DE8807292U1 - Gas-refrigerant heat exchangers, especially for compressed air dryers - Google Patents

Description

DR.-1NC.

PATENT ATTORNEY D-4OOO DÜSSELDORF I · SCHADOWPLATZ 9

Dusseldorf, 27 May 1988

8818

VIA Society for Process Engineering mbH 4000 Düsseldorf 11

Gas-refrigerant heat exchangers, especially for compressed air dryers

The invention relates to a gas-refrigerant heat exchanger, in particular for compressed air dryers, consisting of a first pipe coil for passing through gas to be cooled and a second pipe coil for passing through refrigerant, the second pipe coil being in direct heat transfer contact with the first pipe coil at least over a partial extension of the latter.

A compressed air dryer using a gas-refrigerant heat exchanger of the above type is shown in Fig. 2.

Direct thermal contact for heat transfer from the surface of the gas-carrying pipe coil to the surface of the coolant-carrying pipe coil is a very simple way of heat transfer, but is not sufficient for some applications

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effective. Due to the line contact used between the two pipe coils as shown in this figure, the heat transfer resistance is quite high even when materials with high thermal conductivity such as copper are used. This not only reduces the efficiency of the arrangement, but also means that certain heat exchanger surfaces touched by the compressed air to be dried, which are relatively far away from the line contact, do not become cold enough to achieve the desired dew point reduction. If the coolant temperature ^is reduced so far r,b that these areas reach an exceptionally low temperature, there are other areas close to the line contact that become too cold and lead to the freezing of water vapor, for example, which not only increases the flow resistance for compressed air but can lead to the complete failure of the compressed air dryer.

In order to obtain evenly cooled heat exchange surfaces, so that no places with excessive cooling and no other places with insufficient cooling arise, it is already known to design the two pipe coils as a pipe-in-pipe construction. For this purpose, a pipe of larger diameter is arranged over a pipe (or several pipes) of smaller diameter and coolant is passed through one pipe, preferably the inner pipe (or the inner pipes), while the other pipe, preferably the outer pipe, is exposed to the air to be dried. A third pipe can then be arranged around this second pipe, which in turn carries coolant, so that all surfaces touched by gas are kept at coolant temperature. This pipe-in-pipe-in-pipe construction, see for example the applicant's DE 2709961 C2, as well as the pipe-in-pipe constructions mentioned above, work in themselves

quite satisfactory, but are very complex to produce.

Yet another possibility is shown in the applicant's European patent publication 0179987, in which a gas-refrigerant heat exchanger is used in which the two pipe coils are not in direct heat contact, but are arranged in a common, heat-storing and conductive liquid, which, through its heat storage properties, ensures that the temperature of the pipe walls through which the compressed air flows is as uniform as possible. However, this arrangement also has disadvantages: If water or a water-salt solution (brine) is used, the special property of water, namely that it reaches its greatest density at 4°C, becomes detrimental. This means that, particularly in the working range of such a dryer, the dependence of the medium density on the temperature approaches zero. Different temperatures therefore lead to no or only slight convection, so that the brine, which acts as a "thermal mass", is a poor heat conductor. This has various disadvantages: If, for example, less than 20 % of the nominal power is required from the compressed air dryer, the entire system, as shown in Fig. 2, can go into what is known as intermittent operation, because the thermal inertia of the thermal mass can bridge the times between shutdowns. However, if a lot of power, for example almost nominal power, is suddenly required shortly after switching on again during intermittent operation, the heat exchanger is then no longer able to supply sufficient cooling power to the compressed air via the thermal mass, so that insufficiently dehumidified compressed air is then released, at least for a certain period of time.

If you want to avoid this disadvantage, you have to do without intermittent operation and ensure continuous cooling at 100% capacity, whereby the unused cooling energy must then be removed via a bypass line (hot water bypass valve arrangement) to avoid icing. However, this process is very energy-intensive because full cooling capacity must always be provided and ultimately, as a result, the cooling capacity must be reduced.

The aim of the present invention is to create a gas-refrigerant heat exchanger of the type mentioned at the beginning, with which partial load operation (with switching off the refrigeration machine) is also possible without the risk of freezing, and which is nevertheless able to deliver the cooling capacity required for full load without "dead time" in the event of a sudden full load (after partial load operation).

Furthermore, the gas-refrigerant heat exchanger should be designed in such a way that it enables a compact, if possible even modular, structure and causes relatively low manufacturing costs.

The problem is solved in that the first and the second pipe coil each have the shape of a truncated cone-like helix, each of which has the same helix pitch and is arranged one inside the other in such a way that essentially each helix turn of one pipe coil is touched by two adjacent helix turns of the other pipe coil along a line parallel to the pipe axis.

This measure not only results in a doubled increase in performance compared to the state of the art described at the beginning,

linear contact area, the two contact lines are also radially spread out around the pipe coil cross-section, so that with the help of the thermal conductivity of the pipe material, a largely equalized wall temperature can be achieved, while simultaneously reducing the heat transfer resistance. In addition, the arrangement is very easy to manufacture in a manner to be described and also has partially self-supporting properties.

