Device and method for thermo-electric drying a gaseous stream

Abstract

Device (100) for drying a gaseous stream, comprising an inflow duct (10) having a first inlet port (11) and a first outlet port (12), a first outflow duct (20) and a second outflow duct (30) parallel to the inflow duct, each having a second inlet port (21, 31) and a second outlet port (22, 32), thermo-electric heat pumps (40) configured to transfer heat from the inflow duct (10) to a respective one of the first and second outflow ducts (20, 30), wherein the inflow duct is arranged between the first and the second outflow ducts, a manifold (50) in fluid communication with the first outlet port (12) and with each of the second inlet ports (21, 31), wherein the manifold is configured to split the gaseous stream of the inflow duct in first and second substreams conveyed to the first and second outflow ducts in countercurrent flow with respect to the gaseous stream in the inflow duct, and a liquid separator (70) configured to separate condensate formed in the inflow duct.

Description

DEVICE AND METHOD FOR THERMO-ELECTRIC DRYING A GASEOUS STREAMTechnical field

[0001] The present invention is related to a device for drying a gaseous stream, particularly by utilizing thermo-electric heat pumps and to a method configured therefor. The gaseous stream is more specifically air, such as compressed air.Background art

[0002] Devices of the above-mentioned kind are known from EP 2661592 and comprise a cooling duct, a condensate separator at an outlet of the cooling duct and a heating duct that is arranged from the condensate separator along the cooling duct. A first series thermo-electric devices (heat pumps) are arranged between the cooling and the heating ducts to exchange heat between both ducts. Additional thermo-electric devices are arranged upstream, which are in thermal contact with a side of the cooling duct that is opposite to the side of the cooling duct in thermal contact with the first series of thermo-electric devices.

[0003] The above-mentioned devices show in practice a number of disadvantages. Firstly, the efficiency of the heat transfer is strongly dependent on a good thermal contact between the thermo-electric heat pumps and the ducts. EP 2661592 therefore suggests to provide a heat transfer paste between the external surfaces of the thermo-electric heat pumps and the side surfaces of the ducts. In practice it has been shown that the provision of such paste is insufficient and measures will have to be taken to clamp the parts together properly. One problem that occurs in this respect is shearing due to differential expansion. Since the cooling duct and the heating duct in EP 2661592 will expand differentially (one will shrink and the other one will expand), the structure will warp over time, exposing the clamped thermo-electric heat pumps to shear forces, which will lead to rupture and failure of the thermo-electric components over time.

[0004] A second disadvantage is that the heat which must be dissipated by a thermo-electric heat pump is larger than the heat which is withdrawn by the thermoelectric heat pump. Indeed, thermo-electric heat pumps also dissipate electrical energy, which must be expelled together with the withdrawn heat. In EP 2661592, the cooling duct and the heating duct are of a same type, consequently resulting in a suboptimal heat transfer.

[0005] EP 3312530 describes a device for heat exchange, comprising a stack of two first modules and two second modules, each comprising a fluid channel, and two series of thermo-electric heat pumps. The two first modules are arranged as outer modules in the stack and the two second modules are arranged as inner modules,with the thermo-electric heat pumps arranged between a respective first and second module. The symmetrical construction of the stack prevents warping of the structure and allows safe clamping of the thermo-electric heat pumps. A disadvantage of this structure is that each component in the stack must be provided twice, hence increasing material requirement and therefore cost.Summary

[0006] It is an aim of the present invention to obviate the above-mentioned disadvantages of the prior art. More specifically, is it an aim of the present invention to provide a device and method for drying a gaseous stream on the basis of thermo-electric heat pumps, which are more efficient and / or guarantee a longer service life of the components. It is further an aim of the present invention to provide such devices and methods, which allow for easy scale-up and / or less expensive manufacture.

[0007] According to a first aspect, there is therefore provided a device for drying a gaseous stream as set out in the appended claims. A device for drying a gaseous stream comprises an inflow duct having a first inlet port and a first outlet port, a first outflow duct and a second outflow duct, each having a second inlet port and a second outlet port, and thermo-electric heat pumps configured to transfer heat from the inflow duct to a respective one of the first and the second outflow ducts. The inflow duct is arranged between the first and the second outflow ducts. Advantageously, the first inlet port and the second outlet ports are arranged at a first end, and the first outlet port and the second inlet ports are arranged at a second end opposite the first end. Advantageously, the inflow duct and the first and second outflow ducts are arranged substantially parallel to one another along a longitudinal axis defining a direction of flow through the inflow duct and the first and second outflow ducts, such as between the first end and the second end. At least a first thermo-electric heat pump is arranged between a first wall of the inflow duct and a wall of the first outflow duct. This first wall of the inflow duct and the wall of the first outflow duct are advantageously arranged opposite each other. At least a second thermo-electric heat pump is arranged between a second wall of the inflow duct (opposite the first wall) and a wall of the second outflow duct. This second wall of the inflow duct and the wall of the second outflow duct are advantageously arranged opposite each other. Advantageously, each of the first and the second thermoelectric heat pumps are configured with a hot side and a cold side, wherein the cold side is in thermal contact with (a wall of) the inflow duct and the hot side is in thermal contact with (a wall of) the respective first and second outflow ducts. The device further comprises a manifold in fluid communication with the first outlet port and with each of the second inlet ports. The manifold is configured to split the gaseous stream flowing throughthe first outlet port (inflow duct) into advantageously two (or more) substreams that are each conveyed to a respective second inlet port of the first and the second outflow ducts. By so doing, it is advantageously obtained that the substreams are conveyed through the first and second outflow ducts in countercurrent flow with respect to the flow of the gaseous stream through the inflow duct. The device advantageously further comprises a liquid separator configured to separate condensate which is formed in the inflow duct. The liquid separator is advantageously arranged in proximity of the first outlet port, e.g., upstream from the manifold.

