SK9745Y1 - Modular PTC electric heater - Google Patents

Abstract

A modular PTC electric heater equipped with a heated liquid inlet (30) and a heated liquid outlet (40) is assembled from at least two structurally identical modules (10). The module (10) is designed as a cylindrical or cuboid container (1) with a cavity watertightly closed by two flanges or plugs (2), while the module (10) has a tubular inlet opening (3) and a tubular outlet opening (4), both openings are connected with the container cavity (1). The modules (10) are interconnected by a connecting part (7) provided with two sealings (71, 72) and each module (10) is equipped with at least one PTC cassette heating element (5) fixed on at least one flange or plug (2).

Description

The field of technology

The presented technical solution concerns an electric heater of a heat-carrying liquid, in particular water or a mixture of water with antifreeze liquid, which is conducted in a closed circuit of the heating system of buildings. The technical solution mainly concerns the auxiliary (backup) electric heater in heating systems with a heat pump.

Current state of the art

Current ecological building heating concepts use heat pump systems in which heat is taken from the outside environment. Heat pump systems are usually supplemented with another heating source, for example solar heating or an auxiliary (backup) electric heater, or a combination of several heating sources.

An auxiliary (backup) electric heater is used in heat pump systems especially when the heat taken from the outside environment is not sufficient for comfortable heating and/or heating of domestic hot water, especially in the winter months. At the same time, the electric heater also prevents freezing of the heat-carrying medium.

In known auxiliary electric heaters, the heating elements are designed as resistance heating elements (rods, spirals). The heating coil heats up to 850°C, which can cause overheating of adjacent parts if the temperature of the heating source is not properly controlled or monitored. In order to avoid thermal damage caused by the temperatures of these heating sources, which are significantly higher than the temperature of the liquid to be heated, an expensive safety concept is required.

Electric heaters with resistance coils are described for example in documents EP3910260 A1, EP3869118 A1 and EP3037741 A1.

An alternative to electric heaters with resistance coils are electric heaters with PTC (Positive Temperature Coefficient) heating elements known in the state of the art, the use of which is advantageous mainly due to the fact that the temperature of the heating element does not exceed 300 °C, or even less, depending on the specific design of the PTC heating element .

PTC elements are elements that are electrically conductive at low temperatures, but after reaching a certain temperature barrier, the electrical conductivity drops sharply. As the temperature of the PTC element increases, its resistance increases. Negative feedback is used, acting during the self-heating of the PTC element due to the passing current. When powered from a constant voltage source, this will cause a drop in power on the PTC element, which counteracts further temperature rise. The result is simple heating with stabilization of the temperature of the heated space.

Existing PTC liquid heating devices (mainly for use in automobiles) generally include a PTC heating element with a heat transfer structure that is typically very complex and therefore has disadvantages such as low heat transfer rate and uneven heat transfer. Even modular solutions allowing expansion of the heater's performance are complex and unusable for heating in heating systems. Such devices are for example described in document EP2792211 A1.

Document WO2021/014432 describes an electric cartridge heating element which is simpler in terms of design and function, the electric heating element comprises at least one tubular cartridge containing at least one PTC resistor therein, further comprising an aluminum or alloy block pressed by die casting around said at least one armored tubular cassettes, while a coating layer of plastic material is applied around said aluminum block.

Cassette heating elements of a similar design optimize heat transfer to ensure uniform heating and are also used for heating very small volumes with specific power and high temperatures. The stainless steel (aluminum, aluminum alloy or steel) shell construction with one end closed and power leads coming out of the other end simplifies installation and electrical connection.

The electric back-up heater for heat pump systems should generally provide outputs from 5 kW to 12 kW. A commercially produced cassette heating element usually provides a power of up to 450 W. It is obvious that in order to achieve the required total power, it will be necessary to use several cassette PTC heating elements suitably arranged so that the heating energy is transferred as efficiently as possible.

The resistance coils used in the previous generation of back-up electric heaters could be arranged in a simple way in a cylindrical exchanger and did not require a further increase in dimensions when increasing the power of the back-up heater, i.e. j. it was possible to use one exchanger dimension for all performance ranges.

The use of cassette PTC heating elements requires a different spatial arrangement of the heating elements in the exchanger.

The aim of the presented technical solution is to design a PTC electric heater with a high degree of performance and dimensional variability using a cassette heating PTC element. This goal is achieved by a modular assembly with the possibility of expansion. A lower power PTC electric heater will have smaller dimensions than a more powerful PTC electric heater. The modular assembly will be easily expandable, while the required waterproofing of the assembly will be ensured.

The essence of the technical solution

The expandable modular PTC electric heater is assembled from separate modules that are simply connected by a watertight joint using a joint equipped with a gasket. All modules have the same construction.

