Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B3/00—Ohmic-resistance heating
  • H05B3/20—Heating elements having extended surface area substantially in a two-dimensional [2D] plane, e.g. plate-heater
  • H05B3/34—Heating elements having extended surface area substantially in a two-dimensional [2D] plane, e.g. plate-heater flexible, e.g. heating nets or webs
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
  • F24D13/00—Electric heating systems
  • F24D13/02—Electric heating systems solely using resistance heating, e.g. underfloor heating
  • F24D13/022—Electric heating systems solely using resistance heating, e.g. underfloor heating resistances incorporated in construction elements
  • F24D13/024—Electric heating systems solely using resistance heating, e.g. underfloor heating resistances incorporated in construction elements in walls, floors, ceilings
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
  • H05B2203/026—Heaters specially adapted for floor heating

Definitions

• the present invention relates to a system comprising an electric heating lattice, and to the use of such a system having an electric heating lattice buried underground.
• a spreading of heat along the transverse web plane promotes a uniform distribution of heat from the directly electrically heated first bare wires and from the indirectly, through thermal conduction, heated second bare wires to the surrounding of the web.
• this surrounding may be air or water to be heated which is flowing through the openings of some air or water treatment system. If the lattice is buried in an underground it will be the underground which is uniformly and homogenously heated. In general the occurrence of significant temperature gradients in the lattice is prevented in an easy and cost effective way, also because bare wires are applied.
• At least said first bare wires which are composed of an electric resistance steel alloy are arranged side by side in an average wire density between 2-4 wires per centimetre.
• An average wire density which is less than 2 wires/cm on average results in currents through the first wires which are generally too high and consequently the temperature gradients are too high, thus negatively influencing the application area of the system because the growth of roots and/or plants and/or grasses in and on the surface as well as bottom life in the underground will be influenced negatively.
• More than an average of 4 wires per centimetre makes the lattice expensive, heavy to transport and not easy to position and handle in the field.
• An average first wire density of 3 wires/cm is often preferred in practise.
• the choice of the average first wire density is also important in relation to the particular boundaries of officially prescribed maximum allowable power, voltages as well as currents and the way wherein these requirements can be met in optimum embodiments of the system concerned. Keeping these power parameters in the lattice within prescribed boundary conditions and nevertheless generating enough but not too much uniform heat in said plane is proven a real challenge solved by the system according to the present invention.
• Fig. 1 shows an electric heating lattice 1 which is embodied here as a web or weave comprising a first type of mutually spaced longitudinal wires 2 and a second type of transverse/cross wires 3, being arranged transverse to the first type of wires 2.
• Both types of wires 2, 3 are made of a generally metallic alloy, possibly the same alloy for reasons of cost-price or for easy of production.
• the first type of wires 2 are made of an electric resistance alloy chosen to have a certain specific resistance, and the second type of wires 3 at least thermally conductive.
• the first type of resistance alloy wires 2 comprises at least one and generally a composition out of the mainly metallic group containing: iron, steel, chrome, nickel, copper and carbon.
• the group constituents may be chosen to result for example in constantan or stainless steel which are among the many other alloys easy to manufacture and readily available. Stainless steel is preferred due to its durability and rust resistance. Stainless steel 316 has the appropriate specific resistance. It is preferred that the wires 2, 3 are made of an alloy which is easy to weave to form a lattice or web. And at least the first to be electrically powered wires 2 should have the specific resistance and diameter that a wanted sufficient amount of heat per unit area can be developed. In general the amount of heat generated in said first wires meant for heating 1 m 2 ground area is between 50 and 150 Watt on average.
• 100 Watt/m 2 on average is a maximum for application of lattices in agricultural or sports grounds, which is due to the fact that more heat would be detrimental to underground microbiological life and insect life in the underground and the growth of plants, crops, grasses and the like on the surface of the underground.
• the lattice 1 can be buried in an underground 7 of for example a playing ground, an agricultural ground or a sporting ground such as a football field, or the lattice is provided in or under a road, pavement, floor, wall, ceiling, runway, airfield, approach, drive or ramp or the like.
• the electric resistance alloy of at least the first type of wires 2 is a raw, that is not isolated alloy.
• the outer surface of the raw alloy is bare or untreated that is unprocessed or uncoated which promotes heat delivery by the wires 2 to a surrounding with a high efficiency.
• openings 6 therein -to be elucidated hereinafter- serve to allow water and/or air to pass.
• it is preferred to use stainless steel 316L as alloy for the first and second wires 2, 3 as this alloy given its lower amount of carbon provides an even better resistance against rust and other mostly chemical substances present in soil.