[0008] By splitting up the gaseous stream in (at least) two substreams that are conveyed along two outflow ducts on both sides of the inflow duct, it is advantageously obtained that per unit flow rate, the available surface area to give off heat (to the outflow ducts) is significantly larger than the surface area with which heat is withdrawn (from the inflow duct). As a consequence, not only the heat withdrawn from the inflow duct, but also the energy dissipated in the thermo-electric heat pumps can be drained away better, possibly resulting in higher efficiency. An additional advantage is that a symmetrical arrangement is obtained, which causes the outermost ducts to go through a similar temperature profile. Such a “sandwich”-structure can largely prevent warping of the structure. This leads to a longer service life of the thermo-electric heat pumps.

[0009] Advantageously, the device further comprises a clamping device configured to clamp the inflow duct and the thermo-electric heat pumps between the first and the second outflow ducts.

[0010] Advantageously, the inflow duct and the first and the second outflow ducts each define a longitudinal axis, wherein each of the longitudinal axes substantially defines a flow direction through the respective inflow duct and the first and the second outflow duct, and wherein the device is configured such that the longitudinal axes are arranged substantially vertically, e.g., wherein the longitudinal axes are at an angle comprised between 65° and 90° with respect to the horizontal, particularly between 70° and 90°. It is appreciated that the angles with respect to the horizontal as defined in the present disclosure are to be understood as being symmetrical with respect to 90°, i.e. , an angle between 70° and 90° comprises the angles between 90° and 110° as well.

[0011] According to an alternative aspect of the present invention, there is provided a device for drying a gaseous stream, comprising an inflow duct having a first inlet port and a first outlet port, a first outflow duct having a second inlet port and a second outlet port and at least one thermo-electric heat pump configured to transfer heat from the inflow duct to the first outflow duct. The at least one thermo-electric heat pump isarranged between a first wall of the inflow duct and a wall of the first outflow duct. This first wall of the inflow duct and the wall of the first outflow duct are advantageously arranged opposite each other. Advantageously, each of the (at least one) thermo-electric heat pumps are configured with a hot side and a cold side, wherein the cold side is in thermal contact with the inflow duct and the hot side is in thermal contact with the first outflow duct. The device further comprises a manifold in fluid communication with the first outlet port and the second inlet port.

[0012] According to an embodiment of the alternative aspect, the manifold is advantageously provided to convey the gaseous stream from the first outlet port (integrally) to the second inlet port. According to an alternative embodiment, the device advantageously comprises a second outflow duct arranged at an opposite side of the inflow duct with respect to the side along which the first outflow duct is arranged. The second outflow duct comprises a respective second inlet port and second outlet port. The manifold is advantageously also in fluid communication with the second inlet port of the second outflow duct. At least a second thermo-electric heat pump is advantageously arranged between the inflow duct and the second outflow duct and is configured to transfer heat from the inflow duct to the second outflow duct.

[0013] Advantageously, the inflow duct and the first (and possibly second) outflow duct each define a longitudinal axis, wherein each of the longitudinal axes substantially define a flow direction through the respective inflow duct and the first (and second) outflow duct.

[0014] According to a preferred embodiment, the device is configured such that the longitudinal axes are arranged substantially horizontally.

[0015] A horizontal arrangement of the device enables to drain condensate along the inflow duct. By consequence, the condensate is drained faster, compared to draining at the outlet port of the inflow duct, resulting in improved heat transfer efficiency.

[0016] A substantially horizontally arranged axis advantageously refers to an axis at an angle with the horizontal between 0° and 25°, e.g., between 0° and 20°.

[0017] According to an alternative embodiment, the device is configured such that the longitudinal axes are substantially inclined, e.g. wherein the longitudinal axes are at an angle with the horizontal comprised between 25° and 70°, particularly between 25° and 65°. In the above horizontal or inclined arrangements, the first wall of the inflow duct and the wall of the first outflow duct, which are in thermal contact with the (at least one) thermo-electric heat pump are advantageously arranged substantially vertically.

[0018] Advantageously, the inflow duct comprises a gutter arranged between the first inlet port and the first outlet port, the gutter being configured to collect liquid condensed in the inflow duct.

[0019] Advantageously, the inflow duct comprises a perforated wall extending between the first inlet port and the first outlet port. The perforated wall is advantageously configured to drain condensate of the inflow duct. The perforated wall can form a bottom plate of the inflow duct. A channel can be arranged underneath the perforated wall to serve as gutter for collecting condensate.

