The invention relates to heating a heating fluid by transferring heat energy from a heated liquid to the heating fluid. Particularly, but not exclusively, the invention relates to heating the liquid in a pressure regulated chamber.
In a uranium enrichment facility, a feed station feeds uranium material, such as uranium hexafluoride, into an enrichment apparatus. The uranium material is heated before being fed into the facility.
According to the invention, there is provided a heating apparatus comprising: a heating chamber in which a heater is configured to heat a heating liquid; a heat exchanger configured to receive the heating liquid from the heating chamber and to transfer heat energy from the heating liquid to a separate heating fluid; and a pressure regulator configured to control a pressure inside the heating chamber, wherein the regulator is coupled at a first side to a pressure in the heating chamber and at a second side to atmospheric pressure outside the apparatus.
The pressure regulator may be configured to vent gaseous heating liquid from the heating chamber upon a pressure in the heating chamber reaching a predetermined value.
The pressure regulator may be configured such that a difference between the pressure inside the heating chamber and the atmospheric pressure outside the apparatus causes the pressure regulator to open to vent evaporated gaseous heating liquid from the heating chamber.
The pressure regulator may comprise a seal which is configured to be automatically opened by a pressure differential between the pressure in the heating chamber and the atmospheric pressure outside the apparatus, thereby opening a channel between the heating chamber and the atmosphere outside the apparatus.
The pressure regulator may comprise an inlet open to the heating chamber and an outlet open to atmospheric pressure outside the apparatus.
A difference between the pressure inside the heating chamber and the atmospheric pressure outside the apparatus may cause the liquid heating fluid to flow from the heating chamber through the inlet towards the outlet.
The pressure regulator may comprise a U-bend between the inlet and outlet for containing a body of liquid heating fluid.
The heat exchanger may comprise a heating surface which is thermally coupled to a heating liquid channel to receive heat from the heating liquid.
The heat exchanger may comprise a heating fluid channel configured to direct the heating fluid over the heating surface to receive heat from the heating surface.
The apparatus may comprise a uranium material heating chamber configured to receive heated heating fluid from the heat exchanger and to heat a uranium material container therein
The uranium material heating chamber may be configured to supply cooled heating fluid back to the heat exchanger.
The heating liquid may comprise water.
Evaporation of the heating liquid in the heating chamber may prevent further heating of the heating liquid and heating fluid.
Evaporation of the heating liquid in the heating chamber may lower a surface of the heating liquid below the heater in the chamber and thereby prevent direct contact between the heating liquid and the heater.
According to the invention, there may be provided a method of heating comprising: heating a heating liquid in a heating chamber; receiving the heating liquid in a heat exchanger and transferring heat energy from the heating liquid to a separate heating fluid; and regulating a pressure inside the heating chamber by coupling a pressure in the heating chamber to atmospheric pressure outside the apparatus via a pressure regulator.
For exemplary purposes only, embodiments of the invention are described below with reference to the accompanying figures in which:
An apparatus 1 configured to heat a uranium material container is illustrated in
The apparatus 1 comprises a heating region configured to heat a primary heating fluid 2. The primary heating fluid 2 comprises an evaporable liquid, such as water. As shown in
A temperature sensor 5 is included inside the chamber 3 and is configured to sense the temperature of the liquid primary heating fluid 2 inside the chamber 3. The temperature sensor 5 may be integrated with the heater 4, as shown in
The heating chamber 3 comprises an inlet and an outlet through which the liquid primary heating fluid 2 can respectively enter and exit the heating chamber 3, as described below.
A first aperture 7 comprises an exit through which the liquid primary heating fluid 2 can flow out of the heating chamber 3. As shown in
Still referring to
In order to regulate the flow of liquid primary heating fluid 2, the entrance conduit 13 may be configured to feed the primary heating liquid 2 from the heat exchanger 9 into a heating liquid receiving compartment of the heating chamber 3. The heating liquid receiving compartment is separated from the heater 4 by an internal wall 3d of the chamber 3 so that liquid 2 in the liquid receiving compartment is not substantially heated by the heater 4. In order for the liquid 2 to be heated, it must overflow the internal wall into a larger heating compartment of the chamber 3, in which the heater 4 is present. In terms of its location relative to other components of the apparatus 1, the vertical level of the internal wall 3d may be approximately the same as the vertical level of the heat exchanger 9. In this way the liquid primary heating fluid 2 in the receiving compartment is at approximately the same vertical level as the heat exchanger 9. The two may be arranged so that liquid primary heating fluid 2 in the receiving compartment ensures that the heat exchanger 9 stays filled with liquid primary heating fluid 2 even when the liquid primary heating fluid 2 evaporates in the heating compartment. This is described in more detail further below.
