CA1197426A

CA1197426A - Heat pipe

Info

Publication number: CA1197426A
Application number: CA000435411A
Authority: CA
Inventors: Alan C. Kirby
Original assignee: Individual
Current assignee: Thermon Heating Systems Inc
Priority date: 1983-08-26
Filing date: 1983-08-26
Publication date: 1985-12-03

Abstract

ABSTRACT OF THE DISCLOSURE

An instrument heater for use in cold climates includes a casing divided by a partition into an insulated instrument chamber and a ventilated heat chamber, which contains a catalytic heater, a thermostat connected to a temperature sensor in the instrument chamber for controlling the quantity of propane fed to the heater from a cylinder in the heat chamber, a heat absorption plate against the heater, and a heat conducting pipe extending from the plate into the ins-trument chamber for heating such chamber and the instrument.
Residual heat from the catalytic heater in the heat chamber ensures the flow of propane to the heater in very cold weather.

Description

t3~

This invention relates to a heater and in particular to an instrument heater for use in cold climates.
Instrument heaters including a heater assernbly mounted externally of the instrument for transferring heat to the instrument by conduction are disclosed, for example by Canadian Patent ~o. 999,~97, issued -to H.W. Bage on November 9, 1976, and U.S. Patent No. 4,213,03~, issued to David C. Gross et al on July 15, 1980.
In general, the heating of instrument enclosures in remote locations presents many problems. Systems using bottled gas such as propane with an open flame are subject to outages because of wind, frozen vents or loss of propane vapour pressure.
Most such systems use excessive quantities of fuel, because of the inefficiency of flame type burners and inefficient methods of transferring heat into the instrument enclosure. Other heating methods, such as electrical resistance heatiny result in draining of the sources of elec-trical power, e.g. batteries or solar cells, particularly in arctic or sub-arctic areas where solar energy is quite limited during the winter months.
~0 Heat pipes have been used effectively to transfer ground heat to an ins-trument enclosure. However, such a system is limited by ground heat temperatures, and requires the boring oE holes sufficiently deep to reach stable soil tempera-tures.
The object of the present invention is to overcome the problems described hereinbefore by providing a relatively simple, effective instrument heater, which u-tilizes a fuel such as propane, butane or natural gas.
Accordingly, the present invention relates to an instru-ment heater comprising casing means; partition means dividing said casing means into a substantial:Ly sealed, insula-ted ~t instrument chamber for containing an instrument to be heated and a heat chamber; heater means in said heat chamber; heat conductor means for receiving heat from said heater means extend-ing into said instrument chamber for heating said chamber;
thermostat means in said heat chamber for controlling the heat generated by said heating means; and sensor means extending into said instrument chamber from said thermostat means for actuating said -thermostat means.
The invention will now be described in greater detail with reference to the accompanying drawing, which illustrates a preferred embodiment of the invention, and wherein:
Figure 1 is a partly sectioned perspective view of an instrument heater in accordance with the present invention; and Figure 2 is a partly exploded perspective view of the principal elements of the apparatus of Fig. 1 With reference to the drawing, the heater of the present invention includes a casing generally indicated at 1. The casing 1 is defined by a bottom wall 2, a top wall 3, side walls 4 (one shown) and end walls 5 and 6u A partition 7 ex-tending between the side walls 4 divides the interior of the casing 1 into a heat chamber B and an instrurnent chamber 10.
An instrument package 11 to be heated is housed in the chamber 10 which is substantially totally sealed frorn the environment. For such purpose, insulation 12 is provided on all ! walls of the chamber 10. Wires 13 from the package 11 extend through a hole 15 and a similar hole(not shown) in the end wall 5 of the casing 1. The temperature in the charnber 10 is controlled by an elongated probe or sensing bulb 16 which is connecte~ to a fluid actuated mechanical thermos'ra-t 17 in -the chamber 8 by a capillary tube 18. The bulb 16 is filled with fluid ~or actuating thermostat 17. ~eat is supplied to the chamber 10 by a copper heat pipe 19 containing water or meth-anol. The pipe 19 may also be formed of stainless steel, and ,contain ar~monia or freon as the actuating fluid or heat transEer medium.
The chamber 8 contains a cylinder 20 containlng fuel, e.g. propane. The fuel leaving the cylinder through a valve 21 passes through a pressure regulator 22 and a flexible tube 23 to a flame start valve 24. From the flame start valve 24, the fuel passes through a coupler 25 to the thermostat 17 and finally through an inlet duct 26 to a catalytic heater 27. A
catalyst bed 28 is of the explosion proof type as described in U.S. Patent No. 4,168,945, which issued to A.C. Kirby on September 25, 1979. The use of such a catalyst bed reduces the likelihood of an e~plosion in the heat chamber 8 if there is a fuel leak in such chamber. Thus, a source of fuel such as the cylinder 18 can be located in the same chamber 8 as -the catalytic heater 28.
The heater 27 and the bed 28 are mounted in a generally U-shaped frame 30. The frame 30 includes a base 31 and a pair of arms 33. ~oles 34 in one of the arms 33 permit the mounting of the frame 30 on the partition 7, so that the main elements of the heater are spaced from the bottom wall 2 of the casing 1.
A pair of L-shaped arms 35 extend forwardly from the heater 28 for mounting the heater on the :Erame 30. The arms 35 are slld between plates 36, which extend inwardly from the base 31 and arms 33 of the frame.
A pair of rods 38 connected to one arm 33 of the frame 30 support a copper absorption plate 39, which receives heat from the catalytic heater 27. The hea-t pipe 19 extends through ~'7f~

