Pre-heater assembly with moderately thermally conductive capillary surrounding

Abstract

A pre-heater assembly for pre-heating a fluid, in particular in a fluid separation apparatus, wherein the pre-heater assembly comprises a capillary having a lumen and being configured for conducting the fluid, and a thermal coupling body contacting at least part of the capillary, having a value of thermal conductivity in a range between 8 W/(m K) and 100 W/(m K) and being arrangable so that heat generated by a heat source is supplied to the capillary via at least part of the thermal coupling body.

Claims

1. A pre-heater assembly for pre-heating a fluid for a fluid separation apparatus, the pre-heater assembly comprising: a capillary having a lumen and being configured for conducting the fluid; and a thermal coupling body made of a plastic material, contacting at least part of the capillary, and having a value of thermal conductivity in a range between 8 W/(m K) and 100 W/(m K), wherein: the capillary is wound to increase the effective length of the capillary through which the fluid flows while being pre-heated; and the capillary is at least partially molded or cast within the thermal coupling body so that heat generated by a heat source is supplied to the capillary via at least part of the thermal coupling body.

2. The pre-heater assembly of claim 1, wherein the thermal coupling body is made of one selected from the group consisting of: a plastic molding compound, a casting compound, a plastic filled with thermally conductive particles, and a plastic composition.

3. The heater assembly of claim 1, wherein the wound capillary has a shape of the group consisting of a helical shape, a folded shape, a meandrical shape, a spiral shape, and a shape corresponding to a combination of two or more of the mentioned shapes.

4. The pre-heater assembly of claim 1, comprising a carrier around which the capillary is wound.

5. The pre-heater assembly of claim 1, wherein material of the thermal coupling body between adjacent windings of the capillary is thicker than material of the thermal coupling body between an exterior part of the capillary and an external surface of the pre-heater assembly.

6. The pre-heater assembly of claim 1, comprising at least one of the following features: the thermal coupling body has a value of the thermal conductivity in a range between 10 W/(m K) and 60 W/(m K); the thermal coupling body has a value of the thermal conductivity in a range between 10 W/(m K) and 30 W/(m K); the thermal coupling body is arranged so that the heat from the heat source is supplied to the fluid along a heat flow direction which is substantially perpendicular to an effective fluid flow direction through the capillary; the thermal coupling body is arranged so that the heat from the heat source is supplied to the fluid along a heat flow direction which is substantially perpendicular to an effective fluid flow direction along which the fluid effectively flows from an intersection between an upstream flange face of the thermal coupling body and the capillary to an intersection between a downstream flange face of the thermal coupling body and the capillary; the thermal coupling body is arranged so as to suppress a heat flow along a heat flow direction which is substantially antiparallel to an effective fluid flow direction through the capillary; the thermal coupling body is arranged so as to suppress a heat flow along a heat flow direction which is substantially antiparallel to an effective fluid flow direction along which the fluid effectively flows from an intersection between an upstream flange face of the thermal coupling body and the capillary to an intersection between a downstream flange face of the thermal coupling body and the capillary; the pre-heater assembly comprises at least one of the group consisting of a fluid inlet interface at an intersection between an upstream flange face of the thermal coupling body and the capillary, and a fluid outlet interface at an intersection between a downstream flange face of the thermal coupling body and the capillary, wherein at least one of the fluid inlet interface and the fluid outlet interface is configured to be selectively fluidically connectable to or fluidically disconnectable from a fluidic member; the pre-heater assembly is substantially shaped as a regular prism with a triangular flange face; substantially an entire external heat transfer surface of the pre-heater assembly is constituted by the thermal coupling body; the capillary is made of steel, or of plastic material surrounded by steel.

7. A fluid separation apparatus for separating a fluidic sample into a plurality of fractions, the fluid separation apparatus comprising: a fluid drive unit configured for driving a fluid comprising a mobile phase and the fluidic sample in the mobile phase; a separation unit configured for separating the fluidic sample into the plurality of fractions; and a pre-heater assembly configured for pre-heating the fluid upstream of the separation unit, the pre-heater assembly comprising: a capillary having a lumen and being configured for conducting the fluid; and a thermal coupling body made of a plastic material, contacting at least part of the capillary, and having a value of thermal conductivity in a range between 8 W/(m K) and 100 W/(m K), wherein: the capillary is wound to increase the effective length of the capillary through which the fluid flows while being pre-heated; and the capillary is at least partially molded or cast within the thermal coupling body so that heat generated by a heat source is supplied to the capillary via at least part of the thermal coupling body.

