FIELD OF THE INVENTION
The present invention generally relates to advanced shaped hydroformed quilted panels (ASHQP). More particularly, the invention relates to an advanced shaped hydroformed quilted panel (ASHQP) to operate at 80K and 4K cryogenic temperature.
BACKGROUND OF THE INVENTION
Regenerative Helium and Hydrogen isotope sorption unit (RHHISU) is an important element of any tokomak. RIHHSU is able to adsorb lighter molecules like hydrogen isotopes and Helium due to an intimate interaction between ultra-cooled surfaces (-4K) and further due to the presence of inhabiting surfaces of Advanced High Sorption Sorbents (AHSS). AHSS needs to be cooled to -4K, which can only be achieved by deployment of supercritical Helium. There is an alternative process in which a GM cryocooler is employed whose cold head can achieve such low temperatures.  The limitation of GM cryocooler is its limited heat extraction ability (Maximum Up to 1.5 watt at ~4K). Further, a JM cryocooler with JT valve technology can also be used. This can extract about 5 watts at -4K. Both the GM cryocooler and JM cryocooler with JT valve have the practical limitation of low wattage extraction, wherein a tokamak, the total energy to be extracted can go upto several hundreds of watts for which several units of closed cycle static coolers need to be developed. As opposed to the same, a single RIHHSU  is  enabled  to  achieve  the  required  heat  extraction,  with  less complicacies. Hence, for effective operation of a tokamak, the option of RIHHSU can  make the whole scenario very simplified  rather than  a  complicated cryocooler scenario which pose design including functional limitations.

Prior art tube welded panels (Refer Fig2) for RHHISU. This kind of panels had many limitations for example,:
1) The cryogen flows only through the tubular channels therefore does not come in contact with all the parts of the panels. Therefore non uniform cooling of the panel surface.
2) When used with materials like stainless steel, and thermal conductivity of stainless steel being very low at low temperature, the non uniform temperature profile of the panel surface further get enhanced.
3) Welding between the plate and the tube results in selective contact area therefore the conduction heat transfer between the plate and tube is through selective passages. This causes poor heat transfer between the plate and the tube.
4) Such panels also use copper plates. Copper to some extent results in higher thermal conductivity, however it possess manufactuiing difficulties in terms of welding/brazing. It is also difficult to get a high emissivity surface in the order of 0.1 to 0.2 from copper plates. With the passage of timer copper being susceptible to oxidation especially when the surface is polished the surface emissivity is reduced.
As a consequence of all the above limitationsr a large amount of cryo fluid requires to be circulated through the panels to obtain desired temperature profile on the panels, which still cannot totally avoid the hot spots on the panel. These limitations makes its unusable for application in RHHISU.

The RHHISU is a gas entrapment equipment capable of adsorption of gases including Helium and Hydrogen Isotopes. The principle of operation is that gaseous substances are bouded to the cold surfaces within the sorbent coated surface. This system can also be used as high capacity pumping system to pump mainly hydrogen isotopes and helium gases. It is also recommended to be used in a fusion grade reactor exhaust pumping systems.
The ASHQP basically carry cryogenic fluid and act as a cold body, to radiatively shield the colder bodies from radiative heat of hotter bodies. These panels are used in several applications like radiation shields for cryo-vessel and radiative protection for superconducting coils, or in any cryogenic environment shielding.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an advanced shaped hydroformed quilted panel (ASHQP) to operate at 80K and 4K cryogenic temperature, which is capable of adsorption of gas including helium and hydrogen isotopes.
Another object of the invention is to propose an advanced shaped hydroformed quilted panel (ASHQP) to operate at 80K and 4K cryogenic temperature, which allows bonding of gaseous substances to the cold surface within the sorben coated surface.
A still another object of the invention is to propose an advanced shaped hydroformed quilted panel (ASHQP) to operate at 80K and 4K cryogenic temperature, which is enabled to carry cn/ogenic fluid and act as a cold body to radiatively shield colder bodies from radiative heat from hotter bodies.

A further object of the invention is to propose an advanced shaped hydroformed qUilted panel (ASHQP) to operate at 80K and 4K cryogenic temperature, which can be adopted as a high capacity pumping system to pump hydrogen isotopes and helium gases.
SUMMARY OF THE INVENTION
Accordingly, there is provided an advanced shaped hydroformed quilted panel
(ASHQP) to operate at 80K and 4K cryogenic temperature.
To build an improved ASHQP, the following technical parameters are selected:
• Fabrication parameters for manufacturing cryogenic shield,
• Scalability of fabrication process and design parameters for large size shield manufacturing,
• Scaling of the nozzles and connectors for a given mass and heat transfer including test simulation,
• Technology know how in welding for cryogenic panels.
In order to produce an improved ASHQP, the inventors through research and experimentation recognized the important process parameters for example weldment of the material, joining of two plates, joining of ports or nozzles, hydro-forming, flow patterns, vacuum leak tightness, and performance of the panels after thermal shocks. Upon configuration of Panels with different shape and size, a flow analysis was conducted each case, to optimize the flow patterns, and pressure drop. Based on the analytical results, the associated parameters for example, weld spacing, port size, spot gap for various burst pressure requirements and pressure drop are decided. Various processes of welding were