[0020] Devices according to the first aspect can comprise features of devices according to the alternative aspect and vice versa. Particularly, the device according to the first aspect can be arranged inclined or even substantially horizontally. In such cases a gutter as described above is advantageously provided.

[0021] According to a further aspect, there is provided an assembly which comprises the above-mentioned device (according to the first aspect and / or according to the alternative aspect) and a pretreatment part. The pretreatment part advantageously comprises at least one heat exchanger configured to withdraw heat from the gaseous stream upstream from the first inlet port. The pretreatment part can comprise a first heat exchanger that is advantageously configured as a passive heat exchanger. The first heat exchanger can comprise a third duct and a fourth duct and be configured to transfer heat between the third duct and the fourth duct, wherein the third duct comprises a third inlet port and a third outlet port and the fourth duct comprises a fourth inlet port and a fourth outlet port, wherein the third outlet port is in fluid communication with the first inlet port and the fourth inlet port is in fluid communication with the second outlet ports of the first and second outflow ducts. Alternatively, or in addition, the pretreatment part can comprise a second heat exchanger advantageously configured as an active heat exchanger. Advantageously, the second heat exchanger comprises a fifth duct having a fifth inlet port and a fifth outlet port, wherein the fifth outlet port is in fluid communication with the first inlet port. The second heat exchanger advantageously further comprises a sixth duct and possibly a seventh duct. The fifth and sixth ducts are arranged next to each other. The fifth duct can advantageously be arranged between the sixth duct and the seventh duct such that walls of the fifth duct are arranged opposite to a respective wall of the sixth and seventh ducts, and wherein the second heat exchanger is configured to allow a heat transfer fluid, advantageously a heat transfer liquid such as water, to flow through the sixth and possibly the seventh ducts.

[0022] According to a second aspect, there is therefore provided a use of the device according to the first (or alternative) aspect, as set out in the appended claims.

[0023] According to a third aspect, there is therefore provided a method for drying a gaseous stream, as set out in the appended claims. A method for drying a gaseous stream comprises supplying the gaseous stream through an inflow duct, dividing the gaseous stream egressing from the inflow duct in at least two streams and conveying the at least two streams through respective outflow ducts in countercurrent flow with respect to the inflow duct, actively transferring heat of the gaseous stream from the inflow duct to the at least two streams in the outflow ducts by means of thermoelectric heat pumps, and separating a condensate formed in the inflow duct. Advantageously, the inflow duct and the thermo-electric heat pumps are clamped between the outflow ducts. The gaseous stream is advantageously air, preferably compressed air.Brief description of the drawings

[0024] Aspects of the invention will be described in the following with reference to the appended drawings. In the drawings, corresponding components are designated with same reference numerals.

[0025] Figure 1 represents a perspective view of a device according to aspects of the invention.

[0026] Figure 2 represents a cross section along section line A-A of the device of Fig. 1.

[0027] Figure 3 represents a side view of the device of Fig. 1.

[0028] Figure 4 represents a perspective view of a detail of the device ofFig. 1.

[0029] Figure 5 represents a top view of the manifold of the device of Fig. 1 .

[0030] Figure 6 represents a diagram of the flow of the gaseous stream(white arrows) and the heat flow (black arrows) through the device of Fig. 1.

[0031] Figure 7 represents a longitudinal section along section line B-B of a horizontally arranged device according to aspects of the invention.

[0032] Figure 8 represents a cross section along section line C-C of the device of Fig. 7.

[0033] Figure 9 represents a longitudinal section of an alternative embodiment of the horizontally arranged device.

[0034] Figure 10 represents a diagram of an assembly of the device according to the preceding figures and a pretreatment device.

[0035] Figure 11 represents a diagram of a pretreatment device with active heat exchanger, wherein the white arrows designate the fluid flow and the black arrows designate the heat flow.Detailed description

[0036] With reference to Figs. 1 - 4, a device 100, configured to dry a gaseous stream, comprises an inflow duct 10, a first outflow duct 20 and a second outflow duct 30. The inflow duct 10 extends from an inlet port 11 , arranged at a first end 101 of the device 100, to an outlet port 12, arranged at a second end 102 of the device 100. The second end 102 is arranged opposite the first end 101 along a longitudinal axis 103 of the device 100. The first and second outflow ducts 20, 30 extend from respective inlet ports 21 , 31 , arranged at the second end 102, to respective outlet ports 22, 32, arranged at the first end 101.

[0037] The cross sections of the inflow duct 10 and of the outflow ducts 20,30 can assume any desired shape. Advantageously, the circumference of the cross section has a substantially constant or fixed shape. Advantageously, the inflow duct 10 comprises at least two planar outer side walls 13, 14 (Fig. 2), that are advantageously arranged at opposite sides of the inflow duct 10. The first and second outflow ducts 20, 30 each advantageously comprise at least one planar outer side wall 23, 33. The inner section of the cross section of the inflow duct and the outflow ducts is advantageously shaped to maximize the surface area for heat transfer between the duct walls and the gaseous stream, e.g. by means of cooling fins 15.

[0038] The inflow duct 10 and the first and second outflow ducts 20, 30 are arranged substantially parallel to one another, along the longitudinal axis 103. This longitudinal axis 103 also defines a (general) direction of flow of the gaseous stream through the inflow duct and the outflow ducts, particularly between the first end 101 and the second end 102. The inflow duct 10 is advantageously arranged centrally, and is clamped between the first and second outflow ducts 20, 30 which are arranged on both sides of the inflow duct. Advantageously, the arrangement is such that an outer side wall 23, 33 of the first and the second outflow duct 20, 30 respectively is arranged opposite to a respective outer side wall 13, 14 of the inflow duct 10.

[0039] Thermo-electric heat pumps 40 are arranged between the inflow duct 10 and each of the first and second outflow ducts 20, 30. These thermo-electric heat pumps are configured to transfer heat between a first outer surface (first side) and a second, opposite outer surface (second side) by application of an electrical voltage. By applying electrical voltage, the first side of the thermo-electric heat pump will heat up and form a so-called hot side and the second side will cool down and form a so-called cold side. Consequently, heat can be withdrawn via the cold side of the thermo-electric heat pump and drained via the hot side. The thermo-electric heat pumps 40 are advantageously Peltier-elements and are well-known in the art. Such Peltier-elementscomprise an array of negatively and positively doped semiconductor pairs that are connected electrically in series and are arranged thermally in parallel between two substrates that form the first and second sides of the thermo-electric heat pumps. Advantageously, the thermo-electric heat pumps are arranged in thermal contact with the planar outer side walls 13, 14, 23, 33 of the inflow and outflow ducts. To improve the heat transfer, a paste or contact liquid with thermally conductive properties can be provided at the contact surfaces, as well-known in the art. The thermo-electric heat pumps are advantageously arranged such that the cold sides are in thermal contact with the outer walls 13, 14 of the inflow duct 10 and the hot sides are in thermal contact with the outer walls 23, 33 of the respective outflow duct.

[0040] The thermo-electric heat pumps are advantageously disposed along the longitudinal axis 103 between the two ends 101 and 102. The disposition can be provided in a single row, or advantageously in multiple rows along the longitudinal axis 103. Advantageously, the thermo-electric heat pumps are disposed in two rows 41 , 42 and 43, 44 each, extending along the longitudinal axis 103 on both sides of the inflow duct 10. Such arrangement allows to provide electrical wiring along the outside, hence reducing heat losses.

[0041] The thermo-electric heat pumps 40 are advantageously clamped between the inflow and outflow ducts. A clamping device 60 can advantageously keep the assembly of inflow duct 10, first and second outflow ducts 20, 30 and the thermoelectric heat pumps 40 clamped. The clamping device 60 can comprise a set of clamping bars 61 that are pressed together by means of threaded rods 62. The clamping bars 61 are advantageously arranged against the advantageously planar outer side walls 24, 34 of the first and second outflow ducts 20, 30. Alternatively, other clamping devices, such as known from EP 3312530, can be provided to clamp the assembly.

[0042] A manifold 50 is arranged between the outlet port 12 of the inflow duct and the inlet ports 21 , 31 of the first and second outflow ducts. In an embodiment and referring to Fig. 5, the manifold 50 comprises a tubular body 51 having an inlet port 54, a first tubular branch 52 and a second tubular branch 53. Both tubular branches 52, 53 are in fluid communication with the inlet port 54, which is connected to outlet port 12 of the inflow duct 10. Each of the branches 52, 53 comprises a respective outlet port 55, 56, which is connected to the respective inlet port 21 , 31 of the first and second outflow ducts. The manifold 50 is configured to convey the gaseous stream egressing from the inflow duct 10 through the outlet port 12 to the inlet ports 21 , 31 of the first and second outflow ducts. To this end, the manifold is configured to divide the gaseous stream of the inflow duct between the first and second outflow ducts 20, 30, advantageously insubstantially equal parts. Since the outlet port 12 and the inlet ports 21 , 31 are arranged at a same end 102 of the device 100, the manifold can be of plain shape.

[0043] With reference to Fig. 1 , the device 100 further comprises a liquid separator 70, configured to separate the condensate that forms in the inflow duct from the gaseous stream. In this embodiment, in which the longitudinal axis 103 is arranged substantially vertically, the liquid separator 70 is advantageously arranged at, or in proximity of, the outlet port 12. The liquid separator 70 can e.g. be arranged between the outlet port 12 of the inflow duct and the manifold 50. Alternatively, the liquid separator can be integrated in the manifold 50, or can be arranged downstream from the manifold, e.g. between the manifold and the inlet ports 21 , 31 of the first and second outflow ducts 20, 30. In the latter embodiment, separate liquid separators can be provided in each part of the manifold.

[0044] Advantageously, a second manifold 80 is arranged at the first end101 . The second manifold 80 is configured to connect the outlet ports 22, 32 of the first and second outflow ducts 20, 30 to each other, thereby joining the gaseous stream split by manifold 50 again and applying it at a single outlet port 81.

