US3381746A

US3381746A - Vapor condensing apparatus

Info

Publication number: US3381746A
Application number: US602252A
Authority: US
Inventors: Karl H Wiegmann; John H Leary
Original assignee: Hull Corp
Current assignee: Hull Corp
Priority date: 1966-12-16
Filing date: 1966-12-16
Publication date: 1968-05-07
Anticipated expiration: 1985-05-07
Also published as: GB1162737A

Description

y 1968 K. H. WIEGMANN ET AL 3,381,746

VAPOR CONDENSING APPARATUS Filed Dec. 16, 1966 8e- 46 Fi .2. I

Karl HJ Viegmcnn John H. Lecr'z r INVENTORS AM. a

ABTRAT BF THE DISCLOSURE A vapor condenser having a hollow housing adapted to be evacuated to sub-atmospheric pressure and in which a tubular refrigerated condenser unit is spaced from the housing periphery and forms with the latter inner and outer chambers which communicate with each other at the front end of the housing. A vapor inlet communicates the inner chamber at the rear end of the housing with a source of vapor to be condensed, and a vapor outlet communicates the outer chamber, also at the rear end of the housing, with a source of sub-atmospheric pressure. Thus, vapors are caused to pass along the condenser unit from the inlet to the outlet in a countercurrent flow path.

Background of the invention This invention relates to vapor condensers, and more particularly to a highly eflicient vapor condenser for use with high vacuum freeze drying apparatus.

Vapor condensers heretofore have employed an elongated rectangular housing containing a multiplicity of transversely spaced, rectilinear refrigerated plates extending parallel to the uni-directional flow of vapor through the housing. Baflles sometimes are arranged between the plates to direct the vapor over the plates in the most efficient manner.

This prior arrangement limits the housing to a rectangular shape which is expensive to fabricate to sufficient strength to withstand the required sub-atmospheric pressures. Moreover, the arrangement of spaced rectilinear plates tends to build up ice layers adjacent the vapor inlet to such an extent as to bridge and close the spaces between plates. This blocks the flow of vapor to the rest of the plate surfaces, increasing the pressure drop from inlet to outlet and correspondingly reducing the efliciency of the condenser. Still further, defrosting of ice from the plates involves excessive non-productive time, and drainage of water from the rectangular housing is ineflicient. The rectangular design of the housing also requires excessive space to accommodate a given surface area on the condenser plates.

Summary of the invention The present invention achieves the principal objective of overcoming the disadvantages enumerated heretofore, by a condenser construction which provides a countercurrent flow of vapor from a central inlet first over the inner surface of a tubular refrigerated condenser unit and then in the opposite direction along the outer surface of the condenser unit to an outlet, thereby insuring maximum extraction of condensables from the vapor.

Specifically, the tubular construction of the refrigerated condenser unit achieves the objective of providing maximum condensing surface area, with uniform ice distribution, in a housing which occupies a minimum of space.

The concentric arrangement of the vapor inlet, condenser unit and housing also exposes the entire length of the apparatus to view through a sight glass in the housing, thereby affording thorough inspection and assuring the maintenance of most etlicient operating conditions.

The concentric construction also minimizes manufacturing cost, allows the apparatus to be mounted vertically States Patent or horizontally, and provices maximum eificiency of defrosting and drainage.

The foregoing and other objectives and advantages of the present invention will appear from the following detailed description taken in connection with the accompanying drawings of the preferred embodiment.

Brief description of the drawings FIG. 1 is a view in longitudinal section of vapor condensing apparatus embodying the features of the present invention, the arrows indicating the direction of vapor flow.

FIG. 2 is a sectional view taken on the line 2-2 in FIG. 1, the arrows indicating the direction of flow of refrigerant fluid through the sections of the condenser unit.

FIG. 3 is a plan view of one of the sections of the condenser unit.

FIG. 4 is a sectional view taken on the line 44 in FIG. 3.