8. The fluid separation apparatus of claim 7, comprising the heat source, wherein the heat source is configured for generating heat for heating the separation unit and for pre-heating the fluid in the pre-heater assembly via at least part of the thermal coupling body when the fluid is conducted through the lumen of the capillary.

9. The fluid separation apparatus of claim 8, comprising a board being thermally coupled with the heat source, and having at least one accommodation recess configured for receiving the pre-heater assembly.

10. The fluid separation apparatus of claim 9, wherein the board comprises one selected from the group consisting of: a highly thermally conductive material; aluminium; and copper.

11. The fluid separation apparatus of claim 7, comprising an injector for injecting the fluidic sample into the mobile phase, wherein the injector is arranged upstream of the pre-heater assembly in a flow direction of the fluid.

12. The fluid separation apparatus of claim 7, further comprising at least one of: a detector configured to detect separated fractions of the fluidic sample; a fractioner unit configured to collect separated fractions of the fluidic sample; a data processing unit configured to process data received from the fluid separation apparatus; a degassing apparatus for degassing at least part of the fluid.

13. A method of manufacturing a pre-heater assembly for pre-heating a fluid for a fluid separation apparatus, the method comprising: providing a capillary having a lumen and being configured for conducting the fluid; forming a thermal coupling body of a plastic material having a value of thermal conductivity in a range between 8 W/(m K) and 100 W/(m K); contacting at least part of the capillary with the thermal coupling body; and arranging the thermal coupling body so that heat generated by a heat source is supplied to the capillary via at least part of the thermal coupling body; wherein the capillary is provided as a wound capillary and is at least partially molded or cast within the thermal coupling body.

14. The method of claim 13, wherein the thermal coupling body is made of one selected from the group consisting of: a plastic molding compound, a casting compound, a plastic filled with thermally conductive particles, and a plastic composition.

15. The method of claim 13, wherein the wound capillary has a shape of the group consisting of a helical shape, a folded shape, a meandrical shape, a spiral shape, and a shape corresponding to a combination of two or more of the mentioned shapes.

16. The method of claim 13, wherein the thermal coupling body is formed by overmolding or overcasting the capillary.

17. The method of claim 13, wherein the method further comprises winding the capillary around a carrier before forming the thermal coupling body to surround at least part of the wound capillary.

18. The method of claim 17, wherein the carrier and the thermal coupling body are made of the same material.

19. The method of claim 17, wherein the carrier and the thermal coupling body are made of different materials.

20. The method of claim 13, wherein the method further comprises winding the capillary without a carrier before forming the thermal coupling body to at least partially surround the wound capillary.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other objects and many of the attendant advantages of embodiments of the present invention will be readily appreciated and become better understood by reference to the following more detailed description of embodiments in connection with the accompanying drawings. Features that are substantially or functionally equal or similar will be referred to by the same reference signs.

(2) FIG. 1 shows a liquid separation device in accordance with embodiments of the present invention, particularly used in high performance liquid chromatography (HPLC).

(3) FIG. 2 is a schematic illustration of a pre-heater assembly according to an exemplary embodiment being supplied by thermal energy from a heat source.

(4) FIG. 3 shows a three-dimensional view of a structure obtained during carrying out a method of manufacturing a pre-heater assembly according to an exemplary embodiment of the invention.

(5) FIG. 4 shows another three-dimensional view of a structure obtained during carrying out a method of manufacturing a pre-heater assembly according to an exemplary embodiment of the invention.

(6) FIG. 5 shows another three-dimensional view of a structure obtained during carrying out a method of manufacturing a pre-heater assembly according to an exemplary embodiment of the invention.

(7) FIG. 6 shows another three-dimensional view of a structure obtained during carrying out a method of manufacturing a pre-heater assembly according to an exemplary embodiment of the invention.

