DE2135342A1 - LABORATORY THERMOSTAT - Google Patents

Description

July 13, 1971 H K / W (339)

Professor Dr. Bruno Vollmert, Karlsruhe LABORATORY THERMOSTAT

The invention relates to a laboratory thermostat of the open design with a heat transfer fluid container, heating device, temperature control element and circulating pump.

While chemical reactions or process engineering operations are carried out at a constant temperature in production facilities - and usually already in the Pilot plant operation - closed stationary systems are used, are required to carry out measurements and reactions in the laboratory, handy, portable thermostats to which the apparatus to be heated and operated at certain temperatures can easily be connected. These laboratory thermostats are usually operated openly, i.e. the containers in which the liquid used to transfer heat to the recipient, e.g. a reaction vessel, is heated by an immersed tube heater

is, and in which the centrifugal pump required to circulate the heating fluid is usually located, are only partly filled with liquid. This has the advantage that the shaft that drives the centrifugal pump is not connected to a

Stuffing box or some other shaft seal must be provided which, firstly, would considerably increase the engine power and, secondly5 - especially at higher operating temperatures, would require greater expenditure on construction and maintenance. The open design, on the other hand, has the disadvantage that the heating fluids used are constantly exposed to contact with the air above and, especially at higher temperatures, enter the laboratory room in the form of vapors or fine levers.

Since not exist ia all laboratories potent trigger devices - and -also, need not be, for example, in physical Laboratories - leads to a significant nuisance and possibly damage to the health of the staff. In recent times, therefore, some manufacturers of laboratory thermostats have switched to providing the cover of the devices with a cooling device, which can reduce the nuisance caused by oil mist or oxidative decomposition products of the heat transfer fluid, but cannot eliminate it.

Through the contact of the hot heat transfer fluid with of the air in the gas space of the thermostat, the transfer fluid undergoes a progressive oxidative change, the by increasing darkening and / or thickening of the liquid, as well as by the appearance of volatile, unpleasant smelling and irritating the respiratory tract decomposition and oxidation products are noticeable, when using The can use silicone oils as heating and heat transfer fluids Almost unimpeded access of the air humidity will cause an accelerated polycondensation to chew β chukar tigern masses. Sometimes they form under the influence of atmospheric oxygen also insoluble deposits.

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The object of the invention is to create a laboratory thermostat of the open type in which, even at higher temperatures, the disadvantageous development of disruptive vapors and mists as well as the formation of decomposition and oxidation products, polycondensation products, insoluble precipitates and the like is avoided. This object is achieved according to the invention in a laboratory thermostat of the type mentioned in that the heat transfer fluid ^{container is divided into two separate,> preferably one above the other 1} , arranged containers, one of which contains the circulating pump and the heating device and with the inlet and outlet openings for the heat transfer fluid circuit and of which the other has a cooling device connected to the ambient atmosphere, and that the containers are connected via at least one connecting element which allows the passage of heat transfer fluid and which largely prevents mixing of the heat transfer fluid components in the containers.

In this way it is ensured that there is no hot surface of the heat transfer fluid which | * ows (- with the Ambient atmosphere comes into contact. The liquid passage openings provided in the connecting element are in their number, their diameter and their length, to the properties of the heat transfer fluid that Changes in volume of the heat transfer fluid occurring during operation of the thermostat, the temperatures to be maintained with the thermostat, those in the lower container occurring turbulence and the cooling capacity of the cooling device provided in the upper container.

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In the simplest case, the connecting element is a partition attached between the two containers with at least an opening.

The connecting element can also be a hose or a pipe connecting the two containers.

The pipe can be passed through the cooled container and boreholes can be provided in the part of the pipe located in the container. This embodiment has in particular dan Advantage of a low heat exchange between the containers.

A compact construction is achieved if the Circulating pump driving shaft through which at least one opening or the interior of the at least one tube is guided and the diameter of the opening or the inner diameter of the tube is greater than the diameter of the shaft. At this In the embodiment, the heat transfer fluid can pass through the annular gap between the drive shaft and the opening or inner wall of the pipe.