Description of the preferred embodiment Referring to the drawing, the vapor condensing apparatus includes a hollow housing defined by the peripheral wall 10, the rear end wall 12 and the front wall 14.

The housing is shown mounted in horizontal position by means of longitudinally and laterally spaced legs 16, the lower ends of which are supported upon a foundation.

In the embodiment illustrated, the front wall comprises a door the peripheral flange 18 of which is mounted pivotally on the peripheral flange 20 at the front end of the housing wall 10, by means of the hinge 22. An annular resilient gasket 24 is secured to the flange of the door for abutment against the flange 20 to provide a vacuum tight seal. A plurality of bolts 26 extend through aligned openings in the flanges for securing the door releasably in closed position. A central window 28 in the door affords visual inspection of the interior of the housing.

The hollow housing contains an elongated tubular condenser unit 30 spaced inwardly from the peripheral wall 10 of the housing. In the preferred embodiment illustrated, the condenser unit is formed of a plurality of longitudinally extending sections 30, there being four such sections shown. As best seen in FIGS. 3 and 4, each section comprises a pair of plates 32 within the margins of which are stamped or otherwise impressed on their inner sides a serpentine channel. The plates are welded together about their margains with the serpentine channels registering with each other, thereby forming a continuous passageway 34 between the open ends which communicate with the projecting tubing couplings 36. One of these couplings functions by connection with a length of tubing 38 (FIG. 1) to admit refrigerant fluid from a source (not shown) to the passageway, while the other coupling serves, by connection with another length of tubing 40, to return the circulated fluid to the source.

The condenser unit sections are joined together along their longitudinal margins to form the tubular construction illustrated. The margins of the upper and lower sections are overlapped and connected together by such means as the bolts 42. The front end of the unit is supported within the housing by such means as the upper and lower brackets illustrated. The upper bracket 44 is secured at one end to the housing and at the opposite end to the overlapping side edges of the condenser unit sections.

The lower bracket assembly includes the base bracket 46 which supports the spaced connector brackets 48. These are secured one to each of the adjacent margins of the lower sections. The narrow space between these mar- 6 gins facilitates defrosting of the condenser unit without impairing its function of providing countercurrent vapor flow described hereinafter.

The rear end of the condenser unit is spaced slightly from the rear wall 12 of the housing on which it is supported by the inwardly projecting lugs 50 and interposed heat insulating spacers 52. It will be understood that heat insulating spacers also are interposed between the condenser sections and the

front brackets

44 and 48 to prevent transfer of cold temperature from the condenser unit to the housing.

The front end of the condenser unit is open and terminates inwardly of the front wall 14 of the housing. The housing and condenser unit thus cooperate to form inner and

outer chambers

54 and 56, respectively, which communicate with each other at the front end, for purposes explained in detail hereinafter.

The four inlet tubiugs 33 connect to a common header 58, the inlet pipe 60 of which extends through the housing wall and is fitted at its outer end with a flange 62 by which to connect a feed line from a circulating source of refrigerant fluid (not shown). The return tubings 4t: similarly connect to a common header 64 the return pipe 66 of which extends through the housing wall and is fitted at its outer end with a flange 68 by which to connect a return line to the source of refrigerant fluid.

Extending through the rear wall 12 of the housing and communicating with the inner chamber 54 within the condenser unit is a vapor inlet conduit 7%. This conduit is sealed to the housing wall, as by welding, and its outer end is provided with a peripheral flange 72 by which to connect a vapor infeed line leading from a source (not shown) of vapor to be condensed.

Although the vapor condensing apparatus of the present invention may be utilized for a variety of purposes, it has particular utility in association with apparatus for freeze drying foodstuffs and pharmaceuticals. Essentially, this involves the removal of water remaining in a frozen substance by changing the ice crystals to vapor without allowing the ice to melt.

