GB1599279A

GB1599279A - Steam generator

Info

Publication number: GB1599279A
Application number: GB51071/76A
Authority: GB
Original assignee: Babcock International Ltd
Current assignee: Babcock International Ltd
Priority date: 1976-12-07
Filing date: 1976-12-07
Publication date: 1981-09-30

Description

(54) IMPROVEMENTS IN OR RELATING TO STEAM GENERATION (71) We, BABCOCK INTERNATIONAL LIMITED (formerly BABCOCK & WILCOX LIM ITED), a British Company, of Cleveland House, 19, St. James's Square, London SW1Y 4LN, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The use of sodium as the coolant in a nuclear reactor is known. Since the consequences of contact between sodium and water can be serious, it is preferred that water and steam should be heated by the heat in the liquid sodium through the intermediary of a third fluid that might be allowed with less risk to come into contact with either sodium or water.

In a known proposal for the use of the heat in liquid sodium, helium is first heated in heat exchange 'with the sodium and the heated helium is then transferred to a second heat exchanger in which the helium serves to heat water and heat the steam. Since the helium serves to effect the boiling of water, the temperature difference between the helium and the sodium is necessarily small, with the result that the surfaces separating the helium from the sodium must be large.

An object of the present invention is to provide an alternative method of heating water and steam by the heat in liquid sodium, which may have been heated by cooling a nuclear reactor.

According to the present invention, there is provided a method of producing steam by use of the heat in a hot fluid in which, in each of two units, water is supplied to a first flow path, the hot fluid is caused to flow through a second flow path, an intermediate fluid is caused to flow through a fluid flow path so as continuously to abstract heat from the second flow path and give up heat to the first flow path so that steam is generated in the first flow path, the intermediate fluid being circulated in sequence through the third flow paths of the two circuits.

By way of example, an embodiment of the invention will now be described with reference to the accompanying drawing in which Figure 1 illustrates, somewhat diagrammatically, a heat exchanger, and Figure 2 is a diagram illustrating the temperature changes in each of the units of the heat exchanger illustrated in Figure 1.

The heat exchanger illustrated in Figure 1 includes two units A and B. The units are generally similar to each other and each includes helical tubes defining a first flow path 1 and further helical tubes defining a second flow path 2. The tubes are disposed within a drum 3 defining a third flow path.

The third flow paths of the two units are connected by the ducts 4 and 5, the latter including a circulator pump 6.

In use, the liquid sodium that has been heated as the coolant in a nuclear reactor is passed through the flow path 2. Water is supplied to the flow path 1 and steam is generated from the water in the flow path by the heat supplied by the sodium. To transfer the heat, helium is used as an intermediate fluid; helium flows through the drum 3 continuously abstracting heat from the flow path 2 and supplying it to the flow path 1.

The helium flows alternately through the drums 3 of the units A and B. It will be noticed that in each unit, the water and the sodium flow in countercurrent, whilst the helium is introduced into the third flow path of one unit (2) near the hotter end of the sodium flow path and then pumped into the third flow path of the other unit (I) at a location near to the cooler end of the sodium flow path of that unit.

To facilitate the exchange of heat, convolutions of one flow path alternate with convolutions of the other flow path. The temperature changes along the flow paths are indicated approximately in Figure 2.

In an alternative to the units shown in Figure 1, each unit is formed from three tubes extending one within the other, preferably concentrically. Water is introduced into the central tube, helium into the annular space between that and the second tube, and sodium into the space between the second tube and the outer tube, WHAT WE CLAIM IS:

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. (54) IMPROVEMENTS IN OR RELATING TO STEAM GENERATION (71) We, BABCOCK INTERNATIONAL LIMITED (formerly BABCOCK & WILCOX LIM ITED), a British Company, of Cleveland House, 19, St. James's Square, London SW1Y 4LN, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The use of sodium as the coolant in a nuclear reactor is known. Since the consequences of contact between sodium and water can be serious, it is preferred that water and steam should be heated by the heat in the liquid sodium through the intermediary of a third fluid that might be allowed with less risk to come into contact with either sodium or water. In a known proposal for the use of the heat in liquid sodium, helium is first heated in heat exchange 'with the sodium and the heated helium is then transferred to a second heat exchanger in which the helium serves to heat water and heat the steam. Since the helium serves to effect the boiling of water, the temperature difference between the helium and the sodium is necessarily small, with the result that the surfaces separating the helium from the sodium must be large. An object of the present invention is to provide an alternative method of heating water and steam by the heat in liquid sodium, which may have been heated by cooling a nuclear reactor. According to the present invention, there is provided a method of producing steam by use of the heat in a hot fluid in which, in each of two units, water is supplied to a first flow path, the hot fluid is caused to flow through a second flow path, an intermediate fluid is caused to flow through a fluid flow path so as continuously to abstract heat from the second flow path and give up heat to the first flow path so that steam is generated in the first flow path, the intermediate fluid being circulated in sequence through the third flow paths of the two circuits. By way of example, an embodiment of the invention will now be described with reference to the accompanying drawing in which Figure 1 illustrates, somewhat diagrammatically, a heat exchanger, and Figure 2 is a diagram illustrating the temperature changes in each of the units of the heat exchanger illustrated in Figure 1. The heat exchanger illustrated in Figure 1 includes two units A and B. The units are generally similar to each other and each includes helical tubes defining a first flow path 1 and further helical tubes defining a second flow path 2. The tubes are disposed within a drum 3 defining a third flow path. The third flow paths of the two units are connected by the ducts 4 and 5, the latter including a circulator pump 6. In use, the liquid sodium that has been heated as the coolant in a nuclear reactor is passed through the flow path 2. Water is supplied to the flow path 1 and steam is generated from the water in the flow path by the heat supplied by the sodium. To transfer the heat, helium is used as an intermediate fluid; helium flows through the drum 3 continuously abstracting heat from the flow path 2 and supplying it to the flow path 1. The helium flows alternately through the drums 3 of the units A and B. It will be noticed that in each unit, the water and the sodium flow in countercurrent, whilst the helium is introduced into the third flow path of one unit (2) near the hotter end of the sodium flow path and then pumped into the third flow path of the other unit (I) at a location near to the cooler end of the sodium flow path of that unit. To facilitate the exchange of heat, convolutions of one flow path alternate with convolutions of the other flow path. The temperature changes along the flow paths are indicated approximately in Figure 2. In an alternative to the units shown in Figure 1, each unit is formed from three tubes extending one within the other, preferably concentrically. Water is introduced into the central tube, helium into the annular space between that and the second tube, and sodium into the space between the second tube and the outer tube, WHAT WE CLAIM IS:

1. A method of producing steam by use of the heat in a hot fluid in which, in each of two units, water is supplied to a first flow path, the hot fluid is caused to flow through a second flow path, an intermediate fluid is caused to flow through a third flow path so as continuously to abstract heat from the second flow path and give up heat to the first flow path so that steam is generated in the first flow path, the intermediate fluid being circulated in sequence through the third flow path of the two units.

2. A method as claimed in Claim 1 in which the hot fluid flowing through each of the second flow paths is liquid sodium.

3. A method as claimed in Claim 2 in which the intermediate fluid is helium.

4. A method as claimed in any of the preceding claims in which one flow path is provided by the space within a tube, a further flow path is provided by an annulus defined by that tube and a further tube, and the further tube forms a boundary of the other of the flow paths.

5. A method as claimed in claim 4 in which water is introduced into the tube and the intermediate fluid is caused to flow along the annulus.

6. A method of producing steam substantially as described with reference to, and as illustrated by, the accompanying drawing.