An air cooling and control system for a refrigerated food merchandiser having an insulated cabinet with a product area having adjacent product zones, plural modular evaporator coil sections of substantially equal heat exchange potential and being of predetermined length and arranged in horizontal, spaced, end-to-end predetermined disposition and separate air moving means associated with each coil section and a corresponding product zone for circulating separate air flows through the coil sections and to the product area for cooling. The system further includes a first refrigerant metering valve for controlling liquid refrigerant flow on the high side of the evaporator sections, and a second refrigerant metering valve for controlling suction pressure and refrigerant vapor flow on the low side of the evaporator sections. An electronic control senses exit air temperatures downstream of the evaporator sections and operates the second metering valve in response thereto. In another aspect, a method of operating an electronic evaporator pressure regulating (EEPR) valve during the refrigeration and defrost modes of the controlled evaporator and in response to sensed air temperatures .
|
0. 45. A method of controlling the exit air temperature from the evaporator coil in a commercial refrigerated merchandiser for food products, in which the evaporator coil has a refrigeration mode and a defrost mode, said control method comprising the steps of:
(a) providing an electronic evaporator pressure regulator (EEPR) valve actuated by a stepper motor operated by a valve controller circuit, (b) sensing the exit air temperature from the evaporator coil and generating a signal corresponding thereto; (c) operating the stepper motor in response to said signal to move the EEPR valve during the refrigeration mode of the evaporator coil for modulating refrigerant vapor flow therethrough to maintain a preselected exit air temperature (d) operating the stepper motor to a predetermined position of the EEPR valve in the defrost mode.
15. An air cooling system in a commercial refrigerated merchandiser having an insulated cabinet with a product zone, comprising:
evaporator means having a refrigeration mode and being constructed and arranged for cooling air within the cabinet to achieve a preselected exit air temperature down stream thereof, liquid refrigerant metering means for controlling the flow of liquid refrigerant to the high side of said evaporator means, for circulating air flow through said evaporator means and said product zone; and other refrigerant metering means constructed and arranged on the low side of said evaporator means for controlling the suction pressure thereof, said other metering means comprising evaporator pressure regulating (EEPR) valve means for modulating the refrigerant vapor flow from said evaporator means, and means for sensing exit air temperatures downstream of said evaporator means, and controller means responsive to said sensing means for operating said EEPR valve means in the refrigeration mode and in a defrost mode.
0. 52. A method of controlling the flow of liquid refrigerant through an evaporator coil in a commercial refrigerated merchandiser for food products, in which the evaporator coil has a refrigeration mode and a defrost mode and a low side of the evaporator coil has an electronic evaporator pressure regulator (EEPR) valve operated by a valve controller circuit, said control method comprising the steps of:
(a) maintaining exit air temperature in the refrigeration mode at a set point by modulating the EEPR valve in response to sensed exit air temperature from the evaporator coil, (b) monitoring the position of the EEPR valve, (c) timing a preselected period following the onset of operation of the EEPR valve in the refrigeration mode, the time period being selected to permit the valve to substantially stabilize in a position which maintains the exit air temperature at the set point, (d) storing a reference position of the EEPR valve at the end of the preselected period, (e) entering the defrost mode by closing the EEPR valve, (f) setting the EEPR valve at the stored reference position at the conclusion of the defrost mode upon entry into the refrigeration mode.
17. The method of controlling the exit air temperature from the evaporator coil in a commercial refrigerated merchandiser for food products, in which the evaporator coil has a refrigeration mode and a defrost mode and the suction side of the evaporator coil has an electronic evaporator pressure regulator (EEPR) valve operated by a valve controller circuit, said control method comprising the steps of:
(a) sensing the exit air temperature from the evaporator coil and generating a signal corresponding thereto; (b) operating the EEPR valve in the refrigeration mode of the evaporator coil by modulating refrigerant vapor flow therethrough to maintain a preselected exit air temperature; (c) operating the EEPR valve in the defrost mode of the evaporator coil, (1) by first closing the EEPR valve during a preselected de-icing period of said evaporator coil until reaching a predetermined drip temperature, and (2) then activating the valve controller circuit in response to detection of exit air temperatures exceeding a preselected value during a final drip period to provide limited refrigeration to maintain the preselected temperature during the remainder of the defrost mode. 7. An air cooling system in a commercial refrigerated merchandiser having an insulated cabinet with a product area having horizontally adjacent product zones for the display and marketing of food products, said system comprising:
modular evaporator means having a plurality of separate coil sections of substantially equal size and heat exchange capability, said plural coil sections having a preselected length and being horizontally disposed in spaced apart, end-to-end orientation relative to each other in said cabinet; liquid refrigerant metering means for controlling the inlet flow of liquid refrigerant on the high side of said modular evaporator means; said plural coil sections of said modular evaporator means being constructed and arranged in parallel refrigerant flow relationship with each other and in series flow relationship with said liquid refrigerant metering means, and all of said coil sections having an operative cooling mode at the same time and an inoperative defrost mode at the same time; and separate air moving means associated with the respective coil sections for circulating separate air flows through said coil sections and discharging the air flows to the adjacent product zones for cooling.