As mentioned previously, the heat exchanger 9 is configured to transfer heat from the liquid primary heating fluid 2 to the secondary heating fluid 10. For example, the heat exchanger 9 may comprise a heating surface 14 which is heated by the liquid primary heating fluid 2 and is exposed to the secondary heating fluid 10 so that heat energy transfers from the heated surface 14 to the secondary heating fluid 10. Referring to
The heating surface 14 may comprise one or more fins and is arranged to be heated by the liquid primary heating fluid 2. For example, the heating surface 14 may be thermally coupled to a primary heating fluid channel 15 through which the liquid primary heating fluid 2 flows through the heat exchanger 9. The heating surface 14 may optionally be heated through direct contact with the liquid primary heating fluid 2 in the channel 15. Alternatively, the heating surface 14 may be otherwise thermally coupled to the heating fluid channel 15 via a heat conductive member in order that heat energy from the liquid primary heating fluid 2 transfers to the heating surface 14. The primary heating fluid channel 15 is continuously fed with liquid primary heating fluid 2 from the heating chamber 3 via the exit conduit 8 previously described, so that the heat exchanger 9 continues to heat the secondary heating fluid 10 with heat energy from the liquid primary fluid 2.
Referring to
As illustrated in
The secondary heating fluid 10 may be directed into the entrance 17 of the secondary heating fluid channel 16 of the heat exchanger 9 from a heating chamber 19 in which the secondary fluid 10 has been used to heat a uranium material container 20 such as a cylinder. For example, as illustrated in
Referring again to
The liquid primary heating fluid 2 re-entering the heating chamber 3 from the heat exchanger 9 may be significantly cooler in temperature than the liquid primary heating fluid 2 exiting the heating chamber 3 through the exit 7, due to the loss of heat energy which takes place in the heat exchanger 9. The temperature difference between the heating liquid 2 entering the heating chamber 3 through the entrance 12 and the desired temperature for heating liquid 2 in the chamber 3 may require the heater 4 to continuously heat the liquid 2 in the chamber 3 in order to maintain the desired temperature. An example of a desired temperature for the liquid primary heating fluid 2 inside the chamber 3 is between approximately forty and eighty degrees Celsius, although other temperatures below the boiling point of the primary heating liquid 2 could also be used.
As indicated previously, the heating power output of the heater 4 is controlled by the control unit 6. The control unit 6 may control the power output of the heater 4 in dependence of temperature measurements received from the temperature sensors 29, 30 in the container heating chamber 19 and the container 20 in order to maintain desired temperatures in the heating chamber 19 and the container 20. The control unit 6 may also control the power output of the heater 4 in dependence of pressure measurements received from the pressure sensor 31 in the container 20 to maintain a desired pressure in the container 20. In addition, the control unit 6 may control the power output of the heater 4 in dependence of measurements received from the sensor 5 indicating the temperature of the liquid primary heating fluid 2 inside the heating chamber 3. For example, the control unit 6 may be configured to compare the pressure and temperature measurements received from the sensors 5, 29, 30, 31 with predetermined threshold values and to reduce or zero the heating power output of the heater 4 if one of the measurements exceeds a threshold value. One or more threshold values may be stored in the control unit 6 for each of the sensors 5, 29, 30, 31. If none of the temperature and pressure measurements received from the sensors 5, 29, 30, 31 exceed the predetermined threshold limits, the control unit 6 may be configured to switch on the heater 4 and/or maintain or increase the heating power output of the heater 4 in order to heat the liquid primary heating fluid 2 and thereby heat the secondary heating fluid 10 and container 20. An example threshold value for the temperature of the secondary fluid 10 in the heating chamber 19, as measured by the sensor 29 therein, is approximately 64 degrees Celsius. An example threshold value for the temperature of the container 20, as measured by the sensor 30 described above, is approximately 53 degrees Celsius. An example threshold value for the pressure in the container 20, as measured by the sensor 31 therein, is approximately 400 mbar. The control unit 6 may be configured to activate the heater 4 to heat the primary heating liquid 2 when all three of these temperature and pressure values are below the threshold values. An example threshold value for the temperature of the liquid primary heating fluid 2, as measured by the sensor 5 in the heating chamber 3, is approximately 80 degrees Celsius. In addition to the three measurements already discussed above, the measurement of the temperature of the liquid primary heating fluid 2 received from the sensor 5 in the heating chamber 3 may be checked against the threshold value by the control unit 6 before the control unit 6 is configured to activate the heater 4. The temperature measurements received from the sensor 5 in the heating chamber 3 may be used by the control unit 6 to keep the temperature of the liquid primary heating fluid 2 below the threshold limit, such as 80° C. All of the threshold values of the temperatures and pressures discussed above may be stored in the control unit 6 so that the control unit 6 can instruct the heater 4 to heat the liquid primary heating fluid 2 accordingly based on feedback from the sensors 5, 29, 30, 31 to maintain the desired temperature and pressure conditions.