The truncated cone-shaped spiral shape not only has advantages in terms of manufacturing technology and the improved heat distribution and heat transfer properties already described, the conical shape also results in very special turbulence processes that were only discovered through testing, which result in an even greater homogenization of the heat or cold transfer from the coolant to the gas to be cooled.

The above problem can be solved in principle by this geometric arrangement according to the invention, although this solution can be improved in various ways by further measures. PS has shown that when the pipe coils are spatially arranged in such a way that the truncated cone axis is essentially vertical and the truncated cone end with the larger diameter is at the top, the turbulence properties and thus the evening out of the heat transfer and the reduction in the heat transfer resistance are even greater.

In order to save material, it can be advantageous if, according to yet another embodiment, the pipe coil for the coolant is made of pipe material with a smaller diameter than that of the pipe material for the gas.

becomes.

It is also helpful to solve the problem if the pipe coil for the coolant comprises two branches, the first branch having a first truncated cone arranged inside the truncated cone formed by the gas pipe coil and the second branch having a truncated cone arranged outside the truncated cone of the gas pipe coil. Essentially, each spiral turn of the G4,3 pipe coil is touched by four adjacent spiral turns of the coolant pipe coil branches along lines parallel to the gas pipe axis. In this way, the number of linear contact areas for each gas-carrying pipe can be doubled from two to four, with only a slightly higher expenditure on material and labor costs.

It is advantageous if the upper end of the gas pipe coil is connected to a gas supply connection and the lower end to the gas discharge connection, while the lower end of the refrigerant pipe (or the lower ends of the refrigerant pipes) are connected to the refrigerant supply connection and the upper end (or the upper ends) to the refrigerant discharge connection. This results in a favorable countercurrent arrangement with particularly advantageous cooling properties. If two refrigerant pipes are present, they can be connected in parallel or, to achieve greater evaporation efficiency, in series one after the other.

It is advisable to enclose the pipe-sleeve arrangement in a housing which is filled with a heat-transferring/heat-storing mass (so-called thermal mass), whereby this thermal mass can be provided as a liquid, such as brine, water-hydroxide mixture or

etc. This measure further improves the heat transfer properties, as well as the heat storage properties, which in turn brings additional advantages in terms of solving the problem. If brine or a water-glycol mixture or another liquid is used, the housing must be made permanently liquid-tight and also kept tight. This can be annoying under certain circumstances, so that according to yet another embodiment, in which the housing is only essentially liquid-tight, the heat-transferring/heat-storing mass is a liquid or paste whose viscosity is high or which becomes high after being filled into the housing or which also solidifies completely. Such a thermal mass can be formed, for example, from coal dust which is formed into a paste with a liquid such as brine or the like or also with antifreeze, so that even if the housing is slightly leaky, the thermal mass cannot escape from the housing or can only escape in insignificant quantities. This results in significant handling advantages during production, especially since coal dust in combination with the liquid coolant has proven in tests to be a particularly good heat conductor as well as a particularly good heat storage medium.

Compared to the pipe-in-pipe design, for example, the design in question here has extraordinarily large average cross-sections, so that the flow resistance, especially for the gas to be treated, is significantly lower than in a pipe-in-pipe system with comparable performance. Due to the reduced flow resistance, the pressure losses in the new design are also much lower. The resulting lower flow velocity, which normally leads to less vortex formation and thus to poorer heat

The difference that would otherwise lead to poor transition properties is compensated for here, due to the special shape of the truncated cone-like spiral, which in turn results in additional turbulence effects. It has proven to be advantageous that the turbulence effects increase as the radius of the conical spiral becomes smaller and that the temperature difference between the coolant or thermal mass and the gas to be cooled decreases. The decreasing temperature difference is thus at least partially compensated for by the improved heat transfer as a result of the increasing vortex formation.

Tests have shown that, for the same pipe length, a cylindrical pipe coil has a pressure drop that is 10 to 15 % higher and a cooling temperature that is 2 to 4 ^° C worse than is the case with the conical pipe coil according to the invention, which achieves an optimum between pressure drop and heat transfer.

A temperature sensor is provided to check the temperature of the escaping gas and also to regulate the temperature of the coolant. The gas-refrigerant heat exchanger according to the invention makes it possible to choose an optimal arrangement here: According to a further development of the invention, a temperature sensor can be provided at the lower end of the housing, which is in thermal contact with the escaping gas on the one hand and with the thermal mass on the other. In particular, this temperature sensor could be a sensor that can be inserted into a metal tube (immersion sleeve), with the immersion sleeve being welded or soldered to a metal cylinder or nozzle through which the escaping gas flows and which in turn is embedded in the thermal mass. The temperature sensor thus records

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sensor not only measures the temperature of the gas coming out of the heat exchanger*/ but also partly the temperature of the thermal mass, whereby the proportions of the two temperature influences can be controlled by appropriate shaping in order to achieve optimal operating properties. The operation is particularly problematic when no compressed air is used for a time and therefore no gas flow takes place in the heat exchanger. In this case, measuring the temperature is particularly difficult and is ensured according to the invention by using the temperature of the thermal mass instead of the temperature of the gas. The switching accuracy can be significantly improved as a result.

