such as plagiarism, collusion, or fabrication of results.

 

I confirm that I have talked with my project supervisor about whether ethical review will be required, and that the outcome of the discussion is included in my interim report.

 

Should ethical review be required, I confirm that I will submit an application before the end of the autumn term. Furthermore, if the ethical implications of my project change, I confirm that I will alert my supervisor immediately.

SIGNATURE:  

Adham Alaa

                                                                              

 

 

 

 

  1. Tutors are normally required to return marks and feedback to students within 15 term time working days of the date set for submission.
  2. Some assignments will be kept for ratification by the Exam Board. Students are encouraged to take a copy of their work before submission as it may not be returned.

 

 

 

 

 

 

 

The Optimization and Designing of a Pulse Tube Cryocooler

 

 

By

 

 

 

 

 

 

 

Individual Project

 

Professor:

 

The University of Sussex

 

Brighton, England.

 

Date.

 

 

 

 

 

 

 

Project Objectives

  • Modification of the variables and structures in attempts to achieve optimum efficiency, maximum reliability, increased compactivity and substantial reduction of the overall costs.
  • Design a coaxial pulse tube cryocooler with specific dimensions
  • Stimulation of the performance properties at various conditions such as a drop-in pressure, mechanical stabilization and improvement, velocity, informality as well as the transfer, distribution and loss of heat.
  • Compare the coaxial cryocoolers with other coolers and the geometrical arrangements.
  • Comprehend how the pulse tube cryocooler work and how it could be applied in real life situations.
  • Highlight the possible error sources in the entire research as well as the best safety measures to be applied in the entire process.
  • Use the sage model to retrieve the boundary conditions
  • Optimization of the coaxial pulse tube cryocooler to achieve the best efficacy with the most applicable cooling power and the lowest possible temperatures.

Pulse tube cryocooler description:

The pulse tube cryocooler is in essence composed of two major parts: the linear compressor and the cold finger. The cold finger is where electricity is transformed to acoustic power which shows as an oscillated flow at the main compressor whereas at the cold finger, it is used to create refrigeration without having to move any of the parts of the cooler. In general terms, the cryocoolers apply the flowing oscillations which are produced in the compressor, the regenerative exchangers of heat and the cold displacer/finger, facilitated by the warmth generated thereof. The cold displacer is responsible for the maintenance of the gas therein in proper motion and phase using the aforementioned pressurized oscillations as it were. This action enhances the effective creation of a line between the heating and the cooling effects of the entire cooler. In the Pulse Tube Cryocooler, the cold finger has been designed into a piston which has the capacity to move at what has been termed as cryogenic temperatures (Xu, 2012). The piston ensures that there is a great temperature difference in the cold finger but a negligible difference in pressure. It is worth noting that the displacer in the pulse tube cryocooler is generally replaced with a pulse tube. This, essentially a tube brimful of the helium gas which takes up the roles of the displacer, initiating a boundary between the cooling and the heating parts of the cryocooler. Nevertheless, the tube ought to be carefully put in place to ensure that the possible mixing of the helium gas has been averted and that the possible occurrence of heat transfer by convection has been forestalled. Otherwise, the two occurrences would negate any efficiency endeavors of the entire cooling process (Radebaugh, 417, 2010).

With the replacement of the displacer, the pulse tube cryocooler has proved to be more reliable with reduced vibration of the moving parts. This phenomenon provides even more advantages for those who apply the whole idea of the cryocoolers. Typical working capacities for the commercial pulse tube cryocoolers may generally range from 35-100 W at 78–80K, 6–22 W at 20K and 1-1.5 at 4.2K. Their high reliability as well as the reduced vibrations makes them the first choice in many space activities (Kamoshita et al, 321, 2011).

 

 

 

 

 

Abstract

There has been a need for large coaxial pulse tube cryocoolers that are efficient and of high frequency. The inertness of such coaxial pulse tube cryocoolers has made it prove effective to be used in different areas that require high temperatures and high efficiency. The primary goal of the advancement is to give bigger low-commotion cooling powers in the scope of 80-100 K for space-borne infrared-detector frameworks. In this paper, the performance and design improvement methodologies will be examined, and the designing models for them are in work. A split double pressurized cylinder with a linear compressor that has an extremely cleared volume of 8.2cc is utilized. The general weight without cooler control hardware is under 7.0 kg. At present, the coolers have accomplished more than 13% of Carnot at 80 K or 15% of Carnot at 100 K. The ordinary cooling execution of the coolers gives 6 W at 80 K or 9 W at 100 K with around 122 W of the electric input control and a 313 K dismissal temperature. There have been various ways aimed at improving the coaxial pulse tube cryocoolers, and this paper goes a step further to outline that.

