Laboratory condensers with passive heat exchange

Abstract

The present invention relates to a condenser for condensing gasses. The condenser comprises: an inner tube (1) having a bore (3) therethrough; an outer tube (2) having a bore (8) therethrough and two ends, the inner tube (1) passing through the bore of the outer tube (2); and a seal (15, 16) at each end of the outer tube. The outer tube has exterior and interior fins and is sealed to the inner tube so as to define a sealed space (11) between the inner tube and the outer tube. The space (11) is adapted to contain a liquid in contact with the inner tube (1) and the outer tube (2). The invention further relates to a method of condensing a gas using the condenser, a process of making a chemical using the condenser and a kit adapted to be assembled into the condenser.

Claims

1. An air-cooled laboratory gas condenser for condensing gasses and vapours, comprising: an inner tube having an elongate length and a bore extending therethrough between a first end region and a second end region of the inner tube, the inner tube being made from glass; an outer tube having a bore therethrough and two ends, the inner tube passing through the bore of the outer tube, the outer tube being made from a metal material; and a respective seal at each end of the outer tube, sealing the outer tube to the inner tube at the first and second end regions so as to define an annular elongate sealed space between the inner tube and the outer tube extending along the elongate length of the inner tube between the seals, wherein: the sealed space is at least partly filled with a heat-conductive liquid such that the liquid is in contact with both the inner tube and the outer tube, the outer tube comprises a plurality of internal fins extending into the sealed space between the inner tube and the outer tube and a plurality of external fins extending outwardly from an outer surface of the outer tube, each of the seals comprise a first part, the first part having an external threaded portion that engages a corresponding internal thread formed in the bore of the outer tube at a respective one of the ends of the outer tube so as to fix the first portion relative to the outer tube, each of the seals further comprise a second part, the second part having an internal threaded portion that engages with a corresponding external thread of the first part so as to fix the first and second parts together, the first and second parts of the seals each have respective through-holes through which the inner tube passes, and the inner tube is provided with a key for inter-engaging with only one of the seals, the first and second parts of the seal for which the key is provided being arranged to fit either side of the key.

2. The condenser of claim 1, wherein the key comprises a bulge in an outer diameter of the inner tube.

3. The condenser of claim 1, wherein the key comprises a resilient gasket or sealing member held between the first and second components of the seal for which the key is provided.

4. The condenser of claim 1, wherein each of the internal and/or external fins is ridged.

5. The condenser of claim 1, wherein the internal fins of the outer tube are of a length such that they do not touch the surface of the inner tube.

6. The condenser of claim 1, wherein the heat conductive liquid fills greater than 85% of the sealed space.

7. The condenser of claim 1, wherein the outer surface of the inner tube has one or both of indentations or projections.

8. The condenser of claim 7, wherein the indentations are formed by inwardly-extending indents in the wall of the inner tube, the indents forming both inwardly-extending projections into the space inside the inner tube and inwardly-projecting hollows in the outer surface of the inner tube.

9. The condenser of claim 7, wherein the projections comprise a first and a second set of projections, the first set of projections being interleaved with the second set and rotated relative to the second set about a central axis of the inner tube.

10. The condenser of claim 7, wherein the inner tube has smooth regions, devoid of indentations, at respective positions where the inner tube seals with the seals.

11. The condenser of claim 1, wherein the first component is a common component to both of the seals.

12. The condenser of claim 1, wherein the second component differs between the seals.

13. The condenser of claim 12, wherein the through-hole provided in the second component of one of the seals has a greater diameter compared to the through-hole provided in the second component of the other of the seals.

