Presentation

ANTIFROST TECHNOLOGY

 

RADIANT FROST AND THE AIR MIXER PROTECTION

Frost is the result of the natural phenomenon of temperature drop to 0 °C or even lower. Temperatures of this level cause damage to agricultural crops and eventually to the orchard itself (see photographs 1 and 2). More specifically, low temperature causes freezing and consequent breaking of fluids inside the plant. This destroys the whole plant or part of it.

 Radiant frost is caused as follows: at day, soil and trees are heated by sun rays and store heat. At night, soil and trees radiate losing the accumulated heat. Thus their won temperature and that of the surrounding air drops rapidly. Cold air, being heavier, moves downwards near the ground and creates frost. Due to the sudden drop of temperature, thermic balance cannot be achieved. In this way the "thermic inversion" phenomenon takes place, which means that the air in higher levels remains warmer, creating a "thermic cieling" approx. 10-15 m. above ground level. This condition mostly occurs during the first hours of the day.

 Air mixer role is to absorb war air, bring it downwards to the ground and mix it with cold air by forced circulation. Mixing of war to cold air results to an increse in temperature. Air mixer effectiveness increases as the existing temperature difference becomes higher. In other words, high temperature during the day will result to better effects of the air mixer. These can be seen in the relevant sketches.

 

 antifrost 1.1 antifrost 1.2  antifrost 1.3 

 

The results of radiant can be seen in the following pictures:

 antifrost 1.4

If frost is present during Fall the result is fruit loss

    

 antifrost 1.5

If frost is present during Spring the result is total destruction of the plantation


ESTIMATION AND SHAPE OF PROTECTED AREA

 The area protected by an air mixer is dependent on four factors: a) swept are of blades, b) blade tilr in relation to axis of ratation, c)  rotor speed and d) electir motor power. Combination of above factors makes it possible that the transferred air is equal to approx. 300 cubic meters per acre. This quantity of air modifies local climate around the orchard. Since the upper part of the air mixer rotates slowly around its vertical axis (360° every 4 min) the protected area should theoretically have an absolutely circular shape. 

Practocally, however, the area protected by the air mixer becomes egg-shapped, according to the prevailing drift blowing at night. Length of protected area depends on drift speed. Measurements have proved that the maximum length of coverage (parallel to the drift direction) is bigger than the width by 30-50% (see diagram). The produced air steam is more weak as the distance from the air mixer increases. Consequently, a change in direction, will change the limits of the area to be protected accordingly.

 

THERMAL CEILING - AIR MIXER OPERATION & EFFECTS

 

 antifrost 1.6

 

 antifrost 1.7  antifrost 1.8

 

 

 antifrost 1.9  antifrost 1.10  antifrost 1.11


 

TECHNICAL DESCRIPTON OF ELECTRIC AIR MIXER

The air mixer is a gian fan situtated atop a 10 m. steel tower. The electric motor stands on the tower top and transfers its torque to the blades through a geared reducer. Air mixer operation is supervised by an electronic unit inside the control box.

ROTOR BLADE

It is composed of the steel hub and two glassfiber reinforced polyester blades. Rotor construction allows regulation of each blade poston to obtain maximum possible air supply. Rotor axis or rotation has a tilt angle of 96° so as to transfer warm airi n the height of the trees. In models HAM 5-10 and HAM 10-20, this angle is adjustable up to 100° for maximum effect.


SPEED REDUCER

It's an angular geared speed reducer in the two bigger models and horizontal in the two smaller ones. Transmission ratio is 2,5:1, the gear has a buit-in device which turns the rotor assembly horizontally every 4 min. to achieve continuous coverage of the cultivation area.

 

ELECTRIC MOTOR

In big models, the motor is located in a vertical position and is connected to the gear through coupler. In small models the motor is horizontally placed and connected to the gear directly. Built-in thermistors in the three phases check the motor temperature.

 

TOWER

The tower is a tubular steel construction 10 m. high, founded on a steel reinforced concrete base through four anchor bolts. On special order a 3-legged lattice tower may be provided.

 

CONTROL PANEL

It is a specially designed unit to control the operation of the air mixer and also protect the motor under any conditions. Except of the star-delta motor starter, the unit also includes the following elements:

-General input switch and mans crcut breakers.

-Operation hours meter.

-Volt-meter, Amp-meter.

-Automatic and manual selection swtch.

-Electronic unit controlling the following parameters:

  • Mains malfunction (interrupts air mixer operation and restarts it automatically).

  • Tower vibrations (if excessive vibration occurs, operation is interrupted).

  • Operating temperature range (regulated thermostat switch).

  • Wind speed (operaton is interrupted above 2 beauforts).

For each of the above functions, there is a visual indication on the front νiew of the control panel.

FURTHER TECHNOLOGY DEVELOPEMENT

Once we noticed that our technology is greatly effective on the prevention of frost ,a highly aggressive meteorological phenomenon, thoughts led to further developement and usage of this technology for preventing fog on highways and airport, leading to the creation of ANTI-FOG TECHNOLOGY.