GB1570028A

GB1570028A - Scraped-surface heat exchanger

Info

Publication number: GB1570028A
Application number: GB82379A
Authority: GB
Original assignee: A Johnson and Co London Ltd
Current assignee: A Johnson and Co London Ltd
Priority date: 1977-12-16
Filing date: 1977-12-16
Publication date: 1980-06-25

Description

(54) A SCRAPED-SURFACE HEAT EXCHANGER (71) We, A. JOHNSON AND COM PANY (LONDON) LIMITED, a British company, of Villiers House, 41-47 Strand, London, WC2N SLE, 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:: According to one aspect of the invention, there is provided a scraped-surface heat exchanger for treating a fluid material comprising a stator surrounding a rotor, the stator comprising a plurality of annular projections extending inwardly towards the axis of rotation of the rotor and dividing the space within the stator into a plurality of annular spaces which communicate with one another at locations radially inwardly of the tips of the projections, the rotor carrying scraping means comprising, in each annular space between two adjacent projections, at least one scraper blade which scrapes the whole of one flank of one projection and the whole of the opposite flank of the other projection, whereby some of the material is scraped off the projections as the rotor rotates and is mixed with the remainder of the material.

According to another aspect of the invention, there is provided a scraped-surface heat exchanger for treating a fluid material comprising a stator surrounding a rotor, the stator comprising a plurality of annular projections extending inwardly towards the axis of rotation of the rotor and the rotor carrying scraper means comprising, in each annular space between two adjacent projections, scraping means which scrape the whole of one flank of one projection, the whole of the opposite flank of the other projection, the part of the stator between the roots of the projections and half of the tip of each of the projections whereby some of the material is scraped off the projections as the rotor rotates and is mixed with the remainder of the material.

The scrapers may press against the flanks as a result of the scrapers possessing resilience and/or as a result of the pressure of the fluid material and/or by springs. They could be pivotally mounted on vanes projecting from the rotor.

The heat exchange could be effected with gas or liquid heat exchange medium flowing through the stator, for example along it in the same direction as, or in counter-current with, a fluid material to be heated or cooled which flows along the rotor between the rotor and the stator.

The projections preferably taper, proceeding towards the axis of rotation of the rotor, and they are preferably hollow, the spaces within them being for one of the two fluids involved in the heat exchange. Thus the projections could be of sheet material.

The spaces within them could communicate with one another at their extremities remote from the rotor, so that the above-mentioned gas or liquid can flow into and out of them, from one to another along the stator. Preferably, the connections between the spaces within adjacent projections are staggered circumferentially so that the gas or liquid entering the space within one projection has to flow part of the way around the axis of rotation of the rotor before it can leave that space and flow into the space within the next projection. The space within each projection could be divided into two or more parts, for example by virtue of each projection being made up of two or more segments distributed around the axis of rotation of the rotor. The two flanks of each projection or of each segment of each projection could also be provided by separate members.

The two flanks of each projection could be planar, the planes being substantially perpendicular to the axis of rotation of the rotor.

Alternatively, each projection could have a first flank which is the upper flank when the heat exchanger is positioned with the axis of rotation of the rotor vertical and which then slopes downwardly, proceeding towards said axis. The above-mentioned first flanks and the opposite flanks of the projections are referred to below as upper flanks and lower flanks, respectively, but that does not mean that the heat exchanger necessarily operates with the axis of rotation of the rotor vertical, or, if it is vertical, with the first flanks uppermost. The lower flanks of the projections preferably slope downwardly, proceeding away from said axis. The greater part of each upper flank and/or each lower flank could be planar.Alternatively, the greater part of each upper flank and/or each lower flank could be concavely or convexly rounded in order to give the projections greater strength if they are of sheet material. It is highly desirable so to construct the stator that when the heat exchanger is positioned with the upper flanks of the projections uppermost and the axis of the stator vertical, liquids of low viscosity in the space within the stator, for example low-viscosity liquids used in the heat exchange or low-viscosity liquids for cleaning the heat exchanger after use, will drain completely from the stator and will not, for example, form pools on the upper flanks of the projections.

Whether the two flanks of each projection lie in planes which are substantially perpendicular to the axis of rotation of the rotor or at least the upper flanks are sloping as described above, the tips of the projections could be convexly rounded. There could be, alternatively or additionally, concave rounding between the roots of adjacent projections. The blades may be of plastics material and may be held in slots in plates, for example circular plates, mounted on the rotor and co-axial with it.

The stator may comprise a stack of annular parts each of which provides only one of the projections.

An example in accordance with the invention is described below with reference to the accompanying drawings, in which: Figure 1 shows a side view of a rotary scraped-surface heat exchanger, in section, Figure 2 shows a plan view of a disc on the rotor of the heat exchanger, and Figure 3 shows a scraper mounted on the disc.