14. An air-cooled laboratory gas condenser for condensing gasses and vapours, comprising: an inner tube having an elongate length and a bore extending therethrough between a first end region and a second end region of the inner tube, the inner tube being made from glass; an outer tube having a bore therethrough and two ends, the inner tube passing through the bore of the outer tube, the outer tube being made from a metal material; and a seal at each end of the outer tube, sealing the outer tube to the inner tube at the first and second end regions so as to define an annular elongate sealed space between the inner tube and the outer tube extending along the elongate length of the inner tube between the seals, wherein: the sealed space is at least partly filled with a heat-conductive liquid such that the liquid is in contact with both the inner tube and the outer tube, the outer tube comprises a plurality of internal fins extending into the sealed space between the inner tube and the outer tube and a plurality of external fins extending outwardly from an outer surface of the outer tube, and the inner tube is provided with a key for inter-engaging with only one of the seals to locate the tubes relative to each other.

Description

(1) There now follows, by way of example only, description of an embodiment of the invention, described with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a condenser according to an embodiment of the invention;

(3) FIG. 2 shows a cross section through the condenser of FIG. 1 along line A-A;

(4) FIG. 3 shows an enlargement of area B of FIG. 2;

(5) FIG. 4 shows an enlargement of area C of FIG. 2;

(6) FIG. 5 shows a cross section through the outer tube of the condenser of FIG. 1;

(7) FIG. 6 shows an enlargement of area B of FIG. 5;

(8) FIG. 7 shows a perspective view of the common first part of the seal at either end of the condenser of FIG. 1;

(9) FIG. 8 shows a plan view of the second part of the seal for use at the top end of the condenser of FIG. 1;

(10) FIG. 9 shows a plan view of the second part of the seal for use at the bottom end of the condenser of FIG. 1;

(11) FIG. 10 shows a graphical table showing the acceptable condensers for various solvents;

(12) FIG. 11 shows a perspective view of an example experimental setup;

(13) FIG. 12 shows an end seal of the condenser in one embodiment;

(14) FIG. 13 shows detail of one component of the end seal of FIG. 12;

(15) FIG. 14 shows another way of using the present invention;

(16) FIG. 15 shows a cross-sectional view of the inner tube of an embodiment of the invention;

(17) FIG. 16 shows a plan view of part of the inner tube of FIG. 15; and

(18) FIG. 17 shows a cross-sectional view of the inner tube viewed on line XVII-XVII of FIG. 16.

(19) A condenser 100 according to an embodiment of the invention is shown in the accompanying drawings. The heat exchanger comprises a central inner tube 1 surrounded by an outer tube 2.

(20) We envisage our condenser being used in laboratories where people are trying to synthesise or isolate chemicals. Typically, it will be used to condense or reflux vapour leaving a heated chemical reactor vessel, such as a flask.

(21) The inner tube 1 is formed of borosilicate glass. It has an internal bore 3 for the passage of the gas to be condensed. The inner tube has a top end 4 and a bottom end 5. The inner tube 1 has a plurality of protrusions 6 extending into the bore 3, in the manner of a Vigreux condenser.

(22) The outer tube 2 is formed of extruded aluminium, and so is of consistent cross section along most of its length. It is of the form of a cylindrical shell 7 having an internal bore 8. Into this internal bore 8 extend a plurality of internal fins 9; in the present embodiment, there are 45 such fins equally spaced around the circumference of the cylindrical shell 7, extending along the length of the shell 7. The fins extend radially into the bore 8 by a consistent internal fin length, so that a cylindrical passage 10 is provided, which is occupied by the inner tube 1.

(23) Thus, between the inner tube 1 and the outer tube 2 there is defined a space 11 into which the internal fins 9 extend. This space is filled with a liquid 12, in contact with both inner 1 and outer 2 tubes, the liquid 12 being used as a heat-conducting liquid. Therefore, heat can easily pass from the inner tube 1 through the liquid 12 to the outer tube. The liquid has good heat transfer properties, and may be water. By filled with a liquid, we do not necessarily mean completely filled: we also envisage partially-filled arrangements, but we do also mean completely filled, or nearly so.

