U.S. patent application number 13/677398 was filed with the patent office on 2013-07-04 for freezer evaporator 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 Ronald Wayne Jones.
Application Number | 20130167582 13/677398 |
Document ID | / |
Family ID | 48693749 |
Filed Date | 2013-07-04 |
United States Patent
Application |
20130167582 |
Kind Code |
A1 |
Jones; Ronald Wayne |
July 4, 2013 |
FREEZER EVAPORATOR APPARATUS
Abstract
An ultra low temperature freezer evaporator (ULT) apparatus that
has a triple feed capillary tube system. The ULT apparatus prevents
the low stage compressor from running in a vacuum. The invention
significantly reduces the "pull down" time. Further, the ULT
freezer evaporator apparatus significantly increases the transfer
area between the evaporator tubing and the contact surface on the
unit to assist the transfer of heat from the refrigerated unit
through the condenser to the surrounding room.
Inventors: |
Jones; Ronald Wayne; (New
Richmond, WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
STANDEX INTERNATIONAL CORPORATION; |
Salem |
NH |
US |
|
|
Assignee: |
STANDEX INTERNATIONAL
CORPORATION
Salem
NH
|
Family ID: |
48693749 |
Appl. No.: |
13/677398 |
Filed: |
November 15, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61581234 |
Dec 29, 2011 |
|
|
|
Current U.S.
Class: |
62/515 |
Current CPC
Class: |
F25B 5/02 20130101; F25D
23/061 20130101; F25B 41/067 20130101; F25B 2341/0661 20130101;
F25D 11/04 20130101; F25B 2500/01 20130101; F25B 39/028 20130101;
F25B 7/00 20130101 |
Class at
Publication: |
62/515 |
International
Class: |
F25B 39/02 20060101
F25B039/02 |
Claims
1. An ultra low temperature freezer evaporator apparatus having a
low stage compressor, said apparatus comprising; a triple feed
evaporator system having three predetermined equal lengths of
capillary tubing within three predetermined equal lengths of
evaporator tubing thus providing three evaporator sections, each
evaporator section having a compressor end and a raceway end; a
freezer cabinet with five freezer liner walls having a top wall,
left side wall, right side wall, back side wall, and bottom wall
wherein said triple feed evaporator system is attached thereto with
one evaporator section attached to the back freezer liner wall,
another evaporator section attached to top and left side freezer
liner walls, and the third evaporator section attached to the right
and bottom side freezer liner walls, wherein said triple feed
capillary system prevents the low stage compressor from running in
a substantial vacuum and said apparatus having a significantly
reduced "pull down" time.
2. The ultra low temperature freezer evaporator apparatus of claim
1 wherein said evaporator tubing is approximately 3/8 inch copper
tubing and the capillary tubing has a diameter of approximately
0.036 inches.
3. The ultra low temperature freezer evaporator apparatus of claim
1 wherein said triple feed evaporator system is attached to said
freezer liner walls using aluminum tape.
4. The ultra low temperature freezer evaporator apparatus of claim
1 wherein said triple feed evaporator system is attached to said
freezer liner walls such that each of said three sections is
attached either level or slightly sloping downhill to aid in a
refrigerant/oil that is filled from the top of said apparatus to
flow downhill thereby facilitating the return of the
refrigerant/oil to return to the low stage compressor thus
resulting in a down feed design.
5. The ultra low temperature freezer evaporator apparatus of claim
1 wherein two evaporator sections are mirror images of one
another.
6. The ultra low temperature freezer evaporator apparatus of claim
1 further comprising a manifold wherein each compressor end of said
three evaporator sections are connected thereto and wherein said
manifold leads back to the low stage compressor.
7. The ultra low temperature freezer evaporator apparatus of claim
1 further comprising: a raceway wherein each raceway end of said
three evaporator sections are connected thereto: a distributor
connected to said raceway which delivers refrigerant/oil to said
raceway.
8. The ultra low temperature freezer evaporator apparatus of claim
1 wherein the triple feed capillary system increases the contact
area between the freezer liner wall and the evaporator tubing by
eliminating the necessity of rounding evaporator tubing around the
corners of said freezer liner walls when using a single length of
evaporator tubing.
Description
[0001] This application claims benefit of U.S. Provisional
Application Ser. No. 61/581,234 filed Dec. 29, 2011, pursuant to 35
USC .sctn.119(e).
FIELD OF THE INVENTION
[0002] This invention relates to ultra low temperature freezer
units, in particular, ultra low temperature (ULT) freezers that
have an improved evaporator with an improved capillary feed system
on the low stage compressor assembly.