0. 39. An air cooling system in a commercial refrigerated merchandiser having an insulated cabinet with a product zone, comprising:
evaporator means having a refrigeration mode and being constructed and arranged for cooling air within the cabinet to achieve a preselected exit air temperature downstream thereof, liquid refrigerant metering means for controlling the flow of liquid refrigerant to the high side of said evaporator means, means for circulating air flow through said evaporator means and said product zone; and other refrigerant metering means constructed and arranged on the low side of said evaporator means for controlling the suction pressure thereof, said other metering means comprising evaporator pressure regulating (EEPR) valve means for modulating the refrigerant vapor flow from said evaporator means, said EEPR valve means including an EEPR valve and a stepper motor for actuating said EEPR valve to modulate the low side refrigerant vapor flow, means for sensing exit air temperatures downstream of said evaporator means, and controller means responsive to said sensing means for operating the stepper motor to actuate said EEPR valve in the refrigeration mode and in a defrost mode of the air cooling system.
1. An air cooling system in a commercial refrigerated merchandiser having an insulated cabinet with a product area having a least two horizontally adjacent side-by-side product zones for the display and marketing of food products, said system comprising:
modular evaporator means having at least two separate coil sections of preselected length and heat exchange capability, said coil sections being horizontally disposed with their adjacent ends in spaced apart, end-to-end orientation relative to each other in said cabinet; liquid refrigerant metering means for controlling the inlet flow of liquid refrigerant on the high side of said modular evaporator means; said plural coil sections of said modular evaporator means being constructed and arranged in parallel refrigerant flow relationship with each other to receive liquid refrigerant from said liquid refrigerant metering means, and all of said coil sections having an operative cooling mode at the same time and an inoperative defrost mode at the same time; and separate air moving means associated with the respective coil sections for circulating separate air flows through said coil sections and being constructed and arranged with air flow passageways in said cabinet for discharging the air flows in side-by-side relationship to the horizontally adjacent side-by-side product zones for cooling.
22. An air cooling system for a commercial refrigerated merchandiser having an insulated cabinet with a product area having at least two horizontally adjacent product zones for the display and marketing of food products, said system comprising:
modular evaporator means having at least two separate coil sections of predetermined size and heat exchange capability, said coil sections being horizontally disposed with their adjacent ends in spaced apart orientation with each other and each coil section being operatively associated with one of the product zones for the refrigeration thereof; first refrigerant metering means for controlling the inlet flow of liquid refrigerant to the high side of said modular evaporator means; said plural coil sections of said modular evaporator means being constructed and arranged in parallel refrigerant flow relationship with each other to receive liquid refrigerant from said liquid refrigerant metering means, and all of said coil sections having an operative cooling mode at the same time and an inoperative defrost mode at the same time; and separate air moving means associated with the respective coil sections for circulating separate air flows through said coil sections and being constructed and arranged with separate air flow passageways in said cabinet for discharging the air flows to the horizontally adjacent product zones for cooling.
31. In combination with a commercial refrigerated merchandiser having an insulated cabinet with a product area having at least two horizontally adjacent product zones of predetermined length for the display and marketing of food products, a refrigeration system comprising:
modular air cooling and circulating means having at least two separate evaporator coil sections of predetermined heat exchange capability, each coil section having elongated coil tubing of preselected length corresponding substantially to the length of an associated one of said product zones, and further having separate air moving means for the circulation of refrigerating air flow across each of the respective coil sections; liquid refrigerant metering means for controlling the inlet flow of liquid refrigerant to the high side of said coil sections; said coil sections of said modular air cooling means being constructed and arranged in parallel refrigerant flow relationship with each other to receive liquid refrigerant from said liquid refrigerant metering means, and all of said coil sections having an operative cooling mode at the same time and an inoperative defrost mode at the same time; and said modular air cooling and circulating means being constructed and arranged in said insulated cabinet with each coil section and its air moving means being in operative relationship with its associated product zone for the circulation of separate air flows through the coil sections and the discharge of such air flows separately to the adjacent product zones for cooling.
0. 53. An air cooling system in a commercial refrigerated merchandiser having an insulated cabinet with a product zone, comprising:
evaporator means having a refrigeration mode and being constructed and arranged for cooling air within the cabinet to achieve a preselected exit air temperature downstream thereof, liquid refrigerant metering means for controlling the flow of liquid refrigerant to the high side of said evaporator means, means for circulating air flow through said evaporator means and said product zone; and other refrigerant metering means constructed and arranged on the low side of said evaporator means for controlling the suction pressure thereof, said other metering means comprising evaporator pressure regulating (EEPR) valve means for modulating the refrigerant vapor flow from said evaporator means, said EEPR valve means including an EEPR valve and a stepper motor for actuating said EEPR valve to modulate the low side refrigerant vapor flow including means for sensing exit air temperatures downstream of said evaporator means, and controller means responsive to said sensing means for operating the stepper motor to actuate said EEPR valve in the refrigeration mode and in a defrost mode of the air cooling system, the stepper motor being constructed and arranged to move the EEPR valve through a predetermined number of incremental steps to a new position for affecting the exit air temperature in response to said means for sensing exit air temperature upon receiving a signal from said controller means, said controller means being constructed and arranged to control the stepper motor for moving the EEPR valve in the refrigeration mode so that the EEPR valve always approaches the new position from the same direction.
