- COB LED Heat Sink
- SMD LED Heat Sink
- Lighting Housing
- Grow Light
- Commercial LCD Display
review of modern spacecraft thermal control technologies.
Since 1957, the spacecraft (S/C)
By providing communications, scientific observations, meteorological monitoring, navigation, remote sensing, monitoring and data, technologies that utilize this new Highland have been developedrelayservices (Gilmore 2002).
However, the space mission is facing great challenges in engineering.
S/C thermal control is critical.
S/C Thermal Control Subsystem (TCS)
Maintain an unallowed temperature limit for the entire life cycle of the component.
The difficulty in achieving this depends on the task requirements, as they determine the range of thermal environments and component operations that S/C will be exposed.
What makes this problem more complicated is that S/C is faced with including amicro-
Gravity environment, atmospheric resistance, atomic oxygen that degenerates the surface of the spacecraft, a vacuum environment that leads to gas release and cold welding, micrometeoroids and charged particles.
Overcoming these challenges is the result of well-designed systems and the use of modern technology.
In many cases, S/CTCS use the same technology as ground HVAC & R (e. g.
Insulation and twophase systems).
However, due to the unique spatial environment, these technologies usually have different features than ground technologies.
In other cases, S/CTCS take advantage of common techniques in land systems (e. g.
, Loop heat pipe).
In general, S/c tcs technology has been researched and developed remotely from the HVAC & R community.
Thus, many benefits can be gained by bridging the gap between S/CTCS and HVAC & R professionals.
Several examples of commercial technologies originally developed for space applications show that these collaborations are beneficial.
As necessary, S/C at the end of 1950 drove the progress of solar cells that were ultimately used for ground applications.
The US Department of Defense has developed a global positioning system (GPS)
This permeates our society today.
Created in 1958, NASAoversaw is responsible for the development of many technologies that are now widely commercialized, including non-
Air-invasive sexual health diagnosis
Engineering health-transportation management, precision agriculture and irrigation tools
Management software, less-
Expensive methods for the manufacture of carbon nanotubes (
Comstock and lockny 2007).
Given the long term success History of derivatives, there may be opportunities for the transfer of modern S/c tcs technology to ground HVAC & R applications.
These opportunities are discussed in this paper.
First, an overview of s/C thermal control is introduced.
Next, the strong S/c tcs will drive many technological advances and therefore deserve attention.
Finally, this paper reviews modern S/c tcs technology and evaluates its potential in land applications.
S/C thermal control S/C consists of two parts: the payload that provides the intended service and the bus that supports this payload.
The S/C bus consists of several subsystems that ensure that the payload is fully operational throughout the task lifecycle.
Among them, the thermal control subsystem (TCS)
Designed to keep the part temperature within a specific threshold.
TCS achieves this by first fully balancing the energy input and generation ,[E. sub. ln]and [E. sub. gen]
With energy storage and heat dissipation functions ,【E. sub. stored]and [E. sub. out]
, As shown in equation 1. [E. sub. in]+ [E. sub. gen]= [E. sub. stored]+ [E. sub. out](1)
Energy Input [E. sub. in]
Space derived from direct solar flux maintains a thermal environment ([q\". sub. sol]), albedo flux([q\". sub. alb])
And outgoing long wave radiation ([q\". sub. OLR]).
Other energy inputs include deep space radiation, free molecular heating, and charged particle heating, but are insignificant for most analyses (Gilmore 2002).
The total rate of these flux inputs (
Energy input rate per unit area)
Summarize in equation 2. [q\". sub. total]= [q\". sub. sol]+ [q\". sub. alb]+[q\". sub. OLR](2)
For the Earth on any surface, this relationship can be approximate to include the solar absorption capacity ([alpha])
Solar radiation (S\")
Radius of the Earth ([R. sub. TOA])
The height of the spacecraft (h),albedo ([[rho]. sub. alb])
The top corner of the Sun ([theta])
Long Bobby ([epsilon])
And the radiation emitted by the Earth (E\"). [q\". sub. total][
About equal to][alpha]* S\" +[alpha]* [([[R. sub. TOA]/[[R. sub. TOA]+ h]]). sup. 2]* [[rho]. sub. alb]*S\"\' * cos([theta])+ [epsilon]* [([[R. sub. TOA/[[R. sub. TOA]+h]]). sup. 2]* E\"\' (3)
This association illustrates the complexity of the thermal environment in space and highlights the difficulty of thermal control.
What makes it difficult to zoom in is time and position.
Basic changes for each variable.
The range of solar radiation values is 1317 W/[explain the change of solar cycle]m. sup. 2]up to1419 W/[m. sup. 2]
Depending on where the Earth is relative to the sun.
In addition, the reflectivity ([[rho]. sub. alb])
Defined as part of the solar energy reflected or scattered back into space by the Earth, varies greatly depending on the composition and nature of the Earth (Anderson et al. 2001).
Finally, the output longwave radiation load is not as important as the direct solar flux type, but because the source temperature is very close to the source temperature of the spacecraft, this brings a unique problem.
Therefore, by selecting surface materials with appropriate optical properties, they cannot be easily reflected off, as these same types of surfaces do not allow the emission of heat from the spacecraft.
Energy Power GenerationE. sub. gen]
Is the result of the energy consumption of the components required to operate the satellite.
In 2000, Hoeber and Kim found that this power doubled every five to six years due to increased demand for satellite services.
While recent trends suggest that total power has reached a stable level, the increased heat flux has not reached that level.
According to batujin (2005)
The future problem with small satellites is the micromation of space equipment, resulting in reduced component size and increased heat flux, up to 100 W /[cm. sup. 2].
Large satellites also have similar problems in high-throughput space applications such as power converters, scientific lasers, microwave solids, etc.
Broadband light source, directional energy weapon and space for national transmitter, microcomputer system-based radar (Golliher 2002;
Ponnappan, etc. 2002).
Active and passive-based thermal management technologies cannot meet these requirements, so it is necessary to develop new technologies in order to be able to operate reliably under adverse conditions (Maxwell et al. 2008).
Energy storage]E. sub. stored]
Is a function of satellite mass and thermal properties and significantly affects the time change in component temperature when exposed to time on satellite orbit
Changes in boundary conditions.
S/C has a low capacitance with a significant peak temperature on one track, while S/C with a high capacitance has a smoother temperature distribution.
While high capacitance is required, this price is usually paid by increasing the quality of eds/C, which is not good due to relatively high launch costs.
Foster and Smith (2004)
Provide a detailed review of the launch vehicle efforts including SpaceX and Falcon 1.
This \"affordable\" unit was able to launch about 450 to LEO for $7. 9 million (i. e. , $16,667/kg)(SpaceX 2008).
The heat dissipation of satellites ,[E. sub. out]
, Traditionally only through the radiation of the S/C boundary. As a result,[E. sub. out]
Limited by the available surface area and the optical properties of the surface, and affected by the interaction with the space thermal environment.
According to Hoeber and Kim (2000), managing [E. sub. out]
It is one of the most challenging design limitations of TCS.
S/C has become very complex and expensive to meet the growing importance and expectations of space while overcoming its inherent challenges.
For example, the deployment time of satellites ranges from 3 to 7 years, and the cost ranges from millions to billions of dollars (
Williams and Palo Alto 2006.
With robust system design, the complexity and cost of S/C can be reduced.
While the traditional approach focuses on the design optimized for specific tasks, strong S/C has been developed to handle overseas-wide tasks, thus reducing the long term
Cost of design and development.
In addition, the powerful S/C allows for a significant reduction in time, easier insertion of technology, and helps resist late changes in mission requirements (
Bill and O\'Donnell 2001).
Achieving this requires a big difference from traditional design methods, especially TCS.
The powerful S/c tcs must meet the larger design space of the thermal environment, component distribution, and running state.
Therefore, the traditional design method of S/c tcs must be completely changed.
This will be achieved by promoting technological advances in improving installation methods, heat balance regulation, and strong heat load sharing (Young et al. 2008; Bugby etal. 2005a; Bugby et al. 2008).
The powerful S/c tcs will be implemented through a lot of improvements to existing technologies and the development of new concepts.
As a result, strong S/c tcs technology is being advanced through a lot of research work and exciting developments.
Modern S/C thermal control technology review the following is a review of modern S/c tcs technology, including traditional and robust S/C design techniques.
Detailed study on insulation and heat change
Heat dissipation switch, high rejection surface
Pumping conductive material
Fluid circuits, heat pipes and heat-
Including pumping technology.
For each, an assessment of itspot for ground applications is provided.
Insulation is a good insulating material for saving heat energy and protecting the satellite from external radiation
Establishment and promotion of S/c tcs technology.
Multi-layer insulation (MLI)
The most common S/C insulation technology provides an effective method for spacecraft insulation.
MLI consists of up to 25 layers of thermal control material to obtain the required optical and insulating properties (
Donabedian and others. 2002).
By using a reflective metal layer, radiation heat transfer is minimized, which limits the absorption and emission of solar radiation
Resistance to infrared radiation, while low-
The internetwork Packer.
Ventilation paths embedded within MLI allow exhaust and minimize convection heat transfer.
As shown in Figure 1, a medium-size MLI blanket usually reaches a valid launch in the range of 0. 015 to 0. 030.
Combined with awell-
MLI blankets have a flight history and are effective and reliable.
However, MLI requires a tedious design and installation process due to its inherent vulnerability and the alternative forms being sought. [
Figure 1 slightly]
According to Lee and others, the gel is insulated. (2009)
For the first time, the gas gel material formedin 1930 s changes the air of the silica gel in the liquid phase.
The pore structure of the gel is maintained by drying under supercritical conditions, in which the interface tension between the liquid phase and the gas phase is significantly reduced, almost eliminating the common cause of shrinkage and
Therefore, the air gel is one of the lightest solids known, while showing excellent thermal insulation and sound insulation in the air and in the real air (Sibille et al. 1996).
Due to these unique properties, they are studied as a placement technique for MLI in the form of beads and blankets.
Gas gel beads have been developed for low temperature applications with a bulk density of about 0. 080 g/[cm. sup. 3](4. 994lb/[ft. sup. 3]).
The stacking density of beads treated with carbon black r300 opaci is slightly higher, which is 0. 094 g/[cm. sup. 3](5. 868lb/[ft. sup. 3])(Fesmire et al. 2002).
The diameter of the free flow can be poured into a small cavity to produce minimal dust.
Pearl Rock is another bulk
Filling materials for low temperature applications, but encountered problems in mechanical compression and settling. Fesmire et al. (2006)
It was found that the gas gel beads settled better than the Pearl rock and glass bubbles.
In terms of thermal performance, Barrios et al. (2008)
It was found that in the application of low temperature, the gas gel bead is better than the glass bubble.
However, it was noted that the smaller diameter of glass bubbles with a diameter of less than 10 microns resulted in a residual pressure of about 30 ml compared to the 100 ml pressure in the gas gel Bead test.
The results show that the pressure has a great influence on the bulk insulation performance, and while the air gel beads can be superior to MLI at higher pressure, the MLI blanket provides the best insulation in vacuum (Fesmire et al. 2002;
He\'s Charleston, etc. , 2008).
The gas gel bead is a technique worthy of further study, especially in opaque form, which helps to reduce radiation heat leakage. Trifu et al. (2004)
Evaluation of the gas gel composite blanket as a potential alternative to MLI.
The air-gel composite blanket has similar thermal insulation properties with MLI. An ultra-lightweight (i. e. , 0. 03g/[cm. sup. 3][1. 872 lb/[ft. sup. 3]])
The thermal conductivity of the air gel blanket reached 0. 74 mW/m-K (0. 43 mBtu/h-ft [degrees]F)at 160[degrees]C(320[degrees]F)
At a medium vacuum level.
In addition, blankets elblankets can handle compression up to 200 psi before thermal performance is significantly affected.
Combined with its capability of manual bending and handling, the installation cost of aerogelblankets may be significantly lower than MLI.
In addition, the air gel blanket has good air release properties.
The flight history of the gas gel is limited compared to MLI, although the recent mission put the technology in space.
Most notably, carbon is used by the rover
On a cold Martian night, isolate the most sensitive electronic components with opaque silica gas gel.
Carbon is added to minimize the infrared transmission in the box, and the density of the air gel is 0. 02 g/[cm. sup. 3](1. 249 Ib/[ft. sup. 3])
And the conductivity is 0. 012 W/m-K in 10 torr [CO. sub. 2]at 0[degrees]C (32[degrees]F).
Similarly, travellers use silica gel with a density of 0. 02 g/[cm. sup. 3]
The effective conductivity is 0. 0163 W/m-K at 10torr [CO. sub. 2]and 24[degrees]C (75. 2[degrees]F)
Protection of electronic equipment (
Donabedian and others. 2002).
Due to its inherent design, MLI performs best in vacuum but not well in atmosphere.
Therefore, it is not a suitable candidate for most ground applications.
However, the gas gel does not require a high vacuum environment, so there is great potential in enhancing the product.
In fact, a wide range of studies are currently under way in the gas gel
Various applications including electrical insulation and reinforced glass window systems.
Due to its extremely low thermal conductivity, the air gel allows the use of thinner refrigerator and oven walls, thereby increasing the available volume and/or reducing the unit size.
