ITMI20131880A1 - PASSIVE THERMAL SHELTER - Google Patents

Description

DESCRIPTION

The present invention refers to a passive thermal control shelter for housing inside it an electrical and / or electronic instrumentation which, being sensitive to heat, requires the control of the climatic conditions of the environment in which it operates in order to function indoors. within a predetermined temperature range.

In particular, reference is made to electrical / electronic equipment which, during normal operation, dissipates heat which, if not properly disposed of, could cause malfunction or failure of the electrical / electronic equipment itself.

In some areas of the planet, for example in desert areas that are difficult to access, the adverse environmental conditions due to high temperatures, high temperature variations between day and night, wind, water, sand, can make air conditioning and ventilation systems extremely vulnerable.

These systems have as their main active elements fans, pumps, chillers and other components which, in order to function, require the availability of electricity and must be subjected to various inspections for ordinary and extraordinary maintenance.

In these circumstances it is preferable to use passive air conditioning systems, which are suitable for maintaining the desired climatic conditions for an environment by exploiting physical phenomena such as natural convention.

The advantages of passive air conditioning systems are to be found in their operation without the need for electrical power in such a way as to allow the electrical / electronic equipment to operate in physical and climatic conditions of absolute safety, without affecting the size and capacity of the source of energy foreseen in situ which can be entirely destined to power the electrical / electronic equipment, and without the need for extraordinary maintenance.

Passive thermal control shelters are known comprising a thermally insulated casing in which a thermal accumulator operating by natural convection connected to a finned heat exchanger operating by natural convection located outside the casing is arranged.

Two systems are known for thermal storage: a first system uses water only, a second system uses water and phase change materials called PCM ("Phase Change Material"), or materials such as paraffins or eutectic salts.

In water-only systems, the thermal accumulator generally consists of one or more tanks in stainless steel, plastic material or other material, positioned just under the casing cap and having such a configuration and size as to occupy the entire cross section at best. of the casing to take advantage of all the available space. The aim is to have as large a surface as possible without increasing the internal dimensions.

This is necessary to ensure that the thermal accumulator has a sufficiently high exchange surface as well as a sufficient volume of water for thermal accumulation.

These water-only systems may involve some drawbacks linked to the fact that the tank, by substantially occluding a cross section of the casing, represents a barrier to the natural circulation of the air inside the casing by convection towards the cap of the casing itself, partially limiting the efficiency of the thermal accumulator whose exchange surface with the air remains mainly that of the external side of the tank bottom. For this reason, to increase the efficiency of the thermal accumulator, the application of an internal heat exchanger formed by steel fins, or other material, which are mainly applied to the external side of the tank bottom to increase the surface, can be envisaged. exchange. The contact between the internal heat exchanger and the accumulator is obtained by means of spot welding, gluing, or mechanical pressure.

However, these solutions adopted for the contact between the internal heat exchanger and the thermal accumulator are not very efficient, especially in environments where the heat exchange is due to natural convection alone without any forced ventilation. In particular, the loss of efficiency is linked to the reduced thermal conductivity obtainable at the contact surface between the internal heat exchanger and the thermal accumulator. In fact, with these contact systems you are never sure of the quality and size of the adhesion between contact surfaces and consequently you are never sure of the efficiency in heat transfer.

The provision of such an internal heat exchanger while increasing the efficiency of the thermal accumulator complicates its construction and assembly process.

To recover the inefficiencies introduced by the contact system between the internal heat exchanger and the thermal accumulator, or when the thermal power to be disposed of is significant, it may be required to increase the volume of the thermal accumulation and the exchange surfaces, and consequently in order not to increase the internal temperature of the shelter, it may be necessary to provide larger tanks which in turn require larger shelters.

This negatively affects the costs of the shelter due to the increase in the consumption of building material of the envelope. Increasing the size / weight of the thermal accumulator means making the construction of the same as well as of the casing that must mechanically support it more difficult and expensive. The technical task proposed by the present invention is therefore to provide a passive thermal control shelter which allows to eliminate the technical drawbacks mentioned in the technical note.

As part of this technical task, an object of the invention is to provide a passive thermal control shelter which allows, with a special construction of the integrated thermal accumulator and internal heat exchanger, the rationalization of the exchange surface and of the volume. of accumulation for the optimization of the efficiency of the shelter.

