HEAT EXCHANGER AND METHOD FOR MANUFACTURING SUCH A HEAT EXCHANGER

Abstract

A heat exchanger with a housing (3) that contains a set of channels (12); an inlet collector (4) having an inlet collector chamber (9) with an inlet (5), wherein the inlet collector chamber (9) includes first flow distribution means (10) configured to distribute a flow originating from the inlet (5) evenly over the set of channels (12); and an outlet collector (6). The first flow-rate distribution means (10) consist of a single body (15) that comprises two flow-conducting surfaces (16), which are symmetrical with respect to each other according to the first plane of symmetry and the second plane of symmetry, and which two flow-conducting surfaces (16), as seen from the inlet (5), are inclined downward in a first direction perpendicular to the first plane of symmetry and/or in a second direction perpendicular to the second plane of symmetry.

Claims

1-20. (canceled)

21. A heat exchanger for exchanging heat between two fluids, respectively a first initially two-phase fluid and a second fluid, the heat exchanger comprising: a housing (3) that encloses an internal cavity; a set of channels (12), where each one of the channels (12) in said set passes through the internal cavity of the housing (3); an inlet collector (4) comprising a wall with an inlet (5) for the first initially two-phase fluid, which inlet (5) is in fluid communication with an inlet collector chamber (9) within the inlet collector (4), where both the inlet (5) and the inlet collector chamber (9) are symmetrical in planes of symmetry according to a first plane of symmetry and a second plane of symmetry intersecting said first plane of symmetry, the inlet collector (4) being hermetically connected to the housing (3) on one side of the inlet collector (4) disposed opposite the wall with the inlet (5), and where the inlet collector chamber (9) comprises first flow-rate distribution means (10) configured to distribute a first initially two-phase fluid flow originating from the inlet (5) evenly across the set of channels (12); and an outlet collector (6) comprising a wall with an outlet (7) for the first initially two-phase fluid, which outlet (7) is in fluid communication with an outlet collector chamber (20) in the outlet collector (6), where said outlet collector (6) is hermetically connected to the housing (3) on a side of the outlet collector (6) disposed opposite the wall with the outlet (7), where all inlet orifices (11) of the set of channels (12) are in fluid communication with the inlet collector chamber (9) and all outlet orifices (14) of the set of channels (12) are in fluid communication with the outet collector chamber (20), where the inlet orifices (11) of the channels (12) are symmetrically arranged with respect to each other according to the first plane of symmetry and the second plane of symmetry, wherein the first flow-rate distribution means (10) includes a single body (15) that comprises two flow-conducting surfaces (16), which two flow-conducting surfaces are symmetrical with respect to each other according to the first plane of symmetry and the second plane of symmetry, and which two flow-conducting surfaces (16), as seen from the inlet (5), are inclined downward in a first direction perpendicular to the first plane of symmetry and/or in a second direction perpendicular to the second plane of symmetry, whereby a cross section of the first flow-rate distribution means (10), considered in a plane equal or parallel to the first plane of symmetry or the second plane of symmetry, comprises a substantially full figure formed by the two flow-conducting surfaces (16) and a substantially straight base, the flow-conducting surfaces (16) each being connected by the base at an end situated furthest away from the inlet (5).

22. The heat exchanger according to claim 21, wherein the inlet orifices (11) of the set of channels (12) are arranged in a straight line according to the first direction and symmetrically with respect to each other according to the first plane of symmetry.

23. The heat exchanger according to claim 22, wherein the two flow-conducting surfaces (16) as seen from the inlet (5) only incline downward in the first direction.

24. The heat exchanger according to claim 21, wherein the single body of the first flow-rate distribution means (10) contains a through hole (17) with an axis (18) according to a straight line common to the first plane of symmetry and the second plane of symmetry.

25. The heat exchanger according to claim 21, wherein the inlet collector chamber (9) is bounded by a wall of the inlet collector (4), which wall has a surface (19) facing the inlet collector chamber (9) that stands opposite and substantially parallel to the two flow-conducting surfaces (16).