Comparison of various types of applications in thermal insulation
Water tanks, Omer and others. (2007)
It is found that the air gel is the best insulating material in terms of thickness, weight and quality reduction;
Gas gels, however, are much more expensive than other types.
The air gel is also considered the \"Holy Grail\" inglazings, despite the largest window productiondate is 1 [m. sup. 2](10. 8 [ft. sup. 2])(Bahaj et al. 2008).
In the study of Schulz and others. (2005)
Schulz and Jensen (2008)
, Compared to three times the same size, the evacuated air gel glass provides a 19% reduction in energylayered, argon-filled glazing.
While it currently does not meet the visual quality of the traditional glass window system, it is good in many cases.
In the case of a skylight or light, it will certainly meet the visual requirements
Based on performance only, the gas gel technology is obviously very suitable for a wide range of applications
Ground application range.
However, its costs will slow down market penetration.
So take advantage of the theS/C community-
Where cost considerations are less stringent-
Provide the necessary development to overcome these obstacles. Variable Heat-
Rejection surface change of heat-
The suppression capability of the S/C surface is a way to provide heat balance modulation.
This can be done by changing the physical structure of the radiation surface to change the angle factor and adjusting the heat conduction path near the surface (i. e. , heat switch)
Or by changing the optical properties of the radiation surface.
Several ways to achieve surface heat balance modulation are outlined below. Macro-Louvers. Macro-
Blinds design uses blades to control the viewing angle between the environment and the low viewing angle
An electronic substrate mounted on the surface of the spacecraft.
The blade is made of polished metal, so when the blade is closed to cover the substrate, the effective ratio of the assembly is lower than the radiation rate.
Blade blinds act in a similar way to Venetian blinds, but are easy to catch sunlight between blades.
The windmill design has the advantage of low profile, less than 1. 28 cm (0. 5 in. )
High, so do not capture solar energy (Hardt et al. 2002).
This type of blinds has rotating blades that expose materials with low radiation rates (e. g.
When insulation and high radiation rate materials are required (e. g.
When radiation is needed
However, this design allows the radiator to account for only 50% of the surface area when the blinds are opened.
Therefore, the change of radiation rate is limited. Micro-Electro-Mechanical (MEMS)Louvers.
And the traditional dimension ~ O (cm)
The shutter size of the microcomputer electrical system is O ([micro]m)(Farrar et al. 2007).
The micro-electro-mechanical system blinds offer the same advantage of many macros
Blinds, such as the ability to achieve a continuous launch range;
Further benefits, however, include higher precise control of radiation rates, greater flexibility for spatial changes in radiation rates, and higher redundancy in structures.
For example, Farrar et al. built and tested each electronic control unit on the prototype processor. (2007)
Control the area of only about 3 cm x 4. 5 cm.
In such a small micro
Louveractuators can cover a large part of the device area.
Microcomputer System on NASA space technology 5ST-5)
The task uses an electrostatic comb drive to limit the maximum radiator surface exposure to 40% of the total surface area (Farrar et al. 2007; Osiander et al. 2004).
The importance of minimizing actuator spacing through the ST-5 mission.
In the laboratory environment, the specific radiation rate increased from 0. 18 to 0. 30 (Darrin et al. 2000)and 0. 50 to 0. 88 (Douglas et al. 2002)were found.
However, the micro-sheet theST-
5 tasks are only 0.
03, the change of the temperature of the radiator corresponding to 1 k (Farrar et al. , 2007).
Although the researchers believe that the ratio of the area of the blinds to the supporting structure can be doubled and doubled than the range of the radiation rate value, the technology still needs significant development to match the macro-louvers (Darrin et al. 2000).
Another important consideration for blinds design is reliability.
A problem that hinders reliability is the potential viscosity, electrostatic interaction, capillary force and local cold welding in the microcomputer electrical system equipment (Patton 1999).
The reliability of the memory can be improved by carefully designing the device coating, correct grounding and Degas technology.
Electrostatic switch radiator (ESR). Whereas macro-
MEMSlouvers operates by changing the angle of view coefficient between the surface and the environment of the high emission connector, and ESRs operates by introducing and removing additional conductive thermal resistance near the surface.
Fundamentally, ESRs work like a thermal switch, but are used to change the surface heat dissipation.
They are composed of composite films with high radiation rate and low visible absorption ratio and low-
Radiation rate surface adhering to S/C
In response to the applied DC voltage, the conductive film coating has physical contact with the S/C surface, resulting in a high effective radiation rate.
When the voltage is removed, the cover film is removed from contact with the skin.
Due to the low radiation rate of the skin and the insulation effect of the vacuum in the gap, the temperature of the cover film decreases, thus making the effective radiation rate of the surface low.
The electrostatic blinds use printed circuit boards made of gold metal and are connected to the S/C surface through an electrically insulated adhesive.
Cover film is a pi film sprayed on the outside with aluminum and coated with a high radiation rate conductive coatingfacing surface.
With this structure, it is theoretically possible to achieve effective emission in the range of 0. 05 to 0. 95(Biter et al. 2002, 2003)
The effective radiation ratio changes 0.
72 has been implemented in laboratory testing (Biter et al. 2004).
The first generation of equipment is also at NASA\'s ST-5 mission;
Measure an electrostatic radiator with an effective specific radiation rate change of 0.
43 in the ground test, the effective specific radiation rate changed to 0.
37 in the Space Test, slightly lower than the task (
Biterand Oh 2007).
In addition to lower than expected effective emission changes, another significant disadvantage of the device is that the operating voltage is 350 V, much higher than the voltage commonly used on satellites (Biter et al. 2004;
Biters and Oh 2007). A second-
The power generation device uses inorganic insulators such as alumina on the substrate.
By moving the electrical insulator from the covering film to the housing, the flexibility of the covering film is improved with an effective emission voltage of 0, and the operating voltage is reduced to between 150 and 200 V. 6 (Biter et al. 2006). Currano et al. (2008)
0 reached an agreement.
52 effective emission change at 280 V
One way to reduce the operating voltage of electrostatic devices is to reduce the device. Beasley et al. (2004)
A 250-level thermal switch array has been developedmicro]m by 250 [micro]
Mthat can work at a voltage below 28 V.
In addition to the lower operating voltage, the microcomputer system is light in weight, providing greater flexibility for the spatial variation of the effective radiation rate.
However, a lot of testing is still needed for these devices to determine the best deal
Between mechanical and thermal properties, both depend on the design of the support structure.
Color changing device (ECD). Whereas macro-and micro-
Both blinds and electrostatic devices involve mechanical processes, and the ECDs rely on chemical processes to change the radiation rate of the surface.
There is no obvious advantage of moving parts for reliability, and the ECDs are still able to achieve a continuous range of emission.