Another purpose of the invention is to create a passive thermal control shelter with integrated thermal accumulator and internal heat exchanger that has a simple structure, which is easy to make and assemble, compact and light. Still another object of the invention is to realize a passive thermal control shelter which, thanks to the rationalization of the exchange surface and the storage volume and to the optimization of the thermal energy transfer efficiency between the internal heat exchanger and the 'thermal accumulator, allows operation with water only without the need to use phase change materials to increase the storage capacity while keeping the storage volume significantly reduced and therefore the overall dimensions and consequently the cost of the system. Yet another object of the invention is that of realizing a passive thermal control shelter having a construction that facilitates the convection of the air inside it so that it more envelops the thermal accumulation, increases the exchange surface, and optimizes the the volume necessary for thermal storage is better in order to obtain a more compact shelter that has an internal space as close to what is strictly necessary for housing the electrical and / or electronic instrumentation.

The technical task, as well as these and other purposes, according to the present invention are achieved by realizing a passive thermal control shelter comprising a thermally insulated casing, air and water tight, formed by a base, a hat and side walls, at least one heat accumulator operating by natural convection located inside the casing in a position adjacent to the internal side of the cap, at least one heat exchanger inside the casing and integrated with the heat accumulator, at least one finned heat exchanger operating by natural convection located outside the 'casing and above the heat accumulator, connectors arranged across the casing for the fluid connection between the heat accumulator and the external heat exchanger, characterized in that said heat accumulator comprises a first longitudinal fluid collector and a second longitudinal collector of fluid, and long pipes fluid connection channels between the first collector and the second collector, and in that said internal heat exchanger comprises a plurality of longitudinal fins made in one piece with the pipes.

The fins, which define the heat exchanger inside the casing between the air and the fluid present in the thermal accumulator, allow a considerable improvement in the efficiency of the cooling system without implying any construction complication, since the internal heat exchanger is produced directly with the same operation with which the connection pipes of the thermal accumulator are produced.

Advantageously, with an operation of extrusion of a single profile in thermally conductive material, in aluminum, each of the connecting pipes can be made.

With this same extrusion operation, a profile with external grooves can be directly created in correspondence with the fins and the tubular body of each connection tube to further optimize the heat exchange efficiency.

The integrated system formed by the thermal accumulator and the internal heat exchanger made in a single piece has an improved thermal transmission efficiency at the contact surfaces between one and the other.

In this way, the necessary accumulation capacity is guaranteed while keeping the accumulation volume significantly reduced and through an appropriate rationalization of the exchange surface too, water-only operation can be envisaged with the consequence that the system is not only less cumbersome. simpler and ultimately cheaper.

Other characteristics of the present invention are also defined in the subsequent claims.

Further features and advantages of the invention will become more evident from the description of a preferred but not exclusive embodiment of the passive thermal control shelter according to the invention, illustrated for indicative and non-limiting purposes in the attached drawings, in which:

Figure 1 shows a side view of the shelter.

Figure 2 shows a longitudinal section view of the shelter sectioned along the line II-II of Figure 4 when only one thermal accumulator is installed.

Figure 3 shows a cross-sectional view of the shelter sectioned along the line I-I of Figure 4, when only one thermal accumulator is installed.

Figure 4 shows a sectional view of the plan of the shelter sectioned along the line III-III of Figure 1.

Figure 5 shows a longitudinal section view of the shelter sectioned along the line II-II of Figure 4, when two stacked thermal accumulators are installed and connected in cascade.

Figure 6 shows a cross-sectional view of the shelter sectioned along the line I-I of Figure 4, when two stacked thermal accumulators are installed and connected in cascade;

Figure 7 shows a plan view of the thermal accumulator 5. Figure 8 shows a cross-sectional view of one of the tubes of the thermal accumulator that transversely connects the first and second collectors.

Figure 9 shows a cross sectional view of a manifold. With reference to the aforementioned figures, a passive thermal control shelter is shown, indicated as a whole with the reference number 1.

The shelter 1 comprises a casing 2, 3, 4, thermally insulated, sealed against air and water, and possibly made of sand, at least one thermal accumulator 5 operating by natural convection placed inside the casing 2, 3, 4, and at least a finned heat exchanger 6 operating by natural convection located outside the casing 2, 3, 4.

