RU2095967C1 - Portable heating apparatus for protected ground - Google Patents

Abstract

FIELD: agriculture and municipal engineering, in particular, air heating in greenhouses and film coverings, rural dwellings and animal houses. SUBSTANCE: apparatus has housing 1 made from electrically insulating and heat-insulating material. Housing 1 incorporates heating tubular member 2 filled with current-conductive liquid 3 (water), compensator 4 for accumulating excessive current-conductive liquid produced during heating, and heat-exchanger 5. Heat-exchanger 5 is made from detachable thin-walled metal pipes connected with housing 1 through upper branch pipes 6 and lower branch pipes 7 to define closed channel extending along periphery in vertical plane from housing 1. Length of heat-exchanger channel sides exceeds its height on housing 1 between branch pipes 6 and 7 by 3-10 times. Heat-exchanger 5 may have different configuration and number of closed channels, but triangular configuration is preferable, with sides of channels being inclined from housing for an angle of 75-90 deg. Electrode 8 is positioned above lower branch pipes within heating member 2 at distance making 0.1-0.5 of mentioned height. Apparatus heats ground and air by directing safety voltage electric current through current-conductive liquid. When power is cutoff, apparatus serves as pump for supplying excessive air heat produced due to intensive solar radiation to ground without overheating and injure to plants below film covering. Apparatus may also be used to recuperate heat from ground to air during night frosts, when unexpected power source cutoff occurs. EFFECT: increased efficiency in heating protected ground without damage to plants. 2 cl, 8 dwg

Description

 The invention relates to devices designed for heating greenhouses, hotbeds and film shelters, but may find application for heating residential premises and farms in agriculture.

 Known technical solutions for heating protected ground in greenhouses and greenhouses. In some inventions it is proposed to use air as a heat carrier, for example, see A. p. USSR N 1771594, class. A 01 G 9/24, in others water.

 Due to the very high heat capacity of water, more often they offer devices for heating greenhouses and rooms that are designed for the use of water, see A. p. СССр N 338758, cl. F 24 H 1/38; A.S. N 818510, class A 01 G 9/24; A.S. N 906446, CL A 01 G 9/24; A.S. N 1337538, cl. F 24 H 1/00, or French patent N 2422144, CL. F 24 H 1/06, or US patent N 2989959, CL. 126/344.

 Known technical solutions differ in design features and the achieved effect, but in all cases, heated water (coolant) transfers excess heat to the air through a heat exchanger.

 The authors of these inventions offer various structural schemes for heat exchangers, but devices in which heat exchangers are made in the form of separate radiators located around the periphery are referred to analogues, see A.S. USSR N 338758, cl. F 24 H 1/38, or radiator systems having, for example, a triangle shape, see A.s. N USSR 818510, class A 01 G 9/24.

 Known solutions have disadvantages that are the result of either large capital investments required during implementation, which makes them unsuitable for seasonal greenhouses, film shelters, or low efficiency of soil heating.

 Closest to the proposed invention in terms of features and the problem to be solved is a heating device for sheltered soil, known from A.C. USSR N 906446, class A 01 G 9/24, adopted as a prototype.

 The prototype contains a housing consisting of two parts, the upper and lower halves separated by a partition, a heating element in the form of a metal pipe installed in the housing through a gasket of an insulating material, an electrically conductive liquid, which is water containing salt and in which the electrode is placed, heat exchanger and compensator.

 When applying electric current to the electrode, an electric current passes through the electrically conductive liquid, and it heats up. The generated steam is washed by the heat exchanger, and condensate flows into the pipe. The heat exchanger transfers heat to the air environment of a greenhouse or greenhouse, and the soil is heated through the air.

 Soil heating through the airspace is not efficient enough due to local heating of the air in the area where the device is located and lowering the heating temperature in the peripheral areas. It is impossible to warm the soil to higher temperatures in any local places of the same greenhouse.

 These disadvantages are eliminated with the help of the invention, which provides more efficient heating of the air and soil in greenhouses. The technical result is achieved by uniform heating of both the air and soil, including in the necessary places in the greenhouse. The same device allows in passive mode, i.e. when the power is off, accumulate and pump into the soil the excess heat of the air generated in the daytime from the increased flow of sunlight. At night, when for some reason the power is turned off and the air temperature in the risky farming zone may be lower than the soil temperature, the device recovers, i.e. gives back the air heat stored in the ground.

 This result was obtained due to the fact that the portable heating device for protected ground contains a housing, a heating element installed in it in the form of a metal pipe filled with an electrically conductive liquid, with an electrode placed in it with a gap, a heat exchanger and a compensator.

