Reverse refrigerator. Refrigerators

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What is the difference between a direct distillation refrigerator and a reverse one? and got the best answer

Answer from Ariel[newbie]
Fundamentally, they differ little from one another. If we're talking about As for the laboratory version, the direct refrigerator, as a rule, is a straight tube with a water “jacket”. vapors enter it from above, condense, and the condensate flows into the receiver from the lower end. can be installed obliquely or vertically. This device was invented in the 19th century by the German chemist Johann Justus von Liebig, which is why it is also called the “Liebig refrigerator.” designed for simple distillation of liquids, as well as separation of their mixtures; in the latter case, a reflux condenser is often additionally used.
A reflux condenser is designed to condense the vapors of a boiling liquid and return it to the vessel in which it is boiling. in this case, the vapor enters the lower part of the refrigerator, and condensate flows through it. the device is similar to the Liebig refrigerator, but to increase the efficiency of the device, the internal straight tube is replaced with a complex-shaped tube with a larger surface area ("ball" refrigerator), in addition, in addition to the water "jacket" or instead of it, an internal coil can be installed. the upper end of the reflux condenser must be in communication with the atmosphere.
in principle, almost any direct refrigerator can be used as a reverse refrigerator, provided that its efficiency and inner diameter sufficient for condensation required quantity vapor In principle, a reflux condenser can also be used as a direct condenser if necessary, but it must be taken into account that liquid can be retained in the unevenness of the internal surface, which can lead to a decrease in separation efficiency. It is better not to use a reflux condenser as a direct condenser during vacuum distillation.
Nowadays, almost all refrigerators, both direct and reverse, are equipped with grinding joints at both ends, so there are usually no difficulties when installing them.

Answer from Alexander Goponenko[guru]
At the reflux condenser, the concentrated vapors return back to the reactor. Used when carrying out reactions at high temperatures. Alternatively, the reaction could be carried out in a sealed vessel, but then the pressure may become high (even to the point of explosion).
A direct condenser is used for distillation - separating the low-boiling component from the high-boiling one.
Design differences reflect the purpose. The reflux condenser usually stands vertically, and the liquid should flow back down. A straight refrigerator is usually placed at an angle; condensed liquid should flow out from the other side and not accumulate in the refrigerator

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 the required cooling intensity.


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 vapor flow. 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 point >160 0 C) at the junction of the tubes (Fig. 30) can cause internal stress, which causes cracks or complete destruction of the glass.

Figure 30. Locations of possible cracks when sudden change temperatures

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.

The Liebig refrigerator can perform the functions and air cooler, 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, smaller diameter the shirt surrounding her.

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 increasing the speed of movement of the coolant. The Vesta refrigerator has twice the heat transfer coefficient of 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 outside the area with big difference temperatures, so when using such a refrigerator when working with liquids boiling above 160 0 C, you do not have to worry about 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. When using this type of 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)

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 of 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

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

You can buy a reflux refrigerator on this page.

Chemical refrigerators

Distillation unit with Liebig downward condenser (5)

Refrigerator (chemistry)- a laboratory device for condensing 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.

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.

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 120 °C), which when working with a water cooler due to big difference temperatures could cause a crack in the glass of the refrigerator.

Application

When working with liquids with a boiling point below 120 °C, water coolers of various shapes are used - Liebig, ball, coil, etc. For distillation with an inclined downward condenser, the Liebig refrigerator is most convenient (except in the case of distillation of liquids with a very low boiling point, such as diethyl ether). Finger-shaped refrigerators are usually used as reverse refrigerators or for condensing vapors during sublimation

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

- [This article outlines: objectives of coking, selection of material, design of coking ovens, collection of by-products, physical and Chemical properties coke and statistical remarks.] non-volatile carbonaceous residue obtained from stone ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

I Poisoning (acute) Poisoning is a disease that develops as a result of exogenous exposure to the human or animal body of chemical compounds in quantities that cause disturbances in physiological functions and create a danger to life. IN … Medical encyclopedia

55 Xenon ← Cesium → Barium ... Wikipedia

A refrigerator is a device for condensing steam using a cooling medium, most often water. Refrigerators are installed either obliquely, when it is necessary to collect condensate in the receiver, or vertically to return the condensate to a flask with boiling liquid. In this case, the refrigerator is called reverse. If the temperature at which condensate solidifies is higher than the temperature of the cooling water, then water heated in a thermostat is supplied to the refrigerator, which prevents condensation from freezing in the inner tube of the refrigerator. In Fig. 58 presents the most commonly used refrigerators.

