Heat and mass transfer devices with wettable layers for forming falling films

Abstract

A falling film of liquid desiccant in direct contact with a gas stream is formed, which allows water vapor transfer between a gas stream (air) and the desiccant, enabling dehumidification and/or humidification of air. Thin films are created in one way by a wettable layer that is in contact with a support structure and in another way directly on the support structure. The devices can be installed on an absorber (conditioner) side or a desorber (regenerator) side or both of air conditioning systems; for example, liquid desiccant air conditioning (LDAC) applications.

1 . A heat and mass transfer component for water vapor exchange with a liquid desiccant, the component comprising:
 a support structure; and   a wettable layer in contact with the support structure;   wherein the wettable layer has a surface that is substantially smooth.   
     
     
         2 . The heat and mass transfer component of  claim 1 , wherein the wettable layer is effective to form a falling film of the liquid desiccant upon receipt of a gravity feed of the liquid desiccant. 
     
     
         3 . The heat and mass transfer component of  claim 1 , wherein the wettable layer is effective to form a thin film of the liquid desiccant upon receipt of a gravity feed of the liquid desiccant. 
     
     
         4 . The heat and mass transfer component of  claim 1 , wherein the wettable layer is discrete from the support structure. 
     
     
         5 . The heat and mass transfer component of  claim 1 , wherein the wettable layer has a thickness in the range of 1 to 50 mils. 
     
     
         6 . The heat and mass transfer component of  claim 1  having a multi-scale. 
     
     
         7 . The heat and mass transfer component of  claim 1 , wherein the wettable layer comprises a membrane or a fibrous sheet. 
     
     
         8 . The heat and mass transfer component of  claim 7 , wherein the wettable layer comprises a fibrous sheet with fibers oriented substantially parallel to the plane of the support structure. 
     
     
         9 . The heat and mass transfer component of  claim 7 , wherein the wettable layer comprises a microporous membrane having an average pore size in the range of from about 0.02 to about 10.0 microns and a maximum pore size in the range of 0.1 to 15 microns. 
     
     
         10 . The heat and mass transfer component of  claim 1 , wherein the wettable layer in a dry state fully wets a drop of a nominal 35% by weight solution of lithium chloride in 300 seconds or less. 
     
     
         11 . The heat and mass transfer component of  claim 8 , wherein the wettable layer comprises a fibrous sheet comprising a plasma-treated spunbond polyester. 
     
     
         12 . The heat and mass transfer component of  claim 9 , wherein the wettable layer comprises a porous membrane comprising a plasma-treated nylon membrane whose surface is oxidized and comprises silicon oxides, silicon hydrides, and/or silicon hydroxides. 
     
     
         13 . The heat and mass transfer component of  claim 1 , wherein the wettable layer further comprises one or more draw-and-drip features. 
     
     
         14 . The heat and mass transfer component of  claim 1 , wherein the support structure comprises a frame or a plate. 
     
     
         15 . The heat and mass transfer component of  claim 14 , wherein the frame or the plate comprises a thermoset plastic, a thermoplastic, a cellulosic material, or a coated metal. 
     
     
         16 . The heat and mass transfer component of  claim 1 , wherein the support structure comprises a plate comprising an internal fluid channel for a heat transfer fluid. 
     
     
         17 . A heat and mass transfer panel comprising:
 the heat and mass transfer component according to  claim 1 ;   a gas contact zone adjacent to the wettable layer of the heat and mass transfer component; and   a fluid distribution system proximate an inlet end of the wettable layer.   
     
     
         18 . The heat and mass transfer panel of  claim 17 , wherein the wettable layer is in a gap defined by a portion to the fluid distribution system and the support structure. 
     
     
         19 . The heat and mass transfer panel of  claim 17 , wherein a surface of the fluid distribution system comprises a desiccant-phobic coating. 
     
     
         20 . The heat and mass transfer panel of  claim 17 , wherein the fluid distribution system comprises a manifold that is in fluid communication with the wettable layer. 
     
     
         21 . The heat and mass transfer panel of  claim 17 , wherein the fluid distribution system comprises a header that is adjacent to the wettable layer and/or the support structure of the heat and mass transfer component. 
     
     
         22 . The heat and mass transfer panel of  claim 21 , wherein the header is integral to the support structure. 
     
     
         23 . The heat and mass transfer panel of  claim 17  further comprising a fluid collection system proximate an outlet end of the wettable layer. 
     
     
         24 . The heat and mass transfer panel of  claim 23 , wherein the fluid collection system comprises a vessel that is in fluid communication with the wettable layer. 
     
     
         25 . The heat and mass transfer panel of  claim 17 , wherein the fluid collection system comprises a footer that is adjacent to the wettable layer and/or the support structure of the heat and mass transfer component. 
     
     
         26 . The heat and mass transfer panel of  claim 24 , wherein the footer is integral to the support structure. 
     
     
         27 . The heat and mass transfer panel of  claim 24 , wherein the footer comprises a stepped feature to form a reservoir defined by the footer and the wettable layer at the outlet end. 
     
     
         28 . A heat and mass transfer panel comprising:
 a support structure;   at least one wettable layer in contact with the support structure, the layer comprising one or more draw-and-drip features;   a plurality of gas contact zones adjacent to the layers;   a fluid distribution system comprising a plurality of headers adjacent to the support structures at an inlet end of the layer; and   a fluid collection system comprising a plurality of footers adjacent to the support structures at an outlet end of the layer, each footer comprising a stepped feature to form a reservoir defined by the footer and the layer at the outlet end;   wherein the at least one layer is effective to form a falling film of the liquid desiccant upon receipt of a gravity feed of the liquid desiccant.   
     
     
         29 . The heat and mass transfer panel of  claim 28  further comprising an effective gap defined between the header and the surface of the support structure, wherein a flux through a face width of the layer is in the range of 0.05 to 20 ml/min/inch. 
     
     
         30 . The heat and mass transfer panel of  claim 28 , wherein a surface of the header comprises a desiccant phobic coating. 
     
     
         31 . The heat and mass transfer panel of  claim 28 , further comprising a gap material located between the header and the surface of the support structure. 
     
     
         32 . The heat and mass transfer panel of  claim 31 , wherein a first wettable layer is in contact with the support structure and a second wettable layer is in contact with the first wettable layer, and the gap material is located between the first and second wettable layers. 
     
     
         33 . The heat and mass transfer panel of  claim 32 , wherein the first and second wettable layers comprise a spunbond polyester media and the gap material comprises an apertured polymeric film. 
     
     
         34 . A method for water vapor exchange between air and a liquid desiccant, the method comprising:
 contacting the heat and mass transfer panel according to  claim 17  with air having a water vapor pressure different from the equilibrium vapor pressure in the liquid desiccant forming a film on the wettable layer of the heat and mass transfer component;   wherein the humidity of the air after contact with the panel is different from the humidity before contact with the panel.   
     
     
         35 . A method of making a heat and mass transfer panel, the method comprising:
 obtaining a wettable layer;   optionally providing one or more features on a surface of the layer to provide a multi-scale;   contacting the wettable layer with a support structure to form a heat and mass transfer component;   providing a fluid distribution system proximate to an inlet end of the component to form a heat and mass transfer panel.   
     
     
         36 . The method of  claim 35  comprising the step of providing one or more features on a surface the layer in the form of embossing, calendaring, forming phobic patterns, or combinations thereof.