The exit conduit 8 may be thermally insulated so that liquid heating fluid 2 flowing from the heating chamber 3 to the heat exchanger 9 does not lose any substantial amount of heat energy in the exit conduit 8. The temperature of the liquid primary heating fluid 2 arriving at the heat exchanger 9 may therefore substantially correspond to the temperature of the liquid heating fluid 2 leaving the heating chamber 3 through the chamber's exit 7.
As previously described, the heating surface 14 in the heat exchanger 9 is heated by the liquid primary heating fluid 2 and therefore its temperature is dependent upon that of the liquid primary heating fluid 2. This means that the temperature of the heating surface 14 does not rise above the temperature of the primary heating liquid 2 in the heat exchanger 9 and therefore the maximum temperature of the heating surface 14 is approximately equal to the boiling point of the primary heating liquid 2 in the heating chamber 3.
The heating chamber 3 in which the liquid primary heating fluid 2 is heated by the heater 4 is coupled via a pressure regulator 21 to the atmospheric pressure outside the chamber 3. The atmospheric pressure may be the natural atmospheric pressure of the Earth in the region of the apparatus 1. An example value of atmospheric pressure is approximately 101 kPa. As described below, the coupling between internal pressure of the heating chamber 3 and the atmospheric pressure outside the apparatus 1 causes the pressure regulator 21 to operate passively to prevent a substantial build-up of pressure in the heating chamber 3 and thereby prevent a substantial increase in the boiling point of the liquid primary heating fluid 2 in the chamber 3.
The pressure regulator 21 may comprise a pipe 22 in which a volume of liquid primary heating fluid 2 is present. As described below, under normal operating conditions of the apparatus 1, the liquid 2 in the pipe 22 seals the pipe 22 and thereby prevents gaseous transfer between the heating chamber 3 and the external atmosphere outside the apparatus 1. A consequence of this is that, under when the temperatures and pressures referred to above are below their threshold values, the liquid primary heating fluid 2 in the pipe 22 substantially prevents gaseous primary heating fluid 2 which has been evaporated from the liquid primary heating fluid 2 in the heating chamber 3 from escaping out of the apparatus 1 into the external atmosphere.
In more detail, referring to
The outlet 24 of the pipe 22 of the pressure regulator 21 is open to the external atmosphere and hence atmospheric pressure outside the apparatus 1. Liquid primary heating fluid 2 is located in between the inlet 23 and the outlet 24, for example in a U-bend of the pipe 22, so that the liquid primary heating fluid 2 seals the inlet 23 of the pressure regulator 21 from the outlet 24 in the manner described above.
Referring again to
If the temperature of the liquid primary heating fluid 2 in the heating chamber 3 increases above the defined upper threshold value referred to above, for example due to a malfunction in the heater 4, temperature sensors 5, 29, 30, pressure sensor 31 or control unit 6, then the rate of evaporation of the liquid primary heating fluid 2 in the chamber 3 increases above the rate which occurs at under normal operation. A consequence is a reduction in the amount of liquid primary heating fluid 2 in the chamber 3 and an increase in the amount of gaseous primary heating fluid 2 in the chamber 3.
