Heat Exchanger Fluid Circuit Arrangement

Abstract

An air coil unit of a heat exchanger includes tubes organized into separate circuits of serially connected tubes. The tubes of a given circuit are arranged in serially connected circuit portions, where the tubes of each circuit portion are arranged in rows. The circuits are arranged in a parallel flow-cross flow (PFCrF) configuration where the circuit crosses to adjacent rows between circuit portions to compensate for non-uniform air flow across the tubes. In the PFCrF circuit configuration, each circuit of the heat exchanger shares the non-uniformity of air flow, and mitigates the mal fluid distribution inside the tubes due to the non-uniform air flow across tubes.

What is claimed, is: 
     
         1 . An air coil unit of a heat exchanger, the air coil unit comprising
 a first tube sheet having a first surface that is parallel to the direction of air flow through the air coil unit;   a second tube sheet parallel to and spaced apart from the first tube sheet, the second tube sheet having a second surface that faces the first surface and is parallel to the direction of air flow through the air coil unit; and   thermally conductive tubes that extend between the first surface and the second surface, the tubes arranged so as to be
 transverse to the direction of air flow through the air coil unit, 
 parallel to each other tube, 
 spaced apart from adjacent tubes, 
 arranged into rows, each row defining a plane that is transverse to the direction of air flow through the air coil unit, the rows including a first row and a second row, where the second row is spaced apart from the first row in a direction downstream with respect to the direction of air flow through the air coil unit, 
   
       wherein
 a first subset of the tubes is serially connected to form a first circuit defining a single, continuous, unbranched first fluid path that extends between a first inlet and a first outlet, 
 the first circuit including a first portion of the first subset of the tubes that is disposed in the first row and a second portion of the first subset of the tubes that is disposed in the second row, 
 a second subset of the tubes is serially connected to form a second circuit defining a single, continuous, unbranched second fluid path that extends between a second inlet and a second outlet, 
 the second circuit including a first portion of the second subset of the tubes that is disposed in the first row and a second portion of the second subset of the tubes that is disposed in the second row, 
 the first inlet and the second inlet are in the first row, 
 the first outlet and the second outlet are in a row other than the first row, and 
 the first portion of the first subset of the tubes is aligned with the second portion of the second subset of the tubes when viewed in a direction parallel to the direction of air flow through the air coil unit. 
 
     
     
         2 . The air coil unit of  claim 1 , wherein the first portion of the second subset of the tubes is aligned with the second portion of the first subset of the tubes when viewed in a direction parallel to the direction of air flow through the air coil unit. 
     
     
         3 . The air coil unit of  claim 1 , wherein
 the rows include a third row that is spaced apart from the first row in a direction downstream with respect to the direction of air flow through the air coil unit, and   the first circuit includes a third portion of the first subset of the tubes that is disposed in the third row and is aligned with the first portion of the first subset of the tubes when viewed in a direction parallel to the direction of air flow through the air coil unit.   
     
     
         4 . The air coil unit of  claim 3 , wherein the third row is disposed between the first row and the second row. 
     
     
         5 . The air coil unit of  claim 3 , wherein
 the rows include a fourth row that is spaced apart from the first row in a direction downstream with respect to the direction of air flow through the air coil unit, and   the first circuit includes a fourth portion of the first subset of the tubes that is disposed in the fourth row and is aligned with the first portion of the second subset of the tubes when viewed in a direction parallel to the direction of air flow through the air coil unit.   
     
     
         6 . The air coil unit of  claim 5 , wherein the fourth row is disposed between the third row and the second row. 
     
     
         7 . The air coil unit of  claim 1 , wherein the first outlet and the second outlet are in the second row. 
     
     
         8 . The air coil unit of  claim 1 , wherein the heat exchanger is a fin-and-tube heat exchanger. 
     
     
         9 . The air coil unit of  claim 1 , wherein
 a third subset of the tubes is serially connected to form a third circuit defining, a single, continuous, unbranched third fluid path that extends between a third inlet and a third outlet,   the third circuit including a first portion of the third subset of the tubes that is disposed in the first row and a second portion of the third subset of the tubes that is disposed in the second row,   a fourth subset of the tubes is serially connected to form a fourth circuit defining a single, continuous, unbranched fourth fluid path that extends between a fourth inlet and a fourth outlet,   the fourth circuit including a first portion of the fourth subset of the tubes that is disposed in the first row and a second portion of the fourth subset of the tubes that is disposed in the second row,   the third inlet and the fourth inlet are in the first row,   the third outlet and the fourth outlet are in a row other than the first row, and   the first portion of the third subset of the tubes is aligned with the second portion of the fourth subset of tubes when viewed in a direction parallel to the direction of air flow through the air coil unit.   
     
     
         10 . The air coil unit of  claim 9 , wherein
 the first portion of the second subset of the tubes is disposed in the first row between the first portion of the first subset of the tubes and the first portion of the third subset of the tubes, and   the first portion of the fourth subset of the tubes is disposed in the first row adjacent to the first portion of the third subset of the tubes.   
     
     
         11 . A system for performing at least one of a heating, ventilating, air conditioning and refrigeration function, the system comprising a heat exchanger, the heat exchanger including an air coil unit having
 a first tube sheet having a first surface that is parallel to the direction of air flow through the air coil unit;   a second tube sheet parallel to and spaced apart from the first tube sheet, the second tube sheet having a second surface that faces the first surface and is parallel to the direction of air flow through the air coil unit; and   thermally conductive tubes that extend between the first surface and the second surface, the tubes arranged so as to be
 transverse to the direction of air flow through the air coil unit, 
 parallel to each other tube, 
 spaced apart from adjacent tubes, 
 arranged into rows, each row defining a plane that is transverse to the direction of air flow through the air coil unit, the rows including a first row and a second row, where the second row is spaced apart from the first row in a direction downstream with respect to the direction of air flow through the air coil unit, 
   
       wherein
 a first subset of the tubes is serially connected to form a first circuit defining a single, continuous, unbranched first fluid path that extends between a first inlet and a first outlet, 
 the first circuit including a first portion of the first subset of the tubes that is disposed in the first row and a second portion of the first subset of the tubes that is disposed in the second row, 
 a second subset of the tubes is serially connected to form a second circuit defining a single, continuous, unbranched second fluid path that extends between a second inlet and a second outlet, 
 the second circuit including a first portion of the second subset of the tubes that is disposed in the first row and a second portion of the second subset of the tubes that is disposed in the second row, 
 the first inlet and the second inlet are in the first row, 
 the first outlet and the second outlet are in a row other than the first row, 
 the first portion of the first subset of the tubes is aligned with the second portion of the second subset of the tubes when viewed in a direction parallel to the direction of air flow through the air coil unit. 
 
     
     
         12 . The system of  claim 11 , wherein the first portion of the second subset of the tubes is aligned with the second portion of the first subset of the tubes when viewed in a direction parallel to the direction of air flow through the air coil unit. 
     
     
         13 . The system of  claim 11 , wherein
 the rows include a third row that is spaced apart from the first row in a direction downstream with respect to the direction of air flow through the air coil unit, and   the first circuit includes a third portion of the first subset of the tubes that is disposed in the third row and is aligned with the first portion of the first subset of the tubes when viewed in a direction parallel to the direction of air flow through the air coil unit.   
     
     
         14 . The system of  claim 13 , wherein the third row is disposed between the first row and the second row. 
     
     
         15 . The system of  claim 13 , wherein
 the rows include a fourth row that is spaced apart from the first row in a direction downstream with respect to the direction of air flow through the air coil unit, and   the first circuit includes a fourth portion of the first subset of the tubes that is disposed in the fourth row and is aligned with the first portion of the second subset of the tubes when viewed in a direction parallel to the direction of air flow through the air coil unit.   
     
     
         16 . The system of  claim 15 , wherein the fourth row is disposed between the third row and the second row. 
     
     
         17 . The system of  claim 11 , wherein the first outlet and the second outlet are in the second row. 
     
     
         18 . The system of  claim 11 , wherein the heat exchanger is a fin-and-tube heat exchanger. 
     
     
         19 . The system of  claim 11 , wherein
 a third subset of the tubes is serially connected to form a third circuit defining a single, continuous, unbranched third fluid path that extends between a third inlet and a third outlet,   the third circuit including a first portion of the third subset of the tubes that is disposed in the first row and a second portion of the third subset of the tubes that is disposed in the second row,   a fourth subset of the tubes is serially connected to form a fourth circuit defining a single, continuous, unbranched fourth fluid path that extends between a fourth inlet and a fourth outlet,   the fourth circuit including a first portion of the fourth subset of the tubes that is disposed in the first row and a second portion of the fourth subset of the tubes that is disposed in the second row,   the third inlet and the fourth inlet are in the first row,   the third outlet and the fourth outlet are in a row other than the first row, and   the first portion of the third subset of the tubes is aligned with the second portion of the fourth subset of tubes when viewed in a direction parallel to the direction of air flow through the air coil unit.   
     
     
         20 . The system of  claim 19 , wherein
 the first portion of the second subset of the tubes is disposed in the first row between the first portion of the first subset of the tubes and the first portion of the thud subset of the tubes, and   the first portion of the fourth subset of the tubes is disposed in the first row adjacent to the first portion of the third subset of the tubes.