Equipment for drying gas, in particular air, by refrigeration

Abstract

The disclosed equipment provides for the flow of gas to be dried in a vertically downward direction through a precooling gas/gas heat exchanger and then in a vertically downward direction through a removable insert refrigerant cooling coil configuration of a gas/refrigerant heat exchanger for cooling. A filter removes impurities in the cooled gas extracted from the lower portion of the gas/refrigerant heat exchanger before it is recirculated through a removable insert pipe arrangement of the gas/gas heat exchanger. Such recirculation enables the cooled gas to precool newly admitted gas within the gas/gas heat exchanger. It also increases the temperature of the cooled gas by a prescribed magnitude before it is exhausted from the gas/gas heat exchanger for functional use.

Description

BACKGROUND OF THE INVENTION

This invention relates to equipment for drying gas, such as air, by refrigeration and particularly to an equipment arrangement in which a gas to be dried flows successively through a gas/gas heat exchanger, a gas/refrigerant exchanger and subsequently again the gas/gas heat exchanger in a continuous loop.

As is known, the principle of drying gas by refrigeration is based upon the fact that the dew point of the gas to be dried is lowered so that humidity contained in the gas is separated, along with at least a portion of further impurities. Heretofore, in prior art devices for drying gas by refrigeration the two heat exchanger columns are positioned in a horizontal direction so that due to the use of two different kinds of heat exchangers a satisfactory efficiency is achieved, however, as a result of the horizontal extension of the columns difficulties are encountered with regard to an efficient concentrated withdrawal of the separated humidity or impurities, respectively, as well as with regard to a suitable guidance of the gas or refrigerant flow because the force of gravity does not act upon the gas or refrigerant flow in the flow direction but rather in a direction transverse thereto.

It is known in the prior art to provide a device for separating humidity from wet gases or vapors wherein the gas flow to be cooled or refrigerated is guided through two cooling chambers in a vertical direction. Both chambers are connected in series and cooled by a common coolant flow. The gas to be cooled is passed through the first cooling chamber in a downward direction whereas it passes the second cooling chamber in an upward direction. Thus, the separated liquid, under the influence of the force of gravity, travels to the lower end of the cooling chambers from where the liquid may be readily withdrawn. However, the two prior art cooling chambers both are designed as gas/refrigerant heat exchangers whereas a gas/gas heat exchanger is not present so that the overall efficiency is kept at a relatively low level.

Another known device differs from the above-described prior art merely insofar as both cooling chambers are not disposed beside each other but one above the other so that substantially the same functional operations occur except for the considerably larger height of construction which in many cases may even be excessive.

It is an object of the present invention to improve such prior art devices for achieving both an efficient withdrawal of the condensate along with a suitable conduct of the gas and refrigerant flow and simultaneously a good efficiency with respect to the cooling of the gas to be dried.

SUMMARY OF THE INVENTION

The foregoing and other objects are achieved by an equipment arrangement which advantageously positions both a gas/gas heat exchanger and a gas/refrigerant heat exchanger in vertical direction adjacent each other.

Due to such a structure and configuration of the device according to this invention the desired goal is reached, namely, that the height of the construction is low and the condensate accumulates in a concentrated area with the assistance of the force of gravity and, moreover, that the entire device exhibits a high cooling efficiency due to the refeeding of the gas cooled within the gas/refrigerant heat exchanger into the gas/gas heat exchanger.

In accordance with the illustrative embodiment of this invention, a gas to be dried is processed vertically downward from an upper inlet to a lower outlet through a heat exchanger insert of a gas/gas heat exchanger device. The latter insert includes a plurality of pipes aligned vertically one above the other and in the downward path of the gas to be dried. Each of the pipes illustratively comprises a hollow inner portion extending longitudinally and in a horizontal plane with the insert. Each of the pipes supports cooling fins, or ribs, for cooling gas including the gas from the inlet. Advantageously, the hollow portion of selected ones of the pipes communicate with another inlet of the gas/gas heat exchanger for recirculating gas cooled by a gas/refrigerant heat exchanger through the gas/gas heat exchanger for precooling newly admitted gas to be dried and for upward against the force of gravity exhausting the cooled, or dried, gas to the exterior of the gas/gas heat exchanger for function use.

A gas/refrigerant heat exchanger is used for further cooling of gas received from the lower outlet of the gas/gas heat exchanger and then coupling the cooled gas through an impurities and separated liquid filter to the hollow portion of the pipes in the gas/gas heat exchanger. The gas/refrigerant heat exchanger also comprises an insert comprising a cooling coil network arrangement disposed in a vertically downward path of the gas flow from the gas/gas heat exchanger via an upper inlet and a lower outlet of the gas/refrigerant heat exchanger. The latter outlet is coupled to the filter for communicating the cooled gas thereto for removal of impurities.

In summary, the present invention provides for the flow of a gas to be dried in a vertically downward direction through a precooling gas/gas heat exchanger and thence in a vertically downward direction through a refrigerant cooling coil configurations of a gas/refrigerant heat exchanger for cooling. The processing continues by communicating the cooled gas through a filter for impurity removal and then by recirculating the purified cooled gas through a pipe arrangement of the gas/gas heat exchanger. Such recirculation enables the cooled gas to precool newly admitted gas within the gas/gas heat exchanger and thereby to increase the temperature of the cooled gas by a prescribed magnitude before it is exhausted from the gas/gas heat exchanger for functional use.

DESCRIPTION OF THE DRAWING

The foregoing objects, features and advantages, as well as others of this invention, may become more clearly understood by a reading of the following description of an exemplary embodiment thereof as shown in the accompanying drawing in which:

FIG. 1 is a side view, partially in section, of a device for drying gas by refrigeration;

FIG. 2 is a horizontal cross-section through the gas/gas heat exchanger of FIG. 1, taken along line II--II;

FIG. 3 is a horizontal cross-section through the refrigerant/gas heat exchanger of FIG. 1 taken along line III--III;

FIG. 4 is a side view, partially in section, of an insert for the refrigerant/gas heat exchanger according to another embodiment of the invention; and

FIG. 5 is a vertical section through the insert of FIG. 4 taken along line V--V.

DETAILED DESCRIPTION

Referring now to FIG. 1, there is illustrated a refrigerating dryer 10 according to one embodiment of this invention having a vertically extending gas/gas heat exchanger 12 as well as a gas/refrigerant heat exchanger 14 extending in parallel thereto.

The gas/gas heat exchanger 12 includes a cylindrical housing 16 enclosing a heat exchanger insert 18 of rectangular cross-section. Collars 20 are secured to the outer circumference of the insert 18 by means of which the insert 18 rests upon brackets 22 fastened to the interior surface of housing 16. As apparent in particular from FIG. 2, pipes 24 supporting cooling ribs 26 extend between two opposite sides of the insert 18 parallel above and besides each other.

At the upper end of the gas/gas heat exchanger 12 there is a stud-like inlet 28 through which the gas to be dried, preferably air, may enter. This gas is passed through the insert 18 in the direction indicated by arrow m, thereby flowing through the hollow spaces defined between pipes 24 and cooling ribs 26, respectively. From the lower end of the insert 18, the gas to be dried is passed on to a studlike outlet 30 through which it may escape from the gas/gas heat exchanger 12 as indicated with the S-shaped dashed line leading from outlet 30 to a subsequent inlet 40 of the gas/refrigerant heat exchanger 14.

Cooled gas as derived from the gas/refrigerant heat exchanger 14--the structure of which is explained in greater detail hereafter--is refed via a stud-like inlet 32 into the gas/gas heat exchanger 12 whereupon it enters the opposite free openings of pipes 24. The collar 20 adjacent inlet 32 prevents gas entering through inlet 32 from being applied to the whole group of pipes 24 simultaneously. Rather, merely those pipes 24 extending below the collar 20 adjacent inlet 32 are available to receive gas. Through this lower portion of pipes 24 the gas travels to the right side of the insert 18, in order to rise there to a maximum height determined by the collar 20 located at this side of insert 18, and to enter further pipes (not shown) corresponding to pipes 24 so that the gas flow is conducted through pipes 24 in an S-like configuration. The open ends of the upper pipes 24 communicate with a stud-like outlet 34 through which the dried gas may leave the refrigerating dryer 10. In the described embodiment according to FIG. 1, the gas flow is deviated twice, however, principally any other higher number of deviations may take place.

Gas/refrigerant heat exchanger 14 includes a heat exchanger insert 36 enclosed by a housing 38. Through the stud-like inlet 40 the gas supplied from gas/gas heat exchanger 12 may enter into the gas/refrigerant heat exchanger 14 in order to leave same upon passage of the heat exchanger insert 36 through a stud-like outlet 42 communicating with the inlet 32 of gas/gas heat exchanger 12.

A cooling coil generally designated 44 and having linear tube-like sections 46 is distributed over the entire height and width of insert 36 (cf. FIG. 3). Sections 46 traverse insert 36 in a similar manner as pipes 24 intersect insert 18, except that at their ends they are connected to subsequent sections 46 through U-connections 48, respectively. To increase the cooling action, the sections 46 may be surrounded by cooling ribs 50 as is conventional in the art. The beginning of cooling coil 54 communicates with an injection conduit 52 whereas the end of cooling coil 44 terminates in an exhaust conduit 54 so that the coolant may be pumped through cooling coil 44 in a continuous closed loop.

Between outlet 42 and inlet 32 a filter 56 may be interconnected which then advantageously is located at the coolest point of the gas flow to be dried and which thus may intercept separated liquid and impurities in a particularly effective manner.

The bottoms of the two heat exchangers may be provided with outlets 57 and 58, respectively, through which the liquid separated from the gas flow may be readily withdrawn as under the influence of the force of gravity it accumulates in the bottom area of the two heat exchangers and thus concentrates close to the two outlets 57 and 58, respectively.

Accordingly, the refrigerant dryer 10 according to this invention provides for a suitable withdrawal of the separated impurities and for a suitable course of the gas flow because it will always descend from warmer to cooler points and rises from cooler to warmer points, respectively. It also simultaneously guarantees good efficiency inasmuch as the cooled gas rising within the gas/gas heat exchanger 12 pre-cools the gas descending through insert 18 in direction of arrow m while the gas returning to outlet 34 through pipes 24 is pre-heated by the descending gas flow thus having resumed a desired relatively high temperature level when exiting through outlet 34. In practice, the temperature distribution may be such that the entering gas is at a temperature of 35.degree. C, whereas it leaves gas/gas heat exchanger 12 at a temperature of about 20.degree. C. Upon travel through insert 36 the gas flow may be at a temperature level of +2.degree. C and that temperature may have been increased up to +25.degree. C when the gas leaves gas/gas heat exchanger 12.

FIG. 4 shows a particularly advantageous embodiment of a heat exchanger insert of this invention having a structure differing from that of heat exchanger insert 36 of FIG. 1. This insert likewise exhibits a case 60 receiving cooling coil elements 62, 64 . . . of substantially slice-like configuration and having cooling coil sections 66, 68 . . . . At their lower ends the individual slice-like cooling coil elements 62, 64 rest upon supports 70. At their ends, cooling coil elements 62, 64 terminate into U-bows 72 by means of which they communicate with a manifold 74 connecting cooling coil elements 62, 64 in parallel.

As evident from FIG. 4, each slice-like cooling coil element 62, 64 comprises a plurality of cooling coil sections 66, 68 bent backwards and forwards in S-shaped configuration and extending in parallel with each other in horizontal direction. As indicated by the dash-dotted zig-zag-lines of FIG. 5 (upper area), cooling coil sections 66, 68 . . . --with reference to the cross-section of a slice-like cooling coil element--are bent backwards and forwards in a zig-zag-like manner from a first plane 78, 82 . . . into a corresponding second plane 80, 84 . . . and vice versa, so that each slice-like cooling coil element 62, 64 . . . has a zig-zag-like configuration with regard to its cross-section.

Cooling coil elements 62, 64 . . . adjacent each other may thus be interlaced with each other in a comb-like manner, so that a maximum filling factor for the volume is secured and immediately adjacent sections 66, 68 . . . of neighboring cooling coil elements 62, 64 . . . may support each other mutually, thereby providing for a high mechanical stability of the entire cooling coil system. The mutual association of the sections of the cooling coil elements or of the cooling coil elements themselves is clearly illustrated in the lower portion of FIG. 5.

It will thus be possible to bend the individual cooling coil elements 62, 64 . . . from one coherent tube so that it will be unnecessary to use separate additional connecting members at the points of return as this had been set forth in connection with FIG. 3. As will be understood that this kind of construction will yield a material cost saving because soldering or brazing operations are not required any more. Beyond that, reliability will be increased because leakages due to imperfact soldering work are impossible. Moreover it is warranted that the individual cooling coil elements do not exhibit any regions in which the refrigerant would have to flow in an upward direction. This avoids that impurities contained in the refrigerant such as oil which might separate in the course of the passage of the refrigerant through the cooling coil elements might settle within the cooling coil system. Rather, as the sections 66, 68 . . . are continuously extending in a downward direction throughout any danger of a possible accumulation of impurities within a cooling coil element is removed. While refrigerants are available for which the occurrence of oil or other residues do not necessarily have an adverse effect, such refrigerants exhibit but a comparatively low cooling capacity.

While almost any hollow spaces between adjacent sections bent in a zig-zag-like manner and belonging to one cooling coil element are filled by corresponding neighboring sections, free hollow spaces remain between adjacent sections of the two outer cooling coil elements through which the gas to be dried might flow without sufficiently intensive contact with the cooling coil system.

Therefore, into at least a part of these hollow spaces baffles 86 may project which extend substantially over the entire length of sections 66, 68 and are fastened to the adjacent wall of case 60. These baffles 86 assure a close contact of the gas current with the cooling coil elements in the area of the outer hollow spaces, too.

In order to further enhance the rigidity of the system formed by cooling coil elements 62, 64, contiguous sections of adjacent cooling coil elements may be connected with each other for example by brazing, in particular in the point of return area. Similarly, the outer cooling coil elements may be affixed to case 60.

The refrigerating dryer according to this invention may be used for quantities on an order of magnitude of 3,000 m.sup.3. The three major components of the refrigerating dryer, namely the gas/gas heat exchanger, the gas/refrigerant heat exchanger and the heat exchanger insert may be designed as modules which may be composed due to the prevailing operation conditions with regard to the amount of gas (air) to be conveyed and the desired temperatures, or which may be replaced by suitable larger or smaller similar modules when there is a change in the operation conditions .

Claims

What is claimed is:

1. In an apparatus for drying gas, in particular air, by refrigeration, including a gas/gas heat exchange and a gas/refrigerant heat exchanger, said exchangers extending with their longitudinal axes in a vertical direction, a heat exchanger insert for at least said gas/refrigerant exchanger, said heat exchanger insert comprising a plurality of cooling coil elements being connected in parallel and combined into a closed package and having a plurality of cooling coil sections being bent in their longitudinal direction backwards and forwards in an S-like configuration and extending in a horizontal direction substantially in parallel, said sections further alternating with regard to the cross-section of a cooling coil element in a zig-zag manner between a first and a second plane, adjacent cooling coil elements meshing with each other so that immediately neighboring sections of adjacent cooling coil elements provide for a mutual support.

2. An apparatus as defined in claim 1 wherein said immediately neighboring sections of adjacent ones of said cooling coil elements are rigidly connected with each other.

3. An apparatus as defined in claim 2 wherein baffles are accommodated in free hollow spaces between neighboring sections of said cooling coil elements positioned at the outer sides of said cooling coil package, said baffles extending substantially over the entire length of a cooling coil section.

4. An apparatus as defined in claim 3 wherein any of said heat exchangers is equipped with a heat exchanger insert and wherein said gas/gas heat exchanger, said gas/refrigerant heat exchanger and/or said heat exchanger insert each are constructed as modules replaceable independently of each other.