The Pulse Tube Cryocooler

Introduction

The Pulse Tube cryocoolers have been designed to suit a variety of applications based on range of temperatures with the inclusion of the 10-40K range. This range is generally used in most of the space applications, the physics of condensed matter among other fields. In addition, is the range 50-65K which has been used in the HgCdTe-based detectors which use longer wavelengths, making it quite effective. Without mentioning this, there also is the range 80K which is mainly applied in the extreme temperature superconductivity energy technologies that have gone commercial around the globe. Nevertheless, the heating and cooling power may differ depending on the application as well the temperatures needed (Xu, 617, 2012).

To advance the current benchmark design of the coaxial pulse tube cryocoolers to fit the needs of the clients, researchers have been chipping away at a few of the basic components in the coaxial pulse tube cryocoolers. This streamlining ought to prompt a more extensive use of these pulse-tube cryocoolers into the top but civic applications. This dissertation portrays the advancement of the heat exchangers at the warm end, the cold end and the cradle including irreversible heat losses that are brought about by disturbances of the gas stream. Also, the exchange of heat at the ends to the surroundings has been examined. Likewise, the affectability to inside pollution has been tried and proven.

Results will help in design improvement of the entire scope of coaxial pulse tube cryocoolers, differing from 2 and 5 W at 85 K to coaxial pulse tube cryocoolers. In this dissertation, test result and advantages of the newer designs will be assessed.

Coaxial pulse tube cryocoolers are appropriate for a wide range of temperature reaches including the 10-40 K range which is required for space application, consolidated matter material science and some different fields. Likewise, there is the 50-65 K temperature range which is an imperative one since infrared indicators that are HgCdTe-based can work successfully within the required range. There is additionally the 80 K extend which is required for high-temperature superconductivity control network advancements which include business applications. Notwithstanding, cooling power and electric input power tends to differ as indicated by each application and temperature range required. Interestingly with different cryocoolers like the Stirling cryocooler, Brayton cycle cooler, Gifford-McMahon cryocooler and evaporative cooler, the coaxial pulse tube cryocoolers offer another element which is the disposal of any moving segment exposed to the cold head of the gadget. This tends to be different from the displacer which is utilized as a part of all other cryocoolers keeping in mind the end goal having the gas expanded. The nonappearance of any moving segment at the cold head conveys many favorable circumstances to it. Long life, low vibrations, reliability in operation, and short size makes it reasonable for a wide range of uses. The coaxial course of action is the most minimal one; it can draw on the experience of coupling, facilitate the framework incorporation and decrease the cost, subsequently, it is utilized as a part of space and military applications. The in-line geometrical game plan is the most effective one as it requires no void space at the cold end to turn around the flow bearing which is different from the coaxial course of action but then again, the burden of coupling cooled gadgets because of the cold head situated between two warm plates makes it not appropriate for some applications

Different from other coolers, such cryocoolers as the evaporative cooler, stirling cryocooler, Gifford-McMahon cryocooler as well as the Brayton cycle cooler, the pulse tube cryocooler gives a new dimension which is basically the removal of any movable component in the cold finger of the gadget. This is totally unlike the displacer which is the backbone of the many cryocoolers available, with the intentions of expanding the helium gas. This absence of movable components at the cold finger has born a number of advantages. Some of the most notable advantages in this case include: simple fabrication, reliable operation, durability, reduced vibrations and compactivity which makes it suitable for generally any applications in the field of refrigeration. With regards to compactivity, the coaxial arrangement has the largest degree of compactivity. For this reason, this arrangement can simplify the integration of the cryocooler as well as reduce the average cost of this integration. On the basis of this advantage, the device is used in the space and military applications. Conversely, the geometrical arrangement of the has proven to be the most effective. This is because it may not need any vacuum at the cold finger of the device to make a reverse of the flow direction as the coaxial arrangement would require. However, the issue of the coupling of the cooled devices springing from the cold piece of metal sandwiched between either of the two warm ends makes it suitable for a variety of applications (Xun et al, 281, 2013).