The Weigel-Liebig direct-flow refrigerator (Fig. 58, a) was proposed in 1771 by Weigel and then used by Liebig. This refrigerator is usually used for the distillation of liquids with a boiling point of 100 to 150 °C. The refrigerator has a cooling jacket that is relatively large diameter. The heat transfer coefficient for Weigel-Liebig refrigerators with a length of 300 to 1000 mm varies from 105 to 35 W/(m2*K), i.e. decreases with increasing length of the refrigerator.

Rice. 58. Glass refrigerators: Weigel - Liebig (a), Allin (b), VestanYa, Graham (d), Dimroth (d), Friederichs (f) and tangential water input into the cold-dilator (g) I]

Therefore, it is advisable to use two smaller refrigerators instead of one long refrigerator. The Weigel-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 a possibly smaller diameter surrounding jacket.

Liebig Justus (1803-1873) - German organic chemist and analyst.

The Allina ball refrigerator (Fig. 58, b) is a typical reflux refrigerator. 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 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. In terms of efficiency as a reflux refrigerator, the Allina refrigerator is inferior to the Dimroth refrigerator (Fig. 58, d), which can withstand 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. (Allen (Allen) Alfred Henry (1847-1904) - German organic chemist and analyst.)

The Vesta refrigerator (Fig. 58, c) has a cooling jacket of small diameter, located close to the central, somewhat curved tube. It is more efficient than the Weigel-Liebig refrigerator. Under the same conditions of liquid distillation, a Vesta refrigerator has twice the heat transfer coefficient than a direct-flow one. The Graham spiral refrigerator has the same efficiency (Fig. 58, e). It is used to condense vapor of highly volatile liquids. Both refrigerators retain some of the condensate in the inner tube and are therefore not very suitable for fractional distillation.

The Dimroth refrigerator (Fig. 58, d) is recommended as a reflux refrigerator. It has the highest heat transfer coefficient, reaching 120 W/(m2K). It is not used for fractional distillation of liquid mixtures due to its large gas volume and the ability to retain a lot of condensate in an inclined position.

Graham Thomas (1805-1869) - English physical chemist. Studied the diffusion of gases and liquids through membranes.

West Robert (b. 1928) - American organic chemist.

Dimroth Otto (1872-1940) - German organic chemist.

Friederichs refrigerator (Fig. 58, f). In this refrigerator, steam washes over a coil tube with running water and the walls of an inner wide cylindrical tube, outside of which flows water coming from the coil. This steam intensive refrigerator is essentially a combination of the Weigel-Liebig and Dimroth refrigerators. It is very effective for fractional distillation of liquid mixtures, since condensate practically does not linger in it.

To improve the performance of jacketed refrigerators, by enhancing heat transfer, a turbulent flow of cooling liquid is created.

Rice. 59. Chamber refrigerators: cartridge type (a, b), Staedeler (c), Shirm-Hopkins (d) and Soxhlet (d)

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. 58, g). Then the water or other coolant will begin to move in a spiral in the refrigerator.

Cartridge-type refrigerators (Fig. 59, a, b). In them, the central part - the cartridge - is filled with a solid or liquid cooling mixture. Such refrigerators for low-boiling liquids are reverse. These include the Staedeler refrigerator (Fig. 59, c), in which steam condensation occurs in a coil cooled by liquid and solid mixtures. The liquid formed when the solid refrigerant melts is drained through the side pipe. The liquid component of the solid-liquid cooling mixture is supplied through the left tube, which reaches the bottom of the refrigerator bowl.

Städeler Georg Andreas (1841-1871) - German organic chemist.

The Schirm-Hopkins finger refrigerator (Fig. 59, d) consists of a jacket through which steam is passed, and a “finger” located inside the jacket - a device through which liquid refrigerant flows. When using a finger cooler, the steam flow rate should be as low as possible.

The spherical Soxhlet refrigerator (Fig. 59, e) is more often used as a reflux refrigerator. The steam passes between the outer wall, cooled by air, and the outer wall of the inner ball, through which the refrigerant circulates. The Soxhlet refrigerator is also used in the distillation of liquids. high temperature boiling.

Soxhlet Friedrich (1848-1926) - German agricultural chemist.

Sections

Reverse refrigerator. Refrigerators

Types of refrigerators

Application

Installation

see also

See what “Chemical refrigerators” are in other dictionaries: