US2622414A

US2622414A - N ven tor

Info

Publication number: US2622414A
Authority: US
Publication date: 1952-12-23
Anticipated expiration: 1969-12-23

Description

.Dec. 23, 1952 F. JAUBERT APPARATUS FOR COOLING AND DEHYDRATING AIR Filed July 31, 1947 5 Sheets-Sheet l r m. a z Z Z V A NM M 4| m & ,7 J R E m z m a Q Afi/ Q \k \lu \\M U "A W Sq Dec. 23, 1952 G. F. JAUBERT APPARATUS FOR COOLING AND DEHYDRATING AIR File d'July 31, 1947 3 Shqets-Sheet 5 Patented Dec. 23, 1952 OFFICE APPARATUS FOR COOLING AND DEHYDRATING AIR Georges Francois Jaubert, Paris, France Application July 31, 1947, Serial No. 764,946 In France December 18, 1939 4 Claims.

My invention relates to' processes and corresponding devices, intended for producing large quantities of cold air.

When desiring to secure a more or less intensive production of cold air, one generally draws the air from the atmosphere and sends it onto a cluster of pipes within which is circulated a brine or salt solution, cooled by means of an ice' machine, the refrigeration then resulting from both the conductibility and the convection.

Sometimes one attempts to increase the intensity of the cold thus obtained by evaporating, within the cluster of pipes, a suitable refrigerant, such as, for instance, anhydrous liquid ammonia, liquid carbonic acid, etc. obtained generally remains unsatisfactory, due to the fact that, on the one hand the cluster of refrigerating pipes quickly covers itself with frost which reduces its thermic conductibility, while,

on the other hand the installations using that process are so bulky that they do not afford the possibility of treating large quantities of air. Moreover, the degree of cooling of the air by means of the process under consideration is fixed and cannot be varied. It is, once for all, determined only by the nature of the refrigerant used, and it does not give the possibility of obtaining quick variations (still less instantaneous variations) of the degree of refrigeration of the air.

The process described herein has for an object to eliminate those drawbacks: It consists essentially in first compressing the air intended for refrigeration, and then drying it and furthermore expanding it, the importance of the expansion varying with the degree of cold to be obtained: thus is realised an economical, and practically instantaneous production of large quantities of cold air, the refrigeration of which can be obtained with the simultaneous performance of an external work and a corresponding recovery of energy: a circumstance which brings down the production cost of that cold air. I

My invention thus results in an economical production of cold air, at'very low temperature. According to the tests which I have made the cooling of wet air consumesan amount ofenergy far more considerable than does; the cooling of dry air. If one desires, for instance, to bring down to C. the temperature of one cubic meter of air taken at C. in the state of-saturation and containing, for instance, 25jgr. of water vapor, the calories needed amount to 22.707, of which only are utilized for the refrigeration of air, while 79% are consumed for the refrigera- The efliciency thus tion of the water and its elimination in the form of frost.

A calculation shows that the refrigeration of dry air taken at 25 C. down to 0 C. necessitates the use of only 5.5 calories per kilogram, while the refrigeration of water vapor, between the same limits of 25 C. and 0 C. necessitates the use of 690 calories per kilogram, i. e. 125 times more than for the air. The appended drawings illustrate schematically a form of my invention, taken as an instance, of an installation intended for economically producing large quantities of cold air:

Fig. 1 is a general diagram of the installation,

Fig. 2 schematically represents a sectional view of a drying apparatus given as an instance,

Fig. 3 and 4 schematically represent improved forms of the installation shown in Fig. 1.

Fig. 5 is a plane view corresponding to the Fig. 4.

The installation comprises a compressor I (Fig 1), of the rotary type for instance, coupled for instance with an appropriate electric motor 2. That compressor sucks the air directly from the atmosphere, preferably through a dust filter, and it compresses that air, through a piping 3, into a suitable cooler 4 provided with a draining device and connected with a drying apparatus, composed for instance of two reservoirs 5 and 6 containing a suitable material for damp absorption (said material being preferably regenerable in situ), such as, for instance, the

product which is known by bagel.

