The present invention is directed to refrigeration systems particularly for scientific applications, such as, vaccine storage (requirement parameters as defined in the NSF 456-2021 standard), lab specimens, pharmaceuticals, materials testing, blood products storage in addition to commercial and food service applications and other related applications.
In scientific refrigeration applications, two important performance parameters used to characterize temperature variation within a refrigerated or environmentally controlled system are temperature stability and temperature uniformity. Temperature stability, as utilized herein, is defined as the largest temperature difference experienced at a single point among all measured points in the refrigerated chamber over a period of time. Temperature uniformity, as utilized herein, is defined as the maximum variation of temperature experienced across all points in the refrigerated chamber at any single point in time during the testing period. In most scientific refrigeration designs, where acceptable operating temperature ranges are generally between 1° C. and 10° C., the airflow coming off the evaporator (cooled air, potentially as low as −10° C. exits the evaporator) is distributed in a diffuse manner, generally directed down the rear wall of the refrigerator opposite the door. In this configuration, the intake fan is generally placed in front of the evaporator and draws air from the front portion of the refrigerator exacerbating the naturally occurring airflow over the warmest surface in the chamber, the door inner wall or inner glass surface in the case of a glass door. This has a number of negative effects on the stability and uniformity of the refrigerated chamber creating a general gradient where the volume at the front-top portion of the chamber remains warmer, the volume directly in the evaporator exhaust remains very cold, and cold air accumulation in the bottom volume of the chamber, as well as other detrimental temperature gradient effects. In addition, since the air exhaust and intake are typically closely located, there can be a high level of recirculation that reduces the overall temperature uniformity. Also, to be considered is the effect of product loading that can block airflow or directly, further exacerbating the above-mentioned detrimental effects and expose product to very cold or very warm regions. Design attempts to better distribute the air utilize plenums in the exhaust path to direct air further into the chamber before exhausting into the chamber. This approach can achieve minor improvements but in general, simply moves the distribution of very cold air while potentially exacerbating the overall temperature variation within the chamber.
It is not found in the prior art a method for creating a circulating envelope of air exhausting from the front, upper portion of the refrigerator that utilizes intrinsic properties of the refrigerator construction to create a stable thermal environment with superior heat capacity utilization, significant reduction of recirculation effects and significant improvement in stability and uniformity performance both in loaded and unloaded situations. It is common, that in order to hold tighter temperature stability and uniformity in systems employing conventional compressors (non-proportional), that the time between cycles must be reduced as a function of the desired minimum and maximum temperature selected. This design best utilizes heat capacity of the refrigerator components in addition to optimization of residual latent heat in the phase change of refrigerant remaining in the evaporator after a refrigeration cycle has ended and the compressor shuts off.
A refrigeration system and refrigeration method that show one or more improvements in comparison to the prior art would be desirable in the art.
The refrigeration system according to the present disclosure provides methodology different than known refrigeration systems for handling airflow, moderating typically warmer volumes, enveloping the refrigerated chamber in a more consistent distribution of homogenized air with the aggregate effect resulting in a system that achieves better stability and uniformity, reducing compressor cycles per day while utilizing conventional compressors at common evaporator temperatures.
In an exemplary embodiment, a refrigeration system is provided. The refrigeration system includes a storage chamber configured to store a product at a predetermined temperature. The storage chamber is defined by an inner wall. The inner wall at least partially defines an air plenum. The inner wall includes an opening wall surface, a floor surface, a rear wall surface and a ceiling wall surface. The system also includes a refrigerant circuit including a compressor, a condenser, a condenser fan, an evaporator and an evaporator fan arranged and disposed in an operable configuration to provide refrigeration to the storage chamber. The air plenum includes a conduit arranged and disposed to convey air from an air inlet across the evaporator and into a discharge chamber and out an air outlet. The air outlet is configured to discharge cooled air in a direction toward the opening wall surface.
In an exemplary embodiment, a method for operating a refrigeration system is provided. The method includes providing a storage chamber to store a product at a predetermined temperature, the storage chamber defined by an inner wall. The inner wall at least partially defines an air plenum. The inner wall includes an opening wall surface, a floor surface, a rear wall surface and a ceiling wall surface. A refrigerant circuit is provided that includes a compressor, a condenser, a condenser fan, an evaporator and an evaporator fan arranged and disposed in an operable configuration to provide refrigeration to the storage chamber. Air is conveyed from an air inlet, in the air plenum, across the evaporator and into a discharge chamber and out an air outlet. The air outlet is configured to discharge cooled air in a direction toward the opening wall surface.
