Enhanced Tubular Heat Exchanger

Abstract

A heating, ventilation, and/or air conditioning (HVAC) system may include a heat exchanger comprising at least one heat exchanger tube. The heat exchanger tube may include multiple passes: a first pass, a second pass having an elliptical portion with ribs disposed in the elliptical portion, a third pass having an elliptical portion with ribs disposed in the elliptical portion, and a fourth pass having an elliptical portion with ribs disposed in the elliptical portion. The first pass and the second pass may be connected in fluid communication by a first bend, the second pass and the third pass may be connected in fluid communication by a second bend, and the third pass and the fourth pass may be connected in fluid communication by a third bend. The heat exchanger tube may be configured to promote heat transfer while also controlling a pressure drop across the heat exchanger tube.

What is claimed is: 
     
         1 . A heat exchanger, comprising:
 at least one heat exchanger tube, comprising:
 a first pass; 
 a second pass; 
 a third pass; and 
 a fourth pass; 
 wherein at least a portion of each of the second pass, the third pass, and the fourth pass comprises an elliptical portion. 
   
     
     
         2 . The heat exchanger of  claim 1 , wherein a longitudinal axis of a major diameter of the elliptical portions are aligned with the primary direction of the incoming airflow. 
     
     
         3 . The heat exchanger of  claim 1 , wherein the elliptical portions comprise at least about a 10% reduction in a minor diameter of the elliptical portions. 
     
     
         4 . The heat exchanger of  claim 3 , wherein the elliptical portion of the second pass and the elliptical portion of the third pass comprise substantially different reductions in minor diameter. 
     
     
         5 . The heat exchanger of  claim 4 , wherein the elliptical portion of the third pass and the elliptical portion of the fourth pass comprise substantially similar reductions in minor diameter. 
     
     
         6 . The heat exchanger of  claim 1 , wherein each of the second pass, the third pass, and the fourth pass comprises a plurality of ribs. 
     
     
         7 . The heat exchanger of  claim 6 , wherein the ribs comprise linear indentions disposed along the elliptical portions of the second pass, the third pass, and the fourth pass, and wherein the ribs protrude inward along a lateral axis associated with a minor diameter of the elliptical portions of the second pass, the third pass, and the fourth pass. 
     
     
         8 . The heat exchanger of  claim 7 , wherein the ribs are configured to locally accelerate a flow of fluid travelling through internal passages of the second pass and the third pass near the ribs. 
     
     
         9 . The heat exchanger of  claim 8 , wherein the second pass comprises a larger internal passage than each internal passage of the third pass and the fourth pass. 
     
     
         10 . The heat exchanger of  claim 1 , wherein the heat exchanger comprises a plurality of heat exchanger tubes. 
     
     
         11 . The heat exchanger of  claim 10 , wherein the heat exchanger comprises a primary heat exchanger of a furnace. 
     
     
         12 . A heating, ventilation and/or air conditioning (HVAC) system, comprising:
 a heat exchanger, comprising:
 at least one heat exchanger tube, comprising: 
 a first pass; 
 a second pass; 
 a third pass; and 
 a fourth pass; 
 wherein at least a portion of each of the second pass, the third pass, and the fourth pass comprises an elliptical portion. 
   
     
     
         13 . The HVAC system of  claim 12 , wherein a longitudinal axis of a major diameter of the elliptical portions are aligned with the primary direction of the incoming airflow. 
     
     
         14 . The HVAC system of  claim 13 , wherein the elliptical portions comprise at least about a 10% reduction in a minor diameter of the elliptical portions. 
     
     
         15 . The HVAC system of  claim 14 , wherein the elliptical portion of the second pass and at least one of the elliptical portions of the third pass and the fourth pass comprise substantially different reductions in minor diameter. 
     
     
         16 . The HVAC system of  claim 13 , wherein each of the second pass, the third pass, and the fourth pass comprises a plurality of ribs. 
     
     
         17 . The HVAC system of  claim 16 , wherein the ribs comprise linear indentions disposed along the elliptical portions of the second pass, the third pass, and the fourth pass, and wherein the ribs protrude inward along a lateral axis associated with a minor diameter of the elliptical portions of the second pass, the third pass, and the fourth pass. 
     
     
         18 . The HVAC system of  claim 17 , wherein the second pass comprises a larger internal passage than each internal passage of the third pass and the fourth pass. 
     
     
         19 . The HVAC system of  claim 13 , wherein the heat exchanger comprises a plurality of heat exchanger tubes. 
     
     
         20 . The HVAC system of  claim 19 , wherein the heat exchanger comprises a primary heat exchanger of a furnace. 
     
     
         21 . A method of operating a heating, ventilation, and/or air conditioning (HVAC) system, comprising:
 providing at least one heat exchanger tube in a heat exchanger of the HVAC system, the at least one heat exchanger tube comprising a first pass, a second pass, a third pass, and a fourth pass, wherein at least a portion of each of the second pass, the third pass, and the fourth pass comprises an elliptical portion, and wherein at least one pass comprises a plurality of ribs;   generating an airflow;   contacting the at least one heat exchanger tube with the airflow; and   promoting heat transfer between a fluid passing through an internal passage of the at least one heat exchanger tube and the airflow.   
     
     
         22 . The method of  claim 21 , further comprising:
 providing each of the second pass, the third pass, and the fourth pass with a plurality of ribs;   locally accelerating a flow of fluid travelling through internal passages of the second pass and the third pass near the ribs to promote heat transfer the fluid and the airflow; and   reducing a pressure drop across the heat exchanger.