A further advantage of the novel arrangement is that it can be designed so that an upper part of the outer branch ⁰ of the refrigerant pipe can be replaced by a gas pipe, the lower end of which is connected to the lower end of the gas pipe coil - if necessary with the interposition of a condensate separator and/or other gas treatment arrangements - and the upper end of which is connected to the gas discharge connection. In this way, a gas-gas heat exchanger is practically integrated into the gas-refrigerant heat exchanger without the space requirements increasing significantly. Such a gas-gas heat exchanger in addition to the gas-refrigerant heat exchanger increases the efficiency of the arrangement considerably because gas that still needs to be dried can be pre-cooled by cooled and dried gas and at the same time the dried gas can be warmed up to approximately room temperature again without additional heating devices being required. The integration not only makes the overall arrangement more compact, it also reduces the number of necessary connections, making the overall arrangement even more cost-effective.

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It should be added that the additional gas treatment devices already mentioned can also be arranged in the cone if necessary, for example collecting groove separation devices as described in the applicant's EU patent application 88102966.4.

The invention also relates to the use of such a gas-refrigerant heat exchanger as described above in a compressed air dryer which has a thermostat-controlled refrigeration machine for compressing the refrigerant and a condensate separator, which is advantageously a collecting groove condensate separator. The advantage of the new design is that this design can very easily be made into a module for constructing compressed air dryers with graduated nominal output. A key reason for this use as a module is that, due to the design, the flow resistances of the pipe coils, provided they have the same nominal output, are identical within very small tolerances. In previously known designs, in particular in the pipe-in-pipe design, there were considerably greater deviations in terms of flow resistance due to manufacturing, even with an identical basic design. However, in the case of larger deviations, a direct fluidic parallel connection of pipe coils of individual components is no longer possible, because otherwise the individual components would be loaded to very different levels. In the design according to the invention, however, the deviations are so small that this problem no longer exists.

Another advantage is that the funnel shape means that the individual pipe coils can not only be arranged next to each other but, if necessary, using partial

Can be plugged into one another

The modular design not only has manufacturing advantages (manufacturability of larger series of only one
performance class and thus price reductions even for higher performance classes, which can be achieved by parallel connection of modules), further advantages can be
namely, that additional operational safety can be achieved in a simple way: For example, if two modules of the same nominal load are provided with associated compressors,
enable a control method in which
If one module malfunctions or fails, it is switched off and the other one is automatically switched on.

In addition to different performance values, modules can also be provided for different operating pressures and/or different dew points, which is advantageous in certain applications. The control devices
can also be designed in such a way that they are independent
from the actual device, for example remotely at a monitoring center.

To manufacture a pipe coil for the construction of a gas-refrigerant heat exchanger of the type described above,

use the following procedure:

a) On a truncated cone-shaped mandrel with a distance
Spiral-shaped retaining grooves arranged according to the largest pipe diameter are used to hold a pipe
spirally wound and fixed;

b) on the conical spiral thus formed, another tube of the same diameter is placed in the spiral recesses.
or smaller diameter wound and fixed.

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d) the mandrel is removed from the spiral coil by unscrewing or pulling it out.

This allows the winding of both the

The gas pipe and the refrigerant pipe can be wound very easily into the desired conical spiral shape without the need to take special measures that are otherwise often necessary to prevent the pipe volumes from narrowing in an unfavorable way during winding. The production can also be modified by winding a refrigerant pipe onto a mandrel of the same dimensions as in step a) and fixing it and then screwing a pipe coil spiral, which has already been manufactured according to steps a), b), c) described above, onto the spiral according to the present step b (which is possible due to the spiral shape) or winding it and then fixing it.

The spiral can be fixed after it has been wound onto the mandrel by soldering, in particular by an axially aligned solder seam applied outside the surface area required for "screwing the spiral". Alternatively, other fixing methods such as gluing, welding and the like are of course also possible, but soldering has proven to be particularly advantageous for the copper materials most commonly used here.

To increase the heat transfer, it is advantageous to fill the gaps between adjacent pipes with metal, i.e. to form fillet welds, which can be done by immersing them in a soldering bath, or by placing the entire arrangement in a galvanic bath and galvanically applying the metal, or by spraying the fillets with metallic powder, so-called fillet welds.

so-called application spraying. j

The invention is explained in more detail using embodiments shown in the drawings.