• the lattice 1 can be used to heat water or air passing through the openings 6 in the lattice such as in water and/or air systems for heating or treatment.
• the diameter and total weight of the lattice 1 has to lie within manageable boundaries in order to position the strips easily and to develop a sufficient amount of heat in the electrically powered wires 2.
• several consecutive individual lattice strip configurations are necessary to cover a whole field or underground. For example for a European football field the use of some 55-65 lattice systems as shown in fig. 1 are required.
• the wires 2, 3 elucidated in the lattice mesh detail of fig. 1 make at least thermal contact at nodes 5 which are made by generally welding the metallic alloys for example in a continuous electric welding process. Also spot welding is an alternative.
• the process allows the manufacturing of a normally regular web of longitudinal wires 2 and transverse wires 3 which are welded at the nodes 5. If the lattice web is regular four neighbouring spots on 2x2 neighbouring wires 2, 3 surround an opening 6 which is rectangular or preferably square in shape. If squared as shown in the detail of fig. 1 the lattice 1 has a fully regular pattern resulting in a very uniform heat distribution in both the lattice web plane and in height and thus also in ground, soil and underground material.
• the first type of mutually spaced wires 2 and/or the second type of transverse wires 3 may simply cross each other at nodes 5 or they may alternatively cross over and under each other at consecutive and neighbouring nodes 5 as shown in the detail of fig. 1 . In the latter case the mechanical stability of the woven lattice 1 improves at the cost of a slightly more complex manufacturing and handling thereof.
• Both types of wires 2, 3 may have equal cross sections, which in practice will be sufficient to allow heat to be spread out more evenly and homogeneously via the nodes 5 along the at least thermally conductive cross wires 3 too. E.g. such equal wire type cross sections doubles the total heat radiating outer surfaces of the wires 2, 3 while only the wires 2 have to be electrically powered.
• the amount of heat developed in the first wires 2 i.e. also depends on the diameter of the first wires 2 which is chosen between 0.5 mm and 1 mm, in particular 0.6 mm and 0.8 mm. In a layout of a 3 wire/cm density the preferred diameter of at least the first wires 2 is 0.7 mm if stainless steel 316L is used for these wires 2 to provide the wanted generally controllable amount of electrical heat.
• a complete system 1, 8 for heating for example a football field may have several power supplies whose provided powers are each galvanically separated from earth.
• Stabile and accurate control of current to the lattice-strips can take place by measuring the total current delivered to power distributors 9 and by feeding back a total current related control signal via the microcontroller ⁇ to the associated control input 8-1 of the power supply 8 concerned.
• the wire ends 2-1, 2-2 of the wires 2 are connected electrically to the power distributors 9. This may be achieved by means of arranging these distributors as parts which clamp the wire ends or as an alternative the power distributors may have longitudinal and/or transverse hollows 10 meant to clamp or cast therein the wire ends 2-1 and 2-2 respectively. This minimises contact resistances and heat generated locally therein, as substantial currents will flow through each lattice 1. This also results in precise lengths and resistance values along the lattice strips 4, which promotes an even and balanced heat generation over the length and width of the strips.
• Figs. 1 and 2 also shows how the power distributors 9 are via electric terminals A and B connected to the power supply 8 of fig. 2.
• Fig. 1 also shows how lattice strips meander from a left distributor 9 at terminal A to the right to a prolonged distributor 9 and then back to a further left distributor 9 to terminal B in order to make contact at terminals A and B which are preferably powered on one side of the underground only.
• the distributors are outlined to conduct currents of hundreds of amperes.
• the electric power supply 8 will have a rectifier circuit which may be arranged with microprocessor controlled semiconductors to control the DC current for the first type wires 2 in a way known per se.
• DC control is relatively simple in terms of required hardware if duty cycle and/or amplitude of the then block shaped current is controlled.
• the power supply 8 may be connected to solar panels and/or electric wind mills for providing auxiliary electric power.
• Solar panels advantageously generate DC power in which case convertors become superfluous if connected to a DC system 1.
• lattice widths and spacing between neighbouring strips of lattice may be chosen to save material costs, without jeopardising the requirements concerning the minimum and maximum wanted power per square metre.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Road Paving Structures (AREA)

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Applications Claiming Priority (1)

Publications (2)

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• 2022
  • 2022-02-01 PL PL22706260.1T patent/PL4473797T3/pl unknown
  • 2022-02-01 FI FIEP22706260.1T patent/FI4473797T3/fi active
  • 2022-02-01 EP EP22706260.1A patent/EP4473797B1/en active Active
  • 2022-02-01 WO PCT/EP2022/052284 patent/WO2023147836A1/en not_active Ceased
  • 2022-02-01 DK DK22706260.1T patent/DK4473797T3/da active

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