As shown in Figure 2, the device consists of five main layers, starting with the reflection electrode (RE)
There\'s a mirror
Like an infrared reflection, it is mounted on the skin of the spacecraft.
The active element installed on the RE is discolored by electricity (EC)Ion conductor (IC)
And ion storage (IS)layers.
The IC layer conducts ions, but provides electrical insulation between the electrodes of the device.
The Ec and IS layers are metal oxides with chemical activity, which can be inserted with electrons and ions and de-inserted layers.
Finally, transparent electrodes with high conductivity and transmission ratio protect the device from atomic oxygen. [
In [range], early childhood development operates by applying a small voltage+ or-]
2 v, move the ion and electron pairs between the EC and IS layers.
When applying voltage, one of the active metal oxide layers experiences an increase in absorption capacity due to the insertion layer, while the other active metal oxide layer experiences an increase in absorption capacity due to ion extraction at the same time.
When this process is reversed, the launch of the activation layer will decrease.
Because maximizing exposure of the active layer to the environment will provide maximum specific radiation rate changes, it is necessary to have a transparent electrode on the outer surface of the child\'s development.
While some ECDs rely on a grid of opaque electrode materials to minimize the area covered by the electrode, demiliont et al. (2006, 2008)
And Shannon (2007)
A transparent electrode was tested in theirECD.
Among them, early childhood education is not only 5g /[m. sup. 2](0. 001lb/[ft. sup. 2])
The average emission degree modulation 0 is realized.
Three of the AMidStar space experiments, 0.
Laboratory Experiment 7.
It should be noted that this is a different ECDs for two generations.
At the selected two wavelengths, the emission modulation is close to 0. 9.
Chandra Sehar and others. (2003)evaluated a 1. 6 kg/[m. sup. 2]
The emission modulation is 0. 4to 0. 5.
Table 1 provides a summary of different variables-
Reject the surface.
Ground Application. Variable heat-
Rejection surface technology similar to S/c tcs has potential in ground applications.
In particular, chrome plating can be integrated into the windows of the building.
Based on the same basic principles as the S/c tcs method (i. e. ion conduction)
, Terrestrialapplication focuses on transmission ratio modulation in visible spectra of indoor lighting and space
Lee and Di Bartolomei (2002)
Investigate the big-
Color changing windows for commercial building applications, found that they reduce the use of lighting energy in some cases, but are not able to meet energy needs at the same time
Efficiency and visual comfort goals, especially in winter, when low direct
The sun conditions exist.
They found that increasing the speed of the switch can expand the use of chrome plating.
With the increase in the area of glass windows, the increase in bicycles and the decrease in temperature, the switching speed has proved to be slow. In a follow-
Research Report of Li and others(2006)
Two challenges faced by chrome plating technology were found: 1)
Integration of dynamic windows with building systems, 2)
Development of control algorithms, diagnostic tools, and performance data. For south-facing large-
Display 44-area window, chrome plated59% and 8-
On the visible transmission window of 23% and 15%, the lighting energy saving is 50% per day.
They also found a color changing window.
The lighting system controller maintains the operating plane illumination level in the [range]+ or -]
Requirements of 10%.
Electric discoloration technology can also be used in combination with light
Guide the equipment to penetrate the sunlight into the building. Clear et al. (2006)tested 0. 9 x 0.
9 m electric discoloration window with approximately 3-visible transmission range60%.
They found that increasing the range would help reduce glare and increase daytime lighting at low brightness
In addition, subjects preferred variable transmission conditions, but the system was slightly more than electrical lighting used for fixed transmission types.
It was pointed out that this could be the result of an inefficient control algorithm. Bahaj et al. (2008)
Note that the current 5 to 10 minute switching time, glare, color rendering, cost and longevity issues must be addressed to achieve significant market penetration.
Granqvisa, etc. (2007)
Focus on space conditioning.
The simulation results show that the intelligent window can reduce the space.
Cooling energy up to 50%.
The widespread use of these devices will require cheap production capabilities such as web coatings that allow rollingto-
Other obstacles include durability, optical switching speed, and size limits.
Although the Chromecast technology is being studied, no Chromecast work integrated within the walls of the building is shown in the literature.
This method can provide a way to improve the cooling and heating performance of the building.
It is expected that cost considerations will be the most important obstacle in this approach. Variable heat-
Reject the surface, that is, chrome plating, has great prospects in the application of the building.
However, the literature suggests that challenges remain, many of which are shared with the S/CTCS community.
It includes reduced switching speed, optimized control algorithm, control range and diagnosis.
These communities can therefore benefit from cooperation.
The heat switches are able to be adjusted according to changes in the heat dissipation rate, which makes them an attractive option for modern satellites.
If the thermal switch connects the electronic part to the radiator, when the device generates a lot of energy, the heat is discharged from the device, and when the device does not generate heat, the heat is saved, allows the equipment to remain within the desired temperature range.
The configuration shown in figure 3 uses a thermal switch to connect each internal component to the satellite structure.
Summary of thermal switch technology see table 2.
Therefore, the temperature of each internal device can be controlled separately by selecting the appropriate thermal switch operating temperature.
However, this design has never been used and may not be adopted unless it proves the success of the thermal switch in smaller applications.
The variable conductivity operation of the thermal switch can be achieved in many ways. [
Figure 3 slightly]Paraffin.
The volume change of paraffin wax expands by about 15% when it melts, which helps the thermal switch to operate.
Under normal working conditions, the paraffin thermal switch contains a mixture of solid and liquid wax.
In addition, there is a gap between the two devices connected through the paraffin thermal switch.
Due to the vacuum in the gap, the heat transfer between the thermal switches is limited to the radiation through the gap and the conduction through the supporting structure.
When the heatis is added to the thermal switch, it is absorbed into the waste heat and melts the paraffin solid.
The melted paraffin expands and closes the gap between the cold and hot sides of the previously separated thermal switch, thus realizing the conduction of the entire surface of the thermal switch.
With more heatis added, more paraffin melts, and the pressure at the contact place on the hot and cold sides increases, resulting in an increase in conductivity.
Including the base and Fastener Design, there are a variety of hot switch designs to choose from.
According to Osiander, etc. (2004), a 100-g (0. 22-lb)
The base thermal switch has a conductivity ratio of 100:1.
The paraffin thermal switch has been used to passively control the temperature of the secondary battery on the Mars probe (MER)mission (Sunada et al.
2002, Novak and others. 2003).
This ability as a self
One advantage of the thermal switch is to adjust the variable conductivity device.
Another important advantage of the thermal switch is the over-damping response to the circulating thermal load, which enables the thermal switch to operate in a flat and robust manner.