It shows:

Fig. 1 shows a gas-refrigerant heat exchanger according to a first embodiment of the invention;

Fig. 2 is a schematic representation of a compressed air dryer unit, with which an application for the gas-refrigerant heat exchanger shown in Fig. 1 is to be explained;

Fig. 3 shows a further embodiment of the gas-refrigerant heat exchanger according to the invention in a similar but schematic representation as in Fig. 1 ;

Fig. 4 in a similar representation to Fig. 3, yet another embodiment with integrated gas-gas heat exchanger;

Fig. 5 is a schematic representation of different possibilities for combining different pipe types with the same cone angle;

Fig. 6 is a schematic representation of the arrangement of a gas-refrigerant heat exchanger designed according to the invention in an insulating housing;

Fig. 7 shows in a perspective view components of an equipment box to be installed under the housing according to Fig. 6 for further components of a compressed air dryer;

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Fig. 3 shows in a perspective view two housing units according to Fig. 6, mounted on a common device box according to Fig. 7 and in connection with a remote control device;

Fig. 9 in a similar representation as Fig. 3 a
Possibility of using a gas-refrigerant heat exchanger according to the invention in particularly
It is advisable to arrange a temperature sensor suitable for control purposes;

Fig. 10 in a perspective view a

Insulated housing with an integrated gas-refrigerant heat exchanger according to the invention, whereby the housing is not round but teardrop-shaped;

Fig. 11 shows a similarly designed housing shape in a plan view;

Fig. 12 in another top view the possibility

to combine two (up to four) such housings according to Fig. 11;

Fig. 13 a tabular representation of how by combining different modules different
nominal value ranges can be achieved;

Fig. 14
and 15

also in schematic representations further possibilities for combining modal. -;- sr different designs.

Fig. 1 shows a side view and a partial

Sectional view of a gas-refrigerant heat exchanger 10, consisting of a first pipe coil or coil 12 for passing gas 14 to be cooled, for example compressed air to be dried, and a second pipe coil or coil 16 for passing refrigerant 18, preferably, as also shown, in countercurrent direction. As can be seen from the illustration, the second pipe coil 16 is in direct thermal contact with the first pipe coil or gas pipe coil 12, see for example the contact point 20. A direct juxtaposition of two pipe coils, such that a line contact is created, is also evident from the illustration in Fig. 2, in which a compressed air dryer 22 is shown schematically in which a gas-refrigerant heat exchanger 110 is formed by a first pipe coil 112 and a second pipe coil 116, which according to this schematic illustration are arranged in a serpentine shape in line contact with one another. As is usual with such compressed air dryers to increase efficiency, there is a gas-gas heat exchanger 124 above the gas-refrigerant heat exchanger 110, consisting of a continuation of the gas pipe coil 112 up to a connection piece 126 for compressed air 14 to be treated, and of a further pipe coil 128, again in line contact with it, which is connected at its upper end to a further connection piece 130 for the discharge of treated gas 15. The refrigerant coil 116 is connected at its supply end (bottom) via a so-called thermal expansion valve 130, which is controlled by the temperature of the outlet end of the coil, to a source 132 for refrigerant, consisting of a refrigerant compressor 134, an air-cooled refrigerant condenser 136 and a hot gas bypass valve 138, which is usually present in state-of-the-art systems.

The lower end of the pipe coil carrying the gas within the gas-refrigerant heat exchanger 110 opens into a separation system for condensate and other impurities, reference number 140, where separated moisture collects and is expelled via a solenoid valve 142 serving as a condensate drain. The gas, for example compressed air, which has thus been largely freed of impurities and in particular moisture, then flows upwards in the embodiment shown here, flows through an oil filter 144 to separate any remaining fine oil droplets and then reaches the lower end of the gas pipe coil 128, where the gas absorbs heat again by cooling the pipe wall of this pipe coil 128 and the pipe wall of the pipe 112 in thermal contact with it within the gas-gas heat exchanger 124. As a result, the gas 14 to be treated, which enters via connection 126 and flows in the opposite direction, is in turn pre-cooled, while on the other hand the treated gas is warmed before exiting from the nozzle 127. The pre-cooled gas then passes from the gas-gas heat exchanger 24 into the gas-refrigerant heat exchanger 110 and is there in turn cooled to a temperature close to 0° by thermal contact with the pipe walls, which in turn are in thermal contact with the pipe walls of the refrigerant pipe 116, so that moisture initially contained in the gas in gaseous form precipitates as a liquid in the form of drops 146 and condenses and collects in the condensate separation system 140.

While according to Fig. 2 the pipe coil 112 for gas is only touched along a single common contact line along the axial direction of the pipe coil for coolant 116, so that the heat transfer resistance remains relatively high, this is different in the illustration according to Fig. 1 in that there both the pipe coil 12 for gas to be treated and the

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The pipe coil 16 for coolant each has the shape of a truncated cone-like spiral 27 or 29, which each have the same spiral pitch S, and are arranged one inside the other in such a way that essentially each spiral turn of one pipe coil, see for example reference number 31 or 33, is touched by two adjacent spiral turns of the other pipe coil, see the reference numbers 33, 35 or 31, 37 along a line parallel to the pipe axis, see for example the contact point 20, which has already been mentioned.

Because there are now two contact lines, instead of just one, as in the illustration in Fig. 2, the heat transfer increases to almost double, at the same time the distribution of the cold over the cross-section of a pipe through which the gas flows is evened out, thus improving the operation of the arrangement.