Substantial work has been done and reported on the Pulse Tube Cryocoolers. Presently there is so much work that goes on the creation of designs that would optimize the functionality of the cryocooler. Owing to the many improvements that have been made of the device, its application limits are being expanded by the day. In most cases, the pulse tube cryocoolers are fast replacing the Stirling cycle cryocooler in the miniature cryocoolers (Wen et al, 401).

The pulse tube cryocoolers, have been specially designed to be applied where the objects in question require minimal vibrations. In this case and as observed earlier, the elimination of the movable components in the pulse tube reduces the impact of the possible vibrations at the colder detector end. This is made possible by the fact that the cryocoolers generating the cooling effect at temperatures of about 80K.What is more, the perfectly combined functionality of the cold head without the movable components and the highly bankable magnetic compressor guarantees the efficiency of this device (Xun et al, 283, 2013).

In the most recent reports about the pulse tube refrigerators, these devices have the capacity to have a wide application based on the fact that they produce low heat. The most ubiquitous pulse tube cryocoolers are designed to either be regenerative and recuperative. On the basis of the pulse tube as well as the regenerator the cryocoolers could be designed in a number of such configurations as: Inline, annular, coaxial and u-shape (Xu et al, 281, 2012).

The new uses of the pulse tube cryocoolers are growing by the day and the requirement for the old uses are fast being phased out. The new and variant requirements for the cryocoolers are and have been an impetus as well as a boon for the most contemporary cryocoolers. Nevertheless, the lack of the right types of cryocoolers to meet certain needs has been the stumbling block for any possible applicational advancement. In this case, the major issues that have been associated with the cryocoolers include among others: size, weight, reliability, vibration, cost and efficiency (Radebaugh, 423, 2010).

The magnitude of each of these issues mainly hinges on the mode of application in question. In a period of the last 16 years, the utilization of the satellites using the infrared remote sensors have taken a vital turn of events. Most definitely, this utilization necessitates the presence of a cryocooler which has relatively high efficiency, compactivity, reduced vibrations, reduced weight and relatively low cost implications (Kamoshita, 327, 2011).

In this sense, a substantial number of cryocoolers have been developed mainly focusing at the single purpose of their applications in space expeditions. Similarly, most of the recent development of the Stirling cryocoolers have been based on the improvement of the reliability of the device. The extensive development as well as research on the pulse tube cryocooler by any industries has been taken serious for its potential to have improved simplicity, low cost and/or reliability.

There are many industries that have been involved in the designing and/or improvement of the pulse tube cryocooler. Among other industries, the Netherlands-based -Thales Cryogenic BV has been the most effective in the actual optimization and designing of the device. Most recently Thales Cryogenics has made a milestone by designing the kind of a cryocooler (which is currently in full-throttle production) with a generally good performance outcomes with its 1.5 W pulse coolers running at 80K (Radebaugh, 430, 2010).

The designed coolers are mainly made up of compressors that are mainly founded on a reliable and a highly-recommended technology as well as the pulse-tube cold fingers which work based on the rationale behind the functionality of the CEA/SBT design (a design that has more often than not been optimized by the Thales. As a matter of fact, in 2007, Thales designed and tested an even more powerful LPT9710 pulse tube cryocooler that has been proven to produce a more cooling power which operates at 15W and at 80K.In all reasoning, the LPT9710 pulse tube cryocooler was found to be cost-effective, high-efficacy and low vibrations which enhances its capacity to attain high cooling abilities and relatively low temperatures. These temperatures have been measured and found to be as low as 40K (Kamoshita, 315, 2011).

Thales Cryogenics BV has for the longest time now been designing and testing pulse-tube cryocoolers using an indoor U-shaped pulse-tube refrigerators (PTRs) design. In later years, the company developed the coaxial PTR’s which was designed in line with the CEA/SBT.This was a milestone that would later bore such production models as LPT9310 as well as the LPT9510 with cooling capacities ranges of 1W and 4 W at 80K respectively (1,2) (Yang et al, 344, 2010). The LPT9310 makes a perfect combination of efficiency and/or reliability which is facilitated by the LSF93xx compressors which has a coaxially arranged pulse tube and an incorporated buffer. These features made the gadget more reliable and highly performing for a myriad of applications. On the other hand, the LPT9510 makes an unerring combination of both power and reliability of the LSF95xx compressors which have coaxially arranged pulse tubes with an integrated buffering system (Yang et al, 345, 2010). Similarly, this features results in compacity, satisfactory performance and reliability making it suitable for a variety of applications. In general, the LPT cryocoolers are suitable for almost all the applications that would require extremely minimal levels of acoustic disturbances and/or electromagnetic vibrational interference. The models of the LPT9310 and the LPT9510 respectively are as shown below (Xun et al, 284, 2013).

