Collapsible coaxial flex duct

Abstract

A heating, ventilation, and air conditioning (HVAC) system for a structure having at least one area to be conditioned includes a blower configured to force an airflow through the HVAC system and a duct assembly in airflow communication with the blower. The duct assembly includes a first duct defining a flow path for a first fluid having a first temperature and a second duct having a hollow interior defining a flow path for a second fluid having a second temperature different from the first temperature. The first duct is arranged within the hollow interior of the second duct such that heat is transferred between the first fluid and the second fluid. At least one of the first duct and the second duct is formed from a collapsible material.

What is claimed is: 
     
         1 . A heating, ventilation, and air conditioning (HVAC) system for a structure having at least one area to be conditioned comprising:
 a blower configured to force an airflow through the HVAC system; and   a duct assembly in airflow communication with the blower, the duct assembly comprising:
 a first duct defining a flow path for a first fluid having a first temperature; and 
 a second duct having a hollow interior defining a flow path for a second fluid having a second temperature different from the first temperature, the first duct being arranged within the hollow interior of the second duct such that heat is transferred between the first fluid and the second fluid; 
 wherein at least one of the first duct and the second duct is formed from a collapsible material. 
   
     
     
         2 . The HVAC system of  claim 1 , wherein the first duct and the second duct are arranged concentrically. 
     
     
         3 . The HVAC system of  claim 1 , further comprising at least one mounting bracket arranged within the hollow interior to mount the first duct within the second duct. 
     
     
         4 . The HVAC system of  claim 3 , wherein the at least one mounting bracket is formed from a spring steel. 
     
     
         5 . The HVAC system of  claim 3 , wherein the at least one mounting bracket is configured to allow a flow of air therethrough. 
     
     
         6 . The HVAC system of  claim 3 , wherein the at least one mounting bracket has a spiral-like configuration extending over an axial length of the first duct and the second duct. 
     
     
         7 . The HVAC system of  claim 3 , wherein one of the first fluid and the second fluid is outside air and one of the first fluid and the second fluid is exhaust air. 
     
     
         8 . The HVAC system of  claim 1 , wherein the first duct has a water-permeable membrane such that water or water vapor is transferrable between the first fluid and the second fluid. 
     
     
         9 . The HVAC system of  claim 8 , further comprising a drain feature associated with at least one of the first duct and the second duct. 
     
     
         10 . The HVAC system of  claim 8 , wherein at least one of the first duct and the second duct has a vertical orientation to drain water or water vapor that has accumulated therein. 
     
     
         11 . The HVAC system of  claim 1 , wherein at least one of the first duct and the second duct comprises a plurality of connected duct portions. 
     
     
         12 . The HVAC system of  claim 1 , further comprising
 a coil unit including a heat exchanger, wherein the first duct is coupled to the coil unit and to an inlet opening arranged at an exterior of the structure.   
     
     
         13 . The HVAC system of  claim 12 , wherein the heat exchanger is an evaporator. 
     
     
         14 . The HVAC system of  claim 12 , wherein the coil unit includes a furnace, and the second fluid includes a mixture of air output from the at least one area to be conditioned and flue gas output from the furnace. 
     
     
         15 . The HVAC system of  claim 1 , further comprising a pressure sensor and a movement mechanism arranged within a nested portion of one of the first duct and the second duct. 
     
     
         16 . The HVAC system of  claim 15 , wherein operation of the movement mechanism is adjustable in response to the pressure sensor to balance a flow within the first duct and the second duct. 
     
     
         17 . A duct assembly for a heating, ventilation, and air conditioning (HVAC) system, the duct assembly comprising:
 a first duct defining a flow path for a first fluid having a first temperature; and   a second duct having a hollow interior defining a flow path for a second fluid having a second temperature different from the first temperature, the first duct being arranged within the hollow interior of the second duct such that heat is transferred between the first fluid and the second fluid;   wherein at least one of the first duct and the second duct is formed from a collapsible material.   
     
     
         18 . The duct assembly of  claim 17 , wherein the first duct and the second duct are arranged concentrically. 
     
     
         19 . The duct assembly of  claim 17 , further comprising at least one mounting bracket arranged within the hollow interior to mount the first duct within the second duct. 
     
     
         20 . The duct assembly of  claim 17 , wherein the first duct has a water-permeable membrane such that water or water vapor is transferrable between the first fluid and the second fluid.