WO2009016394A1

WO2009016394A1 - Apparatus and method for dispersing frost and fog

Info

Publication number: WO2009016394A1
Application number: PCT/GB2008/050094
Authority: WO
Inventors: Michael Allen
Original assignee: Michael Allen
Priority date: 2007-07-27
Filing date: 2008-02-13
Publication date: 2009-02-05
Also published as: GB2451308A; GB2451308B; GB0714859D0; GB2451297A; GB0813315D0; GB0802648D0

Abstract

An apparatus for raising the temperature of air in an environment comprises a heater, a mixing chamber, an ambient air fan and at least one vortex generating element. The heater heats ambient air and delivers so heated air to the mixing chamber and the ambient air fan delivers ambient air into the mixing chamber. The mixing chamber includes at least one outlet and one of the at least one vortex generating elements is associated with the at least one outlet.

Description

Apparatus and Method for Dispersing Frost and Fog

Field of the Invention

The present invention relates to an apparatus and method for dispersing frost and fog and in particular to an apparatus for introducing heated air into an environment.

Background of the Invention

The presence of frost or fog can present problems to a number of economic activities. For example, in the growing of frost susceptible crops, such as citrus fruits, vines for example, if the water content of the fruit freezes the fruit is rendered unsuitable for commercial use. Frost damage occurs when the air is calm. As the ground loses its heat the air immediately above cools and settles through the trees or vines. If the air is sufficiently cold and remains in contact with the fruit for long enough frost damage will occur. All that is required to prevent frost damage is to ensure that the fruit does not remain in contact with sufficiently cold air for the time required to cause frost damage. It does not matter if the fruit is in cold air so long as periodically the temperature of the air in contact with the fruit is raised from time to time for sufficient a period.

The causes of frost damage are well known and will not be described in any greater detail herein. Various solutions have been proposed to prevent its occurrence. One solution is referred to as "smudging" and consists of placing drums of oil around an orchard and lighting oil in those drums to generate heat and thereby raise the heat of the air surrounding the fruit in the orchard. This technique is expensive, not particularly effective (due to the heat generated rising in a narrow column and failing to heat around the fruit), damages the environment due to the burning of fossil fuels, which in the case of smudging involves particularly inefficient combustion giving off large volumes of smoke, and the high labour costs associated with tending to smudge pots. Another solution proposed involves siting turbines in the fruit orchard. However, such turbines only serve to stir the air, their mode of operation being to mix warm air in the strata above tree or vine level with the cold air found at tree or vine level. If the air in the strata above tree or vine level is sufficiently warm that the mixed air is above freezing point frost damage in the fruit will not occur. However such a system cannot protect the fruit against frost damage if the air above tree or vine level is not sufficiently warm to raise the mixed air above freezing point. Further, the turbines used require powerful engines to drive them and hence consume large quantities of fuel.

Another practical solution employed by fruit growers is to hire helicopters to fly over their orchards during weather conditions likely to cause frost damage. The action of the helicopter mirrors that of the turbine insofar as the down-draft causes the cold air at low level to mix with warmer air at higher levels. Such action is extremely expensive.

Another solution involves releasing warm water into the air in the orchard at around the height of the fruit in the orchard. However, this requires large volumes of water and the infrastructure associated with the delivery of water. One example of such a system is described in Russian patent application no 2060640.

Another solution to the problem is described in FR 2787290 comprises a J shaped conduit which houses a fan and draws warm air at a high level and directs the said warm air to a low level, for example the level of grape vines. The device may include a heater so that crops may be protected against frost damage when the temperature of air at higher levels is insufficiently warm to prevent the occurrence of frost damage.

Yet another solution to the problem is described in US 4513529 which describes a trailer mounted apparatus for delivering heated air into a fruit growing orchard. The device comprises a plurality of fans which draw air in from an upper opening and force the air out at a lower level. Burners are located in the path of the air, causing the temperature thereof to rise. The vehicle is moved about in the orchard at a speed to cover about sixty acres per hour.

Yet another solution to the problem is described in JP 4281720. In this document ambient air is taken in at a level close to the ground and heated by means of a burner. The heated air is released at a level above the air intake.