(8) FIG. 7 shows a three-dimensional view of a pre-heater assembly according to an exemplary embodiment of the invention manufactured according to FIG. 3 to FIG. 6.

(9) FIG. 8 illustrates a detail of a heating chamber of a fluid separation apparatus according to an exemplary embodiment of the invention, wherein the heating chamber is configured for heating a fluid of the fluid separation apparatus and comprises a pre-heater assembly mounted in a recess of a mounting board.

(10) FIG. 9 illustrates the entire heating chamber illustrated in FIG. 8.

(11) FIG. 10 shows a three-dimensional view of a portion of a pre-heater assembly according to an exemplary embodiment of the invention mounted in a recess of a mounting board of a fluid separation apparatus according to an exemplary embodiment of the invention.

(12) FIG. 11 is a diagram illustrating a dependency of an outlet temperature of fluid conducted through a pre-heater assembly as a function of the thermal conductivity of a thermal coupling body of a pre-heater assembly according to an exemplary embodiment.

(13) The illustration in the drawing is schematic.

DETAILED DESCRIPTION

(14) Before, referring to the figures, exemplary embodiments will be explained in further detail, some basic considerations will be explained based on which exemplary embodiments have been developed.

(15) An exemplary embodiment of the invention provides for an integration of an arbitrarily bent/shaped capillary into an arbitrary outer shape in form of a thermal coupling body. More specifically, exemplary embodiments of the invention provide robust pre-heater assemblies as heat exchangers which are also very user convenient, as it may be sufficient that the user handles only a single monolithic part (i.e. the pre-heater assembly) which may also be provided with integrated fittings. As the shape of a capillary in the inside can be freely chosen, fluid properties can be optimized. As the outer shape defined by the thermal coupling body (which may also be denoted as a jacket) can be freely chosen, heat transfer properties as well as space utilization in device housings can be optimized. Truly three-dimensional shapes are possible.

(16) According to an exemplary embodiment, a manufacturing method is provided which is capable to greatly facilitate integration of an arbitrarily (for instance user defined) bent/shaped capillary into an arbitrary outer shape in form of the thermal coupling body to improve properties of the carried liquid (like, for instance, dispersion) while also improving heat transfer at reduced cost. A core or carrier of the pre-heater assembly may be made of appropriate material (as, for instance, heat conductive plastics or metal). This carrier serves as guide to bend a capillary in desired shape and keep it in place. Fittings can be added, if necessary. In particular, the provision of a female fitting on a front end (but not limited to a front end) is possible. Female fittings may lead to a very robust design, as no parts are likely to be broken when being handled by the user. The thermal coupling body as a jacket/enclosure may be built around the carrier. Exemplary embodiments of corresponding manufacturing procedures include (but are not limited to) investment casting, injection molding, compression of one or multiple parts around the core.

(17) Referring now in greater detail to the drawings, FIG. 1 depicts a general schematic of a liquid separation system 10. A pump 20 receives a mobile phase from a solvent supply 25, typically via a degasser 27, which degasses and thus reduces the amount of dissolved gases in the mobile phase. The pump 20—as a mobile phase drive—drives the mobile phase through a separating device 30 (such as a chromatographic column) comprising a stationary phase. A sampling unit 40 can be provided between the pump 20 and the separating device 30 in order to subject or add (often referred to as sample introduction) a sample fluid into the mobile phase. The stationary phase of the separating device 30 is configured for separating compounds of the sample liquid. A detector 50 is provided for detecting separated compounds of the sample fluid. A fractionating unit 60 can be provided for outputting separated compounds of sample fluid.

(18) While the mobile phase can be comprised of one solvent only, it may also be mixed from plural solvents. Such mixing might be a low pressure mixing and provided upstream of the pump 20, so that the pump 20 already receives and pumps the mixed solvents as the mobile phase. Alternatively, the pump 20 might be comprised of plural individual pumping units, with plural of the pumping units each receiving and pumping a different solvent or mixture, so that the mixing of the mobile phase (as received by the separating device 30) occurs at high pressure and downstream of the pump 20 (or as part thereof). The composition (mixture) of the mobile phase may be kept constant over time, the so called isocratic mode, or varied over time, the so called gradient mode.

