GB2040148A

GB2040148A - Heating apparatus

Info

Publication number: GB2040148A
Application number: GB7926234A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-04-29
Filing date: 1979-07-27
Publication date: 1980-08-20

Abstract

A liquid is heated by being in contact with a solid state device, such as a transistor, and its load. A suitable circuit is shown in Fig. 1 where the current through a transistor 1 is controlled by a potentiometer 5, 6. The control may be retroactive, feedback being provided by an elastic membrane 14, Fig. 2, which closes a vessel 11 in which the liquid 12 is contained. Movement of the membrane displaces the body of the potentiometer relative to its slider, which is set at the desired set point. <IMAGE>

Description

SPECIFICATION Heat generating apparatus This invention relates to heat generating apparatus.

According to this invention there is provided heat generating apparatus comprising a solid state electrical device in direct contact with a liquid, whereby when the device is energised it generates heat which heats the liquid.

The device could be a transistor.

The device could be provided with a load which is in direct contact with the liquid, whereby when the load is energised it generates heat which heats the liquid.

The apparatus could include control means for controlling the energisation of the solid state device.

The apparatus could include extendible means which extends as a result of heating the liquid.

Such extendible means could be coupled with such control means, for controlling the energisation of the solid state device as a function of the extension of the extendible means.

Examples of the invention will now be described with reference to the accompanying drawings, in which the same reference numerals indicate the same items in the different figures.

Figure 1 shows a basic circuit diagram where a solid state device 1 (in this case a transistor) is connected to an electrical supply at terminals 2, where a switch 3 of some type is incorporated. A load resistor 4 is connected to the collector of the transistor 1, and a potentiometer 5 is connected to the base of the transistor 1 by way of its slider 6. The transistor 1 and the load resistor 4 are arranged whereby they together form a heating device in apparatus in which the material which is heated (directly) is a liquid, for example water, liquid ammonia, freon, liquid nitrogen, liquid propane or any gas in a liquid state.

The broken outline 7 illustrates the thermal generative boundary of the arrangement. Additionally, if desired, the boundary 7 may be modified to include the potentiometer 5, as shown by the broken outline 8. In its simplest form, the apparatus operates in the following way. Closure of the switch 3 causes the transistor 1 and the load resistor 4 to generate heat which is dependent on the position of the slider 6 and is due to, and proportional to, the power being dissipated by the transistor 1 and the load resistor4 (and in addition the potentiometer 5 in the case of the thermal boundary 8). Liquid existing within the thermal boundary7 or8 as the case may be will undergo a temperature elevation due to heat generated.At the same time, the liquid will perform the function of a heat sinking medium forthe devices which are in contact with it, namely the transistor 1 and the load resistor 4 and, in the case of the thermal boundary 8, the potentiometer 5. Such an arrangement, which might be open to atmosphere, could be made to cause the liquid to boil. In the case of water, this would in general occur at 1000C and this temperature, i.e. 100"C, would thereafter remain constant.

This temperature therefore represents the upper temperature limit of the heating apparatus. The junction temperatures of solid state devices in general have a maximum operating capability (T max) in excess of 100"C. The dynamic operation of the slider 6 along the potentiometer 5 in the direction of the arrow 9 results in positive feed-back to the transistor 1 which will generate relatively more power.

Dynamic operation of the slider 6 in the direction of the arrow 10 results in negative feed-back to the transistor 1, reducing the power generated by the arrangement in a direction towards cut-off. Therefore, manual operation of the slider 6 results in an arrangement which functions as manually controlled heating apparatus of high efficiency (no heat dumping in the controlling system) where, and at the same time, the transistor is liquid cooled and where, generally, the arrangement stablises itself (in terms of the definition of a heat sink) at 100"C in the case of water as the liquid. Other solid state devices could be used instead of a transistor, for example a silicon controlled rectifier, the circuit arrangement of Figure 1 being modified accordingly.Additionally, the load resistor 2 could be replaced by a different load, for example a temperature dependent resistor. Also, the potentiometer 5 could be replaced by another device, for example a temperature dependent resistor, a thermistor or any of a long list of devices which will provide dynamic control signals to whatever component(s) is/are being utilised within the thermal generative boundary 7 or 8 or outside the boundary 7 or8 as appropriate. Such control devices may have inputs which are derived from pressure, temperature, mechanical displacement, humidity, etc., or any combination of the foregoing with which the control device may react allowing the desired result, whatever this may be, to be achieved.

