Method and apparatus for preventing ice formation in a tub for collecting condensate of an evaporator of a heat pump

Abstract

The invention relates to a method and a device for preventing icing in a collection tray (1) for water (2) which drips from a heat exchanger (3) of a heat pump system (4) through which ambient air (9) flows, wherein water (2) is accumulated in the collection tray (1) up to a predetermined height (H) and then discharged through an overflow (5) and / or drain (6), and wherein, in the event of a risk of freezing, sufficient heat is supplied to the collection tray (1) and / or the accumulated water (2) so that the accumulated water (2) does not fall below a predetermined minimum temperature.The collection tray (1) has, in particular, a drain (6) connected to an overflow (5), and the overflow (5) is positioned and raised such that water (2) accumulates in the collection tray (1) with a continuous surface area (7) before the water (2) flows out through the overflow (5), and at least one heating device (11; 12) is arranged in or on the collection tray (1) by which heat can be supplied in case of risk of freezing. The present invention makes it possible to prevent icing with low energy consumption and even with large tolerances in the shape and positioning of a collection tray (1).

Description

[0001] The invention relates to a method and a device for preventing ice formation and / or for defrosting existing ice in a tub for collecting condensate from an evaporator of a heat pump, in particular an evaporator through which ambient air flows.

[0002] Heat pumps, which extract heat from the ambient air to heat a building and / or domestic hot water, are available in many designs. A common feature of these heat pump systems is a heat exchanger (usually an evaporator in a heat pump circuit or a condenser in a refrigeration circuit) through which ambient air flows. This heat exchanger can ice up at low air temperatures. Ice then accumulates on the heat exchanger surfaces and must be defrosted before the heat transfer becomes insufficient or the heat exchanger is damaged. During this defrosting process, and under certain other operating conditions, water (melted ice or condensation) drips from the heat exchanger into a collection tray, which collects the water and drains it away. Under unfavorable temperature and / or humidity conditions, this collection tray can also freeze over and / or its drain can become clogged with ice, which should be prevented.

[0003] For this purpose, it is known to heat a collection tray, for which various systems have been proposed. Electric heaters are known, as are methods in which heat is diverted from other parts of a heat pump system to heat the collection tray and transported there, for example, via a heat transfer fluid.

[0004] One problem is the size of a typical drip tray, which makes it difficult to distribute heat to all areas where water can drip into the tray (and potentially freeze). Furthermore, since the bottom and walls of the drip tray cannot be arbitrarily thick for cost reasons (and are not necessarily made of highly thermally conductive material), they only transfer heat from a heated area to other areas to a limited extent. Therefore, heating systems for drip trays are often quite complex or inefficient. In particular, heating mats placed in a drip tray often do not have good thermal contact with the tray bottom, so heat can be lost unused. To prevent water from accumulating in certain areas of a drip tray and freezing there, potentially causing damage, a heating system is often used.To prevent damage, collection trays are usually designed so that their bottom has a minimum slope towards a drain everywhere, which means a certain construction height and also requires that collection trays be set up quite precisely horizontally aligned.

[0005] DE 20 2016 105 283 U1 describes a drip tray with underfloor heating and a drain. Dripping water and its temperature can be detected in the drip tray. If the water temperature falls too far below a pre-selected target temperature, underfloor heating can be activated via a heating control system until the target temperature is reached. The fill level in the drip tray can also be detected. An alarm can be triggered if a critical fill level is exceeded.

[0006] The object of the present invention is to at least alleviate the problems described in connection with the prior art and in particular to provide a method and a device that prevents the icing up of a tub for collecting condensate of a heat exchanger of a heat pump system.

[0007] To solve this problem, a method and a device according to the independent claims are provided. Advantageous further developments and embodiments are specified in the respective dependent claims, to which, however, the present invention is not limited.

[0008] A method contributes to the solution for preventing icing in a collection tray for water that drips from a heat exchanger of a heat pump system through which ambient air flows, wherein water is accumulated in the collection tray up to a predetermined height and then discharged through an overflow, and wherein, in the event of a risk of freezing, enough heat is supplied to the collection tray and / or the accumulated water so that the accumulated water does not fall below a predetermined minimum temperature.

