GB1578333A - Method of heating a mixture of gases to be breathed - Google Patents

Description

(54) METHOD OF HEATING A MIXTURE OF GASES TO BE BREATHED (71) We, INTERNATIONAL RESEARCH & DEVELOPMERr COMPANY LIMITED, a British Company, of Fossway, Newcastleupon-Tyne NE6 2YD, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to heating apparatus which finds particulat application to breathing apparatus for conditions in which hypothermia may occur, for example, in deewsea diving.

There exists a problem for divers involved in deep sea diving operations in that hypothermia can occur due to the high loss of body heat through respiration.

The solution to this problem is to heat the mixture of gases for breathing to compen- sate for the respiration heat loss, and known methods involve the provision of a heating source to indirectly heat the cold gas mixture, normally comprising a mixture of oxygen and helium, by means of heat exchangers. Since the heat exchangers need to be located in close proximity to the diver on the sea bed, heating elements or a supply of heated water has been employed. These arrangements are not entirely satisfactory since the Source of heat or heat energy has to be fed from a remote position to a position in proximity to the diver and the heat exchangers can be bulky and inefficient. Transmission of the heating source from a remote position can also present difficulties in the control of temperature to suit an individuaI diver under differing conditions of activity.

The object of this invention is to provide improved apparatus which does not require provision of a remote supply nor the need to manually control the temperature of the gas mixture and therefore results in more efficient apparatus.

According to the present invention a method of producing heat in a mixture of gases to be breathed, the mixture contained ing added hydrogen, in an amount not more than of the order of 04% by volume, and oxygen; comprises passing the mixture through a chamber containing a catalyst which causes the hydrogen and some of the oxygen to combine exothermically leaving sufficient oxygen in the re- maining mixture for breathing require- ments.

The initial gas mixture includes sufficient oxygen for the mixture remaining after heating to be fit for breathing purposes.

The gas mixture may be oxygen and helium.

The invention also provides an apparatus for producing heat in a mixture of gases to be breathed, the mixture containing added hydrogen, in an amount not more than of the older of 04% by volume, and oxygen; the apparatus comprising a source of oxygen and hydrogen, a breathing apparatus and a chamber containing the catalyst, the chamber having an inlet connected to the source and an outlet connected to the breathing apparatus.

Preferably the catalyst is a metal from the platinum group carried by a suitable substrate.

Said breathing apparatus may be a diver's demand valve.

The breathing apparatus may be a breathing mask for the treatment of patients suffering from exposure or hypo- thermia.

The invention will now be described, by way of example only, with reference to the drawing accompanying the Provisional Specification, which shows diagrammatically heating apparatus in accordance with the invention.

The apparatus comprises a having gas-tight cylindrical chamber 10 having apertured end walls 11, 12 through which thaere is fixed in a gas-tight manner a through pipe 13. The upper end 13a of pipe 13 forms an inlet for connection to a source of cold gas, the lower end 13b forms an outlet for connection to a diver's demand valve.

Within the chamber 10 and surrounding the outside of pipe 13 is fixed in gas-tight manner an inner chamber 16 containing a quantity of catalyst material 18 which may be palladium on alumina granules. Between the outside of chamber 16 and the inside wall of chamber 10 there is defined a gas-flow space 19.

Preferably the catalyst is a metal from the platinum group carried by a suitable substrate, for example, palladium on alumina granules, as described above. It may also consist of platinum on a stainless steel honeycomb structure, platinum on a fibrous ceramic such as alumina or alumino-silicate or palladium on a fibrous ceramic.

Palladium on a charcoal or carbon substrate may also be employed.

The upper region of pipe 13 is provided with two regions having through bore perforations, region 14 outside the inner chamber 16 and region 15 inside the inner chamber, similar through bore perforations 17 are provided in the lower region of chamber 16. A control valve 20 comprising a stem 21 having a radial through bore 22 is journalled in a gas-tight manner through the wall of chamber 10 and pipe 13 and may be rotated so as to control the flow of gass through inlet 13a into pipe 13.