Figure 2 shows a cross-section of a practical form of apparatus generally according to Figure 1. Inside a container 11, which may be fabricated from metal, plastics or other suitable material, is the transistor 1 and the load resistor4 and a relatively small quantity of liquid 12, for example water, the circuit diagram being similar to that of Figure 1 except that the connections to the potentiometer 5 are reversed (see Figure 12), the switch 3 has been eliminated and the circuit diagram has been drawn about the container 11 for simplicity. Electrical connections are brought out of the container 11 at sealed openings 13. A diaphragm 14, for example of polythene, is attached by welding to the container 11, sealing its interior from atmosphere.The potentiometer 5 is operated buy a mechanical connection 15 to the diaphragm 14, the connection 15 being attached to the slider 6 which, in the position of the diaphragm shown, is at a datum reference point. The space 16 above the liquid 12 contains (in this instance) air at atmospheric pressure. Assuming the transistor 1 is conducting at the setting of the potentiometer 5 as shown, heat will be dissipated into the liquid 12 causing a thermal and pressure elevation in the space 16 due to the temperature elevation of the liquid 12 and locally generated vapour at the interface between the transistor 1 and the load resistor 4 and the liquid 12.The diaphragm 14 will take up a position similar two that shown in Figure 3 and which is dependent upon (generally): a) the characteristics of the diaphragm 14; b) the power curve characteristics of the arrangement comprising 1, 4, 5; and c) the thermal leakage characteristics of the apparatus. By reference to Figure 12, it will be clearthatthe direction of movement of the slider 6 will be in the direction shown by the arrow 17 in Figure 12, which direction is towards earch, i.e. progressively biasing the transistor towards cut-off until, at some point of equilibrium, it will remain until the electrical supply is interrupted.The apparatus of Figure 2 may be thermally insulated from the surrounding environment Figure 3 illustrates part of apparatus similar two that of Figure 2 except that the potentiometer 5 is contained within the thermal generative area (as indicated by 8 in Figure 1), the slider 6 being attached to the inner face of the diaphragm 14. The advantages of the apparatus are: a) the reduction in the number of external components; and b) the power dissipated by the potentiometer by heat, though small by comparison, is added to that which it is controlling and not lost to the surroundings, as would be the case with an externally mounted potentiometer, so that the efficiency is greater. For the sake of simplicity, electrical interconnections have been omitted from Figure 3.

In the apparatus shown in Figure 4 (in which, for the sake of simplicity, the transistor 1, the load resistor4 and electrical interconnections have been omitted), a vacuum normally exists above the liquid 12, whereby atmospheric pressure causes diaphragm 14to be pressed inwards, the diaphragm 14 having a greater possible length of travel than in apparatus according to Figure 2 or Figure 3.

Figure 5 shows in cross-section part of one of many examples where the transistor 1 and the load resistor4 (indicated together by reference numeral 18) are themselves mounted on a diaphragm 19, resulting in a sealed chamber between the diaphragm 19 and the diaphragm 14 containing the liquid 12 and the space 16. The diaphragm 14 could be replaced by a rigid member. The effects of operating this apparatus should be clear from the previous description. In an example where the diaphragm 14 is replaced by a rigid member, then the air in the chamber (20) below the diaphragm 19 would be compressed. Figure 6 shows how such compressed air could be utilised, namely by way of a vent 22, reference numeral 21 indicating a rigid member replacing the diaphragm 14.It will be noted that, in Figures 5 and 6, the potentiometer and its slider and electrical interconnections have been omitted for the sake of simplicity, but possible dispositions for them will be apparent by way of Figures 2,3 and 4.