 In this case, the upper and lower pipes are introduced into the housing, which is made of heat-insulating and electrical insulating material, and the heat exchanger is made of removable thin-walled metal pipes connected to the housing through the upper and lower pipes, forming a closed channel on the periphery from the housing so that its plane is located vertically, and the length of the sides of the channel exceeds its height along the body, formed by the distance between the nozzles, 3-10 times.

 The heating element in the form of a metal pipe is fixed without a gap in the housing between its upper and lower nozzles, and the electrode is placed with a gap inside the heating element, above the lower nozzles at a distance of 0.1-0.5 heights in the housing. In the heat exchanger, the sides of the closed channel may have a triangle shape along the contour with a deviation from the body at an angle of 75-90 degrees.

 The given set of signs and each of them individually affect the increase in the efficiency of heating the air and soil in an isolated volume of a greenhouse, greenhouse, or film shelter.

 The recommended ratio of the sides of the closed channel (L, L1) and its height along the body (H), equal to 3-10, creates a stable circulation of heated water in all parts of the channel. However, if the L / H ratio is less than 3, then the heating of the air and soil has a local character, creating convection air flows only in a limited amount of shelter.

 When the ratio L / H> 10, the cooled liquid enters the most remote parts of the closed channel, which, firstly, does not give an effective heating of the soil, and secondly, the circulation of the liquid may cease altogether. In addition, the device becomes non-transportable.

 The thinness of the metal tubes of the heat exchanger determines their relatively small thermal inertia in the transfer of heat from the coolant to the air or soil.

 The electrode is located above the lower nozzles at a distance of 0.1-0.5 height along the body (between the nozzles), which creates a stable "traction", i.e. rising water, thereby ensuring its circulation in a closed channel.

 Going beyond the recommended limits both in that and in the other direction reduces the effectiveness of the invention due to the reduction of "traction" and the deterioration or termination of fluid circulation, i.e. the desired technical result is not achieved.

 So, when the position of the electrode at a distance from the lower pipe is less than 0.1 N, the electrically conductive liquid also warms up in the lower side of the closed channel, which reduces the "draft" of the liquid from it, and the circulation of the liquid will be weak. In the case when the lower pipe of the closed channel departs from the body with a slope upward, within the recommended range of 75-90 degrees, warm water will rise upward along this pipe, and direct circulation of the liquid will become impossible.

 However, if the electrode is placed above the specified limit, i.e. above 0.5 H, then the height of the column of heated liquid in the housing decreases, and the “thrust” created when it rises, which also worsens the direct circulation of the liquid through the closed channel.

 Placing a hollow heating element in the housing without a gap between them allows all liquid to pass only between the electrode and the heating element, where electric current flows. At the same time, the entire fluid flow warms up, any cold flows are not mixed in, so there is a good “traction” and, as a result, a good circulation of the heated fluid through a closed channel and uniform heating of the air and soil under a film cover or in a greenhouse.

 The manufacture of a housing from a material having electrical and thermal insulation properties is necessary for the following reasons. Firstly, it is necessary to ensure electrical safety when working with a heating device. Secondly, the minimum thermal radiation through the heat-insulating walls of the casing provides a stable "traction" of heated water to the upper pipes, that is, stable circulation of the coolant is achieved even at a low temperature of its heating, which is important for plant conservation.

 In addition, the heat-insulating property of the housing contributes to an additional technical result when the portable heating device is in passive mode, i.e. when the power is off. In this state, the device effectively recovers the heat accumulated by the soil in the air during night frosts or accumulates and pumps into the soil the excess heat of the air that occurs during the day even in the cold period in a greenhouse or film shelter from increased sunlight.

 The design of the sides of the closed channel in the form of a triangle enhances the effect of water circulation in the heating device. both in the main mode (heating) and in additional modes (recuperation and cooling of the air with the injection of excess heat into the ground), ensuring the achievement of the declared technical result.

 The inclination of the sides of the closed channel in the range of 75-90 degrees allows you to maintain high circulation and deepen the heating device into the soil at different depths, ensuring its effective heating. Reducing the angle of inclination of the sides of less than 75 degrees, while maintaining their straightness, reduces the ratio of the length of the sides of the channels and the height of the body below three. As justified above, such a constructive solution creates a local nature of air and soil heating in greenhouses and film shelters, and it cannot be considered optimal.

 An increase in the angle of inclination of the sides of the closed channel from the housing by more than 90 degrees impedes the circulation of water, which reduces the efficiency of the heating device.

 The foregoing allows us to state that each sign of the totality is necessary, and the entire set is sufficient to solve the problem.

 The proposed set of features is not identified in the known technical solutions.