2. The air cooling system of
3. The air cooling system of
4. The air cooling system of
5. The air cooling system of
6. The air cooling system of
8. The air cooling system of
9. The air cooling system of
10. The air cooling system of
11. The air cooling system of
12. The air cooling system of
13. The air cooling system of
14. The air cooling system of
16. The air cooling system of
18. A control method as set forth in
(1) monitoring the position of the EEPR valve, (2) timing a preselected period following the onset of operation of the EEPR valve in the refrigeration mode, the time period being selected to permit the valve to substantially stabilize in a position which maintains the exit air temperature at a set point, (3) saving a reference position of the valve at a time when the preselected period is timed out.
19. A control method as set forth in
(d) operating the EEPR valve in the pull down mode of the evaporator coil, (1) by first moving the EEPR valve to its full open position, (2) holding the EEPR valve in its full open position until the preselected exit air temperature is detected. 20. A control method as set forth in
(3) setting the EEPR valve at the valve reference position stored in the valve controller during operation of the EEPR valve in the refrigeration mode.
21. A control method as set forth in
(d) operating the EEPR valve in the pull down mode of the evaporator coil, (1) by first moving the EEPR valve to its full open position, (2) holding the EEPR valve in its full open position until the preselected exit air temperature is detected.
23. The air cooling system of
24. The air cooling system of
25. The air cooling system of
26. The air cooling system of
27. The air cooling system of
28. The air cooling system of
29. The air cooling system of
30. The air cooling system of
32. The refrigerated merchandiser of
33. The refrigerated merchandiser of
34. The refrigerated merchandiser of
35. The refrigerated merchandiser of
36. The refrigerated merchandiser of
37. The refrigerated merchandiser of
38. The refrigerated merchandiser of
0. 40. The air cooling system of
0. 41. The air cooling system of
0. 42. The air cooling system of
0. 43. The air cooling system of
0. 44. The air cooling system of
0. 46. The method of
(a) monitoring the position of the EEPR valve during the refrigeration mode, (b) timing a preselected period following the onset of operation of the EEPR valve in the refrigeration mode, the time period being selected to permit the valve to substantially stabilize in a position which maintains the exit air temperature at a set point, (c) storing a reference position of the EEPR valve at the end of the preselected period.
0. 47. The method of
0. 48. The method of
0. 49. The method of
0. 50. The method of
0. 51. The method of
0. 54. The air cooling system of
0. 55. The air cooling system of
0. 56. The air cooling system of
0. 57. The air cooling system of
0. 58. The air cooling system of
0. 59. The air cooling system of
|
This is a continuation of application Ser. No. 08/407,676 filed on Mar. 14, 1995, now abandoned.
1. Field of the Invention
This invention relates generally to the commercial refrigeration art, and more particularly to improvements in food product merchandisers and temperature control systems therefor.
2. Description of Prior Art
Great advances have been made in the last forth years in the field of commercial food merchandising with the improved insulation materials, better refrigerants, more efficient air handlers and condensing unit systems, better lighting and the universal use of ambient air temperature and humidity control in food stores and the like. A long checklist of important factors influence the construction and manufacture of food merchandisers including refrigeration requirements and performance, structural engineering for strength, durability and safety as well as insulation effect, servicing capability, product merchandising potential, and both manufacturing and operating costs.
In today's marketplace a wide variety of food merchandisers are used to best market different types of food products as well as meet their cooling needs. In the low temperature field, frozen food merchandisers maintain product display temperatures at about 0°C F. and ice cream cases operate at about -5°C F. to -10°C F. Frozen foods are best protected in reach-in coolers (with glass front doors), but open front, multi-deck merchandisers best display various food products. Similarly, in the medium temperature field of 28°C F. to 50°C F. product temperature range, glass front deli merchandisers are generally preferred for the marketing of freshly cut meats, cheeses, salads and other deli items, but open front multideck merchandisers are widely used for packaged meat and dairy products and single deck cases are preferred for fresh produce. Thus, even with some industry standardization at eight (8') foot and twelve (12') foot lengths for merchandisers, the manufacture of each commercial refrigerator fixture has remained in hand built operation.
In the past, most commercial merchandisers have utilized evaporator coils of the fin and tube type, which extend the full length of the merchandiser to best achieve uniform air cooling from end-to-end throughout the length. In some applications the evaporator coil was divided into two or more full length sections connected in series refrigerant flow relationship and typically arranged in tandem in the bottom section and/or immediately adjacent in the lower back wall of the merchandiser cabinet. Such coils and the control valving therefor were generally accessible only from the inner lower well area of the product zone for maintenance or service. Furthermore, although such a location does not interfere with the structural soundness of a coffin-type merchandiser, it has been discovered that a back wall evaporator coil location limits the structural support capability for internal vertical frames in multi-deck merchandisers, and the cantilever suspension of glass front panels in a deli merchandiser. The commonly assigned co-pending application Ser. No. 08/057,980 of Michael Grassmuck discloses improvements in hinging and structural supports for glass front panels for deli and reach-in merchandisers, and accommodated the development of the air cooling and control system of the present invention.
