Thermoelectric Heating And Ventilating Device

Abstract

A self-powered, heating and ventilating device for ventilating the interior f an impermeable garment which utilizes an electrically powered fan to propel heated or ambient air within the garment. The electrical energy is produced by a thermoelectric generator which converts thermal energy, produced by the combustion of a liquid fuel, to electrical energy. The heated air utilized to heat the interior of said garment is obtained from heat rejected by finned elements on the cold side of the generator.

Description

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to a portable, self-powered heating and ventilating device which provides a flow of air to heat or ventilate the interior of an impermeable garment, or suit.

The protection of individuals, exposed to a wide range of hostile environmental conditions, such as temperature extremes or toxic agents, ideally requires complete isolation of the individual from that hostile environment. If the individual is to be unrestrained and mobile, he must be inclosed within a personal protective system which provides the requisite hospitable internal environment. A protective system, which would least interfere with the activity of the wearer, should be a lightweight garment, or suit, which completely incloses the individual and is both liquid and gastight. Lightweight, impermeable garments and protective helmets are available to provide the required isolation and protection, and filter devices are available to remove the toxic agents from air drawn into the internal environment. The heretofore unavailable component for such a protective system has been a lightweight portable device, capable of generating a flow of air to heat or ventilate the interior of the protective clothing system for a reasonable period of time. Substantial quantities of air are required to flow through such impermeable, protective garments to keep the wearer in thermal balance by removing therefrom moisture given off by the body, and excess body heat when operating under high environmental temperatures or by adding needed heated air when operating under low environmental temperatures.

A device capable of supplying a flow of air to heat or ventilate the entire impermeable protective suit or garment must of necessity be portable, i.e., susceptible of being carried about by the wearer, lightweight so as not to unduly fatigue or hinder the activity of the wearer, and selfpowered to maintain a source of power or energy to perform its function for reasonable lengths of time. The device of this invention meets the foregoing requirements while supplying a flow of air of a least 18 c.f.m. at standard temperature and pressure against 4.0 inches water column static pressure. The fan which supplies the flow of air is driven by electrical power generated by a thermoelectric device which converts thermal energy directly into electrical energy. Thermoelectric power generation, referred to as the Seebeck effect, requires a closed circuit containing two dissimilar thermoelectric materials in contact, with the junction of each material maintained at different temperatures. Thermoelectric materials, which are preferably semiconductors, such as bismuth telluride and lead telluride, are of two different types, the "P" type which receives electrons and the "N" type which gives up electrons. Such thermoelectric materials are well known in the art.

The features of this invention will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of the fuel, air and heat flow of the present invention;

FIG. 2 is a view in side elevation of the present invention;

FIG. 3 is a top plan view of the device shown in FIG. 2;

FIG. 4 is a bottom view of the same device;

FIG. 5 is a view partially in section taken along the line 5--5 of FIG. 2;

FIG. 6 is a schematic diagram of the electrical circuit of this invention.

Referring to FIG. 1, there is shown a flow diagram which functionally depicts the fuel flow, combustion, heat flow, and airflow of the system which will be described in detail hereinafter, when the operation of the device is disclosed.

FIG. 2 depicts a preferred embodiment of the heating and ventilating device of this invention wherein the device is inclosed within an outer, rigid, protective shell 10 which can be disassembled to allow access to the components of the device. The source of energy to power the device is a volatile hydrocarbon fuel, such as gasoline or kerosene, which is contained within a fuel reservoir or tank 20. Located at the upper end of the tank 20 is a threadably removable, filler cap 21 which covers the opening through which the fuel is introduced into the tank. A flexible rubber diaphragm 22 divides the fuel tank into two compartments, an upper compartment 23 which contains the fuel and a lower compartment 24 which contains air under pressure. Fuel pressurization is accomplished with a manually operated air pump 25 which pressurizes the air compartment. The rubber diaphragm 22 being a flexible member transmits the pressure within the air compartment to the fuel and maintains the fuel under a substantially constant pressure despite any change in the attitude of the tank. A miniature pressure gage 26 in communication with the air compartment, is provided to monitor the internal pressure of the tank. An air bleed valve 27 contained in the filler cap permits the air to be moved from the fuel compartment after pressurization and a bleed valve 28 within the air compartment relieves the pressure in that compartment prior to refilling.