 In FIG. 1 is a frontal sectional view of a portable heating device (PUF) for sheltered soil with one peripheral closed channel and a heater in the form of a heating element and an electrode; in FIG. 2 pull-out of the PPU case in place A, increased by 2 times; in FIG. 3 is a frontal sectional view of a polyurethane foam with two symmetrically arranged peripheral closed channels and a heater in the form of a heating element and an electrode; in FIG. 4 is a plan view of a polyurethane foam with four symmetrically arranged peripheral closed channels; in FIG. 5 is a plan view of a polyurethane foam with two peripheral closed channels located at an angle of 90 degrees; in FIG. 6 is a frontal view of the PUF buried in the surface soil; in FIG. 7 frontal view of the PUF, half buried in the ground; in FIG. 8 is a frontal view of the PUF with deepening in the ground of the lower channel of the heat exchanger and the casing protected by a slide of soil.

 The portable heating device for protected ground comprises a housing 1 (see Figs. 1-3) made of a material having electrical and thermal insulation properties. A heating element 2 is installed in the housing in the form of a pipe filled with an electrically conductive liquid 3, a compensator 4 for accumulating excess electrically conductive liquid formed with heating.

 As the electrically conductive liquid 3 can be used drinking, river or other “soft” water having a small natural amount of dissolved salts. If necessary, the introduction of an additional small amount of salt into the water is permissible.

 Heat exchangers 5 of a radiator type, made of removable thin-walled metal pipes connected to the housing 1 through the upper 6 and lower 7 pipes, form closed channels on the periphery of the housing 1 so that their planes are vertical, with the length of the sides of the channels (L.L1 see Fig. 1 and L see Fig. 3) exceeds the height along the body, formed by the distance between the upper 6 and lower 7 pipes, (H), 3-10 times.

 Heat exchangers 5 can have various shapes of closed channels, but it is more expedient to make them along a contour in the form of a triangle with a deviation of the sides of the channel from the housing by an angle of 75-90 degrees.

 The heating element 2 in the form of a metal pipe is installed without a gap in the housing 1 between its upper 6 and lower 7 pipes; the electrode 8 is located above the lower pipes inside the heating element 2 with a gap at a distance from the lower pipe equal to (0.1-0.5) H. Between the upper and lower branches of the closed channels of the heat exchangers 5 can be installed struts 9. To the heater 2 and the electrode 8 is supplied with an electric current of lowered, safe voltage through the contacts 10 passing through the cover 11 of the housing 1.

 Contact 10 for the electrode 8 is laid inside the electrically insulated rod 12. The free ends of the nozzles 6 and 7 are closed by plugs 13.

 The number of pipes 6 and 7 should be paired, and the number of pairs on the housing 1 from one or more.

 A portable heating device is mounted either on the surface of the soil 14 or with a recess as shown in FIG. 6 and Fig. 7. If necessary, the heating device can be closed into the ground 14 on half of the housing 1. To implement additional functions of the device when the power is turned off, excess heat is pumped from the air to the ground, as well as to recover the heat stored in the ground by air, it is necessary to deepen the lower channel of the heat exchanger into the soil and, in addition, it is desirable to spud (fill) the housing with soil, as shown in FIG. eight.

 Portable heating device operates as follows.

Heating mode
The location of the portable heating device in the greenhouse or film shelter and its configuration in plan are determined. Closed channels of heat exchangers are connected to pipes 6 and 7, and plugs 13 are left on excess pipes 6 and 7. The device is installed either above the ground level, as shown in FIG. 1, or the lower side channels of heat exchangers are buried in the ground, as shown in FIG. 6 and FIG. 7.

 An electrically conductive liquid 3 is poured into the housing 1 10-15 mm higher than the upper edges of the nozzles 6. An electric current of reduced safe voltage is supplied to the contacts 10. When the threshold temperature is reached in the greenhouse, the value of which is set by the user of the portable heating device using a temperature sensor (not shown in the figures ), through the heating element 2, the electrically conductive liquid 3 and the electrode 8 passes an electric current. In the gap between the electrode 8 and the heating element 2, electrolysis occurs with heating of the electrically conductive liquid.

 The higher the temperature of heating the water in the gap between the heating element 2 and the electrode 8, which is set within the recommended limits above the lower nozzles 7, the greater the "thrust" created by the column of heated, rising up liquid, which entrains the cooled liquid from the lower sides of the closed channels.

 Warm water from the housing enters the upper side channels of the heat exchangers 5 and, cooling, falls down in the direction from the housing, and then, along the lower channels, to the housing.

 There is a circulation of liquid in the channels of the PUF, warm water heats the thin-walled metal pipes of the heat exchangers 5, and heat is transferred to the environment (air and soil).

 Due to the heat-insulating properties of the housing material, heat dissipation from the housing is minimal. This allows you to get a stable circulation of water even at a low heating temperature of the device, which is important for the safety of plants.