This process of sublimation occurs at sub-atmospheric pressures. Accordingly, the condenser housing is provided with a vacuum outlet conduit 74 having a flange 76 at its outer end for connection to a vacuum line leading from a vacuum pump (not shown). This outlet conduit communicates with the outer chamber 56 defined between the housing and condenser unit, and is positioned adjacent the rear wall 12 of the housing. In this manner vapors to be condensed enter the inner chamber 54 adjacent the rear wall of the housing and thus are caused to pass along the inner surface of the condenser unit to the forward open end of the latter, and thence rearward through the outer chamber 56 and along the outer surface of the condenser unit to the outlet conduit 74, as illustrated by the arrows in FIG. 1. This counter current flow of vapor results in the latter being subjected to the freezing temperature of the entire inner and outer surfaces of the condenser unit, thereby insuring maximum extraction of condensables from the vapor with only the non-condensables being exhausted to the vacuum pump.

It is important that the condensables be caused to build up on the inner and outer surfaces of the condenser unit in a substantially uniform ice layer throughout the entire length of the unit. This insures against blockage of vapor flow, as is inherent in the plate type condenser constructions of the prior art, and assures maximum operating efficiency of the apparatus.

Maximum degree of uniformity of build-up of the ice layer along the length of the condenser unit is achieved, in the preferred embodiment illustrated, by the provision of a vapor distributor. This consists of an elongated tube 78 which communicates at its open rear end with the vapor inlet conduit 70 and which extends forwardly therefrom in inwardly spaced relation to the condenser unit. The portion of the distributor tube within the condenser unit is perforate, as indicated by the multiplicity of relatively large openings 80. The vapor to be condensed passes outward through these openings into the space of the inner chamber 54 between the distributor tube and the condenser unit. The vapors thus are distributed substantially uniformly over the inner surface of the condenser unit. The front end of the distributor tube may be open, as illustrated, or it may be closed by an end wall if desired.

In the embodiment illustrated, the distributor tube 73 is supported at its rear end by fitting over the inwardly extending portion of the vapor inlet conduit 70, and its front end is supported by means of the brackets 82 connecting the brackets which support the front end of a condenser unit.

A plurality of conduits are provided through the housing wall it). One or more of these may be used to introduce hot water or steam into the housing for melting ice collected on the condenser unit. The melted ice and water are drained out the bottom of the housing through the valve controlled drain pipe 86. Others of the conduits may contain sealed therrno-couples for measuring the temperature of the condenser unit, While still others may contain sealed vacuum measuring leads for measuring the sub-atmospheric pressure in the apparatus.

in the operation of the vapor condensing apparatus of the present invention, the vapor infeed conduit 70 is connected to freeze drying or other apparatus providing vapor which is to be condensed. The outlet conduit 74 is connected to a vacuum pump by which to reduce the pressure within the condenser housing and freeze drying or other apparatus to the required sub-atmospheric ressure. The outlet of a circulating source of refrigerant fluid is connected to the inlet pipe 60, and the return pipe 66 is connected to the return side of the refrigerant source to provide a continuous circulation of refrigerant fluid through the passageways 34 in the sections of the condenser unit.

Vapors to be condensed thus are drawn through the infeed conduit and the openings of the distributor tube. The vapors pass through the inner chamber 54 uniformly along the entire length of the inner surface of the condenser unit forwardly around the open front end of the latter and thence rearwardly through the outer chamber and along the entire length of the outer surface of the condenser unit. condensables in the vapor thus are deposited uniformly over the entire inner and outer surfaces of the condenser unit, and non-condensables (air, etc.) are carried through the outlet conduit 74 to the vacuum pump.

During the condensing operation visual inspection of the interior of the condensing apparatus may be made through the sight glass 28 provided in the door. When the layer of ice collected on the condenser unit reaches a predetermined maximum, above which the efficiency of the apparatus is adversely affected, the pressure in the housing is broken back to atmospheric, and hot water or steam is introduced through one of more conduits 84 in the housing, to melt the ice on the condenser unit. The melted ice and water are drained out the bottom of the housing through the valve controlled drain pipe 86.