The solutions to the problem of frost damage in fruit described in US 4513529, FR 2787290, and JP 4281720 all provide apparatus which blow warmed air into an environment. They all suffer the problem of inefficient mixing of the warmed air emitted from the apparatus with the ambient air liable to cause frost damage. Further, in each case the air that is warmed is all the air that is moved by the fans of each apparatus. Such an arrangement may not be the most efficient means of delivering warmed air into an environment where the effects of frost are to be alleviated.

It therefore would be desirable to provide an improved device for releasing warmed air into an environment.

The presence of fog can be dangerous and can lead to certain activities, such as the taking off and/or landing of aircraft, being prevented.

Surprisingly, it has been found that a device according to the invention, as well as alleviating the effects of frost, is capable of dispersing fog.

Fog forms when the difference between the air temperature and the dewpoint temperature is 3 degrees C or less. By warming the air such that the difference between the air temperature and the dewpoint temperature is greater than 3 degrees C fog will be dispersed.

Airports are often closed due to the presence of fog, it not being safe to take off during foggy conditions, causing great economic loss. Further, fog causes significant disruption to road traffic and often leads to collisions. In the case of runways the economic loss associated with closure may be so significant as to render the use of multiple devices according to the invention along the length of a runway desirable.

The usefulness of the apparatus of the invention in relation to fog is not limited to its use on aircraft runways. The device may be used anywhere that an aircraft is designed to be landed (for example a helipad, or a temporary landing site). Further, the apparatus of the invention may be used effectively on roads at locations where fogs patches are known to form.

Summary of the Invention

According to the present invention there is provided an apparatus for raising the temperature of air as specified in Claim 1.

According to a second aspect of the invention there is provide a method of preventing frost damage in a crop a specified in Claim 9.

According to a third embodiment of the invention there is provided a method of defrosting an ob_ject as specified in Claim 11.

According to a fourth embodiment of the invention there is provided a method of dispersing frost a specified in Claim 12.

Preferred features of the invention are described in the claims depended on Claims 1, 9, 11 and 12, and in the description and the drawings herein.

With regard to the vortex generating element, it has been found that a triangle, and in particular a delta has the best vortex shedding properties. With regard to the nozzle, this provides the advantage that the vortex of warm air exiting the apparatus may be directed in a desired direction. The desired direction may be set by the angle of the outlet of the nozzle with respect to the inlet thereof. A greater degree of selection of direction of the warm air exiting the apparatus is provided by mounting the nozzle so that it may be moved to different orientations with respect to the outlet of the mixing box.

By mounting the apparatus on a vehicle (a trailer in the illustrated examples) provides the advantage that larger area of orchard may be warmed than if the apparatus were static.

The devices of the prior art which blow warmed air into an environment where the temperature is to be raised place the heating element (typically a burner) down stream of a fan which provides all the air to be introduced into the environment. Hence, the burner must be capable of functioning in an environment with a significant air flow, which could cause the burner to blow out. Hence a special burner capable of functioning in such air flows may be required. Further, it is desirable that heated air exiting the device should not be too hot, as this would cause the said air to rise rapidly and fail to alleviate frost conditions in large parts of the environment. Further, fruit contacted by such air might be damaged if the temperature thereof is too great. The present invention separates the functions of heating air and the provision of a large volume of air. This provides the advantage that readily available heaters may be used, the temperature of the air entering the environment may be easily and accurately controlled and the possibility of blow out of a heater is significantly reduced.

Brief Description of the Drawings

In the drawings, which illustrate preferred embodiments of the invention, and which are by way of example:

Figure 1 is a side view of an apparatus according to the invention; Figure 2 is a plan view of the apparatus illustrated in Figure 1;

Figure 3a is a side view of an ambient air transfer duct of the device illustrated in Figures 1 and 2;

Figure 3b is an end view of the ambient air transfer duct illustrated in Figure 3a;

Figure 3c is an end view of an air mixing box of the device illustrated in Figures 1 and 2;

Figure 3d is a schematic representation of a nozzle for attachment to an outlet of the air mixing box illustrated in Figure 3c;

Figure 3e is a side view of a fin for generating a vortex;

Figure 4 is a side view of the ambient air transfer duct illustrated in Figure 3b attached to the air mixing box illustrated in Figure 3c;

Figure 5 is a plan view of the components illustrated in Figure 4; and

Figure 6 is a front view of the air mixing box illustrated in Figures 4 and 5.

