Oil circulation observer for HVAC systems

Abstract

An innovative oil observer for estimating oil concentration and oil amount in a refrigerant compressor in a vapor compression cycle is described. The invention ensures the safe operation of the compressor by ensuring that adequate lubricant is present in the compressor. This oil observer is based on oil models for components of air conditioning and refrigeration systems. Oil models for HVAC components estimate oil mass and refrigerant mass in each component. With all component oil models and heat exchanger observers which provide the estimation of inner geometric lengths of two-phase flow heat exchangers, a system-level oil observer is established by integrating all component models. Experimental testing has been conducted to verify the performance of this oil observer for steady state operation and dynamic processes. The invention has direct applications in residential and commercial air conditioning and refrigeration systems.

1 . A method of monitoring a parameter related to lubricant in a first component of a vapor compression cycle system, comprising: 
 estimating a parameter related to retained lubricant in a plurality of other components of the vapor compression cycle system; and    subtracting the estimate of the parameter related to retained lubricant from a parameter related to a known total lubricant in the vapor compression system.    
   
   
       2 . The method of  claim 1 , wherein the first component of the vapor compression cycle system is a compressor.  
   
   
       3 . The method of  claim 1 , wherein the plurality of other components of the vapor compression cycle system comprise at least one of an evaporator, an accumulator, a suction gas line, a discharge gas line, a condenser, a liquid line and a receiver.  
   
   
       4 . The method of  claim 1 , wherein the parameter related to retained lubricant in the plurality of other components of the vapor compression cycle system is determined using one or more parameters related to the state of each component of the vapor compression system.  
   
   
       5 . A refrigeration apparatus comprising a device for monitoring a parameter related to lubricant in a first component of the refrigeration apparatus, the device estimating a parameter related to retained lubricant in a plurality of other components of the refrigeration apparatus and subtracting the estimate of the parameter related to retained lubricant from a parameter related to a known total lubricant in the refrigeration apparatus.  
   
   
       6 . The refrigeration apparatus of  claim 5 , wherein the first component of the refrigeration apparatus is a compressor.  
   
   
       7 . The refrigeration apparatus of  claim 5 , wherein the plurality of other components of the refrigeration apparatus comprise at least one of an evaporator, an accumulator, a suction gas line, a discharge gas line, a condenser, a liquid line and a receiver.  
   
   
       8 . The refrigeration apparatus of  claim 5 , wherein the parameter related to retained lubricant in the plurality of other components of the refrigeration apparatus is determined using one or more parameters related to the state of each component of the refrigeration apparatus.  
   
   
       9 . A method of monitoring a parameter related to lubricant in a component of a vapor compression cycle system, comprising: 
 detecting a parameter related to a state of the component; and    using the parameter related to the state of the component, estimating the parameter related to lubricant in the component.    
   
   
       10 . The method of clam  9 , further comprising using the parameter related to lubricant in the component to determine an amount of lubricant in the component.  
   
   
       11 . The method of clam  9 , further comprising using the parameter related to lubricant in the component to determine a concentration of lubricant in the component.  
   
   
       12 . The method of  claim 9 , wherein the component of the vapor compression cycle system is one of an evaporator, an accumulator, a suction gas line, a discharge gas line, a condenser, a liquid line and a receiver.  
   
   
       13 . A refrigeration apparatus comprising a device for monitoring a parameter related to lubricant in a component of the refrigeration apparatus, the device detecting a parameter related to a state of the component and, using the parameter related to the state of the component, estimating the parameter related to lubricant in the component.  
   
   
       14 . The refrigeration apparatus of clam  13 , wherein the apparatus uses the parameter related to lubricant in the component to determine an amount of lubricant in the component.  
   
   
       15 . The refrigeration apparatus of clam  13 , wherein the apparatus uses the parameter related to lubricant in the component to determine a concentration of lubricant in the component.  
   
   
       16 . The refrigeration apparatus of  claim 13 , wherein the component of the refrigeration apparatus is one of an evaporator, an accumulator, a suction gas line, a discharge gas line, a condenser, a liquid line and a receiver.  
   
   
       17 . A method of monitoring a parameter related to lubricant in a heat exchanger of a vapor compression cycle system, comprising: 
 determining a length of a two-phase portion of the heat exchanger; and    using the length of the two-phase portion of the heat exchanger, estimating the parameter related to lubricant in the heat exchanger.    
   
   
       18 . An apparatus for monitoring a parameter related to lubricant in a heat exchanger of a vapor compression cycle system, the apparatus determining a length of a two-phase portion of the heat exchanger and, using the length of the two-phase portion of the heat exchanger, estimating the parameter related to lubricant in the heat exchanger.  
   
   
       19 . A method of monitoring a parameter related to lubricant in a heat exchanger of a vapor compression cycle system, comprising: 
 determining a length of a single-phase portion of the heat exchanger; and    using the length of the single-phase portion of the heat exchanger, estimating the parameter related to lubricant in the heat exchanger.    
   
   
       20 . An apparatus for monitoring a parameter related to lubricant in a heat exchanger of a vapor compression cycle system, the apparatus determining a length of a single-phase portion of the heat exchanger and, using the length of the single-phase portion of the heat exchanger, estimating the parameter related to lubricant in the heat exchanger.