Indirect evaporative cooling heat exchanger

Abstract

A heat exchanger including a header having a plurality of header openings with conduits that may be made of plastic are inserted in the openings. The conduits are sealed to the header to prevent leakage between the header and the tubes to prevent water and air leakage between the wet, scavenger air stream flowing through the tubes and a dry air stream flowing around the tubes. A method of making the heat exchanger includes providing the openings inwardly curving perimeter walls that allow for easy insertion of the tubes. A self-leveling sealant may be used to seal the heat exchange conduits to the header using, for example, a paint roller and/or a paint sprayer. The heat exchange conduits can include a plurality of stubby fins formed on the inner wall surface of the conduit.

What is claimed is: 
     
         1 . A heat exchanger for indirect evaporative cooling of a gas stream, comprising:
 at least one elongate heat exchange conduit, which accommodates fluid flow in an interior of the conduit,   the conduit being made of a polymeric material and including an inner wall surface and an outer wall surface,   the inner wall surface including a plurality of stubby fins arranged circumferentially along a perimeter of the inner wall surface and protruding into the interior of the conduit, the stubby fins having a maximum height dimension to maximum width dimension ratio in the range of from 3:1 to 1:1.   
     
     
         2 . The heat exchanger of  claim 1 , wherein the heat exchanger is configured so that gas flows through the interior of the heat exchange conduit, and so that liquid flows outside of the heat exchange conduit and contacts the outer wall surface. 
     
     
         3 . The heat exchanger of  claim 1 , wherein each of the stubby fins has a maximum height dimension to maximum width dimension ratio in the range of from 2:1 to 1:1. 
     
     
         4 . The heat exchanger of  claim 1 , wherein each of the stubby fins has a maximum height dimension to maximum width dimension ratio of about 3:2. 
     
     
         5 . The heat exchanger of  claim 1 , wherein each of the stubby fins has a maximum width dimension at a base, and the length of the base is from about 0.01 inches to about 0.3 inches. 
     
     
         6 . The heat exchanger of  claim 5 , wherein the length of the base is from about 0.03 inches to about 0.1 inches. 
     
     
         7 . The heat exchanger of  claim 1 , wherein the maximum height dimension of each of the plurality of fins is from about 0.02 inches to about 0.4 inches. 
     
     
         8 . The heat exchanger of  claim 1 , wherein the maximum height dimension of each of the plurality of fins is from about 0.04 inches to about 0.2 inches. 
     
     
         9 . The heat exchanger of  claim 1 , wherein each of the plurality of fins are circumferentially spaced apart from each other so that adjacent fins on the inner wall surface are separated by a distance b. 
     
     
         10 . The heat exchanger of  claim 9 , wherein the distance b is less than the maximum width dimension of each of the plurality of fins. 
     
     
         11 . The heat exchanger of  claim 9 , wherein the distance b is from about 0.01 inches to about 0.2 inches. 
     
     
         12 . The heat exchanger of  claim 11 , wherein a ratio of the maximum width dimension to the distance between adjacent fins b is in the range of from about 5:1 to 3:1. 
     
     
         13 . The heat exchanger of  claim 1 , wherein the at least one heat exchange conduit includes a plurality of outside fins formed on the outer wall surface. 
     
     
         14 . The heat exchanger of  claim 1 , wherein the polymeric material comprises polyvinylchloride. 
     
     
         15 . The heat exchanger of  claim 1 , wherein the at least one heat exchange conduit includes comprises a plurality of thermally conductive particles disposed in the polymeric plastic material. 
     
     
         16 . The heat exchanger of  claim 15 , wherein the plurality of thermally conductive particles comprises carbon nano-particles. 
     
     
         17 . The heat exchanger of  claim 1 , wherein the heat exchanger is configured such that air flows through the interior of the at least one heat exchange conduit, and air or water flows outside of the heat exchange conduit and contacts the outer wall surface. 
     