Fig 2: LPT9310.

 

Fig 3: LPT9510

Most of the contemporary versions of the pulse tube cryocoolers are the commercial versions of the prototypes that were designed by CEA.These versions have been designed using the state-of-the-art materials as well manufacturing technologies. The typical manufacturing technologies that would be required in the designing and optimization of a cooler include the wire-EDM (electrical discharging device), high-vacuum brazing as well as the electrical beam welding. For the purpose of ensuring a broader application of the pulse-tube cryocoolers, continuous improvement on as well as the balancing of specifications, performance and costs required. In this regard, the Thales company conducted a research in the attempts to improve on the manufacturability of the device while maintaining the high-efficacy and cooling capacity that features in its current model and the same time raising the hopes high for the designing of a pulse tube cryocooler with an increased overall performance degree (Pan et al, 22, 2016).

This research article will address various aspects of the general optimization of the pulse tube coolers in terms of the exchangers of heat, improving on the physiology of heat sinking, the optimal maximization of manufacturability as well as the reduction of costs. Additionally, this article further lays bare the advancement of a new creation of the LPT coaxial pulse tube cryocooler dubbed the LPT9710.The new pulse tube creation has the capacity to make more than 15W with a cooling capacity that stands at 80K.The device has been fully designed to by the Thales company and is basically ran by a completely recently designed compressor. The advancement of the 300W PdV compressor will be described at length in the latter sections (Hu et al, 9, 2014).

Fig 4: LPT9710

Summary

In summary, the 10-40K has proven to be an important research compass for extreme frequency pulse tube cooler owing to its significance in the space applications. In this case, the lowest temperature attained in the usage of one stage extreme frequency multi pulse tube cryocooler stood at 18.6K with an estimated electrical input of power of 266 W.On the other hand, the cooler one would in essence provide 0.3/ 21.6K and 0.6/24.1 at about a temperature record of 300K (the room temperature) (Yang et al, 343, 2010).Additionally, the multi-layered structure of the PTC (the pulse tube cryocooler ) is better placed to attain the low temperatures whereas the single-staged is simpler due to the associated mechanical simplicity associated with it.Moreover, it is also associated with extreme reliability a well as low vibrational issues. This would mean that, it will be better to use the single-layered structure but keep the most essential parameters at their optimum levels in order to fully improve the cooling effect and attain reach the lowest possible temperature that will be needed (Pan et al, 22, 2016).

Nevertheless, many trials have been done to attain the lowest temperature using the single layered structure. Based on the outcomes of results conducted by Giessen, a single structured PTC with no multi-bypass at 250W electric power input, would attain a temperature which will be as low as 26.1K. Similarly, Giessen had it that cooler would a capacity to provide a cooling effect of 0.2W/30K with an average input power of 200K (Dang et al, 47, 2016).

Lockheed Martin created an in-line geometrical PTC with a low temperature (a no-load temperature) of 23K by utilizing a multi-bypass. He approximated that the cryocooler would present 0.32W/35K.Similarly, Yang created a PTC with a multi-bypass that attained 23.8K and 0.6W at 35K cooling effect. Additionally, a corporation of Chinese engineers with the inclusion of Yuan Zhou and Qiang Zhou created an advanced PTC, dubbed p-06. This was newly discovered compact PTC managed to produce a temperature of 19.3K at 200 W power input and the cooler on average produces 1W/38.9K via the compressor and the PTC is connected by the use of a connecting tubing (Yang et al, 344, 2010).

Initially, the development of the three-stage PTC device, the hardware logistics from the two and single-staged PTC was taken advantage of as the foundation for its design and improvements. As a matter of fact, such a designing improvement was reported to have significantly increased the performance of the hardware of the single-staged PTC configuration. Based on several studies, the in-line, U-tube and stage configurations of the PTC staged 5.2W at 77K, 4.8W at 77K and no-load at 80K cooling effects respectively (Chen et al, 55, 2013).