Also in the past, pressure regulating valves have been interposed in the evaporator-to-compressor suction line to regulate the refrigerant vapor out-flow from the evaporator coil and for the purpose of establishing and maintaining a certain evaporator suction pressure (relative to the compressor) and producing a corresponding saturated refrigeration temperature within the evaporator coil. One class of these valves have generally only been responsive to the evaporator pressure, or the pressure differential between the evaporator and the compressor--and, additionally, many prior art valves have been controlled by a second pilot valve. Representative of such prior art are:
Hanson U.S. Pat. No. 3,303,664
Another class of back pressure regulating valves have been responsive to temperature--as it affects pressure sensors and triggers pressure responsive diaphragm control of a valve element. Representative of such valves are:
Quick U.S. Pat. No. 3,316,731
Another class of evaporator pressure regulating valves have been designed to be responsive to both temperature and pressure acting through a pilot valve. Representative of this class are:
Pritchard U.S. Pat. No. 2,161,312
Dube U.S. Pat. No. 2,401,144
Boyle U.S. Pat. No. 2,993,348
Miller U.S. Pat. No. 3,242,688
The invention is embodied in an air cooling and control system for a refrigerated food merchandiser having an insulated cabinet with a product zone, plural modular evaporator coil sections of substantially equal heat exchange potential and being of predetermined length and arranged in horizontal, spaced, predetermined disposition, first refrigerant metering means for controlling liquid refrigerant flow on the high (inlet) side of the evaporator sections, second refrigerant metering means for controlling suction pressure and refrigerant vapor flow on the low (outlet) side of the evaporator sections, and electronic control means sensing exit air temperatures downstream of the evaporator sections and operating the second metering means in response thereto. The invention is further embodies in the method of operating an electronic evaporator pressure regulating (EEPR) valve during the refrigeration and defrost modes of the controlled evaporator and in response to sensed air temperatures.
It is a principal object of the present invention to provide a novel modular evaporator coil that facilitates modular design and fabrication of different refrigerated fixtures, that provides increased coil capacity with a smaller coil size having a reduced refrigerant charge and improved efficiency; that produces better product temperatures; that eliminates return bends and evaporator coil joints and minimizes refrigerant leaks; that can be used in multiple, parallel-piped sections with one or more liquid metering controls; that is responsive to both liquid and suction controls; and that accommodates ease of manufacture, installation and service. Another feature of the invention is in controlling the operation of commercial refrigerator evaporators to maintain preselected food zone temperatures at substantially constant values. Another object is to provide an EEPR valve for suction control of the associated evaporator means during refrigeration and defrost modes and in response to sensed and projected exit air temperatures. Still another object is to provide an improved apparatus and control strategy for regulating the suction pressure of refrigeration evaporators to achieve operating temperatures and maintain exit air and display zone temperatures. These and still other objects and advantages will become more apparent hereinafter.
In the accompanying drawings which form a part of this specification and wherein like numerals refer to like parts wherever they occur:
For disclosure purposes different embodiments of the modular evaporator coil and electronic evaporator pressure regulator (EEPR) control of the present invention are shown in different commercial food display cases or merchandisers as may be installed in a typical supermarket. Such display cases are generally fabricated in standard eight (8') foot and twelve (12') foot lengths, but may be arranged in a multiple case line-up of several merchandisers operating in the same general temperature range. Low temperature refrigeration to maintain display area temperatures of about 0°C F. for frozen foods requires coil temperatures generally in the range of -5°C F. to -20°C F. to achieve exit air temperatures at about -3°C F. to -11°C F.; and medium temperature refrigeration to maintain fresh food product area temperatures in the range of 34°C F. (red meat) to 46°C F. (produce) requires coil temperatures generally in the range of about 15°C F. to 24°C F. with corresponding exit air temperatures at about 24°C F. to 37°C F. It is clear that a "closed" front case, such as a deli or reach-in having glass panels, will be easier to refrigerate than an open front, multideck merchandiser and that the nature and amount of insulation are also major design factors.
Also for disclosure purposes it will be understood that various commercial refrigeration systems may be employed to operate the air cooling and control systems of the present invention. For instance, conventional closed refrigeration systems of the "back room" type having multiplexed compressors may be used, or merchandisers of the present invention may be operated by strategically placed condensing units located in the shopping arena--of the type disclosed and claimed in commonly assigned, co-pending patent application Ser. No. 08/057,617. In either event, the general operation of refrigeration systems will be understood and readily apparent to those skilled in the art, and various refrigerant terms such as "high side" and "low side" and "exit air" will be used in their conventional refrigeration sense.
Referring to
A feature of the invention resides in the refrigeration means 21 for the merchandiser DM, and specifically in the use of plural modular evaporator coil sections 22 in lieu of conventional full length coils, as will be described more fully. Another feature of the invention is in the refrigeration control for the merchandiser DM, which includes a high side liquid control or metering means in the form of a thermostatic expansion valve 23 and also includes a low side suction control or metering means in the form of an EEPR valve 24 and electronic controller 25 therefore, as will also be described in greater detail hereinafter.