BACKGROUND OF THE INVENTION
[0003] Ultra low temperature (ULT) freezers are typically designed
to store and protect critical biological materials. Minus
86.degree. C. freezers are a common product produced by several
manufacturers. This type of freezer as well as other ULT freezers
operating at even colder temperatures is used for the storage of
blood component additives, bone marrow, insect cell culture,
mammalian cell culture, nucleic acids (DNA/RNA), sperm, fertilized
ova, tissues and viruses.
[0004] Referring to FIGS. 1 and 2, a typical prior art ULT freezer
80 has one long continuous run of evaporator tubing 20 fed by one
extremely long piece (preferably more than 20 feet in length) of
capillary tube 22. Such a tube 22 is typically 0.036 inches in
diameter. Evaporator tube 20 is typically a 3/8 inch copper
tube.
[0005] This single length of capillary tube 22 causes the suction
pressure of the low stage compressor to run in a substantial
vacuum. This vacuum can cause accelerated wear and tear on the
crankshaft and connecting rod. In turn, this will drive up the
compression ratio of the compressor. Thus, a higher compression
ratio can result in the compressor to be running at a pressure
exceeding the compressor manufacturer's recommended operating
envelope. Of course, operating in such a manner is likely to
adversely affect the reliability of the compressor. Further, the
flow rate of the refrigerant is reduced in a negative manner.
Consequently, longer "pull down" times (the time required for the
unit to reach the desired temperature) are experienced. This
requires the compressor to run longer as well thus reducing the
lifespan of the unit and also increasing operating costs.
[0006] As shown in FIG. 3, a lot of transfer area 28, that is,
between the contact surface 24 and tube 20, is reduced when
evaporator tube 20 is routed around corners 26. Therefore, this
design requires a greater amount of time to absorb the heat from
inside the unit and transfer this heat from the condenser to the
surrounding room. This will also increase the time the compressor
must run and increases operating cost.
[0007] There is no ULT freezer unit presently available that solves
the problems noted above.
SUMMARY OF THE INVENTION
[0008] It is an aspect of the invention to provide an ULT freezer
evaporator apparatus that has a triple feed capillary tube
system.
[0009] It is another aspect of the invention to provide an ULT
freezer evaporator apparatus that prevents a low stage compressor
from running in a vacuum.
[0010] Another aspect of the invention is to provide an ULT freezer
evaporator apparatus that significantly reduces the "pull down"
time.
[0011] Finally, it is still another aspect of the invention is to
provide an ULT freezer evaporator apparatus that significantly
increases the transfer area between the evaporator tubing and the
contact surface on the unit to assist the transfer of heat from the
refrigerated unit through the condenser to the surrounding
room.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is an isometric rear view of a prior art freezer
illustrating the evaporator tubing configuration in place on the
freezer unit.
[0013] FIG. 2 is a detailed isometric view of the area of
evaporator tubing identified in FIG. 1 as area "B".
[0014] FIG. 3 is a detailed side view of evaporator tubing
identified in FIG. 1 as area "C".
[0015] FIG. 4 is a left top isometric view illustrating the
evaporator tubing configuration in place on the freezer unit in
accordance with the invention.
[0016] FIG. 5 is a right bottom isometric view illustrating the
evaporator tubing configuration in place on the freezer unit in
accordance with the invention.
[0017] FIG. 6 is a detailed isometric view of capillary tubes 22A,
22B, and 22C brazed into their respective evaporator tubes 20A,
20B, and 20C indentified in FIG. 4 as area "D".
[0018] FIG. 7 is a detailed isometric view of distributor 32 with
capillary tubes 22A, 22B, and 22C leading into raceway 30
identified in FIG. 4 as area "A".
[0019] FIG. 8 is a schematic of the invention used with a preferred
ULT freezer evaporator apparatus.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Referring now to FIG. 8 where invention 10 is shown in
combination with a typical ULT freezer such as manufactured by
Nor-Lake, a Wisconsin Company. This freezer is a two-stage
compressor system as shown. This unit is powered by a low noise,
high performance cascade refrigeration system using two 1
Horsepower hermetically sealed compressors 40, 50. The high stage
compressor 40 is an Emerson Model No. RFT42CIE-PFV for 230-volt
units or the RFT42CIE-PFA for the 115-volt unit. The low stage
compressor 50 is also made by Emerson using the same model as
above.
[0021] When the freezer sensor units call for cooling, high stage
compressor 40 runs by itself until heat exchanger 42 reaches a
temperature of -34 degrees Centigrade. At that time, the controller
will start low stage compressor 50 to run with the high stage. The
low stage refrigerant will begin to circulate through oil separator
56, downstream to heat exchanger 42 and through filter dryer 60
then to distributor 32 where the refrigerant will be dispersed
evenly into three equal length sections 13, 14 and 15 of evaporator
invention 10 with each section having capillary tubes 22A, 22B, and
22C inside copper tubing 20A, 20B, and 20C, respectively.