     
         18 . The heat exchanger of  claim 1 , further comprising a plurality of elongate heat exchange conduits that are spaced apart from each other in the heat exchanger. 
     
     
         19 . The heat exchanger of  claim 18 , further comprising at least one baffle member disposed between adjacent heat exchange conduits in the heat exchanger. 
     
     
         20 . The heat exchanger of  claim 19 , wherein the at least one baffle member comprises a polymeric material. 
     
     
         21 . The heat exchanger of  claim 1 , wherein
 the at least one heat exchange conduit is disposed substantially horizontally in the heat exchanger, and   a thermally-formed sump is disposed below the at least heat exchange conduit to collect particles washed out of the heat exchanger.   
     
     
         22 . A heat exchanger for indirect evaporative cooling of a gas stream, comprising:
 at least one elongate heat exchange conduit;   a first plate with a first outside surface and a first inside surface, the first plate having at least one first opening that defines a first opening perimeter wall in the first plate; and   a second plate having a second outside surface and a second inside surface, the second side plate having at least one second opening that defines a second opening perimeter wall in the second plate, the second inside surface of the second plate opposing the first inside surface of the first plate,   wherein:
 one end portion of the elongate heat exchange conduit is fitted into the first opening and in contact with the first opening perimeter wall, and another end portion of the elongate heat exchange conduit is fitted into the second opening and in contact with the second opening perimeter wall, 
 the first opening perimeter wall curves inwardly from the first outside surface of the first plate toward the second inside surface of the second plate, and 
 the second opening perimeter wall curves inwardly from the second outside surface of the second plate toward the first inside surface of the first plate. 
   
     
     
         23 . The heat exchanger of  claim 22 , wherein the first opening perimeter wall has a portion that curves inwardly and away from the heat exchange conduit. 
     
     
         24 . The heat exchanger of  claim 23 , wherein the second opening perimeter wall has a portion that curves inwardly and away from the heat exchange conduit. 
     
     
         25 . The heat exchanger of  claim 22 , wherein the first and second opening perimeter walls each include a first portion that curves inwardly and toward the heat exchange conduit, a second portion that curves inwardly and away from the heat exchange conduit, and a third portion that connects the first portion and the second portion, the first portion being closer to the respective outside surface of the first plate and second plate than the second and third portions. 
     
     
         26 . The heat exchanger of  claim 25 , wherein the third portions of the first and second opening perimeter walls contact the respective end portions of the heat exchange conduit. 
     
     
         27 . The heat exchanger of  claim 25 , further comprising an adhesive or sealant that is provided between (i) the first portion of the first opening perimeter wall, and (ii) the end portions of the heat exchange conduit. 
     
     
         28 . The heat exchanger of  claim 27 , wherein the adhesive or sealant is added by rolling it across the first outer surface of the first plate. 
     
     
         29 . A heat exchanger for indirect evaporative cooling of a gas stream, comprising:
 at least one elongate heat exchange conduit;   a first plate with a first outside surface and a first inside surface, the first plate having at least one first opening that defines a first opening perimeter wall in the first plate;   wherein:
 one end portion of the elongate heat exchange conduit is fitted into the first opening and in contact with the first opening perimeter wall, and 
 the first opening perimeter wall curves inwardly from the first outside surface of the first plate in the direction of elongation of the heat exchange conduit, and the first opening perimeter wall includes a portion that curves inwardly and away from the heat exchange conduit. 
   
     
     
         30 . A method of making the heat exchanger according to  claim 22  comprising:
 fitting the one end portion of the heat exchange conduit into the first opening so that one end of the heat exchange conduit is substantially flush with first outside surface of the first plate; 
 fitting the another end portion of the heat exchange conduit into the second opening so that another end of the heat exchange conduit is substantially flush with the second outside surface of the second plate; and 
 rolling an adhesive or sealant across at least one of the first outside surface and the second outside surface.