Detailed Description of the Preferred Embodiments

Referring now to Figures 1 and 2, there is illustrated an apparatus 1 for generating warmed air which may be directed into a citrus grove for example. The apparatus 1 comprises a twin axle trailer 2 which provides a bed 3 on which other elements of the apparatus are mounted. A pair of ambient air fans 4 are connected to ambient air ducts 5, which debouch into air mixing chambers 6. Also mounted on the bed 3 is a pair of heaters 7, each comprising two heater units in the form of gas space heaters. The bed 3 provides space for gas bottles 8, which supply fuel to the heaters 7. The ambient air fans 4 and the heaters 7 require power, which in the present example is electrical power supplied by generator sets 9. Two generator sets 9 are provided so that the two arrangements of ambient air fan 4 and heater 7 may be operated independently of one another. Of course the two generator sets may be replaced by a single generator set with appropriate control gear to provide for independent control of the respective arrangements of fan 4 and heater 7.

The space heaters of each heater 7 are provided with fans which move approximately 109 cubic metres/minute or 6559 cubic metres /hour (3848 cubic feet/minute or 230,956 cubic feet/hour) of air and deliver 164kw (557,600 BTUs) of heat to the mixing chambers 6. The ambient air fans 4 each deliver 74 cubic metres/minute or 4454 cubic metres/hour (2614 cubic feet/minute or 156,840 cubic feet/hour) of air to the mixing chamber 6.

The combined output of air flow from the space heaters and the ambient air fans is 367 cubic metres /minute or 22027 cubic metres/hour (12926 cubic feet/minute or 775,592 cubic

The mixing chamber 6 as illustrated in the example comprises a first part 6a which is substantially rectangular in cross-section and a truncated part 6b which has a first cross-section corresponding to the cross-section of the first part 6a at the point where the two parts are _joined together and a second cross-section substantially circular in shape at its outlet. The outlet 6b is provided with a flange 6c to which a nozzle illustrated in Figure 3d may be attached.

In the embodiment illustrated in Figures 1 and 2, a fin 10 which is preferably delta shaped is attached to the flange 6c of the mixing chamber 6.

The ambient and heated air delivered to the mixing chambers 6 are thoroughly mixed and debouch through the outlet 6d. It is desirable that the warm air exiting the outlet 6d be mixed as thoroughly as possible with the air in the environment which is to be warmed. The fin 10 is provided to generate a vortex in the warmed air exiting the said outlet 6d. The swirling motion of the vortex causes the warmed air to mix with the ambient air of the environment to be warmed much more effectively than merely blowing warmed air into the said environment through the outlet 6d.

Figures 3a to 3e illustrate constructional elements of the air delivery apparatus. Figures 3a and 3b illustrate the ambient air duct 5 which connects the output of the ambient air fan 4 to the mixing chamber 6. In order to reduce energy losses in the ambient air transported through the duct the corners 5a are curved.

Figure 3c is a rear view of the mixing chamber 6 and is provided with an ambient air inlet 11 and a pair of spaced apart heated air inlets 12 each of which connects to one of the space heaters of a heater 7.

Figure 3d illustrates a nozzle 13 which attaches to the flange 6c. To attach the nozzle 13 the flat end of the nozzle is simply pushed onto the said flange. The function of the nozzle is to direct the vortex of warmed air exiting the mixing chamber to follow a certain path. The position of the nozzle 13 may be adjusted axially with respect to the flange 6c. Adjustment may be facilitated by a rotatable mounting arrangement, by having a plurality of discrete positions or simply by removing the nozzle and pushing it back onto the flange with the outlet of the nozzle at a different orientation.

In Figure 3e there is shown the fin 10 which is connected to the outlet of the mixing chamber to cause warmed air exiting the nozzle to form a vortex. A lower edge of the fin 10 is itself provided with a flange 10' in which are located holes 10" which provide for attachment of the fin 10 to the flange 6c using suitable fasteners.

