Parallel-flow evaporators with liquid trap for providing better flow distribution

Abstract

A parallel-flow evaporator has a liquid trap for regulating velocity of refrigerant delivered to an evaporator from an expansion device. In its simplest configuration, the liquid trap is a u-shaped pipe positioned vertically and connected to an inlet manifold of the evaporator. By providing a liquid trap, a small amount of liquid refrigerant separates from the vapor phase at certain conditions. This separated liquid will tend to collect in the trap, and reduce a flow cross-sectional area of the line leading to the inlet manifold of the evaporator. As this cross-sectional area decreases, the velocity of the refrigerant passing through the line will increase. In this sense, as a small amount of liquid phase separates out, it will ensure that the velocity of the remaining refrigerant will increase such that further separation will be significantly reduced or entirely avoided. As a result, homogeneous refrigerant flow is provided to the evaporator, resulting in its performance enhancement and system reliability improvement.

1 . A refrigerant system comprising:
 a compressor delivering a compressed refrigerant to a condenser, refrigerant passing from said condenser to an expansion device, and from said expansion device to an evaporator, said evaporator comprising an inlet manifold, outlet manifold, a plurality of channels receiving refrigerant from said inlet manifold and delivering it to said outlet manifold, and fins disposed between said channels; and   a line connecting said expansion device and said evaporator, said line being provided with a liquid trap to collect liquid separated out of a vapor refrigerant passing from said expansion device to said evaporator.   
   
   
       2 . The refrigerant system as set forth in  claim 1 , wherein said liquid trap extends vertically beneath said inlet manifold. 
   
   
       3 . The refrigerant system as set forth in  claim 1 , wherein said liquid trap is generally provided by a u-shape downwardly extending portion of said line. 
   
   
       4 . The refrigerant system as set forth in  claim 1 , wherein said liquid trap is positioned within 5 inches from said inlet manifold. 
   
   
       5 . The refrigerant system as set forth in  claim 1 , wherein said refrigerant system is also provided with an economizer circuit, said economizer circuit having an economizer heat exchanger, and said economizer heat exchanger being provided with a tap line connecting a main flow line through an economizer expansion device, and then into said economizer heat exchanger, said tap line being returned to an intermediate compression point in said compressor downstream of said economizer heat exchanger, and a liquid trap to collect liquid separated out of a vapor refrigerant passing from said economizer expansion device to said economizer heat exchanger. 
   
   
       6 . The refrigerant system as set forth in  claim 1 , wherein said liquid trap includes a plurality of serially spaced u-shaped liquid trap portions. 
   
   
       7 . A method of operating a refrigerant system comprising the steps of:
 providing an evaporator having a plurality of tubes receiving refrigerant from an inlet manifold, and delivering said refrigerant to an outlet manifold, and from said outlet manifold to compressor, said compressor delivering the refrigerant to a condenser, and said refrigerant passing from said condenser to an expansion device, and then back to said evaporator, and providing a fluid line connecting said expansion device to said evaporator, said fluid line being provided with a liquid trap to capture liquid that has separated from a vapor refrigerant; and   passing refrigerant through said refrigerant system and such that liquid trap self-regulates a velocity of refrigerant as the liquid separates from the vapor refrigerant to deliver refrigerant into said inlet manifold in a predominantly homogeneous state.   
   
   
       8 . The method as set forth in  claim 7 , wherein the refrigerant system further being provided with an economizer circuit, said economizer circuit including an economizer heat exchanger, and tapping refrigerant and passing the tapped refrigerant through an economizer expansion device into said economizer heat exchanger, and a liquid trap provided to capture liquid that has separated from a vapor passing from said economizer expansion device into said economizer heat exchanger, and further including the steps of passing refrigerant through said economizer expansion device, and to said economizer heat exchanger, such that said liquid trap self-regulates a velocity of refrigerant as the liquid separates from the vapor refrigerant to deliver refrigerant into said economizer heat exchanger in a predominantly homogeneously state. 
   
   
       9 . A heat exchanger and fluid line system comprising:
 a fluid line leading into an inlet manifold;   a liquid trap on said fluid line; and   a heat exchanger having a plurality of channels receiving a fluid from said inlet manifold.   
   
   
       10 . The heat exchanger and fluid line system as set forth in  claim 9 , wherein said heat exchanger is a refrigerant system evaporator. 
   
   
       11 . The heat exchanger and fluid line system as set forth in  claim 9 , wherein said heat exchanger is a refrigerant system economizer heat exchanger. 
   
   
       12 . The heat exchanger and fluid line system as set forth in  claim 9 , wherein said liquid trap extends vertically beneath said inlet manifold. 
   
   
       13 . The heat exchanger and fluid line system as set forth in  claim 9 , wherein said liquid trap is generally provided by a u-shape downwardly extending portion of said line. 
   
   
       14 . The heat exchanger and fluid line system as set forth in  claim 9 , wherein said liquid trap is positioned within 5 inches from said inlet manifold. 
   
   
       15 . The heat exchanger and fluid line system as set forth in  claim 9 , wherein said liquid trap is provided by a plurality of serially spaced u-shaped structures.