Thermoelectric refrigerator for chromatograph

 

(57) Abstract:

The invention relates to a thermoelectric semiconductor refrigerators are designed to cool or Ter-motterone capillary chromatographic column for gas analysis using a chromatograph. Features thermoelectric refrigerator for chromatograph consisting of a thermopile cooling, coupled with her cooled matrix, radiator, fan, cases, covers, thermal insulation and sensor temperature. thermopile is made of individual modules along the capillary chromatographic column and parallel to the heat flow, cooled matrix consists of individual elements made of vysokoteploprovodnyh material, for example copper, and connected by a flexible conduits, such as flexible stranded copper wire, and the joints between the individual elements of the matrix is filled with an elastic sealant, such as sealers. The matrix has a narrow groove of rectangular shape, of a width corresponding to the diameter of the capillary, and a depth equal to not less than three diameters of the capillary. The lid has a groove of trapezoidal shape with an angle in the range of 20-30othe fridge with the dismantling of the capillary matrix of the refrigerator, and the fridge in the working chamber chromatograph, high reliability thermopile in a wide range of temperatures, the possibility of cooling the capillary tube of any length. 1 Il.

The invention relates to a thermoelectric semiconductor refrigerators designed for cooling or temperature control of the capillary chromatographic column for gas analysis using a chromatograph. The aim of the invention is the creation of a functional structure of a thermoelectric refrigerator with a wide range of operating temperatures.

While conducting gas analysis using a chromatograph for some tasks require full cooling a chromatographic column or part thereof. Herself column is placed in the working chamber chromatograph /1, S. 45-60/.

Typically, the cooling column is carried out using a system of liquid nitrogen or carbon dioxide, supplied separately from the chromatograph. With the cost of modern chromatographs ~30000 - 40000 $ , for example chromatograph company Perkin-Elmer models 8400, 8500, the cost of such cooling systems can be up to 40-50% of the cost of the chromatograph. The operation of the chromatograph with the above cooling system is quite Trudie graficheskiy column is usually 10-30 minutes After cooling column coolant from the camera must be quickly removed, because in the future operations of the gas analysis requires heating the column to a temperature of 100-200oC for 5-10 min, which is a built-in camera with heater and air fan.

For a number of tasks gas analysis when the chromatograph required cooling column or part thereof up to a level of temperature(30-40)oC. This can be achieved by using thermoelectric semiconductor refrigerator operating on the Peltier effect /2/. The first refrigerators (thermostats) for chromatography /3, S. 456/ were quite energy-intensive, unreliable and inconvenient to work, so did not find application in gas chromatographs.

At 3, S. 453/ presents thermoelectric device (refrigerator) for a gas analyzer, we adopted as a prototype.

thermostat consists of a thermopile cooling water radiator, a working chamber in which is placed the bottle Drexel, temperature sensor, thermal insulation cover. Thermoelectric battery creates the necessary temperature in the chamber at 0oC, which is condensed naphthalene from hot TA (refrigerator) are:

the complexity and duration time of the process gas analysis;

- large dimensions thermostat, excluding its placement in the working chamber of the chromatograph;

- large electric power consumption (150 W) at the large value of the operating current (50 A), reducing the possibility of temperature control chamber of thermostat in a wide range of temperatures;

low reliability of thermopile cooling mode "on / off" due to the large thermal stresses in the switching of cold shuts.

The present invention is the creation of a thermoelectric cooler for a gas chromatograph, working in a wide range of operating temperatures from -(30-40) to +60oC, convenient in installation and dismantling as in the working chamber of the chromatograph, and the chromatographic column, reliable.

It is proposed that thermopile is made of individual modules along the capillary chromatographic column and parallel to heat flow; the cooled matrix consists of individual elements made of vysokoteploprovodnyh material, for example of copper, connected by a flexible heat pipe, the sealant, for example, sealers; the matrix has a narrow groove of rectangular shape, of a width corresponding to the diameter of the capillary, and a depth equal to not less than three diameters of the capillary; the lid has a groove of trapezoidal shape with an angle in the range of 20-30o; refrigerator equipped with a quick-release frame with screw clamps.

