The subject of the invention is a plate gravity recuperator, using natural stack draught and directing the used air downwards, prior to leaving the building, for the purpose of release of thermal energy to the air entering the building.

Recuperators, mostly cross-type, known and used on the market, require continuous power supply, resulting in high costs. The price of recuperators is so high than it limits their common use. These recuperators do not require ventilation stacks which is emphasised as cost efficiency at the stage of house construction. However, continuous consumption of electricity during use, in the days of ever increasing energy costs and search for ecological solutions, makes current recuperators little attractive and costly.

Classic gravity ventilation uses the stack draught as well as the fact that the hot air is lighter and capable to float upwards and leave the house in the vertical upward direction through the ventilation stack. Concurrently, almost entire thermal energy of the expelled air is released outside through the ventilation stack. A similar situation takes place in classical fireplaces or in former hearths, where almost entire thermal energy left the room through the stack and only some of the radiated heat remained in the room. Progress in room heating occurred when the flue gases, prior to leaving the hearth, were directed downwards in order to extend their route and increase the surface for the purpose of greater energy accumulation. This is the application in the tiled stoves as well as the contemporary central heating furnaces. The natural stack draught - the bigger the stack, the greater - is strong enough to allow the flames to run up and down several times, releasing a greater part of energy,

The classical gravity ventilation, more costly at the beginning due to construction of stacks and free use, is unacceptable due to complete waste of heating energy. The currently used recuperators are costly in the entire use period and are fully dependent on supplies of electric power. My solution combines advantages of both currently used ventilation systems.

The solution based on the invention refers to the above solutions from tiled stoves and directs the used hot air downwards before it leaves the room for the purpose of transfer of thermal energy to the cold air entering the building. The subject of the invention in the execution example is presented in the form of a drawing, fig. 1, presenting the construction diagram of the gravity recuperator. The hot used air from the building and the cold external air flow interchangeably between multiple plates divided by partitions 9. Each partition has two gap openings, positioned in such a manner that if the upper opening is on the left, the lower must be on the right. Another adjacent partition is set reversely, i.e. the upper gap is on the right, and the lower is on the left. The hot air from the building, flowing in through opening 2 to space 7, enters the gaps in every second partition. Entering the gap, it falls down between two cold plates and releases its heat. Releasing the heat, it becomes heavier and naturally drops down, flowing through the bottom gaps on the right and entering space 12. From this space, already cooled air is sucked out through opening 5 by the stack 13 and expelled outside. The air sucked out by stack 13 causes negative pressure in the entire building, thus causing suction of cold external air through opening 4to space 10 and through the gaps upwards, between the hot plates. Cold air, flowing into the hot plates, initially, as heavier air, is distributed alongthe entire width of the partition. It gradually takes up heat from the adjacent plates and, increasingly hotter and, thus, lighter, it floats upwards. The air, sucked with negative pressure in the building, fails into space 8 and then, through opening 3, inside the building. An additional reason for cold air to enter recuperator, as presented in fig. 5, is the forced flow, including draught, by means of the rotating fan 20, placed on the same axis IS as fan 19, rotating in the duct expelling the air to stack 13. The draught in the stack can be improved with a rotary stack pot. The blades of fan 19 are set in the opposite direction than blades of fan 20. This works like turbocharger in cars.

Since the area of a single plate, usually available in the form of flat metai sheets, is 1000 mm x 2000 mm, and the distance between plates is ca. 10 mm, the more plates, the slower the air flows and the more efficient the energy transfer is. The plates can be also made of foil, preferably aluminium, separated in the middle with small separating rings. According to the solution based on the invention, the air flows very slowly between the plates, as opposed to classical recuperators. Recuperator 1 in newly constructed buildings can form a part of the external wall, as presented in fig. 2, and in already existing buildings it can be mounted on the external wall, as presented in fig. 4.

The hot used air, flowing through inlet 2 to space 7 is separated with partition 6 from the external air, already additionally heated up in space 8. Partition 6, made of metal sheet, the more corrugated, the better its additional heating of air in space 8, right before the inlet to the building through opening 3. Partition 11 has a similar task, separating space 10 of the incoming cold external air through opening 4 from space 12 from which the used air is expelled after it transfers its energy and which is directed to opening 5, and further to stack 13. The U partition preliminarily heats up the air from space 10 from the residues of energy of the air expelled outside. The difference of temperatures between spaces 10 and 12/ similarly to difference in temperatures between spaces 7 and 8 should be minimal, and even more so the lower the number of partitions in the recuperator. Partitions 9 can be positioned in any manner, and sometimes they can be supplemented independently by the user due to the simple structure of the recuperator. In the existing buildings, the outlet from the recuperator can be attached to the existing ventilation ducts 17 and existing stacks 16, as presented in fig. 4.

This recuperator can be also mounted outside buildings, decreasing the amount of external insulation of the recuperator itself, but due to the large size it is recommended to mount it as a part of the external wall, making it almost invisible.

The recuperator is service-free, does not require power supply and can be automatized. In extreme situations or in case of extraordinary needs, it is possible to launch additional electric drive for axis IS, supported with, e.g. solar panels, but this will still account for only a fraction of what a regular recuperator consumes, In periods of absence of the building residents, ducts (2) and (3) can be Socked with gates by means of the electronic central unit.

In case of external temperatures below +2 C, best effectiveness is obtained by means of use of the ground-coupled heat exchanger (GWC) 14 with air inlet 15, as presented in fig. 3. in external temperatures between +2 C and + 18 C, lid 22 can be lifted by means of, e.g. thermostat or electronic control, as presented in fig. 5. Then, the external air bypasses GWC, allowing for its regeneration and fan 20 pumps the air directly from the outside, entering through the tipped lid 22 for exchange in the recuperator.

in temperatures between + 18 C and + 24 C, lid 21, 22 concurrently with lid 23 can be tipped, as presented in fig. 6, allowing not only to bypass GWC, but also the recuperator itself. The hot air will fall directly from space 8 and through inlet 3 to the inside of the building. In this time, fan 20, despite continuous work, will suck the air in through the tipped lid 22 and expel it through the tipped lid 23.

In temperatures below +24 C, lids 21, 22 and 23 can be closed, e.g. by means of a thermostat or electronically, and the air can be cooled inside the building by means of directing the air from GWC to the recuperator.

The invention will significantly reduce power consumption, both in terms of the ventilation process as well as apartment heating costs. The simplicity of operation of the device will reduce the cost of its performance and, at the same time, increase the availability for users. The non-complex structure will allow for production of this recuperator even by small entrepreneurs. With current technical possibilities, the cost of addition of a ventilation stack made of stainless still is low, and visibility of such a ventilation is not detrimental to the building aesthetics, just as in case of collar collectors.