EP2253921A2 - Fin for a heat transferer - Google Patents

Abstract

The rib (2) has a ribbed plate arranged between two structures (1) in a longitudinal direction. A set of gills is provided with gill-depth and a gill-angle with respect to a depth direction of the gills in the ribbed plate. The gills are extended transverse to the depth direction and arranged parallel to each other, where the gill-angle of the grills lies between 14 to 26 degrees. The gill-depth of the grills lies in range of 0.3 mm to 0.6 mm or in range of 1.1 mm to 1.8 mm.

Description

The invention relates to a rib for a heat exchanger according to the preamble of claim 1.

US 2005/0045314 A1 describes ribs for a heat exchanger, in which a corrugated, arranged between flat tubes fin plate is provided to improve the heat transfer with gills.

From the practice of heat exchanger construction, it is also known to provide corrugated ribs with gills, which have a Kiementiefe of 0.9 mm at a gill angle of 27 °.

It is the object of the invention to provide a rib for a heat exchanger, which allows a good heat transfer with low pressure drop.

This object is achieved according to the invention for an aforementioned rib with the characterizing features of claim 1. Investigations have shown the surprising result that, with a suitable choice of the gill angle, both below and above the conventional depth of the kite, there are areas for the kite depth, which allow a particularly large heat transfer at low pressure drop. This favorable property of the rib according to the invention makes it possible, for example, in the case of a radiator for a vehicle interior to provide a lower blower power at the same air flow and the same air heating. In addition, in this exemplary application, the noise generated by blower and air flow is reduced. Further advantages of the invention are generally that an improvement without significant additional costs can be achieved with almost unchanged manufacturing process. The gill angle of a rib according to the invention is between 14 ° and 30 °.

In a preferred embodiment of the invention, the gill angle is between 14 ° and 26 °. This optimized range of the gill angle can be combined with all depths of the girth, and more preferably with small girths of between 0.3 mm and 0.6 mm.

In a preferred embodiment of the invention, the Kiementiefe to further optimize the properties between 0.4 mm and 0.6 mm, more preferably between 0.45 mm and 0.55 mm.

In an alternative embodiment, the Kiementiefe for further optimization between 1.2 mm and 1.6 mm.

A rib density in the longitudinal direction is generally preferably between 70 Ri / dm and 120 Ri / dm. The unit Ri / dm is to be understood as the number of rib flanks given by the corrugation per decimeter. The rib flanks are regularly arranged at an angle to each other to improve the mechanical stability, but can also run parallel to each other depending on requirements.

For ease of production with good effect of the gills, it is provided that a length of the gills KL at least 0.5 mm, in particular between 0.5 mm and 2.0 mm, is smaller than a rib height RH.

Particularly advantageous inventive dimensioning of the gills are used in relatively thin fin sheets, wherein in a preferred embodiment, a material thickness of the fin plate is approximately between 0.06 mm and 0.1 mm.

The inventive dimensioning of the gills is particularly suitable when the multiple gills follow each other directly. This means that between successive ribs no flat web of the remains, so that two gills are separated from each other by means of a single Einschitts in the sheet.

In a generally advantageous embodiment, a first gill group and a second gill group are provided, wherein the gill angles KW of the gill groups have different orientations. Thus, the gaseous fluid is first passed in one direction through the fin plate and subsequently in the opposite direction.

A rib height RH is preferably between 3 mm and 12 mm. In a particularly preferred detailed design, the rib height is between 4 mm and 8 mm.

For use in common designs of heat exchangers, it is provided that a depth of the rib in the depth direction is between 15 mm and 80 mm, preferably between 15 mm and 45 mm.

In another embodiment of the invention, a rib density in the longitudinal direction is not more than about 80 Ri / dm, and in a preferred detail design, the gill angle is at least 26 °. In an alternative embodiment, a rib density in the longitudinal direction is at least about 80 Ri / dm, in particular, the gill angle is not more than about 26 °. Overall, this allows a further optimization of the performance, taking into account the rib density, which can be predetermined depending on the application.

The object of the invention is also achieved for a heat exchanger according to claim 13 by providing a rib according to the invention.

