Refrigerant repelling surfaces

Abstract

Methods and devices for dropwise condensation of a refrigerant vapor on a surface are provided. The surface and various aspects of the system are configured to ensure the surface is refrigerant repelling, enhances droplet mobility, increases condensation rate and/or increases heat transfer rate. The refrigerant repelling surface may be configured so that a refrigerant that may normally wet a flat non-textured surface is instead repelled

1 . A method for condensation heat transfer comprising condensing a refrigerant vapor on a textured portion of an interior surface of a chamber to form a plurality of refrigerant droplets at a user selected pressure, thereby transferring heat from the refrigerant vapor to the interior surface wherein the user selected pressure is not atmospheric pressure, the textured portion of the interior surface comprises surface features, the surface features comprising a surface material and the apparent contact angle of the refrigerant droplets on the surface features is non-zero and greater than the characteristic contact angle of the refrigerant droplets on the surface material of the surface features. 
     
     
         2 . The method of  claim 1 , wherein the characteristic contact angle for the refrigerant droplets on the surface material is less than 50°. 
     
     
         3 . The method of  claim 2  wherein the characteristic contact angle is less than or equal to 20°. 
     
     
         4 . The method of  claim 1 , wherein the apparent contact angle of the refrigerant droplets on the surface features is greater than 90°. 
     
     
         5 . The method of  claim 1  wherein the difference between the apparent contact angle and the characteristic contact angle is greater than 45°. 
     
     
         6 . The method of  claim 1  wherein the atmosphere in the chamber substantially comprises refrigerant vapor. 
     
     
         7 . The method of  claim 1  wherein the refrigerant comprises a component selected from the group consisting of halocarbon, hydrofluorocarbon (HFC), hydrofluoroolefin (HFO) and a hydrocarbon (HC). 
     
     
         8 . The method of  claim 7 , wherein the refrigerant further comprises a lubricant. 
     
     
         9 . The method of  claim 8 , wherein the refrigerant comprises less than or equal to 50% lubricant by mass. 
     
     
         10 . The method of  claim 7  wherein the refrigerant has a molecular mass from 50 to 125. 
     
     
         11 . The method of  claim 7  wherein the component is selected from the group consisting of tetrafluoroethane (R134a) and 2,3,3,3-tetrafluoroprop-1-ene (HFO 1234yf) 
     
     
         12 . The method  claim 1  wherein the surface features provide a re-entrant geometry. 
     
     
         13 . The method of  claim 12 , wherein the surface features are micro mushrooms. 
     
     
         14 . The method of  claim 13 , wherein the micro mushrooms are characterized by the parameters D, W, R and H as shown in  FIG. 19  and D=40-70, W=20-100, R=25-40 and H=65-110. 
     
     
         15 . The method of  claim 1  wherein the surface features form a network or grid pattern. 
     
     
         16 . The method of  claim 1 , wherein the surface material is a polymer coating. 
     
     
         17 . The method of  claim 16  wherein the polymer is a fluoropolymer. 
     
     
         18 . The method of  claim 1  wherein the surface material is a silane coating. 
     
     
         19 . The method of  claim 1  wherein the user selected pressure is greater than atmospheric pressure and less than or equal to 5 MPa. 
     
     
         20 . The method of  claim 1  wherein the surface tension of the refrigerant is from 5 mN/m to 25 mN/m. 
     
     
         21 . A heat exchanger system for condensation heat transfer through condensation of a refrigerant vapor into droplets of the refrigerant, the heat exchanger system comprising: a chamber comprising an interior hollow portion and an interior surface, the interior surface comprising a textured portion, the textured portion of the surface comprising surface features, the surface features comprising a surface material
 wherein the apparent contact angle of the refrigerant droplets on the surface features is greater than the characteristic contact angle of the refrigerant droplets on the surface material of the surface features.   
     
     
         22 . The system of  claim 21  wherein the surface features provide a re-entrant geometry. 
     
     
         23 . The system of  claim 22  wherein the surface features are micro mushrooms. 
     
     
         24 . The system of  claim 23  wherein the micro mushrooms are characterized by the parameters D, W, R and H as shown in  FIG. 19  and D=40-70, W=20-100, R=25-40 and H=65-110. 
     
     
         25 . The system of  claim 21  wherein the surface features form a network or grid pattern. 
     
     
         26 . The system of  claim 21  wherein the surface material is a polymer coating. 
     
     
         27 . The system of  claim 26  wherein the polymer is a fluoropolymer. 
     
     
         28 . The system of  claim 21  wherein the surface material is a silane coating. 
     
     
         29 . The system of  claim 21 , further comprising a refrigerant positioned in the hollow portion of the chamber, the refrigerant comprising a component selected from the group consisting of halocarbon, hydrofluorocarbon (HFC), hydrofluoroolefin (HFO) and hydrocarbon (HC). 
     
     
         30 . The system of  claim 29  wherein the refrigerant is selected from the group consisting of tetrafluoroethane (R134a) and 2,3,3,3-tetrafluoroprop-1-ene (HFO 1234yf) 
     
     
         31 . The system of  claim 21  wherein the characteristic contact angle is less than or equal to 20°. 
     
     
         32 . The system of  claim 21  wherein the difference between the apparent contact angle and the characteristic contact angle is greater than 45°.