The heat exchanger shown in Figures 1 to 3 operates with its rotor 1 rotating about a vertical axis 2. The rotor is preferably of stainless steel and is of regular hexagonal cross-section over the greater part of its length and along that part are regularly distributed circular discs 3, the faces of which are perpendicular to the axis 2. The discs have regular hexagonal holes 4 through them at their centres and they are formed with radial slots 5.

A stator surrounding the rotor comprises a stack of similar annular members 6 (there will usually be more than the three shown) held between flanges 7 and 8 of a housing by bolts 9 provided with nuts 10. Each annular member comprises a collar 6A and a sheet metal part 6B, preferably stainless steel, which affords an annular projection extending inwardly towards the axis 2. The upper flank 6C of each projection is slightly concave but over the whole of its length it slopes downwardly, proceeding towards the axis 2, so that pools of low-viscosity liquid cannot remain on the flanks 6C of the projections when it is desired to drain the heat exchanger with the axis of the stator, which is the axis 2, vertical. The lower flank 6D of each projection is also slightly concave and over the whole of its length slopes downwardly, proceeding away from the axis 2.

The tip 6E of each projection is convexly rounded and there is concave rounding at 6F between the roots of adjacent projections. Seals 11 between the collars 6A and between the end collars and the flanges 7 and 8 are compressed by the bolts 9 and nuts 10. The collars are formed with bosses 12 formed with screw-threaded holes 13 to receive connections for supplying heatexchange fluid to and taking it from hollows 14 within the projections 6B.

Each slot 5 receives a plastics scraper blade 15 which, when free from stress, is flat and wider than the space between the lower flank 6D of one projection 6B and the upper flank 6C of the next. The scraper blades are forced into arcuate form as shown in Figure 3. Each blade has sharp edges which scrape the whole of one flank 6D, one flank 6C and one concavely rounded part 6F and halves of each of two projection tips 6E. The blades have holes 16 through them.

Fluids which are to be in heat-exchange relationship are pumped along the heat exchanger, for example in counter-current, in one case through the hollows 14 in turn and in the other case in through or out of a connection 17 at the lower end of the housing, through the space between stator and rotor and out of or in through the upper end of the housing and being continually scraped off all points on the projections 6B.

In the example shown in the drawings, material scraped off the stator by the blades mixes with the remainder of the material which travels along the space between stator and rotor.

The scraped-surface heat exchanger described above and shown in Figures 1 to 3 of the accompanying drawings is also described, illustrated and claimed in our co-pending Patent Application No.

7716/77 (Serial No. 1570027).

WHAT WE CLAIM IS: 1. A scraped-surface heat exchanger for treating a fluid material comprising a stator surrounding a rotor, the stator comprising a plurality of annular projections extending inwardly towards the axis of rotation of the rotor and dividing the space within the stator into a plurality of annular spaces which communicate with one another at locations radially inwardly of the tips of the projections, the rotor carrying scraping means comprising, in each annular space between two adjacent projections, at least one scraper blade which scrapes the whole of one flank of one projection and the whole of the opposite flank of the other projection whereby some of the material is scraped off the projections as the rotor rotates and is mixed with the remainder of the material.

2. A scraped-surface heat exchanger for treating a fluid material comprising a stator surrounding a rotor. the stator comprising a plurality of annular projections extending inwardly towards the axis of rotation of the rotor and the rotor carrying scraper means comprising, in each annular space between two adjacent projections, scraping means which scrape the whole of one flank of one projection, the whole of the opposite flank of the other projection, the part of the stator between the roots of the projections and half of the tip of each of the projections whereby some of the material is scraped off the projections as the rotor rotates and is mixed with the remainder of the material.

3. A heat exchanger according to claim 1 or 2, a first flank of each projection, which is the upper flank when the heat exchanger is appropriately positioned, with the axis of rotation of the rotor vertical, sloping downwardly, proceeding towards said axis when the heat exchanger is so positioned.

4. A heat exchanger according to claim 1 or 2 in which the flanks of each of the projections are substantially perpendicular to the axis of rotation of the rotor.

5. A heat exchanger according to any preceding claim in which the projections are hollow, the spaces within them being for one of the two fluids involved in the heat exchange.

6. A heat exchanger according to claim 5 in which the projections are of sheet material.

7. A heat exchanger according to claim 5 or 6 in which the spaces within the projections communicate with one another at their extremities remote from the rotor, so that said one of the fluids can flow into and out of them, from one to another along the stator.

8. A heat exchanger according to claim 7 in which the connections between the spaces within adjacent projections are staggered circumferentially so that said one of the fluids entering the space within one projection has to flow part of the way around the axis of rotation of the rotor before it can leave that space and flow into the space within the next projection.

9. A heat exchanger according to claim 8 in which the space within each projection is divided into a plurality of parts.

10. A heat exchanger according to claim 9 in which the division is effected by each projection being made up of two or more segments distributed around the axis of rotation of the rotor.

11. A heat exchanger according to any preceding claim in which the two flanks of each projection are provided by separate members.