Referring to
Each type of commercial refrigerated merchandiser in the past largely has been individually designed for its own food display or storage purpose, and fabrication generally has been a custom assembly process. These prior art merchandisers have had solid, bulky internal frames with heavy insulation therebetween and fully supporting inner cabinets with full length evaporator coils to achieve even, balanced air flow from end-to-end of the display area. It has been discovered that modular internal-external support frame structures can effectively support most commercial merchandiser cabinets--whether single deck as in deli and produce types, or 2-5 multideck cases for frozen foods, meat or dairy which have the greater shelf weight incident thereto. The modularity of the evaporator coil concept of the present invention accommodates the use of novel cabinet frame members that carry the weight of insulated panels, shelving and duct forming members and translate it to an external frame assembly.
Thus, the modular evaporator coils 22 of the invention--while of conventional fin and tube configuration--constitute an advance in the commercial merchandiser field in several respects. The modular coils 22 are standardized in four (4') foot lengths to accommodate more flexibility in placement and facilitate the use of modular framing, as disclosed more fully in a commonly assigned co-pending patent application Ser. No. 08/404,036 of Martin J. Duffy entitled Refrigerated Merchandiser With Modular External Frame Structure. The shorter modular coil 22 has continuous serpentine coil tubes without end joints or the like thereby virtually eliminating coil leaks. The tubing is of smaller diameter than feasible for eight or twelve foot coils and reduces the total amount of refrigerant charge needed. The fins of the coil are more closely spaced than is conventional but with the use of smaller tubing still produce a larger volumetric air space through the coil for more efficient heat exchange and cooling of air recirculated by the fans 12b without added air side resistance. For instance, prior art coils used either ¾" O.D. tubing with tube spacing at 2" from center-to-center, or ⅝" O.D. tubing with tube spacing at 1⅜". It has been discovered that {fraction (7/16)}" O.D. tubing can be spaced at 1.2" and still produce 50% more heat transfer fin surface than conventional coils. The result is better coil performance, use of less material and smaller refrigerant change, fewer joints and less leakage, and better defrost capability.
Thus, still referring to
Referring now to
It will be understood that air temperature control for the product zone of a closed single deck deli merchandiser DM is more easily accomplished than for the product zone of an open front, multideck merchandiser, such as the four deck meat merchandiser MM of
Referring to
In the embodiment of
Metering of refrigerant through the evaporators 22, 122 for refrigeration of the merchandiser product zone 18, 118 is carried out by one of more expansion valves 23, 123 and one or more EEPR valves 24, 124. Various configurations of expansion valves and EEPR valves are possible according to the nature of the merchandiser and its refrigeration requirements. The configuration shown in
The amount of refrigeration carried out by the evaporators 22, 122 is controlled by operation of the EEPR valves 24. The function of the expansion valves 23, 123 is to optimize the refrigeration operation by maintaining an optimal refrigerant superheat value (e.g., 5°C F.) on the suction side of the evaporators, not to achieve temperature control. Thus, each expansion valve 23, 123 is modulated solely in response to the temperature of the refrigerant detected by sensing bulb 28, 128 located on the outlet end of its corresponding evaporator. The expansion valve can be made relatively inexpensively and preset for operating in a predetermined manner in response to the temperature detected by its sensing bulb. It is not believed to be necessary in most instances to readjust the expansion valve after installation.
The expansion valves 23, 123 and their corresponding sensing bulbs 28, 128 can be arranged in several different configurations, the following descriptions of which are not intended to be exhaustive. For instance, the single expansion valve 23 used for all three evaporators, as shown in
The present invention is to be contrasted with evaporator temperature control in a merchandiser (not shown) by expansion valves which are modulated in response to detected exit air temperature from the evaporators. Exit air temperature control for a particular evaporator by operation of an expansion valve at a substantially constant suction pressure will result in variations in the superheat of the refrigerant leaving the evaporator. For example, when the exit air temperature is too cold, the expansion valve throttles down and reduces the refrigerant flow entering the evaporator. As a result, all of the refrigerant in the evaporator is completely vaporized well prior to reaching the outlet of the evaporator. Failure to keep the evaporator substantially full of boiling refrigerant causes a loss in efficiency, non-uniform frost build up on the evaporator requiring more frequent defrost cycles, and additional dehumidification. Accordingly, the present invention closely controls saturated evaporator temperature by locating the EEPR valve 24 near the evaporator, preferably in the merchandiser itself, and the expansion valve functions to make sure that the evaporator operates efficiently by maintaining a substantially constant superheat.
Operation of the EEPR valve 24, 124 is controlled by the controller 25, 125 mounted in the merchandiser and connected to a valve circuit of the EEPR valve for selectively activating its stepper motor 38 to open, close or modulate the valve opening, at 41. The temperature sensor 43, 143 located next to the evaporators detects the exit air temperature from the corresponding evaporator. These sensors are capable of generating signals corresponding to the temperature detected and transmitting them to the controller 25, 125. The controller uses an average of the sensed temperature values in the control of the EEPR valve 24, 124, as described more fully below. It is to be understood that a greater or lesser number of temperature sensors could be used, that sensors for detecting parameters other than temperatures could be used and that the signals from the sensors could be processed differently for use in controlling the EEPR valve without departing from the scope of the present invention.