26. The heat exchanger according to claim 21, wherein each one of the channels (12) in the set of channels (12) has a constant diameter D; and that in a direction common to the first plane of symmetry and the second plane of symmetry, the inlet collector chamber (9) is smaller than 2.0 times the diameter D, preferably smaller than 1.5 times the diameter D, more preferably smaller than 1.0 times the diameter D.

27. The heat exchanger according to claim 21, wherein the cross section of the first flow-rate distribution means (10), considered in a plane equal or parallel to the first plane of symmetry or the second plane of symmetry, comprises a substantially full and substantially isosceles triangle of which the sides of equal length are formed by the two flow-conducting surfaces (16) or comprises a substantially full and substantially isosceles trapezium of which the sides of equal length are formed by the two flow-conducting surfaces (16).

28. The heat exchanger according to claim 21, wherein in the first direction and/or in the second direction a dimension of the inlet (5) is approximately equal to or greater than a dimension of the first flow-rate distribution means (10).

29. The heat exchanger according to claim 21, wherein the outlet collector chamber (20) has a substantially cuboid shape, where the outlet orifices (14) of the channels (12) are in fluid communication with the outlet collector chamber (20) on a first side of the outlet collector chamber (20), and where the outlet (7) is in fluid communication with the outlet collector chamber (20) on a second side of the outlet collector chamber (20) opposite the aforementioned first side of the outlet collector chamber (20).

30. The heat exchanger according to claim 29, wherein each one of the channels (12) in the set of channels (12) has a constant diameter D; and that a perpendicular distance between the aforementioned first side and the aforementioned second side is at least 1.0 times the diameter D, preferably at least 1.5 times the diameter D, with greater preference 2.0 times the diameter D, with still greater preference at least 3.0 times the diameter D.

31. The heat exchanger according to claim 21, wherein the heat exchanger further comprises an intermediate collector (8) between the inlet collector (4) and the outlet collector (6), which intermediate collector (8) is provided with second flow-rate distribution means (21) configured such that a flow of the first initially two-phase fluid in a channel in the set of channels (12) can be at least partially diverted from this channel to and into another channel of the set of channels (12).

32. A refrigeration dryer for cooling and dehumidifying a gas compressed in a compressor installation, which refrigeration dryer comprises a heat exchanger according to claim 21.

33. A ,method for manufacturing a heat exchanger for exchanging heat between two fluids, a first initially two-phase fluid and a second fluid, respectively, where the following components are integrated into the heat exchanger: a housing (3) that encloses an internal cavity; a set of channels (12), where each one of the channels (12) in said set passes through the internal cavity of the housing (3); an inlet collector (4) comprising a wall with an inlet (5) for the first initially two-phase fluid, which inlet (5) is in fluid communication with an inlet collector chamber (9) within the inlet collector (4), where both the inlet (5) and the inlet collector chamber (9) are symmetrical in planes of symmetry according to a first plane of symmetry and a second plane of symmetry intersecting said first plane of symmetry, the inlet collector (4) being hermetically connected to the housing (3) on one side of the inlet collector (4) disposed opposite the wall with the inlet (5), and where the inlet collector chamber (9) comprises first flow-rate distribution means (10) to distribute a first initially two-phase fluid flow originating from the inlet (5) evenly across the set of channels (12); and an outlet collector (6) comprising a wall with an outlet (7) for the first initially two-phase fluid, which outlet (7) is in fluid communication with an outlet collector chamber (20) in the outlet collector (6), where said outlet collector (6) is hermetically connected to the housing (3) on a side of the outlet collector (6) disposed opposite the wall with the outlet (7), where all inlet orifices (11) of the set of channels (12) are connected in fluid connection to the inlet collector chamber (9) and all outlet orifices (14) of the set of channels (12) are connected in fluid connection to the outlet collector chamber (20), where the inlet orifices (11) of the channels (12) are symmetrically arranged with respect to each other according to the first plane of symmetry and the second plane of symmetry, wherein the first flow-rate distribution means (10) includes a single body (15) comprising two flow-conducting surfaces (16) which are symmetrical with respect to each other according to the first plane of symmetry and the second plane of symmetry, and which, as seen from the inlet (5), incline downward in a first direction perpendicular to the first plane of symmetry and/or in a second direction perpendicular to the second plane of symmetry, whereby a cross section of the first flow-rate distribution means (10), considered in a plane equal or parallel to the first plane of symmetry or the second plane of symmetry, comprises a substantially full figure formed by the two flow-conducting surfaces (16) and a substantially straight base, the flow-conducting surfaces (16) each being connected by the base at an end situated furthest away from the inlet (5).

