WO1980001032A1

WO1980001032A1 - Process and plant for mitigation of night frost impact

Info

Publication number: WO1980001032A1
Application number: PCT/DK1979/000051
Authority: WO
Inventors: Povl Henningsen
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-09-27
Filing date: 1979-11-19
Publication date: 1980-05-29
Anticipated expiration: 1981-05-20
Also published as: FI793620A7; DK142973C; DK428078A; EP0020629A1; BR7908925A; JPS55500891A; NO793725L; DK142973B

Abstract

For mitigation of the impact of in particular the kind of night frost, which may appear in spring and autumn heated air in a continuous, descending stratum is blown at a certain height over the surface of the ground of the area desired protected. When a mist of vapour is laid out above the blown-out stratum of air a larger area is protected against severe night frost.

Description

P R O C E S S A N D P L A N T F O R M I T I G A T I O N O F N I G H T F R O S T I M P A C T .

The invention relates to a process for mitigation of the impact of in particular the kind of night frost, which during calm weather periods may appear in spring and early autumn, by which said process possibly heated air in a continuous, descending stratum is blown at a certain height over the surface of the ground of an area desired protected, as well as to a plant for the performing of the said process.

It is from e.g. US patent applications numbered 2,529,339,

2,691,847 and 2,655,764, from DE provisional patent specification number 1,012,109, and SE patent application number 50,183 known how to protect a cultivated area against night frost by blowing out a continuous, descending stratum of air over the ground. It is in the described manner possible to raise the temperature by the surface of the earth up to 2 degrees C. A further temperature rise may be accomplished by adding to the blown out air heat from a suitably situated source of heat. If, however, in the said manner the temperature is raised to more than approximately 2 degrees C, the aggregate upmoving tendency of the airflows above the area will reduce the area coverage by one half almost, as the protective effect in the outer halv of the area will be wasted.

The unfortunate effect of excessive heating of the air is further enhanced by the thus produced upward moving flow through the suction in of the surrounding colder air.

It is of course possible in such cases to intensify the performance of the applied blower(s), but this will require an increase of energy consumption making the process unprofitable.

It is likewise known e.g. from the above mentioned patent applications SE 60,183 and DE 901,476 to mix the air to be blown out with vapour in that aqueous vapour is blown out, or that water from an atomizer nozzle is led into the air. By way of socalled mist spray plants it is known how to protect e.g. blossoming fruit trees against night frost within relatively short distances. By the use of such plants also a frost-protecting "ice armour" can be established over certain species of plants capable of standing the melting of the ice layer, when the temperature goes up.

In case of the blowing out vaporous, possibly heated air, the area coverage will be reduced due to the weight of the mist respectively vapour. At the same time the outgoing air will be cooled down by the water.

The object of the present invention is to devise a process of the described nature by which it will be possible to protect larger areas against severe night frost than now it has been feasible by way of already known methods.

This is according to the invention achieved by laying out vapour above the blown-out stratum of air. The spreading of vapour separately above the outgoing flow of air offers several advantages. Instead of as in case of known mist spray plants to make the outgoing air heavier and thus reduce the area coverage, the freely superjacent vapour will force the air strata further out, and in that the applied atomizer nozzle will produce water drops of varying size, the smaller and lighter water drops will float longer in the air, so that the blown out stratum of air will remain covered by the vapour to its full extent. The outgoing air will furthermore not, as is the case in already known mist spray plants, be cooled down by the atomized water, which incidentally is supplied in noticeable smaller quantities than in ordinary mist spray plants. Eventually the advanced height over the surface of the ground, where the temperature is lowest, of the vaour will imply, that the hoar formation in the water particles will be effected farther away from the vapour nozzle.

By the known methods of frost protection the air is blown out from a blower centrally situated on the area at a certain height fxorn the ground surface. The blown-out air is sucked in at the base of the applied blower unit, with the possible result that the vapour so to speak is sucked from the blown-put stratum of air, whereby the beneficial effect of the vapour mist is lost within a comparatively slight distance from the nozzle.

It is in the said connection advantageous that according to the invention along the limitation of a mainly circular area air is sucked in, which from the center of the area is blown out radially towards the area limits. It is alternatively according to the invention possible at one end of a mainly rectangular area to suck in air, which has been blown out at the opposite end of the area.

The invention relates, as already mentioned above, likewise to a plant for the performance of the described process.Whereas already known plants contemplating mitigation of night frost incorporate a blower, having at some height from the surface of the ground an exhaust nozzle from whic air is blown out in a downward directed, continous stratum of air, it is according to the invention recommended that a vapour mist nozzle is inserted above the blower, from which water particles in the form of vapour is sprayed out above the blown-out stratum of air.

In order to prevent that the blower will suck down the vapour towards the blown stratum of air, it is according to the invention advantageous that the plant comprise one or several suction units situated at some distance from the blower, from which the air, possibly through a pibe line system, is directed to the blower.

Although a pipe line system inserted between the suction unit(s) and the blower invariably offers full safety that the blower can have no negative influence on the vapour, it has been .proved in practice that it is possible in general to do without this system. In case of a rectangular area the blow and the suction unit can be designed identically as, however, oppositely directed, upright units, with the blower sucking in air below, and the suction unit sucking in air from above.

By the devised process and plant it has been practically demonstrated that an area of 1.36 acres (equal to the Danish measure of one tønde land) growing celery could be effectively protected against approximately 6 degrees C of frost by means of one centrally situated blower with further four in the corners of the mainly rectangular area situated suction units.

Claims

PA T E N T C LA I M S

1. Process for mitigation of the impact of in particular the kind of night frost, which during calm weather periods may appear in spring and early autumn, by which said process possibly heated air in a continuous, descending stratum is blown at a certain height over the surface of the ground of an area desired protected, c ha r a c t e r i z e d i n t h a t a mist of vapour is laid out above the blown-out stratum of air.

2. Process according to claim 1 c h a r a c t e r i z e d i n tha t along the limitation of a mainly circular area air is sucked in, which from the center of the area is blown out radially towards the area limits.

3. Process according to claim 1 c h a r a c t e r i z e d i n th a t at one end of a mainly rectangular area air is sucked in, which is blown out at the opposite end of the area.

4. Plant for the performance of the described process according to claim 1 incorporating a blower having at some height from the surface of the ground an exhaust nozzle from which air is blown out in a downward directed, continuous stratum of air c ha r a c t e r i z e d i n tha t a vapour mist nozzle is inserted above the blower, from which water particles in the form of vapour is sprayed out above the blown-out stratum of air.

5. Plant according to claim 4 c h a r a c t e r i z e d i n t h a t it is comprising one or several suction units situated at some distance from the blower, from which the air, possibly through a pipe line system, is directed to the blower.