In order to achieve the necessary accuracy in the position of the EEPR valve element 42, the controller is configured to compensate for the inherent looseness or lost motion in the gearing arrangement (not shown) connecting the stepper motor 37 to the valve element 42. The correspondence between the position of the stepper motor and the position of the valve element might normally be lost in making fine adjustment. Such loss could occur when the direction of motion of the motor 37 changes, such as when the motor first moves the valve element 42 to a more open position in chamber 39 and then attempts to reversely move the valve element by a small amount to a more closed position. When the direction of motion changes, the looseness in the gears may result in no motion of the valve element, even though the stepper motor moves to a position which should correspond to a new valve position. To overcome this inherent inaccuracy, the controller 25, 125 operates so that the movement of the valve element 42 to the final position called for by the controller always occurs from the same direction as the previous movement. More specifically, the valve element is always moved to its final position in a valve opening direction, which permits the use of refrigerant pressure to keep the gears tight. For example, the valve element may be at a position corresponding to 1000 steps of the stepper motor 37 when the control algorithm calls for the valve to be at a position of 950 steps (corresponding to a more closed position of the valve). The controller activates the valve circuit to run the motor to a position of 940 steps--i.e., past the position called for by the control algorithm--and then to the final set position of 950 steps. The position will be highly accurate because the refrigerant pressure in the suction line tends to push the valve element open so that any slack in the gears is removed by action of the pressure.
Referring now to the flow chart of
Upon leaving the start sequence 80, the controller enters into a refrigeration mode including a control routine 82 toward maintaining the exit air temperature T from the evaporators (122) at Tset by modulation of the EEPR valve 124. The refrigeration mode 82 includes modulation of the valve opening (by changing the position of the valve element) in response to the temperature T detected by the sensors, as well as periodic checks 83 to determine the start of a defrost mode, and data storage of valve reference positions (85) such as represented by the valve position which maintained average exit air temperature T generally equal to Tset during the normal refrigeration mode. The valve reference position is used as an initial setting for the EEPR valve at the beginning of the next normal refrigeration mode following a defrost mode.
The controller is preprogrammed with a default valve reference position for use in setting the EEPR valve during the first refrigeration mode following start up of the system. A new valve reference position will be stored by the controller at a scheduled later time sufficiently far removed from initial operation in the refrigeration mode so that the EEPR valve has time to settle into a reasonably stable operating mode (i.e. position) for maintaining exit air temperature at Tset. Thus upon initiation of the refrigeration mode, the controller (at 81) first sets a valve reference position storage time t1 equal to a store time period tstore. In a preferred embodiment, tstore equals 60 minutes. A timer in the controller begins counting down the time t1 from tstore until t1 reaches zero (see 84). The controller then stores the valve reference or average position (see 85) of the EEPR valve element as a reference for the next refrigeration mode.
Throughout the refrigeration mode, the controller is receiving temperature signals from the temperature sensors 143 associated with the evaporators 122. The controller averages the detected temperatures T and uses a control algorithm (e.g., a PID control algorithm) to process the average temperature and produce a control signal for the stepper motor to modulate the valve opening. In this way, the EEPR valve is operated to change the suction pressure seen by the evaporator so as to change the temperature of the evaporator. Although not illustrated, the controller includes various alarms to detect failures in the air cooling system.
Initiation of a defrost cycle could be controlled by a timer within the controller, by a master defrost timer located externally of the merchandiser and controlling the refrigeration and defrost cycles for a number of merchandisers in the system 126, or by detection of some parameter other than time. The defrost method may be by off-time (closing off the high side liquid feed) or by electric defrost, and the air circulating means 21 continue to operate to accelerate the heat distribution through the evaporators. It should also be recognized that a typical defrost is typically carried out on a time line that has two components; namely, a de-icing period to fully melt the ice accumulation from the fins 34 and tubing 33 of the coil (which achieves a drip temperature) and a drip period to permit the water to run off the evaporator to prevent a re-freeze condition. It is contemplated that hot or latent gas defrost may also be used as an alternative, in which case the fans 12a would be turned off during the de-icing period of defrost. In any event, when the controller is informed that it is time for defrost (83a), it enters the defrost mode.