The proposed design solution thermoelectric refrigerator for chromatograph allows you to:

to produce cooling (temperature control) capillary chromatographic column in the temperature range from -(30-40) to +60oC any length;

- quickly perform the Assembly and disassembly of the fridge in the working chamber of the chromatograph, and the installation of the capillary chromatographic column in the refrigerator;

to increase the reliability of the refrigerator;

- to install one temperature sensor and be confined to a single channel automatic temperature control, thermal modules thus connected electrically in series.

Guaranteed positive effect of increasing the reliability of the refrigerator and facilities collaboration refrigerator and chromatograph is due to the fact that thermopile cooling is made of individual modules, allele on heat flow. Thus, due to the reduced length of the individual elements of the cooled matrix, and paired with her metallized ceramic teploperedacha, reduced thermal stress in switching the cold junctions of thermopile and increases the reliability of its work. The connection of the individual elements of the cooled matrix between a flexible conduits, such as flexible stranded copper wire, allows you to equalize the temperature field of the composite matrix within 0,2-0,25oC. thus, the design of the refrigerator allows you to cool the capillary of any length. The joints between the individual elements of the matrix is filled with an elastic sealant, such as sealers, which helped to make the composite matrix is sealed and at the same time flexible, without increasing thermal stress on the cold junctions of thermopile. The presence in the matrix of the narrow rectangular groove width corresponding to the diameter of the capillary chromatographic column, and a depth equal to not less than three diameters of the capillary enables heat transfer between the matrix and the capillary with a minimum temperature gradient. The presence in the lid of the refrigerator groove trapezoidal shape with an angle in the range of 20-30oand the presence Bystroye the chromatograph, as well as the capillary in the refrigerator.

The drawing shows a General view of thermoelectric cooler to the chromatograph.

Here:

1 - thermopile, 2 - matrix, 3 - radiator, 4 - fan 5 - body 6-cover 7 - thermal insulation, 8 - sensor, 9 - heat, 10 - junction, an 11 - frame, 12 - screw 13 - nut 14 - hour, 15 - screw, 16 - groove, 17 cable, 18 - pad. The capillary (capillary tube) (not shown) is placed in a rectangular groove 16 matrix 2, is made of copper. Capillary tube (capillary) of the chromatographic column made of quartz coated with a special enamel that has a diameter of 0.3-0.5 mm capillary Length is several meters. The capillary tube is coiled in a spiral in the Bay. The capillary is a fragile item. The length of the cooled (cooled) section of the capillary can be 60-80 mm. the length of the capillary determines the length of the matrix. Matrix low-temperature solder, such as alloy rose TU-09-4965-88, fused with a metalized ceramic haloperidol thermopile cooling 1 ( the drawing shows a two-stage thermopile). Thermoelectric semiconductor battery cooling 1 operating on the Peltier effect, is traditional constructive solution is -3 1/K. the Specified figure of merit corresponds to the maximum temperature difference at the junctions of single-stage thermopile within 68-70oC at zero capacity. For two-stage thermopile this difference increases by 25-30%.

Thermopile 1 is made of two identical thermoelectric modules (see the drawing) along the cooled capillary. Electrically powered modules is carried out sequentially, and heat flow they work in parallel, cooling independently from each other the plot of the capillary.

Almost thermoelectric modules on electrical resistance may differ from each other by 8-10% /4/. Therefore, when continuous power at maximum capacity or maximum temperature difference on modules: T = TOCD.cf.-Tfull colorwhere TOCD.cf.and Tfull color- the ambient temperature and the cooled matrix, respectively, the temperature difference T for individual modules will be different from each other at 2-5oC. in order to substantially reduce the difference of the difference of thermoelectric modules, and accordingly, the temperature gradient in the cooling capillary, the Department is practical cooling modules, are connected by flexible conduits 9. The heat pipe 9 is made in the form of a flexible stranded copper wire type PS GOST 9124-74. Wire type PS should be relatively short and with a large cross-section. The wire 9 is soldered low-temperature solder alloy rose to the elements of the matrix 2 (see top view). When soldering wires 9, be aware that it may lose its flexibility due to solder along its length due to its high wicking (capillary) properties. Especially this effect is enhanced if the wire twisting (twisting wires required to reduce its diameter, and thus the dimensions of the cooled element).

The junction 10 between the individual elements of the matrix 2 is filled with an elastic sealant, such as sealers-18 THE 38 - 103233-74. This has enabled us to make a composite matrix sealed and at the same time flexible, without creating additional thermal stresses in switching the cold junctions of thermopile.

In the matrix 2, and therefore in the housing 5 (see view a) there is a rectangular groove 16 (the groove in the casing section may be somewhat larger than the groove in the matrix). The width of the groove in the matrix 2 corresponds to the diameter of the capillary chromatographic column. When the value of the diameter Kinopalace influence on the parameters of the refrigerator. On the one hand, the greater the depth of the groove, the greater the likelihood that the capillary will be in the isothermal cavity (due to the small width groove convective heat transfer of air in the channel (groove) is completely absent, and the cooled air will be placed at the base of the groove). On the other hand, with increasing depth of the groove increases the mass matrix, and therefore the output time of thermal mode of the refrigerator. When the depth of the groove equal to approximately three times the diameter of the capillary, i.e., ~1.5 mm, the temperature of the air in the groove (channel) is close to the temperature of the walls of the groove and the mass matrix is not too extended.

Thermopile 1 low temperature solder (alloy rose) soldered to the radiator 3. Needle radiator 3 is manufactured by casting of aluminum alloy and has a galvanic coating on the basis of copper-Nickel for subsequent soldering.

The discharge of heat from the hot junctions of thermopile 1 when it operates in the cooling mode by using the blowing needle-shaped radiator 3 integrated axial fan 4. Fan DC, for example, the brand of 0.7-EV-0,4 UK.883.121 THAT provides air flow within 40 m3/h at full pressure of 4 mm of water.article.

DL is Artie, equal to the diameter of the impeller 4.

On the housing 5 by a running landing is put on the cover 6. Cover 6 and the housing 5 have no locks fastening. In the cover 6 has two trapezoidal groove (see view a). The width of the groove in the upper part of 0.8-1 mm, the angle of the groove ~20-30o. The groove in the lid acts as a capture capillary and greatly facilitates its installation in the groove matrix 2 of thermoelectric refrigerator. The groove in the lid is fixed directs the capillary into the groove 16 matrix 2 dressing cover 6 in the housing 5. This groove facilitates the dismantling of the capillary. The groove in the lid reduces the likelihood of mechanical damage to the capillary during the mounting and dismantling works with refrigerator.

As mentioned above, the capillary is rolled in a spiral. Therefore, it can be expected that during installation of the capillary in a thermoelectric refrigerator it will rest on the top edge of the groove of the cover 6, and due to initial curvature and spring properties to touch the bottom of the groove matrix 2.

Thermal insulation 7 reduces heat leakage on the cold junctions of thermopile 1. As a material of thermal insulation 7 may be, for example, foam stamps PS-4-40 TU 6-05-1178-87, coefficient of thermal conductivity which is at predica temperature can be, for example, Microterminal ARTICLE 3-19, OJO. 468.031 THE par value of 2.2 kω. The sensor 8 may also serve in the system of automatic control and maintain the temperature of the matrix 2 refrigerators. By equalizing the temperature of the matrix with flexible heat pipes in the fridge is only one temperature sensor.

Power thermopile 1, the fan 4, and the transmission of an electrical signal from the sensor 8 are carried out on an electrical cable 17. Prior to that all the current terminals displayed on the guide block 18.

The housing 5 of the fridge for a running landing is accurately reported in box 11. Frame 11 is placed on the basis of the working chamber of the chromatograph. Frame 11 is rigidly fastened by means of two screws 12. The movement of the screws 12 by means of two fixed nuts 13, seamed into the rack 14 and have only rotational motion. The role of the key plays of the cylindrical protrusion of the screw 15, and the screw 12 throughout its length is provided a rectangular groove. Hour 14 welded to the frame 11. During the rotation of the nut 13 (for ease of rotation on the lateral faces of the nut provides for a large knurled) depending on the direction the screw 12 moves up and rests in the ceiling is the same body 5 of the refrigerator in the frame 11 will be 10-15 C. At the same time frame Assembly after disassembly of the refrigerator can remain in the working chamber chromatograph, without interfering with the closing of the chamber door.

In the chromatographs of the company Perkin-Elmer models 8400, 8500 base of the chamber with a lid (door) is pushed forward. For these chromatographs it is advisable to have only one frame 11, which is high-temperature adhesive (up to 200oC) is attached to the sliding base.