In an advantageous detailed design of the heat exchanger is designed as a heat exchanger of a motor vehicle, in particular as an electric radiator, liquid-operated radiator, evaporator or condenser of a vehicle air conditioning, intercooler or coolant radiator. In motor vehicles, there is a particularly high requirement for the optimization of the heat exchanger performance with a given space. The rib according to the invention is particularly suitable for use with a radiator, since it allows for a given air flow and given temperature difference a particularly small pressure drop. This reduces noise and makes it possible, for example, to make a heating fan particularly small. In the case of a heat exchanger in the form of an electrically operated radiator, the structures are, for example, electric heating elements, preferably PTC heating elements (PTC = Positive Temperature Coefficient). In a possible alternative embodiment of a radiator, the structures may also be flat tubes or round tubes in which, for example, heated coolant flows through an engine cooling circuit.

Further advantages and features of the invention will become apparent from the embodiments described below and from the dependent claims.

Fig. 1

zeigt eine ausschnittsweise Draufsicht auf einen Wärmeübertrager mit erfindungsgemäßen Rippen.

Fig. 2

zeigt eine Ausschnittsvergrößerung der Rippe aus Fig. 1.

Fig. 3

zeigt einen Querschnitt durch die Rippe aus Fig. 1.

Fig. 4

zeigt eine schematische Ausschnittsdarstellung der Rippe aus Fig. 1 zur Definition von Bemaßungen.

Fig. 5

zeigt eine Temperaturdifferenz als Funktion eines luftseitigen Druckabfalls unter Variation von Rippendichte und Kiemenwinkel für eine Kiementiefe von 1,5 mm.

Fig. 6

zeigt eine Temperaturdifferenz als Funktion eines luftseitigen Druckabfalls unter Variation von Rippendichte und Kiemenwinkel für eine Kiementiefe von 0,5 mm.

Fig. 7

zeigt ein Diagramm des Quotienten aus Leistung und luftseitigem Druckabfall als Funktion des Kiemenwinkels für mehrere erfin- dungsgemäße Kiementiefen sowie für einen Stand der Technik.

Hereinafter, several embodiments of the invention will be described and explained in more detail with reference to the accompanying drawings.

Fig. 1

shows a fragmentary plan view of a heat exchanger with ribs according to the invention.

Fig. 2

shows an enlarged detail of the rib Fig. 1 ,

Fig. 3

shows a cross section through the rib Fig. 1 ,

Fig. 4

shows a schematic sectional view of the rib Fig. 1 to define dimensions.

Fig. 5

shows a temperature difference as a function of an air-side pressure drop with variation of rib density and gill angle for a gill depth of 1.5 mm.

Fig. 6

shows a temperature difference as a function of an air-side pressure drop with variation of rib density and gill angle for a depth of 0.5 mm.

Fig. 7

shows a graph of the quotient of power and air-side pressure drop as a function of the gill angle for several inventive Kement depths as well as for a prior art.

The in Fig. 1 shown heat exchanger is a radiator for a motor vehicle. In a known construction, ribs 2 are respectively provided between structures in the form of parallel flat tubes 1, through which a heated coolant of an engine cooling circuit flows, so that overall a heat transfer network through which a gaseous fluid such as air flows is formed. The flow direction of the air extends in the direction of a depth of the heat exchanger perpendicular to the plane of the drawing in Fig. 1 , The flat tubes 1 each open into a bottom 3 of a collector.

A height direction in the sense of the invention runs in the plane of the drawing Fig. 1 from left to right, ie perpendicular to the direction of the flat tubes and to the depth direction. A longitudinal direction in the sense of the invention runs in the plane of the drawing Fig. 1 from top to bottom, ie parallel to the flat tubes. 1

The rib 2 are formed in their construction principle in a known manner as gill corrugated ribs of a corrugated in the longitudinal direction ribbed plate, wherein the individual ribs formed by the corrugation each having a plurality of gills 4. The gills 4 are formed as a set-up opening of the ribbed plate and arranged one behind the other in the depth direction.

According to the illustrations after Fig. 2 to Fig. 4 the gills are formed as a series of directly consecutive in the depth direction, so formed by means of only one incision of the rib sheet each other and angled webs. The installation angle relative to the depth direction is defined as the gill angle KW. The total length of a gill, measured in a plane with the depth direction, is defined as the kite depth KT.

