RU2323557C1 - Method and device for thermal protection of electronic modules - Google Patents

Abstract

FIELD: protection in emergency situations of electronic modules of flight information recorders used on aeroplanes and any other transport facilities.

SUBSTANCE: heat is abstracted from the electronic modules with the aid of a thermal protective mixture in the process of its fusion and dehydration, and the device for realization of this methods has a body, whose interval surfaces form a cavity for placing of the electronic modules in its center, thermal spacer of material based on basalt fiber adjoining the body internal surface, the space between the electronic modules and the thermal spacer is filled with a mixture of crystals of barium citrate, calcium citrate and silicic acid gel and sodium citrate, the crystals of barium citrate and calium citrate are preliminarily coated with a sheath of zinc abietate saturated with a mixture of cilicic acid and sodium zincates.

EFFECT: enhanced heat abstraction capacity of the mixture and, as a result, provided its operation during the required period of time of mixture smaller in mass and amount.

2 cl, 1 dwg

Description

The method and device for thermal protection of electronic modules belong to a special field of electronic technology and can be used for protection in emergency situations of electronic modules such as flight information recorders used on airplanes and any other vehicles.

A known method of thermal protection of electronic modules by removing heat using two layers of heat-shielding mixtures, consisting of a mixture of crystals of barium citrate and calcium citrate in a weight ratio of from 20:80 to 80:20 and a mixture of crystals of barium citrate and a double salt of sodium citrate in a weight ratio of 20:80 to 80:20, and the crystals of barium citrate, calcium and a double salt of sodium citrate are coated with a porous shell of silicic acid (application No. 2004126459/09 (028595), IPC 7 H05K 7/20, H05K 5/02).

A device is known for implementing a method of thermal protection of electronic modules, which comprises a housing, the inner surfaces of which form an internal cavity for accommodating electronic modules, a heat-reflecting casing dividing the internal cavity of the housing into two parts filled with heat-shielding mixtures, and means for removing gaseous decomposition products from the housing, moreover, part of the cavity between the inner surfaces of the housing and the outer surfaces of the heat-reflecting casing is filled with a mixture of crista catch of barium citrate and calcium citrate, part of the cavity between the inner surfaces of the heat-reflecting casing and electronic modules is filled with a mixture of crystals of barium citrate and a double salt of sodium citrate, and the crystals of barium citrate and a double salt of sodium citrate are covered with a porous shell of silicic acid (application No. 2004126459/09 (028595), IPC 7 H05K 7/20, H05K 5/02).

The described method and device of thermal protection for the combination of essential features are the closest to the claimed invention and are selected as the closest analogues (prototypes).

A disadvantage of the closest analogues is the low specific heat dissipation ability of the mixtures, as a result of which a significant mass of the mixture is required to protect the modules from exposure to high ambient temperatures for the required period of time, which is unacceptable with limited volumes.

The technical result achieved by the implementation of the proposed invention is to increase the specific heat dissipation ability of the mixtures and ensure their operation for the required period of time with a smaller amount of the mixture in mass and volume.

The technical result is achieved due to the fact that in the method of thermal protection of electronic modules by removing heat from the device using a heat shield, a mixture of crystals of barium citrate and calcium citrate in a weight ratio of 80:20 to 40:60 with silica gel is used as a heat shield and sodium citrate, the crystals of barium citrate and calcium citrate being pre-coated with a zinc abietate shell saturated with a mixture of silicic acid and sodium zincates.

A device for implementing the method of thermal protection of electronic modules comprises a housing, the inner surfaces of which form a cavity for placement of electronic modules in its center, a thermal gasket adjacent to the internal surface of the housing, means for removing gaseous products from the housing, while the space between the electronic modules and the thermal gasket filled with a mixture of crystals of barium citrate and calcium citrate with a gel of silicic acid and sodium citrate, and crystals of barium citrate and citrate Pre-coated with a coating of zinc abietate, saturated with a mixture of silicic acid and sodium zincates.

The drawing shows the design of a thermal protection device for electronic modules.