The envelope 2, 3, 4 includes a base 2, a hat 3 and side walls 4, consisting of multilayer panels having an external corrosion-resistant aluminum frame, and at least one internal layer of thermally insulating material.

The heat accumulator 5 is located adjacent to the internal side of the cap 3, while the finned heat exchanger 6 is located adjacent to the external side of the cap 3.

The heat accumulator 5 is positioned with its main lying plane oriented horizontally, while the finned heat exchanger 6 is positioned with its main plane oriented with an inclination such as to form an acute angle with respect to the lying plane the thermal accumulator 5 .

The heat accumulator 5 is in fluid communication with the heat exchanger 6 through connectors 7 arranged through the cap 3 and connecting the heat accumulator 5 and the external heat exchanger 6.

Advantageously, the thermal accumulator 5 comprises a first longitudinal fluid manifold 8 and a second longitudinal fluid manifold 9 which face each other at their opposite lateral face 8a, 9a, and longitudinal metal connecting pipes 13 of fluid between the first manifold 8 and the second manifold 9.

Preferably the first manifold 8, the second manifold 9 and the tubes 13 have an internal cross section of passage of constant width along their entire length.

The tubes 13 are arranged transversely between the opposite lateral faces 8a, 9a of the first manifold 8 and the second manifold 9 and are laterally mutually spaced in such a way as to allow the passage of air in the space that opens between them. The thermal accumulator 5 is integrated with a heat exchanger inside the casing 2, 3, 4.

The internal heat exchanger comprises a plurality of longitudinal metal fins 15 external to the tubes 13 and made in one piece with the tubes 13.

The fins 15 are longitudinally arranged in the longitudinal direction of the tubes 13.

The external surface of both the tubes 13 and the fins 15 advantageously has longitudinal grooves 16, 17 laterally spaced with a regular pitch to increase the overall heat exchange surface.

Preferably the grooves 16 are straight and affect the entire outer surface of the tubes 13 and the grooves 17 are straight and affect the entire outer surface of the fins 15.

The sum of the external height of the tubes 13 and the fins 15 is substantially equal to and in any case not higher than the external height of the first manifold 8 and the second manifold 9.

The tubes 13 then develop entirely inside the generators of the opposite side faces 8a, 9a of the first manifold 8 and of the second manifold 9.

The tubes 13 preferably have a quadrangular shape in cross section and have the fins 15 in correspondence with all their four lateral faces 13a, 13b, 13c, 13d.

The tubes 13 have in particular four flat lateral faces 13a, 13b, 13c, 13d from which the fins 15 extend orthogonally, and the fins 15 in turn are flat and of equal height and are uniformly distributed over the entire external surface extension. of the four flat lateral faces 13a, 13b, 13c, 13d of the tubes 13.

Of the flat side faces 13a, 13b, 13c, 13d of the tubes 13, two opposite side faces have a horizontally oriented lying plane and the other two opposite side faces have a vertically oriented lying plane.

Advantageously, each tube 13 is made from a single extruded profile, preferably in aluminum.

The first manifold 8 and the second manifold 9 preferably have a quadrangular shape in cross section with four flat side faces.

Of the flat lateral faces of the first manifold 8 and of the second manifold 9, the two lateral faces 8a, 9a have a vertically oriented lying plane together with the opposite side face 8b, 9b, and the other two opposite lateral faces have an oriented lying plane horizontally.

Also the external surface of the first manifold 8 and of the second manifold 9 preferably has longitudinal grooves 18, 19 laterally spaced with a regular pitch to increase the overall heat exchange surface.

The longitudinal grooves 18, 19 are straight and preferably affect all the side faces of the first manifold 8 and of the second manifold 9.

Advantageously, the first manifold 8 is also made from a single extruded profile, preferably in aluminum, and similarly the second manifold 9 is also made from a single extruded profile, preferably in aluminum.

The optimization of the efficiency of the thermal accumulator 5 is also ensured by the special proportioning of its constituent elements.

In particular, the width of the internal cross section of the passage of the pipes 13 is not less than 40% of the width of the internal cross section of the passage of the first manifold 8 and of the second manifold 9.