When heated or heated, the temperature of the equipment does not change with the melting point of the paraffin before all paraffin wax is melted or solidified.
Therefore, the response time of the paraffin thermal switch to the step change of heat flow is about 1 minute (Lankford 2002). Gas-Gap. The gas-
The gap heat switch, mainly a low temperature solution, uses an adsorption bed to control the amount of gas in the gap separating the hot and cold structures.
When heat transfer is required through the switch, heat the adsorption bed of zirconium nickel-hydrogen, active charcoal, or other adsorption materials with a resistance heater to release hydrogen into the gap.
Hydrogen is able to pass through the heat switch until the control heating switch is off and the hydrogen is absorbed again by sorbent material.
This type of thermal switch shows the conductivity ratio in the range of 700: 1 to 2500: 1.
However, the higher conductivity ratio is at the expense of a longer switching time of five minutes to one hour, and the cost and reliability issues are higher due to the smaller tolerances required in manufacturing and higher quality requirements (Lankford2002).
Poor thermal expansion (DTE).
Differential thermal expansion thermal switch provides a more reliable alternative to gas
This type of thermal switch uses two materials with different thermal expansion coefficients (CTEs)
Control the contact between the cold side and the hot side of the switch.
When the center tube of stainless steel is passively or actively heated, it expands enough to separate the Be end plate from the vacuum cylinder, thus limiting the heat transfer to radiation through the vacuum gap.
When the center tube is cooled, it shrinks to make the endplate liumendplate and the cylinder in contact to conduct. Marland et al. (2000)
Two kinds of gas were studied.
Gap and differential thermal expansion thermal switch for Low Temperature Application, building and testing prototype design.
Paulsen and others have also developed and tested differential thermal expansion thermal switches in slightly different versions. (2000)
Milanis and mantelly (2003).
Heat Change layer (VTL).
A recent concept is that VTL consists of a series of hot-
Electric devices (TEDs)
Embedded in another insulation matrix.
In fact, TEDs is used as a double that is personally controllable
Directional heat pump, providing accurate temperature control of the Assembly substrate, with a conductivity ratio of 70: 1 (Hafer et al.
The VTL inserts between the assembly substrate and the satellite bus and is customized according to the size of the Assembly. Electro-Wetting-on-Dielectric (EWOD). A liquid-droplet-
Hot switch can be realized based on common surface EWOD.
The system is based on a thermal guide drop introduced between abottom and the high radiation rate roof and separated by a barrier.
With EWOD drive, the contact point of the drop changes by providing an on and off state. Gong et al. (2008)
An EWOD for s/c tcs was developed and repeatable 2 was shown.
8:1 switches at 70 v, and the theoretical limit under ideal conditions is 1000:1.
The advantages of this method include low power consumption and fast switching ~ O (seconds)(
Mohseni andBaird, 2007).
Although the application of S/CTCS thermal switch technology on the ground seems to be limited, currently research work using similar technology is common in the field of electronic cooling. Paik et al. (2008)
Wet technology, not as a thermal switch, but as two-
Size adaptive cooling platform.
Krishnan and Garimella are in several works (2004a, 2004b)
And Chris Nan and others. (2005)
For Transient thermal management of electronic equipment.
Instead of using paraffin in a thermal switch, they integrate it into a phase change energy storage system. High-
Electrical conductivity materials such as Lam. (2002)
Several S/C applications with high conductivity materials have been identified as ideal.
These applications include heat multiplier, electronic circuit-
Panel radiator, advanced battery assembly and non-structural radiator.
Therefore, many studies focus on the development of materials that not only have high thermal conductivity, but also maintain good mechanical properties such as strength, stiffness and low expansion coefficient at low density. Composites.
Carbon fiber or graphite fibers in various matrix materials are manufactured to provide high thermal conductivity while maintaining good mechanical properties.
For example, the thermal conductivity of K1100 fiber is three times that of copper, and the density is only one-
Quarter of copper (Lam et al. 2002).
However, the binding of these fibers into the matrix material may result in very small compression effective conductivity depending on the properties of the matrix.
In addition to the properties of the matrix material, the manufacturing process used to inject fiber into the matrix will also affect the properties of the composite due to the importance of fiber orientation.
Although some composites have already produced high conductivity in two dimensions, achieving high conductivity in the third dimension is a challenge in such as heat multiplier (Silverman 2005).
Another challenge for composites is their thermal expansion coefficient (CTE)
Compared to the components they are connected to, such as heat pipes.
The difference in CTE requires a flexible binding material;
However, the adhesive material currently suitable for this application has a high thermal resistance, reducing the overall conductivity of the device.
Despite these challenges, there is still great potential for composites as high conductivity materials.
Banisaukas, etc. (2005)
Reported on the development of aluminum by Northrop Grumman-
8000 reinforced composite thermal multiplier with a weight of 20% to 50% lighter than the standard aluminum multiplier and-
Plane conductivity around 500 W/mK.
Annealing pyrolysis graphite (APG).
The use of APG embedded in amatrix materials has also received attention, such as aluminum heat sinks and solar collectors (
Jaworske and hornacek2).
While the mechanical properties of the APG are poor, wrapping the APG in a matrix that provides stiffness and strength makes it a very useful material.
It is also possible to select the packaging material to reduce the density of the composite or to match the coefficient of expansion of the adjacent equipment.
Table 3 summarizes the comparison of common matrix materials provided by mendesano with and without embedded APG (2006).
Although be and magnesium have the best than conductivity of the materials listed in Table 3, natural materials may provide a better match for thermal expansion in some applications.
For example, ceramic electronic packaging, such as silicon and arsenic-aluminum chemical devices, usually have a thermal expansion coefficient between 5 and 8 ppm/K.
For these applications, Kovar, aniron-nickel-
Although the thermal conductivity of the cobalt material is low, it may provide the best performance.
One manufacturer of packaged APG products is k-
Technology company to k-Core[TM]
Typical package APG, k-Core[TM]
The material consists of graphite surrounded by sealant, which results in the material having a high thermal conductivity in both directions. While the k-Core[TM]
The conductivity of the material is about 1700 W/m-k in the x-andy-
Direction, it has the lowest conductivity, only about 10 W/m-K, inthe z-direction.
However, this can be achieved by introducing high
Another interesting improvement of the packaged APG is that it is incorporated into the flexible strap. These k-Core[TM]
Hot foil and straps are designed to provide a lower quality alternative to the aluminum sheet currently used to connect the equipment to the thermal circuit. The k-Core[TM]
The strap can provide conductivity of about 1100 W/m.
K with a thickness of 0. 016 in. [0. 04 cm](0. 002 in.
Aluminum packaging agent).
Chemical vapor deposition (CVD)Diamond Films.