The reservoirs 5 and 6 are connected by a common pipe 1, from which is started a pipe 8, extended, through a cooler l5,.to an expansion turbine 9, preferably keyed onto the shaft of the electric motor 2. The exhaust pipe ID of the turbine 9 is connected to the apparatus intended for the utilization. of the cold air. i

As my process aims at producing, before all, very large amounts of cold air at as. low aco'st as possible, and as the only real expensesinvolved reside in those resulting from the air compression, it is indispensable to compress it only to the least possible extent: for instance by only 2 or 3 effective kg. per cm?, so as to obtain a temperature of at the exhaust. :I therefore take care of avoiding all unnecessary compression, and I consequently eliminate all 1305-- sibilities of any losses of pressure head in the piping as well "as in-the drying iapparatus,'be' cause :an eifective loss of pressure. head amounting to only 0.5 kg. to 11kg. per cm. would conthe name of Carsiderably influence the ratio of the pressures before and after the expansion, with the result that the production of cold would fall down accordingly.

In consideration of the large volume of air undergoing treatment, as well as of the almost :absolute degree of desiccation which is desired, before the expansion takes place, it is necessary to develop the surface of the dehydrator, and to use the absorbent material in the form of small grains. If those grains were simply thrown into high drying towers (of some 5 or meters height for instance), they would oppose a very high resistance to the flow of air.

Consequently, the general information on the above described installation should be completed by some data re: the inside dispositions of the drying apparatus which have been designed in order to reduce the loss of pressure head.

For that purpose, each one of the generators 5 and 6 containing the damp absorbent (Garbagel for instance) comprises, as shown in Fig. 2, an envelope l6 containing, within its walls, a stack made by the piling up of several sections or rings [1, l8 concentric to the envelope, the said sections having their walls provided with a large number of holes and containing the absorbent material, such as Carbagel.

The central section of the stack 18 (Fig. 2), is connected to the pipe 29 bringing the air to the drying apparatus. The head 2! which closes the upper extremity of the envelope I6 is set at a proper distance of the drying stack, 50 that a space is left therein, between the stack and the head, for a chamber 22 wherefrom starts the outlet pipe 23.

Because of that disposition, the wet air which enters the central section of the stack IS flows from that stack through the many holes of its walls, and, after having run through the filling of carbagel, escapes through the wall 17, similarly perforated, for gathering on the chamber 22. That disposition results in a suitable dehydration of the air, while it opposes only a relatively low resistance to its circulation.

The dehydration battery 56 preferably includes :a device intended for the regeneration of the carbagel contained within; it may offer any suitable disposition, and comprise an inlet air pipe H running across the. regenerating heater l2 which can be connected to the one or the other of the reservoirs 5 and 5, or to both of them (Fig. 1). The said reservoirs comprise exhaust pipes shown in I3 and [4 (Fig.1) and each one of those capacities can be isolated from the all compressed inlet pipe 3 and from the pipe 8 leading to the expansion turbine 9.

From the compressor l the air is at first led, through the pipe 3, to the cooler 4 which cools it down approximately to the ambient temperature; afterwards it is sent across the one or the other of the drying reservoirs 5, 6, in which the air abandons the water it contains. Once it has been brought back to the ambient temperature in the cooler l5, the air is sent to the expansion turbine 9, wherefrom it comes out at very low temperature before being sent to the utilization apparatus. As the air expands in the turbine 9, it produces therein a useful work, which can, for instance, be utilized for running the compressor I: in which case the electric motor 2 is called upon to supply only the necessary complement of power eventually needed.

Thus is obtained, at the outlet pipe 10 of the turbine 9, refrigerated air, the degree of cooling of which can be modified at any time, simply by varying the air pressure before its expansion, or the exhaust pressure, which may be lower than the atmospheric pressure. Indeed the greater is the ratio between the inlet pressure and the outlet pressure, and the colder is the air leaving the apparatus.

For obtaining :a higher degree of cold it is possible, after having dried all the air, to send part of it to a supercompressor of any suitable type which gives it an excess of pressure; and after having brought down that fraction of air to the ambient temperature, to expand it in a piston motor with performance of external work, the expansion in that case coming nearer the pure adiabatic expansion than would do the expansion in a turbine.

Thus can be obtained dry and very cold air, which is afterwards mixed with the remainin fraction of the air which has been compressed only once. Thus it is easy to obtain the total possible range of cold, while operating on large volumes of air. Drying under pressure releases a proportion of the heat contained in the wet air, so that this air under pressure is warmer when leaving the drying apparatus than when entering it: it generally reaches the turbine at a temperature of +25 C., a condition which may beundesirable when very cold air must be ob tained at the exhaust of the turbine.