The PTC configurations

Fig 5: The PTC configurations

Nevertheless, to achieve a higher cooling effect that exceeds p-06, a new coaxial PTC with increased compactivity is utilized to make a creation of P-07 that is able to go as low as 18.6K in temperature and reaches a cooling effect of 0.2W/20.6 K. This new creation will be applied in physical property measurements where various types of materials will have to be cooled down to a temperature of between 20 and 40 K in order to have a measurement of their physical characteristics (Xu et al, 678, 2012).

Without mentioning this, the 55-65 K range of  temperature has been created to enhance appropriate cooling effect in the subsequent generation of the very big scale long wave focal plane arrays in the wake of their emergence from a single element headed for the to the focal plane arrays until such a time that they reach the VLSFPA’s which then introduces a sharp upward mobility of the cooling needs that are transformed from hundreds of milliwatts to between 1.0-3.0 W which may even increase up 4W which is the necessary requirement for the forthcoming generation (VLSFPA) (Pan et al, 24, 2016).

At around 1996, the TRW made a profound milestone; here the 70K temperature range technology when the TRW 6020 was created and managed to deliver 2.0W at 60K for 78W inside the compressor at 300K temperature. These results were quite impressive at that moment since the efficacy of the system went beyond the ones of stirling cryocoolers. Lockheed Martin created a replica of the coaxial; PTC in the early 1990s where it had the same frequency as those of the TRWs (Radebaugh, 420, 2010).

To wrap up, the high range of superconductivity temperature power connection technologies need a cooling effect of more than 100 W which is relatively high when compared to a normal cooling ability of less than 10W.The High Temperature Superconductivity (HTS) technological concepts need function within the limits of the liquefied nitrogen temperatures which is extremely practical to various life aspects with the inclusion of the infrared detection model in the aerospace. Compared to such cryocoolers as the Brayton, the PTC has been considered to be more efficient given their increased power yielding (Wen et al, 403, 2015).

Optimization of Dimensional Parameters

The design and improvement guideline is to augment the COP as well as the cooling limit of a coaxial pulse tube cryocoolers given the necessities of the cold finger measurements. A streamlined PC reenactment model and quick plan strategy ought to be built up for execution forecast and optimization. The model will depend on a limited distinction technique to explain the mass, vitality, and energy protection conditions and some experimental coefficients included with the multi-dimensional impacts in the pulse tube considered. In the model, the geometrical and working measures are advanced at the same time to procure the largest COP as well as the cooling limit.

The reenactment depends on a split dual pressurized cylindrical compressor with the extreme cleared volume of 8.2 cc, which is associated with the cold finger by a 30cm adaptable tube. Considering the working temperature and the limit, 400-work stainless steel screens are utilized as the regenerator network. The normal filling weights change from 3.0 Mpa to 3.5 Mpa in pressure. The reenactments depend on the warm and cool temperature of 300 K and 80 K, separately.

For a coaxial pulse tube cryocoolers, where the pulse tube is embedded concentrically with the regenerator, the external breadth of the cold finger is regularly settled by the end application. For this application, the characterized prerequisites on the frosty finger measurement are around 25 mm. Thus, the rest of the qualities that can be chosen amid streamlining incorporate  pulse tube length, regenerator length and distance across.

Figure 1 demonstrates the reproduction comes about for the cooling limit at 80 Kelvin with regenerator distance. The compressor cylinder eventfulness is around 3.85 mm to give the relating required PV work, and the mean filling weight is set at 3.2 Mpa. Strangely, as appeared in Figure 1, the COP and cooling power change in various routes as the regenerator length fluctuates. We will probably locate the ideal point for both, or if nothing else an adequate point for both. While offering thought to both prerequisites, we chose 66 mm as the best trade-off length.

 

 

 

 

Given a similar guideline, Figures 2 and 3 give the reproduction aftereffects of the variety of the capacity and COP of the pulse tube length and internal distance across. The suitable length and inward breadth measurements are then decided.

 

Applications

According to Dang et al (49, 2016), there are various instances where the rationale behind the functioning of the pulse tube cryocooler has been applied in various similar devices. To begin with is the Multispectral Thermal Imager (MTI) instrument which had been but a figment of imagination till it was fully launched on March 2000 and utilized as another version of the TRW to help in the general cooling of its FPA to about 75K.The MTI (P97-3) is a US DOE-financed satellite mission and a technology demonstration belonging to DOE/NNSA (National Nuclear Security Administration) which has the aim of developing a wide array of new technologies. In addition, the MTI seeks to demonstrate the efficiency of the highly precise multispectral imaging for the related environmental effects as well as other industrial facilities that springs from the space. Managed by SNL (Sandia National Laboratories), RTC (Savannah River Technology Center) as well as LANL (Los Alamos National Laboratory).

Fig 6: Multispectral Thermal Imager (MTI) instrument

Secondly is the Jet Propulsion Laboratory (JPL)’s Atmospheric Infrared Sounder (AIRS) instrument which remained abstract until it was launched on May, 2002.Designed by the Jet Prolusion Technology in California, the Atmospheric Infrared Sounder (AIRS) has proven to be an important tool for the study of the vagaries of climate as well as the climatic patterns associated with a particular locality. The instrument has also been associated with the studies of the distribution such greenhouse gases as carbon dioxide. It has also been reported to be an integral part of weather forecasts. In the wake of its launch, it proved to be even more efficient than the other instruments (five in number) alongside which it was launched (Wen et al, 400, 2015).

Fig 7: Atmospheric Infrared Sounder (AIRS)

This instrument was designed to amass the climatic data and transform it into what was termed as the 3-D maps of the temperature, air, cloud properties and/or moisture. This was a substantial boon for the attempts of many researchers to comprehend the severe patterns of weather as well as the unforeseen climatic changes. Making observations using 2378m wavelengths of the radiation of heat (and makes use of 55k PTCs in the cooling of the HgCd FPA to 58K), the instrument has had a foot print in the aerospace applications (Wen et al, 404, 2015).

Third is the Tropospheric Emission Spectrometer (TES) (another product from the Jet Propulsion Laboratory) instrument which was formally commissioned on 23th July, 2004.The instrument was reported to have been using 57K PTCs to making a cooling effect on two distinct FPAs to 62K.The Tropospheric Emission Spectrometer is essentially an infrared remote sensor that was designed to make measurements on the composition as well as the state of the troposphere. While it has the capacity to detect many aspects of the troposphere, its cardinal purpose is to examine the ozone. It provides data on where the ozone originated from as well as its interaction with other chemical substances in the entire atmosphere. The so collected data is utilized to create a three-dimensional simulation that reflects the chemical composition of the atmosphere, its inherent interaction with the biosphere as well as the exchange processes that occur between the troposphere and the stratosphere (Hu et al, 8, 2014).

Fourth is the Japanese Advanced Meteorological Imager (JAMI) instrument which was not known until its commissioning on 21st March, 2005.The instrument has been reported to be using only two TRW HEC PTCs to have a cooling effect onto its FPAs to 67K.Designed by Raytheon and launched as the Imager Subsystem for Japan’s MTSAT-1R satellite, the instrument ultimate purpose is to deliver precise introduction of the geosynchronous earth orbit (GEO) technologies for the metrological remote senses (Dang et al, 50, 2016).

Fig 8: Third is the Tropospheric Emission Spectrometer (TES)

 

Fifth, the pulse tube cryocoolers are used is such industrial applications as the semi-conductor fabrication. Essentially, semi-conductor fabrication is the process by which the integrated circuits that are the prototype of the everyday electrical devices, is created. It could also be defined as the multi-stage sequencing of the phot chemical and lithographic steps during which the electrical devices are created. In the military scene, the pulse tubes are used in the process of cooling the military remote sensors that are used for the general remote sensing of their battle field and/or looming wars. They are also used in the cooling of the astronomical detectors where the liquefied cryogens are mainly used. Some of these cryogens includes the Atacama Cosmology Telescope and/or Qubic experiment. The pulse tubes are preferred in these aerospace applications for the simple reason that the aerospace environment is special; whereby the supply of power is limited. In addition, the rejection condition is entirely negative. Similarly, the pulse tubes may be quite useful specifically in the telescopes that are based on the space applications only where it may be farfetched to replenish the supply of the cryogens when they get depleted. Next, the pulse tubes have also shown a capacity to liquefy the oxygen gas on planet Mars. Lastly in this case is the fact that pulse tubes have been reported to be effective pre-coolers in the dilution refrigerators (Hu et al, 9, 2014).

Safety procedures:

Based on the work by Chen et al (57, 2013), the optimization process may have some inherent perils that may compound the entire process of designing and optimizing a pulse tube cryocooler. As such, the designing process ought to be meticulous and procedural. In this regard, there should be a perfect transfer of heat between the generator fillings and the gas that ran the pulse tube. In addition, the hydraulic diameter of the generator fillings ought to be less than the depth thermodynamic penetration. Third, the generator should not be as long as it would be sensible in as far as the optimization of the pulse tube cryocooler is concerned. Fourth, to bypass any possibility of temperature being inhomogeneous in the generator, the pulse tube ought to be lengthened. Furthermore, when the cooling ability of the cooler is increased, the diameter decreases in length/ in the ratio of the regenerator. In addition, owing to the high temperatures on the axis, there is inhomogeneous distribution of temperature. To resolve this, one may add a low-mesh stainless steel or copper to enhance improvement on the straightening or conductivity of the flow at either ends of the regenerator. The reservoir of the gas as well as the inertance tube are required. The two have the capacity to adjust the step-wise relationship that exists between the filling of pressure and the motion of the gas. Additionally, in order to achieve a profound shifting of phases, the should be installed a double segmented inertance tube which have inhomogeneous measure measurement. The inertance tube have the capacity to negate any possibility of there being an instability that may occur. The occurrence of the possible instability has in many cases been attributed to the existence of the DC impact which may eventuate into double inlets in the cooler. To ensure that there will be no any possible occurrence of a gas leakage, it should be ensured that there is an increased performance in as far insulation is concerned. Lastly, in order to improve the refrigeration properties of the cooler, the multi-bypass, the inertance tube as well as the double inlet should be integrated as the phase shifters (Pan et al, 23, 2016).

PTC Performance and diagrams:

The rich PCT information system Thales Cryogenics  was taken advantage of to create a new and bigger compressor. The purpose with respect to the performance of the pulse tube cryocooler was to enhance the delivery of 300W (the PdV power), with an average compressing efficacy of about 75%. These deliveries are expected to produce a maximum input power of 400W (Chen et al, 55, 2013).

The designing process commenced with the examination of the concepts of the linear motors. Based on the fact that maximum efficiency is needed and such limitations as swept volume, dimensions, the weight are real, the research preferred a moving magnet-type linear motor. In this case, since the chosen motor had great magnetic field changes and gradients, it was required that there be a full optimization of the components that are part and parcel of the magnetic circuit. This was done to minimize the possible magnetic losses. Alongside the Joule-losses, the magnetic losses have a bearing on the ultimate efficiency of the cooler (Yang et al, 345, 2010).

Fig 10: The Pulse Tube Cryocooler.

The preliminary tests were carried out on a bigger compressor using the cold finger of the LSF9330, a high-ended flexure which was supported by a 20mm stilring cold finger. This allowed the initial testing of the compressor long before the LPT9710 pulse tube cold finger was availed. As such the only experienced limiting power was the level of the power; the 20mm stirling could only be exposed to the test with a maximum electrical input power of 125W.This is because it is generally designed to be in line with the functionality of a compressor which had a capacity to deliver substantially less power compared to the 9710 compressors (Pan et al, 23, 2016).

Measuring the performance efficiency of the compressor was only possible when the striling cold finger had been duly connected. The efficiency of the compressor was measured using the measurements of the voltage of the current, the stroke of the compressor among other related quantities. When the efficiency of the compressor was integrated into the LSF9330 cold finger, it hit the 80% mark which was well above the design objective of 75%. Owing to the fact that the compressor was created to match with the stirling cold finger. When incorporated to the LPT9710 pulse-tube cryocooler, the efficiency of the cooler is thus anticipated to be relatively high (Wen, 399, 2015).

The thermodynamic performance is as shown below. In the figure, the cooling power has been plotted against the cooling capacity. In other words, the figure brings into light the fact the cooling power of the pulse tube depends on its ability to impact a cooling effect. From the figure, it is straightforward that the effective combination of the Stirling cold finger with the bigger compressor may result to in an entirely effective system (Xun et al, 283, 2013).

Fig 11: Cooling capacity of the PTC with 1.7 MPa filling pressure.

The subsequent figures represent the efficiency metrics of the pulse-tube cryocooler.

Fig 12: Typical cool-down curve of the PTC with 1.7 MPa filling pressure.

Fig 13: Cooling capacity of the PTC with 2.2 Mpa filling pressure

Fig 14: Efficiency of the linear compressor.

 

Project Planning

The figure below represents the general planning of this project; the planning includes the specific activity of the project as well as the date the specific activity will occur.