The gills have according to Fig. 2 also a gill length KL, which is slightly smaller than a rib height RH, so that the bending of the ribbed plate is possible. In the present case, the rib height RH also corresponds to the free distance of adjacent flat tubes 1. For preferred rib heights between 3 mm and 12 mm, the gill length KL in optimized form is between 0.5 mm and 2 mm less than the rib height RH.

The number of rib flanks per unit length in the longitudinal direction is defined as the rib density RD (unit: Ri / dm). Preferably, the rib density RD is between 70 and 120 Ri / dm.

The total length of the ribs in the depth direction or flow direction of the air is defined as the rib depth RT and is typically between 15 mm and 80 mm, depending on the requirements.

The sectional view Fig. 3 shows that the gills 4 are provided in the depth direction as two successive gill panels 5.6 of each identical gills, the gill angle of the two fields 5, 6 is the same size, but inverted in the direction. Thus, the air is first passed in one direction and then in the reverse direction through the fin plate.

At the beginning of the first gill field 5 and at the end of the second gill field 6, a respective peripheral girth 5a, 6a is provided, which has only half the height of a normal gill 4 above the plane of the sheet. Between the gill panels 5, 6 a roof gill 7 is provided in each case, which ensures a transfer between the differently directed gill fields 5, 6.

All of the belts 4,5a, 6a, 7 have in each case the same height above the plane of the sheet in all the present exemplary embodiments.

For the purposes of the present invention, calculations and experiments have been carried out in order to optimize the dimensioning of the several identical, arranged one behind the other 4 kiesen, with surprising effects have been shown.

It has been known to produce corrugated ribs of the above-described shape which have the following dimensions: (State of the art:) KT = 0.9 mm KW = 27 ° RH = 4.5mm RT = 26 mm D = 0.08 mm

It has been found that for smaller gill angles in the range of 14 ° to 26 ° both for smaller depths of the kite than in the prior art as well as for larger depths of kings significant improvements in the ratio of heating power to air-side pressure drop can be found.

Fig. 5 shows the results of experiments on different rib densities with variation of the gill angle for a constant depth of girth of 1.5 mm, so a much greater Kiementiefe than in the prior art. In each case an air mass flow MS = 3 kg / min was set. The measured variable is the achieved temperature difference of the air as a function of the pressure drop. The X-shaped mark shows the working point according to the above technique.

Fig. 6 shows that too Fig. 5 analogous results for a Kiementiefe KT = 0.5 mm, so a significantly smaller Kiementiefe than the prior art. The set air mass flow is again 3 kg / min.

Results of the simulations and experiments are in Fig. 7 summarized. Plotted are the quotient of temperature difference (corresponding to heat output) and pressure drop .DELTA.T / .DELTA.p over the gill angle for four different belt depths: 0.5 mm, 0.9 mm (prior art for gill angles of 27 °). 1.2 mm and 1.5 mm. The working point known from the prior art is again in the form of an X-shaped marking located. In the results after Fig. 7 are given an air mass flow of 6 kg / min and a rib height of 4.5 mm.

It is noted that the air mass flow rates set in the experiments and simulations ( Fig. 5 and Fig. 6 : 3 kg / min, Fig. 7 : 6 kg / min) have no relevant influence on the results. This is according to available knowledge at least for a range of air mass flow of 2 kg / min to 6 kg / min and probably beyond.

The results after Fig. 7 show that better values for ΔT / Δp are achieved both for smaller belt depths of 0.5 mm and for larger belt depths of 1.2 mm or 1.5 mm, when the gill angle is in a smaller range compared to the prior art moved from 14 ° to 26 °.

Furthermore, it is possible Fig. 7 It can be seen that, in particular for the variant of the larger belt depth, even for larger gill angles, for example up to 30 °, significantly improved values for ΔT / Δp are achieved in comparison with the prior art.

For these surprising results can be speculated without claim to correctness the explanation that in the case of the small Kement depth of 0.5 mm, the proportion of flowing through the gills or the side of the fin sheet changing air is very low (see also Fig. 8 ). The gills cause primarily an increase in the roughness, so that there is a rupture or detachment of a laminar boundary layer of the air flow. At the same time, the air-side pressure drop is low due to the large number of disturbances and "Neuantäufen" the flow, as through the gills little air flows and the air is thus hardly deflected. The air distribution over the rib is thus very homogeneous. In order to achieve a comparable with the prior art air-side heat transfer, in the variant the small cone depths (0.3 mm to 0.6 mm) slightly increase the rib density, about 10 Ri / dm.

For the large depths of the kite (1.1 mm to 1.8 mm), the explanation for the surprising effect is that due to the large depth of the kite, even at small gill angles (eg 22 °) enough air flows through the gills (see also Fig. 9 ). Due to the small gill angle, the detachments behind each gill are smaller than at large gill angles (27 °, state of the art). The air distribution perpendicular to the flow direction is thereby more homogeneous or it comes to more uniform air velocities.

The Fig. 10 and Fig. 11 show speed profiles for different rib heights, namely 4.5 mm ( Fig. 10 ) and 6 mm ( Fig. 11 ). Clearly visible is the much more homogeneous velocity profile of variants 1 and 2 according to the present invention compared to the prior art.

The above-described preferred embodiments of a fin are applicable to various types of heat exchangers, particularly automobiles, such as coolant coolers, air conditioner evaporators, air conditioner condensers, intercoolers, or the like. Particularly preferred is an application in radiators of a motor vehicle, since the required power of a fan blower can be reduced here by the low pressure drop for a given performance and the overall homogeneous flow through the network. In an embodiment of the invention, not shown, the heat exchanger is designed as an electric heater, wherein the structures 1 are not flat tubes, but PTC elements which are heated by electric current.

Claims (14)

A rib for a heat exchanger, comprising a corrugated sheet (2) which is corrugated in a longitudinal direction and arranged between two structures (1),
wherein the fin plate (2) in a depth direction of a particular gaseous fluid for the transmission of heat between the structures (1) and the gaseous fluid can flow,
and wherein in the ribbed plate (2) a plurality of parallel arranged behind one another, transversely to the depth direction extending gills (4) are provided with a Kement KT and a Kiemenwinkel KW with respect to the depth direction, characterized
that the gill angle KW is between 14 ° and 30 °, in particular between 14 ° and 26 °, wherein the girth KT either in the range of 0.3 mm to 0.6 mm or in the range of 1.1 mm to 1.8 mm is located. Rib according to claim 1, characterized in that the Kiementiefe KT is between 0.4 mm and 0.6 mm, in particular between 0.45 mm and 0.55 mm. Rib according to claim 1, characterized in that the Kiementiefe KT is between 1.2 mm and 1.6 mm. Rib according to one of the preceding claims, characterized in that a rib density in the longitudinal direction is between 70 Ri / dm and 120 Ri / dm. Rib according to one of the preceding claims, characterized in that a length of the gills (4) KL is at least 0.5 mm, in particular between 0.5 mm and 2.0 mm, smaller than a rib height RH. Rib according to one of the preceding claims, characterized in that a material thickness D of the ribbed plate (2) is approximately between 0.06 mm and 0.1 mm. Rib according to one of the preceding claims, characterized in that the plurality of gills (4) follow one another directly. Rib according to one of the preceding claims, characterized in that a first gill group (5) and a second gill group (6) is provided, wherein the gill angles KW of the gill groups (5, 6) have different orientations. Rib according to one of the preceding claims, characterized in that a rib height RH is between 3 mm and 12 mm, in particular between 4 mm and 8 mm. Rib according to one of the preceding claims, characterized in that a depth of the rib RT in the depth direction between 15 mm and 80 mm, in particular between 15 mm and 45 mm. Rib according to one of the preceding claims, characterized in that a rib density in the longitudinal direction is not more than about 80 Ri / dm, wherein in particular the gill angle is at least 26 °. Rib according to one of claims 1 to 10, characterized in that a rib density in the longitudinal direction is at least about 80 Ri / dm, in particular, the gill angle is not more than about 26 °. Heat exchanger comprising a rib according to one of the preceding claims. Heat exchanger according to claim 13, characterized in that the heat exchanger is designed as a heat exchanger of a motor vehicle, in particular as an electric radiator, liquid-operated radiator, evaporator of a vehicle air conditioner, condenser of a vehicle air conditioning, intercooler or coolant radiator.

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