[0009] Insofar as a heat exchanger is mentioned here, this refers to the air-to-air heat exchanger, which functions either as an evaporator in heating mode or as a condenser in cooling mode. The heat pump can be located outdoors and thus be at least partially exposed to the surrounding weather conditions. The collection tray is positioned relative to the heat exchanger so that water forming at the heat exchanger (e.g., condensate) and / or water flowing towards it (rain, dew, ice, snow) can be collected and stored to a predetermined extent, preferably below the heat exchanger. The collection tray is designed to hold a predetermined volume (of water, snow, etc.) and, should more water / snow, etc., accumulate, this excess is removed, for example, via an overflow, drain, etc. For this purpose, the collection tray has a height that defines a predetermined collection volume for water.Furthermore, it is now planned that heat will be supplied to the collection tray and / or the water / snow, etc., contained within it at a predetermined time to ensure that a minimum water temperature is maintained. This minimum temperature is one at which ice formation is impossible. The timing can be determined based on the risk of freezing. The point at which a "risk of freezing" exists can be (automatically) defined using various parameters and / or measurements. The "risk" can include current or future environmental conditions conducive to water freezing. "Freezing" can specifically mean that the accumulated water freezes predominantly or even completely. This is distinct from the thawing of water that is already (completely) frozen in the collection tray.

[0010] This approach offers several significant advantages:

[0011] The accumulated (warm or heated) water itself supports the distribution of heat from a heating system through conduction and convection, regardless of where and how the heat is supplied to the collection tray and / or the water. It is no longer necessary to heat the bottom of the collection tray as evenly as possible, and heat from, for example, heating mats placed in the tray is no longer lost directly to the surroundings, instead of first heating the water. At the same time, the water also acts as a heat storage medium, so that freezing is not a concern in the event of brief periods of low outside temperatures.

[0012] Furthermore, the shape and precise horizontal alignment of the base of the collection tray are no longer critical, as long as its unevenness and elevations are essentially covered by water. Heating mats or coiled pipes can therefore be installed inside the collection tray without obstructing the drainage of the (accumulated) water.

[0013] Finally, it is also no longer possible for water to freeze anywhere in the collection tray, the thawing of which would require much more heat energy in the short term than maintaining a temperature above freezing at ambient temperatures below freezing.

[0014] The simplest way to achieve this is with an overflow located at the specified height, designed to hold water up to a height of 1 to 10 cm, particularly 2 to 5 cm. However, it is also possible to close a low-lying drain using a valve, such as a float valve, which only opens when and as long as the water level exceeds the specified height.

[0015] The water temperature can also be regulated in various ways (using standard control technology). Firstly, heating can generally be omitted when outside temperatures are above freezing. At ambient temperatures below or near freezing, temperature control can be implemented to maintain the stored water within a desired temperature range slightly above freezing, e.g., between 2 and 5 °C [degrees Celsius]. This eliminates the risk of freezing, even in the outer areas of the collection tray or at the overflow and / or drain.

[0016] Preferably, the collection tray and / or the collected water are electrically heated. This allows for easy installation and control of heating devices. In particular, heating mats, heating rods, heating coils, and the like can now be easily placed in the collection tray, where, submerged in water, they distribute their heat evenly to both the water and the tray. Alternatively, heating devices can also be installed on the outside of the collection tray, as the collected water helps to distribute the heat.

[0017] Additionally or alternatively, the collection tray and / or the accumulated water are heated with heat from other parts of the heat pump system. This also results in the aforementioned advantages of a more even heat distribution. In particular, heating pipes installed inside the collection tray no longer impede the water drainage.

[0018] The water is preferably dammed up to such a high level that a continuous water surface (comprising all possible water surfaces) forms in the collection basin, regardless of the exact shape of the basin's base and its orientation relative to a horizontal surface. This results in a particularly low risk of icing occurring anywhere, because the water carries heat supplied from anywhere to all areas.

[0019] A device for preventing icing in a collection tray for water dripping from a heat exchanger of a heat pump system through which ambient air flows also contributes to solving the problem, wherein the collection tray has an overflow and the overflow is arranged and positioned so that water accumulates in the collection tray with a continuous water surface before water flows out through the overflow, and wherein at least one heating device is arranged in or on the collection tray, through which, in case of danger of freezing, enough heat can be supplied so that the accumulated water does not fall below a predefinable minimum temperature.

[0020] The overflow is designed to hold water up to a height of 1 to 10 cm [centimeters], particularly 2 to 5 cm. The drip tray only needs to be 0.5 to 2 cm higher than this height, as it only needs to prevent overflow at a point other than the overflow itself.

[0021] The at least one heating device is designed in such a way that, if a risk of freezing of the accumulated water is detected and / or exists, it can (always) supply sufficient heat to ensure that the accumulated water does not fall below a predefinable minimum temperature (to maintain a liquid state). The at least one heating device is in direct contact with the accumulated water; preferably, heat is conducted from (a component of the) heating device to the accumulated water. The heat can be conducted or transferred from the (local) heating device via the water to other areas of the water or the collection tray located away from the heating device, thus preventing freezing with minimal energy expenditure. The water itself can therefore be used for heat transfer, particularly if it is intentionally accumulated in the collection tray.can flow.