12. A heat exchanger according to claim 10 in which the two flanks of each segment of each projection are provided by separate members.

13. A heat exchanger according to any one of claims 1 to 3 in which the projections taper, proceeding towards the axis of rotation of the rotor.

14. A heat exchanger according to claim 3 or any subsequent claim appended to claim 3 in which said opposite flanks of the projections slope downwardly, proceeding away from said axis.

15. A heat exchanger according to claim 3 or any subsequent claim appended to claim 3 in which the greater part of each upper flank is concavely rounded.

16. A heat exchanger according to claim 3 or any subsequent claim appended to claim 3 in which the greater part of each said opposite flank is concavely rounded.

17. A heat exchanger according to any preceding claim in which the tips of the projections are convexly rounded.

18. A heat exchanger according to any preceding claim in which there is concave rounding between the tips of adjacent projections.

19. A heat exchanger according to any preceding claim in which the blades are held in slots in plates mounted on the rotor.

20. A heat exchanger according to any preceding claim in which the stator comprises a stack of annular parts each of which provides only one of the projections.

21. A scraped-surface heat exchanger substantially as described above with reference to Figures 1 to 3 of the accompanying drawings.

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

Claims

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

co-pending Patent Application No.

7716/77 (Serial No. 1570027).

WHAT WE CLAIM IS: 1. A scraped-surface heat exchanger for treating a fluid material comprising a stator surrounding a rotor, the stator comprising a plurality of annular projections extending inwardly towards the axis of rotation of the rotor and dividing the space within the stator into a plurality of annular spaces which communicate with one another at locations radially inwardly of the tips of the projections, the rotor carrying scraping means comprising, in each annular space between two adjacent projections, at least one scraper blade which scrapes the whole of one flank of one projection and the whole of the opposite flank of the other projection whereby some of the material is scraped off the projections as the rotor rotates and is mixed with the remainder of the material.
2. A scraped-surface heat exchanger for treating a fluid material comprising a stator surrounding a rotor. the stator comprising a plurality of annular projections extending inwardly towards the axis of rotation of the rotor and the rotor carrying scraper means comprising, in each annular space between two adjacent projections, scraping means which scrape the whole of one flank of one projection, the whole of the opposite flank of the other projection, the part of the stator between the roots of the projections and half of the tip of each of the projections whereby some of the material is scraped off the projections as the rotor rotates and is mixed with the remainder of the material.
3. A heat exchanger according to claim 1 or 2, a first flank of each projection, which is the upper flank when the heat exchanger is appropriately positioned, with the axis of rotation of the rotor vertical, sloping downwardly, proceeding towards said axis when the heat exchanger is so positioned.
4. A heat exchanger according to claim 1 or 2 in which the flanks of each of the projections are substantially perpendicular to the axis of rotation of the rotor.
5. A heat exchanger according to any preceding claim in which the projections are hollow, the spaces within them being for one of the two fluids involved in the heat exchange.
6. A heat exchanger according to claim 5 in which the projections are of sheet material.
7. A heat exchanger according to claim 5 or 6 in which the spaces within the projections communicate with one another at their extremities remote from the rotor, so that said one of the fluids can flow into and out of them, from one to another along the stator.
8. A heat exchanger according to claim 7 in which the connections between the spaces within adjacent projections are staggered circumferentially so that said one of the fluids entering the space within one projection has to flow part of the way around the axis of rotation of the rotor before it can leave that space and flow into the space within the next projection.
9. A heat exchanger according to claim 8 in which the space within each projection is divided into a plurality of parts.
10. A heat exchanger according to claim 9 in which the division is effected by each projection being made up of two or more segments distributed around the axis of rotation of the rotor.
11. A heat exchanger according to any preceding claim in which the two flanks of each projection are provided by separate members.
12. A heat exchanger according to claim 10 in which the two flanks of each segment of each projection are provided by separate members.
13. A heat exchanger according to any one of claims 1 to 3 in which the projections taper, proceeding towards the axis of rotation of the rotor.
14. A heat exchanger according to claim 3 or any subsequent claim appended to claim 3 in which said opposite flanks of the projections slope downwardly, proceeding away from said axis.
15. A heat exchanger according to claim 3 or any subsequent claim appended to claim 3 in which the greater part of each upper flank is concavely rounded.
16. A heat exchanger according to claim 3 or any subsequent claim appended to claim 3 in which the greater part of each said opposite flank is concavely rounded.
17. A heat exchanger according to any preceding claim in which the tips of the projections are convexly rounded.
18. A heat exchanger according to any preceding claim in which there is concave rounding between the tips of adjacent projections.
19. A heat exchanger according to any preceding claim in which the blades are held in slots in plates mounted on the rotor.
20. A heat exchanger according to any preceding claim in which the stator comprises a stack of annular parts each of which provides only one of the projections.
21. A scraped-surface heat exchanger substantially as described above with reference to Figures 1 to 3 of the accompanying drawings.