U.S. patent application number 13/378814 was filed with the patent office on 2012-04-19 for core box with air vents integrated in pins.
This patent application is currently assigned to BEKAERT COMBUSTION TECHNOLOGY B.V.. Invention is credited to Paul Thijssen, Jan Van Peteghem.
Application Number | 20120090563 13/378814 |
Document ID | / |
Family ID | 42173552 |
Filed Date | 2012-04-19 |
United States Patent
Application |
20120090563 |
Kind Code |
A1 |
Thijssen; Paul ; et
al. |
April 19, 2012 |
CORE BOX WITH AIR VENTS INTEGRATED IN PINS
Abstract
The invention relates to sand casting and more specifically to
sand casting of a heat exchanger element with pins and/or fins. The
invention provides a core box for sand casting of workpieces
comprising pins and/or fins. The core box molding surface comprises
at least one air vent and pins and/or fins. The at least one air
vent is integrated in at least one pin or fin.
Inventors: |
Thijssen; Paul; (Steyl,
NL) ; Van Peteghem; Jan; (Bornem, BE) |
Assignee: |
BEKAERT COMBUSTION TECHNOLOGY
B.V.
|
Family ID: |
42173552 |
Appl. No.: |
13/378814 |
Filed: |
June 17, 2010 |
PCT Filed: |
June 17, 2010 |
PCT NO: |
PCT/EP2010/058509 |
371 Date: |
December 16, 2011 |
Current U.S.
Class: |
122/367.1 ;
164/15; 164/234 |
Current CPC
Class: |
F28F 2255/14 20130101;
B22C 7/065 20130101; F28F 3/022 20130101; B22C 9/123 20130101; F28D
9/0081 20130101; F24H 1/26 20130101; B22D 25/02 20130101; B22C
9/106 20130101 |
Class at
Publication: |
122/367.1 ;
164/234; 164/15 |
International
Class: |
F22B 37/00 20060101
F22B037/00; B22C 9/10 20060101 B22C009/10; B22C 7/06 20060101
B22C007/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 23, 2009 |
EP |
09163465.9 |
Claims
1-10. (canceled)
11. A core box for sand casting comprising at least one air vent
and pins and/or fins of a particular heat exchanger geometry and
being fixed to the core box, wherein said at least one air vent is
integrated in at least one of said pins and/or fins.
12. A core box for sand casting according to claim 11, wherein said
at least one air vent being located at the base section of said
pins and/or fins.
13. A core box for sand casting according to claim 11, wherein said
at least one air vent being located at the surface of the body of
said pins and/or fins.
14. A core box for sand casting comprising pins according claim 11,
wherein said pins and/or fins have a diameter equal to or smaller
than 3 mm.
15. A core box for sand casting according to claim 11, said core
box comprising equal to or more than 250 pins and/or fins per
square meter.
16. Method for the production of a pinned and/or finned heat
exchanger element, said method comprising: providing a core box,
said core box comprising pins and/or fins of a particular heat
exchanger geometry and being fixed to the core box, said core box
further comprising at least one air vent, wherein said at least one
air vent is integrated in at least one of said pins and/or fins;
shooting a mixture of sand and binder into said core box, which is
subsequently left to harden; removing said core box, thereby
obtaining a sand core; placing said sand core in a molding box;
pouring molten metal into said molding box thereby obtaining a heat
exchanger element around said sand core; cooling of the cast heat
exchanger element; removing said sand core.
17. A sand cast heat exchanger element comprising walls provided
with pins and/or fins which enlarge the heat-exchanging surface, as
obtained by the method of claim 16.
18. Use of the core box as defined in claim 11 for the production
of pinned and/or finned heat exchanger element.
19. Use of the heat exchanger as defined in claim 17 in a heating
boiler.
20. A heating boiler provided with a heat exchanger element
according to claim 17.
Description
DESCRIPTION
[0001] 1. Technical Field
[0002] The present invention relates to sand casting and all
casting processes where sand core are used, and more in particular
to a sand casting for production of pin finned workpieces.
[0003] The invention further relates to such workpieces, e.g. heat
exchanger elements provided with a dense array of pinned fins.
[0004] 2. Background Art
[0005] Heat exchanging surfaces are commonly provided with pin
fins. These pin fins provide an enlargement of the heat exchanging
surface, as more surface of the heat exchanger is in contact with
the cooling or heating fluid.
[0006] A further enlargement of the heat exchanging surface can be
obtained by using thinner and thus also shorter pins which also
allows more pins on the same surface area, thereby obtaining a
greater surface content, as described in EP1722172. Still more
enlargement of the heat exchanging surface is however limited by
the inter pin or fin spacing, reduction below which it is
impossible or impracticable to go with present manufacturing
methods in an effort to increase surface area.