[0022] The heating system may be equipped with a control unit that can initiate and / or terminate a heating process as needed and / or according to the situation. This control unit may interact with sensors that provide data or information to determine or predict the risk of freezing. These sensors may, for example, be configured to provide signals for determining the (current and / or future) temperature (of a component, the environment, etc.), the (current and / or future) humidity, the (current and / or future) amount of water in the drip tray, etc. The control unit can interpret and evaluate these signals and regulate the operation of the heating system accordingly, particularly with a focus on maintaining a calculated and / or variably adjusted minimum temperature of the stored water.

[0023] Preferably, the overflow consists of a substantially vertical pipe section placed on top of the drain, which has at least one opening at a predetermined height. Water flows through the (open at the top) pipe section only when the water level exceeds this height, without requiring any regulation. Therefore, during operation, water will always be present in the collection tray up to this height. It is preferred that the at least one heating element is located in the area near or around the drain where the water initially accumulates (or up to the overflow).

[0024] The base of the collection tray may have irregularities and / or not be horizontal and / or not sloped towards the drain. Unlike previous designs, such details are no longer critical because it is no longer necessary to try to empty the collection tray completely. Similarly, it is not essential for the heating elements inside the collection tray to have the largest possible contact area with the base, as the accumulated water absorbs and distributes heat even without such contact. It is preferred that the at least one heating element is located in / on the at least one irregularity where the water collects. These irregularities can be designed as grooves, ridges, etc., providing sufficient volume for the heating element and the accumulated water.

[0025] Preferably (and most easily controlled), the heating device is an electric heater, in particular in the form of at least one heating mat, heating coil, or heating rod. As long as these are covered by water, good heat distribution is ensured. An electric heater typically works on the principle of ohmic resistance heating, so that it generates heat when an electric current flows through it.

[0026] Alternatively, or additionally, the heating system can be heated using a heat transfer fluid from the heat pump system. This saves electrical energy and, depending on the spatial arrangement of the heat pump system components, can be achieved with short circuits. Heating pipes can be laid in the drip tray without obstructing the water drainage.

[0027] The explanations of the procedure can also be used to characterize the device, and vice versa. The device is configured to carry out the proposed procedure (automatically).

[0028] Schematic embodiments of the invention, to which it is not limited, and the functioning of the method will now be explained in more detail with reference to the drawing. It illustrates: Fig. 1: a heat exchanger with a drip tray and Fig. 2: a schematic longitudinal section through a drip tray with heating devices and accumulated water.

[0029] Figure 1Figure 1 schematically shows a drip tray 1 located beneath a heat exchanger 3, for example, an evaporator of a heat pump system 4, through which ambient air 9 can flow. Under certain operating conditions, water 2 (usually condensate) drips from this heat exchanger 3, which is collected in the drip tray 1 and accumulated up to a height H. This height H is 1 to 10 cm, preferably 2 to 5 cm. In the simplest case, this is achieved using a pipe section 10, which is placed on a drain 6 and forms an overflow 5 at its upper end. The pipe section 10 can simply be open at the top or have at least one opening at height H. The height H, i.e., the water level in the drip tray, is determined by the length of the pipe section 10 (which can also be variable) or the position of the openings. Alternatively (albeit with somewhat more effort), this can also be achieved without a pipe section 10 by closing the drain 6 (e.g., by...).This can be achieved (by means of a valve, in particular with the aid of a float) and opening only when the water level exceeds height H. The water 2 constantly present in the collection tray 1 up to height H offers several advantages, especially with regard to preventing icing throughout the entire area of ​​the collection tray 1. Firstly, this water 2 has a certain heat capacity that prevents rapid freezing, which can occur with small amounts of water in the collection tray 1 if the outside temperature drops quickly and / or significantly below freezing. Furthermore, heating devices 11, 12 can now be arranged more easily, since it is no longer necessary to heat the entire collection tray 1 as evenly as possible.In particular, heating devices 11, 12 can be placed in the collection tray 1, especially on a base 8 of the collection tray 1, without obstructing the drainage of the water 2 or having poor thermal contact with the collection tray 1 due to unevenness 15. It should only be ensured that the water 2 covers the heating devices 11, 12, in particular forming a continuous water surface 7. Then the water 2 helps to distribute the introduced heat by conduction and convection, almost regardless of where the heat is introduced. Electric heating devices 11, e.g., heating mats 13, are suitable for heating. However, a fluidic heating device 12 can also be provided, which supplies heat to the water 2 by means of a heat transfer medium from components of the heat pump system 4.

