Patent Application
20090288433
This invention relates to heating, ventilation, air-conditioning and refrigeration (HVACR) systems, and, more particularly, to a method and apparatus capable of detecting malfunctions in the system before they become catastrophic and cannot be remedied by routine maintenance.
HVACR systems that operate using a vapor-compression cycle generally comprise a compressor, a condenser, an expansion valve and an evaporator interconnected by a line having an interior within which a refrigerant fluid is circulated. Although this technology is mature and is currently used in a wide variety of commercial and residential applications, malfunctions can arise as a result of leaks in the system or failure of one or more components. In many instances, the malfunction may not be catastrophic, e.g. wherein the system ceases to heat or cool altogether, but may result in a gradual or progressive decrease in performance and/or efficiency that can nevertheless create spoilage of foodstuffs and other inventory, for example, or other problems.
Periodic maintenance of HVACR systems can be time consuming, expensive and in many cases unnecessary at the time performed. Recognizing that a failure to maintain such systems will eventually cause a problem, the issue becomes how often such maintenance should be performed and what should be done. Approaches that rely solely on the passage of time are often ineffective and ignore the specific requirements of a particular installation and/or type of system.
Automated preventative maintenance devices for HVACR systems have been proposed, such as disclosed, for example, in U.S. Pat. No. 5,596,507. The device disclosed in the '507 patent relies upon a number of temperature sensors and electrical current sensors to detect a variety of operating parameters of the system, and to provide inputs to a computer capable of analyzing the data and identifying potential trouble spots in the system that may need maintenance. While systems of this type may be effective, they are not economically feasible for residential applications and many smaller commercial operations.
This invention is directed to a predictive maintenance method and apparatus for HVACR systems including a sensor capable of detecting the presence of a gaseous phase in the refrigerant fluid at a location wherein solely liquid phase should be present if the system is functioning properly.
In the presently preferred embodiment, the method and apparatus of this invention is particularly intended for use in a vapor-compression system including a compressor, a condenser, an expansion valve and an evaporator interconnected by a line having an interior within which a refrigerant fluid is circulated. The apparatus comprises a sensor positioned in the line at a location between the condenser and expansion valve wherein the refrigerant fluid, if the system is functioning properly, is in liquid phase. The sensor is effective to detect the presence of gas bubbles in the refrigerant fluid, and provide a warning indication that maintenance of the system is required.
Unlike prior predictive maintenance systems, the method and apparatus of this invention is relatively simple, inexpensive and may be easily installed in residential and commercial HVACR systems. While no specific indication of the cause of a problem in the system is provided, it is contemplated that competent service personnel can readily identify and repair the HVACR system when notified of a maintenance issue, thus substantially eliminating the need for periodic inspections of such system.
The structure, operation and advantages of the presently preferred embodiment of this invention will become further apparent upon consideration of the following description, taken in conjunction with the accompanying drawings, wherein:
Referring now to the drawings, an HVACR system 10 is schematically depicted that operates by vapor compression in a conventional manner. The details of system 10 form no part of this invention and are therefore discussed generally herein. The system 10 includes a compressor 12, a condenser 14, an expansion valve 16 and an evaporator 18 interconnected by a line 20 having an interior 22 within which a refrigerant fluid 24 is circulated in the direction of the arrows shown in
The fluid 24 undergoes phase changes and temperature changes in the course of passage through the system 10 that may be used for heating or cooling purposes depending upon the particular application for which the system 10 is employed. Assuming for purposes of discussion that the system 10 is utilized in a refrigeration or air conditioning application, fluid 24 in saturated vapor form is initially directed to the intake of the compressor 12. The compressor 12 is effective to compress the saturated vapor which increases its pressure and temperature, forming a superheated vapor. The superheated vapor is discharged from the compressor 12 and enters the condenser 14. The condenser 14 is formed with a number of coils (not shown) through which the superheated vapor is directed. The coils are cooled by circulating air or water in order to remove heat from the superheated vapor and convert it into a saturated liquid that is transmitted to the expansion valve 16. If the system 10 is functioning properly, the fluid 24 is in a saturated liquid phase throughout the passage within line 20 from the condenser 14 to the expansion valve 16.
