Heat exchanger

Abstract

A heat exchanger defined by a pair of concentrically arranged inner and outer tubes which define between them an annular flow passage for a product to be cooled or warmed. The outer tube includes a double walled section that defines a surrounding, annular chamber which extends over a major portion of the length of the outer tube. The outer tube ends include means for coupling the heat exchanger to a product pipe line so that the product can be cooled as it flows through the pipe line. A coolant intake port and a coolant outlet port are located adjacent ends of the inner tube and extend in a radial direction from the inner tube through the outer tube and the ports. The ports include means for connection to a coolant circulating system. Conduits are provided which permit a flow of the coolant from the inner tube to the annular chambers in the outer tube and from there back to the inner tube for discharge through the outlet port. Ends of the inner tube are shaped to minimize product turbulence and possible product damage and the inner tube further includes flow restricting means to assure the desired distribution of the coolant flow between the inner and the outer tubes.

Description

BACKGROUND OF THE INVENTION

Heat exchangers are well known and have a wide range of applicability. One particular type of heat exchanger is adapted for placement in a pipe line for the product to be heated or cooled (hereinafter "cooled," which means "heated or cooled"). U.S. Pat. No. 1,967,837 describes such a prior art heat exchanger.

Generally speaking, "in line" heat exchangers provide a product passage sandwiched between coolant passages. Normally, and as is described in the above-referenced U.S. Patent, the product passage is an annular passage disposed between concentric cylindrical inner and annular outer coolant passages. The product flows through intricate distribution channels and passages from the heat exchanger intake to the outlet around similarly intricate channels and passages which distribute the coolant from its intake to the inner and outer coolant chambers to the coolant outlet. The construction is complicated and, therefore, renders such heat exchanger expensive. Moreover, such heat exchangers exhibit significant resistance to the flow in the product pipe line and cause substantial product turbulence and agitation. For certain perishable products such as milk, for example, such agitation is highly undesirable because it can cause rancidity. Consequently, prior art in-line heat exchangers are generally unsatisfactory for economic reasons and in particular they are not well suited for use in applications in which the product to be cooled can be injured by turbulence and agitation.

In addition, the heretofore necessary intricate passageways to guide the product and the coolant around each other made it necessary to construct prior art in-line coolers of readily demountable parts so that they can be individually cleaned since the many corners, crevices and the like accumulate dirt, debris, and products that could not be simply washed off with a wash water flow through the heat exchanger. Such a construction greatly increases the bulk of the heat exchanger and further increases its initial cost. In addition, operating and maintenance costs increase because individual parts may and frequently do fail and since each cleaning of the line necessitates the disassembly of the heat exchanger, the cleaning of the individual parts, a reassembly of the parts and finally the reinstallation of the heat exchanger.

Thus, prior art in-line heat exchangers are cumbersome to operate and were frequently abandoned in favor of more conventional bulk cooling equipment. Bulk cooling equipment, however, is expensive and can become overloaded so that the product is not sufficiently cooled. It became therefore necessary to provide a second back-up system which is placed in operation if and when the need therefor arises. For expensive equipment such use is economically inefficient and undesirable.

SUMMARY OF THE INVENTION

The present invention provides an in-line heat exchanger which is simple and, therefore, inexpensive to construct. It is of a unitary construction in which all parts are permanently secured, e.g., welded to each other, and it provides a flow passage for the product to be cooled that is virtually unobstructed and which affords a smooth continuation of the product flow in the pipe line. Consequently, the heat exchanger of the present invention can be cleaned with the pipe line by passing therethrough a suitable cleaning fluid, e.g. water. There is no need for removing the heat exchanger, tediously disassembling it, cleaning it and thereafter reinstalling it as was necessary with prior art in-line heat exchangers.

In its broadest aspects the present invention provides a jacketed outer tube that is connectable to a product pipe line and which has a smooth inner wall that forms a continuation of the pipe line. An inner tube of lesser diameter than the outer tube wall is concentrically disposed within the outer tube. Radially oriented inlet and outlet ports extend through the outer tube directly into the inner tube to flow a heat exchange medium, hereinafter sometimes referred to as "coolant" directly into the inner tube. A pair of conduits provide a flow passage from the inner tube to the annular coolant jacket of the outer tube so that coolant can be circulated through the inlet to the inner tube, from there the flow is separated into a first portion along the inner tube and the second portion into the outer jacket and the outer jacket flow is returned to the inner tube for the discharge of all coolant through the outlet port.

