Problems of creating a system of cooling of the phased array centimetric

Аuthors

Tokmakov D. I.

Kompany «Radiofizika», 10, Geroev-Panfilovcev Str., Moscow, 125363, Russia

e-mail: dimatok87@gmail.com

Abstract

The aim of the presented research consists in the choice of the junction type of cooling channels and headers of the active phased array’s cooling system, junction testing and operability of thin-walled tubes estimation. An analysis of the obtained results has been performed.
Deforming thin-walled metal cooling channels are an efficient solution for heat sink. The swelling by the internal pressure of the thin-walled tube secures a tight stable mechanical and thermal contact of cooling channel and cooled surface, then the heated coolant liquid flows ot through the exhaust manifold to the heat exchanger.
The main requirements to the coolant system are the tight contact of the thin-walled tube and the heat transferring surface to adjoining in the area of width about 30mm, the reliable joints securing leaks’ absence.
To minimize the thermal resistance in the contact the cooling channels should be mechanically tighten to the cooled object but the modern phased arrays do not allow place the clamping mechanism. An efficient alternative method consists in using of the coolant’s pressure to swell the thin wall pipes and provide contact of the cooled wall and the pipe. To investigate the proposed approach the stainless steel pipe 12X18H10T with wall thickness 0.25mm rolled out to the flat tube with dimensions 45x3.5x0.25mm was chosen.
On the basis of the preliminary computation it was found that the pipe sections with a gap of 0.1 mm secures the required contact area length of 30 mm at a pressure of 2 bar. The experimental results have shown that the required area length can be provided at a pressure 1.5bar.
The tests have shown that the soldered joint has sprung a leak that appears under cyclic loading of the pipe. The leak was avoided by increasing the tinning zone up to 20mm; the improved section stood for 3000 cycles.
One of the tested specimens has the soldered joint of the pipes to the collector. The small pipe’s thickness results the deformation of the pipes heated during the soldering so that the required tight contact of the pipe and the collector can’t be secured. This deformation can be avoided by using some supplementary parts so that results structure’s fragility and damaging of the soldered joints during transporting and installing of the radiator in tests device.
A laser welding was used as another joint method. The welding was carried out on the specimen similar to this used to test the soldered joints. A collector’s fragment and a small section of thin-walled tube were used as a specimen to test at pressures up to 5 bar and no leak was found.
It was shown that the cooling system with thin deformable tube can be efficient but requires more careful design including the use of other materials (e.g. 36NHTYU). It has been found that the laser welding provides the joint of the best strength. The most accessible and maintainable are the mechanical and solder ones.
Practical implication.
The proposed cooling system can be used in the array antennas with high-density radiating elements / modules of a stationary or mobile systems.
The main disadvantage of the proposed cooling system is the probability of foreign objects into the gap between the cooled wall and the thin-walled pipe so that decreases the heat contact patch and results deformation and damage of the thin pipe. The dust protection of the antenna system must be used to avoid the mentioned defect.

Keywords:

active phased-array antenna, the system cooling, thin-walled tubes

References

1. Krahin O.I., Radchenko V.P., Vencenoscev D.L. Radiotekhnika, 2011, №10, p.88-94
2. Petrunin I.E. Fiziko-khimicheskie protsessy pri paike (Physico-chemical processes in soldering), Moscow, «Vysshaja shkola», 1972, 280p.
3. Svarka lazernaya impul'snaya. Soedineniya svarnye tochechnye. Osnovnye tipy, konstruktivnye elementy i razmery, GOST 28195-91 (Pulsed laser welding. Welded joints point. Main types, elements and dimensions. State Standart 28195-91), Moscow, Standarty, 2005, 10 p.

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