Classification of refrigerators. direct reverse. Refrigerators. Types and applications of Reflux condensers

A direct condenser (Fig. 26 b) is used to distill solvents from a reaction medium, to separate mixtures of liquids into components, or to purify liquids by distillation.

A reflux condenser (Fig. 26a) is used in synthesis plants to dissolve substances. The vapors entering the reflux condenser are cooled, condensed, and the resulting liquid flows back into the reaction flask.

Figure 26. – Application of direct and reverse refrigerator.

Water (Fig. 27) Air (Fig. 28)

Refrigerators are classified according to the type of cooling agent that fills the inner “jacket”:

Water s running water;

Water with still water;

Air.

An air cooler is used to condense liquid vapors from
T. kip. >150 C, water with running water – boiling point. liquids< 120 С, водяной с непроточной водой - с Т. кип. жидкости от 120 до 150 С.

According to the structure of the inner tube

Based on the design of the inner tube, the cooling jacket, and, consequently, the cooling surface, refrigerators are distinguished:

- “pipe in pipe”;

Ball;

Serpentine;

Combined, etc. (Fig. 29).

The use of a specific type of refrigerator is determined by required intensity cooling.

A	b	V	G	d	e	and	h
And	To	l	m	n	O	P

Figure 29. Refrigerators of various designs.

Air cooler (Fig. 29 a, o)

It is one of the simplest refrigerators in design and consists of a long glass tube. Such a refrigerator is used only when working with high-boiling liquids (boiling point >150°C), since the cooling effect of air is small. The refrigerator can be used as direct or reverse. As a reverse refrigerator, such a refrigerator is ineffective: the movement of the liquid predominantly corresponds to laminar flow and the substance is easily “thrown out”. As a downward condenser, such a refrigerator can be used at a low distillation speed.

Weigel-Liebig refrigerator (more often Liebig, English. Liebig condenser)
(Fig. 29 b, p)

It was first proposed in 1771 by Weigel and then used
Liebig. Mainly used as a downdraft cooler. It is ineffective as a reflux condenser, because... has a small cooling surface and laminar flow vapor For this purpose, it is used for relatively high-boiling (boiling temperature > 100 0 C) compounds. Since atmospheric moisture condenses on the outer surface of the refrigerator, which can get inside the flask through capillary leaks in the joint, the joints on the refrigerator and flask should be thoroughly lubricated. It is also recommended to put a cuff made of dry filter paper on the refrigerator above the joint. Higher boiling liquids (boiling temperature >160 0 C) at the junction of the tubes (Fig. 30) can cause the occurrence of internal tension, which causes cracks or complete destruction of the glass.

Figure 30. Locations of possible cracks due to sudden temperature changes

The heat transfer coefficient for Liebig refrigerators with a length of 300 to 1000 mm varies from 105 to 35 W/(m 2 K), i.e. decreases with increasing length of the refrigerator.

A Liebig refrigerator can also perform the functions of an air refrigerator if it is positioned vertically and the steam of a high-boiling liquid is directed into the jacket through the upper branch, and condensate is taken from the lower one. As a result of heating, a continuous vertical flow of cold air will appear in the central tube. In this case, the most efficient refrigerators are those with a wider central tube and, if possible, a smaller diameter surrounding jacket.

Refrigerator Vesta(English West condenser) (Fig. 29 c)

It is a modification of the Liebig refrigerator, the difference from which is the smaller distance between the inner and outer tubes, which allows you to increase the speed of movement of the coolant. The Vesta refrigerator has double higher coefficient heat exchange than the Liebig refrigerator and is more effective for cooling the vapors of low-boiling liquids.