The ports and conduits between the inner tube and the outer jacket are all radially arranged and face in the same radial direction. In this manner a minimal obstruction of the product flow is obtained and the product passage is virtually unobstructed and free of tortuous passages, hidden crevices, and the like, which so frequently trap debris and which are almost impossible to clean unless direct access to them can be provided.

All components of the heat exchanger of the present invention are constructed of a readily cleanable material, e.g. stainless steel, and they are permanently secured, e.g. welded together. This greatly reduces manufacturing costs since it eliminates expensive machining of parts that must closely fit so that seals can be obtained between the demountable parts. Moreover, since no machining and no tight tolerances need to be met by the components of the heat exchanger of the present invention, they can be constructed of readily formed, thin walled material. This reduces the weight and material consumption and greatly enhances the efficiency with which heat is transferred between the product and the cooler, thereby rendering the heat exchanger of the present invention more effective than the prior art devices since the latter require heavier wall thicknesses to establish and maintain the necessary dimensional tolerances.

In addition, the heat exchanger of the present invention is readily installed in a product pipe line and need not be removed for cleaning the pipe line since it is automatically cleaned each time the pipe line is washed.

The lightweight construction of the heat exchanger, its constant inside diameter and its outer diameter which is only insignificantly larger than the diameter of the pipe line make it possible to install it in an existing pipe line without the need for additional support or hanging equipment.

Thus, the unit can be employed as an efficient, low cost back-up system for existing bulk coolers for the product. Furthermore, the smooth product flow passage through the heat exchanger minimizes product agitation and turbulence. Thus, it is ideally suited for handling products such as milk which cannot be subjected to excessive agitation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective elevational view, in section and with parts broken away illustrating the heat exchanger of the present invention;

FIG. 2 is an enlarged end view, in section, and is taken on line 2--2 of FIG. 1;

FIG. 3 is a view similar to FIG. 2 but is taken on line 3--3 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, a heat exchanger 2 such as a cooling unit for milk in a milk processing plant generally comprises an elongate outer tube having a smooth, cylindrical inner wall 6 and terminating in end flanges 8 that are constructed so that they can be coupled to a standard pipe fitting for installation of the unit in a milk pipe line, for example. The outer tube has a diameter only slightly larger than the diameter of the pipe line in which it is installed. An inner tube 10 is concentrically disposed within and has a slightly lesser length than the outer tube. Ends 12 of the inner tube are closed and the inner tube has a diameter less than that of wall 6 of the outer tube to define an annular flow passage 14 for the product, e.g. milk, to be cooled.

The inner tube is cylindrical and includes an intake port 16, which extends radially away from the tube adjacent one end thereof and which is defined by tubular member 18 provided with an internal pipe thread 20. An outlet port 22 is adjacent the other end of inner tube 10 and is defined by another tubular member 18 provided with an internal pipe thread 20 which also extends radially away from the inner tube and which is further longitudinally aligned with the intake port; in other words, both ports extend in the same radial direction for purposes more fully set forth hereinafter.

Outer tube 4 includes a casing 24 that extends over a major portion of the length of the tube, which ties into inner wall 6 adjacent flanges 8 to define an annular jacket 26 which surrounds the annular product flow passage 14. Two slanted cylindrical tubular conduits 28 communicate the jacket with interior space 30 of inner tube 10. Slanted tubes are disposed between and to adjacent inlet and outlet ports 16, 22 and they face in the same radial direction as the port tubes 18 so that the ports and the slanted tubes are in mutual alignment in the product flow direction. It will be observed that tubes 18 and conduits 28 define the sole connections between the inner and the outer tubes and mount the tubes to each other. Additional mounting of structure over and above the necessary coolant conduit, which would only obstruct the product flow passages are not necessary.

To assure an adequate coolant flow from interior space 30 to the annular jacket 26 a flow restrictor 32 is provided. The flow restrictor is defined by a disc 34 that has an outline slightly less than the cross-section of inner space as is best seen in FIG. 3. The disc is positioned just upstream (in the flow direction of coolant) of the upstream slanted tube 28 and has approximately the same inclination to the axis of the heat exchanger as the tube. The bottom portion of the disc (as seen in FIG. 1) terminates in or is mounted to a tab 36 made of resilient material such as spring steel so that an increase in the coolant flow rate correspondingly increases the force the coolant applies to the disc and thereby forces the disc in a downward direction, (clockwise as viewed in FIG. 1) to open the remaining flow passage and interior space 10 and thus facilitate the ready and even passage of coolant without undue pressure build-ups and the like. If desired the backside of the disc can be provided with a suitable brace to limit the maximum extent to which the disc can be pivoted downwardly.

Although tube end 12 can be constructed of flat end plates to assure low cost they are preferably dished to define convex end surfaces 38. Such end surfaces facilitate the product flow and help reduce flow turbulence and agitation.

