Heat transfer fluid for the piping system of a heat transport device and heating circuit

Abstract

Heat transfer fluid (3) for the piping system (2) of a heat transport device (1), consisting of demineralized water (9) in which carbon nanoparticles (10) are dispersed, wherein the carbon nanoparticles (10) have a surface area ratio of 250 to 300 square meters per gram of weight.

Description

[0001] According to claim 1, the invention relates to a heat transfer fluid for the piping system of a heat transport device. The invention also relates, according to claim 6, to a heating circuit whose piping system carries a heat transfer fluid.

[0002] A heating system is a heat transport device in which water, traditionally used as a heat transfer fluid, is heated in a hot-water heating system, distributed via a piping system, and then transported to a heat dissipation device. In building heating systems, the warm heating water releases heat energy into the environment via heating surfaces, such as radiators or wall or floor heating. In heating technology, the heating circuit refers to the piping system for distributing the heat transfer fluid heated in a hot-water heating system to the heating surfaces. In a closed heating circuit, the heat transfer fluid is transported to the heating surfaces and then back to the hot-water heating system for further heat absorption.

[0003] Heating systems play a particularly important role in implementing statutory energy and climate targets. Buildings, not only in Germany, account for a large share of energy consumption, and the largest share of this is heating. Depending on the efficiency of the heating system's hot water preparation, these devices can cause particularly high energy consumption, for example, an inefficient boiler. Against this backdrop, the highest possible efficiency of a heating system is desirable.

[0004] It is well known that, in addition to the hot water heating equipment, the quality of the water used as a heat transfer fluid also has a long-term impact on the efficient and trouble-free operation of the heating system. Especially in a closed heating circuit, little water is lost, and the heating water is therefore treated to ensure it remains functional over time. To this end, substances are added to the heating water to counteract corrosion of the heating system or calcification. However, such additives cannot improve heat transfer through the heat transfer fluid.

[0005] The present invention is based on the object of improving the efficiency of heat transport.

[0006] This object is achieved according to the invention by a heat transfer fluid having the features of claim 1. The object is also achieved according to claim 6 by a heating circuit with such a heat transfer fluid.

[0007] With the aim of improving the effectiveness of heat transfer, the invention does not follow previous proposals for improving the longevity of a system, but rather improves the heat transfer capacity of the heat transfer fluid. It is based on the finding that carbon nanoparticles have certain properties which, when dispersed in a heat transfer fluid, significantly improve the effectiveness of heat transfer. The invention has recognized that a permanently stable dispersion can be provided and the heat capacity of the heat transfer fluid can be increased if carbon nanoparticles with a surface area ratio of 250 to 300 square meters per gram of weight are dispersed in demineralized water. A dispersion of water and carbon nanoparticles is understood to be a homogeneous mixture in which the carbon nanoparticles are finely distributed in the water.The heat transfer fluid with the inventive dispersion of water and carbon nanoparticles does not sediment even after extended periods. The carbon nanoparticles are stably supported by the water in the inventive configuration of the heat transfer fluid.

[0008] The heat transfer fluid according to the invention can transport heat quantities faster and more effectively than conventional heating water or other aqueous heat transfer fluids, without the need for chemicals. Carbon nanoparticles exhibit good thermal conductivity, which is even higher than that of natural diamond. Both components of the heat transfer fluid according to the invention complement each other in their respective advantageous properties, with the specific heat capacity of the heat transfer fluid being significantly higher than that of conventional heating water in the configuration according to the invention.

[0009] A particularly stable dispersion for a high-performance heat transfer fluid is formed when the carbon nanoparticles are dispersed in a ratio of 10 to 80 grams per 1000 kilograms of water. A ratio of 60 grams of carbon nanoparticles per 1000 kilograms of water has proven particularly advantageous.

[0010] In an advantageous embodiment of the invention, the carbon nanoparticles are dispersed in demineralized water with an oxygen content of less than 0.1 milligrams per liter. The demineralized water stably supports the dispersed carbon nanoparticles if the feed water is distilled or demineralized, depending on its quality, and the oxygen content is subsequently reduced to below 0.1 milligrams per liter by degassing. Before degassing, the water is advantageously treated and desalinated in one or two osmosis stages.

[0011] An effective heat transfer fluid composed of demineralized water and dispersed carbon nanoparticles is characterized by a dispersion configuration such that the heat transfer fluid has an electrical conductivity between 30 and 40 microsiemens per centimeter.

[0012] In the preferred embodiment of the invention, the carbon nanoparticles are formed as carbon nanotubes, whose properties, particularly the high surface area-to-mass ratio, are highly advantageous for the formation of the heat transfer fluid according to the invention. By dispersing carbon nanotubes with the inventive configuration, the specific heat capacity of conventional heating water can be regularly increased by 25 percent, thus increasing the effectiveness of heat transfer.

[0013] The heat transfer fluid according to the invention is stable and increases the effectiveness of heat transport from the heat source to the heating surfaces in a closed heating circuit over a long period of time.

[0014] An embodiment of the invention is explained in more detail below with reference to the drawings. They show: Fig. 1 a schematic view of an embodiment of a heat transport device with a heat transfer fluid according to the invention, Fig. 2 an embodiment of a dispersion of water and carbon nanoparticles, Fig. 3 a perspective view of an embodiment of a carbon nanoparticle.