The production of these two spiral structures 27, 29 is carried out in a simple manner by providing a truncated cone-shaped mandrel 39 with spirally arranged retaining grooves 41, 43 or 45, the distance between which corresponds to the diameter of the gas pipe to be wound up. The retaining grooves can be adapted exactly to the curve of the outer circumference of the gas pipe to be wound up, see reference number 43, or simplified, have a triangular round shape, reference number 41, or simply form steps 45, one step line of which is parallel and the other perpendicular to the axis 47 of the mandrel 39. After winding up the gas pipe and thus forming the spiral 27, possibly also forming the connection areas 51 and 49 and fixing them using the appropriate measures, such as clamping devices or some soldering points or soldering seams, the conical spiral or spiral 27 thus formed is then pushed into the spiral recesses which are formed by

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the individual turns of the spiral, a cooling medium tube is wound up and the second spiral 29 is formed in this way, which is then in turn fixed, for example by soldering 53, which is preferably guided in a line along the cone shell from the upper to the lower end, in order to mechanically connect the individual tubes to the other adjacent tubes. The filling of the fillet welds with metal that occurs in this way also results in an even better heat transfer between adjacent tubes. The filling of the fillet welds can be done by dipping in a soldering bath, alternatively metal can also be introduced into the fillet welds galvanically or by powder spraying. At the same time, the ends of the second coiled tube 29 can also be bent into a suitable shape, see reference numbers 55, 57. The connections should be bent in such a way that the core 39 can now be pulled upwards, for example if the groove shape was designed according to reference number 45, or like a screw can be unscrewed from a nut, _namely if a groove shape was selected according to reference numbers 41 or 43. If the connection 49 or 55 is to be bent inwards for later assembly reasons, or in the case of immersion bath soldering, it is advisable to remove the mandrel 39 beforehand.

The manufacturing process described is extremely simple and efficient and results in very uniform pipe cross-sections, in contrast to designs in which a pipe-in-pipe arrangement is chosen. The procedure is also very flexible, since with just one mandrel of the appropriate extension and fixed cone angle 59, spirals of very different diameters but always the same cone angle 59 can be produced, depending on where on the cone the winding begins.

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started and at which point it ends. The mandrel must be adapted in terms of its spiral pitch S to the outer diameter of the pipe with the largest diameter, in this case it is the pipe that forms the spiral 2 7.

Different pipe types for different performance classes were investigated and these are shown schematically in Fig. 5. A letter designation is given, which later in another representation shows the corresponding performance in cbm of compressed air per hour, see Fig. 13.

If you imagine line 60 in Fig. 5 as the conical shell of a dome, which is provided on its outer surface with spiral-shaped retaining grooves for pipes to be wound up with a spiral pitch S that corresponds to the outer diameter of the pipe with the larger diameter, you can also first wind the pipe with the smaller diameter into these grooves, whereby the specified distances then arise between the individual turns of the pipe with the smaller diameter, and then wind the pipe with the larger diameter between every two such turns. This creates an inverted arrangement, with an internal pipe coil, for example for coolant, onto which the pipe with the larger diameter is then wound as a gas-carrying pipe, whereby the turns of this gas-carrying pipe touch each other, in contrast to the turns of the coolant-carrying pipe, which are spaced apart from each other. Fig. 3 shows an arrangement in which an inner conical spiral made of a smaller diameter pipe for coolant is followed by a second pipe spiral 27 with mutually touching turns of a larger diameter pipe for gas flow.

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is arranged. A further coil 29 made of pipe of a smaller diameter can then be attached to this construction in the manner already described at the beginning, again for the passage of coolant. Due to the screw shape, however, a manufacturing process is also possible in which the coil 61 is manufactured independently of the coil 27 (if necessary with the coil 29 attached). After completion and appropriate fixing (and appropriate provision with regard to the connecting pieces), the finished coil 61 can then be inserted into a finished coil 27 from above and "screwed in" with regard to the last piece. Three (or more) coils can also be combined in this way.

The construction shown schematically in Fig. 3 is similar to that of Fig. 1, but has the advantage that the refrigerant coil comprises two branches, reference numbers 29 and 61, whereby the first branch 61 forms a first truncated cone 61 arranged inside the truncated cone 27 formed by the gas coil and the second branch forms a truncated cone 29 arranged outside the truncated cone 27 of the gas coil, such that essentially every spiral turn of the gas coil (apart from the uppermost edge turn) is touched by four adjacent spiral turns of the two refrigerant coil branches 61, 29 along lines parallel to the gas coil axis. This quadruples the contact area or the heat transfer increases to almost four times and evens out even further across the surface of the gas pipe. The branches 61, 29 can later be connected in parallel, as indicated in Fig. 1, or in series, as shown in Fig. 9.

Both embodiments, both those of Fig. 1 and

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those of Fig. 3 are characterized in that the tube spirals are spatially arranged in such a way that the truncated cone axis 47 is essentially vertical and the truncated cone end with the larger diameter is at the top. At the same time, the flow direction of the gas flow is directed from top to bottom, similar to Fig. 2, see arrow 14 in Fig. 1 and 3. During its downward spiral movement, centrifugal force and torque change, and it is assumed that these effects create additional vortex forces that lead to a desired higher turbulence and thus an increased heat transfer coefficient in the lower area of the spiral, which advantageously compensates for the reduced temperature difference between the gas to be cooled and the coolant at the lower end of the conical spiral, because the gas is colder at the lower end of the spiral than at the upper end.

