Vapor compression systems including liquid refrigerant atomizer, and methods of operating and controlling the same

Abstract

A vapor compression system includes a compressor including a compression stage for compressing a working fluid, a first heat exchanger downstream from the compressor that receives and cools the working fluid, a second heat exchanger downstream from the first heat exchanger and upstream from the compressor that receives and heats the working fluid, and an accumulator positioned between the second heat exchanger and the compression stage. The accumulator defines an interior volume for containing a vapor phase and a liquid phase of the working fluid, and the accumulator includes an inlet to receive the working fluid from the second heat exchanger and an outlet to allow the vapor phase of the working fluid to exit the accumulator and flow towards the compression stage. The accumulator atomizes the liquid phase of the working fluid into droplets and introduces the droplets into the vapor phase of the working fluid exiting the accumulator.

What is claimed is: 
     
         1 . A vapor compression system that circulates a working fluid, the system comprising:
 a compressor including a compression stage for compressing the working fluid;   a first heat exchanger downstream from the compressor that receives and cools the working fluid;   a second heat exchanger downstream from the first heat exchanger and upstream from the compressor that receives and heats the working fluid; and   an accumulator positioned between the second heat exchanger and the compression stage, wherein the accumulator defines an interior volume for containing a vapor phase and a liquid phase of the working fluid, wherein the accumulator includes an inlet to receive the working fluid from the second heat exchanger and an outlet to allow the vapor phase of the working fluid to exit the accumulator and flow towards the compression stage, and wherein the accumulator is operable to atomize the liquid phase of the working fluid into droplets and introduce the droplets into the vapor phase of the working fluid exiting the accumulator.   
     
     
         2 . The vapor compression system of  claim 1 , wherein the accumulator includes an ultrasonic transducer positioned in the interior volume to contact the liquid phase of the working fluid and operable to atomize the liquid phase of the working fluid. 
     
     
         3 . The vapor compression system of  claim 2 , wherein the accumulator includes two or more ultrasonic transducers. 
     
     
         4 . The vapor compression system of  claim 1 , wherein the inlet is positioned proximate a bottom of the accumulator and the outlet is positioned proximate a top of the accumulator, such that the vapor phase of the working fluid flows generally upwards within the interior volume towards the outlet and carries relatively smaller droplets of the liquid phase, and relatively larger droplets of the liquid phase separate from the vapor phase and pool within the interior volume. 
     
     
         5 . The vapor compression system of  claim 1 , wherein the droplets of the liquid phase of the working fluid introduced into the vapor phase transfer heat via a heat of evaporation of the droplets during compression. 
     
     
         6 . The vapor compression system of  claim 5 , further comprising a controller connected to the accumulator for controlling an amount of the droplets introduced into the vapor phase of the working fluid. 
     
     
         7 . The vapor compression system of  claim 6 , further comprising temperature sensors and pressure sensors connected to the controller and positioned for monitoring a temperature and pressure of the working fluid, wherein the controller is configured to:
 determine one or more characteristics of the working fluid at two or more stages of the vapor compression system based on the monitored temperature and pressure, and   control, based on the determined one or more characteristics, the amount of the droplets introduced into the vapor phase of the working fluid.   
     
     
         8 . The vapor compression system of  claim 7 , wherein the compressor is a scroll compressor, and wherein the one or more characteristics include a density of the working fluid. 
     
     
         9 . The vapor compression system of  claim 7 , wherein the working fluid is a refrigerant blend comprising a first refrigerant and a second refrigerant, wherein a difference between boiling points of the first and second refrigerants is greater than or equal to 25° C., and wherein the one or more characteristics are indicative of a concentration of the first and second refrigerants in the working fluid. 
     
     
         10 . The vapor compression system of  claim 9 , wherein the first refrigerant and the second refrigerant are independently selected from the group consisting of: carbon dioxide (R-744), chlorodifluoromethane (R-22), 1,1,1,2-tetrafluoroethane (R134A), R410A (a near-azeotropic mixture of difluoromethane (R-32) and pentafluoroethane (R-125), 1,1-difluoroethane (R152a), dimethyl ether (R-E170), propane (R-290), 2,3,3,3-tetrafluoroprop-1-ene (R-1234yf), cis- and trans-1,3,3,3-tetrafluoropropene (HFO-1234ye), cis- and trans-1,3,3,3-tetrafluoroprop-1-ene (R-1234ze), 3,3,3-trifluoropropene (HFO-1234zf), trifluoromonochloropropenes (HFO-1233), trans-1-chloro-3,3,3-trifluoropropene (HFO-1233zd (E)), cis-1-chloro-3,3,3-trifluoropropene (HFO-1233zd (Z)), 2-chloro-3,3,3-trifluoropropene (HFO-1233xf), trans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz (Z)), cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz (E)), pentafluoropropenes (HFO-1225), 1,1,3,3,3-pentafluoropropene (HFO-1225zc), 1,2,3,3,3-pentafluoropropene (HFO-1225yez), hexafluorobutenes (HFO-1336), cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz (Z)), trans-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz (E)), trans-1,2-difluoroethene (R-1132 (E)), and any isomers or combinations thereof. 
     