In the apparatus of each of Figures 2 to 6, a modification could be made whereby the transistor 1 and the load resistor4 are separated by a liquid- and gas-tight partition or membrane. Such an arrangement would result in differential pressure, temperature, etc. characteristics in respect of the chambers formed thereby, i.e. the chamber containing the transistor would have a different set of characteristics from the chamber containing the load resistor due to their different power sharing natures when operated together.

Referring nowto Figures7to 10, there will be described forms of apparatus which may operate irrespective of orientation, the liquid interface about the transistor and load resistor being maintained by their being received in an absorbent material, for example sponge, felt or cotton, which is saturated with the liquid. Figure 7 illustrates a form of such apparatus corresponding to the apparatus of Figure 2, reference numeral 23 indicating the absorbent material. The apparatus of Figure 8 corresponds with that of Figure 7 except that the absorbent material extends underneath the diaphragm 14.The apparatus of Figure 8 could be modified so that the under-side of the container 11 is replaced by a further diaphragm so that, on heating, a doubledisplacement occurs, as shown by Figure 9 in which reference numeral 14a indicates the second diaphragm. The apparatus of Figure 9 could be modified so that a vacuum exists in the chamber defined by the absorbent material 23 so that, in the absence of heating, the absorbent material takes up the shape shown in Figure 10 so that the possible displacement range is increased as compared with the apparatus of Figure 9. In Figures 7 to 10, the potentiometer 5 and electrical interconnections have been omitted for the sake of simplicity, but their possible dispositions will be apparent from the previous description.

In the forms of apparatus so far described the function of the or each diaphragm could be taken over by a bellows or other long stroke structure, for example a piston.

Figure 11 illustrates one form the potentiometer 5 may have, namely a resistive portion 25 earthed at each end with a tap 24 taken to the voltage supply.

Figure 13 illustrates a cross-section of part of one example of apparatus according to the invention where (other features apart) a vacuum may be generated as opposed to an increase in pressure as previously described. A container 26 has three ports 27, 28 and 29 and is divided by a partition 30. A mechanical linkage 31, which is liquid-and gas-tight, is capable of dynamic displacement through the partition 30, for example through a small diaphragm or sleeve seal. A diaphragm 32 divides the chamber above the partition 30 into two additional chambers 33 and 34 and the chamber below the partition 30 is also divided into two chambers, 36 and 37, by a diaphragm 35. Within a chamber 36 there is absorbent material saturated with a liquid, for example water, a solid state device 38, in the example a transistor, and a load resistor 39. Therefore, expansion in chamber 36 due to heat dissipated by the transistor 38 and the load resistor 39 causes an increase in pressure in thechamber 37 which is available via the port 29. The linkage 31 causes the diaphragm 32 to distort in sympathy, which causes an increase in pressure in the chamber 34 which is available through the port 28. A valve 40 is disposed in the port 27 and if this valve is shut, then a partial vacuum will be produced in the chamber 33 due to distortion of the diaphragm 32 downwards. If the valve 40 is open, air will be sucked in through the port 27. For higher power operation, the differential chamber principle previously discussed would be useful, i.e. the transistor 38 could be arranged to be at a lower pressure and temperature than the load resistor 39, which resistor could be tolerant to very high temperatures and pressures.Again, in this example one or more of the diaphragms could be replaced by a piston or other long stroke device. Figure 14 shows a cross-section through part of apparatus which corresponds to that of Figure 13 except that an additional port 41 is provided for the chamber 36. This port is controlled by a valve 42 which is operated in some manner, for example electromagneticaliy. Connected to the port 41 is a chamber 43 which, for example, is capable of undergoing expansion, for example a polythene bag. The valve 42 is normally open, i.e. open in the absence of power supplied to it. This valve could be connected to the same electrical supply as the heating system. Therefore, upon switching power to the heating system, in addition to heat being produced, the valve 42 would close and the system would operate as previously described.However, by interrupting the power supply either automatically or manually, the valve 42 would open. The pressure existing in the chamber 36 would thereby be applied to the chamber 43 which would then expand, allowing the diaphragms 32 and 35 to return to their states or rest. The internal surface of the chamber 43 could be at ambient temperature, causing condensation of any vapour coming into it. This condensation would be returned, for example by gravity, to the absorbent material in chamber 36. The apparatus of Figure 14 can therefore be seen to be capable of cycling without exhausting to atmosphere. One way of applying a polythene bag around such apparatus is shown in Figure 15 where the apparatus is denoted by reference numeral 44 and the bag by reference numeral 45. In Figures 13 and 14 forthe sake of simplicity, a potentiometer for control purposes and the electrical interconnections have not been shown, but possible dispositions for them will be apparent from the foregoing description.

