Flow heater with bypass channel

Abstract

A flow heater is disclosed comprising a housing (1) having an inlet (2) and an outlet (3), a flow channel (12) for the flow of liquid to be heated, the flow channel (12) extending from the inlet (2) to the outlet (3), a heating plate (4) arranged as a wall of a heating section of the flow channel. According to the invention a bypass channel (16) is arranged in parallel with the heating section of the flow channel in order to guide any air bubbles contained in the liquid from the inlet (2) to the outlet (3) without passing through the heating section of the flow channel.

Description

[0001] The invention is based on a flow heater having the features specified in the preamble of claim 1, such as the technology known from DE 102017121341 B4.

[0002] Flow heaters are required, for example in automobiles, to heat various liquids, in particular water or aqueous solutions. The development goals for flow heaters for vehicles have always been: compact design, low manufacturing costs and high efficiency, so that a large amount of liquid can be heated in a short time.

[0003] It is an object of the invention to achieve these goals to a greater extent.

[0004] This object is achieved by a flow heater according to claim 1. Advantageous refinements of the invention are the subject of the dependent claims.

[0005] The water circuit of a motor vehicle can sometimes contain air bubbles or air bubbles can be generated over time. Air bubbles in a flow heater impair the heat transfer from the heating plate with the electric heating resistor to the liquid, in particular when air bubbles accumulate in the flow heater. In the flow heater according to the invention, the bypass channel counteracts the problem of air bubbles reaching the heating plate or even accumulating thereon.

[0006] In the flow heater according to the invention, the heating plate forms a wall of the heating section of the fluid channel. The heating section is connected in parallel to the bypass channel. Thus, air bubbles that can be present in the liquid can be guided from the inlet to the outlet without having to pass through the heating section of the fluid channel.

[0007] The parallel connection of the fluid channel is to be understood in the context of the fluid, so that the word "parallel" does not mean that the bypass channel is geometrically parallel to the heating section of the fluid channel. Rather, the "parallel connection" means that the bypass channel branches off from the fluid channel upstream of the heating section and merges into the fluid channel downstream of the heating section. Thus, a part of the liquid that enters the flow heater at the inlet flows through the heating section of the fluid channel to the outlet, while another part flows from the inlet through the bypass channel. The part that flows through the heating section of the fluid channel is greater than the part that flows through the bypass channel, preferably at least 10 times greater. For example, the flow resistance of the bypass channel can be at least 10 times greater than the flow resistance of the heating section of the flow channel.

[0008] When the liquid flows through the heating section of the fluid channel, friction causes a pressure loss. Therefore, the pressure at the beginning of the bypass channel is higher than the pressure at the end of the bypass channel. This pressure difference can be used to suck any air bubbles that can be present in the bypass channel.

[0009] In an advantageous refinement of the application, the pressure difference can be increased by widening the flow channel between the inlet and the heating section. In a corresponding embodiment of the application, the cross section of the inlet is smaller than the cross section of the heating section. Furthermore, the pressure difference increases if the flow channel between the heating section and the outlet narrows. In this way, a reduction in the flow rate after the inlet and a renewed increase in the flow rate before the outlet can be achieved. The higher speed before the outlet than after the inlet results in a pressure difference, so that any gas bubbles that can be present can be drawn more effectively through the bypass channel.

[0010] The flow heater is intended to be oriented in operation such that the starting point of the bypass channel is located on the upper wall of the flow channel. Then gravity causes any gas bubbles to rise, so that they can more easily enter the bypass channel.

[0011] In an embodiment of the application, the heating section can be in the shape of a U. The heating section then has two legs connected to one end. A flow channel of this form can be achieved, for example, by providing a partition wall between the two legs, which is connected to the heating plate. In such an embodiment, the liquid can flow down along one side of the partition wall and then up along the other side of the partition wall. In such an embodiment, the bypass channel can be provided as an opening in the partition wall at the upper end or as a conduit directly connected to the upper end of the two legs of the U-shaped flow channel.

[0012] In an embodiment of the application, the heating section of the flow channel can be a gap between the heating plate and a flow guide plate, which extends along the heating plate, for example, parallel to it. The flow guide plate can be made, for example, from a metal plate. The bypass channel can then be provided as a groove in the upper side of the flow guide plate and / or in the lower side of an intermediate wall connected to the lower side of the flow guide plate. Alternatively, the flow guide plate and the intermediate wall can be made as one piece. In both cases, the bypass channel can be provided as a hole through the intermediate wall.

[0013] In an embodiment of the application, the intermediate wall can have a very large wall thickness and can be designed, for example, as a bottom or lowered portion of a housing cover or as a raised portion of a housing bottom plate. The intermediate wall has a height measured at right angles to the upper surface of the flow guide plate immediately adjacent to the wall, a width or wall thickness measured in the direction of the line connecting the inlet and the outlet, and a length at right angles to its height and wall thickness. Here, the wall thickness can be several times the height of the wall and can also be greater than the length of the wall.

[0014] In a further advantageous refinement of the application, it is provided that the thickness of the intermediate wall increases with increasing distance from the inlet. In this way, the flow can be better directed and the formation of eddies and stagnation zones can be avoided.

[0015] Further details and advantages of the application are explained in the illustrative embodiments with reference to the drawings. Here:

[0016] Figure 1 A flow heater is shown in exploded view,

[0017] Figure 2 A housing of a flow heater is shown from below; and,

[0018] Figure 3 A simplified cross-sectional view of a flow heater is shown.