Fuel flows from the pressurized fuel tank 20 through a fuel metering system which regulates the fuel pressure and meters the fuel flow to the burner 40. As shown in FIG. 2, a hollow fuel tube 30 communicates with and proceeds from the upper compartment 23 of fuel tank 20 and carries the fuel to a high-pressure regulator 31 and then to a low-pressure regulator 32 which is manually adjustable. The two stage pressure regulation system functions to provide a constant fuel flow to the burner. Adjustments are made in the low-pressure regulator to compensate for changes in fuel viscosity to insure a constant fuel flow rate. A shutoff valve 33 is also provided on the fuel line to permit positive fuel shutoff. The fuel then flows through a flexible tube 34 to the burner 40 and the fuel is metered to the burner through a capillary tube (not shown in the drawing) to insure proper fuel metering for the low fuel flow involved (approximately 0.22 lbs. per hr.).

The burner assembly shown in FIGS. 2, 4 and 5 consists of a burner 40, an axial flow blower 41, referred to hereinafter as the generator blower and a swivel base 42, or support. The swivel base allows the burner assembly to be removed away from its operative position against the thermoelectric generator 50 so that the fuel-air mixture may be ignited. The swivel base has a U-shaped configuration with the base being attached to the outer shell and having spaced-apart, upstanding, parallel sides 43 which support the burner assembly. A pair of spaced-apart pins 44 on either side of the assembly are supported in spaced-apart slots 45 on each upstanding side of the swivel base with the slots being configured so as to allow the burner assembly to be directed away from the thermoelectric generator and to be rotated upwardly to facilitate ignition.

The burner is a lightweight, low-pressure multifuel device, such as the burner described in U.S. Pat. No. 3,324,921 to Fox et al. Fuel is fed through the fuel line to the center of the burner where the fuel is absorbed on a feltlike refractory or ceramic wick 46 and transported to the outer periphery of the wick. Air from the generator blower 41 passes through openings in the burner and exits with the fuel as it vaporizes with the wick. Openings at the periphery of the burner allow additional air to mix with the richly burning fuel-air mixture at the wick periphery. A baffle plate 47 located a short distance in front of the wick holds the flame front at the burner head and provides a heat source to hasten vaporization of the fuel. After the burner is ignited and is operating properly, the burner assembly is returned to its position against the thermoelectric generator and is held in place under tension by means of tension springs 48 on either side of the assembly.

The thermoelectric generator 50 consists of 16 individual thermoelectric modules 51 positioned around an octagonal core. Each module consists of 22 "P" and "N" type bismuth telluride and lead telluride pellets which are electrically connected in series. The modules are also connected in series to obtain the required voltage (12 volts). Finned heat exchangers 52 are used to remove heat at the cold side of the modules. Ambient air is forced by the generator blower 41 across the finned heat exchangers to remove heat from the cold side of the thermoelectric modules. This airflow, in picking up heat from the finned heat exchangers, provides the clean, heated, airflow required for the heating function of this device. The generator is inclosed within a cylindrical housing 53 and the upper end of the housing is covered with a circular plate 54 having a plurality spaced-apart openings. A shutter plate 55, rotatably mounted above the circular plate, as shown in FIGS. 3 and 5 has a plurality of similarly spaced openings 56 which may be placed in register in the openings of said circular plate. With the openings in register, the airflow from the modules can be vented to the atmosphere. When the openings are closed, the heated air is forced to travel along a hot air duct 57 to a point where it may be pumped into the impermeable protective garment. The electrical power generated by the thermoelectric generator drives the generator blower, the suit blower 60 and as will be described later, also recharges a battery and provides a source of electrical power which may be utilized for some external requirement.

The hot core of the generator surrounds a cylindrical combustion chamber 58 which is shown in FIG. 5. The heat required by the thermoelectric generator is derived from the hot gases produced by the combustion process which gases flow through a three-pass ducting system, identified as 58, 58' and 58", which minimizes the temperature gradient along the hot core. After passing through the ducting system, the combustion gases are vented through the atmosphere through an exhaust tube 59 shown in FIG. 2.

