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 dimples disposed in the elliptical portion, and a third pass having an elliptical portion with dimples disposed in the elliptical portion. The first pass and the second pass may be connected in fluid communication by a first bend, and the second pass and the third pass may be connected in fluid communication by a second 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; and 
 a third pass; 
 wherein at least a portion of the second pass and at least a portion of the third pass comprises an elliptical portion. 
   
     
     
         2 . The heat exchanger of  claim 1 , wherein the second pass and the third pass do not overlap in a downstream direction with respect to the primary direction of an incoming airflow. 
     
     
         3 . The heat exchanger of  claim 2 , wherein a longitudinal axis of a major diameter of the elliptical portions are aligned with the primary direction of the incoming airflow. 
     
     
         4 . 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. 
     
     
         5 . The heat exchanger of  claim 4 , wherein the elliptical portion of the second pass and the elliptical portion of the third pass comprise substantially different reductions in minor diameter. 
     
     
         6 . The heat exchanger of  claim 1 , wherein each of the second pass and the third pass comprises a plurality of dimples. 
     
     
         7 . The heat exchanger of  claim 6 , wherein the dimples comprise spherical shaped indentions disposed along the elliptical portions of the second pass and the third pass, and wherein the dimples protrude inward along a lateral axis associated with a minor diameter of the elliptical portions. 
     
     
         8 . The heat exchanger of  claim 7 , wherein the dimples are configured to locally accelerate a flow of fluid travelling through internal passages of the second pass and the third pass near the dimples. 
     
     
         9 . The heat exchanger of  claim 8 , wherein the second pass comprises larger diameter dimples than the third 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; and 
 a third pass; 
 wherein at least a portion of the second pass and at least a portion of the third pass comprises an elliptical portion. 
   
     
     
         13 . The HVAC system of  claim 13 , 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 the elliptical portion of the third pass comprise substantially different reductions in minor diameter. 
     
     
         16 . The HVAC system of  claim 13 , wherein each of the second pass and the third pass comprises a plurality of dimples. 
     
     
         17 . The HVAC system of  claim 16 , wherein the dimples comprise spherical shaped indentions disposed along the elliptical portions of the second pass and the third pass, and wherein the dimples protrude inward along a lateral axis associated with a minor diameter of the elliptical portions. 
     
     
         18 . The HVAC system of  claim 17 , wherein the second pass comprises larger diameter dimples than the third 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, and a third pass, wherein at least a portion of the second pass and at least a portion of the third pass comprises an elliptical portion, and wherein each of the second pass and the third pass comprises a plurality of dimples;   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:
 locally accelerating a flow of fluid travelling through internal passages of the second pass and the third pass near the dimples to promote heat transfer the fluid and the airflow; and   reducing a pressure drop across the heat exchanger.