Furthermore, the spacing pitch between the grooves 16 of the tubes 13 is comprised between 5/100 and 20/100 of the spacing pitch between the fins 15, and the spacing pitch between the grooves 17 of the fins 15 is comprised between 5/100 and 10/100 of the height of the fins 15. Furthermore, the dimensioning of the pipes 13 is extremely advantageous, which have a suitably wide passage cross section to increase the volume of thermal accumulation and a suitably wide external perimeter to increase the exchange surface: in particular the the value of the passage cross section is equal to 29200 mm <2> +/- 10% and the value of the perimeter is equal to 2400 mm / - 10%.

The operation of the shelter 1 in an environment where a strong temperature excursion is expected between the hot day and the cold night is briefly as follows.

In a thermodynamic system, the casing 2, 3, 4 is similar to a resistance, the heat exchanger 6 to a transistor, and the thermal accumulator 5 to a capacity.

In fact, the envelope 2, 3, 4 acts to reduce the heat exchange between the outside and the inside of the shelter 1.

The heat exchanger 6 acts to transfer only during the night from the inside to the outside of the shelter 1 the heat generated by the electrical / electronic equipment and accumulated during the day by the thermal accumulator 6. The heat transfer is carried out through the fluid, generally water, circulating by natural convection in the hydraulic circuit formed by the heat accumulator 5 and the heat exchanger 6.

Finally, the heat accumulator 5 acts to accumulate the heat during the day when the external temperature is higher than the internal temperature of the shelter 1. This has the purpose of preventing the internal temperature of the shelter 1 during the day from rising beyond a desired value. maximum.

During the day, the heat produced inside the shelter 1 cannot be transferred to the outside and the only way to avoid a high rise in the internal temperature of the shelter 1 is therefore to accumulate the heat produced in the thermal accumulator 5.

During the day, therefore, there is no circulation in the hydraulic circuit since the warmer and therefore lighter water is found in the heat exchanger 6 located above the thermal accumulator 5, since the outside air temperature is higher than that of the air inside the shelter 1.

Only during the night does the passive cooling system become a real natural heat engine that uses the temperature gradient between a hot source (the water in the heat accumulator 5 heated by the heat dissipated by the electrical / electronic equipment) and a source outside (outside air). The work of this natural heat engine is used to move the water of the hydraulic circuit whose hottest component flows upwards from the heat accumulator 5 to the heat exchanger 6 and the colder component flows downwards from the heat exchanger 6 to the thermal accumulator 5. The circulation just described allows a progressive cooling of the water present in the thermal accumulator 5 which, at the end of the overnight regeneration period, is able to accumulate heat again for the following day. The activation of the circulation is due to the fact that the temperature of the external air during the night is lower than that of the air inside the shelter 1. The water in the heat exchanger 6, in contact with the external air, becomes more cold and heavy water present in the thermal accumulator 5, inside the shelter 1, triggering the movement of the fluid.

The shelter conforming to the present invention allows you to flexibly adapt the cooling system to the thermal power to be disposed of, and in particular it allows you to increase the thermal storage capacity without increasing the size of the envelope. In this regard, it should be noted, in fact, that it is possible to provide for the installation of a first thermal accumulator 5 and of at least a second thermal accumulator 5 stacked one above the other and in cascade fluid communication without the lower heat penalizes the performance of the upper heat accumulator. In fact, when the air inside the envelope heats up, it can rise towards the hair 3, interact with the thermal accumulator 5 placed further down, then rise further through the free spaces present between the connection pipes 13 of the thermal accumulator 5 placed lower until you reach the heat accumulator 5 located at the top.

This solution avoids increasing the plan dimensions of the shelter with considerable savings in product, packaging, transport and installation costs.

The passive control shelter thus conceived is susceptible of numerous modifications and variations, all falling within the scope of the inventive concept; furthermore, all the details can be replaced by technically equivalent elements.

In practice, the materials used, as well as the dimensions, may be any according to the requirements and the state of the art.