[0045] With reference to Fig. 6, the device 100 is utilized as follows. A gaseous stream 90 is applied to the inlet port 11 of the inflow duct 10. The gaseous stream can be any gaseous fluid (e.g., gas or supercritical fluid) that comprises a condensable substance or component. The gaseous fluid is advantageously air, particularly compressed air, that e.g. comprises water vapour. The gaseous stream (e.g. compressed air) can be applied to the inlet port 11 at an elevated pressure, e.g. 4 bar or higher, or 5 bar or higher. The device 100 is advantageously configured to resist such elevated pressures.

[0046] The gaseous stream 90 flows through the inflow duct 10, wherein heat Qi is withdrawn from the gaseous stream by the thermo-electric heat pumps 40. As a result, the gaseous stream 90 cools down in the inflow duct as it approaches the outlet port 12. The cooling down of the gaseous stream 90 is configured such that the condensable component (e.g. water vapour) condenses or precipitates. Due to the vertical arrangement, the condensate 71 will advantageously collect at the outlet port 12, where it can be separated out by liquid separator 70.

[0047] The cooled gaseous stream 90 is split up in two separate streams91 , 92 at the outlet port 12, advantageously downstream from the liquid separator 70. Each stream 91 , 92 is conveyed to the inlet port 31 , 21 of the respective outflow duct. It is appreciated that the streams 91 , 92 flow through the outflow ducts in countercurrent flow with respect to the flow of the gaseous stream 90 through the inflow duct. The heatQi withdrawn from the stream 90 is advantageously supplied as heat Q2 to the streams 91 , 92. As a result, the streams in the outflow ducts heat up as they approach the respective outlet ports 22, 32.

[0048] Consequently, the device 100 advantageously has an arrangement showing mirror symmetry, in which a median plane of the inflow duct 10 that comprises the longitudinal axis 103 serves as symmetry plane. This median plane is advantageously parallel to the outer side walls 13, 14 of the inflow duct which are in thermal contact with the thermo-electric heat pumps.

[0049] In the device 100, the inflow and outflow ducts are advantageously arranged in a W-shaped pattern, in which the gaseous stream is supplied in the central leg of the “W’ and discharged from the side legs. Such an arrangement has several advantages. Firstly, it is remarked that Q2 > Qi since not only the heat Qi withdrawn from the stream 90 must be drained by the thermo-electric heat pumps, but also the electrical energy that is dissipated by the thermo-electric heat pumps. Consequently, Q2 = Qi + Qe, wherein Qerepresents the electrical energy dissipated in the thermo-electric heat pumps. By splitting up the gaseous stream 90 when flowing out of the inflow duct 10 and conveying it in countercurrent flow symmetrically along the inflow duct, it is obtained that a larger surface area for drainage of the heat Q2 can be utilized per unit flow rate. For the surface area is doubled with respect to the U-shaped arrangement known from EP 2661592. This results in increased efficiency, since Q2 > Qi.

[0050] Advantageously, the heat transfer efficiency can be further improved by an appropriate design of the first and second outflow ducts. These can be provided with a larger perimeter (surface area) for heat drainage per unit flow area of the duct with respect to the inflow duct. Particularly, the hydraulic radius Rhof the inflow duct is larger than a hydraulic radius Rh,0of the first and second outflow ducts. The hydraulic radius is defined as a ratio of the cross sectional area of flow A (free area) of the respective duct to the wetted perimeter D of the cross section of the respective duct: Rh,(i,o) = A / D. Advantageously, the wetted perimeter in relation to the free cross sectional area is larger with the outflow ducts than with the inflow duct. This can result in a better drainage of the heat Q2.

[0051] A second advantage of such a symmetrical arrangement is that the outer (outflow) ducts show a similar temperature profile, such that at start up and shut down differential expansion is avoided and the structure does not warp. As a result, shear stresses between the cold side and the hot side of the thermo-electric heat pumps are avoided as much as possible, hence early failure of the latter is avoided and the device has a longer lifetime.

[0052] In practice it can be useful to provide a thermal insulation sleeve around the device 100. The inflow and / or outflow ducts are typically at a lower temperature level with respect to ambient temperature. Applying thermal insulation around the device can therefore increase the efficiency of the thermo-electric heat pumps.

[0053] Referring to Figs. 7-8, the device 100 of Figs. 1-6 can alternatively be arranged with longitudinal axis 103 horizontally, resulting in the device 200. The flow of the gaseous stream through the inflow duct 210 consequently occurs along a substantially horizontal direction 95, from the inlet port 11 to the outlet port 12. In the first and second outflow ducts 20, 30, the gaseous stream that is split up will equally flow horizontally, although in opposite direction. The inflow duct 210 and the first and second outflow ducts 20, 30 can advantageously be stacked horizontally, as illustrated in Fig. 8. In such an arrangement it will be appreciated that the outer side walls 13, 14 of the inflow duct 210, as well as the outer side walls 23, 33 of the first and second outflow ducts 20, 30, between which the thermo-electric heat pumps 40 are clamped, are arranged substantially vertically (Fig. 8).