 With air heating in a greenhouse or film shelter, a temperature sensor (not shown in the figures) interrupts the circuit, and the heating of the electrically conductive liquid (water) ceases. After some time, the circulation of liquid created in the channels of the PUF created by electric heating stops.

Recuperation mode
With a sharp and strong cooling of the air, for example during night frosts, the portable heating device can also work in the event of an unexpected absence of electricity in the recovery mode, i.e. return of previously accumulated heat to the air. A prerequisite for this is the deepening of the lower lateral channels of the heat exchangers 5 into the ground and, in addition, it is desirable to earthing (filling) the housing with soil, as shown in FIG. eight.

 Water, having cooled in the upper lateral sides of the closed channels of the heat exchangers 5, acquires a greater density and sinks down to the ground, and warmer water from the housing 1 and the lower side channels of the heat exchangers enters the upper side channels of the heat exchangers. Water circulation occurs, and the stored heat from the soil is intensively transferred to the air. The circulation of water will be the more intense, the greater the difference in temperature between the soil and air.

 The emergence and maintenance of water circulation is facilitated by the fact that the water in the casing is kept warm due to the insulating material of the casing and the heat in the soil hill surrounding the casing.

Cooling mode
In the daytime, from the operation of the heating device or from heating the air in the greenhouse or under the film with sunlight, the power to the heating device is turned off using a temperature sensor (not shown in the figures). In the future, the flow of sunlight and air temperature can increase significantly. The device allows you to cool the air to prevent damage to the plants, and to transfer the excess heat from the air to the ground.

 A prerequisite for this is the deepening of the lower side channels of the heat exchangers 5 into the ground and, in addition, it is advisable to ground (backfill) the housing with soil, as shown in FIG. eight.

 In such a situation, the part of the liquid in the housing is colder than the part located in the upper side channels of the heat exchangers 5 and heated by hot air. In a liquid heated in the upper lateral sides of closed channels, the volume increases and the density decreases. It partially flows into the upper part of the housing of the compensator. The height of the liquid column in the housing increases, and its pressure on the underlying water layers also increases. Under the influence of this pressure, the liquid partially flows from the body to the lower channels of the heat exchangers 5, and from it to the upper side channels until the liquid pressure in the communicating vessels (body and upper side channels) is equalized.

 In the future, this movement of the liquid will be supported, since the incoming water in the upper lateral channels will again be heated from hot air, and in the case where there is no heat influx from the outside due to the soil slide surrounding the case and the heat-insulating properties of the case material, the water will inevitably cool. and its density increases, since heat is transferred to the lower layers by a metal pipe located in the housing (heating element), as well as due to the heat transfer properties of the water itself. Warm water entering the lower side channels transfers heat to colder soil, while the excess heat available in the air is pumped into the soil by the device, like a pump.

 A portable heating device was tested in the conditions of the Moscow region when meeting the requirements for all the features of the proposed technical solution. The total height of the casing was 350 mm, while the height along the casing between the upper and lower pipes was 300 mm. The length of the sides of the closed channels was 900 mm, 2100 mm and 3000 mm. The shape of the sides of the closed channels of the heat exchangers was made in the form of triangles: rectangular, as in FIG. 1, and isosceles, as shown in FIG. 3 The electrode was placed at various distances from the lower pipe, from 30 to 150 mm. An electric current was supplied with a voltage of 12 to 36 volts. The dry weight of the device is about 3 kg. The volume of filled water is about three liters.

 It was established that in the practical activities of gardeners and gardeners convenient for transfer and winter storage, the maximum length of one closed channel of the lateral sides of the heat exchanger 5 should be considered equal to 2.5-3.0 m.

 The proposed device reliably heats a garden greenhouse with an area of 12 square meters and a film shelter with an area of 15 square meters. For large-area greenhouses and hotbeds, 2-3 heating devices are required.

Claims (2)

 1. A portable heating device for sheltered soil, comprising a housing, a heating element installed in it in the form of a metal pipe filled with an electrically conductive liquid, with an electrode placed in it with a gap, a heat exchanger and a compensator, characterized in that in a housing made of electrical insulation and heat insulation material, the upper and lower nozzles are introduced, the heat exchanger is made of removable thin-walled metal pipes connected to the housing through the upper and lower nozzles, forming along iferea from the housing, the closed channel so that its plane is vertical, while the length of the sides of the channel exceeds the height of the housing, formed by the distance between the nozzles, 3-10 times, the heating element is fixed without a gap in the housing between its upper and lower nozzles, and the electrode placed above the lower nozzles at a distance of 0.1 to 0.5 of the height of the housing. 2. The device according to p. 1, characterized in that in the heat exchanger the sides of the closed channel, forming a triangle shape along the contour, are deflected from the body by an angle of 75 90 ^o .

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