     
         11 . A method of operating a vapor compression system that includes a compressor, a first heat exchanger, a second heat exchanger, and an accumulator, the method comprising:
 compressing a working fluid at a compression stage of the compressor;   cooling the working fluid at the first heat exchanger downstream from the compressor;   heating the working fluid at the second heat exchanger downstream from the first heat exchanger;   channeling the working fluid into an interior volume of the accumulator downstream from the second heat exchanger and upstream from the compression stage, wherein the working fluid in the interior volume includes a liquid phase and a vapor phase;   channeling the vapor phase of the working fluid from the accumulator towards the compression stage; and   using the accumulator, atomizing the liquid phase of the working fluid into droplets and introducing the droplets into the vapor phase being channeled towards the compression stage.   
     
     
         12 . The method of  claim 11 , wherein atomizing the liquid phase of the working fluid into droplets comprises contacting the liquid phase with an ultrasonic transducer in the interior volume. 
     
     
         13 . The method of  claim 11 , further comprising flowing the vapor phase of the working fluid generally upwards within the interior volume from an inlet towards an outlet of the accumulator such that the vapor phase carries relatively smaller droplets of the liquid phase and relatively larger droplets of the liquid phase separate from the vapor phase and pool within the interior volume. 
     
     
         14 . The method of  claim 11 , further comprising transferring heat during compression via a heat of evaporation of the droplets of the liquid phase introduced into the vapor phase. 
     
     
         15 . The method of  claim 14 , further comprising:
 monitoring a temperature and a pressure of the working fluid at two or more stages of the vapor compression system;   determining one or more characteristics of the working fluid based on the monitored temperatures and pressures; and   controlling, based on the determined one or more characteristics, an amount of the droplets introduced into the vapor phase of the working fluid.   
     
     
         16 . The method of  claim 15 , wherein the compressor is a scroll compressor, and wherein the one or more characteristics include a density of the working fluid. 
     
     
         17 . The method of  claim 15 , wherein the working fluid is a refrigerant blend comprising a first refrigerant and a second refrigerant, wherein a difference between boiling points of the first and second refrigerants is greater than or equal to 25° C., and wherein the one or more characteristics are indicative of a concentration of the first and second refrigerants in the working fluid. 
     
     
         18 . A vapor compression system that circulates a working fluid including a vapor phase and a liquid phase, the system comprising:
 a scroll compressor including a compression stage for compressing the working fluid;   a first heat exchanger downstream from the compressor that receives and cools the working fluid;   a second heat exchanger downstream from the first heat exchanger and upstream from the compressor that receives and heats the working fluid;   an atomizer configured to generate droplets of the liquid phase of the working fluid and positioned to introduce the droplets into the vapor phase of the working fluid upstream from the compression stage; and   a controller connected to the atomizer and configured to control an amount of the droplets introduced into the vapor phase of the working fluid based on a volume ratio of the scroll compressor.   
     
     
         19 . The vapor compression system of  claim 18 , further comprising one or more sensors connected to the controller and positioned for monitoring one or more conditions of the working fluid at a first stage upstream from the compression stage and a second stage downstream from the compression stage, and wherein the controller is configured to:
 determine a density of the working fluid at each of the first and second stages based on the monitored conditions of the working fluid;   compare a ratio of the densities to a target volume ratio of the scroll compressor; and   based on the comparison, control the amount of the droplets introduced into the vapor phase of the working fluid.   
     
     
         20 . The vapor compression system of  claim 19 , wherein the one or more sensors include a temperature sensor and a pressure sensor positioned at each of the first stage and the second stage. 
     
     
         21 . The vapor compression system of  claim 18 , wherein the atomizer is positioned within a housing of the scroll compressor.