To obviate that inconvenience, it is possible to use another characteristic of the invention, according to which the air is first cooled, for instance down. to 0 or a lower temperature, before entering the expansion turbine, by means for instance of an ordinary ice machine (ammoniac, or sulfurous gas or carbonic acid machine, etc.) The efliciency and the yield in cold air are so much improved when doing so, that they largely compensate not only for the acquisition and operation costs of the supplementary material, but also for the excess time necessary for putting in service the ice machine.

In the same line of progress my invention involves an improved process, which consists in directly or indirectly effecting a heat exchange between a part or the totality of the air leaving the expansion turbine and the totality or a fraction of the air entering the said turbine, in order to refrigerate and to dry the compressed and to dry it, partially or totally, before it enters the turbine, with eventually no use of external chemical means or devices, thus securing a simplification of the system in which the refrigeration precedes the expansion.

In carrying out the said process, I lead the totality or a part only of the cold air leaving the turbine into a heat exchanger (tubular exchanger or indirect acting air cooler, brine cooler or direct action cold accumulator), wherein it abandons its cold, either directly (tubular exchanger, cold aocumulator), to the whole or to a part only of the air under pressure which is going to enter the turbine, either indirectly through the intermediary of a brine air cooler, i. e. by means of an unoongealable brine which will have the same effect as the exchanger just mentioned or as a cold accumulator of a Known type.

That portion of the air thus expanded, but a little reheated while passing through the exchanger, is mixed, in principle, with the rest flows towards the utilization.

As it is plain, the direct acting exchanger, or

the indirect action brine air cooler, or else the cold accumulator, are simply inserted in by-pass on the path of the exhaust cold air flowing towards its place of utilization.

For regulating the degree of intensity of that preliminary refrigeration, it is possible to act either on the air presure when admitted into the turbine (i. e. on the air compressor), or on the degree of the vacuum at the exhaust of the turbine, or on both factors at the same time. It is also possible to act on the amount of cold air which is by-passed by the exchanger.

From an economical point of view, the latter system offers the advantag to eliminate the ice machine, and this compensates largely for the supplementary work imposed on the compressor in order to maintain, at the turbine exhaust, a determined and rather low temperature (of the order of 50 to 75 under zero).

The gain in efficiency resulting from that refrigeration effected prior to the expansion, results also from the fact that the compressed air thus cooled looses in the exchanger an important part of the water that it can still contain: and that permits to use only preliminary chemical air .dryers of small importance instead of the very large apparatus utilized till now and which have been described above.

Fig. 3 illustrates a form of my invention and an instance of an installation based on the last mentioned process. Acompressor 2| for instance, of the rotary type, is keyed on the shaft of a motor 22, for instance electrical. That com pressor sucks the air directly from the atmosphere through its piping 23, and discharge the compressed air through its pipe 24, its cooler 25 and the pipe 21 in a cooler 29. That air, once it has been cooled in the cooler 26, is brought back by the pipe 28, through an air dryer 29, into an expansion turbine 39, preferably keyed on the other end of the shaft of the electric motor 22. After having passed through the turbine, the air. is led by a pipe 3| to the apparatus in which it'will be utilized; and on the pipe is preferably disposed a valve 32, around which a bypass communicates, by means of a valve 36, with a coil placed in a brine air cooler 34. The said air cooler communicates with the heat exchanger 26 through a pipe 38 in a closed cycle in which is inserted a brine circulating pump 33. At the base of the tube coil through which the air is circulated, in the cooler 26, is installed a draining valve 39.

Innormal operation, the valve 32 is closed and the valve 36 open; the air leaving the turbine 39 through the pipe 3| is sent through the pipe 35 and the open valve 36 into the brine refrigerator 34, where it releases a part of its low temperature to the brine circulated by the pump 33 and the pipe 38 in the cooler 29. The whole of the air delivered by the compressor 2| into the cooler 26, through the pipe 21, is thus cooled by the effect of the said brine, and it releases a part of the condensed vapor it contained herein; this latteraccumulates, in the form of liquid water, at the base of the cooler 26, wherefrom it can be from time to time drained by means of the draining valve 39. That air is then suitably dried by the air dryer 29 before it arrives to the expansion turbine 30.

My invention provides for the improvement of the above described processes, by the use of thermo-regenerable dehydrants, which make it possible to obtain, according to my observations, a degree of desiccation, which becomes more pronounced, as the temperature at which the drying operation is carried out decreases and even at temperatures lower than 0 C.

The process thus improved consists, on the one hand: in using two drying devices, one working at the ambient temperature, and the other at a temperature of the order of 0 or even under 0; on the other hand, in utilizing, for the regeneration of the regenerable dehydrant, the heat developed by the compression of the air, so as to make use of all the possibilities offered by the process and to render it as economical as possible.

