U.S. patent application number 12/570202 was filed with the patent office on 2010-05-13 for frost reduction by air curtain.
This patent application is currently assigned to THERMO FISHER SCIENTIFIC (ASHEVILLE) LLC. Invention is credited to Wendell Morris, Dennis H. Smith.
Application Number | 20100120351 12/570202 |
Document ID | / |
Family ID | 42165664 |
Filed Date | 2010-05-13 |
United States Patent
Application |
20100120351 |
Kind Code |
A1 |
Morris; Wendell ; et
al. |
May 13, 2010 |
FROST REDUCTION BY AIR CURTAIN
Abstract
An ultra-low temperature freezer, including a cabinet with a
freezer compartment maintained within a certain temperature range,
a door providing a seal with the cabinet when engaged with the
cabinet, a catch basin at the bottom of the cabinet for collecting
air, and a distribution channel fluidly connected to the catch
basin, for recirculating the air collected from the catch basin to
the top of the cabinet, the distribution channel at the top of the
cabinet pushing compressed air across the front of the cabinet and
forming an air curtain and thermal barrier to incoming warmer
air.
Inventors: |
Morris; Wendell; (Asheville,
NC) ; Smith; Dennis H.; (Dubuque, IA) |
Correspondence
Address: |
WOOD, HERRON & EVANS, LLP
2700 CAREW TOWER, 441 VINE STREET
CINCINNATI
OH
45202
US
|
Assignee: |
THERMO FISHER SCIENTIFIC
(ASHEVILLE) LLC
Asheville
NC
|
Family ID: |
42165664 |
Appl. No.: |
12/570202 |
Filed: |
September 30, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61112904 |
Nov 10, 2008 |
|
|
|
Current U.S.
Class: |
454/193 |
Current CPC
Class: |
F25D 21/04 20130101;
F25D 23/023 20130101 |
Class at
Publication: |
454/193 |
International
Class: |
F24F 9/00 20060101
F24F009/00 |
Claims
1. An ultra-low temperature freezer, comprising: a cabinet with a
freezer compartment maintained within a certain temperature range;
a door providing a seal with the cabinet when engaged with the
cabinet; a catch basin at the bottom of the cabinet for collecting
air; and a distribution channel fluidly connected to the catch
basin, for recirculating the air collected from the catch basin to
the top of the cabinet, the distribution channel at the top of the
cabinet pushing compressed air across the front of the cabinet and
forming an air curtain and thermal barrier to incoming warmer
air.
2. The apparatus of claim 1, wherein the distribution channel is
disposed exterior to the cabinet and configured to compress the
air.
3. The apparatus of claim 1, further comprising nozzles disposed on
the distribution channel at the top of the cabinet for outputting
the compressed air.
4. The apparatus of claim 1, further comprising at least two plates
with an opening in between, on the distribution channel at the top
portion of the cabinet for forming the air curtain.
5. The apparatus of claim 1, wherein the distribution channel is
disposed between insulation and an evaporator.
6. The apparatus of claim 1, wherein the distribution channel
includes a tortured path from a front of the freezer to the back of
the freezer and back to the front of the freezer, where the front
of the freezer is the plane where the door seals the cabinet.
7. The apparatus of claim 1, wherein the distribution channel
includes a middle portion between the door and a second door
connected to the cabinet, providing an air curtain from the middle
portion to the catch basin.
8. An ultra-low temperature refrigeration apparatus, comprising: a
cabinet with a freezer compartment maintained within a certain
temperature range; a door providing a seal with the cabinet when
engaged with the cabinet; a collection means at the bottom of the
cabinet for collecting gas; and a distribution means fluidly
connected to the collection means, for recirculating the gas
collected from the collection means to the top of the cabinet, the
distribution means at the top of the cabinet pushing compressed gas
across the front of the cabinet and forming a curtain and thermal
barrier to warmer outside environment.