34. The method according to claim 33, wherein the inlet (5) is implemented with, in the first direction and/or in the second direction, a dimension which is almost equal to or greater than a dimension of the first flow-rate distribution means (10).

35. The method according to claim 34, wherein the inlet collector (4) is manufactured integrally with the first flow-rate distribution means (10) by means of a machining technique.

36. The method according to claim 34 for manufacturing a heat exchanger.

Description

[0103] With a view to better demonstrating the features of the invention, a number of preferred embodiments of a heat exchanger in accordance with the invention are hereafter, by way of example without any restrictive character, shown below, as well as of an inlet collector and outlet collector for use in such a heat exchanger, with reference to the accompanying figures, in which:

[0104] FIG. 1 shows a conventional refrigeration dryer according to the known prior art;

[0105] FIG. 2 shows a refrigeration dryer with a heat exchanger according to the invention;

[0106] FIG. 3a shows a heat exchanger with an open view of an inlet collector according to the invention;

[0107] FIG. 3b shows the heat exchanger in FIG. 3a with an open view of an outlet collector according to the invention;

[0108] FIG. 4a shows an isometric view of an inlet collector according to the invention;

[0109] FIG. 4b shows a view of the inlet collector in FIG. 4a according to a direction perpendicular to the inlet of the inlet collector;

[0110] FIG. 4c shows a view of the inlet collector in FIG. 4a according to an intersection A-A in FIG. 4b;

[0111] FIG. 5a shows an isometric view of an outlet collector according to the invention;

[0112] FIG. 5b shows a view of the outlet collector in FIG. 5a according to a direction perpendicular to the outlet of the outlet collector;

[0113] FIG. 5c shows a view of the inlet collector in FIG. 5a according to an intersection C-C in FIG. 5b;

[0114] FIG. 6 shows an isometric view of an intermediate collector according to the invention;

[0115] FIG. 7 shows a temperature distribution of dried compressed air in a housing of the conventional heat exchanger in FIG. 1;

[0116] FIGS. 8a-d show a temperature distribution of dried compressed air in a housing of a heat exchanger according to four variants of the invention;

[0117] FIG. 9 shows a temperature distribution of dried compressed air in a housing of a heat exchanger according to the fourth variant of the invention in FIG. 8d at low airflow rates.

[0118] The conventional refrigeration dryer 1′ in FIG. 1 for drying compressed air from a compressor plant comprises a heat exchanger 2′ with a housing 3′ enclosing an internal cavity and a set of channels, each of the channels in this set passing through the housing 3′, the internal cavity and again through the housing 3′.

[0119] The air to be dried flows in the internal cavity across the channels. Said compressed air to be dried is cooled by sending an initially two-phase cooling agent through the channels. Said initially two-phase cooling agent evaporates as it passes through these channels due to heat exchange with the compressed air in the internal cavity around the channels.

[0120] The heat exchanger 2′ further comprises an inlet collector 4′ with a side inlet 5′ for the initially two-phase cooling agent. The inlet collector 4′ is hermetically attached to the housing 3′ across all inlet orifices of the channels. In this way, the inlet orifices of the channels are in fluid communication with an inlet collector chamber in the inlet collector 4′, which inlet collector chamber collects a flow of the initially two-phase cooling agent that enters the inlet collector 4′ via the side inlet 5′.

[0121] The inlet collector chamber may have a distribution pipe, a structured medium or inserts to distribute the initially two-phase cooling agent entering the inlet collector 4′ via the side inlet 5′ uniformly across the set of channels.

