SU1469452A1 - Thermostat of chromatograph - Google Patents

Abstract

This invention relates to instrumentation engineering, in particular to thermostats for chromatographs. The aim of the invention is to reduce the temperature gradient in the thermostat volume. The thermostat includes a housing with a door and a cap, on which chromatographic columns are mounted, located in an annular gap formed by the chamber walls and a thin-walled hollow cylinder, which is fixed to the wall of the centrifugal fan coaxially with its shaft. Channels with flaps connecting the chamber to the atmosphere are made in the housing. When the fan impeller is rotated, the air drawn in from the internal volume of the hollow cylinder passes through the air in the wall of the fan, is heated, passes through the heater, and is stirred in the mixing chamber. In the annular gap, where the columns 5 are placed, uniformly heated air flows, which passes further into the cylinder 8, and the cycle repeats. 1 hp ff, 3 ill. from 4 O5. SP IND I Fig.}

Description

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This invention relates to instrumentation engineering, in particular to thermostats for chromatographs.

The purpose of the invention is to reduce the temperature gradient in the volume occupied by the chromatographic column and increase the reliability of the thermostat.

Fig. 1 shows a thermostat with a removed door, a general view; FIG. 2 is a section A-A in FIG. 4 "g. Z - section BB in Fig.1.

The thermostat is placed in the frame 1 of the device and includes a housing 2 with a door 3 and a lid 4 on which chromatographic columns 5 are fixed, located in a uniform annular gap 6 formed by the walls of the thermostat chamber 7 and the thin-walled hollow cylinder 8, which is fixed on the wall 9 of a centrifugal fan 10 coaxially with its shaft 11, the fan 10 also contains a second wall 12, suction nozzles 13 and 14, made in the walls 9 and 12, respectively, a twin impeller 15 with a partition 16 and an engine 17 fixed to the base

SRI 18 connected to the frame t. Of the device and the body 2 of the thermostat. A heater 19 is located around the perimeter of the fan 10. Between the annular gap 6 and the heater 19 there is a mixing chamber 20, in which an average temperature of air in the air flow created by the fan 10 occurs. On the base 18, coaxially with the shaft 11 of the fan 10 is fixed bushing 21 along which a shutter 22 is mounted mounted in channel 23 of housing 2, channel 23 is intended to supply cold air to chamber 7, in the upper part of housing 2 there is a channel 24 designed to discharge hot air from chamber 7 The channel 24 is closed by a valve 25. At the second end of the shaft t1 of the engine 17 of the fan 10 there is an axial fan 26 placed in the channel 27 of the frame 1 of the device. Fan 26 removes air from the internal volume of the appliance heated by the external walls of the thermostat and heated air discharged from the thermostat chamber 7.

The thermostat works as follows.

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The air sucked in by the rotation of the impeller 15 of the fan 10 from the internal volume of the hollow cylinder 8 passes through the suction nozzle 13 in the wall 9 of the fan 10 and is discharged to the ends of the impeller 15. Then the air is heated, pass through the heater 19, and enters the mixing chamber 20, where air mixing occurs. Preheat the air from the mixing chamber 20 evenly into the uniform annular gap 6 formed by the hollow cylinder 8 and the walls of the chamber 7. From the annular gap 6 Air flows through the gap between the end face of the hollow cylinder 8 and the door 3 into the inner part of the hollow cylinder 8, from where it again enters fan 10, and the cycle repeats. The volume of air pumped by the fan to is 15–20 volumes of thermostat chamber 7 per minute. The temperature of the air leaving the annular gap 6 from the mixing chamber 20 is the same around the perimeter of the mixing chamber 20 and the annular gap 6, since the heater 19 is made in the form of a ring covering the fan 10 and the amount of heat per unit time unit of length of the heater 19, equally around its perimeter. The absence of a temperature gradient around the perimeter of column 5 and the temperature difference between column 5 and air in chamber 7 is achieved by ensuring the same conditions of heat exchange and intensification of heat exchange between column 5 and air around the entire perimeter of the column. The same heat exchange conditions around the entire perimeter of the column 5 are ensured by the fact that it is placed in the middle of the annular gap 6 and is blown by a uniformly intense air flow having the same speed and temperature around the entire perimeter of the annular gap b. The diagram of the airflow in the chamber 7 is shown by arrows in FIG. , 2,