The connecting element can also be designed as a slide bearing for the shaft driving the circulating pump, which shaft has at least one bore connecting the container. at This embodiment ensures that the drive shaft runs smoothly.

The plain bearing can also be in the form of concentric tubes at least one annular gap connecting the containers, so that no special bores are required.

A particularly space-saving structure is achieved if the upper part of the plain bearing is designed as an upper container. The heating device of the thermostat is preferred in a separate container from the lower one, however

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related container provided. This embodiment has the advantage that the circulation pump and the heating device are more easily accessible. In addition, In this embodiment, the drive shaft of the circulation pump be short so that vibration and resonance phenomena are avoided.

In addition to the heating device of the lower container or the container having a heating device connected to the lower container, a cooling device can expediently be provided which is switched on in the event that if the thermostat is connected, for example, to a heat-generating reaction vessel.

The upper container is expediently provided with an overflow so that at higher temperatures and volume expansion of the heat transfer fluid the excess Amount of liquid can flow off.

The upper container containing the cooled heat transfer fluid can be equipped with an inlet pipe for nitrogen or another indifferent gas must be provided. In this way, an atmosphere of nitrogen or some other inert gas can be formed over the surface of the cooled heat transfer liquid so that it does not come with it Comes into contact with oxygen.

To transfer the turbulence in the lower container To avoid on the upper container, radially arranged vertical metal sheets can be arranged in the upper container be.

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In order to keep the heat transfer due to the heat conduction as low as possible, the connecting element can be made of a heat insulating material such as polytetrafluoroethylene, exist.

The exemplary embodiments of the invention shown schematically in the drawings are described below.

A thermostat according to the invention is shown in FIG. in the case of the two cylindrical containers A and B by a means Flange centrally arranged cylindrical tube D are connected, through its interior, the drive shaft 4 of a circulating pump 1, for example a centrifugal pump, with a certain clearance, 8 © that one enters the lower container A. Introduced liquid without great resistance - i.e. in such a way that in BeMIter A there is no over de: i static pressure of the liquid Excess pressure is created - through the connecting pipe B Ia the container B can rise. The length of the pipe D determined - for a given diameter - essentially d & e ÄTjsi according to the fluid and heat exchange between the containers A and B. Since the exchange should be as small as possible, a pipe D as long as possible would be advantageous. Nevertheless, for reasons of construction and handiness of the thermostat, short tubes are generally used Prefer D of a few centimeters in length and prefer to reduce the exchange by a small diameter. In the extreme it is sufficient if the length of the pipe D is only one or a few millimeters. If namely the two containers A and B are arranged directly on top of each other and only through a drilled disc, which e.g. conveniently because of

209884/0833

the better insulating effect of polytetrafluoroethylene, are separated, is the length of the openings containing Fasteners D given by the thickness of this cutting disc. The connecting element D in the sense of the invention can therefore also be a simple bore in a partition between the two containers A and B in extreme cases.

The connecting pipe D will generally be made of the same material from which the containers A and B are made consist e.g. of stainless steel or brass, nickel-plated or / and chrome-plated, but it can also consist of suitable polymeric materials, e.g. polytetrafluoroethylene, which have the advantage of lower heat transfer.

Before the thermostat is put into operation, the elements that are arranged one above the other according to this embodiment and are identified by the Tube D connected to each other, containers Ά and B so far with the liquid used as a heat exchanger, e.g. high-boiling liquid Mineral oil fractions, diphenyl diphenyl oxide mixtures, silicone oils, that fill the oil level with the help of an on the container B attached sight glass 9 becomes visible. If there is no sight glass 9, it is filled through one of the nozzles 7 or 8 heat transfer fluid until it begins to emerge at overflow E. At the inlet and outlet openings 2, 3 is the recipient to be kept at a constant temperature (a reaction vessel or a measuring device or the like) connected, e.g. with the help of hose connections (metal hoses) or fixed pipes.

From the circulation pump 1, the heat transfer fluid is in the operating state conveyed from the thermostat to the recipient and back again. The return is to the lower container A. appeared; therefore, the one in the upper container B takes

209884/0833

Part of the heat transfer fluid does not participate or only to a very small extent in the circuit and remains as a result a built-in cooling device G cold or only moderately when, depending on the intensity of the cooling C, depending on the temperature of the part of the heat transfer fluid located in the circuit and depending on the width of the between the pipe D and the shaft 4 located space.

During the heating process taking place by means of the heating device 5, the heat transfer fluid expands, so that the liquid level in the container B rises so far that part of the liquid overflows at E. The overflow It is therefore advisable to connect a transparent hose that leads to a collecting vessel, e.g. a Bottle or jug. The level of the liquid in the container B can be seen through the sight glass 9 easy to control.

The clearance between the connecting pipe D and the passed through Shaft 4 of the circulation pump 1 should be so far that the heat transfer fluid is at full heating power during of the heating process from the heated container A can expand unhindered into the cooled container B, i.e. with so little Resistance that there is no overpressure in container A, even if the thermostat is connected to a closed heating circuit connected, e.g. to the heating or cooling jacket of a reaction vessel. As a rule, it is sufficient if the Inner diameter of the connecting pipe D, depending on whether there are other connecting channels between the containers in addition to the pipe D A and B are provided, is 0.5 to 5 mm, or if it is slightly larger, e.g. 0.5 to 4 mm larger than the diameter the passing wave 4. (Corresponding survival

209834/0633

Conditions also apply to the bores (10) of the connecting pipe D in the exemplary embodiments in FIGS. 2, 4 a and 5. The diameter of the bores 10 should, for example, be between 0.5 and 4 mm, preferably between 1 and 3 mm, each depending on the size of the heating output and the number of holes.)

You will not make the bores 10 or the clearance between tube D and shaft 4 unnecessarily large because of the exchange (Diffusion or convection) between the two containers A and B should be kept as small as possible. With executions According to Figure 1, it is expedient in the containers B radially arranged vertical thin sheets ("Baffles") to prevent the fluid in B from rotating.

In addition to the heating device 5, a cooling device 6, which can be switched on, can be provided in the container A, when the thermostat is connected to heat-generating reaction vessels.

If the thermostat is to be operated for a long time at high temperatures, e.g. 200 - 300 ° C, the protection can be used perfect the heat transfer fluid by closing the upper container B with a lid and introducing an inert gas, e.g. nitrogen, at 11. The / cover can also be firmly soldered or welded to the container B. or be glued, since the pressure equalization with the atmosphere through the overflow E and / or through the opening is given in the cover through which the shaft 4 is passed. In the exemplary embodiment according to FIG. 2, the Nitrogen introduced through a gas inlet pipe 11 and discharged through a bore 12 and the overflow pipe E again. In this way, every contact becomes the heat transfer fluid avoided with the oxygen in the air.

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The operation of the thermostat according to the invention under nitrogen atmosphere is by no means a necessary one, but only one that is recommended for continuous operation, which means that It is only made possible that as a result of the inventive Arrangement of the surface of the heat transfer fluid in the Container B stays cold, however hot the liquid is in container A.

As a result of the erfindungsgeniäßen structure of the thermostat the hot heat transfer fluid at any point with the ambient atmosphere into contact _s is can - even without an inert gas atmosphere = dis adverse effects of conventional laboratory thermostats set ,, 'as fogging and oxidative modification of Wärraeüberträgerflüsgigkeic even at high operating temperatures, not . The advantages of the open mode of operation, which works without a shaft seal, are fully retained.

The embodiment of the laboratory thermostat according to the invention shown in FIG. 2 differs from that shown in Figure 1 essentially in that the lower container A is connected to the upper container B by a pipe D. which is passed through the container B. Thus, in the embodiment according to FIG. 2, a heat transfer fluid introduced in A through the pipe D into the container B - and back again - are located in the Ln container B located part of the pipe D bores 10. This embodiment of the connecting element D has the Advantage that the liquid and heat exchange between the containers A and B can be made relatively small.

209834/0633

That the base plate 13 carrying the motor 14 is fastened here on the pipe D passed through the container B. and not (as in the embodiment of Figure 1) with the help of the lateral webs 15, only shows that in the inventive Laboratory thermostats numerous variations in the construction details are possible without changing anything in the principle of the invention. For example, the Motor 14 can also be attached by means of a flange located on the upper edge of the container B. Further construction variants consist in that the drive motor of the circulation pump 1 is not mounted on or on the thermostat itself is, but in the usual way in laboratories attached to a stand rod of the laboratory table and via a Movable coupling, e.g. a piece of vacuum hose or a double cardan coupling, with the shaft 4 of the circulation pump 1 connected is. In this case, the shaft 4 is guided and held by a sliding or / and ball bearing (as in the exemplary embodiments of Figures 3 and 4). If the shaft 4 is relatively long, it can be useful be to lead them also at the lower end through a counter bearing 16, as is shown schematically in FIG.

With regard to the heating and control elements, too, all of them can be tried and tested in practice or appear useful in practice Embodiments and variations can be combined with the thermostat according to the invention.

In the embodiment of the invention shown in Figure 3a Laboratory thermostat consists of openings connecting the lower container A with the upper container B. containing element D in a plain bearing for the shaft 4, in which there are a number of bores 10,

209884/0633

through which the heat transfer fluid can pass from container A to container B without major resistance ( and vice versa ). Instead of the holes 10 in the plain bearing - or in addition to these - you can have another one on the side Attach pipe or other connecting pipes D. In this embodiment, the sliding bearing can for the most part lie within the container B containing the cooled heat transfer fluid, so that it is also cooled.

As Figisff 3 Ib ^ © rasischamlichtj kaass the plain bearing also as

There is a gap between the outer tube and the outer tube as an opening

lotiE dmsek Distäassteg © Association is »

Is Figpr 4 ο, will ^ esasseliatiilicfets. that the container B

away isaesf k @ ia £ 3esa & 2fiscli - in addition to wave 4 the BeMlltor A => ardgsoifdtist be smß. Such a non keaseiitrisch © Anosdstiag kasa wegea the ÖBkompliziertheit the Ä4isfüfersing worn? © Advantage "seis _p wean the Theraostatendeckel Flats SGESSg offers ₉ as © bessaäsrs at higher thermostat. The r-isbssa of Beliältsr B arranged bearings you will at disssE · AcasfMireag-sfQrii swscfesäBIgsrweise also cool »

The Elder "is isf§feTctssgsbeispiel Figure 4. b shows an inventiveness geisäßen Lab © £ at®2> * l? 3sasth @ £ ta © stateia ₉ of the slide bearing was designed as Befoalter B at dam DER upper part. The openings for the FläsgigksiSsaTastanscli. are located as bores, 10 ± n the wall of the slide bearing = the area of the overflow E, it is ensured that when the thermostat is heated, the heat transfer fluidity is controlled over the edge of the slide bearing with extremely small WohamsM cügs leliältses E ! mim la special cases advantageous s eis ρ \ y @ su ss on it aMiesatg, Fiats sn save «,

20SSI4 / 0S3

The size ratio of the two containers A and B can be varied within wide limits without affecting the functionality of the device. In general, for reasons of space, container B will be made smaller than container A, for example in the volume ratio V _A / V _B >> 20/1 to 5/1, but in extreme cases, such as in the exemplary embodiment in FIG. 4 b, for example up to 200/1. Experience has shown that working with the thermostat according to the invention is particularly convenient if the container B is so large that the oil level can be reached even when the temperature is rapidly lowered from, for example, 5 to 50 ° C, which occurs when chemical reactions or Series of measurements are often necessary, does not drop to a level below the connecting element D or the bores 10 in the connecting element D. That would make refilling with heat transfer fluid necessary. It must be taken into account that the volume of the total heat transfer fluid can often be a multiple of the thermostat volume.