The cold gas mixture may be contained in a pressurized container, not shown, and may be, for example, air or another mixture of nitrogen and oxygen. Helium or another inert gas mixed with oxygen can be used. For diving purposes a mixture, containing an amount of oxygen such that, after heating, the mixture contains 10% oxygen, is used, to which is added a proportion of hydrogen of the order of 03% by volume for mixtures of helium and of the order of 04% for nitrogen mixtures.

The gas can be pre-mixed in pressurised containers or it may be held in separate containers and mixed in the correct proportions immediately prior to use.

The cold gas supply is connected to inlet 13a of pipe 13 and allowed to flow into the pipe, the gas is directed through perforated region 14 into the flow space 19 to flow downwards in the annulus between chambers 10 and 16 thence the gas flows through perforations 17 into contact with the catalyst bed material 18 and the catalyst brings about a reaction between the hydrogen in the mixture and some of the oxygen to release a quantity of heat which warms the remaining gas mixture and at the same time also heats the catalyst material. The gas then flows upwards through the upper regions of the catalyst bed into the perforated region 15 and thence into the pipe 13 to outlet 13b which is connected to the diver demand valve, not shown. Heat loss from the catalyst bed 18 is minimised by virtue of gas flow over the outside of inner cylinder 16.

Fine control of the gas temperature is achieved by means of control valve 20 which can be turned to position the through bore 22 in stem 21 so as to allow a proportion of the cold inlet gas to pass directly through the bore of pipe 13, to outlet 13b, thus by-passing the catalyst 18 and reducing the temperature of the gas emerging through perforated region 15.

Thus from the foregoing description it will be seen that the energy required for heating the gas is contained within the cold gas itself in the form of a fixed proportion of hydrogen. The primary control of the temperature is determined by the hydrogen content of the mixture and is independent of the mass flow rate of the gas, i.e. the temperature is independent of pressure, density and volume flow rate.

Thus there is no requirement for manual control of temperature other than to adjust the unit for an individual diver.

This invention is not limited to the construction of heater described with reference to the specific embodiment nor to the specific catalyst referred to. Alternative constructions and materials may be used; also the outlet need not be limited for connection to a diver demand valve.

The invention is not limited to application to the specific embodiment described, for example, the invention may find application for the treatment of patients suffering from exposure or hypothermia. In this latter case, the breathing of warm air through a mask will aid the recovery of the patient. The hydrogen content of the mixture may be higher than that used for diving purposes so that a temperature of gas mixture higher than normal body temperature may be employed. Situations where revival equipment such as that described above may be employed include mountain rescues lifeboats, ships, hospitals and ambulances.

