Note: Descriptions are shown in the official language in which they were submitted.
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HEAT EXCHANGE APPARATUS UTILIZING
THERMAL SIPHON PIPES
~ACKGROUND OF THE INVENTION
This application is a division of Canadian Serial No.
2~1,447, filed June 27, 1977.
This invention relates to a heat exchanger and, more
particularly, to a heat exchanger utilizing a plurality of
thermal siphon pipes which contain a heat exchange fluid for
removing heat from a hot fluid, such as steam.
In electrical power generation systems, the spent steam
from a steam turbine is normally passed to a once-through con-
denser in which feedwater is passed in a heat exchange relation-
ship with the steam to condense the steam. However, in view of
the substantial water consumption and thermal pollution in-
volved, these types of condensers are becoming less and less
desirable.
As a result, various types of dry hea-t exchangers have
been suggested which, in their basic form, utilize pressurized
air to condense the steam. However, these dry condensers are
~0 considerably more expensive than the water condensers discussed
above because of the fan power required and the high cost of the
heat exchanger portion of the condenser. Also, the dry con-
densers have poorer cooling potential than the water condensers.
A third form of heat exchanger that is possible in these
types of environments is the so-called heat pipe heat exchanger
which utilize a plurality of horizontally extending pipes, closed
at each end and having wicking material formed on their interior
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~urface. A heat exchange fluid is disposed in the pipes and is
vaporized by the heat of the steam which is passed over a portion
of the pipes, and air or the like is passed over the other
portions of the pipes to condense the heat e~change flui~. How-
ever, these types of arrangements are unpractical in a large
system since the wicking material is expensive, the pipes are
difficult and costly to manufacture, and the pipes are restricted
to use in a horizontal position.
SU~ RY OF THE INVENTION
It is therefore an object of the present invention to
provide a heat exchange apparatus which is air cooled and which
can be manufactured at a relatively low cost.
It is a further object of the present invention to
provide a heat exchange apparatus of the above type which mini-
mizes the need of excessive fan power and the use of heat pipes
requiring internal wicking material.
It is a further object of the present invention to
provide a heat exchange apparatus of the above type which
employs a plurality of gravity controlled, thermal siphon pipes
constructed and arranged in a unique manner.
Toward the fulfillment of these and other objects, the
heat exchange apparatus of the present invention comprises an
upper heat exchange section, a lower heat exchange section, a
plurality of thermal siphon pipes each having an upper portion
extending in the lower heat exchange section, each of the pipes
being closed at each end and con-taining a heat exchange fluid,
means for passing a hot fluid across the lower portions of the
pipes to transfer heat from the hot fluid to the heat exchange
fluid, and means for passing a cool fluid across the upper
portion of the pipes to remove heat from the heat exchange fluid.
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Thus broadly, the invention contemplates a heat exchanger
for exchanging heat energy from a relatively hot fluid to a
relatively cooler fluid which comprises a heat exchanger housing
defined by top, bottom, and sidewalls, a partition dividing the
interior of the housing into an upper portion and a lower portion,
a plurality of thermal siphon pipes extending through the par-
tition with their respective evaporator sections located in the
lower portion and their respective condenser sections located in
the upper portion, a plurality of panels internal to the upper
portion dividing the upper portion into a plurality of heat
transfer compartments and adjacent cooling fluid plenums with
the compartments substantially enclosing the upper portions of
some of the thermal siphon pipes and with the panel dividing
each compartment from its respective plenum provided with at
least one inlet opening to permit the passage of a cooling fluid
from the plenum into the compartment. Each compartment is
provided with an outlet to exhaust the cooling fluid after it
has passed over the condenser section of the thermal siphon
pipes, and a ~eans introduces a flow of cooling fluid into each
of the plenums and through the inlet opening to cool the con-
denser sections of the heat pipes.
BRIEF DESCRIPTION OF THE DRAWINGS
The above brief description, as well as further objects,
features, and advantages, of the present invention will be more
fully appreciated by reference to the following detailed
description of a presently preferred but nonetheless illus-
trative embodiment in accordance with the present invention,
when taken in connection with the accompanying drawings wherein:
FIG. 1 is a schematic elevational view depicting a
portion of a power generation system utilizing the heat exchange
apparatus of the present invention;
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FIG. 2 is an enlarged vertical, cross-sectional view
depicting one embodiment of the heat exchange apparatus of the
present invention;
FIG. 3 is an enlarged partial view of a portion of the
condenser section of FIG. 2, appearing with FIG. l;
FIG. 4 is an enlarged perspective view of another
embodiment of the heat exchange apparatus of the present
invention; and
FIGS. 5 and 6 are cross-sectional views taken along the
lines 5-5 and 6-6, respectively, of FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The heat exchange apparatus of the present invention will
be described, for the purposes of example, in connection with an
electrical power generator plant, in which the heat exchange
apparatus is utilized to condense spent steam from a turbine.
Referring specifically to FIG. 1, the reference r.umeral 10
refers in general to a steam turbine having an inlet line 12 for
introducing steam from an external source into the turbine, and
two outlet lines 14 and 16 for discharging the spent steam after
20 it has passed through the turbine. The turbine operates in a ;~,
conventional manner to drive an electrical generator 18 for
generating electrical power, also in a conventional manner.
Four condenser sections 20, 22, 24, and 26 surround the
turbine 10, with the sections 20 and 22 extending to one side
of the turbine and the sections 24 and 26 extending to the other
side thereof. The sections 20 and 22 receive spent steam from
the line 14 and the sections 24 and 26 receive spent steam from
the line 16.
One embod:iment of a condenser section 22 is depicted in
detail in FIGS. 2 and 3, it ~eing understood that the remaining
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sections 20, 24 and 26 can be constructed in an identical
manner. In particular, the section 22 includes a housing 30
which is divided into an upper portion 32 and a lower portion
34 by a horizontally extending partition 36. An inlet opening
38 is provided at one end portion of the lower housing portion
34 for receiving steam from the ste~m line 14, for treatment
in a manner to be described later.
A plurality of vertical partitions 40 are provided in
a spaced relationship in the upper housing portion 32, with the
end partitions 40 forming the walls of the housing. A
plurality of perforated vertical partitions 42 are also pro-
vided in the upper housing portion 32 and extend between
adjacent partitions 40. Each partition 42 divides the area
between adjacent partitions 40 into an air passage 44 and a
heat exchange compartment 46.
A plurality of thermal siphon pipes 50 are provided in
the housing 30 with the upper portion of each pipe extending in
a compartment 46, and with the lower portion of each pipe
extending in the lower housing portion 34. The pipes 50 are
disposed in three parallel rows in each compartment 46, with
the end pipes of each row being depicted. It is understood
that the number of pipes 50 in each row can vary according to
particular design requirements. A plurality of heat exchange
fins 51 extend over the upper portions of the pipes 50 in the
compartments 46, and the lower portion of each of -the pipes 50
extends at an angle relative -to the upper portion thereof, for
reasons that will be described in detail later. Each pipe 50 is
closed at its ends and contains a heat exchange fluid, such as
ammonia, which is vapori2ed in the portion of the pipe extending
in the lower housing portion 34 and is condensed in the portion
of the pipe extending in the compartment 46, as will be de-
scribed in detail later.
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A fan 52 is disposed in the upper portion of each air
passage 44 and operates to draw ambient air into the passage 44
in a generally downwardly direction as viewed in FIGS. 2 and 3.
A baffle 54 is provided in each air passage 44 to direct a
portion of the air into the lower portion of the passage. The
air then passes through the perforations in the partitions 42
in a general right-to-left direction and across the upper
portions of the pipes 50 in the heat exchange compartments 46.
A plurality of vent pipes 56 extend through the upper wall of
the housing 30 for receiving the air after it has passed through
the compartments 46 after which the air is discharged through a
wind vane 58 mounted at the upper end of each of the vent pipes
56.
As shown in FIG. 2, an additional air vent pipe 60 is
associated with two of the compartments 46 and operates to pass
a portion of the air exiting from the latter compartments into
a collection duct 62. The collection duct 62 is utilized to
recirculate the relatively warm air to the boiler (not shown)
associated with the steam turbine 10 to supply the combustion
air of the boiler. As better shown in FIG. 3, the passage of
air through the vent pipes 56 and 60 associated with the latter
two compartments 46 can be selectively controlled by means of
manually operated damper valves 64 disposed in each pipe in
accordance with the particular combustion air requirements of
the boiler. It is understood that the number of compartments
46 having an additional air vent pipe 60 can be varied as needed.
Referring again to FIG. 1, a pair of condensed steam
lines 70 and 72 connect the outlet end of the lower housing
portions 34 of the condenser sections 22 and 24, respectively,
30 to a pump 78; and lines 74 and 76 connect the lower housing
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portions of the condenser sections 20 and 26, respec-tively, to
a pump S0. The pumps 78 and 80 operate to draw the condensed
steam from the condenser sections 20, 22, 24, and 26 and pump
it to a collection tank (not shown), or the like, for further
treatment.