In another exemplary embodiment, the air plenum arrangement and storage chamber are arranged and disposed to provide an enveloping airflow that travels from the air outlet of the air plenum along the opening wall surface, across the floor surface and into the air inlet of the air plenum.
Another aspect of this invention is greatly improved homogenization of ejected air. Temperature variation of the air passing over the evaporator is greatly reduced due to mixing forced in volumes where product cannot be stored.
Yet another aspect of this invention is the temperature moderation of ejected air at the exhaust. The temperature of the air passing over the evaporator is moderated and leaves the plenum at a temperature closer to the chamber temperature than it would otherwise.
Still another aspect of the invention is the cold surface cooling (as opposed to direct convective cooling) of upper storage chamber volume. The discharge chamber and upper surface of the storage chamber are cold due to the air coming directly from the evaporator fan. This cools the upper portions of the chamber via free convection and heat transfer directly from the plenum wall surface. This is important because the upper portions of a refrigerated chamber typically stay warmer than the mid and lower portions since warmer air naturally rises. This, in turn, improves chamber stability and uniformity in comparison to systems without this type of plenum.
Additionally, another aspect of this invention is the transient heat absorption effect due to the greater relative plenum area and inherent thermal mass of the surrounding plenum components combined with the interior walls of the refrigerator. Again, this serves to improve chamber stability and uniformity in comparison to systems without this type of air plenum.
Another important aspect of embodiments of the present disclosure is the relative elongation of the refrigeration system's intrinsic operating cycle period, resulting in fewer compressor starts per day required to maintain a defined differential. This is achieved without reducing the energy efficiency of the unit.
Also, a benefit of this invention is the enveloping of the product storage volume between a rear wall and a downward flow of cooling air at the front along the opening. Unlike conventional configurations, the front is cooled first rather than the rear and the air plenum provides an additional insulating effect further homogenizing temperature distribution.
Also, a benefit of this invention is the positive impact from the effective capacitive thermal mass heat exchange effect due to the enveloping circulation and the utilization of a greater portion of the refrigerator thermal mass after active refrigeration ceases. This works to continue passive cooling, moderate and slow temperature rise in the product chamber due to heat infiltration ultimately extending cycle times in comparison to conventional configurations, improving relative stability and uniformity without decreasing energy efficiency.
Importantly impacted by this invention is the time required to recover to the normal chamber operating ranges after long and short door openings. This is greatly enhanced due to the enveloping of the chamber, the increased effective capacitive thermal mass and the directed outlet and intake locations which counter the typical temperature gradient (driven by natural convection of warmer air) experienced in a refrigerated chamber.
Additionally, this invention reduces or eliminates the most common warm areas towards the front of the unit substantially impacting system stability and uniformity performance.
Important to this invention is the ability to maintain tight control of temperature variation using only conventional compressor systems vs. variable speed type compressor systems. The positive impact on the temperature variation is further improved by when variable speed type compressors are utilized.
Other features and advantages of the present invention will be apparent from the following more detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts.
Provided is a refrigeration system that provides a benefit of exhausting air in a direction to the front of the unit rather than the rear and downwards causing the system to operate in a fundamentally different way because there is more room for air mixing, product cannot be positioned to block airflow and in turn temperature homogenization is improved.
The refrigeration system according to the present disclosure relates generally to the field of refrigeration for the storage of vaccines, blood products, food products, lab specimens and any application that requires tightly controlled temperature stability and uniformity. Temperature stability is defined as the largest temperature gradient experienced at a single point in the refrigerated chamber over a period of time. Temperature uniformity is defined as the maximum temperature experience across all points in the refrigerated chamber at any point in time during the testing period.
The disclosed method utilizes a novel air handling plenum that leverages intrinsic properties of the thermal system and construction to greatly improve the product chamber temperature uniformity and stability in comparison to systems with non-critical plenum designs or without plenums. Although this system manages airflow with an air plenum that specifically directs airflow, it is the novel leveraging of the entire thermal system and construction that achieves the performance improvements.
Important to the benefits provided by embodiments of the refrigeration system according to the present disclosure is the partial envelopment of the product chamber improving the uniformity and stability of the air temperature. The differentiators significantly impact the product chamber uniformity and stability parameters.
Embodiments of the present disclosure result in configurations that function in a superior way in comparison to all other known methodologies of homogenizing and stabilizing air temperatures employed in conventional (non-proportional) compressor driven, vapor cycle refrigeration systems. Such systems, employed in medical, pharmaceutical, food service and industrial applications generally rely on the same basic configuration and all have some measure of the issues inherent to such configurations.