WHAT WE CLAIM IS:- 1. A method for producing heat in a mixture of gases to be breathed, wherein the mixture, which contains added hydrogen, in an amount not more than of the order of 04% by volume, and oxygen, is passed through a chamber containing a catalyst which causes the hydrogen and some of the oxygen to combine exothermically, leaving at least sufficient oxygen in the remaining mixture for breathing requirements.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. 13. The upper end 13a of pipe 13 forms an inlet for connection to a source of cold gas, the lower end 13b forms an outlet for connection to a diver's demand valve. Within the chamber 10 and surrounding the outside of pipe 13 is fixed in gas-tight manner an inner chamber 16 containing a quantity of catalyst material 18 which may be palladium on alumina granules. Between the outside of chamber 16 and the inside wall of chamber 10 there is defined a gas-flow space 19. Preferably the catalyst is a metal from the platinum group carried by a suitable substrate, for example, palladium on alumina granules, as described above. It may also consist of platinum on a stainless steel honeycomb structure, platinum on a fibrous ceramic such as alumina or alumino-silicate or palladium on a fibrous ceramic. Palladium on a charcoal or carbon substrate may also be employed. The upper region of pipe 13 is provided with two regions having through bore perforations, region 14 outside the inner chamber 16 and region 15 inside the inner chamber, similar through bore perforations 17 are provided in the lower region of chamber 16. A control valve 20 comprising a stem 21 having a radial through bore 22 is journalled in a gas-tight manner through the wall of chamber 10 and pipe 13 and may be rotated so as to control the flow of gass through inlet 13a into pipe 13. The cold gas mixture may be contained in a pressurized container, not shown, and may be, for example, air or another mixture of nitrogen and oxygen. Helium or another inert gas mixed with oxygen can be used. For diving purposes a mixture, containing an amount of oxygen such that, after heating, the mixture contains 10% oxygen, is used, to which is added a proportion of hydrogen of the order of 03% by volume for mixtures of helium and of the order of 04% for nitrogen mixtures. The gas can be pre-mixed in pressurised containers or it may be held in separate containers and mixed in the correct proportions immediately prior to use. The cold gas supply is connected to inlet 13a of pipe 13 and allowed to flow into the pipe, the gas is directed through perforated region 14 into the flow space 19 to flow downwards in the annulus between chambers 10 and 16 thence the gas flows through perforations 17 into contact with the catalyst bed material 18 and the catalyst brings about a reaction between the hydrogen in the mixture and some of the oxygen to release a quantity of heat which warms the remaining gas mixture and at the same time also heats the catalyst material. The gas then flows upwards through the upper regions of the catalyst bed into the perforated region 15 and thence into the pipe 13 to outlet 13b which is connected to the diver demand valve, not shown. Heat loss from the catalyst bed 18 is minimised by virtue of gas flow over the outside of inner cylinder 16. Fine control of the gas temperature is achieved by means of control valve 20 which can be turned to position the through bore 22 in stem 21 so as to allow a proportion of the cold inlet gas to pass directly through the bore of pipe 13, to outlet 13b, thus by-passing the catalyst 18 and reducing the temperature of the gas emerging through perforated region 15. Thus from the foregoing description it will be seen that the energy required for heating the gas is contained within the cold gas itself in the form of a fixed proportion of hydrogen. The primary control of the temperature is determined by the hydrogen content of the mixture and is independent of the mass flow rate of the gas, i.e. the temperature is independent of pressure, density and volume flow rate. Thus there is no requirement for manual control of temperature other than to adjust the unit for an individual diver. This invention is not limited to the construction of heater described with reference to the specific embodiment nor to the specific catalyst referred to. Alternative constructions and materials may be used; also the outlet need not be limited for connection to a diver demand valve. The invention is not limited to application to the specific embodiment described, for example, the invention may find application for the treatment of patients suffering from exposure or hypothermia. In this latter case, the breathing of warm air through a mask will aid the recovery of the patient. The hydrogen content of the mixture may be higher than that used for diving purposes so that a temperature of gas mixture higher than normal body temperature may be employed. Situations where revival equipment such as that described above may be employed include mountain rescues lifeboats, ships, hospitals and ambulances. WHAT WE CLAIM IS:-

1. A method for producing heat in a mixture of gases to be breathed, wherein the mixture, which contains added hydrogen, in an amount not more than of the order of 04% by volume, and oxygen, is passed through a chamber containing a catalyst which causes the hydrogen and some of the oxygen to combine exothermically, leaving at least sufficient oxygen in the remaining mixture for breathing requirements.

2. A method as claimed in claim 1 in

which the mixture of gases comprises helium.

3. A method as claimed in claim 1 or 2 in which the catalyst is a metal of the platinum group carried on a substrate.

4. A method as claimed in claim 3 in which the catalyst is palladium on a substrate of alumina granules.

5. An apparatus for producing heat in a mixture of gases to be breathed, the mixture containing added hydrogen, in an amount not more than of the order of 04% by volume, and oxygen; the apparatus comprising a source of oxygen and hydrogen, a breathing apparatus and a chamber containing the catalyst, the chamber having an inlet connected to the source and an outlet connected to the breathing apparatus.

6. An apparatus as claimed in claim 5 including a by-pass valve for directing part of the mixture directly from the inlet to the outlet.

7. An apparatus as claimed in claim 5 or 6 in which the inlet to the chamber is from an outer container which surrounds the chamber and through which the incoming gas flows.

8. An apparatus as claimed in claim 5, 6 or 7 in which the breathing device is a diver's demand valve.

9. An apparatus for producing heat in a mixture of gases for breathing, comprising a breathing apparatus and an apparatus substantially as described with reference to the drawing accompanying the provisional specification.