U.S. patent number 3,889,746 [Application Number 05/425,025] was granted by the patent office on 1975-06-17 for heat exchanger.
Invention is credited to Ernest Laffranchi.
United States Patent |
3,889,746 |
Laffranchi |
June 17, 1975 |
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.
Inventors: |
Laffranchi; Ernest (Ferndale,
CA) |
Family
ID: |
23684833 |
Appl.
No.: |
05/425,025 |
Filed: |
December 14, 1973 |
Current U.S.
Class: |
165/155 |
Current CPC
Class: |
F28D
7/103 (20130101); F28D 2021/0042 (20130101) |
Current International
Class: |
F28D
7/10 (20060101); F28d 007/10 () |
Field of
Search: |
;165/154,155,156,141,66 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Sukalo; Charles
Attorney, Agent or Firm: Townsend and Townsend
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.
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.
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