Fig. 4 shows yet another embodiment in which part of the outer branch 29 of the coolant coil is replaced by a gas coil 28, which corresponds to the coil 128 in the gas-gas heat exchanger according to Fig. 2 and serves to at least partially reheat the dried air that exits from the condensate separator and other devices (not shown in Fig. 4) before it is delivered to the consumer, namely by thermal contact with the upper turns of the coil 27, into which still warm gas to be treated enters, which in turn is precooled in this way.

A condensate separator, as shown schematically in Fig. 2 with the reference number 140, possibly also in connection with a filter, can be inserted into the coil according to Fig. 1, 3 or 4 in place of the dome 39 and thus can be accommodated in a space-saving manner. Fig. 6 shows such a

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Construction r, '-eniatic, whereby a gas-refrigerant heat exchanger IC according to Fig. 4 is mounted on a plate 63, whereby either supply and discharge lines, which are led through the plate 63 and soldered to it, serve as a support, or specially provided struts. For reasons of saving space, it can be expedient to install a condensate separator of a corresponding shape, if necessary also an associated oil filter, inside the coils made by the truncated cone. 61, 27, 28 formed space, which would also have the advantage that the connecting lines between, for example, the lower end 51 of the coil 27 and the condensate separator, see reference number 140 in Fig. 6, remain short, as does the connecting line between the upper end of the condensate separator and the connection 65 at the lower end of the coil 28. The upper connecting line of the coil 28, reference number 67, as well as the connection 49 for the supply of gas 14 to be treated or for the discharge of treated gas 15 are led out upwards according to Fig. 6 and could end in a corresponding connecting piece in a cover 69, see also Fig. 8, where such connecting pieces with threads can be seen in a housing cover. A connection for the refrigerant supply is then led downwards, while the refrigerant discharge 19 in Fig. 4 is not bent upwards but downwards and at 19 according to Fig. 6 is also led through the plate 63 and is, for example, soldered tightly to it. The further discharge line, which is designated 73 and leads to the condensate separator 140, is used to discharge condensate and is also soldered tightly into the plate 63.

j This base plate 63 with the attached modular gas-refrigerant heat exchanger and condensate separator can then be

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Insert the sealing ring 75 into a cup-shaped, preferably round housing 77, which has a corresponding opening 79 for the passage of the connecting pipes 18, 15 and 73. With the help of fastening means also soldered to the plate, for example a screw bolt 81, the plate 63 can then be fastened to the housing base 83 and, if necessary, simultaneously to the cover plate 85 of another rectangular housing 87, which contains further components of a compressed air dryer, such as in particular the compressor 134, the condenser 136, the condensate drain valve 142 and, if necessary, control and display devices, provided that these are not housed at a remote location, see reference number 89 in Fig. The housing 77 is preferably liquid-tight, just as the passages of the lines 18, 73 and 19 through the base plate 63 are designed to be liquid-tight, and the plate 63 has a liquid-tight connection to the container base 83 as a result of the seal 75. After inserting the gas-refrigerant heat exchanger 10 according to Fig. 6 in the container 77, the housing can be filled with a heat-transferring/heat-storing mass, for example with brine, or with a water-glycol mixture, or, what has proven particularly effective, with a paste obtained by mixing coal dust or similar with a liquid such as brine or antifreeze. Then, after tightly connecting or passing the supply lines 14 and 15 through the cover, for which the opening 91 can be used, the container 77 is also sealed liquid-tight at the top so that it can now be handled without problems. The liquid tightness does not need to be particularly good or only needs to be guaranteed temporarily provided that the heat-transferring/heat-storing liquid chosen is one that is initially only liquid or viscous when filled and thus reaches all angles between the individual pipe coils

and fills, after which this liquid or viscous liquid can then solidify or harden completely to such an extent that the tightness of the container is no longer important.

One such mass would be bitumen, for example, whereby this type of thermal mass has the advantage that it cannot evaporate later even if the container becomes leaky, so that the environment is not polluted and also does not lead to any change in the operating properties.

The introduction of the mass results in additional heat bridges between the adjacent turns of the spirals 29, 27, and possibly 61 and 28. In addition, this mass results in additional heat storage capacity, which is advantageous in intermittent operation. The advantage of this is that the bypass line 138 according to Fig. 2 can be omitted or at least switched off, since the compressor then only produces as much refrigerant as is necessary to maintain a certain temperature or pressure for the refrigerant within the gas-refrigerant heat exchanger. With the design according to Fig. 9, freezing of condensate is completely ruled out using just one temperature sensor. Instead of several sensors, e.g. in Fig. 2 B. designated 131, 133, only a single temperature sensor 141 is sufficient here, which can be inserted into a metal tube 95 from below, which metal tube 95 is in turn soldered or welded to a metal cylinder 97 through which gas exiting at 99 flows and at the same time is embedded in thermal mass 100 and connected to a pipe carrying coolant. By appropriate shaping and by suitable heat transfer resistances it can be achieved that on the one hand the temperature of the gas from the coolant

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medium heat exchanger 10 is recorded at point 99, i.e. the actual current temperature of the gas, on the other hand for cases where there is no gas flow, i.e. when the system is idle, the temperature of the entire arrangement is nevertheless correctly determined by the temperature sensor 93, namely via the temperature of the thermal mass 100 or that of the coolant. In this way it is achieved that even when no compressed air is needed, i.e. when no gas flows past the sensor 93, no misleading display occurs.