9. The apparatus of claim 8, wherein the distribution means is
disposed exterior to the cabinet.
10. The apparatus of claim 8, further comprising nozzles disposed
on the distribution means at the top of the cabinet for outputting
the compressed gas.
11. The apparatus of claim 8, further comprising at least two
plates with an opening in between, on the distribution means at the
top portion of the cabinet for forming the curtain.
12. The apparatus of claim 8, wherein the distribution means is
disposed between insulation and an evaporator.
13. The apparatus of claim 8, wherein the distribution means
includes a tortured path from a front of the apparatus to the back
of the apparatus and back to the front of the apparatus, where the
front of the apparatus is the plane where the door seals the
cabinet.
14. The apparatus of claim 8, wherein the distribution means
includes a middle portion between the door and a second door
connected to the cabinet, providing the curtain from the middle
portion to the collection means.
15. A method of an ultra-low temperature freezer, comprising:
collecting air at a catch basin at the bottom of a freezer cabinet
when opening a door of the freezer; compressing and distributing
the air collected from the catch basin to the top of the cabinet
via a distribution channel; and outputting the compressed air
across the front of the cabinet from the top of the cabinet to the
bottom of the cabinet toward the catch basin and forming an air
curtain and thermal barrier to incoming warmer air.
16. The method of claim 15, further comprising of recirculating the
air outputted across the front of the cabinet and into the catch
basin via a distributing channel.
17. The method of claim 15, further comprising cooling the air
through the distribution channel disposed adjacent to an
evaporator.
18. The method of claim 15, further comprising of actively cooling
and compressing the air circulating through the distribution
channel.
Description
[0001] The present application claims the filing benefit of U.S.
Provisional Application Ser. No. 61/112,904, filed Nov. 10, 2008,
the disclosure of which is incorporated herein by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to a method and
system of frost reduction in freezers. More particularly, the
present invention relates to a system and method of reducing frost
in ultralow temperature freezers by an air curtain.
BACKGROUND OF THE INVENTION
[0003] There has been a rapid increased demand for refrigeration
systems that can attain a very low temperature range. One type of
system that can reach such temperatures is called an ultra-low
refrigeration system or called an ultra-low freezer, which can
maintain a very low range of temperatures. The ultra-low
temperature refrigeration systems can be used to store and protect
a variety of objects including critical biological samples so that
they are safely and securely stored for extended periods of time.
However, with the low storage temperatures involved and the need to
periodically insert and remove particular samples from the freezer
compartment, various problems may arise.
[0004] Generally, in refrigeration systems, a refrigerant gas is
compressed in a compressor unit. Heat generated by the compression
is then removed generally by passing the compressed gas through a
water or air cooled condenser coil. The cooled, condensed gas is
then allowed to rapidly expand into an evaporating coil surrounding
a refrigerator or freezer compartment where the gas becomes much
colder, thus cooling the coil and the compartment of the
refrigeration system or freezer around which the coil is
placed.
[0005] Ultra-low and cryogenic temperatures ranging from
approximately -95 degrees Celsius to -150 degrees Celsius have been
achieved in refrigeration systems using a single circuit vapor
compressor or dual circuit vapor compressors. The single circuit
systems typically use a single compressor to pump a mixture of four
or five chlorofluorocarbon (CFC) containing refrigerants to reach
an evaporative temperature of as low as -160 degrees Celsius.
[0006] During normal operation, freezers accumulate frost as a
result of humid air entering the freezer. This problem is
especially critical in ultra-low temperature freezers as the
samples stored in such freezers can be particularly sensitive to
changes in the environment within the freezer. The frost that is
developed, even in the smallest amounts, can affect the environment
of some or all of the individual samples within the freezer
compartment and, therefore, contribute to serious problems. There
is a need for having greater control of the environment within such
a freezer, especially a control of the frost conditions that can
develop with everyday use of such a freezer.