Allina ball cooler (English Allihn condenser) (Fig. 29 d)

Is a typical reflux condenser. Due to their larger cooling surface, Allina refrigerators are shorter than Weigel-Liebig refrigerators. It is convenient to insert the stirrer axis through the ball cooler and introduce it into the reactor various substances, well washed into the flask with condensate and heated by it. Typically, the number of balls in such refrigerators ranges from 3 to 8. In terms of efficiency as a reflux refrigerator, the Allina refrigerator is inferior to the Dimroth refrigerator (Fig. 29g, h ), withstands significant temperature changes. To avoid choking, when the condensate does not have time to flow back into the flask with boiling liquid, the reflux ball cooler is installed in an inclined position, but the slope should not be too great so that the condensate does not accumulate in the balls. The accumulation of condensation leads to a decrease in the effective cooling surface of the refrigerator.

Coil refrigerator(Graham's refrigerator)

(English: Graham condenser) (Fig. 29 d, f)

Never used as a reverse, because Condensation that does not flow well enough along the folds of the coil may be thrown out of the refrigerator and cause an accident. A vertically mounted coil refrigerator is the most efficient downdraft refrigerator, especially for low-boiling substances.

Dimroth refrigerator (eng. Dimroth condenser), (Fig. 29 g, h)

Very efficient reflux condenser. It has the highest heat transfer coefficient, reaching 120 W/(m 2 K). It can also be used as a downdraft if the relatively large distillate losses on the coil can be neglected. The junction of the coil with the jacket is located outside the zone with a large temperature difference, so when using such a refrigerator when working with liquids boiling above 160 0 C, there is no fear of complications. For more efficient cooling it is used Dimroth refrigerator with double jacket (Fig. 29 h).

To improve the performance of jacketed refrigerators, increasing heat transfer, a turbulent flow of coolant is created. To do this, the liquid supply and discharge tubes of the jacket are soldered so that their axes are located tangentially to the jacket (Fig. 14 i) . Then the water or other coolant will begin to move in a spiral in the refrigerator.

Friedrich's refrigerator (Friedrichs, Friederichs)
Friedrich condenser, (Fig. 29 i, j)

In such a refrigerator, vapors wash a coil tube with running water and the walls of an internal wide cylindrical tube, outside of which flows water coming from the coil. This steam intensive refrigerator is essentially a combination of the Liebig and Dimroth refrigerators. It is very effective for fractional distillation of liquid mixtures, since condensate practically does not linger in it.

Schirm-Hopkins refrigerator (usually the Hopkins refrigerator, Fig. 29 l).

It consists of a jacket through which steam is passed, and a “finger” located inside the jacket - a device through which liquid refrigerant flows. Using of this type refrigerator, the steam flow rate should be as low as possible.

Cooling finger Cold fingers, (Fig. 29 m)

This specially shaped reflux condenser (it does not need to be specifically fixed in the cooling system) is used primarily in devices for semi-micromethods. If the "cooling finger" is inserted into the reaction vessel on a stopper, the device does not need to be sealed.

Dewar refrigerator (Fig. 29 n)

A mixture of dry ice (solid carbon dioxide) with acetone or alcohol, or liquid nitrogen is used as a cooling agent in such a refrigerator.

Justus Liebig (1803-1873)	James Dewar (1842-1923)

Refrigerators- serve for condensation of boiling liquid vapors in distillation apparatuses. Depending on the operating conditions, the liquid is processed in the refrigerator while cooling the vapors (condensate) and must either be discharged to the receiver or returned to the vessel in which the heating is carried out. This difference in the purpose of refrigerators determines their shape and name. Refrigerators designed to collect condensate are called direct or downward, and refrigerators from which condensate is returned to the process are called reverse.

Direct refrigerators (Liebig). Liebig refrigerators, consisting of a long glass tube (forshtos), one end of which is expanded, are very common in laboratories. This tube is passed through a glass or metal jacket or coupling, and secured with pieces of rubber tubing fitted to the ends of the coupling. Sometimes there are Liebig refrigerators in which the refrigeration tube is soldered to the jacket.

At the ends of the coupling (perpendicular to its axis) there is one outlet. Rubber tubes are put on them, one of which, located near the narrow end, is connected with a water tap, and the other is diverted into the waste pipe. When the tubes are connected in this way, the water in the refrigerator moves towards the vapors of the cooled liquid. When connecting the refrigerator, the following rules must be observed: water must always enter the refrigerator from the lower lower end and exit from the upper raised end. The cooling jacket (coupling) must always be filled with water. Otherwise, during prolonged distillation, the refrigeration tube becomes very hot and may burst at the border with the water level.

When used for a long time, a reddish-yellow coating of iron oxides that enter with water from the refrigerator often forms in the refrigerator jacket. water pipes. Plaque interferes with the visibility of the refrigeration tube and must be removed periodically. To do this, the refrigerator is disconnected from the water tap, all the water is released and 10-16% hydrochloric acid is poured into the refrigerator jacket, while clamps are put on the rubber tubes near the outlets. Carefully turning the refrigerator, dissolve the deposit of iron oxides in hydrochloric acid, then pour out the acid, connect the refrigerator again to the water supply and run the water for 5-6 minutes. It is possible to distill a liquid using a Liebig refrigerator only when the temperature of its vapor does not exceed 150°C.

Reflux condensers can be ball (Allina refrigerators), coil and other forms. In ball refrigerators, the tube consists of spherical extensions, while in coil refrigerators it is coiled in the form of a spiral. This shape of the tubes increases the cooling surface and at the same time more complete condensation of vapor occurs.

The Allina refrigerator is installed only in vertical position, but not inclined, since in the latter case condensed liquid will collect in the balls, interfering with the correct selection of fractions.

Ball Soxhlet refrigerator most often used as the reverse. Cooling water enters through a small outlet into the internal spherical cavity and flows out of the right process. Liquid vapors pass between inner surface and the outer wall. Thus, the vapors are cooled from both surfaces at once; with the outside - air, and with the inside - cold water.

There are a number of special refrigerators, for example, refrigerators in which the refrigeration tube has the shape of a spiral (Fig. 14, position 6). This is done in order to increase the cooling surface without increasing the size of the refrigerator.

Refrigerators Domrata are universal, as they can be used as downstream and reverse. The refrigerator can withstand significant temperature changes. Its advantage is that on its outer walls there are water vapors from environment do not condense.

Related information:

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Vapors of liquids during distillation or heating (boiling). Used to distill solvents from a reaction medium, to separate mixtures of liquids into components (Fractional distillation), or to purify liquids by distillation.

Depending on the method of application there are different following types refrigerators:

• Direct refrigerator (descending) - used to condense vapors and remove the resulting condensate from the reaction system. The condensate is collected in a receiver flask.
• Reflux refrigerator - used for condensing vapors and returning the condensate to the reaction mass. Such refrigerators are usually installed vertically.

Types of refrigerators

Reverse, or rising, condensers are used when carrying out a reaction at the boiling point of the reaction mixture, but without distilling off the liquid; they ensure condensation of vapors and flow of condensate back into the reactor along the walls of the refrigerator.

Dephlegmator - a refrigerator for partial condensation of the light part of steam, reflux.

The simplest type of laboratory refrigerator is the air refrigerator, which is usually just a glass tube that is cooled by ambient air. It is used exclusively when working with high-boiling liquids (preferably with a boiling point of at least 300 °C), which when working with a water cooler due to big difference temperatures could cause a crack in the glass of the refrigerator.

Air cooler

It is one of the simplest refrigerators in design and consists of a long glass tube. Such a refrigerator is used only when working with high-boiling liquids (boiling point >150°C), since the cooling effect of air is small. The refrigerator can be used as direct or reverse. As a reverse refrigerator, this type of refrigerator is ineffective: the movement of the liquid predominantly corresponds to laminar flow and the substance is easily “thrown out”. As a downward condenser, such a refrigerator can be used at a not too high distillation speed for substances with a boiling point >150°C.

Ball air cooler

Used as a reverse. Ball coolers are more efficient than conventional ones (straight in design) air coolers, due to the larger heat exchange surface. Such refrigerators have found application for semi-microsynthesis, where the amount of heat removed is small and for condensation of even low-boiling substances air cooling turns out to be quite sufficient. (If necessary, the refrigerator can be wrapped in damp filter paper in this case.)

Liebig refrigerator

It is used primarily as a downdraft down to approximately 160°C. Coolant for substances with boiling point< 120°С служит в нем проточная вода, а в интервале 120-160°С - непроточная.

The Liebig refrigerator consists of two glass tubes sealed one into the other. Liquid vapor moves through the inner tube, and cooling agent (cold water) moves through the outer tube (jacket).

As a reverse refrigerator, such a refrigerator is ineffective, since it has a small cooling surface and laminar flow of vapors; for this purpose, it is used only for relatively high-boiling (bp >100°C) compounds. Atmospheric moisture condenses on the outer surface of the refrigerator, which can get inside the flask through capillary leaks in the joint, so the joints on the refrigerator and flask should be thoroughly lubricated. It is also recommended to put a cuff made of dry filter paper on the refrigerator above the joint. Higher boiling liquids at junction A (Fig. 1-c) can cause internal stress, which causes cracking of the glass. Therefore, Liebig refrigerators cannot be made of non-heat-resistant glass.

Ball cooler

Used exclusively as a reverse. Since this refrigerator has spherical expansions, the flow of vapors in it becomes turbulent; The cooling effect of such a refrigerator is significantly higher than that of the Liebig refrigerator. However, atmospheric moisture also condenses on its outer surface and junction A is also dangerous. The coolant is supplied from bottom to top. It is convenient to insert the stirrer axis through the ball cooler and introduce various substances into the reactor, which are well washed into the flask by the condensate and heated by it. Typically, the number of balls in such refrigerators ranges from 3 to 8. To avoid choking, when the condensate does not have time to flow back into the flask with boiling liquid, the reflux ball refrigerator is installed in an inclined position, but the slope should not be too large so that condensate does not accumulate in the balls . The accumulation of condensation leads to a decrease in the effective cooling surface of the refrigerator.

Coil refrigerator

Never use as a return, since condensate, which does not flow well enough along the folds of the coil, can be thrown out of the refrigerator and cause an accident. A vertically mounted coil refrigerator is the most efficient downdraft refrigerator, especially for low-boiling substances.

Staedeler refrigerator

A modification of the coil refrigerator in which the cooling vessel can be filled with a mixture of ice and table salt, solid carbon dioxide with acetone, etc. Such a refrigerator can be used for condensation of substances boiling at very low temperatures.

Dimroth refrigerator

Very efficient reflux condenser. It is also used as a downdraft if the relatively large losses of distillate on the coil can be neglected. The junction of the coil with jacket A is located outside the zone with a large temperature difference, therefore, when using such a refrigerator when working with liquids boiling above 160°C, there is no fear of complications. Since the outer jacket of the refrigerator is air when room temperature, atmospheric moisture does not condense on its surface (see above). True, low-boiling substances can “crawl” along inside shirts and thereby “pull” the cooling zone. The Dimroth condenser is therefore not suitable as a return condenser for relatively low-boiling substances, such as ether. At the upper open end of the refrigerator, atmospheric moisture easily condenses on the water supply hoses, so it is equipped with a calcium chloride tube.

Immersion refrigerator - “cooling finger”

This specially shaped reflux condenser (it does not need to be specifically fixed in the cooling system) is used primarily in devices for semi-micro methods. If the “cooling finger” is inserted into the reaction vessel on a stopper, the device should not be sealed.

Installation

Chemical refrigerators can be used either as reverse or as downward (they differ in the position and method of fastening when installing the device).

The top of the condenser is attached to a Wurtz flask, Wurtz tube, or tube extending from the flask containing the original mixture. Bottom part connected to an allonge, through which the product of synthesis or distillation enters the receiver.

It should be separately noted that the cooling agent (water) is supplied exclusively from the bottom up. When refrigerant is supplied from top to bottom, filling the refrigerator jacket will be incomplete, which will make cooling ineffective. In addition, with such a supply, the refrigerator may fail (crack) due to local overheating of the jacket.

• Voskresensky, P. I. Technique laboratory work: manual / P. I. Voskresensky. - 10th ed., erased. M.: Chemistry, 1973. 717 pp.

The XSh ball refrigerator is designed for heat exchange of two flows, cooling and condensation of liquid vapor. It is used exclusively as a return one, as it has spherical extensions inside the outer flask. When condensation occurs, the vapors in the refrigerator become turbulent. This type of refrigerator has higher cooling properties, significantly exceeding those of Liebig type refrigerators.

Features of use

The coolant is supplied from bottom to top. The ball device allows you to insert the stirrer axis into it, as well as introduce various substances into the reactor. Typically the number of balls ranges from 2 to 8.

When in use, the ball cooler is installed in an inclined position. This allows you to avoid drowning, while the slope should not be significant, otherwise the condensate will not have time to drain back into the flask. Condensation accumulation affects cooling efficiency.

In our online store you can buy, the following types ball refrigerators:

• length from 20 to 40 cm;
• number of balls - 2, 6, 8;
• input/output connection - 14/23, 29/32, 45/40 and without grinding.

Advantages of a ball cooler

1. The special ball design gives the refrigerator an impressive heat transfer surface.
2. Low vapor resistance allows you to get more high-strength moonshine.

You can buy a reflux refrigerator on this page.

You took beer with you on your hike, but there wasn’t a stream with cold water along the route, and the cold ended. How to quickly cool beer or other drinks, and not by a couple of degrees, as is done through evaporation, but in such a way as to actually cool the drink and enjoy the heat? To do this, you need to take with you an extremely compact chemical refrigerator, which you can prepare in advance and always have the necessary charge on hand for cooling food, freezing bruises and other needs.

Cold will help with: bruises, sprains, fractures, dislocations, swelling, burns, insect bites, heat stroke, the occurrence of inflammatory processes, the need to stop bleeding (from the nose), the need to cool foods.

Method for producing chemical cold

To prepare it you need water and ammonium nitrate- a common fertilizer. You can easily find it in flower shop, its price is low, so your emergency refrigerator will be cost-effective.

The mass proportion of water and nitrate is 60% to 40%, by volume it turns out to be 1:1. Stir this mixture in the bottle. When dissolved in water, saltpeter absorbs a large number of heat. If salt, when dissolved, lowers the temperature by 3 degrees, then the same amount of saltpeter will lower the temperature by 23 degrees! Fridge chemically ready to use. If you freeze a half-filled bottle with water and then fill it with saltpeter (grinding is not necessary), you will get a long-lasting source of cold.

Another one great idea. While camping, you can make a cooler out of a camping mat and a bottle of formula. IN right moment We activate the mixture and wrap it in a mat, and cover the open ends with a rag or spare clothes.

The used mixture, before pouring it out, must be greatly diluted with water if you do not want to harm the plants.

About a thermos, how to make one from a bottle.

Experiment with chemically generated cold

Mix 100 g of snow or ice with 33 g of rock salt - the temperature of the resulting mixture will drop to -20 ° C. If you mix 100 g of snow or ice with 100 g of potassium nitrate, the temperature of the mixture will drop to -30 ° C. The temperature of the cooling mixture, consisting of 100 g of snow (or ice) and 150 g of potassium chloride hydrate reaches -45° C. But what about in the summer, when there is no snow and ice? In the warm season, you can use these chemical compounds, which, dissolving in water, absorb heat, thereby helping to reduce the water temperature to – 35 ° C. Of course, the water must be cold, and the compounds indicated below must be taken in the following proportion(by weight) relative to water:

ammonium chloride 3
sodium nitrate 5
ammonium nitrate 10
sodium sulfide + hydrochloric acid 40
ammonium or potassium thiocyanate 15

To avoid large losses of cold, it is advisable to prepare the solution in a thermos.

When finished, pour the solution into a cup and remove the water from it by evaporation. The substance remaining after evaporation can be used again for experiments.