US3811422A

US3811422A - Chemical heater tube

Info

Publication number: US3811422A
Application number: US00296361A
Authority: US
Inventors: D Olson
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1972-10-05
Filing date: 1972-10-05
Publication date: 1974-05-21
Anticipated expiration: 1991-05-21

Abstract

A chemical heater-cartridge for producing high amounts of heat without excessive pressure rises. A sealed, thin-walled, steel tube filled with solid lithium surrounding a core of Teflon powder forms the portable heater-cartridge. The exothermic reaction of this mixture, initiated by a pyrotechnic fuze, results in a high heat output and a reduction of pressure within the cartridge. This reduction of pressure permits the use of a small-mass tube which increases the rate of heat transfer. Sulfur hexafluoride vapor (SF6) or Freon may be added under pressure to enhance the reaction rate. Alkali metals, other than lithium, and fluorocarbons, other than Teflon, may be used and are equivalent reactants.

Description

United States Patent [191 Olson 1] 3,811,422 [451- May 21', 1974 CHEMICAL HEATER TUBE [75] Inventor: Donald R. Olson, State College, Pa.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

221 Filed: on. s, 1972 211 Appl. No.: 296,361

Primary Examiner-William F. ODea Assistant Examiner-Peter D. Ferguson Attorney, Agent, or Firm-R. S. Sciascia; P. Schneider 5 7] ABSTRACT A chemical heater-cartridge for producing high amounts of heat without excessive pressure rises. A sealed, thin-walled, steel tube filled with solid lithium surrounding a core of Teflon powder forms the portable heater-cartridge. The exothermic reaction of this mixture, initiated by a pyrotechnic fuze, result$ in a high heat output and a reduction of pressure within the cartridge. This reduction of pressure permits the use of a small-mass tube which increases the .rate of heat transfer. Sulfur hexafluoride vapor (S1 or Freon may be added under pressure to enhance the reaction rate. Alkali metals, other than lithium, and fluorocarbons, other than Teflon, may be used and are equivalent reactants. r

8 Claims, 2 Drawing Figures l. Field of the Invention nic fuze indicated at 16. The container holds a reactant charge including an alkali metal 12 surrounding a central fluorocarbon material 14. The alkali metal 12 may, for example. be lithium and the fluorocarbon Tef- The presentinvention relates generally to heating de- 5 Ion. The chemical reaction for such a combination vices and more particularly to a portable heating cartridge employing a mixture of solid ingredients which react exothermicly upon ignition. Because of their fast response. such heating cartridges make it feasible to boil water in water injection bottles and thus achieve the driving pressure necessary for the injection. The heaters can also be employed to melt ice and give preheat to a system to enhance starting capability.

2. Description of the Prior Art In the field of one-shot heating devices chemicals which are initially contained in a closed container react to generate heat. Such heat sources have a wide variety of uses. However, most chemical reactions employed to produce high amounts of heat also produce execessive pressures within the container. The high pressures necessitate increases in container mass or strengthing of the container in various other ways to prevent its destruction. Such modifications cut down on the heat transfer capabilities of such a container and make it less efficient.

SUMMARY OF THE INVENTION A pyrotechnic fuze is employed to ignite the reaction mixture within the heater-cartridge. The alkali metal and the fluorocarbon combine to release energy in an OBJECTS OF THE INVENTION An object of the present invention is to produce a high heat output within a hermetically sealed container and yet not cause a pressure rise within that container.

A further object of the invention is to achieve a response time several orders of magnitude higher than an electrical heater of equivalent power rating.

Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a cross-sectional view ofa heater-cartridge shown mounted in a container; and

FIG. 2 depicts a cross-sectional view taken along the line 2-2 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS would be: Li (solid) F. (50nd) (solid) heat 4 LiF (solid) Li C WK can better be sn ifi FIG. '2 the li thiiim fills the container 10 with the exception'ofa center core which may be filled with tetrafluoroethylen'e powder. As shown in FIG. 1, the tubular container 10 may be employed to heat water in a water injection bottle to achieve the necessary driving pressure for injection.