In the exemplary embodiments of FIGS. 1 and 2, the diameters of the cylindrical containers A and B are same size. But that is not a necessity. The container A can also - as, for example, in FIGS. 3 a and 4 a shown - have a larger diameter than the container ß. This has the advantage that you can use the contact thermometer 18 can be immersed directly into the container A. On the other hand, it is in many cases - especially with the isothermal Carrying out exothermic reactions - advantageous to circulate the smallest possible oil volume, because this means the inertia of the thermostat is reduced, i.e. the device switches from heating to cooling more quickly if through

209884/0633

the "starting" of an exothermic reaction releases heat, wherein in this case the contact thermometer 18 - or at least one of several contact thermometers - not in the thermostat, but immersed in the interior of the reaction vessel.

It is generally customary in laboratory thermostats to use the circulating pump 1, which is usually designed as a centrifugal pump, and c '. To accommodate heating device 5 together in a container. In the construction according to the invention, it can be advantageous - as shown in the detailed exemplary embodiment according to FIG The container A connected to the container B containing the cold heat transfer fluid contains the circulating pump 1. The main advantage of this arrangement is that the circulation pump 1 and heater 5 are more easily accessible so that they can be easily installed and removed independently of one another. A further advantage is that the drive shaft 4 of the circulating pump 1 is particularly short in the embodiment according to FIG. 5 and therefore the vibration and resonance phenomena, which are sometimes annoying with longer shafts, are avoided. You can increase the performance of the circulation pump to a multiple of the performance usual for laboratory thermostats without increasing the total volume of the thermostat, since the dimensions of the container F, which is spatially separated from the container A, can be kept relatively small. As practice has shown, one can measure the volume of the circulating water

209884/0633

Heat transfer fluid - as far as the proportion in the thermostat is concerned - for arrangements according to the type of Lower figure 5 to less than 1 liter.

This is a great advantage when using high-quality media such as silicone oils and generally when using the Thermostats for isothermal implementation of chemical reactions (contact thermometer in reactor). The lower in this case the volume of the circulating heat transfer fluid, the faster the theory speaks. * v .-- f impulses des Control system,

The volume of the thermostat erfindungsgemäSen divides sicln in the embodiment of Figure 5 on gsmäS ule two containers A and F on. When in Fig-Λΐ? ^ Iistraktion K shown in Figure 5 accounts for the greater part of the volume of the container F. Man, however, the structure can easily ebesse also run such that both '^ hältex A and F are the same size or the container A is greater. As to: BÄMlter F.

In Figure 5, the two containers A ui-.VF attvr are connected to each other by the pipe section 17, ν, ηά the gauge arrangement is placed in a box filled with insulating material, which can be made of sheet metal, but also of plastic. In many cases it can be useful to set up the two retainers A and F at a greater distance from each other or to attach them to stand rods and to connect them diareti with a flexible, insulated metal hose »

The way in which the recipient is connected should also not be determined by Figure 5 "Man ksna - whom? it au "some reason appropriate appear" just as the Rezipienter directly to the circulation pump anschlisSsn * From, recipient gelange Ί * Ήε WMrmetragerflussigkfeit. in aev container F

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ΠΏή 7 (3Si Uu ¹ pc in that! LeMltesr 4 bsu? ₀ la circulation pump. As dis loMIlter A sasd F are arranged Saich, always the FsirdGrasÜg Filled ,, -ggs © © is introduced in © Is the BeMIter A J? 2 , tl3sigkQ.iiä "(© das Qims see, there the tarch card expanding? Ji'S3oig! ieife) Güi £ © ti the Ferfeiüdisags © reads D in the chilled

AjLg SQgQloÜQaeistG ¥ G2Aj®iüidet ess boi L la ©! © Ε ¹ EQgsl QiaQeksiFß'dr ^ ICoatakttfecsrsiOiseterj the with a t-Sür <Si @ ö-Ilelaic3 s @ fe @ ppelt siad ₀ The EC @ 2ίktometer can disfG-£ iataktthena d © sa Bsltältee A ei®tai2efesa _D it can also be of the ventilator A in the eiaeis lateral connection or

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b @ £ dea Äissfükizii, agsb © ispl © l nacb. Figure -5 or in the interior eia © s leakti © iass © fäBes feefisdon «