DISCLOSURE OF INVENTION
[0007] It is an object of the present invention to escape the
limitations of the sand casting process for further enlargement of
the heat exchanging surface. More precisely, the object of the
present invention is to provide an improved sand casting method
enabling the enlargement of the heat exchanging surface.
[0008] In making sand cores or molds for subsequent casting
purposes, the sand mixture is delivered to the core box cavity by
means of compressed air. This core box is provided with a number of
fixed pins or fins with a particular heat exchanger geometry. The
terms "particular heat exchanger geometry" refer to the fact that
the pins or fins have about the same geometry of the pins or fins
in the heat exchanger which will be made by means of the sand core
or sand mold. Although other geometrical are not excluded, the pins
or fins have a cylindrical form with a diameter of maximum 3.0 mm
or have a frusto-conical form with an average diameter of maximum
3.0 mm. It is general practice in molding such core to provide air
vents in the molding surfaces of the core box in positions which
will do the most good in obtaining sound cores. When a blast of
airborne sand is received by the core box, the air must be rapidly
vented while the sand remains entrapped within the core box cavity.
In the currently available pins and/or fins sand casting technology
the air vents are located in between three neighboring pins or in
between two neighboring fins and have a diameter of minimally 4 mm.
This means that a possible enlargement of the heat exchanging
surface is restricted by those 4 mm.
[0009] The present invention mitigates this restriction by
providing air vents in or integrated in the pins and/or fins. An
aspect of the present invention provides a core box for sand
casting of workpieces comprising pins and/or fins. The core box
molding surface comprises at least one air vent and pins and/or
fins. The at least one air vent is integrated in at least one pin
or fin. The integration of the air vents in the pins and/or fins
allows a densification of the pin and/or fin array, which thereby
enlarges the heat exchanging surface. This is especially useful
when relatively big air vents are needed for sufficient venting in
the core box, but a large heat exchanging surface of the cast heat
exchanger is desired.
[0010] US-A1-2003/0173049 discloses a method and an apparatus for
making a sand mold utilizing reverse purge air through a core box
and to harden the binder in the sand mold proximate the ejection
pins. In a particular embodiment, the ejection pins are hollow
tubes functioning as vents.
[0011] Coming back to the present invention, the pins used here can
have any appropriate diameter. Preferably, the pins have a diameter
of 3.0 mm or smaller. This enables a further enlargement of the
heat exchanging surface of the heat exchanger element produced with
the core box according to the present invention.
[0012] In a preferred aspect, the at least one air vent is
integrated in the base section of the pin or fin. Such air vent can
cover the complete circumference of the base section of the pin or
fin. In an alternative preferred aspect, one or more air vent(s)
can cover only part of the circumference of the base section of the
pin or fin. As such, more than one air vent can be present at the
base section of the pin or fin.
[0013] In another preferred aspect, the at least one air vent is
integrated in the surface of the body of the pin or fin. Such air
vent can cover the complete circumference of the body of the pin or
fin. In an alternative preferred aspect, the air vent can cover
only part of the circumference of the body of the pin or fin. As
such, more than one air vent can be present at the body of the pin
or fin.
[0014] In still another preferred aspect, the at least one air vent
is integrated in the top surface of the pin or fin. In case fins
are being cast, more than one air vent can be present at the top of
the fin. A further advantage of this preferred embodiment is that
the body of the pin and/or fin is part of the required walls of the
air vent.
[0015] The integration of the air vents in the pins and/or fins
makes it now possible to make more dense arrays of pins and/or
fins. This more dense array of pins and/or fins in the core box for
sand casting enables the enlargement of the heat exchanging surface
of pin and/or fin containing heat exchanger elements produced by
use of such core box.
[0016] An aspect of the claimed invention provides a sand cast heat
exchanger element comprising walls. The walls of the heat exchanger
element are provided with pins and/or fins which enlarge the
heat-exchanging surface. The pins and/or fins are forming an array,
wherein that array comprises equal to or more than 250 pins and/or
fins per square meter.
[0017] Such heat exchangers have more heat exchanging surface, for
a slightly increased heat exchanger weight, which allows an equal
or even better thermal inertia of the system and also the reaction
time stays the same or becomes even better.
[0018] Another aspect of the present invention provides a method
for the production of a pinned and/or finned heat exchanger
element. This method comprises following steps. First, a pinned
and/or finned core box is provided. This core box comprises at
least one air vent. This at least one air vent is integrated in at
least one of said pins and/or fins. Then, a mixture of sand and
binder is shot into said core box. The sand-binder mixture is
subsequently left to harden. In cold box processes, catalyst gas
for hardening is led through the air vents. Thereafter, the core
box is removed, thereby obtaining a sand core. This sand core is
then placed in a moulding box. Molten metal is poured into said
moulding box thereby obtaining a heat exchanger element around said
sand core. Thereafter the cast heat exchanger element is cooled;
whereafter the sand core is removed.
[0019] Another aspect of the present invention provides the use of
the core box according to the present invention for the production
of a pinned and/or finned heat exchanger element.
[0020] In a further aspect, the present invention provides the use
of the heat exchanger element as defined by the present
invention.
[0021] A further aspect provides a heating boiler provided with a
heat exchanger element according to the present invention.
Definitions
[0022] The term `core box` should be understood to be every mould
used in sand casting in which air vents are being used: e.g. core
box, pattern, mould box or other mould.
[0023] The term pitch should be understood as the distance from the
centers in between two neighboring pins and/or fins.
BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS
[0024] Example embodiments of the invention are described
hereinafter with reference to the accompanying drawings in
which
[0025] FIG. 1 shows a top view of a pinned core box for a heat
exchanger element.
[0026] FIG. 2 shows a cross section taken along line II-II' of FIG.
1.
[0027] FIG. 3 shows a cross section of a pinned core box with an
exemplary air vent configuration according to the present
invention.
[0028] FIG. 4 shows a cross section of a pinned core box with
another exemplary air vent configuration according to the present
invention.
[0029] FIG. 5 shows a cross section of a pinned core box with still
another exemplary air vent configuration according to the present
invention.
[0030] FIG. 6 shows an exemplary heat exchanger element according
to the present invention.
[0031] FIG. 7 shows a cross section taken along line VII-VII' of
FIG. 6.
[0032] FIG. 8 shows a cross section taken along line VIII-VIII' of
FIG. 6.
[0033] FIG. 9 shows an alternative pin with integrated air
vents.
MODE(S) FOR CARRYING OUT THE INVENTION
[0034] Examples of a pinned or finned core box for sand casting,
air vent arrangement, sand cast heat exchanger elements and a
method for production of such heat exchanger elements will now be
described with reference to FIGS. 1 to 8.
[0035] Vents will be provided as is well known in core boxes in
which cores are to be blown and in known manner would be provided
with suitable means for preventing the escape of the sand particles
with the escaping air.
[0036] FIG. 1 shows a top view of a prior art pinned core box for
casting of a heat exchanger element. X represents the horizontal
pitch in between two consecutive pins. Y represents the vertical
pitch in between two rows of pins. In this example, pins (1) have a
conical shape, which is shown in FIG. 1 as two concentric circles,
the inner one representing the top of the pin, the outer circle
representing the base of the pin. In the prior art, air vents (2)
are located in between the base sections of three neighboring pins.
FIG. 2 shows a cross section taken along line II-II' of FIG. 1.
[0037] FIG. 3 shows a cross section of a pinned or finned core box
for the sand casting of a heat exchanger element with an exemplary
air vent configuration according to the present invention. In a
first exemplary embodiment according to FIG. 3, the air vent's exit
(3) covers the complete circumference of the body of the pin or
fin. In an alternative exemplary embodiment according to FIG. 3,
the air vent's exit (3) covers only part of the circumference of
the body of the pin or fin. Alternatively, multiple exits (3) of
the air vent cover multiple parts of the circumference of the body
of the pin or fin.
[0038] FIG. 4 shows a cross section of a pinned or finned core box
for the sand casting of a heat exchanger element with another
alternative air vent configuration. In a first exemplary embodiment
according to FIG. 4, the air vent's exit covers the complete
circumference of the base section of a pin. In an alternative
exemplary embodiment according to FIG. 4, the air vent's exit (3)
covers only part of the circumference of the base section of the
pin. As such, more than one air vent is present at the base section
of the pin or fin. Alternatively, multiple exits (3) of the air
vent cover multiple parts of the circumference of base section of
the pin.
[0039] FIG. 9 shows another example embodiment of a pin with
integrated air vents. FIG. 9A shows a 3-D drawing of such a pin
wherein multiple air vents are present in the collar of the pin. It
must be understood that such pins are then integrated in the
molding surface of the core box. FIG. 9B shows a section according
to line B-B'. It must be understood that the collar of the pin will
be integrated in the molding wall of the core box.