SUMMARY OF THE INVENTION
[0007] The foregoing needs are met, to a great extent, by the
present invention, wherein, in one aspect, an apparatus and
technique is provided for reducing the accumulation of frost in the
sample compartment of the freezer apparatus.
[0008] In accordance with one aspect of the invention, an ultra-low
temperature freezer, includes a cabinet with a freezer compartment
maintained within a certain temperature range, a door providing a
seal with the cabinet when engaged with the cabinet, a catch basin
at the bottom of the cabinet for collecting air, and a distribution
channel fluidly connected to the catch basin, for recirculating the
air collected from the catch basin to the top of the cabinet, the
distribution channel at the top of the cabinet pushing compressed
air across the front of the cabinet and forming an air curtain and
thermal barrier to incoming warmer air.
[0009] The freezer can also include the distribution channel
disposed exterior to the cabinet. The freezer can also include
nozzles disposed on the distribution channel at the top of the
cabinet for outputting the compressed air. Additionally, there can
be at least two plates with an opening in between, on the
distribution channel at the top portion of the cabinet for forming
the air curtain. Moreover, the distribution channel can be disposed
between insulation and an evaporator.
[0010] Alternatively, the distribution channel can include a
tortured path from a front of the freezer to the back of the
freezer and back to the front of the freezer, where the front of
the freezer is the plane where the door seals the cabinet.
Furthermore, the distribution channel can include a middle portion
between the door and a second door connected to the cabinet,
providing an air curtain from the middle portion to the catch
basin.
[0011] In another aspect of the present disclosure, an ultra-low
temperature refrigeration apparatus, includes a cabinet with a
freezer compartment maintained within a certain temperature range,
a door providing a seal with the cabinet when engaged with the
cabinet, a collection means at the bottom of the cabinet for
collecting gas, and a distribution means fluidly connected to the
collection means, for recirculating the gas collected from the
collection means to the top of the cabinet, the distribution means
at the top of the cabinet pushing compressed gas across the front
of the cabinet and forming a curtain and thermal barrier to warmer
outside environment.
[0012] In yet another aspect of the present disclosure, a method of
an ultra-low temperature freezer, includes collecting air at a
catch basin at the bottom of a freezer cabinet when opening a door
of the freezer, compressing and distributing the air collected from
the catch basin to the top of the cabinet via a distribution
channel, and outputting the compressed air across the front of the
cabinet from the top of the cabinet to the bottom of the cabinet
toward the catch basin and forming an air curtain and thermal
barrier to incoming warmer air.
[0013] This disclosure describes certain embodiments of the
invention in order that the detailed description may be better
understood, and in order that the present contribution to the art
may be better appreciated. Additional embodiments of the invention
are described below or will be apparent from this description to
one skilled in the art and do not limit the subject matter of the
invention as set forth in the claims.
[0014] The invention includes embodiments in addition to those
described and of being practiced and carried out in various ways.
Also, it is to be understood that the phraseology and terminology
employed herein, as well as the abstract, are for the purpose of
description and should not be regarded as limiting.
[0015] As such, those skilled in the art will appreciate that the
conception upon which this disclosure is based may readily be
utilized as a basis for the designing of other structures, methods
and systems for carrying out the several purposes of the present
invention. It is important, therefore, that the claims be regarded
as including such equivalent constructions insofar as they do not
depart from the spirit and scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and, together with a general description of the
invention given above, and the detailed description of the
embodiments given below, serve to explain the principles of the
invention.
[0017] FIG. 1 illustrates a front view of one embodiment of a
freezer.
[0018] FIG. 2 is a side view of the freezer of FIG. 1 with an air
curtain unit.
[0019] FIG. 3 is a partial view of the freezer of FIG. 1, showing
the distribution channel forming the air curtain.
[0020] FIG. 4 is a detailed view of the air curtain unit.
[0021] FIGS. 4A and 4B are diagrammatic views of alternative
embodiments of distribution channels.