As already briefly referred to, all components of heat exchanger 2 are permanently attached to each other by welding, brazing or the like. Consequently, the various members such as outer tube 4 including inner wall 6, casing 24, inner tube 10, in and outlet ports 16, 22 and slanted tubes 28 can be constructed of thin walled tubular members of deformed sheet metal. Close manufacturing tolerances are not required since none of the surfaces require close tolerance sealing fits. Where seals are required, the parts are welded or brazed together. At other points of the heat exchanger slight variations in the dimensions do not affect its operation. Accordingly, the heat exchanger of the present invention can be constructed with little or no machining and of lightweight wall sections to enhance its efficiency.

Turning now to the operation of the heat exchanger of the present invention, it is installed in product pipe line e.g. milk pipe line in which fresh, still warm milk is transferred to a holding and cooling tank. End flanges 8 of outer tube 4 are engaged with matching couplers at the ends of the pipe line and the couplers are tightened. Intake and outlet port 16, 22 are connected to a coolant circulating system 40. In the milk cooling example the circulating system might be a fresh water supply. Alternatively, ice water or a conventional coolant such as freon may be passed through heat exchanger 2. In the latter instance suitable expansion valves and reduced diameter conduits for the ports and the slanted tubes are provided. When milk begins to flow it enters the heat exchanger adjacent one end and continues essentially unidirectionally, and opposite to the coolant flow to and through annular flow passage 14 for discharge from the heat exchanger at the other end thereof. At no time is the milk required to change its flow direction so that it is subjected to virtually no agitation. The ports and the tubes connecting the inner tube with the outer annual cooling jacket are aligned in the direction of the milk flow to minimize their respective flow resistances and flow turbulences caused thereby.

After the pipe line is shut down it is cleaned by flowing therethrough suitable cleansing solutions and cleansing water. The same water completely cleanses all surfaces of heat exchanger 2 coming into contact with the milk. The surfaces are smooth and there are no hidden passages, crevices and the like in which debris and/or milk particles cannot be cleansed away by the flow of wash water. Consequently, the heretofore necessary removal of the heat exchanger, disassembly, cleaning and reinstallation is eliminated.

Claims

I claim:

1. A heat exchanger for fluid food products comprising an outer tube having an inner diameter and a concentric inner tube having an outer diameter less than the inner diameter to define an annular product flow space between the two tubes, the outer tube including at its ends means for coupling it to a product pipe line and having an outer diameter only insignificantly larger than the pipe line diameter, the outer tube further including means defining an annular, concentric coolant flow space surrounding the product flow space and extending over a portion of the total length of the outer tube, radially oriented coolant inlet and outlet ports defined by hollow cylindrical members connected to the inner tube, extending to the exterior of the outer tube, and communicating an interior of the inner tube with the exterior of the outer tube, each member including an interior thread extending from the outer end of the member towards the other end thereof for threadably connecting the members to a coolant circulating system, and generally radially disposed, cylindrical coolant passages disposed upstream and downstream of the inlet and outlet ports, respectively, for flowing a portion of the coolant from the inner tube to the annular space in the outer tube and back to the inner tube before discharge from the heat exchanger through the outlet port.

2. A heat exchanger for perishable liquid food product comprising a first outer tube having a cylindrical inner wall and ends adapted to be connected to a pipe line for the product for flowing the product through the tube, the outer tube including means defining an annular coolant flow space surrounding the cylindrical inner wall of the tube, a second cylindrical inner tube having a lesser diameter than the diameter of the inner wall and being concentrically disposed within the outer tube to define a continuous, annular flow passage for the product between the inner and the outer tubes, first radially extending conduits adjacent and spaced from ends of the inner tube extending from the inner tube through the outer tube for communicating an interior space of the inner tube with the exterior for circulating a fluid coolant through the inner tube, a second radially oriented conduit adjacent each first conduit communicating the inner space of the first tube with the annular coolant space of the outer tube to define a coolant flow passage from the inner tube to the annular space in the outer tube and back to the inner tube, and means in the inner tube positioned adjacent the second conduit proximate the inlet port for restricting the coolant flow therein and facilitating the diversion of a portion of the coolant flow to the annular coolant space in the outer tube, the flow restricting means including means directing a portion of the coolant flow in the inner tube towards such second conduit.

3. A heat exchanger according to claim 2 wherein the flow restricting means comprises a disc-shaped member disposed within the inner tube and having an outline less than a cross-section of the tube, and including means resiliently positioning the disc adjacent the proximate second conduit generally transversely with respect to the length of the inner tube.