(19) A data processing unit 70, which can be a conventional PC or workstation, might be coupled (as indicated by the dotted arrows) to one or more of the devices in the liquid separation system 10 in order to receive information and/or control operation. For example, the data processing unit 70 might control operation of the pump 20 (e.g. setting control parameters) and receive therefrom information regarding the actual working conditions (such as output pressure, flow rate, etc. at an outlet of the pump 20). The data processing unit 70 might also control operation of the solvent supply 25 (e.g. setting the solvent/s or solvent mixture to be supplied) and/or the degasser 27 (e.g. setting control parameters such as vacuum level) and might receive therefrom information regarding the actual working conditions (such as solvent composition supplied over time, flow rate, vacuum level, etc.). The data processing unit 70 might further control operation of the sampling unit 40 (e.g. controlling sample injection or synchronization of sample injection with operating conditions of the pump 20). The separating device 30 might also be controlled by the data processing unit 70 (e.g. selecting a specific flow path or column, setting operation temperature, etc.), and send—in return—information (e.g. operating conditions) to the data processing unit 70. Accordingly, the detector 50 might be controlled by the data processing unit 70 (e.g. with respect to spectral or wavelength settings, setting time constants, start/stop data acquisition), and send information (e.g. about the detected sample compounds) to the data processing unit 70. The data processing unit 70 might also control operation of the fractionating unit 60 (e.g. in conjunction with data received from the detector 50) which provides data back.

(20) FIG. 1 also shows a heat source 80 for generating thermal energy, i.e. heat, and can for instance be embodied as a Peltier heater or an ohmic heater. The heat source 80, in the shown embodiment, fulfils two tasks. Firstly, the heat source 80 heats a pre-heater assembly 90 according to an exemplary embodiment by heat conduction, wherein the pre-heater assembly 90, in turn, pre-heats fluid downstream of the injector 40 and upstream of the separating device 30. Secondly, the heat source 80 heats the separating device 30 by heat convection, wherein the separating device 30, in turn, heats the fluid within the separating device 30.

(21) FIG. 2 is a schematic illustration of the pre-heater assembly 90 according to an exemplary embodiment being supplied by thermal energy from the heat source 80.

(22) The pre-heater assembly 90 is configured for pre-heating a liquid (for instance a mixture between a mobile phase in form of one or more solvents and a fluidic sample to be separated by the fluid separation apparatus 10). The pre-heater assembly 90 comprises a (for instance helically or meandrically) wound capillary 200 having a lumen. The capillary 200 can be made of steel or, for instance if the liquid to be conducted is a biological fluid, can be made of steel with an interior layer of biocompatible plastic such as PEEK, PTFE, etc. The capillary 200 is configured for conducting the liquid when it is driven by a fluid drive unit such as pump 20. The capillary 200 may be formed with such a small inner diameter that the flow of the liquid within the lumen is laminar. The capillary 200 is monolithically embedded and fully surrounded by a thermal coupling body 202 configured as a plastic molding compound (optionally with filler particles to adjust the value of thermal conductivity of the thermal coupling body 202) contacting the full circumferential surface of the capillary 200. When the plastic material of the thermal coupling body 202 is mixed with thermally conductive filling particles, the resulting thermal coupling body 202 can be adjusted to have a value of thermal conductivity of approximately 20 W/(m K). This is a moderate value being higher than that of many thermally insulating plastic materials and being lower than that of conventional thermally conductive materials such as copper or aluminum (conventionally used thermally conductive materials may have a value of thermal conductivity of more than 200 W/(m K)). The thermal coupling body 202 forms an outer surface of the pre-heater assembly 90.

(23) As can be taken from the schematic drawing in FIG. 2, the thermal coupling body 202 is arranged so that heat generated by the heat source 80 (such as a Peltier heater) is supplied to the capillary 200 (and from there to the conducted liquid) via the thermal coupling body 202. Preferably but not necessarily, the heat transfer mechanism from the heat source 80 to the capillary 200 is heat conduction. FIG. 2 also shows an effective fluid flow direction 206 which is defined by a connection line between a fluid inlet interface 210 and a fluid outlet interface 212 of the pre-heater assembly 90, i.e. positions where the capillary 200 intersects with the thermal coupling body 202. Although the liquid traversing the pre-heater assembly 90 follows the wound trajectory of the capillary 200 embedded by the material of the thermal coupling body 202, the liquid effectively flows along the effective fluid flow direction 206. The heat transfer from the heat source 80 towards the capillary 200 occurs along a primary heat flow direction 204 which is substantially perpendicular to the effective fluid flow direction 206.