[0022] FIG. 5 illustrates another embodiment with a tortured path
for the distribution channel.
[0023] FIG. 6 illustrates another embodiment with a selectively
reduced area for the air curtain.
[0024] FIG. 7 illustrates yet another embodiment with the
distribution channel embedded within the freezer.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The invention will now be described with reference to the
figures, in which like reference numerals refer to like parts
throughout.
[0026] Frost accumulates during routine operation of ultra-low
temperature freezers through humid air entering the freezer.
Sources for air entry in the freezers are, for example, a door
opening to remove and/or replace experiment samples. Humid air can
also enter through a faulty seal in the storage chamber of the
freezer or in the door that seals the chamber. Humid air can also
enter, as described below, during the pressure equalization process
that occurs after the door is resealed if warmer (less dense) air
has entered the freezer compartment while the door was open.
[0027] As seen in FIG. 1, the ultra-low temperature freezer 10 can
include an outer frame 14, with insulated walls of the cabinet 12
of the freezer 10 providing a storage chamber or freezer
compartment 24 to contain materials being cooled and maintained at
low temperatures in a desired range (e.g., -80.degree. C. to
-160.degree. C. or -95.degree. C. to -150.degree. C., for
biological laboratory samples). The storage chamber or freezer
compartment 24 can be subdivided further into a plurality of
compartments (not shown). The freezer 10 also includes a door 16
that is attached to the frame or outer housing 14 and provides a
seal of the freezer 10, including the freezer compartment 24, when
closed. FIG. 1 shows the door 16 in the open position, in which
humid air can be transferred from outside of the freezer 10 into
the compartment 24.
[0028] Over a period of time, especially as the freezer door 16 is
opened to insert new samples or remove samples, frost will build up
due to condensation of humidity from the admitted air onto surfaces
of the freezer compartment 24 and surfaces of the samples. During
the door 16 opening, the very dense cold air (-90.degree. C.)
quickly falls out of the bottom of the cabinet 12 and is replaced
by ambient air. Since the ambient air typically has higher moisture
content than the cold air, moisture condenses quickly on all cold
areas inside the cabinet 12. Over a prolonged period of time, this
causes an increase in ice formation build-up. Over time, this frost
can impede operation and will have to be removed by the user. The
removal of frost can be accomplished by defrosting the freezer 10
or "chipping" the frost away. Neither of these methods is easily
accomplished. A defrost requires the freezer compartment or chamber
24 to be empty and samples stored in the freezer 10 are not allowed
to defrost. Manually removing the frost is cumbersome and can
result in damage to the freezer 10 interior and possible damage to
stored samples. Both methods are time consuming and add no value to
the user's process. Additionally, any automated defrosting method
will also require time and there is a danger of affecting the
materials stored in the freezer 10 within the freezer compartment
24, especially when the stored materials are hyper-sensitive to
even the slightest of temperature fluctuations.
[0029] However, the freezer 10 of the present disclosure does
include an air curtain unit 100 that will reduce the frost. The air
curtain unit 100 has a catch basin 200 positioned below the area
where the door 16 closes with the outer frame 14 of the freezer 10.
The catch basin 200 receives air or other type of gas and avoids
contact with the door 16. The air curtain unit 100 also includes a
continuous distributing channel 210 that moves the air received at
the catch basin 200 and distributes the air or other type of gas to
another location on the freezer 10 in order to create an air
curtain. The freezer 10 of the present disclosure would reduce the
amount of cold and warm air exchange that takes place during a door
16 opening of an ultra-low temperature freezer 10 with the air
curtain unit 100.