As the liquid primary heating fluid 2 evaporates in the chamber 3, the surface of the liquid primary heating fluid 2 drops below the level of the heater 4 and thus the heater 4 ceases to directly heat the liquid primary heating fluid 2. Furthermore, as the volume of gaseous primary heating fluid 2 increases due to evaporation of the liquid heating fluid 2 in the heating chamber 3, the pressure regulator 21 ensures that a significant increase in the internal pressure of the heating chamber 3 is prevented by increasing the volume available for the gaseous primary heating fluid 2 to expand into. The pressure in the heating chamber 3 may primarily be reduced by venting of gaseous primary heating fluid 2 out of the chamber 3 through the further outlet 26 in the manner described above. The pressure in the heating chamber 3 may also be reduced by movement of the primary heating liquid 2 in the pipe 22, as described below.
If the pressure of the heating chamber 3 rises above the atmospheric pressure outside the heating chamber 3, force exerted by the gaseous primary heating fluid 2 against the liquid primary heating fluid 2 in the pipe 22 of the pressure regulator 21 causes the liquid primary heating fluid 2 inside the pipe 22 to move along the pipe 22 away from the inlet 23 and the heating chamber 3. This causes liquid primary heating fluid 2 to flow from the heating chamber 3 into the pipe 22 through the inlet 23 and thereby lowers the surface of the liquid primary heating fluid 2 in the chamber 3. The result is an increase in the volume of the chamber 3 available for the evaporated gaseous primary heating fluid 2 and thus a prevention of any substantial increase of pressure inside the heating chamber 3.
If the surface of the liquid primary heating fluid 2 inside the pipe 22 of the pressure regulator 21 is forced by the gas pressure to the level of the U-bend previously described, then gaseous primary heating fluid 2 evaporated from the liquid primary heating fluid 2 in the heating chamber 3 will begin to escape from the apparatus 1 by rising through the liquid primary heating fluid 2 on the outlet side of the U-bend in the pipe 22. This gaseous primary heating fluid 2 leaves the apparatus 1 and enters the external atmosphere outside the apparatus 1 via the outlet 24 of the pipe 22.
The two pressure regulating parts of the pressure regulator 21, namely the outlet 24 of the pipe 22 and the further outlet 26 act independently of each other. In an example operation, an increase of the pressure inside the heating chamber 3 above the threshold pressure value would initially cause the seal 28 of the further outlet 26 to open and vent gaseous primary heating fluid 2 to the exterior. Subsequently, evaporated heating fluid 2 may escape through the U-bend of the pipe 22. If either part of the pressure regulator 21 were to fail, pressure release in the chamber 3 would still occur via the other part.
For example, the outlet 24 of the pipe 22 of the pressure regulator 21 may be configured to act as a back-up mechanism for releasing pressure from the heating chamber 3 in the event that the further outlet 26 of the pressure regulator 21 fails to do so. The opposite may also be true in the case of failure of the pipe 22.
The pipe 22 may be formed from glass or otherwise transparent material so that the level of liquid primary heating fluid 2 in the pipe 22 can be visually monitored from outside the apparatus 1. If it is observed that the level of liquid 2 on the outlet side of the U-bend in the pipe 22 has risen above the normal level, it indicates that primary liquid heating fluid 2 has been forced along the pipe 22 towards the outlet 24 by a build-up of pressure in the chamber 3. An operator of the apparatus 1 may then choose to manually shut down the heater 4.
Additionally or alternatively, the material from which the pipe 22 is formed may be relatively brittle and/or fragile so that a seismic event such as an earthquake causes the pipe 22 to break and release liquid primary heating fluid 2 from the chamber 3 via the third aperture 25. The release of liquid 2 in this manner may cause the surface of the liquid 2 in the chamber 3 to drop below the heater 4 so that the heater 4 no longer heats the liquid 2. Breakage of the pipe 22 may also allow free gaseous transfer between the external atmosphere and the chamber 3.
As described above, the pressure regulator 21 prevents a substantial increase of pressure inside the heating chamber 3 above the atmospheric pressure outside the chamber 3. In doing so, the pressure regulator 21 prevents the boiling point of the liquid primary heating fluid 2 inside the heating chamber 3 from rising significantly above the boiling point of the liquid 2 at normal atmospheric pressure of approximately 101kPa. Accordingly, even if a malfunction occurs which causes the liquid primary heating fluid 2 inside the heating chamber 2 to boil, the maximum temperature to which the primary heating fluid 2 may heat the heating surface 14 is approximately the boiling temperature of the liquid primary heating fluid 2 at the atmospheric pressure outside the apparatus 1.