Ifeiara siefep as iia desi ÄissfühnÄisgsfeelspielea vmä to 1 2 ₉ the © iataktthersioEeter 18! Aiasserlialb of Thenaostaten "Behs> lt @ 3T8 Δ befiüäetj, dnrcfe .eime" measure simple electrical Schaltnag be taken to ensure "that the heating circuit is immediately ^one CSBtesferoelisai _f If for whatever reason (e.g. due to a misunderstanding of the motor or a defect in the motor) the circulation pump fails ο

With particularly high demands on the temperature constancy, it is advisable to connect the Heistang with the help of a Thyristorctisltemg in a known way so that the heating output can be continuously regulated _? whereby only a small part of the preselected heating output for controlling the TeraperatBr is switched off and on by the contact thermeaster ο

Claims (1)

- 17 - 7 ^s a;:. '. ^ W': cμ T \ Uc ¹ V ⁴ Cr. Laboratory thermostat of the open design with heat transfer fluid container, heating device, temperature control element and circulating pump, characterized in that the heat transfer fluid container is divided into two separately arranged containers (A, B), one of which (A) the circulating pump (1) and the heating device (5) contains and is connected to the inlet and outlet openings (2,3) for the heat transfer fluid circuit and of which the other, connected to the ambient atmosphere (B) has a cooling device (C), and that the container (A ₅₁ B) are connected via at least one connecting element (D) which allows the passage of heat transfer fluid and which largely prevents mixing of the heat transfer fluid components in the containers (A, B-). Laboratory thermostat according to Claim 1, characterized in that the cooled container (B) is arranged above the container (A). Laboratory thermostat according to claim 1 or 2, characterized in that the connecting element (D) is a Partition wall with at least one opening. Laboratory thermostat according to Claim 1 or 2, characterized characterized in that the connecting element (D) is a hose or pipe (Figure 1). Laboratory thermostat according to one of Claims 1 to 4, characterized in that the connecting element is passed through the container (B) and bores (10) are provided in the part of this element located in the container (B) (Figures 2, 4a, 5). 209884/0633 '; ^"::: '5342 6. Laboratory thermostat according to one or more of claims 3 to 5, characterized in that the the circulation pump (1) driving shaft (4) through the at least one opening or the interior of the at least a connecting element is guided and the diameter of the opening or the inner diameter of the connecting element is larger than the diameter of the shaft (4) (Figure 1,2). 7. Laboratory thermo etat according to claim 1 or 2, characterized characterized in that the connecting element (D) as a plain bearing for which the circulating pump (1) driving shaft (4) is designed, which is the container (A, B) connecting bore (10) (Figure 3a). 8. Laboratory thermostat according to claim 1 or 2, characterized characterized in that the connecting element (D) acts as a slide bearing for the shaft (4) that drives the circulating pump (1) is formed, which concentric tubes with at least one annular gap connecting the containers (A, B) has (Figure 3 b) " 9. Laboratory thermostat according to claim 7 or 8, characterized characterized in that the upper part of the plain bearing is designed as a container (B) (Figure 4 b). 10. Laboratory thermostat according to one or more of the claims 1 to 9, characterized in that the heating device (5) is spatially located in one of the container (A) separate, old container (A) in connection with container (F) is located (Figure 5). 11. Laboratory thermostat according to one or more of the claims 1 to 10, characterized in that the container (A) and / or the container (F) have a cooling device (6). 209884/0633 12. Laboratory thermostat according to one or more of claims 1 to 11, characterized in that the Container (B) with an overflow *. U) is provided. 13. Laboratory Thermostat according to one or more of claims 1 to 12, characterized in that _f into the container (B) a nitrogen-introducing tube (11) aündet (Figures 1, 2). 14. Laboratory thermostat after one or more of the Claims 1 to 13, characterized in that in the container (B) radially arranged vertical sheets are arranged. 15. Laboratory thermostat according to one or more of the claims 1 to 14, characterized in that 4ass the connecting element (D) made of a thermal insulating material, for example polytetrafluoroethylene exists. IO . Blank page