The module is designed as a cylindrical or cuboidal (flattened) container with a cavity sealed watertight by two flanges or plugs. The module has a tubular inlet and a tubular outlet, both openings are connected to the cavity.

On each module, at least one PTC cartridge heating element is mounted on at least one flange (or plug) and equipped with a jacket of stainless material (such as aluminum, aluminum alloy or steel) with one end closed and power leads coming out of the other end. The jacket of the heating element can advantageously be coated with an insulating plastic material.

The construction of the jacket does not require any additional insulation of the jacket when installed in the module cavity.

The cassette PTC heating element can be equipped with means for fixing in the flange (or in the plug), the fixing of the PTC heating element to the flange is not described in detail, as it is part of the state of the art (fixing nut, silicone gasket, etc. are used).

A PTC cassette heating element installed and connected to an electrical source transfers heat to the liquid flowing through the module cavity.

The module is equipped with fins arranged in the cavity to prevent swirling and to direct the flow of liquid from the inlet pipe opening to the outlet pipe opening. At the same time, the ribs serve to strengthen the entire module and increase the resistance against the pressure of the flowing liquid.

To connect two modules, the inlet pipe opening of the second module is connected to the outlet pipe opening of the first module, while the second module is rotated by 180°.

In this way, it is possible to expand the electric heater as needed.

The pipe openings have stops for the connecting piece. The connecting part made of metal or suitable plastic is equipped with two sealing rings, which is inserted into the pipe openings to create a watertight connection.

Furthermore, the module is equipped on the outer surface with a protruding wall with a cut-out for mutual connection and/or fixing the position of the modules.

Furthermore, the module is equipped on the outer surface with two clamps with holes for threading the connecting rods. The connecting rod is preferably metal and can have a thread with a nut on both ends to press the modules together and create a tight connection of all the modules.

The module can be made of a suitable metal or plastic material designed for hot heat transfer fluid, also the connecting rod can be made of any solid material.

In an advantageous embodiment, the module is made of plastic by injection into a mold.

Overview of images on drawings

The technical solution will be explained using, but not limited to, pictures. The pictures show:

Fig. 1 - view of the module with installed cassette PTC heating elements, fig. 2 - longitudinal section of the module from figure 1, fig. 3 - front view of the cavity of the module with ribs (without installed cassette PTC heating modules), fig. 4 - detail of the connecting part with two seals and the location of the connecting part in the tubular opening of the module, fig. 5 - indicated direction of liquid flow in a modular PTC electric heater and fig. 6 - modular electric PTC heater assembled from four modules.

Implementation examples

Example 1

In fig. 6, an expandable modular electric PTC heater 100 is depicted.

The expandable modular PTC electric heater 100 is equipped with a heated liquid inlet 30 and a heated liquid outlet 40 and is assembled from four separate modules 10, each module 10 being made as a cylindrical container 1 with a cavity watertightly closed by two flanges 2. The module 10 has a tubular inlet opening 3 and the tubular outlet opening 4, both openings 3, 4 are connected to the cavity of the container 1.

Each module 10 has mounted on each flange 2 four PTC cartridge heating elements 5 equipped with a jacket of stainless material with the liquid-immersed end closed and power leads coming from the other end. The jacket of the PTC heating element 5 can be advantageously coated with an insulating plastic material.

The module 10 shown in Figures 1, 2 and 3 is equipped with ribs 9 arranged in the cavity to prevent swirling and to direct the flow of liquid from the inlet pipe opening 3 to the outlet pipe opening 4. The ribs 9 simultaneously serve to strengthen the entire module 10 and increase the strength against pressure flowing liquid. The PTC cassette heating elements 5 are fitted in the flange 2 in such a way that they extend into the cavity of the module 10 between the ribs 9.

To connect two modules 10 in a row, the inlet pipe opening 3 of the second module 10 is connected to the outlet pipe opening 4 of the first module 10, while the second module 10 is rotated by 180°. The first module 10 means the preceding module and the second module 10 means the following module in the direction of liquid flow.

The pipe openings 3, 4 have stops 11 for the connecting part 7, which is inserted into the openings 3, 4 to create a watertight connection. The connecting part 7 is equipped with two sealing rings 71, 72 and is shown in figure 4.

After connecting the modules 10 using the connecting part 7, the liquid flows through the heated liquid inlet 30 in the direction of flow from the inlet opening 3 of each module 10 to its outlet opening 4, the flow is directed by the ribs 9 and this way of conducting the liquid through the modules 10 shows the smallest pressure losses. The direction of flow of the heated liquid through the connected modules 10 is shown by the arrows in Fig. 5.