(24) However, there is a further—parasitic—heat transfer corresponding to a secondary heat flow direction 208 from the hot liquid close to the fluid outlet interface 212 towards the still colder liquid close to the fluid inlet interface 210. This results in an effective undesired temperature equilibration among different liquid parts or packets, and partially via the thermal coupling body 202, which, in turn, results in an undesired cooling of the liquid close to the fluid outlet interface 212. The parasitic secondary heat flow direction 208 is substantially perpendicular to the primary heat flow direction 204.

(25) According to exemplary embodiments of the invention, it has been surprisingly found that the desired heat transfer along the primary heat flow direction 204 is only slightly reduced, but the parasitic thermal energy flow along the secondary heat flow direction 208 is significantly reduced by a selection of the value of the thermal conductivity of the material of the heat transfer body or thermal coupling body 202 in a range between about 8 W/(m K) and about 100 W/(m K). It has further been surprisingly found that the net pre-heating performance of the liquid by the pre-heater assembly 90 is substantially improved by selecting an only moderately thermally conductive material of the thermal coupling body 202.

(26) The liquid in the capillary 200 flows from the fluid inlet interface 210 to the fluid outlet interface 212 and is heated during its flow by the primary heat flow oriented perpendicular (see reference numeral 204) to its effective fluid flow direction 206. Since the secondary heat flow from the already heated liquid close to the fluid outlet interface 212 back towards the still colder liquid close to the fluid inlet interface 210 occurs, thermal energy flows away from the liquid close to the fluid outlet interface 212 which deteriorates the pre-heating performance of the pre-heater assembly 90. However, in particular if the value of the thermal conductivity of the thermal coupling body 202 is selected as described beforehand, it has turned out that the secondary heat flow reducing the pre-heating performance is significantly weakened and the efficient performance of the pre-heater assembly 90 is improved.

(27) However, it is nevertheless advantageous that the primary heat flow along the primary heat flow direction 204 perpendicular to the effective flow direction 206 is rendered sufficiently efficient, so that the surrounding of the thermal coupling body 202 can be preferably made of a material with a high thermal conductivity such as aluminum. Moreover, it is advantageous that a smallest distance d between the capillary 200 and an exterior surface of the thermal coupling body 202 is sufficiently small to allow for an efficient heat transfer from the heat source 80.

(28) FIG. 3 to FIG. 6 show different three-dimensional views of structures obtained during carrying out a method of manufacturing a pre-heater assembly 90 according to an exemplary embodiment of the invention, wherein the manufactured pre-heater assembly 90 is shown in FIG. 7.

(29) FIG. 3 shows a carrier 300 which may for instance be made of a material such as plastic or a metal. The carrier 300 is rod-shaped and comprises a circumferentially running groove 302 serving as a guide and an accommodation for a capillary 200 to be wound around the carrier 300.

(30) FIG. 4 shows the carrier 300 with the capillary 200 wound around an exterior surface of the carrier 300. More precisely, the capillary 200 is guided along and accommodated within the groove 302 so as to precisely define the trajectory of the capillary 200 in the pre-heater assembly 90 to be manufactured.

(31) FIG. 5 and FIG. 6 show the arrangement of FIG. 4 with fittings 500 attached to both opposing ends of the carrier 300. These opposing ends are correspondingly shaped to receive the fittings 500 (which are here configured as female fittings). Via the fittings 500, the capillary 200 may be fluidically connected to another fluidic member (such as a fluidic valve, a separating device 30, an injector 40, etc.).