It has already been pointed out that the shape of the newly developed gas-refrigerant heat exchanger is particularly suitable for modular construction. Fig. 8 shows an arrangement of two such modules 11 which are mounted on a common housing 87, whereby this housing can also be constructed from modular components of the same design, for example a cover plate 85, an identical base plate 86 and side parts 88 which can be screwed to it. This construction is shown in the second column of Fig. 13. In the column above only one module is used, in the column below there are four, and in the last column there are also four. By using modules of different output levels, see the designations A, B, C, D, and by combining such modules of different output levels in various ways, e.g. By multiplying the number of elements (e.g. 2B, 2C, 2D ₁ ) or by quadrupling, see 4B, 4C, 4D, or by combining 2 and 2 (2E, 2F, see last column), completely different performance values can be achieved in a modular manner.

The combination possibilities are very diverse, as the list in Fig. 14 shows that with the schematically shown configuration in the right column, for example,

.&bull;&bull;&lgr;"

J-U".

&bull; 4 X «

- 26 -

four different flow options are implemented. If two individual units are combined according to the second column, further performance levels are obtained, whereby, since two compressors are also provided here, the different performances can be achieved by switching them on and off as required.

In the last two columns, a parallel connection of two modules each, each of which is also supplied with a compressor, is provided, which allows further stages to be implemented.

The special shape of the housing, which can also include the housing for the other components of a compressed air dryer, see Fig. 10, makes it easier to assemble several units that can work independently of one another. It is also conceivable, see Fig. 11, to place a round upper part (housing 11 with connections 71, 72) on a drop-shaped device housing part 87, whereby such units can then easily be combined into assemblies, as shown in Fig. 12.

A connection block 106 for remote controls can be seen in Fig. 8 and is also shown schematically in Fig. 11. In the embodiment according to Fig. 12, cable ducts 104 are provided through which the corresponding connections can be passed.

This electronic external monitoring makes it possible to install the entire system in a control cabinet and monitor it from a central control room.

Another advantage is that the entire arrangement

does not have any boiler-like containers that require acceptance, so that no costly acceptance procedures (e.g. by the technical inspection association) are necessary.

Operating units with different requirements can be combined with one another. For example, a first module with a first compressor could enable operation with an operating pressure of 7 bar, with a dew point of 8°C. A second unit arranged next to it with its own compressor could be arranged for 12 bar operating pressure for the compressed air, with a dew point DTP of 2°C. On the other hand, due to the identical flow conditions (same pipe lengths, same pipe diameters >), devices with the same nominal value can also be connected in parallel in terms of flow without any problems and can be switched on or off using appropriate valves. If the required output is less than 50 % of the nominal output, for example, a pressure drop of less than 0.1 bar would occur, whereupon a valve could be closed using appropriate pressure control and automatic switching, so that only half the output would have to be used. If the requirements rise above 50 % and thus the pressure drop on just one device also increases, a switch could be made that puts a second parallel set of devices into operation and thus results in full nominal output.

The latter parallel connection of two devices also represents a safety control, since if one system fails, the other system is always available.

It is also possible to plan more economically, e.g. by initially purchasing only one unit, but as requirements increase, a second one is purchased, which can be easily operated in parallel.

- 28 can be switched.

Such combination options cannot be implemented with previously known systems due to the different flow resistances caused by the manufacturing technology, even with the same nominal power.

Claims (1)