The two Figures 4 and 5, the corresponding components of which have been given the same reference numbers, illustrate schematically an arrangement of a plant carried out according to the above process: Fig. 4 shows a complete elevation view of such an installation, and Fig. 5 shows a simplified plan of the same.

When leaving the compressor which is a part of the compressor-motor-turbine group numbered 4|, the air under pressure, heated by the compression work, passes through a tubular exchanger 43, which is a cooler and a recuperator, wherein the air gives up its calories to the regenerative air needed for the reactivation of the regenerable dehydrant, the so-called regenerative air being sucked in the outside atmosphere and blown into the exchanger 43 by the blower 50.

If the temperature of the regenerative air would not suffice for securing a complete reactivation of the dehydrant used (for instance if the compressor should compress only at too small a pressure), an electric heater 5|, similar to the heater mentioned with regard to Fig. 1, supplies the balance of calories. The heating resistance can, moreover, be provided with means for several rates of heating, in order to be able, by itself alone and with the help of the blower 50, to assure the complete reactivation of the dehydrant utilised when the turbo-compressor is at rest.

When leaving the exchanger 43, which recuperates the heat of the compression, the compressed air passes through a tubular cooler 44, supplied with cold water, then in a drainer-condenser-oil separator 45, of a known type, and finally through the main dryer 46, which contains the regenerable dehydrant (carbagel, silicagel, alumina etc.) working at the ambient temperature.

When leaving the air dryer 49, the air is already almost completely desiccated, but it has been slightly heated; it is then passed through a tubular cooler 41, supplied also by cold water, wherefrom the air exhausts at a temperature of about 15 C.

The compressed air then enters a heat exchanger 48, in which it is cooled to a temperature lower than 0 C., generally between -5 C. and 10 C., by exchange of heat with very cold air coming from the exhaust of the expansion machine T of the group 4|, machine which may be, for instance, of the turbine type, the sliding vane type, or the piston type. After leaving the exchanger 49. the cooled compressed air is led to a second drier 49, in which it is further dried, and which it leaves substantially completely dry to enter a pipe 60, connecting the drier 49 to the inlet of the expansion machine T. Another pipe 52 connects the drier 49 to the heater 5| intended for the regeneration.

The substantially completely dry air entering the expansion machine T expands therein, and temperature becomes very low of the order of C. for instance. The exhaust from, the

expansion machine is connected to an utility line U, directly through a valve 62, and indirectly through a valve 54, the cooling line of the exchanger 43, and a valve or cook 55. Such an arrangement permits of obtaining very cold and dry air, in a short time after the starting of the installation, and of rapidly regulating the temperature of this air.

On setting the installation going, the valve 42 is closed, the valve 54 is open, and the cock 55 is positioned so as to make the line 56 communicate with the pipe 57 with direct exhaust into the atmosphere; under these conditions the entire cold air produced by the expansion turbine T is used to cool the compressed air coming from the cooler 51, in such a way that the air which is led to the admission or" the expansion turbine is rapidly cooled and that, consequently, the air furnished by this turbine rapidly reaches the desired low temperature, for example 80 degree C. The valve 52 is then opened and the cook 55 is positioned so as to make the line 56 communicate with the appliance U. The temperature of the appliance air is regulated by manipulation of the valves 42 and Fa l, and cook 55; the lowest temperature is obtained when the cock'55 evacuates into the pipe and when only the air coming from the valve 22 is used.

In another form of embodiment, there is no second drier 49, and the cooled compressed air leaving the exchanger 58 is directly brought to the pipe 69, and led therethrough to the inlet of the expansion machine T.

An installation as the one of Figs. 4 and 5 applies easily to the production of rapid and even instantaneous variations of the temperature of the dry and cold air sent towards the utilization U, by means of a quadruple regulation, bearing on the following elements: (1) regulation of the pressure of the compressed air operating the expansion motor; (2) regulation of the pressure in the exhaust pipe of the expansion motor, by lowering the said pressure to a value even inferior, if necessary, to the atmospheric pressure; (3) regulation of the mixture, in definite amounts, of the very dry and cold air (80 to 100 C.) which leaves the expansion motor, with the expanded air similarly dry, but by far not so cold, which leaves the return of the counter-flow exchanger, which latter receives the whole or a part of the exhaust from the expansion motor, and which serves to cool the compressed air supplying the 2nd dryer; at last: (4) regulation of a mixture made of the air specially dried, by whatever means but not necessarily cooled, with very cold air leaving the expansion motor.