Gantt Chart:

 

 

Progress to date and upcoming planned work:

Based on the information of the gantt chart above, I am currently writing my tentative report which will be the final task of term1.In addition, I stalled the designing process of the coaxial pulse tube cryocooler since it may not take long and I will embark on it during the vacation. To start with, I commenced working on the actual project late owing to the fact that there was a delay in the allocation of a title for the project. As such, I had to catch up quickly with the literature review section as well as the project planning. I had adequate time to have my final touches on other assignments in time since they had a close relationship to each other. This common relationship may include the comprehension of the pulse tube cryocooler as well as the real applications related with it such the definition of safety. As such, it was easy to make a link between the two. Nevertheless, the work slated form term 2 assignments will be more involving and will therefor require increased rate of work and time since I will start designing the coaxial pulse tube as well as the CFD which is bound to help in optimizing the performance of the device. In addition, the interface conditions ought to access via the sage and the outcome should be analyzed meticulously (Kamoshita, 365, 2011).

Conclusion:

To wrap up, the development of the pulse tub cryocoolers has for the longest time now been so vital in such fields as the aerospace as well as the military. This is because it is very important in many applications and ranges of temperatures due to its simple physiology, high level of reliability, durability and compactness. In addition, the arrangement of the coaxial pulse tube cryocoolers is the most short-sized and is applicable to a myriad of applications owing to the fact that the compressor and the inertance tube which are coupled together instead of being linked through the connection tubing. This paper has generally focused on the 10-40K range of temperature since it is the hardest one to attain and needs a lot of optimization in order to achieve the lowest temperatures with the best tenable efficacy (Radebaough, 430, 2010).

 

 

 

 

 

 

 

 

 

 

References List

Chen, L., Jin, H., Wang, J., Zhou, Y., Zhu, W. and Zhou, Q. (2013) ‘18.6 K single-stage high frequency multi-bypass coaxial pulse tube cryocooler’, Cryogenics, 54, pp. 54–58. doi: 10.1016/j.cryogenics.2012.11.002.

Dang, H. (2012) ‘High-capacity 60 K single-stage coaxial pulse tube cryocoolers’, Cryogenics, 52(s 4–6), pp. 205–211. doi: 10.1016/j.cryogenics.2012.01.006.

Dang, H. and Zhao, Y. (2016) ‘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’, Cryogenics, 78, pp. 40–50. doi: 10.1016/j.cryogenics.2016.06.001.

Hu, J.Y., Zhang, L.M., Zhu, J., Chen, S., Luo, E.C., Dai, W. and Li, H.B. (2014) ‘A high-efficiency coaxial pulse tube cryocooler with 500 W cooling capacity at 80 K’, Cryogenics, 62, pp. 7–10. doi: 10.1016/j.cryogenics.2014.03.010.

Kamoshita, T. and Yasukawa, Y., Fuji Electric Co., Ltd., 2004. Pulse tube cryocooler. U.S. Patent 6,691,520.pp.415-434.

Pan, C., Zhang, T., Zhou, Y. and Wang, J. (2016) ‘A novel coupled VM-PT cryocooler operating at liquid helium temperature’, Cryogenics, 77, pp. 20–24. doi: 10.1016/j.cryogenics.2016.04.009.

Radebaugh, R., 2003. Pulse tube cryocoolers. Low Temperature and Cryogenic Refrigeration,

Wen, J., Wu, Y., Zhang, A., Yang, B., Zhang, H., Chen, X. and Chen, H. (2015) ‘Experimental study of an aerospace low temperature refrigerator cooled by a pulse-tube Cryocooler ☆’, Physics Procedia, 67, pp. 398–404. doi: 10.1016/j.phpro.2015.06.048.

Xu, M., Sumitomo Heavy Industries, Ltd., 2007. Pulse tube cryocooler. U.S. Patent Application 11/905,432.

Xun, Y.Q., Dai, Q.T., Yang, L.W. and Liang, J.T. (2013) ‘High frequency pulse tube cryocooler with nonmetallic cold head’, International Journal of Refrigeration, 36(1), pp. 279–284. doi: 10.1016/j.ijrefrig.2012.08.012.

Yang, L.W., Xun, Y.Q., Thummes, G. and Liang, J.T. (2010) ‘Single-stage high frequency coaxial pulse tube cryocooler with base temperature below 30 K’, Cryogenics, 50(5), pp. 342–346. doi: 10.1016/j.cryogenics.2010.01.009.