[0022] The capillary tubes 22A, 22B, and 22C are of a predetermined
diameter and length to cause a predetermined temperature/pressure
drop of the refrigerant as it reaches the 3/8 copper tubing 20A,
20B, and 20C that is attached to freezer liner 12. In the example
shown in FIG. 8, once the refrigerant is at the evaporator
invention 10, the refrigerant will start to absorb heat from the
interior of the invention 10 through the freezer liner walls
12.
[0023] The three-piece evaporator invention 10 is attached to
freezer liner walls 12 with aluminum tape (not shown) to provide
better heat transfer. Care must be taken to attach evaporator 10
either level or slightly sloping downhill to aid in refrigerant/oil
to return to low stage compressor 50. Refrigerant is fed at the top
of the freezer cabinet providing a down feed design, thus letting
gravity assist the refrigerant/oil back to compressor 50.
[0024] Two sections of evaporator invention 10 are mirror images of
each other. FIG. 4 shows evaporator sections 14 and 15. The third
section (13) of evaporator invention 10 is shown in FIG. 5 as well
as section 14 again. Thus, FIG. 4 shows the back (14), top and left
side (15) of the freezer box which corresponds to sections 14 and
15. FIG. 5 shows the bottom, right (13) and again the back (14) of
the freezer box which corresponds to sections 13 and 14. Note that
the door of the freezer box 80 (in direction 35) is not shown.
[0025] The back section 14 is adjusted by reducing the radius of
the turns to achieve the same length as the other two sections 13
and 15. The three-evaporator sections tees into a manifold 34, then
back to the compressor 50 as shown FIG. 8.
[0026] As shown in FIG. 6, capillary tube 22A is brazed into
evaporator tube 20A; capillary tube 22B is brazed into evaporator
tube 20B; and finally capillary tube 22C is brazed into evaporator
tube 20C to form evaporator sections, 13, 14, and 15
respectively.
[0027] As shown in FIG. 7, low stage distributor 32 provides
refrigerant in direction 36 up raceway 30 where it is split into
the three-evaporator sections 13, 14, and 15 as shown in FIGS. 4
and 5.
[0028] The use of evaporator invention 10 provides an accelerated
"pull down" by providing increased contact area. In fact, when the
inventor tested a similar freezer model without evaporator
invention 10, it was found that runtime was approximately 40% less
to go from ambient temperature to -80 degrees Centigrade.
[0029] The high capacity air-cooled condenser 49 features rifled
tubing. Having rifled tubing will spin the refrigerant to keep more
liquid against the tubing walls for improved heat rejection to the
surrounding environment.
[0030] Again, referencing FIG. 8, the high stage compressor starts
and refrigerant exits compressor 40 through the discharge line to
the heat exchanger suction accumulator 44. Part 44 has both low and
high temperature refrigerant entering in the dome of the canister.
The hot gas makes a couple of passes in 3/8'' tubing inside the
canister to boil off any liquid that might be present from the
return gas. This heat exchange is to prevent any liquid from
entering compressor 40 and causing damage to the bearing surfaces.
The refrigerant exits part 44 and travels to condenser 49 where
cooler air is drawn across it to lower the temperature of the
refrigerant and condense it. Now the liquid refrigerant exits
condenser 49 and enters filter drier 48 where particles and
moisture are filtered from the refrigerant. The refrigerant enters
capillary tube 47 and achieves the right temperature/pressure drop
then onward to heat exchanger 42 to absorb heat from the low stage
circuit. The refrigerant exits and makes a pass through heat
exchanger suction accumulator 44 to boil off any liquid before
entering compressor 40 where the refrigerant is drawn into the
combustion chamber. Heat of compression will add heat and raise the
pressure of the refrigerant where it exits through the discharge
line and the cycle will start again.
[0031] The low stage compressor 50 will start once heat exchanger
temperature reaches -34.degree. c. The refrigerant passes through
oil separator 56 where the oil is retained through a coalescing
filter and falls to the bottom of oil separator 56. The filtered
refrigerant exits and enters heat exchanger 42 where heat is
rejected to the high stage circuit. The refrigerant exits and
enters filter drier 60 where particles and moisture are filtered
from the refrigerant. The refrigerant now enters distributor 32
where the pressure evenly disperses the refrigerant into capillary
tubes 22A, 22B and 22C to achieve the right temperature/pressure
drop and then onward to evaporator sections 13, 14 and 15. Here the
refrigerant will absorb heat from conditioned area 12. The
refrigerant enters manifold 34 and returns to low stage compressor
50 where the refrigerant is drawn into the combustion chamber. Heat
of compression will add heat and raise the pressure of the
refrigerant where it exits through the discharge line and the cycle
will start again. Both compressors will run until the cabinet
sensor is satisfied.
[0032] 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.
* * * * *