What I claim is:

1. An installation for the conversion of large quantities of starting or atmospheric air into very dry gaseous air at temperatures rapidly regulable between the limits of neg. 50 and neg. 100 deg. C., comprising a compressor for converting the starting air into compressed air, means for first cooling the compressed air for converting the compressed air into compressed air cooled to a temperature of the order of the temperature of the starting air, means for drying by a dehydrating agent regeneratable by heat for converting the said cooled compressed air into substantially completely dry air, means for eifecting a second cooling of substantially completely dry air, including a heat exchanger for converting the said substantially completely dry air into cold dry air at a temperature of at least neg. deg. C., an expansion machine for converting the said cold dry air into very cold dry air at a temperature of the order of neg. 50 to neg. deg. C., an utility line to receive a part of said very cold dry air and deliver said very dry gaseous air, means for deriving another portion of said very cold dry air and circulating the said very cold dry air through said heat exchanger to coact with said second cooling means and convey it to said utility line, and means for regulating the magnitude of said quantities of air whereby said very dry gaseous air is brought to the desired temperature.

2. An installation for the conversion of large quantities of starting or atmospheric air into very dry gaseous air at temperatures rapidly regulable between the limits of neg. 50 and neg 100 deg. C., comprising a compressor for converting the starting air into compressed air, means for first cooling the compressed air for converting the compressed air intocompressed air cooled to a temperature of the order of the temperature of the starting air, means for drying by a dehydrating agent regeneratable by heat for converting the said cooled compressed air into substantially completely dry air, means for effecting a second cooling of said completely dry air, including a heat exchanger with a cooling line for converting the said substantially completely dry air into cold dry air at a temperature of at least neg. 10 deg. C., an expansion machine for converting the said cold dry air into very cold dry air at a tem perature of the order, of neg. 50 to neg. 100 deg. C., and means for connecting the exhaust from said expansion machine to an utility line, last said means including a direct connection through a regulable valve and an indirect connection successively through a second regulable valve, the cooling line of said heat exchanger, and a third valve.

3. An installation for the conversion of large quantities of starting or atmospheric air into very dry gaseous air at temperatures rapidly regulable between the limits of neg. 50 and neg. 100 deg. C., comprising a compressor for converting the starting air into compressed air, means for first coolin the compressed air for converting the compressed air into compressed air cooled to a temperature of the order of the temperature of the starting air, means for drying by a dehydrating agent regeneratable by heat for converting the said cooled compressed air into dehydrated compressed air, means for effecting a second cooling of said dehydrated compressed air, including a heat exchanger for converting the said dehydrated compressed air into cold dry air at a temperature of at least neg. 10 deg. C., means for effecting a second drying by a dehydrating agent regeneratable by heat for converting the said cold dry air into substantially completely dry air, an expansion machine for converting the said substantially completely dry air into very cold dry air at a temperature of the order of neg. 50 to neg. 100 deg. C., an utility line to receive a part of said very cold dry air and deliver said very dry air, means for deriving another part of said very cold dry air and circulating the said derived air through said heat exchanger to coact with said second cooling, and deliver it to said utility line, and means for regulating the magnitude of said parts whereby said very dry air is brought to the desired temperature.

4. An installation for the conversion of large quantities of starting or atmospheric air into very dry gaseous air at temperatures rapidly regulable 9 between the limits of neg. 50 and neg. 100 deg. C., comprising a compressor for converting the starting air into compressed air, means for eflecting a first cooling the compressed air for converting the compressed air into compressed cooled air to a temperature of the order of the temperature of the starting air, means for drying by a dehydrating agent regeneratable by heat for converting the said cooled compressed air into dehydrated compressed air, means for effecting a second cooling of the dehydrated compressed air including a heat exchanger with a cooling line for converting the said dehydrated compressed air into cold dry air at a temperature of at least neg. 10 deg. C., means for effecting a second drying of the cold dry air by a dehydrating agent regeneratable by heat for converting the said cold dry air into substantially completely dry air, an expansion machine for converting the said substantially completely dry air into very cold dry air at a temperature of the order of neg. 50 to neg. 100 deg. C., and means for connecting the exhaust from said expansion machine to an utility line, last said means including a di- .10 rect connection through a regulable valve and an indirect connection successively through a second regulable valve, the cooling line of said heat exchanger, and a third valve.

GEORGES FRANQOIS JAUBERT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS