U.S. patent application number 14/156707 was filed with the patent office on 2014-07-24 for vortex shedding heat transfer method and apparatus.
This patent application is currently assigned to STANDEX INTERNATIONAL CORPORATION. The applicant listed for this patent is STANDEX INTERNATIONAL CORPORATION. Invention is credited to Michael J. Dobie.
Application Number | 20140202444 14/156707 |
Document ID | / |
Family ID | 51206739 |
Filed Date | 2014-07-24 |
United States Patent
Application |
20140202444 |
Kind Code |
A1 |
Dobie; Michael J. |
July 24, 2014 |
VORTEX SHEDDING HEAT TRANSFER METHOD AND APPARATUS
Abstract
A heating transfer method and apparatus that has a fixed
physical obstruction placed in the air path causing the airflow to
cause the airflow to shed into alternating patterns. A column is
placed perpendicular to the airflow path to provide an obstruction
to the airflow. The cross-section of the column can be round,
square or another multi-sided design. The obstruction will affect
the velocity and intensity at which the shedding occurs thus,
causing motion of the jets to deliver a more uniform cook on the
product surface.
Inventors: |
Dobie; Michael J.;
(Lewisville, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
STANDEX INTERNATIONAL CORPORATION |
Salem |
NH |
US |
|
|
Assignee: |
STANDEX INTERNATIONAL
CORPORATION
Salem
NH
|
Family ID: |
51206739 |
Appl. No.: |
14/156707 |
Filed: |
January 16, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61755573 |
Jan 23, 2013 |
|
|
|
Current U.S.
Class: |
126/21A ;
219/400; 219/405; 62/408 |
Current CPC
Class: |
A21B 1/245 20130101;
F25D 17/06 20130101; F25D 2400/28 20130101; F25D 2317/063 20130101;
F24C 15/322 20130101; F25D 2317/0665 20130101 |
Class at
Publication: |
126/21.A ;
219/400; 219/405; 62/408 |
International
Class: |
F24C 15/32 20060101
F24C015/32; F25D 17/06 20060101 F25D017/06 |
Claims
1. A heat transfer apparatus for providing uniform airflow to a
product, said apparatus comprising: a motor driven fan for
providing a controllable airflow; a plenum for receiving the
airflow, said plenum having a horizontal width, an orifice surface
that is essentially oriented parallel to the product; a plurality
of jets within the orifice surface of said plenum, wherein said
plurality of jets direct the airflow to the product; an obstruction
perpendicular to the airflow in said plenum, wherein said
obstruction has a predetermined cross-section shape, size
corresponding to the geometry of said plenum and the output of
airflow provided by the motor driven fan, wherein said obstruction
extends across the width of said plenum, wherein said obstruction
causes the airflow in the plenum to shed into alternating patterns
thus causing the airflow exiting said jets to change direction due
to vortex shedding taking place in said plenum.
2. The heat transfer apparatus of claim 1 wherein said
cross-sectional shape is a shape selected from the group consisting
of round, oval, or multi-sided.
3. The heat transfer apparatus of claim 1 wherein said obstruction
is rectangular.
4. The heat transfer apparatus of claim 1 wherein said apparatus is
part of an air impingement oven.
5. The heat transfer apparatus of claim 1 wherein said apparatus is
part of a refrigeration apparatus for quick cooling of products.
Description
[0001] This application claims benefit of U.S. Provisional
Application Ser. No. 61/755,573 filed on Jan. 23, 2013, pursuant to
35 USC .sctn.119 (e).
FIELD OF THE INVENTION
[0002] This invention relates to apparatus that have heat transfer
requirements for air impingement ovens, in particular, impingement
ovens wherein the product remains stationary relative to the
oven.
BACKGROUND OF THE INVENTION
[0003] Typically, batch impingement ovens provide air directly from
above and below the product that is to be cooked or heated. Batch
impingement ovens direct columns of air directly at the product
from above and below. In practice, most items, heated or cooked,
are supported by a pan or some other means of support such as
packaging material or cooking trays. The columns or jets of air
that strike the cooking support from below impart heat to the
support, which, in turn, delivers heat to the product via
conduction through the support.
[0004] Good batch oven design includes mechanisms for moving the
top air jets in relation to the product. This motion is necessary
to prevent localized overheating and browning of the product
surface. The motion evens out the heat transfer, resulting in even
cooking and browning of the products. Motion mechanism may move the
jets themselves, while the product remains stationary, or as in
alternative technologies, the product, itself, moves via a moving
product support.
[0005] Conveyor ovens solve this problem by moving the product
under the jets of air. Other ovens solve the problem by moving the
jets or changing the direction of the airflow out of the jet
orifices. Ovens that change the jet direction have used an air vane
that is mounted on a motor driven shaft.
[0006] All of the above solutions are mechanisms that have the
complication of moving parts within a heated environment. These
mechanisms are subject to maintenance issues due to the heat and
can lead to mechanical breakdowns and failure of electrical
components due to the hostile environment.
[0007] Vortex shedding is a well-known fluid dynamics principle
that occurs when fluid flows past a blunt object, resulting in
vortices that alternately shed and detach from the blunt object.
The fluid then flows in alternating wave-like patterns due to the
low-pressure vortices behind the blunt object.
[0008] The inventor has discovered new and unexpected uses for this
vortex shedding oscillating flow principle for use in impingement
oven designs. Vortex shedding creates a new, superior method of
imparting motion to heated air jets resulting in improved evenness
of cooking and heating, with minimal mechanisms having to be
located in hostile environments.
[0009] While the primary use of the vortex shedding principles are
directed toward batch air impingement ovens, the invention can also
be used with other ovens and for quick cooling devices such as
beverage coolers, ice makers, and the like.
[0010] There is not found in the prior art the use of vortex
shedding principles for batch impingement ovens or quick cooling
apparatus.
SUMMARY OF THE INVENTION
[0011] It is an aspect of the invention to provide a heating
transfer method and apparatus that has a fixed physical obstruction
placed in the air path causing the airflow to cause the airflow to
shed into alternating patterns.
[0012] It is another aspect of the invention to provide a heating
transfer method and apparatus that has a column running
perpendicular to the airflow path to provide an obstruction to the
airflow.
[0013] Another aspect of the invention is to provide a heating
transfer method and apparatus wherein the cross-section of the
column can be round, square or another multi-sided design.
[0014] It is still another aspect of the invention to provide a
heating transfer method and apparatus where the obstruction will
affect the velocity and intensity at which the shedding occurs.
[0015] Finally, it is an aspect of the invention to provide a
heating transfer method and apparatus such that once the
cross-sectional shape and area of the obstruction are optimized for
the oven air duct geometry, air velocity and fluid density, an
alternating wave in the duct will cause motion of the jets to
deliver a more uniform cook on the product surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is an end view of a typical air impingement oven.
[0017] FIG. 2 is a cross-sectional view along section lines A-A as
shown in FIG. 1.
[0018] FIG. 3 is a detailed cross-sectional view of the vortex
shedding heat transfer apparatus in accordance with the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] Referring now to FIG. 1, a typical batch air impingement
oven 8 is shown illustrating section line A-A. FIG. 2 shows a
cross-sectional side of oven 8 along section A-A.
[0020] Referring to FIG. 2 and the detailed view shown in FIG. 3,
invention 10 is depicted.
[0021] As shown, obstruction 16 is placed within plenum 12 causing
airflow 18 to shed into alternating patterns 14 as shown.
Obstruction 16 preferably has a rectangular cross-sectional shape.
However, other cross-sectional shapes could also be used such as
round, oval, or even multi-sided. Obstruction 16 is a column that
extends across the entire plenum 12 perpendicular to airflow 18.
The cross-sectional shape and size of obstruction 16 will affect
the velocity and intensity at which the shedding of airflow 18
occurs. When the cross-sectional shape and area of obstruction 16
are optimized for a particular oven plenum 12 geometry, an
alternating wave 14 in plenum 12 will cause the airflow exiting
jets 22 to deliver a more uniform heating to product 26 supported
by pan 24.
[0022] Airflow 18 is provided by motor driven fan 20. Airflow from
jets 22 is of an intensity that could cause an increased heat
transfer coefficient directly below each jet 22. This localized
higher transfer rate is usually undesirable if this localized spot
remains in the same place. Invention 10 using vortex shedding
principles solves this problem. The direction of the air exiting
jets 22 changes due to vortex shedding taking place in the air
plenum delivery duct 12.
[0023] When optimized, jets 22 deliver essentially a perpendicular
airflow to the surface of product 26, which is supported by pan 24.
This a major improvement as this method of vortex shedding
eliminates the problem of a localized heat transfer coefficient
without the need for mechanically changing the position of jets 22
or changing the direction of airflow 18 as it exits jets 22 by
using air vanes or other methods. Invention 10 accomplishes this
task without the need for moving parts.
[0024] For a typical oven 8 as shown in FIG. 1, the preferred
dimensions are as follows. Plenum 12 is approximately 2.5 inches
high, 16 inches wide and 16 inches long with a decreasing
cross-sectional area. Jet orifices 22 in this embodiment are
approximately 5/8 inch in diameter each with orifices 22 being
twenty-three in number. Obstruction 16 is placed horizontally
across plenum 12 to cause the creation of vortices 14 downstream.
Obstruction 16 in this example is a 1/2 inch square tube across the
full 16 inch plenum 12. These vortices 14 effect the direction of
airflow 18 out of jet orifices 22.
[0025] Fan 20 is delivering approximately 120 cfm into plenum 12;
airflow 18 crosses obstruction 16 travelling at approximately 500
fpm to create the vortices 14. The air vortices 14 then exits
orifices 22 at approximately 3000 fpm. The location of obstruction
16 was determined experimentally by observing the direction of the
airstreams from jets 22 while moving obstruction 16 in plenum 12.
The location selected for obstruction 16 is where the maximum
movement of the airstreams was observed.
[0026] Although the present invention has been described with
reference to certain preferred embodiments thereof, other versions
are readily apparent to those of ordinary skill in the preferred
embodiments contained herein.
* * * * *