The thermal conductivity is 1100 W/m-
K of the CVD diamond film has been measured, almost three times as much as copper, and the potential for conductivity is up to four times as much as copper.
CVD Diamond is also known as the hardest material with good strength and is a good candidate for thermal diffusion as an electrical insulator (Lam et al. , 2002; Silverman,2005). Future High-
The researchers continued to look for materials with higher conductivity.
Figure 4, reproduced from silverman (2005)
, Provides an intuitive comparison of specific high thermal conductivity
Conductive materials were reviewed in this discussion.
The figure shows that carbon nanotubes generated by arc discharge, laser ablation, or chemical vapor deposition are shown as high
In addition, the theoretical thermal conductivity is 6000 W/m-
The tensile strength of carbon nanoparticles is 9100 x [10. sup. 3]psi (Silverman 2005).
However, carbon nanotubes were discovered only in 1991, and further research is needed before they are implemented on satellites.
Carbon foam also has a high thermal conductivity with a density of only about 0. 5g/[cm. sup. 3]
, And shows the potential to be used in the radiator despite its low stiffness (Silverman 2005). [
Figure 4 slightly]
Ground applications requiring a combination of high thermal conductivity and good mechanical properties (i. e.
, Strength, stiffness and coefficient of low thermal expansion)
, Can be found in the design of cars and military vehicles.
Other applications include electronic cooling such as laptop cooling and tablet cooling. Panel Display (Kubota et al. 2008)
And handheld devices (Xiong et al. 2008).
In addition, the cost optimization of diamond film for electronic cooling is also studied (
Rogacs and Rhine 2007). Cost-
Reduction in diamond films and other high-tech advances
Spycethermal communicators can be used by S/C. Pumped-
Pumping fluid circuit
The fluid circuit has been successfully used for manned missions.
Due to excellent heat
Physical Properties, the internal circulation of the International Space Station and the shuttle uses water, and the external circulation uses Freon 21 and ammonia (
Westheimerand Tuan 2005).
Despite its success in manned flights
Although the work is in progress, including the Bioinspired integrated structure/thermal fluid loop system (Williams et al. 2007; Arritt et al. 2008; Lyall et al. ,2008).
Fluid channels are integrated into an isogrid structure to provide thermal management capabilities similar to biological organism circulation systems.
The flow is controlled by a large amount of paraffin. wax valve.
The pump is a key component in these systems because redundancy is usually provided through multiple fluid circuits, each with multiple fluid circuits, which adds weight and complexity (
Westheimer and map 2005).
In addition, conventional pumps provide a source of vibration for sensitive sensors that may have problems.
Therefore, reliable inert pumping technology must be developed.
Two notable options are currently being developed.
Electric power (EHD).
The EHD pump uses an electric field to induce motion in a dielectric fluid.
In addition to the absence of moving parts, the EHD pump is light in weight, relatively easy to design and manufacture, requires less power than conventional pumps, and produces very little noise or vibration (Didion 2001).
Darabi et al gave a more detailed explanation of the mechanism behind the operation of the EHD pump. (2002)
And the description of the various pump configurations proposed and tested by the researchers.
The EHD pump is still in the development phase and developing the pressure head in the 1000 Pa range usually requires a high voltage. Didion(2001)
The thermal control system driven by EHD is tested (EHD-TCS)usingsingle-
This EHD system uses a conduction pump, dididion (2001)
Think longer term is more appropriate
Term space application ratio EHD pump using ion
Resistance, polarization, or induction technology.
The EHD pump is tested at a voltage of 10 kV, 15 kV and 20 kV, both of which maintain a constant voltage for the entire operation and during operation
The result is 15 kV including flow rate 0.
786g/s under pressure of 545 Pa.
Chastity and Didion (2007)
The use of EHD conduction pumps for both uses was investigated
Phase Loop for high heat flow thermal control. For anR-
134a working quality, they achieve pressure generation and mass flow rates of up to 13,160 Pa and 2.
Under the applied voltage of 15 kV,-20[degrees]C.
They found that the pre-regeneration has a secondary dependence on the applied voltage, while the flow has a linear dependence.
An important consideration for space applications is reliability.
While one of the main advantages of the EHD pump is considered to be the lack of moving parts, there is actually very little work done
Conduction pump tested by dididion (2001)
Running continuously for 120 h without any problems.
Chastity and Didion (2007)
Within 24 hours, keep the pressure within 300 Pa of the daily average. Didion (2001)
Indicates that further testing is required before the system is suitable for space.
Magnetic dynamics (MHD).
Similar to EHD pumps, since there are no moving parts, magnetic pumps are interested in space applications, which minimizes their quality and vibration.
However, the maintenance fluid pump operates using different principles, so it has different advantages and disadvantages and is suitable for different applications.
Most notably, when the EHD pump is lowconductivity ([10. sup. -12]to[10. sup. -6]S/m)
The electrical conduction rate of a fluid depends on the electrical conduction rate of the fluid (
Above 1 S/m [0. 3 S/ft])to operate(Wang et al. 2004).
In a hemodialysis pump, two electrodes are used to apply voltage on the cross line
Part of the fluid channel, which produces ion current on the channel.
The magnetic field is also applied at right angles to the fluid channel, which interacts with the ion current to produce the aLorentz force applied in the direction of the fluid flow (Woias2005).
In addition to the need for moving parts, this pumping method also has the advantages of reversible;
The flow direction can be reversed by switching the applied voltage or magnetic field direction.
However, the magnetic field required for the maintenance pump may be the main obstacle installed in systems such as satellites, where the magnetic field may compromise the performance of the surrounding components.
Several researchers reported the performance of an experimental hemodialysis pump, although none of these studies focused on their long-term studies
Reliability of term (
Limov and Li 2000
Zhang and Li 2000.
These studies have shown that, although the EDM source produces significant bubbles, thereby hindering the flow of the fluid, resulting in degradation of the electrodes, thereby reducing the performance of the pump, both the DC and the AC sources can be used.
And these micro
Pumps use lower voltage than typical mechanical micropumps
Pump, more testing and development is still needed to optimize the design of hemodialysis and evaluate its reliability.
In addition, the related problem of exposing sensitive satellite components to magnetic fields must be addressed.
However, since the design of the magnetic pump is relatively simple and there are no moving parts, this makes it a technology that needs to be considered in modern TCS applications.
The future space exploration program will require more and more heat.
Flow cooling capacity (> 100 W/[cm. sup. -2][2201. 4Btu/h-[in. sup. 2]])
For laser and other equipment
Diode arrays and multiplechip modules (Silk et al. 2008).
To achieve this level of heat dissipation, a new thermal management method is required.
A potential approach is
Fluid loops cooled using spray. Spray Cooling.