It will be apparent to those skilled in the art that various changes may be made in the size, shape and arrangement of parts described hereinbefore. For example, although the concentric, circular cross sectional configuration of the housing, condenser unit and distributor tube is preferred for its simplicity, economy, rugged construction and high efficiency of condensing and defrosting, it may be of rectangular or other cross sectional configuration if desired. Further, although the apparatus is shown mounted in a horizontal position, it may be mounted vertically or at intermediate angles. The tubular condenser unit may be constructed in various ways other than the sectional arrangement illustrated. These and other modifications may be made, as desired, without departing from the spirit of this invention and the scope of the appended claims.

Having now described our invention and the manner in which it may be used, what we claim as new and desire to secure by Letters Patent is:

1. Vapor condensing apparatus, comprising (a) a hollow housing having a peripheral wall and front and rear walls and adapted to be evacuated to sub-atmospheric pressure,

(b) a tubular condenser unit in the housing spaced inwardly from the peripheral wall thereof, the rear end of the condenser unit being positioned closely adjacent the rear end of the housing, the front end of the condenser unit being open and terminating inwardly of the front end wall of the housing, whereby the condenser unit defines with the housing inner and outer chambers communicating with each other at the front end of the housing,

(c) the condenser unit having passageway means therein for the circulation of refrigerant fluid,

(d) refrigerant inlet and outlet conduit means connected at one end to the condenser unit passageway means and extending through the housing for connection to a circulating source of refrigerant fluid,

(e) outlet conduit means adjacent the rear wall of the housing communicating with the outer chamber and adapted for connection to a source of vacuum,

(f) a tubular vapor inlet extending inwardly through the rear wall of the housing and communicating with the inner chamber, the outer end of the vapor inlet being adapted for connection to a source of vapor to be condensed, and

(g) the vapor inlet including distribution means for distributing vapors to be condensed substantially uniformly along the inner surface of the condenser unit.

2. The apparatus of claim 1 wherein the distribution means comprises an elongated tubular vapor distributor spaced inwardly from and extending a substantial distance into the inner chamber, the portion of the distributor within the inner chamber being perforate for passage of vapor outwardly therefrom into the space between the distributor and condenser unit.

3. The apparatus of claim 1 wherein the peripheral wall of the housing, the tubular condenser unit and the tubular vapor inlet are circular in cross section.

4. The apparatus of claim 1 wherein the condenser unit comprises a plurality of interconnected longitudinal sections each having passageway means therein.

5. The apparatus of claim wherein the longitudinal sections are of arcuate cross sections and are interconnected at their longitudinal margins forming a condenser unit of substantially circular cross section.

6. The apparatus of claim 1 wherein the condenser unit comprises a plurality of interconnected longitudinal sections each having passageway means therein, and the refrigerant inlet and outlet conduit means comprises a plurality of inlet and outlet conduits one of each connected at one end to one of the passageway means and the opposite end being connected to inlet and outlet header means, respectively, the header means being adapted for connection to a circulating source of refrigerant iiuid.

7. The apparatus of claim 1 wherein the front wall of the housing comprises a door mounted on the housing for removably closing the front end of the latter.

3. The apparatus of claim 1 wherein the front wall of the housing includes a transparent window for viewing the interior of the apparatus.

9. The apparatus of claim 1 including liquid defrost drain conduit means in the housing.

References Cited UNITED STATES PATENTS 2,358,940 9/1944 Schoeller 165l55 2,372,079 3/1945 Gunter 165-155 X 2,626,130 1/1953 Raskin 165-469 X 2,870,997 1/1959 Soderstrom l-155 X ROBERT A. OLEARY, Primary Examiner.

A. W. DAVIS, Assistant Examiner.