Thermoelectric refrigerator for chromatograph operates as follows.

The door opens to the working chamber of the chromatograph and installation of frame 11 in the chamber. Rotation of the nuts 13 and, accordingly, vertical movement of the screws 12, is made by the hand of the operator.

The window frame 11 is mounted to the housing 5 thermoelectric cooler Assembly.

Using trapezoidal grooves on the lid 6 is capture the desired capillary chromatographic column. The cover 6 is fitted to the housing 5. The operator must ensure that the capillary exactly in the groove of the matrix 2 thermopile cooling 1. For this purpose, the housing 5 can be coated slim risks.

Is power to thermopile 2 and the fan 4. Philadelphica with the system of automatic control and maintain the temperature sets the desired temperature of the matrix 2 and the inclusion of the automatic unit.

Depending on the temperature regime of a thermoelectric refrigerator time to the required temperature of the matrix 2 will be within 2-10 minutes With this electric power consumption of thermoelectric refrigerator DC will not exceed 50-55 watts.

Upon completion of the refrigerator power thermopile and the fan is turned off. The cover 6 is removed. thermally capillary released. The refrigerator is removed from the working chamber of the chromatograph.

Continued operation of the gas analysis using a chromatograph, but without the participation of thermoelectric cooler.

The proposed thermoelectric refrigerator for chromatograph compared with the prototype allows to realize the following benefits:

to simplify and reduce the time of installation and dismantling of the cooled object (capillary) in the refrigerator; when the frame Assembly with the mounting screws in the working chamber chromatograph the duration of the installation of the refrigerator will be 10-15 with and about the same time will take the process of capturing the desired capillary exposed in the subsequent cooling is ladimir object (capillary) and the matrix up to 0.2-0.5oC, in the prototype without the introduction of special measures (for example, intensive mixing environment) the temperature difference between the cooled object and the wall of the chamber thermostat will be ~1-3oC;

to reduce the time required operating temperature of the refrigerator to 2-10 min (last numerical value refers to the time limit of the temperature of the cooling mode, i.e. the mode of -30 to -40oC) for prototype - time mode is 30-45 minutes, while the temperature of the temperature is only 0oC;

to reduce power consumption DC with 150 watts for thermostat to 50-55 watts thermoelectric cooler to the chromatograph;

and most importantly, to increase the reliability of thermopile several times while increasing the operating temperature range by dividing it into separate modules running on heat flow in parallel; the cooled matrix is also divided into separate elements interconnected by means of flexible conduits, which leads to equalization of temperature of the cooled elements of the matrix; despite the introduction of structural elements the temperature difference between the cold is and cold junctions of thermopile by no more than 3-5%.

In addition, this constructive solution of the matrix allows the use of the design of the fridge is only one temperature sensor, one channel automatic temperature control, and one power supply thermal modules.

Currently IHPM, Moscow design documentation for thermoelectric cooler for gas chromatograph (Fig. IHPM 062.00.00) the above scheme. The fridge made and is in phase trials.

Sources of information

1. Chromatographic analysis of the environment. TRANS. from English. / Ed. by C. G. Berezkin. - M.: Chemistry, 1979, S. 45-65.

2. Kolenko E. A. Thermoelectric cooling devices. - M.-L.: ed. AN SSSR, 1963.

3. Anatychuk L. N. thermoelements and thermoelectric devices. The Handbook. - Kiev: "Naukova Dumka", 1979, S. 420-436, 453,456.

4. Thermoelectric semiconductor cooling modules. Specifications 003.00.00 THAT. - M.: EHPM, 1996.

Thermoelectric refrigerator for chromatograph consisting of a thermopile cooling, coupled with her cooled matrix, radiator, fan, cases, covers, thermal insulation and temperature sensor, different the th column and parallel to the heat flow, the cooled matrix consists of individual elements made of vysokoteploprovodnyh material, for example copper, and connected by a flexible conduits, such as flexible stranded copper wire, and the joints between the individual elements of the matrix is filled with an elastic sealant, such as sealers, the matrix has a narrow groove of rectangular shape with a width corresponding to the diameter of the capillary, and a depth equal to not less than three diameters of the capillary, the lid has a groove of trapezoidal shape with an angle in the range of 20 - 30othe refrigerator is equipped with quick-release frame and screw clamps.

 

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