Although spray cooling has been verified in the open-loop configuration (
Flash system through the space shuttle)
Future systems will be extended to include the loop method (Silk et al. 2008).
However, due to a lack of precise understanding of the heat transfer mechanism, spray cooling is considered a highly experimental technique in the scientific community.
Therefore, this technology also needs the work of calculation and experiment. Lin et al. (2005)
Developed a closed two.
Use fluorine inert (FC-72)
Water as working fluid.
Using water, they obtained a critical heat flow of 500 W /[cm. sup. 2](11,007 Btu/h-[in. sup. 2])
In the cooling area of 19. 3[cm. sup. 2](3. 0 [in. sup. 2]).
Future work is needed to improve understanding of the heat transfer mechanism, improve the predictive model, provide liquid management in a weightless environment, and conduct thorough testing in a weightless environment (Silk et al. 2008).
Compared with S/C peers, fluid circulation technology is more mature and more inherited.
As a result, the S/C community has benefited a lot from the success of HVAC and R & D.
However, the modern way of pumping water (i. e. , EHD)
What is being investigated by S/C is an area that may be overlooked.
Several examples of ground EHD research work were reported. Feng and Seyed-Yagoobi (2006)
Use the EHD pump of dclevel 10,000 and 15,000 V to deliver improved refrigerant distribution in the evaporator.
They found steam.
This technology can improve the compression cycle.
Singhal and Garimella (2005, 2007)
AndIverson, etc. (2009)
Various aspects of EHD pumping in high heat flow cooling system are studied.
This work focuses primarily on optimizing the design of the EHD pump for Micro Channel cooling.
They found that EHD pumps are simple to manufacture, low cost, do not require extra space, and can achieve the necessary high flow rate.
Heat pipes Swanson and Birur (2003)claim that two-
Phase technology, such as heat pipes, is clearly the main thermal control innovation of the past decade, thus defining the stateof the-art.
First patent obtained in 1942 (Reay et al. 2006)
Good heat pipe-Two were established.
Phase systems that demonstrate their practicality and reliability in many flights.
There are several changes that make them useful in many applications;
The most basic operation is to use the wick to draw the liquid from the condenser to the evaporator, where the liquid is evaporated before returning to a container with a larger density.
Diode heat pipe.
Heat pipes can also be designed to transfer heat only in one direction, although some heat will inevitably leak in the opposite direction due to conduction if the operation is reversed.
The diode heat pipe operates by using a reservoir connected to the heat pipe core to control the amount of liquid and steam in the heat pipe. Prager et al. (2002)
Describe the operation of liquidtrap,liquid-
Plug and gas-
In more detail, plug the diode.
Variable heat pipe (VCHP).
Although the diode heat pipe user container contains an excessive amount of working fluid, non-condensed gas is filled in the VCHPs user container to regulate the conduction of the device.
Figure 5 shows the operation of VCHP; Prager etal. (2002)
Please note that the front part of the gas can be considered a floating piston that is not permeable.
As the temperature of the evaporation surface increases, the steam pressure increases, forcing the non-condenser to enter the storage tank, leaving a larger condenser surface area with two-
In this way, the heat taken out of the heat pipe can be passively controlled to maintain the equipment at a relatively constant temperature.
Assuming the right size, VCHPs can generally keep the device in [range]+ or -]
Achieve the required temperature of 2 Kof without using the additional power supply.
However, this type of operation does cause some temperature changes that can be minimized through feedback control.
If the temperature of the equipment starts to drop, the heater on the reservoir can be started to expand the non-
Reduce condenser area. [
Figure 5 Slightly]Sarraf et al. (2008)
The pressure control heat pipe (PCHP)
The goal is to improve the temperature control of the VCHP while minimizing additional power usage, complexity, and response time.
This can be achieved by actively controlling the number of non-condensed gases in the heat pipe reservoir, or by actively changing the volume of the reservoir. Sarraf et al. (2008)
It is proved that the PCHP controlling the volume of the reservoir can maintain the evaporator temperature in [range]+ or -]0.
The target temperature is 1 k while the VCHP has gone through a [change]+ or -]3.
The temperature is 5 k under the same conditions.
PCHP also has a shorter response time, which takes only 30 seconds compared to the 20 minutes required for heating
VCHP with similar power consumption (Sarraf etal. 2008).
The power consumption of the PCHP is about 8 w on average, but when the system is fully loaded, the power consumption may increase to 32 W. Flat-Flat heat pipes.
For applications that require flat-panel heat pipes, for example-
The normalization of the flat surface was designed and tested.
Xie miaonov boke (2008)describe a 1. 0 mm-(0. 039in. )
Thick Thermal surface heat pipe designed for thermal management of afuel batteries with an effective heat conductivity of up to 5000 W/m-
Not sensitive to gravity.
Garimella, Soban (2001)
See the nearest apartment
Flat heat pipes advance.
They found a temperature drop in an apartment.
On the equivalent copper plate, the flat heat pipe is reduced by 83%.
Capillary pumping circuit (CPL).
Although traditional heat pipes are useful
They are state-of-the-art, reliable equipment that does not deliver heat over long distances.
Therefore, the placement of S/C components is limited to close-
This has a compound effect on increasing the support structure and quality (Hoang et al. 2003).
In addition, in terms of heat transfer, thermal density and temperature control, the future S/C will exceed the capacity of conventional heat pipes (Hoang et al. 2003).
Therefore, the Capillary pumping circuit (CPL)
Circulating heat pipes (LHP)
Next Generation Hot pipe technology that has been identified as S/CButler et al. (2002)
It is estimated that CPLs and LHPsoffer have improved at least two orders of magnitude in terms of heat transport capacity compared to conventional heat pipes.
The first CPLs proposed by NASA in 1966 is currently on-
Orbital S/C tasks and electronic cooling applications (Liuet al. 2008; Bugby et al. , 2005). A single-
Flight Experiment of CAPL-evaporator flight
2. successful flight on 1995. Three,single-
Evaporator CPLs provides successful and robust operations on nasa\'s Earth Observation System (EOS)
Terra since 1999 (Ku et al. 1996; Ku et al. 2004;
Cloud and Bugby 2007).
Similar to conventional heat pipes, CPLs relies on capillary force to drive steam from a typical polyethylene evaporator Wick to a condenser (Butler et al. 2002).
However, they use standard, non-standard
Sweat discharge pipes in most systems (Butler et al. 2002).
In addition, the system relies on hydraulic poweraccumulator (i. e. , reservoir)
Control system saturation temperature and fluid circulation (Figure 6).
The reservoir is connected to the CPL liquid tube line through smooth-
Wall tube, can be far away from the evaporator. [
Figure 6 slightly]
CPL is usually cold.