[0054] In such horizontal arrangement, the condensate can advantageously be collected along the length of the inflow duct. Advantageously, the inflow duct 210 comprises a gutter 216 at an underside or bottom wall of the inflow duct for collecting and draining the condensate. The gutter 216 and / or the longitudinal axis 103 can advantageously be arranged along a slight slope, e.g. between 0° and 25° with respect to a horizontal axis. This allows the condensate to be easily conveyed in direction of the inlet port and / or the outlet port, depending on the slope, to a liquid separator 219. The gutter 216 and / or the bottom wall of the inflow duct 210 is advantageously arranged between the outer side walls 13 and 14.

[0055] Referring to Fig. 9, the inflow duct 210 can be provided with a perforated bottom plate 217 configured to drain the condensate through perforations 218. The drained condensate can be collected in a channel that is arranged at the opposite side of the perforated bottom plate 217 and serves as gutter 216, and which in turn conveys the condensate to the liquid separator 219. The inflow duct 210 and the channel (gutter) 216 can form a single integral duct, separated by the perforated bottom plate 217.

[0056] The inflow duct 10, 210 of the previous drawings is advantageously arranged as a single channel, i.e., with a continuous cross section, or as a series of channels that are mutually in fluid communication in the inflow duct. Such an arrangement has the advantage that the inflow duct can easily be made gas tight, resistshigher gas pressures and / or can be manufactured with less material, compared to an arrangement with several separate channels as is the case in EP 3312530.

[0057] Alternatively, particularly the inflow duct 210 can be split in two separate, adjacent channels. By way of example, the inflow duct can consist of two separate modules arranged side-by-side. Each of these channels (modules) is in fluid communication with a respective one of the first and second outflow duct. Consequently, two side-by-side U-shaped structures are obtained, instead of one integral W-structure. In such embodiments, the gaseous stream is split at the inlet port 11 in two parts. The two channels are consequently arranged back to back against each other, along the longitudinal axis. However, the manufacture of such an arrangement has a larger material requirement, although use can be made of pre-fabricated modules.

[0058] Referring to Fig. 10, the devices 100, 200 can be complemented with a pretreatment device 400 to obtain an assembly 300 for drying a gaseous stream. The pretreatment device 400 can be arranged upstream from the devices 100, 200. The pretreatment device can be configured to pre-cool the gaseous stream supplied to the inflow duct 10, 210 and / or to further heat the streams 91 , 92 drained from the outflow ducts 20, 30.

[0059] The pretreatment device 400 can comprise a passive heat exchanger 410, that is advantageously configured to exchange heat between the entering stream 90 and the exiting stream 93 created by joining the streams 91 and 91 from the first and second outflow ducts. Such heat exchanger 410 advantageously comprises a third duct 411 and a fourth duct 412 and is configured to transfer heat between the third duct and the fourth duct. The third duct 411 comprises a third inlet port 413 and a third outlet port 414 and the fourth duct 412 comprises a fourth inlet port 415 and a fourth outlet port 416. The third outlet port 414 is in fluid communication with the first inlet port 11. The fourth inlet port 415 is in fluid communication with the two outlet ports 22, 32 of the first and second outflow ducts.

[0060] In addition, or alternatively, the pretreatment device 400 can comprise an active heat exchanger 420, that is advantageously configured to exchange heat between the entering stream 90 and a heat transfer fluid 421 , advantageously by means of a thermo-electric heat pump 440. The heat transfer fluid 421 can be a gaseous stream, such as ambient air, but is advantageously a liquid, such as water. The heat Q3 transferred to the heat transfer fluid can be transferred to ambient atmosphere in a subsequent heat exchange stage, or can be used as process heat.

[0061] Advantageously, the active heat exchanger 420 is configured according to a same structure as the devices 100, 200, particularly the heat transfer fluidis conveyed through ducts that are arranged on both sides of the duct of the entering stream 90. Referring to Fig. 11 , such an active heat exchanger comprises a central duct 422 for conveying the stream 90 (entering gaseous stream) and one or more peripheral ducts 423, 424 that are arranged on a circumference, e.g. on both sides, of the central duct 422. The central duct 422 has an inlet port 425 and an outlet port 426. Outlet port 426 is in fluid communication with the first inlet port 11 of the inflow duct 10, 210. The heat transfer fluid 421 is configured to flow through the peripheral ducts. The direction of flow of the heat transfer fluid 421 through the peripheral ducts 423, 424 can be countercurrent or concurrent with the direction of flow of stream 90 through the central duct 422. Thermo-electric heat pumps 440 are arranged along the circumference (e.g., on both sides) of the central duct 422, in thermal contact with the central duct 422 on one side (e.g., cold side) and with a respective one of the peripheral ducts 423, 424 on an opposite side (e.g., hot side). As a result, the thermo-electric heat pumps 440 are configured to transfer heat between the central duct 422 (stream 90) and the respective peripheral duct 423, 424. The thermo-electric heat pumps 440 are consequently clamped between the central duct 422 and the peripheral ducts 423, 424.

[0062] The pretreatment device 400 can increase the efficiency of the device 100, 200 by providing an appropriate pretreatment of the gaseous stream 90. An optimal efficiency increase is obtained by providing a pretreatment device with both a passive heat exchanger 410 and an active heat exchanger 420.

