Heat exchanger assembly and method for hvac system

Abstract

An HVAC heat exchanger with an array of tubes including one or more dead tubes is provided. In one embodiment, the heat exchanger is a microchannel heat exchanger operable to exchange heat with air in an HVAC system via refrigerant passing through the microchannel heat exchanger. The microchannel heat exchanger includes an array of flat tubes arranged between a first manifold and a second manifold. The array of flat tubes includes multiple tubes coupled in fluid communication with the first manifold and the second manifold to convey refrigerant between the first manifold and the second manifold through microchannels of the multiple tubes. The array of flat tubes also includes one or more dead tubes that do not convey refrigerant between the first manifold and the second manifold. Additional systems, devices, and methods are also disclosed.

1 . An apparatus comprising:
 a microchannel heat exchanger operable to exchange heat with air in an HVAC system via refrigerant passing through the microchannel heat exchanger, the microchannel heat exchanger including:
 a first manifold; 
 a second manifold; and 
 an array of flat tubes arranged between the first manifold and the second manifold, wherein the array of flat tubes includes multiple tubes coupled in fluid communication with the first manifold and the second manifold to convey refrigerant between the first manifold and the second manifold through microchannels of the multiple tubes, and the array of flat tubes also includes one or more dead tubes that do not convey refrigerant between the first manifold and the second manifold; wherein the array of flat tubes includes a first outer flat tube that is at one end of the array, a second outer flat tube that is at an opposite end of the array, and a plurality of inner flat tubes located between, and in parallel with, the first outer flat tube and the second outer flat tube; wherein the first outer flat tube is a dead tube of the one or more dead tubes; and wherein an inner flat tube closest to the first outer flat tube within the array is an additional dead tube of the one or more dead tubes. 
   
     
     
         2 . The apparatus of  claim 1 , wherein the microchannel heat exchanger is a multi-pass microchannel heat exchanger configured such that, in operation, a first subset of flat tubes of the array of flat tubes conveys the refrigerant from the first manifold to the second manifold and a second subset of flat tubes of the array of flat tubes returns the refrigerant from the second manifold to the first manifold. 
     
     
         3 . The apparatus of  claim 2 , wherein the one or more dead tubes includes at least one dead tube positioned between a first flat tube that conveys refrigerant from the first manifold to the second manifold and a second flat tube that conveys refrigerant from the second manifold to the first manifold such that the at least one dead tube reduces thermal cross-conduction between the first flat tube and the second flat tube. 
     
     
         4 . The apparatus of  claim 3 , wherein the at least one dead tube is positioned at a location within the array such that the presence of the at least one dead tube at the location reduces thermal stress at the location compared to thermal stress that would be at the location if the at least one dead tube were instead a live tube. 
     
     
         5 - 7 . (canceled) 
     
     
         8 . The apparatus of  claim 1 , wherein the second outer flat tube and an inner flat tube closest to the second outer flat tube within the array are additional dead tubes of the one or more dead tubes. 
     
     
         9 . The apparatus of  claim 1 , comprising a baffle in the first manifold that divides a first pass of the microchannel heat exchanger from a second pass of the microchannel heat exchanger. 
     
     
         10 . The apparatus of  claim 9 , wherein the first pass and the second pass are separated within the array of flat tubes by at least one dead tube of the one or more dead tubes. 
     
     
         11 . The apparatus of  claim 1 , wherein the microchannel heat exchanger includes fins disposed in the array of flat tubes to facilitate heat exchange between the microchannel heat exchanger and the air. 
     
     
         12 . The apparatus of  claim 1 , wherein the microchannel heat exchanger is installed in the HVAC system. 
     
     
         13 - 15 . (canceled) 
     
     
         16 . The apparatus of  claim 1 , wherein at least one dead tube of the one or more dead tubes separates two adjacent passes of the microchannel heat exchanger. 
     
     
         17 . The apparatus of  claim 16 , wherein the microchannel heat exchanger is a condenser, and the two adjacent passes include a first de-superheating pass and a subsequent pass of the condenser. 
     