A centrifugal fan or blower, hereinafter referred to as the suit blower 60, provides the flow of air which is used to ventilate the interior of the impermeable suit. Clean atmospheric air can be taken in directly from an air inlet opening 61 shown in FIG. 4, and propelled by the blower out through an air outlet opening 62. In operation, the air outlet opening would be connected with a flexible conduit (not shown) which would deliver the flow of air to an opening in the suit. When desired, heating air from the cold side of the thermoelectric generator is delivered through a hot air return duct 57 to the suit blower. The temperature of the air delivered to the air outlet opening by the suit blower is controlled manually by means of an air temperature adjustment knob 63. This knob controls by mechanical linkage 68 the shutter valve at the top of the thermoelectric generator and also simultaneously controls a second air valve which controls the air inlet opening. When cool air is required, the valve controlling the air inlet opening is opened permitting atmospheric air to be drawn into the suit blower and simultaneously the shutter valve is opened wide to permit the heated air from the cold side of the generator to pass directly out to the atmosphere. When warmer air is required, the air inlet opening is gradually restricted and the shutter valve simultaneously gradually closed until the proper temperature is achieved. As shown in FIG. 3, control over the shutter opening is achieved by means of thin cords 64 attached to diametrically opposite points on the shutter plate 55 which cords are drawn over spaced-apart pulleys 65 and attached to opposite ends of a pivot bar 67. As the pivot bar is turned in one direction, the cords cause the shutter to rotate in one direction to close the openings and when the pivot bar is turned in the opposite direction, the shutter turns causing the shutter opening to register with the plate openings. A mechanical linkage 68 connects the pivot bar to the shaft 69 bearing the temperature adjustment knob 63 so that by turning the temperature control knob, the mechanical linkage causes the pivot bar to be pivoted upwardly or downwardly, thereby closing the shutter.

The electrical circuits for this invention are shown schematically in FIG. 6. The components in the circuit consist of a three-deck, single-pole switch 70 which controls the various circuits, a rechargeable nickel-cadmium battery 71, a thermoelectric generator 72, a generator blower 73, a suit blower 74, a voltage regulation device consisting of a 13 volt Zener diode 75, and a 75 ohm resistor 76. Each of the three decks has six switch positions which are numbered from one to six in the diagram. In position No. 1, the Off position, only the thermoelectric generator 72 is connected to the generator blower 73 to facilitate cooling of the system during shut down. When set in position No. 2, the Ignition position, the generator blower is energized by the battery at reduced voltage because of the 75 ohm resistor in the circuit. Position No. 3, the Battery-Powered position, the generator blower is energized by the battery at full battery voltage. Position No. 4, referred to as the Self-Powered position, causes the generator blower to be energized by the thermoelectric generator and the excess thermoelectric generator power to be dissipated by the voltage regulating Zener diode. In this position, the battery may also be charged from an external source by connecting said source to the battery terminal 77 and the common negative terminal 78. Position No. 5 on the switch, the Suit Blower position, causes the generator blower and the suit blower to be energized by the thermoelectric generator and the battery to be charged and the voltage regulated by the Zener diode. In position No. 6, the External Load position, power is supplied to external load connection terminals 79 and 78 and to the generator blower by the thermoelectric generator, the battery is charged and the voltage is limited by the Zener diode.

Particular reference is now made to FIG. 1 in connection with the following description of the operation of the present invention. The device is first positioned so that the fuel tank 20 is upright. The air bleed valve 28 is opened to relieve the pressure within the air compartment of the fuel tank. The bleed valve 27 on the filler cap 21 is then opened and air forced within the fuel compartment to cause the diaphragm 22 to be forced to the bottom of the fuel tank. The filler cap is removed and the tank compartment 23 filled with fuel. When the cap has been replaced, both bleed valves are closed and the air compartment is pressurized with the hand pump 25 to 50 p.s.i.g. Air within the fuel compartment is removed by opening the bleed valve in the filler cap and allowing the air to escape and thereafter closing the valve. The manually adjustable low pressure regulator 32 is adjusted to provide the proper fuel flow rate by compensating for changes in fuel viscosity caused by ambient conditions such as temperature, humidity and wind conditions.