(24) In order to dissipate the heat transferred to the outer tube 2, the outer tube 2 is provided with external fins 13 extending along the length of the cylindrical shell 7 and radially outwards from an outer surface 14 of the cylindrical shell 7. In this embodiment, there are 60 such external fins 13 equally spaced around the circumference of the cylindrical shell 7. The external fins have a ridged profile (shown in more detail in FIG. 6 of the corresponding drawings) which increases the surface area of the external fins, which improves the heat transfer from the outer tube 2 to the surrounding air.

(25) In order to seal the space 11, a top seal 15 and a bottom seal 16 are provided. These seal the outer tube 2 and inner tube 1 together, and each seal one end of the space 11.

(26) Each of the seals 15, 16 comprise a common first part 17. This comprises an annular plastic member, formed of acetal. The first part 17 has a step in external diameter, and as such is made up of a narrower portion 18 and a wider portion 19. The external circumferential surfaces of both portions 18, 19 are threaded. The thread of the narrower portion 18 engages a corresponding thread 20, 21 formed in the internal bore 8 at the respective end of the outer tube 2, so as to fix the first portion relative to the outer tube 2.

(27) The first part 17 has a through-hole 22 through which the inner tube passes. In one embodiment (but not in others) the inner tube 1 is provided with a bulge 23 in diameter at its bottom end bigger than the through-hole 22, so that the bulge 23 cannot pass through the first part 17 but will rest against it. This may help to locate the tubes relative to each other. The gap 24 defined between the first part 17 and the outer tube 2 is filled with a sealant, such as polyurethane or an o-ring seal.

(28) Each of the seals also comprises a generally annular second part 25, 26; different second parts may be provided for the top end (top second part 25) and bottom end (bottom second part 26). However, the function of both parts is similar. Each second part 25, 26 has a narrow potion 27 of reduced internal diameter compared to a wider portion 28. The wider portion 28 is provided with an internal thread, which engages the thread of the wider portion 19 of the first part 17, so as to fix the two parts together.

(29) The narrow portion 27 has an internal through-hole 29, 30; the through-hole 29 of the top seal 15 may be bigger than the through-hole 30 of the bottom seal 16 as the inner tube 1 may differ in diameter from top to bottom. The narrower portions also have a groove or ridge 31 on the face that will contact the end face of the outer tube. This groove or ridge 31 is of the same diameter as the cylindrical shell 7. The groove or ridge 31 provides location 33 for further sealant of the same material as discussed above to be trapped between the inner tube 2 and first part 17, further sealing the space 11.

(30) The second parts 25, 26 are provided with flats 32, so that the condenser 100 is less likely to roll if placed on a flat surface.

(31) In use, a gas to be condensed is passed through the internal bore 3 of the inner tube 1, typically from bottom end 5 to top end 4. The gas to be condensed will typically be mixed with other gasses, such as air. The gas will be at above the local temperature and notably above the temperature of the outer tube 2 and thus the inner tube 1.

(32) As the gas passes over the protrusions 6 of the inner tube, if the inner tube 1 is at less than the boiling point of the gas, the gas will condense and, if the bottom end 5 is lower than the top end, as in the experimental set up shown in FIG. 11 of the accompanying drawings, run down the internal bore 3 under gravity. It can then be collected in a flask 101. The flask 101 can either be the original flask from which the gas was evaporated (in which case the process is reflux) or a different flask (distillation or evaporation).

(33) However, this will involve heat transfer to the inner tube 1. The liquid (e.g. water) 12 will conduct this heat away from the inner tube 1 to the outer tube 2 through the internal fins 9. The heat will pass through the outer tube 3 to the external fins, where it will be dissipated to the local atmosphere (as long as that is suitably cooler than the temperature of the gas).