     
         18 . The apparatus of  claim 16 , wherein the microchannel heat exchanger is a condenser, and one of the two adjacent passes is a last subcooling pass of the condenser. 
     
     
         19 . The apparatus of  claim 16 , wherein the microchannel heat exchanger is an evaporator, and one of the two adjacent passes is a last superheating pass of the evaporator. 
     
     
         20 . An HVAC system comprising:
 a compressor;   a blower; and   a microchannel heat exchanger operable to exchange heat with air in the HVAC system via refrigerant passing through the microchannel heat exchanger, wherein the microchannel heat exchanger includes an array of tubes arranged between a first manifold and a second manifold, the array of tubes includes live tubes coupled to the first manifold and the second manifold in a manner that allows refrigerant to pass between the first manifold and the second manifold via the live tubes, and the array of tubes includes one or more dead tubes that are not coupled to the first manifold and the second manifold in a manner that allows refrigerant to pass between the first manifold and the second manifold via the one or more dead tubes; and wherein the array of tubes includes a pair of outermost tubes positioned at opposite sides of the microchannel heat exchanger, the pair of outermost tubes includes a first outer tube and a second outer tube, the first outer tube is a dead tube of the one or more dead tubes, and the array of tubes includes an additional tube that is adjacent to the first outer tube and is also a dead tube of the one or more dead tubes.   
     
     
         21 . (canceled) 
     
     
         22 . The HVAC system of  claim 20 , wherein the array of tubes includes an array of flat tubes. 
     
     
         23 . The HVAC system of  claim 20 , wherein the HVAC system includes a packaged HVAC unit with the compressor, blower, and microchannel heat exchanger in a shared cabinet. 
     
     
         24 . (canceled) 
     
     
         25 . A method comprising:
 providing an array of flat microchannel tubes arranged between a first manifold and a second manifold of a microchannel heat exchanger operable to exchange heat with air in an HVAC system via refrigerant passing through the microchannel heat exchanger, wherein the microchannel heat exchanger includes the first manifold, the second manifold, and the array of flat microchannel tubes; and   wherein the array of flat microchannel tubes includes a first outer flat microchannel tube that is at one end of the array, a second outer flat microchannel tube that is at an opposite end of the array, and a plurality of inner flat microchannel tubes located between, and in parallel with, the first outer flat microchannel tube and the second outer flat microchannel tube; and   preventing fluid communication between the first manifold and the second manifold through one or more flat microchannel tubes of the array of flat microchannel tubes, so as to cause each of the one or more flat microchannel tubes to be a dead tube that does not convey refrigerant between the first manifold and the second manifold in operation, while permitting fluid communication between the first manifold and the second manifold through additional flat microchannel tubes of the array of flat microchannel tubes, wherein preventing fluid communication between the first manifold and the second manifold through the one or more flat microchannel tubes includes preventing fluid communication between the first manifold and the second manifold through the first outer flat microchannel tube and also preventing fluid communication between the first manifold and the second manifold through an inner flat microchannel tube that is closest to the first outer flat microchannel tube.   
     
     
         26 . The method of  claim 25 , comprising brazing the array of flat microchannel tubes to the first and second manifolds, wherein brazing the array of flat microchannel tubes includes brazing the additional flat microchannel tubes to the first and second manifolds but does not include brazing the one or more flat microchannel tubes to the first and second manifolds. 
     
     
         27 . The method of  claim 25 , wherein preventing fluid communication between the first manifold and the second manifold through the one or more flat microchannel tubes includes bending ends of the one or more flat microchannel tubes such that the one or more flat microchannel tubes do not meet the first and second manifolds. 
     
     
         28 . The method of  claim 25 , wherein preventing fluid communication between the first manifold and the second manifold through the one or more flat microchannel tubes includes crimping an end of at least one flat microchannel tube of the one or more flat microchannel tubes to block flow through the at least one flat microchannel tube.