drying.E PATENT ATTORNEY
D-4OOO DÜSSELDORF I · SCHADOWPLATZ 9 Dusseldorf, 27 May 1988 VIA Society for Process Engineering mbH Düsseldorf 11 Protection claims: Gas-refrigerant heat exchanger, in particular for compressed air dryers, consisting of a first pipe coil (12) for passing through gas (14) to be cooled, and a second pipe coil (16) for passing through refrigerant (18), the second pipe coil (16) being in direct heat transfer contact (20) with the first pipe coil (12) at least over a partial extent, characterized in that the first (12) and the second (16) pipe coils each have the shape of a truncated cone-like spiral (27, 29), each having the same spiral pitch (S) and are arranged one inside the other in such a way that essentially each spiral turn (31, 37; 35, 33) of one pipe coil (27 or 29) is surrounded by two adjacent spiral turns (35, 33 with respect to 31; 31, 37 with respect to 33) the other pipe coil along a line parallel to the pipe axis. Postal cheque, BEIiLiN west IBLZ I OÖ'lOÖ'lOl'f 32* 36"Yotf*- deutsche bank »BLZ 3OO7OOIO» 6I6O253 2. G^.s-refrigerant heat exchanger according to claim 1, characterized in that the cone-like, helical pipe coils (27, 29) are spatially arranged such that the truncated cone axis (47) is essentially vertical and the truncated cone end with the larger diameter is at the top. 3. Gas-refrigerant heat exchanger according to claim 1 or 2, characterized in that the pipe coil (29) for the refrigerant consists of pipe material with a smaller diameter than the pipe material for the pipe coil (27) for the gas to be cooled. 4. Gas-refrigerant heat exchanger according to one of claims 1 to 3, characterized in that the pipe coil (29) for the refrigerant (18) comprises two branches (29, 61), the first branch (61) forming a first truncated cone (61) arranged inside the truncated cone formed by the gas pipe coil (27) and the second branch (29) forming a truncated cone (29) arranged outside the truncated cone (27) of the gas pipe coil, such that essentially each spiral turn of the gas pipe coil (27) is touched by four adjacent spiral turns of the refrigerant pipe coil branches (29, 61) along lines parallel to the gas pipe axis. 5. Gas-refrigerant heat exchanger according to one of claims 2 to 4, characterized in that the upper end (12) of the gas coil (27) is connected to a gas supply connection (126) and the lower end (51) to a gas discharge connection, and that the lower end (57) of the refrigerant pipe (29) of the refrigerant tube (29, 61) is connected to a refrigerant supply connection (e.g. 130 in Fig. 2) and that the upper End (55) of the refrigerant pipe (29) or the refrigerant pipes (29, 61) are connected to a refrigerant discharge connection, and that if two refrigerant pipes (29, 61) are present, these are connected in parallel or in series (Fig. 9). Gas-refrigerant heat exchanger according to claim 5, characterized in that the pipe coil arrangement (27, 29; 61) is enclosed in a housing which is filled with a heat-transferring/heat-storing mass (1100). 7. Gas-refrigerant heat exchanger according to claim 6, characterized in that the housing (77) is liquid-tight and that the heat-transferring/heat-storing mass (100) is a liquid, such as brine or a water-glycol mixture. 8. Gas-refrigerant heat exchanger according to claim 6, characterized in that the housing (77) is essentially liquid-tight and that the heat-transferring/heat-storing mass is a liquid or a paste whose viscosity is high or which becomes high after being filled into the housing or which solidifies completely. 9. Gas-refrigerant heat exchanger according to claim 8, characterized in that the heat-transferring/heat-storing mass consists of coal dust or a similar powdery solid, which is bound to a paste by a liquid, such as brine. 10. Gas-refrigerant heat exchanger according to one of claims 6 to 9, characterized in that lower end of the housing (77) with the | passing gas (99) on the one hand and the heat transfer j &igr; load-bearing/heat-storing mass (100) on the other hand j j temperature sensor in thermal contact (93, 95) j , is provided. : j ! 11. Gas-refrigerant heat exchanger according to claim 10, j J «^characterized in that the temperature sensor ei>, ! J Sensor (93) insertable in a metal tube (95) J _/ and the metal tube (95) with a metal cylinder ■ ' or metal socket (97) welded or soldered | is that of the gas emerging from the gas coil! : Gas (99) is flowing through and in the heat transfer j load-bearing/heat-storing mass (100) embedded! ! is. ! , I ! 12. Gas-refrigerant heat exchanger according to one of the following j claims 4 to 10, "'characterized in that a &igr; upper part of the outer branch (29) of the cold j middle pipe is replaced by a gas pipe (28) i whose lower end (65) is connected to the lower end of the Gas pipe coil (27) of the gas-refrigerant-heat- \ &ngr; I exchanger (10) - if necessary with the interposition of an I Condensate separator and/or other gas treatment ' arrangement - and its upper end | (67) is connected to the gas discharge connection (127). | 13. Gas-refrigerant heat exchanger according to claim 12, j characterized in that the condensate separator and/or the other gas treatment arrangement within the tube coil cone formed
cavity is arranged. I 14. Gas-refrigerant heat exchanger according to claim 1, characterized in that a first frustoconical spiral arrangement and a second frustoconical spiral arrangement are inserted into one another. 15. Gas-refrigerant heat exchanger according to one of claims 1 to 14, characterized in that the gaps between adjacent tubes of the tube coil arrangement (27, 29, 61) are filled with metal (53) to form metal grooves. 16. Gas-refrigerant heat exchanger according to one of claims 1 to 15, characterized in that the heat exchanger is assigned a compressed air dryer which has a thermostat-controlled refrigerator (134) for compressing the refrigerant and a condensate separator (140). 17. Gas-refrigerant heat exchanger according to one of the claims
1 to 15, characterized in that the heat exchanger has the form of a module for the construction of compressed air dryers with graduated nominal output. 18. Gas-refrigerant heat exchanger according to claim 17, characterized in that two modules of the same size
are fluidly connected in parallel.