diver membrane catalytic heating system

Revolutionary Diver Membrane Catalytic Heater System By Global Heating Tech

We present a case study in the application of our catalytic heater system for divers. The particular characteristics that a scuba diver would require for a portable heater are:

  • make it as simple as possible
  • the heater must be separate from the divers air supply
  • a pure compressed oxygen supply is available
  • install automatic thermostatic controls. The diver will be too busy to worry about adjusting temperature for his own comfort, and it may also be unsafe because of the divers inability to sense absolute temperature
  • a critical test will be to see how the heater will operate from 1 to 10 atmospheres (14.7 to 147 psi)
  • the dominating new parameter on the membrane catalytic heater for a dive suit will be the effect of the ambient pressure changes
  • regulators freeze up in cold conditions and could use a heater, too

We discussed a variety of system designs with the major variable in the system of how heat is uniformly delivered and distributed to the diver's body. The major systems considered:

  • closed loop water circulation
  • open loop water circulation
  • open heat pipe system using boiling fuel
  • flexible sealed heat pipe systems at ambient pressure
  • rigid sealed heat pipe system
  • metallic conductors
  • exhaust gas stream circulation
  • aspirated exhaust gas stream and water circulation

We chose the aspirated exhaust stream circulation with ambient water injected into the flow with an aspirator as the best solution. This allows the temperature from the heater to be dropped to a temperature below the boiling point of water and also capture the heat from exhaust by putting some of the carbon dioxide into the water solution. If there were a malfunction of the heater or internal leak, the exhaust flow would be primarily water. Unburned fuel would be dissolved and carried away by the water. Leaks would be easy to detect in a dry suit and would be non-hazardous. The thermostat sensor would throttle back the heater if there were an abnormal temperature rise due to a blocked aspirator inlet flow.

A thermostat would control the oxygen delivery. A membrane would control the fuel delivery to achieve an approximate stoichiometric mixture of fuel and oxygen while the oxygen concentration varies by a factor of 10 with water depth. It is expected that the heater would operate above the boiling point of the fuel to achieve this, thereby achieving a fuel delivery proportional to gas pressure. This is important because the oxygen concentration is expected to vary by a factor of 10 times due to the gas pressure varying from one to ten atmospheres.

Components of a System with a target of 200 Watts for two to six hours and thermostatically controlled.

  • bladder pressurized methanol fuel ampoules
  • pressurized Oxygen bottle
  • pressure regulator from oxygen bottle
  • tubing from methanol fuel ampoule and oxygen bottle
  • fuel membrane
  • catalyst bed
  • reaction chamber containing the fuel membrane and catalyst bed
  • aspirator on exhaust
  • water inlet flow line - It may flow around the reaction chamber to capture heat
  • the end of the exhaust line could flow around heat regulators to avoid freeze up and scavenge the last usable heat
  • outlet exhaust line looped around the suit, it may make several loops back and forth from the heater
  • thermostat (passive with thermal wax controlling valve, or electronic controller and electrical valve)
  • oxygen control valve
  • check valve to prevent water from back flowing into the heater.

Several features of the system over possible alternative systems are:

  • methanol fuel is water-soluble and would not present a hazard in a marine environment
  • alternative gaseous fuels such as hydrogen, butane, and propane present a storage hazard in boats and could build up under water and in trapped spaces creating an explosive mixture with air or oxygen. Naphtha and kerosene are liquid fuels but also have a similar hazards because of lack of solubility in water and due to their low density will float to the surface of the water. Ethanol is a substitute fuel that is also water-soluble and would work with the catalyst, but it would have less complete catalytic combustion at low temperatures
  • the membrane allows the system to not require a fuel injected or carbureted system. It will allow the system to be shut-off and not become flooded with liquid fuel. Although it may be necessary to provide a means of equalizing the pressure in the combustion chamber when the oxygen supply is cut off and the temperature drops. It will pull a vacuum against the check valve.
  • by using the high-pressure oxygen gas input as the circulation flow driver, it automatically delivers heat as it as it is generated. There is also no active pump required

© 2010 Vacca, Inc.