[0040] FIG. 5 shows a cross section of a pinned or finned core box
for the sand casting of a heat exchanger element with still another
alternative air vent configuration. In a first exemplary embodiment
according to FIG. 5, the core box comprises pins and the air vents
are located at the top in the center of the pin. As such, only one
air vent is present at a pin. In a second exemplary embodiment
according to FIG. 5, the core box comprises fins and the air vents
are located at the top of the fins. As such, more than one air vent
is present at the top of the fin.
[0041] An example embodiment provides a sand cast heat exchanger
element comprising walls. The walls of the heat exchanger element
are provided with pins and/or fins which enlarge the
heat-exchanging surface. The pins and/or fins forming an array,
wherein that array comprises equal to or more than 250 pins and/or
fins per square meter. In this example the pin array is composed of
pins with a diameter of 3 mm, and the air vents located at the base
section of the pins. The array has a horizontal pitch X of 5 mm and
vertical pitch Y of 4.66 mm. This array provides 429 pins/m.sup.2
and a heat exchanging surface of 303 m.sup.2/m.sup.3. Such heat
exchanger element has a density of 30.3%. For comparison, current
state of the art sand castings with air vents with diameter of 4 mm
and use of pins with diameter of 3 mm, the array having a
horizontal pitch X of 5.75 mm and vertical pitch Y of 5.5 mm,
provide an array with 316 pins/m.sup.2 and provide a heat
exchanging surface of 223 m.sup.2/m.sup.3. Such heat exchanger
element has a density of 22.4%.
[0042] Another example embodiment of a sand cast heat exchanger
element according to the present invention comprises a pin array of
pins with diameter of 5.7 mm with a horizontal pitch X of 8.5 mm
and a vertical pitch Y of 7.25 mm wherein the air vents are located
at the top of the pins. This provides an array with 162
pins/m.sup.2 and a heat exchanging surface of 415 m.sup.2/m.sup.3
and a density of 41.5%.
[0043] The density of the pin and/or fin array is an indication for
the pressure drop which might be expected for this pin and/or fin
array. As can be seen from the above examples of 3 mm pins, the
density is not strongly affected by the densification of the pin
configuration.
[0044] A method for the production of such a pinned and/or finned
heat exchanger element comprises following steps.
[0045] First, a pinned and/or finned core box is provided. This
core box comprises at least one air vent. This at least one air
vent is integrated in at least one of said pins and/or fins. Then,
a mixture of sand and binder is shot into said core box. The
sand-binder mixture is subsequently left to harden. In cold box
processes, catalyst gas for hardening is led through the air vents.
Thereafter, the core box is removed, thereby obtaining a sand core.
This sand core is then placed in a moulding box. Molten metal is
poured into said moulding box thereby obtaining a heat exchanger
element around said sand core. Thereafter the cast heat exchanger
element is cooled; whereafter the sand core is removed.
[0046] FIGS. 6 to 8 show a sand cast heat exchanger element (5)
comprising walls (6) substantially of aluminium, said walls (6)
enclosing at least one water carrying channel (7) and having at
least one flue gas draft (10). At least one wall (6) forms a
boundary between water carrying channel (7) and flue gas draft
(10). The at least one wall is provided with pinned fins and/or
fins (8,9) which enlarge the heat-exchanging surface and which
extend in the flue gas draft (10). The pinned fins and/or fins form
an array, wherein the array comprises equal to or more than 250
pinned fins and/or fins per square meter. In a first exemplary sand
cast heat exchanger element the air vents in the core box were part
of the pins as shown in FIG. 3. In an alternative exemplary sand
cast heat exchanger element, the air vents in the core box were
part of the pins as shown in FIG. 4. In a further alternative
exemplary sand cast heat exchanger element, the air vents in the
core box were part of the pins as shown in FIG. 5.
[0047] The illustrated exampled of the present invention the pins
have a conical shape, although in another example, another shape
e.g. completely cylindrical or dimples, could be present. It is
clear to the man skilled in the art, that any shape of heat
exchange enlarging structures can be used.
[0048] Thus there has been described a pinned or finned core box
for sand casting, air vent arrangement, sand cast heat exchanger
elements and a method for production of such heat exchanger
elements. The invention further relates to a heat exchanger element
with a very dense pinned fin and/or fin array having equal to or
more than 250 pins and/or fins per square meter. The invention also
provides methods for obtaining such a dense pinned fin and/or fin
array, by modifying the air vents in the sand casting core box.
This invention provdes thus a solution for the further enlargement
of the heat exchanging surface in a pinned and/or finned heat
exchanger element.
* * * * *