[0063] Referring to Fig. 10, the devices 100, 200 advantageously comprise a control unit 450 operably connected to the thermo-electric heat pumps 40. The devices 100, 200 can further comprise one or more measurement devices 451 operably connected to the control unit 450. The measurement device 451 can be configured to measure a quantity of the gaseous stream, such as one or more of temperature, pressure, flow rate and relative humidity. In addition, or alternatively, the measurement device can be configured to measure an operational quantity of the thermo-electric heat pumps, such as one or more of electrical voltage and electrical current. Advantageously, the control unit 450 is configured to control the thermo-electric heat pumps 40 on the basis of measurements of the measurement device 451 . Advantageously, measurement device 451 is configured to measure the temperature of the stream 90 at the outlet port 12 of the inflow duct 10, 210 and feed it back to the control unit 450. Based on this temperature, the control unit can control the voltage across and / or the current through the thermo-electric heat pumps 40, e.g., on the basis of a proportional, integral and / or derivative controller, such as a PID-controller. Although not required, the thermo-electric heat pumps 440 of the pretreatment unit’s active heat exchanger 420 can also beconnected to the control unit 450, or be operated through a separate control unit. This is however no requirement and the thermo-electric heat pumps 440 can be operated without specific control in the alternative.

[0064] In an application example, the devices of the present disclosure are utilized for drying compressed air. The compressed air is supplied by a compressor and can e.g. be applied for operating pneumatic tools. The devices of the present disclosure can dry the compressed air supplied by the compressor. In an application example, a compressor supplies compressed air at a pressure between 5 bar and 9 bar and a temperature between 30°C and 40°C with a relative humidity that can approach 100%. The pretreatment device 400 can be configured to cool the compressed air to a temperature between 10°C and 25°C. The devices 100, 200 are configured to receive the compressed air from the pretreatment device at a temperature between 10°C and 25°C, advantageously between 12°C and 18°C and to deliver it at a temperature between 16°C and 23°C (at the outlet port 81). The pretreatment device 400 can further be configured to further heat up this exiting stream 93 to a temperature between 25°C and 34°C, e.g. by means of the passive heat exchanger 410. The temperature at the outlet port 12 of the inflow duct 10, 210 can be an important control parameter to control the drying power. This temperature is advantageously set to a temperature lower than the dew point of the compressed air throughout the inflow duct. In practice, the temperature at the inlet port 12 will typically be set to a temperature between 2°C and 8°C, advantageously between 3°C and 5°C. This ensures a sufficient degree of drying of the air and avoids condensation in the pneumatic tools in which the compressed air is applied.

[0065] It will be appreciated that devices according to aspects of the present invention can comprise more than two outflow ducts, depending on the geometry if the inflow duct. By way of example, the inflow duct can have a triangular cross section, such that thermo-electric heat pumps and respective outflow ducts can be arranged on three sides of the triangle. Similarly, heat transfer through thermo-electric heat pumps and respective outflow ducts can be provided on four sides of a rectangular cross section of the inflow duct.

Claims

CLAIMS1. Device (100, 200) for drying a gaseous stream, comprising: an inflow duct (10, 210) having a first inlet port (11) at a first end (101) and a first outlet port (12) at a second end (102), a first outflow duct (20) and a second outflow duct (30), each having a second inlet port (21 , 31) at the second end (102) and a second outlet port (22, 32) at the first end (101), wherein the inflow duct and the first and second outflow ducts are arranged substantially parallel to one another along a longitudinal axis (103) defining a direction of flow through the inflow duct and the first and second outflow ducts between the first end (101) and the second end (102), thermo-electric heat pumps (40) configured to transfer heat from the inflow duct (10, 210) to a respective one of the first and the second outflow ducts (20, 30), wherein the inflow duct is arranged between the first and the second outflow ducts such that at least a first one (43, 44) of the thermo-electric heat pumps is arranged between a fist wall (13) of the inflow duct and a wall (23) of the first outflow duct and at least a second one (41 , 42) of the thermo-electric heat pumps is arranged between a second wall (14) of the inflow duct and a wall of the second outflow duct, a manifold (50) in fluid communication with the first outlet port (12) and with each of the second inlet ports (21 , 31), wherein the manifold is configured to split the gaseous stream of the inflow duct in multiple substreams, the multiple substreams comprising a first substream conveyed to the first outflow duct and a second substream conveyed to the second outflow duct, wherein the manifold (50) is configured to allow the gaseous stream to flow through the first and the second outflow ducts (20, 30) in countercurrent flow with respect to the inflow duct (10, 210), and a liquid separator (70, 219) configured to separate condensate that is formed in the inflow duct.

2. Device according to claim 1 , further comprising a clamping device (60) configured to clamp the inflow duct (10, 210) and the thermo-electric heat pumps (40) between the first and the second outflow ducts (20, 30).

3. Device according to any one of the preceding claims, wherein the thermoelectric heat pumps (40) are each configured to have a hot side and a cold side, wherein the cold side is in thermal contact with the inflow duct (10, 210) and the hot side is in thermal contact with the respective one of the first and the second outflow ducts (20, 30).