(32) FIG. 7 shows pre-heater assembly 90 according to an exemplary embodiment of the invention which is obtained by overmolding the arrangement of FIG. 5 and FIG. 6 with plastic material to thereby form the thermal coupling body 202. Forming the thermal coupling body 202 from plastic material has the advantage that it can be simply and cheaply manufactured by molding and that a monolithic preheater assembly 90 is obtained which promotes a proper thermal coupling to the exterior heat source 80. An exterior surface of the thermal coupling body 202 also constitutes an external surface of the entire pre-heater assembly 90. When viewing the pre-heater assembly 90 from a viewing direction perpendicular to a flange face thereof at which the fittings 500 are located the pre-heater assembly 90 has a substantially V-shape. Thus, the pre-heater assembly 90 is substantially shaped as a regular prism with an equilateral triangular base surface 700.

(33) FIG. 8 illustrates a detail of and FIG. 9 illustrates an entire heating chamber 810 of a liquid separation system 10 according to an exemplary embodiment of the invention, wherein the heating chamber 810 is configured for heating a liquid of the liquid separation system 10 and comprises a pre-heater assembly 90 as described referring to FIG. 7 which is mounted in a mounting recess 802 formed as a groove within a mounting board 800 of the heating chamber 810.

(34) The mounting board 800 is a plate made of a highly thermally conductive material such as aluminum. A plurality of substantially V-shaped grooves are formed as the mounting recesses 802 in the mounting board 800. The mounting recesses 802 are arranged horizontally and in parallel to one another. At the back side of the mounting board 800 (not shown) heat source 80 may be mounted for heating the mounting board 800. By heat conduction, the pre-heater assembly 90 as shown in FIG. 7 and being mounted with full-face contact within one of the mounting recesses 802 is heated by the heated mounting board 800. Due to the modular arrangement of the mounting recesses 802, a plurality of pre-heater assemblies 90 and/or other fluidic members (such as one or more separation devices 30) may be mounted on the mounting board 800 and hence in the heat chamber 810.

(35) In FIG. 8, only one pre-heater assembly 90 is mounted in one of the mounting recesses 802. The pre-heater assembly 90 shown in FIG. 7 is simply placed in one of the mounting recesses 802, and subsequently a turning knob 820 (as an example for a pre-heater fastening element) is turned (for instance by 90°) so that its radially outermost portion engages an undercut section (for instance shaped as a dovetail groove) in a surface portion of the mounting recess 802 and thereby fastens the pre-heater assembly 90 in the mounting recess 802. The corresponding V-shapes of the pre-heater assembly 90 and of the mounting recess 802 substantially simplify the mounting procedure by providing guidance and by also promoting a proper heat transfer by heat conduction.

(36) As can be taken from FIG. 9, additionally three separation devices 30 (here configured as chromatographic separation columns) are mounted in other mounting recesses 802. The separation devices 30 are mounted on the respective mounting recess 802 with a gap or some distance between an innermost surface of the mounting recess 802 so that the separation devices 30 are heated by heat convection rather than by heat conduction, which may be desired for separation devices 30 to obtain a homogeneous heating.

(37) FIG. 10 shows a three-dimensional view of a portion of pre-heater assembly 90 mounted in a corresponding mounting recess 802 of mounting board 800. FIG. 10 particularly shows as to how the turning knob 820 engages into undercut section 1000 to provide for a reversible fastening. The pre-heater assembly 90 rests with a form closure within the correspondingly shaped mounting recess 802.

(38) FIG. 11 is a diagram 1100 illustrating a dependency of an outlet temperature (plotted along an ordinate 1104) of liquid conducted through a pre-heater assembly 90 as a function of the thermal conductivity (plotted along an abscissa 1102) of a thermal coupling body 202 of the pre-heater assembly 90 according to an exemplary embodiment. This information is displayed in FIG. 11 for two different flow rates of 2.5 ml/min and 5.0 ml/min.

(39) The results in FIG. 11 are the result of a simulation. The outlet temperature of the liquid at the fluid outlet interface 212 is determined by a simulation for different materials of the thermal coupling body 202. It can be taken from FIG. 11 that approximately in a range from 8 W/(m K) to 100 W/(m K) better results can be obtained as with the conventional used and significantly more expensive and cumbersome materials aluminum and copper.

(40) It should be noted that the term “comprising” does not exclude other elements or features and the term “a” or “an” does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.