[0122] Furthermore, the heat exchanger 2′ comprises an outlet collector 6′ with an outlet 7′ for the initially two-phase cooling agent. The outlet collector 6′ is hermetically attached to the housing 3′ across all outlet orifices of the channels. In this way, the outlet orifices of the channels are in fluid communication with an outlet collector chamber in the outlet collector 6′, which outlet collector chamber collects flows of the initially two-phase cooling agent that enters the outlet collector 6′ via the outlet orifices of the channels. The initially two-phase cooling agent can then leave the outlet collector 6′ via the outlet 7′.

[0123] The refrigeration dryer 1 according to the invention in FIG. 2 comprises, analogously to the conventional refrigeration dryer 1′ in FIG. 1, a heat exchanger 2 with a housing 3 enclosing an internal cavity and a set of channels, each of the channels in this set passing through the housing 3, then the internal cavity and again through the housing 3.

[0124] An inlet collector 4 of the heat exchanger 2 has an inlet 5 for an initially two-phase cooling agent. In this case, this inlet 5 is centrally located opposite the inlet orifices of the channels, which in itself ensures a more uniform distribution of a flow of initially two-phase cooling agent entering through said inlet 5 than would be the case with a side inlet 5′ such as in the heat exchanger 2′ of the conventional refrigeration dryer 1′ in FIG. 1.

[0125] Similarly, an outlet 7 of an outlet collector 6 of the heat exchanger 2 is centrally located opposite the outlet orifices of the channels, which offers an analogous advantage in comparison with the side outlet 7′ such as in the heat exchanger 2′ of the conventional refrigeration dryer 1′ in FIG. 1.

[0126] Optionally, the heat exchanger 2 is also equipped with an intermediate collector 8 for levelling pressure levels in the set of channels between the inlet collector 4 and the outlet collector 6.

[0127] FIG. 3a shows the heat exchanger 2 in FIG. 2 with an open view of the inlet collector 4, and FIG. 3b shows the heat exchanger 2 in FIG. 2 with an open view of the outlet collector 6.

[0128] In the inlet collector chamber 9 first flow-rate distribution means 10 are disposed which distribute and direct the flow of the initially two-phase cooling agent entering the inlet collector 4 through the inlet 5 to the inlet orifices 11 of the channels 12, which channels 12 pass through the internal cavity enclosed by the housing 3 of the heat exchanger 2 and finally exit through the outlet orifices 14 into the outlet collector 6 with the outlet 7.

[0129] FIG. 4a shows an isometric view of the inlet collector 4 with inlet 5.

[0130] Said inlet 5 is in this case implemented as an elongated slot of which the dimensions, in a direction perpendicular to said inlet 5, are approximately equal to the dimensions of the first flow-rate distribution means 10. As a result, when the inlet collector 4 is produced, the location of the first flow-rate distribution means 10 is easily accessible after said inlet 5 has been formed, so that the first flow-rate distribution means 10 can then be easily formed using a standard machining technique.

[0131] FIG. 4b shows a view of the inlet collector 4 in FIG. 4a according to a direction perpendicular to the inlet 5 of the inlet collector 4, while FIG. 4c shows a view of said inlet collector 4 in FIG. 4a according to an intersection A-A in FIG. 4b.

[0132] Both inlet 5 and inlet collector chamber 9 are symmetrical according to a first plane of symmetry B-B and a second plane of symmetry coinciding with the plane of intersection A-A and intersecting this first plane of symmetry B-B.

[0133] The first flow-rate distribution means 10 consist of a single body 15 comprising two flow-conducting surfaces 16 which are symmetrical with respect to each other according to the first plane of symmetry B-B and the second plane of symmetry A-A, and which two flow-conducting surfaces 16, as seen from the inlet 5, incline downward in a first direction R1 perpendicular to the first plane of symmetry and/or in a second direction R2 perpendicular to the second plane of symmetry.

[0134] In this case, the single body 15 of the first flow-rate distribution means 10 is implemented with a cross section which, considered in a plane equal or parallel to the plane of intersection A-A, comprises a substantially full and substantially isosceles triangle of which the sides of equal length are formed by the two flow-guide surfaces 16.