There is a deviation, which enables the loop to operate at a lower temperature and provides a good temperature control [+ or-]0. 5[degrees]C (Bugby et al. 2005; Hoang et al. 2003).
The heater of about 15 W on the reservoir can be used to control the operating temperature of the loop, and it also needs to be pre-
Adjust the loop before Forest artup (Butler et al. 2002).
When the heat is applied to the reservoir
The liquid is pumped through the system to moisten the evaporator lamp core.
This is necessary to avoid evaporation within the liquid core of the evaporator, and steam bubbles prevent liquid flow, resulting in the evaporator drying up and stopping the loop.
Loop heat pipe (LHP).
Lhp tested in the former Soviet Union for the first time at 1980 s, providing enhanced heat transfer capability similar to the toCPLs, currently in the process of 100 s on-Track task (
Dutraand Riehl 2004Bugby et al. 2005).
Conventional use of the sintering powder metal evaporator Wick and standard non-
The sweat drain pipe for most systems. The hydro-
The accumulator in LHP is called the compensation room (CC).
As shown in Figure 7, CC is connected directly to the evaporator, so it is prone to heat leakage.
The second Wick connects CC to the evaporator. [
Figure 7 Slightly]
Lhp is considered stronger than CPLs as they are able to use steam bubbles in the evaporator core.
Lhp will automatically when CPLs stop running
Adjust to a higher working temperature to maintain the necessary cooling at the c inlet.
This robustness is also evident at the beginning. up process.
Although CPLs need a pre-
The adjustment process removes steam bubbles from the evaporator core, and lhp can
Start when the heat load is applied to the evaporator.
However, the process is still very slow, and the CPL and LHP systems typically use a start-up heater of 35 w to 75 w on the evaporator to start the evaporation (Butler et al. 2002).
Due to the considerable size of CC, in some applications, the space required to combine CC and evaporator assemblies may make it more difficult for lhp to merge than CPLs.
In addition, although it has been proved in some cases that the local reservoir makes fine temperature control more difficult (Baker 2004).
If the required temperature is higher than the natural equilibrium temperature, the LHP operating temperature can be controlled using a heater of 50 W without the need for heatercontrol (Butler et al. 2002).
Although considered more robust than CPLs, temperature oscillation and instability have been found in some cases (Ku et al. 2001;
Nikitkin 2001 and Bienert).
Other studies focused on the development of improvements to CPLs, lhp and two systems specifically for low temperature applications (
Kobel and Ku 2002; Bugby et al. 2003;
Nikitkin 2002 and Bienert).
Many changes in traditional, CPL and LHP designs have been proposed and tested.
Ortenstein and so on. (2003)
A thermal control system combining LHP, two constant conductivity heat pipes, VCHP and radiators was designed and tested.
The size of the next generation of CPLs and lhp may be significantly reduced.
In a study by Wang et al. (2008)
They developed a micro
CPL can accommodate 185 people. 2 W/[cm. sup. 2](4077Btu/h-[in. sup. 2])at 165[degrees]C (329[degrees]F).
Cytrynowicz, etc. (2002, 2004)
Dedicated to the use of micro-computers to micro-scale LHP technology
Coherent porous silicon (CPS)technology. Liu et al. (2008)
Put forward a flat
Panel CPL for S/C applications.
Mixed heat pipes.
Hybrid loop heat pipe (HLHP)
Is an alternative to combining the best attributes of CPLs and lhp while overcoming the shortcomings (Hoang 2003; Bugby et al. 2005a).
Hlhp uses a reservoir configuration of CPL with a secondary liquid loop to provide a core leak of the evaporator in the main loop.
Core leakage is achieved by pumping excess liquid through the evaporator to remove any steam bubbles in the core that may cause the system to age.
According to Bugby and others. (2005a)
Ground tests have been successfully carried out but have not flown in space.
In reviewing many different two
Phase system configuration using the elements of hps and CPLs, Wrenn and Wolf (2008)
Put forward a mechanicalpumped HLHP(Figure 8).
In this configuration, studies were also conducted by Zuo et al. (2005)andPark et al. (2007)
The liquid pump replaces the secondary evaporator to cycle the excess liquid. Zuo et al.
Describe the advantages of existing technologies, including: 1)
Improve reliability; 2)
Reduced sensitivity to gravity; 3)
Improved heat flow performance; 4)
Improve heat transfer; and 5)
The temperature of the large surface. [
Evaporator heat pipe. Two-
The phase system is also able to operate with multiple evaporators, increasing the flexibility of the system to accommodate multiple devices. Multi-
The evaporator CPLs is possible and has been flying in space, including the capillary impact loop flight experiment CAPL-1 and CAPL-3 (Bugby et al. 2005). Multi-
Evaporator lhp is actually limited because the size of the reservoir becomes infinite as the number of evaporator increases (Bugby et al. 2005).
Despite this limitation, many
The evaporator system has recently been discussed more widely as lhp (Goncharov and others.
2000, Maydanik etal.
2003, Nagano, Ku 2007)than CPLs (
Ortenstein and so on. 2003). Several multi-
Developing evaporator HLHP system for on-
Orbital experiments including NASA/JPL ST
8 and the afrl dus & T program (Bugby et al. 2008).
Thorough review of on-
Single and multi-track experiments
Evaporator CPLs and LHPs, refer to Mishkinis et al. (2005)and Wang et al. (2008).
Pulsating heat pipe (PHP).
The PHPs, which was invented in the 1990 s, adopted a non-trace design to make it a potentially simple and low
Especially the cost technology for electronic cooling (Weislogel 2002).
In the study of Yang et al. (2008)
Heat flow capacity up to 1242 W /[cm. sup. 2](27,341 Btu/h-[in. sup. 2])
Experimental verification was carried out.
Php consists of a tube small enough in diameter to cause surface tension to dominate gravity and bend back and parallel to itself, as shown in Figure 9.
Depending on whether the end of the tube is sealed or connected, PHPs can be configured to turn the loop on or off. Closed-
Loop PHPs can combine the flow of the loop and the flow of the loop, which seems to improve their performance compared to the open flowloop systems.
Adding check valves to One Direction can further improve performance, but this is not common due to increased costs and complexity. [
Figure 9 omitted
The evaporator and condenser of PHP are usually located at the curved end of the tube, and the flow between the two ends is driven by the formation and disappearance of steam bubbles.
When PHP is constructed, the pipe is evacuated and then partially filled with working fluid, resulting in a mixture of liquid plugs and steam plugs.
When the mixture enters the evaporation section, it goes through Zhang\'s and feigri (2008)
Described as a constant pressure thermal addition that combines equal entropy pressure increases due to bubble expansion (i. e.
, A to B in Figure 10).
The simultaneous increase of the evaporation part of the steam pressure and the con