[0030] Fig. 2Figure 1 shows a schematic longitudinal section through the collection tray 1 described above, containing accumulated water 2. The section passes through the overflow 5 and the drain 6. To illustrate the advantages of the invention, the base 8 is provided with (exaggerated) irregularities 15 and is mounted at an angle to a horizontal surface 16. Furthermore, as an example of an (electric) heating device 11, a heating mat 13 is placed on the base 8 of the collection tray 1. It can be seen that, due to the irregularities 15, gaps 14 form between the base 8 and the heating mat 13, which would reduce heat transfer to the collection tray 1 if no water 2 were present. However, by accumulating water 2 up to a height H, all previously disadvantageous effects of the irregularities 15 and the inclined mounting are eliminated. The water 2 covers the heating mat 13 (usually also filling the gap 14) and thus absorbs heat that would otherwise have flowed uselessly into the surroundings, and distributes it.As a result, less energy is required to prevent freezing, and the drip tray 1 can nevertheless be manufactured with larger tolerances and positioned less precisely. Due to the unevenness 15 and a potentially sloping installation position of the drip tray 1, the height H is not necessarily uniform, so an average height H above the floor 8 can be assumed.

[0031] It should be noted that heating the stored water 2, e.g., by switching on the electric heating device 11 via a switch 18 connected to a power source 17, is only necessary if the ambient temperature could otherwise cause freezing. In such a case, enough heat should be supplied to maintain a temperature with a certain safety margin above the freezing point. The heat losses are no greater than when heating an empty collection tray 1, and are even lower, because the water distributes the heat evenly and no individual areas are warmer than others. The surface area also changes only slightly. It is desirable that the water 2 not only forms a continuous water surface 7 (which would still allow for "islands" or irregular edges), but a water surface 7 that completely fills the collection tray 1. The invention is most effective when this is the case.

[0032] The present invention makes it possible to prevent icing with low energy input and even with large tolerances in the shape and setup of a collection tray 1. Reference symbol list

[0033] 1 Drip tray 2 Water 3 Heat exchanger / evaporator 4 Heat pump system 5 Overflow 6 Drain 7 Water surface 8 Floor 9 Ambient air 10 Pipe section 11 Electric heating device 12 Fluid heating device 13 Heating mat 14 Gaps 15 Unevenness 16 Horizontal 17 Power source 18 Switch HHöhe (water level)

Claims

1. Method for preventing icing in a collection tray (1) for water (2) which drips from a heat exchanger (3) of a heat pump system (4) through which ambient air (9) can flow, and wherein, in the event of a risk of freezing, sufficient heat is supplied to the collection tray (1) and / or the accumulated water (2) such that the accumulated water (2) does not fall below a predetermined minimum temperature, characterised in that the water is accumulated in the collection tray (1) up to a preset height (H) of 1 cm to 10 cm and then drained off through an overflow (5).

2. Method according to claim 1, wherein the collection tray (1) and / or the accumulated water (2) are electrically heated.

3. Method according to claim 1 or 2, wherein the collection tray (1) and / or the accumulated water (2) are heated with heat from the heat pump system (4).

4. Method according to one of the preceding claims, wherein the water (2) is accumulated to such a height that a continuous water surface (7) is formed in the collection tray (1), regardless of the exact shape of a base (8) of the collection tray (1) and its position relative to a horizontal (16).

5. Device for preventing icing in a collection tray (1) for water (2) which drips from a heat exchanger (3) of a heat pump system (4) through which ambient air (9) can flow, wherein the collection tray (1) has a drain (6) connected to an overflow (5) and the overflow is so high and so arranged that water (2) with a continuous water surface (7) accumulates in the collection tray (1) accumulates water (2) with a continuous water surface (7) up to a predetermined height (H) of 1 to 10 cm, before water (2) flows off through the overflow (5), and wherein at least one heating device (11; 12) is arranged in or on the collection tray (1), through which, in the event of a risk of freezing, sufficient heat can be supplied to ensure that the accumulated water (2) does not fall below a predetermined minimum temperature.

6. Device according to claim 5, wherein the overflow (5) is formed by a vertically extending pipe section (10) placed on the drain (6).

7. Device according to claim 5 or 6, wherein a base (8) of the collection tray (1) has unevenness (15) and / or is not aligned horizontally (16) and / or is not provided with a slope towards the drain (6).

8. Device according to one of claims 5 to 7, wherein the at least one heating device is an electric heater (11).

9. Device according to one of claims 5 to 7, wherein the heating device (12) can be heated by a heat transfer fluid with heat from other parts of the heat pump system.

10. Device according to one of claims 5 to 9, wherein the collection tray (1) is 0.5 to 2 cm higher than the height (H).

Images