[0135] It would not be excluded in the scope of the invention that alternatively or similarly a cross section, considered in a plane equal or parallel to the intersection plane B-B, would include a substantially full and substantially isosceles triangle of which the sides of equal length were formed by the two flow-conducting surfaces.

[0136] It would not be excluded in the scope of the invention that alternatively or similarly a cross-section, considered in a plane equal or parallel to the intersection plane B-B, would include a substantially full and substantially isosceles triangle of which the sides of equal length were formed by the two flow-conducting surfaces.

[0137] The inlet orifices 11 of the channels formed by the set of channels 12 are arranged in a straight line according to the first direction R1 and symmetrically with respect to each other according to the first plane of symmetry B-B.

[0138] In the context of the invention, however, it cannot be excluded that the inlet orifices of the set of channels are arranged symmetrically with respect to each other in some other way according to the first plane of symmetry and the second plane of symmetry, for example when the inlet orifices are disposed at a regular distance on concentric circles or when the inlet orifices are positioned according to a pattern corresponding to grid points of a rectangular grid or a hexagonal honeycomb grid.

[0139] The single body 15 of the first flow-rate distribution means 10 may optionally include a through-hole 17 having an axis 18 according to a straight line common to the first plane of symmetry B-B and the second plane of symmetry A-A.

[0140] The inlet collector 4 includes a wall delimiting the inlet collector chamber 9, which wall has a surface 19 facing the inlet collector chamber 9 that is opposite and substantially parallel to the two flow-conducting surfaces 16. This allows a velocity of the initially two-phase cooling agent entering the inlet collector chamber 9 along inlet 5 to be maintained, which reduces the likelihood of liquid particles from the initially two-phase cooling agent precipitating against walls delimiting the inlet collector chamber 9, whereby these liquid particles remain better dispersed in the initially two-phase cooling agent.

[0141] In order to keep the velocity of the initially two-phase cooling agent as high as possible, a dimension of the inlet collector chamber 9 in a direction common to the first plane of symmetry B-B and the second plane of symmetry A-A is best chosen as small as possible, typically smaller than 2.0 times the diameter D of the channels formed by the set of channels 12.

[0142] FIG. 5a shows an isometric view of the outlet collector 6 with outlet 7.

[0143] FIG. 5b shows a view of the outlet collector 6 in FIG. 5a according to a direction perpendicular to the outlet 7 of the outlet collector 6, while FIG. 5c shows a view of the outlet collector 6 in FIG. 5a according to an intersection C-C in FIG. 5b.

[0144] The outlet collector chamber 20 has a substantially cuboid shape, where the outlet orifices 14 of the channels 12 are in fluid communication with the outlet collector chamber 20 on a first side of the outlet collector chamber 20 and where the outlet 7 is in fluid communication with the outlet collector chamber 20 on a second side of the outlet collector chamber 20 opposite the aforementioned first side of the outlet collector chamber 20.

[0145] To create a uniform outflow of the first initially two-phase cooling agent in the outlet collector chamber 20, a perpendicular distance between the aforementioned first side and the aforementioned second side is best chosen large enough, typically minimally 1.0 times the diameter D of the ducts.

[0146] FIG. 6 shows an isometric view of an intermediate collector 8 according to the invention.

[0147] Second flow-rate distribution means 21 are formed by an internal cavity 22 in the intermediate collector 8 configured such that a flow of the initially two-phase cooling agent in a channel in the set of channels 12 can be at least partially diverted from this channel to and into another channel of the set of channels 12. This allows pressure levels in the channels formed by the set of channels 12 to be equalized.

[0148] The inlet collector, outlet collector and intermediate collector described above can be produced in a simple and inexpensive way using a machining technique compared to more advanced techniques such as additive manufacturing.

COMPARATIVE EXAMPLE

[0149] As shown in FIG. 1, a FD 1010 VSD refrigeration dryer made by Atlas Copco Airpower was used to test a standard eight-row heat exchanger 1629 1926 00 made by AKG Thermotechnik to cool and dehumidify a flow rate of 1010 l/s, 750 l/s and 500 l/s of ambient air at an initial temperature of 25° C., which ambient air is brought to an overpressure of 7 barg and enters the heat exchanger at a temperature of 35° according to the conditions of ISO standard no. 7183 option A1. 7183 option A1.