In the examples described, the transistor and its load resistor could be mounted on a metallic heat sink which is also in direct contact with the liquid.

Finally, the present invention may be applied to the various forms of apparatus described in and claimed by my co-pending Patent Application filed under reference HL 19555 and also claiming priority from my United Kingdom Patent Application No.

17159/78.

Claims

CLAIMS 1. Heat generating apparatus comprising a solid state electrical device in direct contact with a liquid, whereby when the device is energised it generates heat which heats the liquid. 2. Apparatus according to claim 1, wherein the device is a transistor. 3. Apparatus according to claim 1 or 2, wherein the device is provided with a load which is in direct contact with the liquid, whereby when the load is energised it generates heat which heats the liquid. 4. Apparatus according to claim 3, wherein the load is a load resistor. 5. Apparatus according to any preceding claim, including extendible means which extends as a result of heating the liquid. 6. Apparatus according to claim 5, wherein the extendible means comprises at least one diaphragm. 7. Apparatus according to any preceding claim, including control means for controlling the energisation of the solid state device. 8. Apparatus according to claim 7, wherein the control means is a potentiometer. 9. Apparatus according to claim 7 or 8, wherein the control means is in direct contact with the liquid, whereby heat generated by it heats the liquid. 10. Apparatus according to any of claims 7 to 9 as dependent on either of claims 5 and 6, wherein the extendible means is coupled with the control means, for controlling the energisation of the solid state device as a function of the extension of the extendible means. 11. Apparatus according to any preceding claim, wherein the device is immersed in the liquid. 12. Apparatus according to any of claims 1 to 10, wherein the solid state device is received by absorbent material, which material is saturated with the said liquid. 13. Heat generating apparatus, substantially in accordance with any example herein described with reference to the accompanying drawings. New claims or amendments to claims filed on 6-8-79. Superseded claims :- All. New or amended claims:

1. Heat generating apparatus comprising a solid state electrical device and a load in direct contact with a liquid, whereby when the device is energised it generates heat which heats the liquid.

2. Apparatus according to claim 1, wherein the solid state electrical device is a transistor.

3. Apparatus according to claim 1 or 2, wherein the load is a resistor.

4. Apparatus according to claim 1 wherein the heating means are provided with a metallic heat sink which is also in contact with the liquid, whereby when the heating means is energised it generates heat, which heats the metallic heat sink which together heat the liquid.

5. Apparatus according to any preceding claim, including extendible means which extends as a result of heating the liquid.

6. Apparatus according to claim 5, wherein the extendible means comprises at least one diaphragm.

7. Apparatus according to any preceding claim, including control means for controlling the energisation of the solid state device.

8. Apparatus according to claim 7, wherein the control means is a potentiometer.

9. Apparatus according to claim 7 or 8, wherein the control means is in direct contact with the liquid, whereby heat generated by it heats the liquid.

10. Apparatus according to any of claims 7 to 9 as dependent on either of claims 5 and 6, wherein the extendible means is coupled with the control means, for controlling the energisation of the solid state device as a function of the extension of the extendible means.

11. Apparatus according to any preceding claim, wherein the heating means is immersed in the liquid.

12. Apparatus according to any of claims 1 to 10, wherein the heating means is received by absorbent material, which material is saturated with the said liquid.

13. Apparatus according to claim 7 or 8 wherein the controlling means is a potentiometer incorporating a fixed electrical tapping point into the resistive material, sub-dividing the resistive material wherein the tapping point becomes electrically common.

14. Heat generating apparatus, substantially in accordance with any example herein described with reference to the accompanying drawings.

15. Apparatus according to claim 14 wherein the solid state electrical device is positioned other than in the liquid controlled by the controlling means.