The burner assembly is withdrawn from its position against the thermoelectric generator and pivoted upwardly. The Shut-Off valve is opened allowing the fuel to flow to the burner and after an approximately 60 second delay, to permit the fuel to wet the ceramic felt wick, the electrical switch 70 is turned from the Off position to position No. 3, held there momentarily and then turned to position No. 2. The fuel-air mixture at the head of the burner is ignited with a match or lighter. Following ignition, the switch is returned to position No. 3. The air temperature adjustment knob is turned to the extreme cool position and after observing that the burner is operating satisfactorily, the burner assembly is returned to its position against the thermoelectric generator. After operating for several minutes, during which the products of combustion and heating gases flow through and heat the hot core of the thermoelectric generator, the electrical switch is placed on position No. 4 which cuts out the battery and allows the thermoelectric generator to power the generator blower. The generator blower provides air for the burner which ultimately leaves the system as combustion exhaust gases. The generator blower also provides a flow of air which passes across the finned heated exchange generator along the cold side of the thermoelectric modules and is either vented as heated air or is conducted to the suit blower. Heat generated by the burner passes through the three-pass ducting system and heats the hot side of the thermoelectric modules. Some of this heat escapes with the combustion gases and some of the heat flows across the module junctions and is rejected by finned heat exchangers. After several more minutes of operation to allow the thermoelectric generator to come to full power, the switch is advanced to position No. 5 or 6, depending on whether the power is to be used to drive the suit blower or to supply some external requirement. When operating in position No. 5, the air valves are adjusted to obtain the desired amount of heated and ambient air. To shut down the device, the shutoff valve 33 is closed, the switch 70 turned to position No. 1 which allows the generator blower to cool down the device.

The foregoing description has been set forth only to illustrate the principles of the invention. Accordingly, it is desired that the invention be not limited by the embodiment described, but, rather, that it be accorded an interpretation consistent with the scope and spirit of its broad principles.

Claims

WHAT IS CLAIMED IS:

1. A portable self-powered, heating and ventilating device which provides a flow of air to heat or ventilate the interior of an impermeable suit or garment and is adapted to be carried on the back of the wearer, which device comprises

a. a liquid fuel reservoir in which liquid fuel is maintained under a substantially constant pressure despite the attitude of said reservoir,

b. a burner in which said liquid fuel is converted to thermal energy,

c. conduit means connecting said reservoir to said burner and controlling the flow of fuel to said burner,

d. thermoelectric generating means for directly converting thermal energy to electrical power having an inner hot core through which the heated products of combination generated by said burner pass and having an outer cold side,

e. generator air-blower means, electrically powered, for delivering a flow of air through said burner for combustion and for delivering a flow of air to the cold side of the thermoelectric generator to remove heat therefrom,

f. suit blower means, electrically powered, adapted to deliver a flow of air which is drawn from outside of the system or from the airflow which has been heated by the cold side of the thermoelectric generator,

g. an adjustable airflow control means to regulate the desired mixture of the outside air or heated air which is to be delivered to the suit and

h. electrical circuit means to deliver electrical power from said thermoelectric generating means to said generator air blower means and said suit blower means.

2. A portable self-powered, heating and ventilating device according to claim 1 having an auxiliary electrical means and circuit means, to power said generator blower means when said thermoelectric generating means is not operating.

3. A portable self-powered, heating and ventilating device according to claim 2 wherein said auxiliary electrical means is a rechargeable battery and having a rechargeable circuit means to conduct electrical power from said thermoelectric generating means to said battery to recharge said battery.

4. A portable self-powered, heating and ventilating device according to claim 3 having an appropriate switch control means to select the circuit means desired.

5. A portable self-powered, heating and ventilating device according to claim 4 wherein the hot core of the thermoelectric generator has a multipass ducting system through which the hot combustion gases flow which serves to minimize the temperature gradient along the hot core of the thermoelectric generator.

6. A portable self-powered, heating and ventilating device according to claim 5 wherein the cold side of the thermoelectric generator has finned heat exchanges from which heat is removed by the airflow produced by the generator airblower.

7. A portable self-powered, heating and ventilating device according to claim 6 wherein said thermoelectric generator has venting means associated therewith through which the airflow heated by the finned heat exchangers can be vented to the atmosphere and wherein said thermoelectric generator has a duct associated therewith which can carry air heated by the finned heat exchangers to the said suit blower means.

8. A portable self-powered, heating and ventilating device according to claim 7 wherein said thermoelectric generator is a generally cylindrical device having an inner cylindrical heat core.

9. A portable self-powered, heating and ventilating device according to claim 8 wherein said fuel reservoir is divided into two compartments separated by a flexible impermeable membrane, one of which compartments contains the liquid fuel and communicates with said fuel conduit means and the other compartment contains air under pressure.