Claims (15)

CLAIMS 1. Passive thermal control shelter (1) comprising a thermally insulated, air and watertight enclosure (2, 3, 4), formed by a base (2), a cap (3) and side walls ( 4), at least one thermal accumulator (5) operating by natural convection placed inside the casing (2, 3, 4) in a position adjacent to the internal side of the cap (3), at least one heat exchanger inside the casing (2, 3 , 4) and integrated with the thermal accumulator (5), at least one finned thermal exchanger (6) operating by natural convection located outside the casing (2, 3, 4) and above the thermal accumulator (5), connectors ( 7) arranged through the casing (2, 3, 4) for the fluid connection between the heat accumulator (5) and the external heat exchanger (6), characterized in that said heat accumulator (5) comprises a first collector longitudinal fluid (8) and a second longitudinal fluid manifold (9), and longitudinal tubes li (13) for fluid connection between the first manifold (8) and the second manifold (9), and by the fact that said internal heat exchanger comprises a plurality of longitudinal fins (15) made in one piece with the pipes ( 13). 2. Passive thermal control shelter (1) according to the preceding claim, characterized in that said fins (15) are arranged externally to the tubes (13). 3. Shelter (1) with passive thermal control according to the preceding claim, characterized in that said fins (15) are arranged longitudinally in the longitudinal direction of the tubes (13). 4. Shelter (1) with passive thermal control according to any preceding claim, characterized in that said first longitudinal fluid manifold (8) and said second longitudinal fluid manifold (9) face each other in correspondence with one of their opposite side faces (8a, 9a), and in that said longitudinal connecting tubes (13) are arranged transversely between said opposite side faces (8a, 9a) and are laterally mutually spaced. 5. Shelter (1) with passive thermal control according to any preceding claim, characterized in that each connecting tube (13) is made from a single extruded profile. 6. Shelter (1) with passive thermal control according to any preceding claim, characterized in that the external surface of both said tubes (13) and said fins (15) has longitudinal grooves (16, 17) laterally spaced with regular pitch to increase the overall heat exchange surface. 7. Shelter (1) with passive thermal control according to any preceding claim, characterized by the fact that said first manifold (8), said second manifold (9) and said connection pipes (13) have an internal cross section of passage of constant amplitude for their entire length, by the fact that the external height of said tubes (13) is substantially equal to the external height of said first manifold (8) and of said second manifold (9), and by the fact that said tubes (13 ) extend entirely inside the generatrices of said opposite side faces (8a, 9a) of said first manifold (8) and of said second manifold (9). 8. Shelter (1) with passive thermal control according to any preceding claim, characterized in that the width of the internal cross section of passage of said pipes (13) is not less than 40% of the width of the internal cross section of passage of said first manifold (8) and of said second manifold (9). 9. Shelter (1) with passive thermal control according to any preceding claim, characterized in that the spacing pitch between said grooves (16) of the tubes (13) is comprised between 5/100 and 20/100 of the spacing pitch between said fins (15), and the distance between said grooves (17) of said fins (15) is comprised between 5/100 and 10/100 of the height of the fins (15). 10. Passive thermal control shelter (1) according to any preceding claim, characterized in that said connection tubes (13) have a quadrangular shape in cross section and have said fins (15) in correspondence with all their four lateral faces ( 13a, 13b, 13c, 13d). 11. Shelter (1) with passive thermal control according to the preceding claim, characterized in that said tubes (13) have four flat lateral faces (13a, 13b, 13c, 13d) from which said fins (15) extend orthogonally, being a uniform distribution of said fins (15) is provided for the entire external surface extension of said four flat side faces (13a, 13b, 13c, 13d). Passive thermal control shelter (1) according to any preceding claim, characterized in that the external surface of said first manifold (8) and of said second manifold (9) has longitudinal grooves (18, 19) laterally spaced with regular pitch to increase the overall heat exchange surface. Passive thermal control shelter (1) according to any preceding claim, characterized in that said thermal accumulator (5) is made of aluminum. 14. Passive thermal control shelter (1) according to the preceding claim, characterized by the fact of having a first thermal accumulator (5) and a second thermal accumulator (5) stacked on top of each other and in cascade fluid communication . 15. Thermal accumulator (5) for shelter (1) with passive thermal control integrated with a heat exchanger, characterized in that said accumulator comprises a first longitudinal fluid collector (8) and a second longitudinal fluid collector (9) facing to the first manifold (8) in correspondence with their opposite lateral faces (8a, 9a), and longitudinal tubes (13) for connecting the fluid between the first manifold (8) and the second manifold (9), said connection tubes (13) ) being arranged transversely between said opposite side faces (8a, 9a) and being laterally mutually spaced, and by the fact that said heat exchanger comprises a plurality of longitudinal fins (15) made in one piece with the tubes (13).