tried out to finalize a selected set of process parameters considering the process and product variables. The improved ASHQP as produced has been tested for thermal cycling and leak tightness for various cryogenic applications.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1    Shows a tube welded flat thermal shield panel according to the
invention. Figure 2    Shows a tube welded cylindrical thermal shield panel according to
the invention.
DETAIL DESCRIPTION OF THE INVENTTnN
General arrangement for a tube welded flat thermal shield panel is shown in fig-1 and a tube welded cylindrical thermal shield panel is shown in fig-2.
• As shown in figure 1a bend tube (1) of material SS 304L/SS316L is welded on to a flat SS 304L/SS316L sheet (2) surface. The straightness and surface finish must be good for better welding joint and to accomplish the functional requirement i.e. better heat transfer.
• The bending of the tube (1) is done in such a manner so that there is no "pinching" (reduction in cross section) at the bent position to avoid un desirable flow of cryogenic fluid in this area.
• Straightness of the tube (1) is another important aspect for better surface contact between the tube (1) and the sheet (2) which leads to better heat transfer.

• It may be essential at times to manufacture panels out of different sheet thicknesses. The plate thickness was found to be 1.5 - 2.0 mm thick and tube thickness of 1.5 - 2.0 mm thick for the best performances.
• Proper fixturing is implemented to avoid any distortion following the welding process, due to lower thickness of both the tube (1) and the SS sheet (2).
• Optionally, Copper tube and sheets are also used in place of SS 304Lj316L due to better thermal conductivity however it poses manufacturing difficulties in terms of welding/brazing.
• GTAW/Brazing is used for joining of the tube and sheet.
• The Sheet (2) with the welded tube (1) is a cylindrical thermal shield as shown in fig-2. The cylindrical tube may be made out of a flat sheet followed by rolling process or it may be a standard SS 304L/316L seamless tube (1) of required diameter and thickness.
Austenitic steel for example, SS304L or 316L or 316NL are found to be most suitable for this type of application.
As the other constituent components of the panels such as port and weldments also have to be of same material, therefore SS304L was selected to work with.

A. Weld Spacing
Various trials with different gaps right from edge till deeper spacing are tried out with an objective of distortion control and leak tightness. To achieve leak tightness (in the order less than 10-10 mbar) and distortion control and mounting space, weld space has been fixed for different panels.
B. Weld Patterns
Trials were carried for different weld patterns like single spot, stitch seam, double spot, seam channeling with different end gap and it is concluded that a stitch seam and double spot, provide equal mechanical strengths, whereas the mechanical strength improves by 80% between a single spot and a double spot. It is also observed that the end bulge differs significantly for different end gaps in seam channeling.
C. SDOt or Bulge Spacing
Different spot spacing were tried out and it is found that the bulge between the spots substantially increases with a slight increase in the bulge space. An attempt has been made to establish a relationship between the bulge height and spot spacing.
D. Panel Bulge Heighfr
An experiment has been conducted to evaluate the effect of bulge height over the length of the channel. It is observed that the bulge height of the bubbles differs reasonably due to increase in channel length. Accordingly, different length

Of the several joining process available (TIG welding, Laser welding, Roll Seam welding), roll seam welding process was selected due to its flexibility cost effectiveness and cleanliness in operation.
Various port connections like vertical port, horizontal port, fish mouth port and inclined port were tried and the optimum parameters were selected.
Hydro-forming with different fluids and different type of die contours were tried and panels of different shape and size were designed, CFD conducted to understand its flow behavior, pressure drop and conclusions drawn on weld spacing, port size, spot gap for various burst pressure requirements and pressure drop requirements.
Physical prototypes of different shapes and sizes, different qUilt geometry, port connections were made parameters were selected with the consideration of process limitations, quality control stipulations, and physical behavior for incorporating improvement in the panels. The process parameters were determined keeping in mind the process and product variables.
Selection of welding spacing, patterns, spot or bulge height was made based on various trials with different gaps from the edge upto the deeper spacing, with an objective of distortion control and leak tightness. To achieve the leak tightness (in the order less than 10-10 mbar) and distortion control and mounting space, weld space has been fixed for different panels. The brief description is as given below--

