Indirect evaporative cooler using membrane-contained liquid desiccant for dehumidification and flocked surfaces to provide coolant flow

Abstract

An apparatus for conditioning an inlet air stream. A first stage is provided with a dehumidifier cooling an air stream input by absorption of water vapor from the input air stream. A second stage is provided with an indirect evaporative cooler to receive a cooled portion of the input air stream and sensibly cool the received portion of the input air stream to a temperature range near the dew point temperature. A first portion of the sensibly cooled air stream is exhausted to a cooled space while a second portion is directed to a wet side of the indirect evaporative cooler and receives heat to sensibly cool the input air stream. A flow channel for the second portion of the sensibly cooled air stream in the indirect evaporative cooler is defined by a surface of a separation wall covered with wicking material acting to wick a stream of liquid coolant.

1 . An apparatus for dehumidifying air supplied to a space, comprising:
 a first flow channel for receiving a stream of inlet supply air, wherein the first flow channel is defined in part by a vapor permeable membrane;   a second flow channel adjacent to the first flow channel receiving a stream of liquid desiccant; and   a third flow channel adjacent to the second flow channel receiving a stream of exhaust air, whereby heat is transferred from the stream of inlet supply air to the stream of exhaust air in the third flow channel via the stream of liquid desiccant,   wherein the third flow channel is defined in part by a first surface of a separation wall, wherein the separation wall is spaced apart a distance from the vapor permeable membrane, and wherein a layer of wicking material is provided on the first surface acting to wick a stream of liquid coolant.   
     
     
         2 . The apparatus of  claim 1 , wherein the second flow channel is defined by the vapor permeable membrane and a second surface of a separation wall, opposite the first surface, that is impermeable to fluid. 
     
     
         3 . The apparatus of  claim 1 , wherein the stream of liquid coolant flow through the wicking material layer is gravity driven. 
     
     
         4 . The apparatus of  claim 1 , wherein the wicking material is knitted nylon fabric, polypropylene woven fabric, polypropylene non-woven fabric, adhesive-backed flocking fibers, or one or more fabrics coated with a hydrophilic coating and wherein the liquid desiccant comprises a salt solution and the liquid coolant comprises water. 
     
     
         5 . The apparatus of  claim 1 , wherein the layer of wicking material comprises a hydrophilic coating on the first surface of the separation wall. 
     
     
         6 . The apparatus of  claim 1 , wherein the exhaust air comprises a portion of the stream of inlet supply air exiting the first flow channel at about the second, lower enthalpy. 
     
     
         7 . The apparatus of  claim 1 , wherein the stream of inlet supply air flows in a first direction in the first flow channel and the stream of exhaust air flows in a second direction in the third flow channel, the second direction being in at least one of cross or counter to the first direction, and wherein the third flow channel is arranged such that the exhaust air stream flows in an at least a partially cross or counter flow direction relative to the stream of inlet supply air in the first flow channel. 
     
     
         8 . A method of conditioning a supply air stream, comprising:
 dehumidifying the supply air stream to provide a dehumidified air stream, wherein the dehumidifying includes directing the supply air stream through a first channel defined by a surface of a vapor permeable membrane containing liquid desiccant; and   transferring heat from the liquid desiccant to a layer of coolant flowing in a second channel adjacent to the liquid desiccant.   
     
     
         9 . The method of  claim 8 , wherein the layer of coolant comprises coolant flowing in a layer of wicking material positioned for heat transfer from the liquid desiccant and wherein the method further includes evaporating a portion of the coolant flowing in the layer of wicking material into an air stream flowing adjacent to the layer of wicking material. 
     
     
         10 . The method of  claim 9 , wherein the coolant in the layer is flowing at a flow rate of less than about 50 inches per minute. 
     
     
         11 . The method of  claim 8 , wherein a temperature of the supply air stream is increased during the dehumidifying less than about 5° F. 
     
     
         12 . The method of  claim 8 , wherein the dewpoint temperature of the supply air stream is decreased during the dehumidifying to less than about 55° F. 
     
     
         13 . An apparatus for conditioning an inlet air stream, comprising:
 a first stage comprising a dehumidifier operable for cooling an air stream input to an inlet of the dehumidifier by absorption of water vapor from the input air stream; and   a second stage comprising an indirect evaporative cooler in fluid communication with an outlet of the first stage to receive a cooled portion of the input air stream, wherein the indirect evaporative cooler is operable to sensibly cool the received and cooled portion of the input air stream to a temperature range less than the wet bulb temperature and greater than the dew point temperature of the input air stream;   wherein a first portion of the sensibly cooled air stream is supplied to a cooled space, and   wherein a second portion of the sensibly cooled air stream is directed to a wet side of the indirect evaporative cooler and receives heat from the received and cooled portion of the input air stream.   
     
     
         14 . The apparatus of  claim 13 , wherein the dehumidifier performs the cooling using a membrane-contained liquid desiccant cooled by an indirect evaporative channel that includes a wicking layer containing a flow of coolant. 
     
     
         15 . The apparatus of  claim 13 , wherein the dehumidifier performs the cooling using a membrane-contained liquid desiccant that is liquid cooled. 
     
     
         16 . The apparatus of  claim 13 , wherein the second portion comprises 10 to 40 percent of the received and cooled portion of the input air. 
     
     
         17 . The apparatus of  claim 13 , wherein a flow channel for the second portion of the sensibly cooled air stream in the indirect evaporative cooler is defined in part by a surface of a separation wall and wherein a layer of wicking material is provided on the surface acting to wick a stream of liquid coolant adjacent the flow channel. 
     
     
         18 . The apparatus of  claim 13 , further comprising a direct evaporative stage between the second stage and the cooled space, wherein the direct evaporative stage receives the first portion of the sensibly cooled air stream and provides additional cooling via direct evaporative cooling prior to supplying the first portion of the sensibly cooled air stream to the cooled space. 
     
     
         19 . The apparatus of  claim 18 , wherein the direct evaporative stage is adapted to contain flow of water with a vapor permeable membrane or within a layer of wicking material. 
     
     
         20 . The apparatus of  claim 19 , wherein the layer of wicking material is provided as a surface with a hydrophilic coating. 
     
     
         21 . A method for conditioning a supply air stream, comprising:
 cooling an air stream by absorption of water vapor from the air stream to a first wet bulb temperature and first dewpoint temperature;   after the cooling by absorption, using indirect evaporative cooling to sensibly cool the air stream to a second temperature; and   supplying a first portion of the sensibly cooled air stream to a space, wherein a second portion of the sensibly cooled air stream is used to perform the indirect evaporative cooling of the air stream.   
     
     
         22 . The method of  claim 21 , wherein the second temperature is less than the first wet bulb temperature and greater than the first dewpoint temperature and the cooling is performed using membrane-contained liquid desiccant or with a liquid coolant flowing on a separation wall covered with a layer of wicking material or a hydrophilic coating. 
     
     
         23 . The method of  claim 21 , further comprising, prior to the supplying the first portion to the space, humidifying the sensibly cooled air stream by providing a flow of water adjacent to the sensibly cooled air stream, wherein the flow of water with a vapor permeable membrane or within a layer of wicking material. 
     
     
         24 . The method of  claim 21 , further comprising, prior to the supplying the first portion to the space, providing additional cooling to the sensibly cooled air stream via direct evaporative cooling.