[0030] Referring to FIGS. 1 and 2, the catch basin 200 is just
below the door 16 and is fluidly connected to the distributing
channel 210. The distributing channel 210 can include a vertical
plenum 212 and horizontal plenum 214 being fluidly connected in a
single continuous unit. Other configurations of the distributing
channel can be made as long as the air or gas collected from the
catch basin 200 is redistributed to a different area of the cabinet
12 for generating the air curtain. The distributing channel 210
compresses the air received from the catch basin 100 and forwards
the air from the vertical plenum 212 to the horizontal plenum 214
for outputting the air curtain across the front of the cabinet
12.
[0031] Referring to FIGS. 1 through 4, the process of reducing
frost by an air curtain is shown in more detail as follows. As soon
as the door 16 opens, the denser air falls into a catch basin 200
at the bottom of the cabinet 12. The air is collected at the catch
basin 200 and recirculated through a distributing channel 210 from
the catch basin 200 through the vertical plenum 212 and finally to
the top part of the cabinet 12C at the horizontal plenum 214 of the
distributing channel 210.
[0032] Referring to FIG. 3, at the top of the cabinet 12C, the air
would be pushed out across the front of the cabinet 12 through the
distributing channel 210 forming an air curtain and thermal barrier
to incoming warmer air. The use of this cold air for the air
curtain would reduce the frost formation, as well as provide
quicker temperature recovery of the storage chamber 24 of the
cabinet 12 since the air falling to the bottom of the cabinet 12
would be replaced with cold recycled chamber air.
[0033] Referring to FIG. 4, the air drops to the catch basin 200
when the door 16 is opened, and the air is actively pushed by a
motor 230 (i.e., motor for a fan, blower or other means for
actively pushing the air) through the distribution channel 210 from
the catch basin 200. Other types of gases can also be used or mixed
in with the air. The distribution channel 210 can have a smaller
cross-sectional area for the flow of air than the catch basin 200
in order to compress the air. The compressed air goes through the
vertical plenum 212 and pushes up to the horizontal plenum 214. On
the horizontal plenum 214, the compressed air is pushed out through
outlets 216 on the bottom side of the horizontal plenum 214 of the
distribution channel 210. The outlets 216 can be, for example,
nozzles 218 as shown in FIG. 4A or plates 220 with an opening space
222 in between as shown in FIG. 4B to allow the air or other type
of gas to release. The airflow 400 pushes down to the catch basin
200 and recirculates.
[0034] The location of the distribution channel 210 of FIG. 4
accommodates after-market installation of the freezer 10. As seen
in FIGS. 1-3, the distribution channel 210 is positioned toward the
front of the freezer 10 and accommodates an efficient installation
with minimal steps. The after-market installation thus avoids being
limited to installation in the original manufacture of the freezer
10 and avoids expensive installation or expensive changes in the
assembly line.
[0035] Alternatively, instead of including the motor 230 to push
the air and be compressed in the distribution channel 210, a
compressed air source (not shown) can be added. Additionally, a
cold air filter (not shown) can be included in the distribution
channel 210 in order to separate out any foreign particles that may
fall into the catch basin through the grills and thereby prevent
the obstruction of the distribution channel 210. The air can
alternatively be pushed across horizontally from the vertical
plenum 212 of the distribution channel 210. The distribution
channel 210 can be a cylindrical shape hose construction,
rectangular construction or other configurations.
[0036] Referring to FIG. 4, the catch basin 200 can be configured
in a variety of configurations. The catch basin 200 can be extended
a certain distance from the cabinet 12 on a plane parallel with the
ground and toward the bottom portion of the freezer 10 and below
the cabinet 12 as seen in FIG. 2. Other configurations can be used,
including where the location of the catch basin 200 can be closer
to the ground or can be restricted to being below the cabinet 12
and above the refrigeration deck 300 or at the top portion of the
refrigeration deck 300. The refrigeration deck 300 includes, for
example, the compressor for the freezer 10. The catch basin 12 can
extend along the length of the bottom portion of the cabinet 12 and
just below the door 16, accommodating the closing of the door 16
with the cabinet 12. Alternatively, the catch basin 200 can extend
around only a portion of the bottom surface 12A of the cabinet 12.