To enhance the reaction rates, it is also desirable, but not necessary, to have a third reactant present. It has been found that sulfur hexafluoride vapor (SP or Freon gas may be added under pressure to enhance the reaction rate. Such an addition adds to the energy liberated in the reaction.

It should be further noted that the charging pressure of the SF or Freon gas is crucial. It has been found that 100 psig gives a start-up time of A second as compared to 2-3 seconds for a 50 psig charge.

Except under unusual conditions, it is not feasible to install a stoichiometric mixture of the reactants in the tube. The adiabatic reaction temperature is of the order of 6,606 E: which will melt the containing stmcture unless the heat is dissipated from the outside of the tube at an exceedingly high rate. To solve this problem, the amount of fluorocarbon used will depend upon the heat transfer capability of the heater tube.. The role played by the excess alkali metal in this process is not passive. Due to the very high thermal conductivity of liquid alkali metals, they serve as an excellent heat transfer medium between the reactive products and the containe'rs metal wall. This fact also.

produces a heater with a very rapid response, several orders of magnitude higher than that in an'electrical heater of equiyalent range.

The tube is operated simply by detonatingthe fiuz e 16. A 1 inch diameter heating cartridge, l2 inches long with Teflon added to react with only one third of the lithium present, produces a heat equivalent in energy to that produced by a 600 watt electrical heater operating for a period of 20 minutes.

Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is: l. A portable heater tube comprising: a hermetically sealed container; a reactant charge disposed within said container; said reactant charge being composed of lithium, tetrafluoroethylene. and a third constituent chosen from the group consisting of sulfur hexafluoride and Freon gas; and

' means connected to said container to initiate a chemical reaction in said reactant charge.

2. The portable heater tube of claim 1 wherein the FIG. I, which illustrates a preferred embodiment of lithium is present in excess amounts in proportion to a the heater-cartridge. shows a tubular container 10 which may be formed of stainless steel. The container [0 may be hermetically sealed by a plug and pyrotechstoichiometric mixture.

3. The portable heater tube of claim 1, wherein the lithium substantially fills the container with the exception of a central core, said core being substantially filled with said tetrafluoroethylene.

4. The portable heater tube of claim 1 wherein the third constituent is sulfur hexafluoride at a charging pressure of at least I psig.

5. The portable heater tube of claim I wherein the third constituent is Freon gas at a charging pressure of at least 100 psig.

6. The portable heater tube of claim 5 wherein the lithium substantially fills the container with the exception of a central core, said core being substantially filled with said tetrafluoroethylene.

7. A portable heater tube comprising:

stoichiometric mixture.

Claims

2. The portable heater tube of claim 1 wherein the lithium is present in excess amounts in proportion to a stoichiometric mixture.
3. The portable heater tube of claim 1, wherein the lithium substantially fills the container with the exception of a central core, said core being substantially filled with said tetrafluoroethylene.
4. The portable heater tube of claim 1 wherein the third constituent is sulfur hexafluoride at a charging pressure of at least 100 psig.
5. The portable heater tube of claim 1 wherein the third constituent is Freon gas at a charging pressure of at least 100 psig.
6. The portable heater tube of claim 5 wherein the lithium substantially fills the container with the exception of a central core, said core being substantially filled with said tetrafluoroethylene.
7. A portable heater tube comprising: a hermetically sealed container; a reactant charge disposed within said container; said reactant charge being composed of lithium and tetrafluoroethylene, wherein the lithium fills the container with the exception of a central core, said core being filled with said tetrafluoroethylene; and means connected to said container to initiate a chemical reaction in said reactant charge.
8. The portable heater tube of claim 7 wherein the lithium is present in excess amounts in proportion to a stoichiometric mixture.