Defrost of the evaporators begins by the controller activating the valve circuit to fully close (86) the EEPR valve, stopping the normal refrigeration mode in the merchandiser. The temperature of the exit air from the evaporators begins to rise, and the controller periodically averages the temperatures from the sensors 143 and, at 87, determines if the averaged temperature equals or exceeds a drip time temperature Tdrip stored in the controller. In the preferred embodiment, the drip time temperature Tdrip is empirically selected to be an exit air temperature above 32°C F. as detected at the end of the de-ice period when all of the ice on the evaporators is gone. The beginning of drip time may be initiated by detection of the absence of ice on the evaporators. One way of accomplishing this is by first detecting a plateau in exit air temperature rise during the defrost mode which indicates that the thermal energy in air passing over the evaporators is being employed in melting the ice. The controller then looks for a exit air temperature rise following the plateau, which indicates the ice is gone and the thermal energy in the merchandiser again goes to heating the air. This rise in exit air temperature signals that de-icing is complete and that drip time has begun (see FIG. 9). In the preferred embodiment following detection of Tdrip, a drip time t2 is reset (88) to a time period tdrip and the controller partially opens the EEPR valve to meter refrigerant flow through the evaporators, see 89. The controller then modulates the EEPR valve in response to the averaged sensed temperature to refrigerate the merchandiser at Tdrip. At the same time refrigeration is begun at Tdrip, a timer 90 in the controller is started to count down drip time t2 from tdrip to zero. Thus, as shown in
The controller halts refrigeration at Tdrip when it finds that the drip time t2 equals zero, indicating the period for drip time tdrip has expired. The controller then enters a pull-down mode by fully opening the EEPR valve (91) and holds it open without regard to the detected exit air temperatures T from the temperature sensors 143 until such time as the average detected temperature first equals or goes below Tset (92). Overriding the normal modulation of the EEPR valve during the pull-down period following defrost and holding the valve in its fully open position accelerates the pull-down to the refrigeration set point. After the sensed temperature first crosses Tset, the valve is immediately set to the valve reference position 93 stored from the last operation of the controller in the refrigeration mode. The valve reference position storage time t1 is reset to tstore (81) and the refrigeration mode, described above, begins again.
The effect on exit air temperature caused by operation of the controller and EEPR valve as described is graphically illustrated in
The rapid pull down achieved by holding the EEPR valve in a fully open position results in exit air temperature declining in a steep slope to the set point Tset. In contrast, if normal prior art modulation of an EPR-type valve is permitted following the end of the defrost period, the exit air temperature approaches the set point Tset asymptotically. The reason for this is that the control algorithm causes refrigeration to slow as the set point is approached. Therefore, the set point Tset is not reached as quickly in the prior art as with the present invention.
Referring now to
Referring to
The scope of the invention is intended to encompass such changes and modifications as will be apparent to those skilled in the art, and is only to be limited by the scope of the appended claims.
Patent | Priority | Assignee | Title |
11143449, | Aug 20 2009 | MAERSK CONTAINER INDUSTRY A/S | Method for dehumidifying a refrigeration system |
6889518, | Aug 22 2001 | Hill Phoenix, Inc | Service case |
6912864, | Oct 10 2003 | Hussmann Corporation | Evaporator for refrigerated merchandisers |
7032401, | Nov 05 2003 | LEER, INC | Break down ice merchandiser shroud |
7143605, | Dec 22 2003 | Hussman Corporation | Flat-tube evaporator with micro-distributor |
7296422, | Mar 30 2004 | Maytag Corporation | Produce preservation system |
7344210, | Nov 05 2003 | LEER, INC | Break down ice merchandiser shroud |
7367198, | Jul 07 2005 | Hussmann Corporation | Method of control for a refrigerated merchandiser |
7451607, | Jul 07 2005 | Hussmann Corporation | Method of control for a refrigerated merchandiser |
7770806, | Jun 19 2007 | Nortek Global HVAC LLC | Temperature control in variable-capacity HVAC system |
7992398, | Jul 16 2008 | Honeywell International Inc; Honeywell International, Inc | Refrigeration control system |
8291719, | Oct 09 2007 | BE AEROSPACE, INC | Thermal control system and method |
8689575, | Oct 09 2007 | B/E Aerospace, Inc. | Thermal control system and method |
9261299, | Sep 22 2006 | SIEMENS INDUSTRY, INC | Distributed microsystems-based control method and apparatus for commercial refrigeration |
9303901, | Jun 12 2007 | DANFOSS A S | Method for controlling a vapour compression system |
9814326, | Aug 26 2014 | Hill Phoenix, Inc | Refrigeration system having a common air plenum |
Patent | Priority | Assignee | Title |
1953118, | |||
2075838, | |||
2133963, | |||
2166813, | |||
2219912, | |||
2254420, | |||
2490413, | |||
2495554, | |||