(34) A condenser 100 according to this embodiment was tested against a straight air-cooled condenser and an air-cooled Vigreux condenser. In each case, 50 millilitres of various solvents was placed in a 100 ml flask 101 on a heating block 102 set at 20 degrees centigrade above the solvent's boiling point. A condenser of each type was attached to the flask. The amount of solvent lost after increasing amount of time in millilitres was recorded as follows:

(35) TABLE-US-00001 Boiling point Solvent (deg C.) condenser type 90 min 300 min 960 min Methanol 65 Air 3 5 12 Methanol 65 Air Vigreux 0 0 12 Methanol 65 Embodiment 0 2 5 Ethanol 78 Air 0 4 17 Ethanol 78 Air Vigreux 0 0 0 Ethanol 78 Embodiment 0 0 2 Isopropyl Alcohol 108 Air 2 4 15 Isopropyl Alcohol 108 Air Vigreux 0 0 0 Isopropyl Alcohol 108 Embodiment 0 0 2 Diethyl ether 35 Air 9 na na Diethyl ether 35 Air Vigreux 30 na na Diethyl ether 35 Embodiment 3 7 15 Tetrahydrofuran 66 Air 0 9 na Tetrahydrofuran 66 Air Vigreux 2 5 na Tetrahydrofuran 66 Embodiment 2 2 4 Ethyl acetate 77 Air 3 7 23 Ethyl acetate 77 Air Vigreux 0 0 3 Ethyl acetate 77 Embodiment 0 0 2 Dioxane 101 Air 0 0 0 Dioxane 101 Air Vigreux 0 0 2 Dioxane 101 Embodiment 0 0 2 Heptane 98 Air 0 0 4 Heptane 98 Air Vigreux 0 0 5 Heptane 98 Embodiment 0 0 3 Acetonitrile 82 Air 0 1 3 Acetonitrile 82 Air Vigreux 0 0 0 Acetonitrile 82 Embodiment 0 0 2 Toluene 111 Air 0 0 0 Toluene 111 Air Vigreux 0 0 0 Toluene 111 Embodiment 0 0 3 Acetone 57 Air 2 19 na Acetone 57 Air Vigreux 2 12 30 Acetone 57 Embodiment 0 2 5 Dichloromethane 40 Air 9 na na Dichloromethane 40 Air Vigreux 5 30 na Dichloromethane 40 Embodiment 2 2 5 Chloroform 61 Air 0 2 7 Chloroform 61 Air Vigreux 0 0 2 Chloroform 61 Embodiment 0 0 2

(36) A water-cooled condenser in similar situations was found generally not to loose any solvent. As such, whilst the condenser of the present embodiment might not reach the efficiency of a water-cooled condenser, it can be seen from the above table that there is generally significantly less solvent loss than with standard air-cooled condensers. As such, the condenser of the present embodiment provides an improvement on such condensers without the need for a running water supply; the condenser of the present embodiment can be used with solvents having a lower boiling point than prior art air-cooled condensers, without needing to resort to a water-cooled condenser.

(37) This can be seen in FIG. 10, which shows which condensers (straight air-cooled, Vigreux air-cooled, the present embodiment and water-cooled) have been found to be acceptable for different solvents (for each condenser indicated, the condensers listed above in the key would also be acceptable). Here, acceptable is taken as less than 10% solvent loss (solvents with boiling point at 50 degrees C. and over), with heating set point 15C above boiling point, after 16 hours. The area indicated for the present embodiment would previously have required a water-cooled condenser.

(38) Whilst the present embodiment has been described with reference to a laboratory setting, the invention could equally well be implemented on any desired scale, for example pilot plant or other industrial settings.

(39) The condenser would be provided to a user/customer (e.g. a chemical synthesis laboratory) pre-assembled with the heat-transfer liquid encapsulated between the inner and outer tubes and the end seals already fitted and sealed to the inner and outer tubes. That is our preferred arrangement. An alternative is to provide the condenser at least partially disassembled to allow the user to put their own heat transfer liquid (e.g. water) between the first and second tubes, and to have the user seal the end(s).