The temperature in the chamber 7 is maintained from 80 ° C to a temperature exceeding the ambient temperature by 10-15 ° C, as follows. The valve 22 located in the channel 23 opens, And the valve 25 installed in the-channel 24,

remains closed. The connection of the suction nozzle 14 of the fan 10 with the atmosphere leads to an increase in pressure in the chamber 7, due to which, in the seals of the door 3, the lid 4 and the gaps between the housing 2 and the damper 25 are formed, a small part of the thermal water is formed from the chamber 7 in atmosphere . The amount of heat carried away by the discharged air corresponds to the amount of heat given to the chamber 7 by the evaporator and detector (not shown) heated to the maximum operating temperature, i.e. The temperature of the evaporator and detector does not affect the operation of the thermostat in this temperature range. A small amount of cold air entering chamber 7 through channel 23, passage through heater 19, is heated and in the mixing chamber 20 is mixed with a stream of air circulating in chamber 7. If it is necessary to maintain temperatures close to room temperature, the dampers 22 and 25 open. at the same time.

The thermostat is cooled in the following way. The flaps 22 and 25 open, and due to the vacuum created by the second half of the impeller 15 of the fan Yu, cold air through the suction nozzle 14, channel 23 and the gap between the rear wall of the housing 2 and the base 18 enters the thermostat chamber 7. Hot air due to the pressure generated by the fan 10 is discharged from chamber 7 through channel 24. Three quarters of the volume of incoming cold air is blown through the chamber 7 of the thermostat, cooling it, and one quarter with hot air is blown out of chamber 7 through channel 24. Due to the high performance of the fan 10, the chamber is blown intensively with cold air 7 and hot air is ejected from chamber 7. The cooling time of the thermostat is 400 to 50 ° C. 9-10 min. The partition 16, which divides the impeller 15 of the fan 10 into two parts, is shifted relative to the center of the impeller 15 in the direction of the engine 17, i.e. pr5 of 5

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the water content of the impeller, which provides air circulation in chamber 7, is 3–4 times higher than the performance of the impeller for taking cold air. In order to avoid idle rotation of the second half of the impeller 15 in the temperature-maintaining mode, the suction nozzle 13 of the fan Yu has a diameter greater than the diameters of the partition 16 and the suction nozzle 14. Due to this, the blades of the second half of the impeller 15 are continuations of the blades of the first half of the impeller 15 They are also used to provide air circulation in the sump 7 in the temperature maintenance mode.

The hot air from the thermostat chamber 7 flows into the frame 1 of the device, from where, along with the air flow generated by the axial fan 26, is discharged through the channel 27 to the atmosphere. The air flow in the gap between the thermostat and the frame 1 of the device, created by the fan 26, eliminates the transfer of heat from the columns of the thermostat to other devices located in the frame 1 of the device. In addition, the air flow generated by the fan 26 cools the evaporator radiator and detector output connectors, which, in turn, improves their operating conditions. The pattern of air movement during cooling is shown by arrows in FIG.

The use of the proposed thermostat allows creating a uniform temperature distribution field in the volume occupied by the chromatographic column; ensure that the temperatures of the column and the air in the thermostat chamber match both in the isothermal mode and in the temperature programming mode; increase the reliability of the thermostat by lowering the temperature of the fan motor.

Claims (2)

1. A chromatographic thermostat comprising a heat insulating body, a lid, a column in the form of a tube coiled into a cylindrical coil, inlet and outlet channels for air, a centrifugal fan with an engine, and an open cylindrical skirt located coaxially inside the cylindrical coil coaxially with the fan, different the fact that, in order to reduce the temperature gradient in the volume of the thermostat, the column is placed — in the center of the uniform annular gap formed by the outer casing and the cylindrical skirt; through an annular mixing chamber with an outlet of a fan, equipped with a uniformly distributed annular heater and an additional impeller, which interacts with the outlet of the inlet channel, made of AA ten Go in the rear wall of the thermostat housing and fitted with a controllable flap. 2. Thermostat pop. 1, characterized in that the inlet duct flap is made of thermal insulating material in the form of a truncated cone and is mounted so that it moves along a sleeve fixed to the base coaxially with the fan shaft, and the shape of the duct repeats the flap shape. . l5