Indirect evaporative cooling of a gas using common product and working gas in a partial counterflow configuration

Abstract

An indirect evaporative cooler includes a number of heat transfer plates. Each plate has a wet side and a dry side, and the dry sides of adjacent plates face each other. The plate dry sides have low permeability to an evaporative liquid. Input air flows over the dry sides from an input end to an output end. Part of the input air becomes product air and exits at the output end. The rest of the input air passes through perforations in the plates to the other side of the plates to become working air. The other side of each plate is a wet side, which is wet by an evaporative liquid. Working gas flows over the wet side, evaporating the evaporative liquid and cooling the evaporative liquid, the plate, and finally the product gas by heat transfer. The perforations are formed both toward the input end of the plate and toward the output end of the plate. Part of the wet side of the plate, toward the output end of the plate, has a plurality of barriers placed to cause the working gas at that end of the plate to flow in a direction generally counter to the input air.

1 . A heat exchanger plate for use in an indirect evaporative cooling system, the plate comprising: 
 a dry side having low permeability to an evaporative liquid and formed to allow an input fluid to flow over its surface from an input end to an output end;    a wet side designed to have its surface wet by an evaporative liquid, and formed to allow a working gas to flow over its surface to evaporate the evaporative liquid; and    perforations formed in the plate to allow a portion of the input fluid to pass from the dry side to the wet side, the perforations placed both toward the input end of the plate and toward the output end of the plate;    wherein a portion of the wet side toward the input end of the plate forms channels for guiding the working air which passes through the input-end perforations in a direction generally transverse to the product air flow; and    wherein a portion of the wet side toward the output end of the plate further includes a plurality of barriers placed to cause the working air from the output-end perforations to flow in a direction generally counter to the product air.    
   
   
       2 . The plate of  claim 1  wherein the channels are generally perpendicular to the flow of input air.  
   
   
       3 . The plate of  claim 1 , wherein the barriers are elongated.  
   
   
       4 . The plate of  claim 3  wherein the barriers are oriented generally perpendicular to the input airflow.  
   
   
       5 . The plate of  claim 1  wherein the dry side further forms channels to guide the input air from the input end toward the output end.  
   
   
       6 . The plate of  claim 1  wherein the output-end perforations include output-end side-perforations along a side parallel to product air flow and output-end edge-perforations along an edge where the product air exits.  
   
   
       7 . The plate of  claim 1  wherein the barriers cause the working gas at the output end of the plate to flow in a circuitous route.  
   
   
       8 . An indirect evaporative cooler comprising: 
 a plurality of generally parallel, spaced apart plates wherein each plate has—   a dry side having low permeability to an evaporative liquid and formed to allow an input gas to flow over its surface from an input end to an output end,    a wet side designed to have its surface wet by an evaporative liquid, and formed to allow a working gas to flow over its surface to evaporate the evaporative liquid, and    perforations formed in the plate to allow a portion of the input gas to pass from the dry side to the wet side, the perforations placed both toward the input end of the plate and toward the output end of the plate,    wherein the dry sides of adjacent plates face each other, and    wherein a portion of the wet side toward the output end of the plate further includes a plurality of barriers placed to cause the working gas from the perforations toward the output end of the plate to follow a counter flow path to the input gas; and    means for providing input gas at the input side of the plates and exiting product gas at the output side of the plates; and    means for exiting working gas.    
   
   
       9 . The evaporative cooler of  claim 8 , wherein the channels are generally perpendicular to the flow of input air.  
   
   
       10 . The plate of  claim 8 , wherein the barriers are elongated.  
   
   
       11 . The plate of  claim 10  wherein the barriers are oriented generally perpendicular to the input airflow.  
   
   
       12 . The plate of  claim 8  wherein the dry side further forms channels to guide the input air from the input end toward the output end.  
   
   
       13 . The plate of  claim 8  wherein the output-end perforations include output-end side-perforations along a side parallel to product air flow and output-end edge-perforations along an edge where the product air exits.  
   
   
       14 . The plate of  claim 8  wherein the barriers cause the working gas at the output end of the plate to flow in a circuitous route.