THE REFRIGERATOR IS 0°C! | MODEL CONSTRUCTION

In the journal “modelist-Konstruktor” has repeatedly published materials on the makeshift “fridges” where to store your products use natural cold which in the middle zone of our country, not to mention its North, more than enough. In all of these devices when too much frost, the optimum temperature is maintained by heating the food. The sensors used for this are very different, but for some reason, nobody comes to use the effect of phase transformation. In short, a physical phenomenon accompanying the freezing and melting of water.

As you know, when water freezes it increases its volume, and it can be used to drive various mechanisms. I want to offer readers several devices which successfully works this effect.

The switch electrically. It can be used in insulated foam boxes, which often set on the balcony or outside the window. At the bottom of this “fridge” fits the heater — for example, medical heat pad. On top of it is second bottom, aluminum tray, which are perishable products. Here is placed and a temperature sensor. It is a hermetic container of flexible material (e.g., polyethylene) filled with water. It is desirable that this vessel had the shape of a parallelepiped in such sometimes Packed shampoos, or lotions.

The bottle is a rigid frame, on the wall of which are mounted normally open contacts or, better, limit microswitch. When the water in the bottle freeze, its thickness will increase and the wall of the vessel will compress the contacts including heated pan. Move the side walls can reach 10 mm when the cross-section of the bottle is about 30X70 mm. After turning on the heated the ice melts, the vessel takes the same form and the heater is turned off.

Fig. 1. Balcony “refrigerator” temperature control:

1 — sealed polyethylene vessel filled with water, 2 — contact (micro switch), 3 — heater (heater medical), 4 — bottom plate (plate with holes), 5 — persistent product, 6 — a box of foam or wood.

Without the cost of electricity. If the products are stored in a cold area of the sill which is formed when mounted on the edge of the heat insulating barrier (in the simplest case, an ordinary Board or better — foam plates), it is the simplest vault, also can be equipped with a device to maintain temperature in the cold zone at 0°C. the Main role here also plays water-filled plastic bottle in the freezing water in it it increases in volume, the force is transmitted further through a rod and lever to teploizoliruyuschih the barrier, and the latter is raised. The barrier is formed a gap, through which flows the cold air, giving the place a warm, flowing from the top of the room. When the ratio of lever arm 1:5 and in the course of working the wall of the bottle-sensor 10 mm width of the formed slit may reach 50 mm. For greater effect, you can associate the raising and lowering of the barrier closing and priotkryvaya window.

Fig. 2. The thermostat to the “cold zone”:

1 — sealed container made of polyethylene, filled with water, 2 — rod with a thickening at the lower end, 3 — lever, 4 — insulating plate of plastic foam, 5 — persistent product, 6 — the air flow through the crack under the plate.

Sensor with hydraulic transducers. Working stroke of the actuator can be made large enough without leverage, if the sensor is to use a kind of hydraulic Converter. It is a tight metal vessel, within which is located an elastic rubber tube; one end plugged and the other connected to a hydraulic cylinder in which can move the plunger. The cavity of the metallic vessel filled with water and a rubber tube coupled with a hydraulic cylinder — engine oil.

In the freezing vessel of water ice compresses the rubber tube, thereby squeezing the oil hydraulic cylinder, lifting the piston. The latter moves the damper or shutter for regulating the flow of cold air. Working stroke of the plunger depends on the volume of the metal vessel and the diameter of the plunger: the more .the first and less than second — the greater advances a plunger in the freezing water.

Fig. 3. Sensor with hydraulic transducers:

1 — strong vessel of metal, 2 — cover screw 3 — through channel along the axis of the cap 4 — the length of rubber tubing filled with oil, 5 — tube, closing the lower end of the tube, 6 — an oil with a low freezing point, 7 — tide in the outer part of the lid (hydraulic cylinder), 8 — piston, 9 — rubber ring for sealing; And — the displacement of the plunger during the freezing of water in the vessel.

Practice shows that for actuating the valves of a simple “fridge” on the windowsill, which was discussed above, it is enough cylinder volume of only 100 ml.

Sensor with hydraulic transducers is also interesting because it allows you to remotely control various devices (e.g., close doors of greenhouses or greenhouses when the temperature is below zero degrees). To this end, the cylinder having arranged therein an elastic tube connects with the Executive hydraulic cylinder with a long copper or aluminum tube.

N. BEZBORODOV, Dolgoprudny, Moscow region.

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