The purpose of the expansion valve 16 is to create an abrupt lowering of the pressure of the saturated liquid received from the condenser 14. This causes adiabatic flash evaporation which lowers the temperature of the refrigerant fluid 24 and produces a mixture of cold refrigerant liquid and vapor. The liquid/vapor mixture discharged from the expansion valve 16 is transmitted to the evaporator 18. In most designs, the evaporator 18 is formed with a number of coils or tubes (not shown) and a fan 26 directs relatively warm air, e.g. from the space that is being cooled, over the coils or tubes. See arrows 27 in
As noted above, if the system 10 is operating properly, the refrigerant fluid 24 is in a saturated liquid phase in the course of passage within line 20 between the output of the condenser 14 and the input of the expansion valve 16. The presence of a gaseous phase of the fluid 24 at this location is an indication of a maintenance issue, e.g. that there is a leak in the system 10 or one or more of the components 12-18 is not functioning normally. In accordance with a presently preferred embodiment of this invention, a predictive maintenance sensor 26 is located in the line 20 between the expansion valve 16 and condenser 14, and preferably immediately upstream from the expansion valve 16. The sensor 26 is effective to detect the presence of a gaseous phase within the fluid 24, and to cause a warning to be produced indicating that maintenance is needed.
The sensor 26 comprises an emitter 28, a detector 30 and an optical aperture 32 formed in the line 20. A controller 34, discussed in more detail below, is coupled to the emitter 28 and the detector 30. In the embodiment depicted in
The detector 30 in the
An alternative embodiment of this invention is illustrated in
For purposes of illustration, the fluid 24 circulating through the line 20 is shown in liquid phase in
In the presently preferred embodiment, the optical aperture 32 or the two aligning sections 38, 40 that form an optical aperture are sized to be smaller than at least some of the gas bubbles 42 that are present in the refrigerant fluid 24 when it is a mixture of liquid and gaseous phase. In particular, the optical aperture 32, or sections 38, 40, have a height dimension measured in a direction generally perpendicular to the flow of fluid 24 through the line 20 that is smaller than the diameter of at least some of the gas bubbles 42 present in the fluid 24. For example, an optical aperture 32, or sections 38, 40, having a height dimension of 0.02 inches would readily permit the detection of gas bubbles 42 of that diameter or larger. It is also contemplated that the sections 38 and 40 forming an optical aperture could be oriented 90° from their position shown in
The controller 34 may be any suitable processor capable of operating the emitter 28, receiving the signals produced by the detector 30 and producing a warning indication in the event a second signal is produced. In one presently preferred embodiment, following initial start-up of the system 10, the controller 34 may record a “baseline” value representative of the first signal produced by the detector 30 wherein it is known that the system 10 is operating properly and fluid 24 in the form of a saturated liquid is circulating through the line 20 between the output of the condenser 14 and the input of the expansion valve 16. The controller 34 may operate the emitter 28 and detector 30 periodically or continuously, as desired, to check on the status of the system 10. Subsequent signals produced by the detector 30 are compared to the baseline value, and, if such signals noted above are within a predetermined range of the baseline value, e.g. “first” signals, no warning indication is produced. On the other hand, if a “second” signal is produced representative of the presence of both liquid and gaseous phase within the line 20, a comparison by the controller 34 of such second signal to the baseline value results in the production of a warning indication that maintenance of the system 10 is required. It is contemplated that the warning indication may comprise a flashing light or the like on a refrigeration unit, on the thermostat of an air conditioning system or other suitable indicia.
While the invention has been described with reference to a preferred embodiment, it should be understood by those skilled in the art that various changes may be made and equivalents 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.