Figures 4 to 6 illustrate the elements of the apparatus which transfer and mix ambient and heated air. In Figure 4, the fin 10 is illustrated as being attachable either to the flange 6c, or to the inner surface of the nozzle 13. The fin 10 may be attached to the flange 6c whether a nozzle 13 is provided or not.

By mounting the apparatus so that it is portable, for example a trailer which may be towed as in the illustrated embodiment, the apparatus may be moved through a citrus grove, orchard or vineyard. The swirling air exiting the apparatus warms the air in the vicinity of the crop which is likely to be spoiled by frost damage. As mentioned above, it is not necessary that the air surrounding the fruit be held above a threshold temperature at all times. What is required is to warm the air sufficiently that the fruit is never exposed to cold air for sufficient time to result in frost damage. As such a single apparatus may serve a large number of trees or vines and may in fact be able to serve a number of rows of vines. Nevertheless, for an apparatus of the invention there is a limit to the number of trees or vines which can be served and that limit will depend on the harshness of frost at a particular instance. Where a citrus grove, orchard or vineyard is so large that one machine cannot prevent frost damage throughout, additional machines may be deployed each serving a different area.

Use of the device is not limited to the avoidance of frost damage in crops. The device may be used to de-frost aircraft or other machines. When used as such, the apparatus is positioned so that warmed air exiting the outlet 6d will pass around the aircraft raising the temperature of the air immediately around said aircraft, and heating the material from which the aircraft is made.

Where the device is used to disperse fog, for example on a runway, it is likely that a number of devices would need to be place alongside the runway.

Where the device is to be used on a road side to disperse fog in an area known to be susceptible to the formation of fog, one or more devices would need to be positioned so that warmed air is directed to the pocket where fog accumulates. An apparatus as illustrated in the drawings may be moved about to where fog is forecast to occur.

Claims

1. An apparatus for raising the temperature of air in an environment comprising a heater, a mixing chamber, an ambient air fan and at least one vortex generating element, wherein the heater heats ambient air and delivers so heated air to the mixing chamber and wherein the ambient air fan delivers ambient air into the mixing chamber, and wherein the mixing chamber includes at least one outlet and one of the at least one vortex generating elements is associated with the at least one outlet.

2. An apparatus according to Claim 1, wherein the mixing chamber outlet is provided with a nozzle element, and wherein the nozzle element directs the warmed air exiting from the mixing chamber.

3. An apparatus according to Claim 2, wherein the vortex generating element is mounted in said nozzle.

4. An apparatus according to any preceding claim, wherein the vortex generating element is triangular in shape.

5. Apparatus according to Claim 4, wherein the vortex generating element is a delta.

6. An apparatus according to any preceding claim, wherein the heater comprises two heater units, each heater unit debouching into the mixing chamber.

7. An apparatus according to any preceding claim, further including a platform mounted on axles, a platform and a towing element.

8. An apparatus according to any preceding claim, further comprising a fuel supply for said heater.

9. An apparatus according to any preceding claim, further comprising an electricity supply for said fan.

10. An apparatus according to any preceding claim, comprising a pair of heaters, a pair of mixing chambers and a pair of ambient air fans, wherein each heater heats ambient air and delivers the so heated air to a respective one of the pair of mixing chambers and each ambient air fan delivers ambient air into a respective one of the mixing chambers.

11. A method of preventing frost damage in crops comprising the steps of: introducing air warmed by an apparatus as claimed in any preceding claim for period of time sufficient to raise the temperature of air surrounding the crop to a level above a threshold temperature at which frost damage might occur, and maintaining the air surrounding the crop at the raised temperature for sufficient a period of time to prevent frost damage occurring in the crop.

12. A method of preventing frost damage in crops according to Claim 9, wherein the apparatus is as claimed in Claim 5, and the method includes the step of moving the apparatus about within a cropped area.

13. A method of defrosting an ob_ject comprising the step of increasing the temperature of the air surrounding the object to a level sufficient to raise the temperature of surfaces of the object above freezing point.

14. A method of dispersing fog comprising the step of introducing air warmed by an apparatus as claimed in of Claims 1 to 11, for a period of time sufficient to raise the temperature of the environment in a designated area where fog is present by at least three degrees C and continuing to introduce such warmed air for the period of time when fog is required to be dispersed.