2665072, | |||
2794325, | |||
2943643, | |||
3003331, | |||
3063253, | |||
3147602, | |||
3168805, | |||
3196626, | |||
3264842, | |||
3316731, | |||
3363433, | |||
3434299, | |||
3500634, | |||
3501925, | |||
3531945, | |||
3564865, | |||
3698204, | |||
3914952, | |||
3987642, | Jun 24 1975 | Fiat Societa per Azioni | Control valve for vehicle air conditioning systems |
4364238, | Nov 03 1977 | Danfoss A/S | Valve for refrigeration plant |
4478050, | Nov 19 1982 | Hussmann Corporation | Oil separation for refrigeration system |
4523435, | Dec 19 1983 | Carrier Corporation | Method and apparatus for controlling a refrigerant expansion valve in a refrigeration system |
4651535, | Aug 08 1984 | Pulse controlled solenoid valve | |
4685309, | Nov 01 1982 | Emerson Electric Co. | Pulse controlled expansion valve for multiple evaporators and method of controlling same |
4686835, | Aug 08 1984 | Pulse controlled solenoid valve with low ambient start-up means | |
4735060, | Aug 08 1984 | Pulse controlled solenoid valve with food detection | |
4750334, | Mar 26 1987 | Parker Intangibles LLC | Balanced thermostatic expansion valve for refrigeration systems |
4789025, | Nov 25 1987 | Carrier Corporation | Control apparatus for refrigerated cargo container |
4845956, | Apr 25 1987 | Danfoss A/S | Regulating device for the superheat temperature of the evaporator of a refrigeration or heat pump installation |
4899554, | Jan 08 1987 | SANDEN CORPORATION, A CORP OF JAPAN; CANON KABUSHIKI KAISHA, A CORP OF JAPAN | Refrigerator with plural storage chambers |
4911404, | Jul 28 1989 | Parker Intangibles LLC | Electronically operated expansion valve |
4934156, | Jul 16 1988 | Danfoss A/S | Evaporator pressure regulating valve controlled by an auxiliary force for a refrigerator installation |
4958502, | Jan 05 1988 | Mitsubishi Jukogyo K.K. | Controller for a refrigeration unit |
4993231, | Mar 02 1990 | ZHEJIANG XINJING AIR CONDITIONING EQUIPMENT CO , LTD | Thermostatic expansion valve with electronic controller |
5035119, | Aug 08 1984 | Apparatus for monitoring solenoid expansion valve flow rates | |
5060910, | Mar 15 1990 | Aisan Kogyo Kabushiki Kaisha | Flow control device |
5065595, | Dec 05 1990 | Parker Intangibles LLC | Thermostatic expansion valve |
5168200, | Dec 18 1989 | Automatic powered flowmeter valves and control thereof | |
5182920, | Jul 15 1991 | Mitsubishi Denki Kabushiki Kaisha | Refrigeration cycle system |
5184473, | Feb 10 1992 | General Electric Company | Pressure controlled switching valve for refrigeration system |
5247806, | Aug 20 1990 | Matsushita Electric Industrial Co., Ltd. | Multi-system air conditioner |
5251459, | May 28 1991 | Emerson Electric Co. | Thermal expansion valve with internal by-pass and check valve |
5329462, | Dec 24 1992 | Carrier Corporation | Expansion valve control |
5357767, | May 07 1993 | Hussmann Corporation | Low temperature display merchandiser |
5361597, | Apr 22 1993 | Fuji Koki Manufacturing Co., Ltd. | Thermostatic expansion valve |
5364066, | Jul 15 1993 | Parker Intangibles LLC | Dual port valve with stepper motor actuator |
5381816, | Aug 31 1992 | Orbital Walbro Corporation | Pressure regulator |
5396780, | Dec 18 1992 | Danfoss A/S | Refrigeration system and method of controlling a refrigeration system |
5408841, | Dec 06 1990 | Nippondenso Co., Ltd. | Automotive air conditioner |
5533347, | Dec 22 1993 | NOVAR MARKETING INC | Method of refrigeration case control |
5572879, | May 25 1995 | Thermo King Corporation | Methods of operating a refrigeration unit in predetermined high and low ambient temperatures |
5771908, | Sep 25 1996 | O DORSAY, INC | Hairclip |
5921098, | Nov 17 1997 | DANFOSS A S | Process for the control of a refrigeration system as well as a refrigeration system and expansion valve |
Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Apr 27 2000 | Hussmann Corporation | (assignment on the face of the patent) | / | |||
Sep 30 2011 | Hussmann Corporation | GENERAL ELECTRIC CAPITAL CORPORATION, AS ADMINISTRATIVE AGENT | NOTICE AND CONFIRMATION OF GRANT OF SECURITY INTEREST IN PATENTS | 027091 | /0111 | |
Apr 01 2016 | GENERAL ELECTRIC COMPANY AS SUCCESSOR IN INTEREST BY MERGER TO GENERAL ELECTRIC CAPITAL CORPORATION , AS ADMINISTRATIVE AGENT | Hussmann Corporation | RELEASE OF SECURITY INTEREST IN PATENTS RECORDED AT REEL 027091, FRAME 0111 AND REEL 029568, FRAME 0286 | 038329 | /0685 |
Date | Maintenance Fee Events |
Oct 28 2005 | M1552: Payment of Maintenance Fee, 8th Year, Large Entity. |
Nov 07 2005 | ASPN: Payor Number Assigned. |
Oct 28 2009 | M1553: Payment of Maintenance Fee, 12th Year, Large Entity. |
Date | Maintenance Schedule |
Apr 09 2005 | 4 years fee payment window open |
Oct 09 2005 | 6 months grace period start (w surcharge) |
Apr 09 2006 | patent expiry (for year 4) |
Apr 09 2008 | 2 years to revive unintentionally abandoned end. (for year 4) |
Apr 09 2009 | 8 years fee payment window open |
Oct 09 2009 | 6 months grace period start (w surcharge) |
Apr 09 2010 | patent expiry (for year 8) |
Apr 09 2012 | 2 years to revive unintentionally abandoned end. (for year 8) |
Apr 09 2013 | 12 years fee payment window open |
Oct 09 2013 | 6 months grace period start (w surcharge) |
Apr 09 2014 | patent expiry (for year 12) |
Apr 09 2016 | 2 years to revive unintentionally abandoned end. (for year 12) |