a hole in one arm 33 of the Erame into the absorption plate 39. A ceramic fiber blanket 4~ insulates the outer surface of the pla-te 39. A vent ~2 is provided in end wall 6 of the casing 1 for ventilating the chamber 8.
In operation, the temperature desired for the instrument package 11 is set on the thermostat 17. The flame start valve 24 has an internal by-pass feature which permits an excess of fuel to pass through the valve for start up purposes. During starting of the heater 27, a by-pass button 44 on -the valve 2 is pressed to allow excess fuel to the heater 27. After -the heater is started, the buttGn ~4 is released, and an internal orifice (not shown) controls the supply of fuel to the thermostat 17 and the heater 27.
The heater 27 is fueled by propane, butane, natural gas or a similar fuel. The infra-red heat generated by the catalytic heater 27 is absorbed by the absorption plate 39.
Heat is transferred to the hea-t pipe 19, and into the instru-ment chamber 10, which, as mentioned, is more or less completely sealed from the atmosphere. Once the temperature in the chamber 10 has reached the desired level, the thermostat 17 ensures that sufficient fuel is fed to the heater to sustain a minimum catalytic reaction only. The heat generated in the chamber 8 by the catalytic heater 27 is usually sufficient to maintain vapour pressure in the fuel cylinder 20, thereby prevent:ing outages because of low ambient tempera-tures.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An instrument heater comprising casing means;
partition means dividing said casing means into a substantially sealed, insulated instrument chamber for containing an instru-ment to be heated and a heat chamber; heater means in said heat chamber; heat conductor means for receiving heat from said heater means extending into said instrument chamber for heating said chamber; thermostat means in said heat chamber for controlling the heat generated by said heating means; and sensor means extending into said instrument chamber from said thermostat means for actuating said thermostat means.

2. An instrument heater according to claim 1, including vent means in said casing means for ventilating said heat chamber; catalytic heater means connected to said thermostat means in said heat chamber for heating said conductor means.

3. An instrument heater according to claim 2, including flame start valve means in said heat chamber for receiving fuel from a source of fuel in said chamber and feeding said fuel to said thermostat means to start said catalytic heater means.

4. An instrument heater according to claim 2, including frame means mounted on said partition means for supporting said catalytic heater means and said thermostat means.

5. An instrument heater according to claim 4, including a heat absorption plate mounted on said frame means for trans-ferring heat from said catalytic heater means to said conductor means.