In the refrigerator - 0 ° C. Drawing, description

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In the refrigerator - 0 ° C. Tips for the home master

Builder, home master

The magazine "Modeler-Constructor" has repeatedly published materials about home-made "refrigerators", where natural cold is used to store food, which is more than enough in the middle zone of our country, not to mention its north. In all these devices, in case of too severe frosts, the optimum temperature is maintained by heating the food container. The sensors used for this are very different, but for some reason it never occurs to anyone to use the effect of phase transformation. In short - a physical phenomenon that accompanies the freezing and melting of water.

As you know, when freezing, water increases its volume, and this can be used to drive a variety of mechanisms. I want to bring to the attention of readers several devices where this effect successfully works.

Electrical heating switch. It can be used in foam-insulated boxes, which are sometimes installed on a balcony or outside a window. A heater is placed at the bottom of such a "refrigerator" - for example, a medical heating pad. On top of it is the second bottom - an aluminum pallet, on which perishable products are located. The temperature sensor is also placed here. It is a sealed container made of an elastic material (for example, polyethylene) filled with water. It is desirable that this vessel has the shape of a parallelepiped - sometimes shampoos or lotions are packaged in such containers.

The bottle is located in a rigid frame, on the wall of which normally open contacts or, better, a limit microswitch are mounted. When the water in the bottle freezes, its thickness will increase and the wall of the vessel will squeeze the contacts that turn on the heating of the pan. The course of the side wall can reach 10 mm with a bottle cross section of about 30x70 mm. After turning on the heating, the ice melts, the vessel takes its previous shape and the heating pad is turned off.

In the refrigerator - 0°С
Rice. 1. Balcony "refrigerator" with temperature control: 1 - a sealed vessel made of polyethylene filled with water, 2 - electrical contact (microswitch), 3 - electric heater (medical heating pad), 4 - bottom (plate with holes), 5 - stored product, 6 - styrofoam or wood box

Without electricity costs. If the products are stored in the cold zone of the window sill, which is formed when a heat-insulating barrier is installed on its edge (in the simplest case, an ordinary board or, better, a foam plate), then such a simple storage can also be equipped with a device that maintains the temperature in the cold zone at 0 ° C. The main role here is also played by a polyethylene bottle filled with water: when water freezes in it, it increases in volume, the force is then transferred through the rod and lever to the heat-insulating barrier, and the latter rises. A gap is formed under the barrier through which cold air flows, giving way to warm air flowing from above from the room. With a ratio of lever arms of 1:5 and with a working stroke of the sensor bottle wall of 10 mm, the width of the resulting gap can reach 50 mm. For greater effect, you can associate the rise and fall of the barrier with the closing and opening of the window.

In the refrigerator - 0°С
Rice. 2. Thermostat for the "cold zone": 1 - a sealed polyethylene vessel filled with water, 2 - a stem with a thickening at the lower end, 3 - a lever, 4 - a heat-insulating foam plate, 5 - a stored product, 6 - an air flow through a slot under the plate

Sensor with hydroconverter. The working stroke of the actuator can be made sufficiently large even without a system of levers, if a kind of hydraulic converter is used as a sensor. It is a rigid metal vessel, inside of which there is an elastic rubber tube; one end is plugged, and the other is connected to a hydraulic cylinder in which the plunger can move. The cavity of the metal vessel is filled with water, and the rubber tube, together with the hydraulic cylinder, is filled with engine oil.

When freezing in a vessel of water, ice squeezes the rubber tube, thereby squeezing oil into the hydraulic cylinder, which raises the plunger. The latter moves dampers or flaps that regulate the flow of cold air. The working stroke of the plunger depends on the volume of the metal vessel and the diameter of the plunger: the larger the first and the smaller the second, the more the plunger extends when the water freezes.

In the refrigerator - 0°С
Rice. 3. A sensor with a hydraulic transducer: 1 - a strong vessel made of metal, 2 - a threaded cover, 3 - a through channel along the axis of the cover, 4 - a piece of a rubber tube filled with oil, 5 - a plug covering the lower end of the tube, 6 - oil with a low freezing point, 7 - tide in the outer part of the cover (hydraulic cylinder), 8 - plunger, 9 - rubber ring for sealing; A - displacement of the plunger when water freezes in the vessel

Practice shows that to actuate the doors of the simplest "refrigerator" on the windowsill, which was discussed above, a cylinder with a volume of only 100 ml is sufficient.

A sensor with a hydraulic converter is also interesting in that it allows you to remotely control various devices (for example, close the doors of greenhouses or greenhouses when the temperature drops below zero degrees). To do this, the cylinder with an elastic tube placed in it is connected to the executive hydraulic cylinder with a long copper or aluminum tube.

Author: N. Bezborodov

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