The thermal protection device comprises a housing 1, usually made of high strength metal. The housing 1 may have any desired shape, providing resistance to crushing and penetrating shock. A thermal pad 2 made of a material based on basalt fibers having high porosity and a low coefficient of thermal conductivity is adjacent to the inner surface of the housing 1. A shielded electronic module 3 is located in the center of the internal cavity of the housing 1. The heat-shielding mixture 4 occupies the space between the electronic module 3 and the gasket 2 and consists of crystals of barium citrate and calcium citrate mixed with silica gel and sodium citrate, with crystals of barium citrate and calcium citrate pre-coated with a highly porous, water-insoluble zinc abietate shell saturated with a mixture of silicic acid and sodium zincates. The housing 1 is closed by a cover 5. The housing 1 and the cover 5 have special openings for removing steam from the device.

When exposed to a high temperature on the housing 1, the energy of the incoming heat is allocated and water is evaporated from silicic acid and the salts are melted, followed by dehydration of the mixture 4. The structure of the mixture 4 is a viscous, rubbery mass, which causes water vapor to go to the housing 1 with high hydraulic resistance . The work of mixture 4 is as follows: at a temperature of the layer 103 ... 105 ° C, dehydration of the gel of silicic acid takes place, while the vapor leaves through not working salts and the coating from zinc abietate. At a temperature of 135 ° C, 150 ° C, 185 ° C, barium and calcium citrates are melted and dehydrated, while the vapor output is hindered by coating salts and finely dispersed quartz of anhydrous silica gel. At a temperature of the layer of 205 ° C in the layers of the gel and salts upstream and spent, the coating of zinc abietate melts, restrained by silica gel and spent salts, which further increases the economical consumption of water vapor for cooling.

These reactions with a uniform heat flux occur in layers, in one steam and several, “concentric shells” 0.5 ... 0.8 mm thick concentric with respect to module 3, repeating the shape of the inner surface of the housing 1 and moving from the periphery to the center. The high dehydration energy of the used mixture 4 is due to the presence of molecules of only constitutional water of primary hydration in barium and calcium citrates, an odd number of water molecules in barium citrate and calcium citrate.

The melting and dehydration phenomena of mixture 4 are accompanied by evaporation of water. When water vapor passes through the mixture 4, heat is removed from the modules 3 and the case 1 is forced to cool. This process allows you to keep the maximum temperature of the module 3 board at the level of acceptable values - 98 ... 102 ° C, that is, at the level at which the electronic module 3, located in the housing 1, does not cause significant damage. However, the accumulation of a large amount of steam inside the sealed enclosure 1 can lead to overheating of this steam and an increase in the temperature of the electronic module 3 above the critical value. To exit the steam in the housing 1, the cover 5 has special holes. The steam outlet is specially hindered by the resulting structure of the spent and partially worked out layers of the mixture 4, which leads to a more economical consumption of water vapor and, consequently, an increase in the operating time of the mixture. The thickness of the layers of the mixture 4 depends on the weight ratios of salts and gel of silicic acid in these mixtures and on the time of their dehydration.

The viscous, rubber-like structure of the mixtures contributes to the dissipation of part of the energy of the impacts on the body of the device.

The use in the proposed method and device of a heat-protective layer consisting of a mixture of crystals of barium citrate, calcium citrate, gel of silicic acid and sodium citrate, in addition, crystals of barium citrate and calcium citrate are pre-coated with a zinc abietate shell saturated with a mixture of silicic acid and sodium zincates, allowed to increase the specific heat-transfer ability of the mixture by 55-60% and ensured the protection of the electronic module with a lower mass of the mixture for at least 60 minutes at a temperature of 1100 ° C and 10 hours at a temperature f 260 ° C.

Claims (2)

1. The method of thermal protection of electronic modules by removing heat using a heat-shielding mixture, characterized in that as a heat-shielding mixture using a mixture of crystals of barium citrate and calcium citrate in a weight ratio of from 80:20 to 40:60 with a gel of silicic acid and sodium citrate, moreover, the crystals of barium citrate and calcium citrate are pre-coated with a zinc abietate shell saturated with a mixture of silicic acid gel and sodium zincates. 2. A device for implementing the method of thermal protection of electronic modules comprises a housing, the inner surfaces of which form a cavity for placement of electronic modules in its center, a thermal pad adjacent to the internal surface of the housing, and special means for removing gaseous products, characterized in that the space between the electronic modules and a thermal pad is filled with a mixture of crystals of barium citrate and calcium citrate with a gel of silicic acid and sodium citrate, and crystals of citrate bar I and calcium citrate of the pre-coated zinc abietate, a saturated mixture of silicic acid and zincates sodium.