[0015] Fig.1 shows a schematic view of a heat transport device 1 for transporting heat via a heat transfer fluid 3, which in the illustrated embodiment is the closed heating circuit 13 of a heating system. A piping system 2 of the heating circuit 13 carries the heat transfer fluid 3. The heat transfer fluid 3 is heated in a hot water heating system 4, for example a boiler or a heat exchanger, and fed to a heating surface 6 in a flow line 5. The heating surface 6 is a device that releases supplied heat to the environment and comprises radiators or elements of a wall or underfloor heating system. After the heat has been released from the heating surface 6, the heat transfer fluid 3 is returned to the hot water heating system 4 via the return line 7 of the piping system 2, where it can absorb heat again in the closed heating circuit 13.In the embodiment shown, a circulation pump 8 is arranged in the heating circuit 13 to move the heat transfer fluid 3.

[0016] The heat transfer fluid 3 is a dispersion of demineralized water 9 and carbon nanoparticles 10, which are Fig.2. The presence of carbon nanoparticles 10 significantly increases the specific heat capacity of the heat transfer fluid, so that the circulating heat transfer fluid 3 can supply larger amounts of heat to the heating surface 6 more quickly. To prepare the dispersion, feed water is demineralized or distilled and then brought to an oxygen content of less than 0.1 milligrams per liter in a degassing stage. Carbon nanoparticles 10 are added to the demineralized water 9 with a surface area ratio of 250 to 300 square meters per gram of weight, as indicated by arrow 14, and dispersed, i.e., a homogeneous mixture is formed. A stable dispersion, which does not tend towards sedimentation of the carbon nanoparticles 10 even after a prolonged period of time, results with a ratio of 10 to 80 grams of carbon nanoparticles per 1000 kilograms of water.

[0017] In the embodiment shown, the carbon nanoparticles 10 are designed as carbon nanotubes (cnt), which are Fig. 3 are shown schematically. Carbon nanotubes (CNT) are carbon tubes (carbon nanotubes=CNT) with diameters in the nanometer range. They are constructed from honeycomb lattices of carbon atoms. With their outer surface 11 and their inner surface 12, carbon nanotubes (CNT) have a comparatively very large surface area, making them particularly well suited to the function of the heat transfer fluid, namely heat absorption and dissipation. Another advantageous property of the carbon nanotubes (CNT), which improves the effectiveness of the heat transfer fluid 3 when dispersed with demineralized water 9, is their particularly good thermal conductivity, which at room temperature, at 6000 W / (m·K), is more than 2.5 times higher than that of natural diamond at 2190 W / (m·K).

[0018] For a stable dispersion of demineralized water 8 and carbon nanoparticles 10, in the illustrated embodiment of a heat transfer fluid 3 for heating circuits 1, carbon nanotubes (cnt) are dispersed in a preferred ratio of 60 grams per 1000 kilograms of water.

[0019] An effective heat transfer fluid composed of demineralized water and dispersed carbon nanoparticles exhibits an electrical conductivity of between 30 and 40 microsiemens per centimeter. In the illustrated embodiment, with carbon nanotubes (CNT) in a ratio of 60 grams per 1000 kilograms of water 9, the heat transfer fluid 3 exhibits an electrical conductivity of approximately 36 microsiemens per centimeter.

[0020] In an advantageous embodiment, the heat transfer fluid 3 with a dispersion of demineralized water 9 and carbon nanotubes (cnt) has the following additional properties: -pH value at 20ºC: 8,2 -Total hardness: 0.29 ºdH -Magnesium content: 0,004 mol / m 3 - Sodium content: 0,41 mol / m 3 - Nitrite content: 0,001 mol / m 3 - Chloride content: 0,027 mol / m 3 - Sulfate content: 0,004 mol / m 3 - Nitrate content: 0,014 mol / m 3 List of reference symbols (part of the description) 1 heat transport device 2 Piping system 3 Heat transfer fluid 4 Hot water heating 5 Lead-up 6 heating surface 7 Return 8 Circulation pump 9 Demineralized water 10 carbon nanoparticles 11 Outer surface 12 Inner surface 13 Heating circuit 14 Arrow CNT carbon nanotubes

Claims

[1] Heat transfer fluid (3) for the piping system (2) of a heat transport device (1), consisting of demineralized water (9) in which carbon nanoparticles (10) are dispersed, wherein the carbon nanoparticles (10) have a ratio of their surfaces of 250 to 300 square meters per gram of weight. [2] Heat transfer fluid (3) according to claim 1, characterized by that the carbon nanoparticles (10) are dispersed in a ratio of 10 to 80 grams per 1000 kilograms of water. [3] Heat transfer fluid (3) according to claim 1 or 2, characterized by that the demineralized water (9) has an oxygen content of less than 0.1 milligrams per liter. [4] Heat transfer fluid (3) according to one of the preceding claims, characterized bya configuration of the dispersion of water (9) and carbon nanoparticles (10) such that the heat transfer fluid (3) has an electrical conductivity between 30 and 40 microsiemens per centimeter. [5] Heat transfer fluid (3) according to one of the preceding claims, characterized by that the carbon nanoparticles (10) are formed as carbon nanotubes (cnt). [6] Heating circuit (13) with a piping system (2) which carries a heat transfer fluid (3) according to one of claims 1 to 5.

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