In fig. 5 is the heated liquid inlet 30 at the lowest point of the modular electric PTC heater 100, such an arrangement is advantageous due to the removal of air bubbles directed upwards to the place where the vent valve is located in the system. Of course, in another embodiment, the heated liquid inlet 30 can be at the highest point of the modular electric PTC heater 100. The depicted direction of liquid flow shows that the liquid flows through the connected modules 10 always from the inlet circular opening 3 to the circular outlet opening 4.

The module 10 is equipped on the outer surface with a protruding wall 8 with a cut-out for connecting the modules to each other and/or fixing their position before connection using the connecting part 7.

Furthermore, the module 10 is equipped on the outer surface with two clips 6 with holes for passing through the connecting rods 50. The connecting rod 50 is preferably metal and can have a thread with a nut at both ends for additional pressing of the modules 10 together and creating a tight connection of all the modules 10 and the corresponding connecting parts 5.

The module 10 can be made of a suitable metal or plastic material designed for hot heat transfer fluid, also the connecting rod 50 can be made of any solid material.

In an advantageous embodiment, the module 10 is made of plastic by injection into a mold.

In the exemplary embodiment, the modular PTC electric heater 100 is assembled from four modules 10, each of which has eight cassette PTC heating elements 5 with a power of 400 W, and the total power of the modular PTC electric heater is therefore 12.8 kW. The modular electric PTC heater has an overall dimensions of 300mm x 110mm x 480mm (L x W x H), which is a suitable power and size for using the modular heater as a backup electric heater for heat pump systems.

Example 2 (not shown)

The modular PTC electric heater 100 is assembled from two modules 10, each of which has eight cassette PTC heating elements 5 with a power of 400 W, and the total power of the modular PTC electric heater is thus 6.4 kW. Already by connecting two modules 10 with sixteen cassette heating PTC elements, a smaller backup electric heater for systems with a heat pump is created.

In a separate claim, a heat pump system for heating buildings and/or preparing hot domestic water is protected, characterized in that the backup electric heater connected in a closed circuit of the heat-carrying medium is a modular PTC electric heater according to the presented technical solution.

Industrial applicability

The modular PTC electric heater according to the presented solution can replace the currently used electric heaters with resistance coils. The technical solution makes it possible to easily expand the 10 heater assembly according to the required power, while the power values are in the range from 400 W and practically unlimited from above.

Claims (9)

CLAIMS FOR PROTECTION 1. A modular PTC electric heater equipped with a heated liquid inlet (30) and a heated liquid outlet (40), assembled from at least two structurally identical modules (10), characterized in that the module (10) is designed as a cylindrical or cuboid container (1 ) with the cavity watertightly closed by two flanges or plugs (2), the module (10) has a tubular inlet opening (3) and a tubular outlet opening (4), both openings are connected to the container cavity (1), the modules (10) are interconnected connecting part (7) equipped with two seals (71, 72), each module (10) is equipped with at least one PTC cassette heating element (5) fixed on at least one flange or plug (2). 2. Modular PTC electric heater according to claim 1, characterized in that the module (10) is equipped in the cavity of the container (1) with ribs (9) arranged to prevent swirling, to direct the flow of the heated liquid and to increase the strength of the container (1) against pressure. 3. Modular PTC electric heater according to claim 2, characterized in that the inlet (30) of the heated liquid is connected to the pipe inlet opening (3) of the first module (10) and the outlet of the heated liquid (40) is connected to the pipe outlet opening (4) ) of the last connected module (10). 4. A modular PTC electric heater according to any preceding claim, characterized in that the module (10) is equipped on the outer surface with a projecting wall (8) with a cut-out for connecting the modules (10) to each other and/or fixing their position before connection by means of a connecting part (7). 5. A modular PTC electric heater according to any preceding claim, characterized in that to connect two modules (10) one after the other, the inlet pipe opening (3) of the second module (10) is connected to the outlet pipe opening (4) of the first module (10) ), while the second module (10) is turned 180° against the first module (10). 6. A modular PTC electric heater according to any preceding claim, characterized in that the module (10) is equipped on the outer surface with two clamps (6) with holes for passing connecting rods (50), while the connecting rod (50) has at its ends, a thread with a nut for additional pressing of the modules (10) and the corresponding connecting parts (7) together. 7. A modular PTC electric heater according to any of the preceding claims, characterized in that the module (10), the connecting part (5) and the connecting rod (50) are made of metal or plastic material intended for hot heat transfer fluid. 8. A modular PTC electric heater according to any one of claims 1 to 6, characterized in that the module (10) is preferably made of plastic by injection molding. 9. A heat pump system for heating buildings and/or preparing domestic hot water, characterized in that the backup electric heater connected in a closed circuit of the heat-carrying medium is a modular PTC electric heater according to any preceding claim.