[0150] In FIG. 7 a distribution is shown of a temperature of dried compressed air around all channels in the housing of the heat exchanger, measured at positions a to i, as a function of the flow rate of ambient air. In this case, the temperature of the dried compressed air is controlled to a setpoint of 3.0° C. according to ISO standard no. 8573-1 class 4 under test conditions of ISO standard no. 8573-3.

[0151] This setpoint is represented in FIG. 7 by a long-dashed line. The distribution of the temperature of dried compressed air is shown as [0152] a solid line with circular symbols for an ambient airflow rate of 1010 l/s; [0153] a short-dashed line with square symbols for an ambient airflow rate of 750 l/s; and [0154] a dotted line with rhombic symbols for an ambient airflow rate of 500 l/s.

[0155] In a water separator behind the heat exchanger, two measurements of the LAT are further carried out: a “LAT left” measurement at position j and a “LAT right” measurement at position k.

[0156] Finally, the dew point of the compressed air and the evaporation temperature of the initially two-phase cooling agent are determined.

[0157] This leads to the following measurement results:

TABLE-US-00001 airflow rate 1010 l/s 750 l/s 500 l/s LAT left-LAT right(° C.) 2.0, 3.7 1.8, 3.6 1.2, 4.0 PDP (° C.) 3.1 3.3 2.8 Tevap (° C.) −3.0 −2.1 −2.1

[0158] In this case, two parameters can be identified as performance indicators of the heat exchanger: [0159] a maximum value for the temperature difference “ΔTair” between a warmest and a coldest temperature of the dried air around the channels in the housing of the heat exchanger, in this case 9.8° C., 10.0° C. and 11.0° C. for an air flow rate of 1010 l/s, 750 l/s and 500 l/s respectively; and [0160] a proximity or approach, which is a temperature difference between the dew point PDP and the evaporation temperature Tevap, in this case 6.1° C., 5.4° C. and 4.9° C. for an air flow rate of 1010 l/s, 750 l/s and 500 l/s respectively.

[0161] Due to low temperatures of the dried compressed air at positions d to h, there is a risk that the heat exchanger would partially freeze there if the evaporation temperature of the cooling agent were to be further lowered by a pressure drop of the cooling agent, especially at low air flows. For this reason and because of high temperatures at positions a and b, a desired average temperature for the dried compressed gas of 3° C. cannot be achieved.

Examples 1 to 4

[0162] Example 1 differs from the comparative example in that the inlet collector of the heat exchanger is replaced by an inlet collector with first flow-rate distribution means according to the invention as shown in FIG. 4a-4c.

[0163] FIG. 8a shows for Example 1 the distribution of the temperature of dried compressed air around all channels in the housing of the heat exchanger, measured at positions a to i. This distribution is shown as a solid line with triangular symbols. The setpoint of 3.0° C. is represented by a long-dashed line.

[0164] Example 2 differs from the comparative example both in that the inlet collector of the heat exchanger is replaced by an inlet collector with first flow-rate distribution means according to the invention as shown in FIG. 4a-4c, and in that the outlet collector is replaced by an outlet collector according to the invention as shown in FIG. 5a-5c.

[0165] FIG. 8b shows for Example 2 the distribution of the temperature of dried compressed air around all channels in the housing of the heat exchanger, measured at positions a to i. This distribution is shown as a solid line with triangular symbols. The setpoint of 3.0° C. is represented by a long-dashed line.

[0166] In Example 3, in the comparative example, the inlet collector of the heat exchanger is replaced by an inlet collector with first flow-rate distribution means according to the invention as shown in FIG. 4a-4c, and an intermediate collector according to the invention as shown in FIG. 6 is incorporated in the heat exchanger.

[0167] FIG. 8c shows for example 3 the distribution of the temperature of dried compressed air around all channels in the housing of the heat exchanger, measured at positions a to i. This distribution is shown as a solid line with triangular symbols. The setpoint of 3.0° C. is represented by a long-dashed line.

[0168] In Example 4, in the comparative example, the inlet collector of the heat exchanger is replaced by an inlet collector with first flow-rate distribution means according to the invention as shown in FIG. 4a-4c, the outlet collector is replaced by an outlet collector according to the invention as shown in FIG. 5a-5c, and an intermediate collector according to the invention as shown in FIG. 6 is incorporated in the heat exchanger.

[0169] FIG. 8d shows, for Example 4, the distribution of the temperature of dried compressed air around all channels in the housing of the heat exchanger, measured at positions a to i. This distribution is shown as a solid line with triangular symbols. The setpoint of 3.0° C. is represented by a long-dashed line.

[0170] This leads to the following measurement results at an airflow rate of 1010 l/s for the various examples 1 to 4:

TABLE-US-00002 Example 1 2 3 4 LAT left-LAT right(° C.) 3.0-3.1 3.0-3.1 3.1-3.3 3.3-3.4 PDP (° C.) 3.2 2.8 3.1 3.7 Tevap (° C.) −1.7 −1.6 −0.9 −0.9

[0171] Consequently, the proximity between the dew pressure and the evaporation temperature in examples 1 to 4 is equal to 4.9° C., 4.4° C., 4.0° C. and 4.6° C. respectively.

[0172] The maximum value for the temperature difference ‘ΔTair’ for Examples 1 to 4 is equal to 4.4° C., 4.3° C., 3.2° C. and 3.1° C. respectively.

Example 5 and 6

[0173] A refrigeration dryer with the heat exchanger according to Example 4 is also tested at low airflow rates: an airflow rate of 750 l/s in Example 5 and an airflow rate of 500 l/s in Example 6.

[0174] FIG. 9 shows for Examples 5 and 6 the distribution of the temperature of dried compressed air around all channels in the housing of the heat exchanger, measured at positions a to i.

[0175] The setpoint of 3.0° C. is shown in FIG. 9 by a long-dashed line. The distribution of the temperature of dried compressed air is shown as [0176] a solid line with circular symbols for an ambient airflow rate of 1010 l/s; [0177] a short-dashed line with square symbols for an ambient airflow rate of 750 l/s; and [0178] a dotted line with rhombic symbols for an ambient airflow rate of 500 l/s.

[0179] Measurement results for Examples 5 and 6 are summarized in the table below:

TABLE-US-00003 Example 4 5 6 LAT left-LAT right(° C.) 3.3-3.4 3.2-3.3 1.9-2.1 PDP (° C.) 3.7 3.7 2.4 Tevap (° C.) −0.9 0.9 0.3 Proximity (° C.) 4.6 2.8 2.1

[0180] When the proximities in Examples 4 to 6 are compared with the proximities in the comparative example, it can be concluded that for the same airflow rate the proximities in Examples 4 to 6 are smaller than those in the comparative example. Furthermore, a decrease in the proximity at the low airflow rates in Examples 5 and 6 with respect to the proximity in example 4 is greater than the decrease that occurs at the low airflow rates in the comparative example.

[0181] The smaller the proximity, the greater the heat transfer between the initially two-phase cooling agent and the compressed air, and the more energy-efficient the refrigeration dryer operates as a result.

[0182] The improved smaller proximities in Examples 4 to 6 can be explained by a more uniform distribution of the temperatures of dried compressed air around all channels in the housing of the heat exchanger, as a result of which said temperatures can be controlled closer to the setpoint of 3.0° C. without running the risk of one of these temperatures becoming too low so that the heat exchanger would freeze up.

[0183] The maximum value for the temperature difference ‘ΔTair’ for Examples 5 to 6 is equal to 1.8° C. and 1.1° C. respectively.

[0184] The present invention is by no means limited to the embodiments described as examples and shown in the figures, but a heat exchanger according to the invention, an inlet collector and/or an outlet collector for such a heat exchanger, or a refrigeration dryer provided with such a heat exchanger may be implemented in all kinds of variants and/or dimensions without going beyond the scope of protection of the invention according to the claims.