Unlike the system shown in
The inner wall 201 includes an opening wall surface 205, a floor surface 207, a rear wall surface 209 and a ceiling wall surface 211 all of which provide surfaces that bound the storage chamber 107. The air plenum 203 formed by the inner wall 201 corresponding to the rear wall surface 209 and the ceiling wall surface 211 conveys air from an air inlet 213 to an air outlet 215 across the evaporator 101 and the evaporator fan 111. The evaporator fan 111 in the embodiment of
The configuration of refrigeration system 100 provides an air inlet 213 at the bottom of the storage chamber 107 causing an airflow that is counter to the natural convection of warmer air greatly enhancing uniformity though active mixing and counterflowing of cold and warm air currents. In one embodiment, the air inlet 213 intakes air through a plurality of vents in the bottom, rear of the storage chamber 107. In an exemplary embodiment, the distance from the celling wall surface 211 to the single or plurality of air inlet return openings 213 is two thirds to four fifths the height of the product storage chamber 107. In alternative embodiments, there is a step construction in the back wall of the product storage chamber 107 and the distance from the celling wall surface 211 to the single or plurality of air inlet return openings 213 is one half the height of the product storage chamber 107. In addition, the embodiments of the present disclosure eliminate the ejection of cold air along the back wall to the bottom of the chamber where the cold exiting air reinforces the cold air naturally residing at the back rear of the unit. The conventional rear, downward cold air ejection exacerbates the naturally cold regions (colder air naturally falls). This elimination, as is present in the embodiments of the present disclosure, serves to better homogenize the temperature distribution within the chamber. In addition, the embodiments of the present disclosure direct air from the top, front of the chamber to the bottom portion of the rear of the chamber homogenizing temperature variances in the storage chamber 107. This greatly reduces unwanted recirculation effects common in conventional configurations that limits air exchange in the lower volumes, particularly when the chamber is loaded with product. In one embodiment, the air outlet 215 ejects air forward towards the opening 115 of the refrigeration system 100 though a plurality of vents at the top of the chamber no farther than 12 inches from the door and no closer than ½ inch from the opening 115.
Also shown in
Embodiments of the present disclosure are adaptable and retrofittable to common, conventional refrigerator configurations via reversal of flow direction and incorporation of inner wall 201 components to form an air plenum on systems having an evaporator located in the top and ejecting air down the rear wall.
The arrangement according to the present disclosure, as exemplified in
In addition, the arrangement according to the present disclosure, as exemplified in
While the invention has been described with reference to one or more embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. In addition, all numerical values identified in the detailed description shall be interpreted as though the precise and approximate values are both expressly identified.
This application is a non-provisional continuation patent application claiming priority and benefit of U.S. Non-Provisional patent application Ser. No. 17/588,463, file Jan. 31, 2022, entitled “REFRIGERATION SYSTEM WITH ENVELOPING AIR CIRCULATION AROUND PRODUCT CHAMBER”, currently pending, which is hereby incorporated by reference in its entirety.
Number | Name | Date | Kind |
---|---|---|---|
8966929 | Rafalovich et al. | Mar 2015 | B2 |
9285153 | Contreras LaFaire et al. | Mar 2016 | B2 |
20010047660 | Mashburn et al. | Dec 2001 | A1 |
20040139763 | Jeong | Jul 2004 | A1 |
20060202596 | Bauer | Sep 2006 | A1 |
20090019881 | Rafalovich et al. | Jan 2009 | A1 |
20120060526 | May | Mar 2012 | A1 |
20150260448 | Avila | Sep 2015 | A1 |
20160169578 | Linney, II | Jun 2016 | A1 |
20170074568 | Orozco | Mar 2017 | A1 |
20170261250 | Cho et al. | Sep 2017 | A1 |
20190017740 | Fei | Jan 2019 | A1 |
20200278136 | Olivani et al. | Sep 2020 | A1 |
Number | Date | Country |
---|---|---|
1258838 | Jul 2000 | CN |
1258838 | Jul 2000 | CN |
2988081 | Feb 2016 | EP |
2988081 | Feb 2016 | EP |
Entry |
---|
Pdf is original document of foreign reference EP 2988081 A1 (Year: 2016). |
Pdf is translation of foreign reference CN 1258838 A (Year: 2000). |
Pdf is translation of foreign reference EP 2988081 A1 (Year: 2016). |
Number | Date | Country | |
---|---|---|---|
20230341169 A1 | Oct 2023 | US |
Number | Date | Country | |
---|---|---|---|
63147466 | Feb 2021 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 17588463 | Jan 2022 | US |
Child | 18216708 | US |