Alternatively, the catch basin 200 can be a variety of shapes
including a rectangular shape along the length of the cabinet 12.
The catch basin 200 can be longer than the cabinet's length along
the bottom surface 12A of the cabinet 12.
[0037] Referring to FIG. 5, in another embodiment, the distribution
channel 510 can have a more tortured path than the path seen in
FIG. 1. The catch basin 200 is connected to the distribution
channel 510 that is embedded within the refrigeration deck 300 and
feeds along toward the back portion of the freezer 10, then up
toward the top portion of the freezer 10 and finally toward the
front of the freezer cabinet 12 that is attached to the door 16.
Other configurations of even more tortured path can be used. The
increased path of the distribution channel allows the air a greater
path in which to be compressed and thus providing greater pressure
in the air curtain.
[0038] The air curtain can be alternatively formed in the
horizontal direction as mentioned above, with an alternate
configuration of the distribution channel accommodating
recirculation of the air (not shown). The air curtain unit 100 can
also be split into two sections, where two air curtain units 100 of
FIG. 3 are arranged independently on both sides of the cabinet
12.
[0039] Referring to FIG. 6, in another embodiment, a smaller space
for the air curtain can be configured. For example, if the freezer
10 includes a first door 16A and a second door 16B, then the air
curtain would only run across the space of the door 16 that is
open. The distribution channel 610 would include a path not only on
the top portion of the cabinet 12, but also in between the first
and second doors 16A and 16B. The output from the middle plenum 616
and top horizontal plenum 614 would be switched according to the
opening of the doors 16A and 16B. Therefore, if the second door 16A
is opened, then only the open space is configured with an air
curtain as the air is outputted through the middle plenum 616 to
the catch basin 200. The pressure of the air can also be lower than
if it was to cover the larger space. Additionally, the air curtain
unit can collect the air failing through spaces between the inner
doors 16A and 16B. Additionally, the circulation path can be
shortened. Above the middle plenum 616 there can be a second catch
basin 202 that can shorten the circulation path when the first door
16A is opened. The distribution channel 610 can include valves or
other means (not shown) to accommodate the shortened circulation or
an alternate configuration. The catch basins 200 and 202 are
fluidly connected with the distribution channel 610. The blower
within the air curtain unit can include a smaller fan when the air
curtain is reduced as in FIG. 6.
[0040] In another embodiment, the cold air is pulled in and
compressed to form an air curtain as mentioned above. Rather than
using the distribution channel to compress the air, the air can be
already compressed through an active compressing device (not
shown).
[0041] In FIGS. 1-4, an illustration is made showing the
recirculation or distributing channel 210 going on the outside of
the cold space. However, referring to FIG. 7, a cross sectional
view of a freezer includes another embodiment. Rather than being
placed external to the frame 14 of the freezer 10 in FIG. 1, the
distributing channel 210 in FIG. 7 is embedded between the
insulation 702 and the evaporator 704 and within the frame 14 of
the freezer 700. In this embodiment, the distributing channel 210
may have a more tortured path as shown in connection with the
embodiment of FIG. 5. The location of the distributing channel 210
being placed between the insulation 702 and evaporator 704, and its
possible long tortured path, would allow the air that forms the air
curtain to be at the same or similar temperature as the evaporator
704. The reduction of warm moist air that enters the cabinet during
a door opening will reduce the amount of frost that forms and
extend the time span between defrosts or user removal of frost
build-up.
[0042] The many features and advantages of the invention are
apparent from the detailed specification, and thus, it is intended
by the appended claims to cover all such features and advantages of
the invention which fall within the true spirit and scope of the
invention. Further, since numerous modifications and variations
will readily occur to those skilled in the art, it is not desired
to limit the invention to the exact construction and operation
illustrated and described, and accordingly, all suitable
modifications and equivalents may be resorted to, falling within
the scope of the invention.
* * * * *