4. Device according to any one of the preceding claims, configured such that the longitudinal axis (103) is substantially arranged at an angle between 0° and 25° with respect to a horizontal axis.

5. Device according to the preceding claim, wherein the thermo-electric heat pumps (40) are arranged between substantially vertically arranged walls of the inflow duct (210) and of a respective one of the first and the second outflow duct (20, 30).

6. Device according to claim 4 or 5, wherein the inflow duct (210) comprises a gutter (216) arranged between the first inlet port and the first outlet port, wherein the gutter is configured to collect condensed liquid.

7. Device according to any one of the claims 4 to 6, wherein the inflow duct (210) comprises a perforated wall (217) extending between the first inlet port and the first outlet port, wherein the perforated wall is configured to drain condensate through perforations (218).

8. Device according to the preceding claim, wherein the inflow duct (210) comprises a gutter (216) arranged underneath the perforated wall for collecting condensate.

9. Device according to any one of the preceding claims, wherein a hydraulic radius of the inflow duct (10, 210) is larger than a hydraulic radius of the first and the second outflow ducts (20, 30), wherein the hydraulic radius is defined as a ratio of a free cross sectional area of the respective duct for the gaseous stream to a wet cross sectional circumference of the respective duct.

10. Device according to any one of the preceding claims, further comprising a control unit (450), wherein the control unit is configured to control the thermo-electric heat pumps (40) on the basis of a quantity of the gaseous stream, preferably further comprising a measurement unit (451) configured to perform a measurement representative of the quantity of the gaseous stream and operably connected to the control unit (450), preferably wherein the quantity is a temperature.

11. Assembly (300), comprising the device according to any one of the preceding claims and a pretreatment part (400), wherein the pretreatment part comprises at least one heat exchanger (410, 420) configured to withdraw heat from the gaseous stream before applying the gaseous stream to the first inlet port (11).

12. Assembly according to the preceding claim, wherein the at least one heat exchanger comprises a first heat exchanger (410), wherein the first heat exchanger comprises a third duct (411) and a fourth duct (412) and is configured to transfer heat between the third duct and the fourth duct, wherein the third duct comprises a third inlet port (413) and a third outlet port (414) and the fourth duct comprises a fourth inlet port (415) and a fourth outlet port (416), wherein the third outlet port (414) is in fluid communication with the first inlet port (11) and the fourth inlet port (415) is in fluid communication with the second outlet ports (22, 32) of the first and second outflow ducts.

13. Assembly according to the preceding claim, wherein the first heat exchanger (410) is a passive heat exchanger.

14. Assembly according to any one of the claims 11 to 13, wherein the at least one heat exchanger comprises a second heat exchanger (420) configured to transfer heat from the gaseous stream to a heat transfer fluid, and wherein the second heat exchanger comprises a fifth duct (422) having a fifth inlet port (425) and a fifth outlet port (426), wherein the fifth outlet port (426) is in fluid communication with the first inlet port (11).

15. Assembly according to the preceding claim, wherein the second heat exchanger (420) is an active heat exchanger.

16. Assembly according to claim 14 or 15, wherein the second heat exchanger (420) comprises a thermo-electric heat pump (440).

17. Assembly according to any one of the claims 14 to 16, wherein the heat transfer fluid is a liquid.

18. Assembly according to any one of the claims 14 to 17, wherein the second heat exchanger (420) comprises a sixth duct (423) and a seventh duct (424), wherein the fifth duct (422) is arranged between the sixth duct (423) and the seventh duct (424) such that walls of the fifth duct (422) are arranged opposite a respective wall of the sixth and the seventh ducts, and wherein the second heat exchanger is configured to allow the heat transfer fluid to flow through the sixth and the seventh ducts.

19. Use of the device or the assembly according to any one of the preceding claims for drying air.

20. Use according to the preceding claim, wherein the air is compressed air, preferably wherein the compressed air has a pressure of at least 4 bar at the first inlet port, preferably at least 5 bar.

21. Use according to the preceding claim, wherein the device is controlled such that the compressed air has a temperature between 2° C and 8°C at the first inlet port (12).

22. Method for drying a gaseous stream, comprising: supplying the gaseous stream (90, 95) through an inflow duct (10, 210), dividing the gaseous stream (90, 95) egressing from the inflow duct into at least two streams (91 , 92) and conveying the at least two streams through respective outflow ducts (20, 30) in countercurrent flow with respect to the inflow duct, wherein the inflow duct and the respective outflow ducts are arranged substantially parallel to one another along a longitudinal axis (103) defining a direction of flow through the inflow duct and the respective outflow ducts, actively transferring heat (Qi) of the gaseous stream (90, 95) from the inflow duct to the at least two streams (91 , 92) in the outflow ducts by means of thermo-electric heat pumps (40) arranged between the inflow duct and each of the outflow ducts, andseparating a condensate (71) formed in the inflow duct.

23. Method according to the preceding claim, further comprising clamping the inflow duct (10, 210) and the thermo-electric heat pumps (40) between the outflow ducts (20, 30).

24. Method according to claim 22 or 23, wherein the gaseous stream is air, preferably compressed air.

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