panels were manufactured with similar channel formation. Maintaining the width of the panels as constant, observations were made on the bubble height at the middle and at both ends. The bubble height is found to be higher than the channel length, when the bubble in the middle of the channel is increased.
E. Panel Sheet Thickness:
It may be essential at times to manufacture panels out of different sheet thicknesses. The object could be a reduction in weight, an increase in burst strength, and in structural strength. It is quite imperative for given hydro forming pressure, the bubble height would differ. Lower the thickness of the sheet, higher the bubble height. Panel thickness was found to be 3mm thick dual sheet for the best performances.
Use of different fluid for forming ■
Hydro forming is the process which needs to be employed for forming of the panels. Different fluids can be used for this purpose. For different forming pressure different fluids can be employed. e.g. for forming up to 20 bar compressed air can be used. For forming up to 100 bar water can be used. For forming beyond 100 bars hydraulic oil should be used. If air is used for forming then there exists risk of explosion due to compressibility of air. If oil is used then cleaning of oil post forming operation remains as the biggest issue. Water is the most suitable candidate for this application. Water can be easily evacuated by baking. However viscosity of water being very low special pumps need to be employed for this purpose.

Use of die for forming:
For different applications different panels needs to be designed with specific features, they could be different weld patterns, different flow paths, different bubble heights, different pressure drop, different temperature rise etc. It is practically impossible to design a variety of dies for this purpose. Therefore generic dies with flat surface with clamping on weld area is more advisable than specific dies. It is also advisable that the panel be designed so that it gives rise to minimum bubble height difference in forming.
The advantages of the invention ■
a) Being a double layered construction, the ASHQP has an inbuilt flow path for ScHe to flow without coming in contact with AHSS.
b) Being qUilted in shape it breaks down the monotony of stream line flow and therefore increases the turbulence which in turn increases heat transfer.
c) The other side of the ASHQP offers a clean surface for preparation of ASRB (Advanced Regeneration Sorbent Bed). Further, the quilted shape of the ASHQP, the surface area increases in comparision with flat surface of prior art, which gives opportunity to fix more AHSS.
d) Being hydro formed it is possible to channelize the flow of ScHe into different sections of the ASHQP without difficulty.

e) ASHQP can be manufactured in various shapes and sizes to meet the demand of space limitation and flow connection restriction.
f) The ASHQP can withstand a very high degree of internal pressurization which occurs in the event of phase transformaiion of cryo fluids.
g) ASHQP although has a qUilted surface it has got no sharp corners or cavities for entrapment of gases which makes it a good choice for application relating to cryogenics and ultra-high vacuum where outgassing plays an important role.
There is another application of the ASHQP, that is to say, the panel should act as a radiation shield to protect the ultra low temperature surface with reference to the room temperature surface. These ultra low temperature surfaces are typically cooled upto 80 K by passing LN2 (Liquid Nitrogen) and He gas at 80K through the surfaces.
The greatest advantage of the ASHQP is that it can be made leak tight up to 10-9 mbar lit/see which does not allow any of the cryogens floWing inside to come out and avoid any unfavourable condition.

WE CLAIM :
1. An advanced shaped hydroformed qUilted panel (ASHQP) to operate at 80K and 4K cryogenic temperature.
- a perfectly straightened metal tube (1) with surface finish to allow a higher heat transfer, the metal tube (1) being bent without any degree of pinching at the bent position to eliminate undesirable flow of cryogenic fluid in the bent area; and
- a flat metal sheet (2) clamped to the metal tube (1) ina clamping device and joined together using a roll seam welding technique by maintaining weld spacing such that leak-tightness and distortion control can be prevented;
wherein the tube, sheet, and weldments are selected of identical metal grade and standard.
2. The hydroformed panel as claimed in claim 1, wherein different fluids such as compressed air, water, and hydraulic oil are used depending on the desired forming pressure 20 bar, 100 bar, and greater than 100 bar respectively.
3. The hydroformed panel as claimed in claim 1, wherein austenitic steel for example SSO 304L or 316L or 316NL for the constituent components of the panel including panel ports is used.
4. The hydroformed panel as claimed in claim 1, wherein the plate thickness and the tube thickness respectively are 1.5 to 2.00 mm and 1.5 to 2.00 mm, and wherein copper tube and copper sheet can be used in place of austenitic steel.

5. The hydroformed panel as claimed in any of the preceding claims, wherein the tube and sheet when fabricated optionally constitutes a cylindrical thermal shield.
6. The hydroformed panel as claimed in claim 1, wherein the panel surface is formed in quilted shape to increase turbulence including heat transfer.
7. The hydroformed panel as claimed in claim 1, wherein the welding technique can be GTAWjBrazing.