To give a specific example, if the primary heating fluid 2 is water, the maximum temperature of the heating surface 14 in the heat exchanger 9 is approximately one hundred degrees Celsius. It follows that the maximum temperature of the secondary heating fluid 10, and uranium material container 19, is also approximately one hundred degrees Celsius. The apparatus 1 therefore prevents the uranium material container 19 from being heated to undesirably high temperatures, even in the case that the apparatus 1 suffers a malfunction.
A method for heating the uranium material container 20 by heating the primary and secondary heating fluids 2, 10 is described below with reference to
In a first step S1 of the method, the heating chamber 3 is partially filled with liquid primary heating fluid 2. The liquid primary heating fluid 2 is referred to below as water 2, but it will be appreciated that alternative evaporable liquid heating fluids 2 could be used and that the method is not limited to the use of water. If water is used, a quantity of olive oil may be added to reduce evaporation. The chamber 3 is filled with water 2 to a level which at least partially submerges the heater 4 in the heating compartment of the chamber 3. Filling of the chamber 3 may be carried out using the fill line previously described. Alternatively, the chamber 3 may be filled by removing a lid of the chamber 3 and re-fixing the lid once the chamber 3 has been filled to the desired level. A drain line may be used if the chamber 3 has to be emptied. Filling of the chamber 3 may also cause water to flow into the pipe 22 through the aperture 25 so that water 2 rests in the U-bend of the pipe 22. As illustrated in
In a second step S2, the heater 4 is activated and begins to heat the water 2 inside the heating chamber 3. The temperature to which the water 2 is heated is regulated by the controller 6 based on temperature and pressure signals received from the sensors 5, 2930, 31 in the heating chambers 3, 19 and container 20 respectively, as previously described.
In a third step S3, the water 2 is circulated from the heating chamber 3 to the heat exchanger 9. The pump 11 may be activated, for example by the controller 6 based on data received from the sensors 29, 30, 31 in the heating chamber 19 and the container 20, to aid this process.
In a fourth step S4, the water 2 from the heating chamber 3 heats the heating surface 14 in the heat exchanger 9. The heating surface 14 may, for example, comprise one or more thermally conductive fins arranged to receive heat from the water 2 via a thermal coupling, as previously described.
In a fifth step S5, the secondary heating fluid 10, which may comprise air, flows over the heating surface 14 and is thereby heated. The secondary heating fluid 10 may optionally be blown over the heating surface 14 by one or more fans in the heat exchanger 9. The heated secondary heating fluid 10 is then directed away from the heat exchanger 9 via a thermally insulated path to heat the uranium material heating chamber 19 and container 20 therein. For example, the secondary heating fluid 10 may be circulated in a continuous manner from an exit of the heat exchanger 9 to an entry of the heat exchanger 9 via the uranium material heating chamber 19.
In a sixth step S6 of the method, the water 2 is caused to exit the heat exchanger 9 and flow back into the liquid receiving compartment of the heating chamber 3.
In a seventh step S7, the water 2 overflows an internal wall 3d of the heating chamber 3 and re-enters the heating compartment of the heating chamber 3. Here, the water is re-heated by the heater 4 before being caused to flow back to the heat exchanger 9 to further heat the secondary heating fluid 10.
As previously described, the pressure regulator 21 acts throughout the heating process to prevent a substantial build up of pressure in the heating chamber 3 and thereby prevent the water 2 from boiling at a temperature substantially above one hundred degrees Celsius, assuming an external atmospheric pressure of 101 kPa. Boiling of the water 2 in the heating chamber 3 causes the water 2 to evaporate to such an extent that the water level falls below the level of the heater 4. This substantially prevents any further heating of the secondary heating fluid 10 in the heat exchanger 9 due to the lack of heated water being circulated in the apparatus 1. As such, the temperature of the uranium material container 20 is prevented from rising to an undesirable level.
The alternatives described above may be used either singly or in combination.
Number | Date | Country | Kind |
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11400055.7 | Nov 2011 | EP | regional |