Refrigerant management in hvac systems

Abstract

Generally, management of refrigerant in an evaporator of an HVAC chiller is described. Methods, systems, and apparatuses to manage refrigerant in an evaporator can include one or combination of the following approaches: (1) by use of a refrigerant displacement array to physically prevent refrigerant from residing where the array is positioned; (2) by control of the interstitial velocity of refrigerant flow within the volume of the shell of an evaporator; (3) by a phase biased distribution of the refrigerant mixture, so that a gaseous portion is uniformly distributed into the evaporator shell, while liquid refrigerant and oil is distributed into the evaporator shell at a designated area; and (4) by preventing or reducing the occurrence of foaming inside the evaporator through anti-foaming surfaces, such as by the use of refrigerant phobic and lubricant phobic material(s). Refrigerant management can in turn improve the thermal performance and overall efficiency of the evaporator.

1 - 34 . (canceled) 
     
     
         35 . A refrigerant evaporator comprising:
 a shell including a refrigerant inlet and a refrigerant outlet, wherein a refrigerant mixture enters a volume in the shell from a lower portion of the shell;   a plurality of tubes disposed within the shell and carrying a process fluid including at least a first plurality of tubes being immersed in liquid refrigerant within the shell, and at least a second plurality of tubes being at least partially surrounded by a spray flow of the refrigerant mixture sprayed upwardly through an interstitial volume of the shell throughout at least the second plurality of tubes including between outer surfaces of the second plurality of tubes, wherein the spray flow of the refrigerant mixture comprises a refrigerant gas flow entraining liquid droplets of refrigerant; and   a baffle positioned and located adjacent the first plurality of tubes and immersed in the liquid refrigerant to displace the liquid refrigerant upwardly in the shell toward the second plurality of tubes and configured to reduce an interstitial flow area between tubes of the first plurality of tubes to increase an upward gas velocity of the refrigerant mixture through the interstitial volume of the shell and to maintain a target interstitial velocity of refrigerant flow suitable to attain the spray flow of the refrigerant mixture above a threshold interstitial velocity that does not attain the spray flow of the refrigerant mixture.   
     
     
         36 . The refrigerant evaporator of  claim 35 , wherein the threshold interstitial velocity is about 3 ft/s. 
     
     
         37 . The refrigerant evaporator of  claim 36 , wherein the target interstitial velocity is about 5 ft/s. 
     
     
         38 . The refrigerant evaporator of  claim 35 , wherein at least the first plurality of tubes includes a tube pitch configured for further attaining the spray flow of the refrigerant. 
     
     
         39 . The refrigerant evaporator of  claim 35 , further comprising a distributor disposed at the lower portion of the shell for distributing a gaseous portion of the refrigerant mixture. 
     
     
         40 . The refrigerant evaporator of  claim 35 , wherein the plurality of tubes is configured such that there is no liquid pool with bubbles. 
     
     
         41 . The refrigerant evaporator of  claim 35 , wherein the baffle is at least partially immersed in the liquid refrigerant to displace the liquid refrigerant. 
     
     
         42 . The refrigerant evaporator of  claim 35 , wherein the baffle is a first baffle, and wherein the refrigerant evaporator further includes a second baffle positioned adjacent the first plurality of tubes and immersed in the liquid refrigerant. 
     
     
         43 . The refrigerant evaporator of  claim 42 , wherein the second baffle is axially spaced from the first baffle along a length of the shell. 
     
     
         44 . The refrigerant evaporator of  claim 35 , wherein the plurality of tubes is oriented substantially horizontally relative to a support surface of the refrigerant evaporator. 
     
     
         45 . The refrigerant evaporator of  claim 35 , wherein tubes of the plurality of tubes are spaced relative to each other by a rectangular pitch. 
     
     
         46 . The refrigerant evaporator of  claim 35 , wherein at least a portion of the baffle is located between lower-most tubes in the first plurality of tubes and the shell. 
     
     
         47 . The refrigerant evaporator of  claim 35 , wherein the first plurality of tubes is arranged in a first row, wherein the second plurality of tubes is arranged in a second row, and wherein a number of tubes in the second row exceeds a number of tubes in the first row. 
     
     
         48 . The refrigerant evaporator of  claim 35 , wherein the baffle is a unitary construction and includes a plurality of apertures through which the corresponding first plurality of tubes are received. 
     
     
         49 . The refrigerant evaporator of  claim 35 , wherein the shell includes a first length, and the baffle includes a second length of at least 25% of the first length, and wherein the first length and the second length are along an axial direction of the first plurality of tubes. 
     
     
         50 . The refrigerant evaporator of  claim 49 , wherein each of the first plurality of tubes includes an outer diameter less than a diameter of apertures in the baffle in which the tubes are respectively received, thereby defining an annular gap separating each of the first plurality of tubes and the baffle, and the annular gap extends along the second length. 
     
     
         51 . The refrigerant evaporator of  claim 35 , wherein the baffle is further positioned and adjacent the second plurality of tubes. 
     
     
         52 . An apparatus for controlling a rate of heat exchange of refrigerant in a multi-dimensional environment comprising in combination or for assembly:
 a refrigerant evaporator having a shell configured to receive a refrigerant mixture, wherein the shell includes a refrigerant inlet and a refrigerant outlet, wherein the shell is configured such that the refrigerant mixture enters a volume in the shell from a lower portion of the shell;   a plurality of tubes disposed within the shell configured for traversing a process fluid, the plurality of tubes having an upper plurality of tubes configured for being immersed in liquid refrigerant within the shell, and a lower plurality of tubes configurable proximate to the upper plurality of tubes and configured to be at least partially surrounded by a spray flow of the refrigerant mixture sprayed upwardly through an interstitial volume of the shell throughout at least the upper plurality of tubes including between outer surfaces of the upper plurality of tubes, wherein the spray flow of the refrigerant mixture comprises a refrigerant gas flow entraining liquid droplets of refrigerant; and   one or more integral baffles configurable to be positioned adjacent to the lower plurality of tubes and capable of being immersed in the liquid refrigerant for displacing the liquid refrigerant upwardly in the shell toward the upper plurality of tubes and configured to reduce an interstitial flow area between tubes of the lower plurality of tubes to increase an upward gas velocity of the refrigerant mixture through the interstitial volume of the shell and to maintain a target interstitial velocity of refrigerant flow suitable to attain the spray flow of the refrigerant mixture above a threshold interstitial velocity that does not attain the spray flow of the refrigerant mixture.