In operation, the steam is discharged from the turbine
10 through the lines 14 and 16 to thle condenser sections 20, 22,
24, and 26 where it passes into and through the lower housing
portion 34 of each section and across the lower portions of the
pipes 50. The heat from the steam is transferred to the heat
exchange fluid in the pipes 50 whereupon the steam condenses
and the heat exchange fluid vaporizes and rises to the upper
portions of the pipes 50 located in the compartments 46. The
fans 52 force relatively cool ambient air into the air passages
44, through the perforated partitions 42, and across the upper
portions of the pipes 50 to transfer the heat from the heat
exchange fluid in the pipes to the air before the air exits
through the vent pipes 56 and, in the case of a portion of the
compartments 46, through the vent pipes 60. During the passage
of air across the upper portion of the pipes 50, the heat
exchange fluid in the pipes condenses and drips under the
force of gravity to the lower portions of the pipes in the
lower housing portion 34 to continue the transfer of heat in
the above manner.
Referring again to FIG. 1, the condensed steam is drawn
from condenser sections 20, 22, 24, and 26, via lines 70, 72,
74, and 76, under the force of pumps 78 and 80 from which it is
passed to collection tanks, orthe like, for further treatment.
Another embodiment of the condenser section is referred
to in general by the reference numeral 88 in FIGS. 4-6, and
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includes a duct 90 which is provided for receiving the steam
from the pipes 14 or 16 and discharging the condensed steam to
the lines 70 and 72 in a manner similar to that of the lower
housing portion 34 of the previous embodiment. A plurality of
heat pipes 92 are provided with each having a lower portion 92a
extending within the duct 90 and an upper portion 92b projecting
outwardly from the upper surface of the duct. The upper heat
pipe portions 92b extend at an angle with respect to -the lower
portions 92a and laterally with respect to the duct 90. The
10 heat pipes 92 are divided into two groups 94 and 96, with the
heat pipes in one group extending toward one side of the duct
90 and the heat pipes in the other group extending toward the
other side of the duct. Each group g4 and 96 contains four
rows of heat pipes 92 with each row extending along the length
of the duct 90. In this manner the heat pipes 92 form a
substantial Y-shaped configuration when viewed from the end of
the duct 90, with the stem of the Y extending into the duct 90.
A plurality of fins 98 are provided over the upper heat
pipe portion 92b with only a few of the fins being depicted,
for the convenience of presentation. Each heat pipe 92 is
closed at each end, contains a heat exchange fluid, and operates
in identical fashion to the heat pipes 50 in the previous
embodiment.
A support plate 100 extends over and is connected to
the upper ends o~ the heat pipes 92 and supports an induced
draft fan 102 and a hood 104 which extends around the fan and
which is open at its upper end. An opening (not shown) is
provided in the support plate 100 to permit air to be drawn by
the fan 102 across the upper heat pipe portions 92b and through
the hood 104 for discharge into atmosphere as shown by the flow
arrows.
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In operation, the fan 102 operates to pull air across
the upper heat pipe portions 92b of both groups 94 and 96 of
heat pipes, and through the hood 104, which cools the heat
exchange fluid in the upper heat pipe portions 92b. The heat
exchange fluid condenses and drips downwardly into the lower
heat pipe portions 92b in the duct 90 and is vaporized by virtue
of its heat exchange with the steam passing through the latter
duct.
It is understood that the lower heat pipe portions 92a
may be slanted in the same manner as the lower portions of the
heat pipes 50 in the previous embodiment.
Several advantages result from the arrangement of the
present invention. For example, the necessity for a wick or
the like in connection with the heat pipes of both embodiments
is eliminated since the pipes operate as gravity controlled,
thermal siphons, i.e., the condensea heat exchange fluid in the
pipes drips under the force of gravity from the upper portion
of the pipes to the lower portions thereof. Also, the heat
exchanger of the present invention can be used in connection
with a conventional steam turbine having low back pressure and
low heat rates.
Also, in the embodiment of FIGS. 2 and 3 the slanted
lower portions of the heat pipes enable their length to be
increased without increasing the structural size of the steam
passage, and in acldition reduce the resistance to the steam
flow. Further, th~ technique in the embodiment of FIGS. 2 and
3 of utilizing at least a portion of the heated air exiting
from the boiler results in an increased efficiency of the over-
all system.
In the embodiment of FIGS. 4-6, the Y shape of the heat
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pipes minimizes air direction and velocity changes and reduces
recirculation of hot air through the system when compared to
forced draft fan air cool modules. Also, in the embodiment
of FIGS. 4-6 the packing density of the heat pipes is
relatively high, resulting in a relatively high air cooled
surface area per unit length duct which of course minimizes
the space requirements for the heat exchange apparatus. Also,
the embodiment of FIGS. 4-6 enables the most economical fan
size to be selected by varying the number of heat pipes and the
angle that the upper heat pipe portions make with the lower
heat pipe portions.
It can be appreciated that the present invention is
not restricted to use in a steam condensing environment, but
can be used in any situation in which a heat exchange between
two fluids is desired.
It is understood that other variations of the specific
construction and arrangement of the apparatus disclosed above
can be made by those skilled in the art without departing from
the invention as defined in the appended claims.
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