[0019] Figure 1 The flow heater shown has a housing 1 with an inlet 2 and an outlet 3. In the embodiment shown, the inlet 2 and the outlet 3 are arranged side by side on the same side of the housing 1; however, the inlet 2 and the outlet 3 can also be arranged on different sides of the housing.

[0020] The housing 1 is provided with a heating plate 4 which carries an electric heating resistor, for example in the form of a printed conductor track, and a flow guide plate 5. Furthermore, a circuit board 6 with control electronics is arranged in the housing 1, which can be connected to a supply voltage and a communication line via connector terminals 7, 8 provided by the housing 1. The upper and lower sides of the housing 1 are closed off with covers 9, 10.

[0021] In the housing 1, which can be made of metal, for example, a flow channel for the flow of the liquid to be heated extends from the inlet 2 to the outlet 3. The course of this flow channel can be assisted Figure 2 and Figure 3 for best understanding; Figure 2 The housing 1 of the flow heater is shown from below (with reference to the direction shown in Figure 1 , Figure 3 A simplified cross-sectional view of a flow heater is shown schematically.

[0022] The flow guide plate 5, which can be made of sheet metal, for example, adjoins an intermediate wall 11 which is arranged in the housing 1 between the inlet 2 and the outlet 3. The heating plate 4 is a wall of the heating section of the flow channel. In the embodiment shown, the heating section of the flow channel is arranged as a gap between the heating plate 4 and the flow guide plate 5, which heating plate 4 can have cooling fins 13.

[0023] In the direction of Figure 1 , the gap is bounded by the lower surface of the flow guide plate 5 and the upper surface of the heating plate 4. At the inlet 2 and the outlet 3, the flow channel can in each case have a section 14 which extends along the other face of the flow guide plate 5, i.e. along the upper surface of the flow guide plate 5.

[0024] To prevent bubbles from accumulating in the continuous flow heater, a bypass channel 16 branches off from the flow channel at a point between the inlet 2 and the heated section of the flow channel and re-joins the flow channel downstream of the heated section of the flow channel. The bypass channel is thus connected in parallel with the heated section of the flow channel. In the embodiment shown, the bypass channel is provided by a recess in the upper surface of the intermediate wall 11 against which the flow guide 5 rests.

[0025] The intermediate wall 11 delimits the beginning and end sections of the flow channel with its front surface 11a and back surface 11b. Here, the thickness of the intermediate wall 11 measured between the front surface 11a and the back surface 11b can increase with increasing distance from the inlet 2. In this way, the formation of vortices and stagnation zones is counteracted.

[0026] The flow channel widens in the housing 1 between the inlet 2 and the heated section of the flow channel. In other words, the flow channel between the inlet 2 and the gap has a larger cross-sectional area than the inlet 2. This means that the flow rate of the liquid decreases after entering the housing 1. In the region between the heated section and the outlet 3, the cross-sectional area of the flow channel decreases to the cross-sectional area of the outlet 3.

[0027] The flow resistance of the bypass channel 16 is significantly higher than the heated section of the flow channel 12, i.e. the gap between the heating plate 4 and the flow guide 5, for example ten times or more. In this way, it can be ensured that only a small fraction of the liquid flows through the bypass channel 16. To achieve a high flow resistance, it is advantageous to design the bypass channel 16 to be narrow. For example, the cross-sectional area of the bypass channel 16 at its narrowest point can be no more than one fifth of the cross-sectional area of the heated section of the flow channel 12 formed by the gap.

[0028] List of reference signs

[0029] 1 housing

[0030] 2 inlet

[0031] 3 outlet

[0032] 4 heating plate

[0033] 5 flow guide

[0034] 6 circuit carrier

[0035] 7 connector

[0036] 8 connector

[0037] 9 lid

[0038] 10 lid

[0039] 11 intermediate wall

[0040] 11a front surface of the intermediate wall

[0041] 11b rear surface of the intermediate wall

[0042] 12 flow channel

[0043] 13 fin

[0044] 14 segment of the flow channel

[0045] 16 bypass channel

Claims

1. A flow heater, comprising: The outer casing (1) has an inlet (2) and an outlet (3); A flow channel (12) for supplying the liquid to be heated extends from the inlet (2) to the outlet (3); The heating plate (4) is the wall of the heating section that is configured as a flow channel; Its features are, The bypass passage (16) is configured to be parallel to the heated section of the flow passage so as to guide any air bubbles contained in the liquid from the inlet (2) to the outlet (3) without passing through the heated section of the flow passage; The heating section of the flow channel (12) is set as the gap between the heating plate (4) and the guide plate (5); The bypass channel (16) extends along the upper surface of the guide plate (5), and the heating section of the flow channel (12) extends along the lower surface of the guide plate (5).

2. The flow heater according to claim 1, characterized in that, The guide plate (5) abuts against the intermediate wall (11), which is located between the inlet (2) and the outlet (3) in the housing (1).

3. The flow heater according to claim 2, characterized in that, The bypass channel (16) is formed by a groove on the lower surface of the intermediate wall (11), and the guide plate (5) abuts against the groove.

4. The flow heater according to claim 2, characterized in that, The thickness of the intermediate wall (11) increases with the distance from the entrance (2).

5. The flow heater according to claim 1, characterized in that, Between the inlet (2) and the heating section of the flow channel, a section of the flow channel (12) extends along the upper surface of the guide plate (5).

6. The flow heater according to claim 1, characterized in that, Between the heating section of the flow channel and the outlet (3), a section of the flow channel (12) extends along the upper surface of the guide plate (5).

7. The flow heater according to claim 1, characterized in that, The flow resistance of the bypass channel (16) is at least 10 times that of the flow resistance of the heating section of the flow channel.

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