Header, heat exchanger, and air-conditioning apparatus

Abstract

A header includes a plurality of branch tubes and a header manifold. If refrigerant flowing into the header manifold forms a pattern of annular flow or churn flow, tips of the branch tubes inserted into the header manifold pass through a liquid-phase portion having a thickness δ [m] and reach a gas-phase portion. The thickness δ [m] of the liquid-phase portion is defined as δ=G×(1−x)×D/(4ρL×ULS), where G is a flow speed [kg/(m2s)] of the refrigerant, x is a quality of the refrigerant, D is an inside diameter [m] of the header manifold, ρL is a liquid density [kg/m3] of the refrigerant, ULS is a reference apparent liquid speed [m/s] that is a maximum value within a range of variation in an apparent gas speed of the refrigerant flowing into a flow space of the header manifold. The reference apparent liquid speed ULS [m/s] is defined as G(1−x)/ρL.

1 : A header comprising:
 a plurality of branch tubes; and   a header manifold having a flow space that communicates with the plurality of branch tubes and in which gas-liquid two-phase refrigerant flows upward and is discharged into the plurality of branch tubes,   wherein if the refrigerant flowing into the header manifold forms a pattern of annular flow or churn flow, tips of the branch tubes inserted into the header manifold are configured to pass through a liquid-phase portion having a thickness δ [m] and reach a gas-phase portion,   wherein the thickness δ [m] of the liquid-phase portion is defined as δ=G×(1−x)×D/(4ρ L ×U LS ), where G is a flow speed [kg/(m 2 s)] of the refrigerant, x is a quality of the refrigerant, D is an inside diameter [m] of the header manifold, ρ L  is a liquid density [kg/m 3 ] of the refrigerant, U LS  is a reference apparent liquid speed [m/s] that is a maximum value within a range of variation in an apparent gas speed of the refrigerant flowing into the flow space of the header manifold, the reference apparent liquid speed U LS  [m/s] being defined as G(1−x)/ρ L .   
     
     
         2 : The header of  claim 1 ,
 wherein a reference apparent gas speed U GS  [m/s] that is a maximum value within a range of variation in an apparent gas speed of the refrigerant flowing into the flow space of the header manifold satisfies a condition U GS ≥α×L×(g×D) 0.5 /(40.6×D)−0.22α×(g×D) 0.5 , where α is a void fraction of the refrigerant, L is an entrance length [m], g is a gravitational acceleration [m/s 2 ], and D is the inside diameter [m] of the header manifold, and   wherein the void fraction α of the refrigerant is defined as x/[x+(ρ G /ρ L )×(1−x)], where x is the quality of the refrigerant, ρ G  is a gas density [kg/m 3 ] of the refrigerant, and ρ L  is the liquid density [kg/m 3 ] of the refrigerant.   
     
     
         3 : The header of  claim 2 , wherein the reference apparent gas speed U GS  [m/s] that is the maximum value within the range of variation in the apparent gas speed of the refrigerant flowing into the flow space of the header manifold satisfies a condition U GS ≥3.1/(ρ G   0.5 )×[σ×g×(ρ L −ρ G )] 0.25 , where ρ G  is the gas density [kg/m 3 ] of the refrigerant, σ is a surface tension [N/m] of the refrigerant, g is the gravitational acceleration [m/s 2 ], and ρ L  is the liquid density [kg/m 3 ] of the refrigerant. 
     
     
         4 : A header comprising:
 a plurality of branch tubes; and   a header manifold having a flow space that communicates with the plurality of branch tubes and in which gas-liquid two-phase refrigerant flows upward and is discharged into the plurality of branch tubes,   wherein, when a center position of the flow space of the header manifold in a horizontal plane is defined as 0% and a position of a wall surface of the flow space of the header manifold in the horizontal plane is defined as 100% on either side, a tip of each of the branch tubes inserted into the header manifold is positioned in an area within 50% on either side,   wherein a reference apparent gas speed U GS  [m/s] that is a maximum value within a range of variation in an apparent gas speed of the refrigerant flowing into the flow space of the header manifold satisfies a condition U GS ≥α×L×(g×D) 0.5 /(40.6×D)−0.22α×(g×D) 0.5 , where α is a void fraction of the refrigerant, L is an entrance length [m], g is a gravitational acceleration [m/s 2 ], and D is an inside diameter [m] of the header manifold, and   wherein the void fraction a of the refrigerant is defined as x/[x+(ρ G /ρ L )×(1−x)], where x is a quality of the refrigerant, ρ G  is a gas density [kg/m 3 ] of the refrigerant, and ρ L  is a liquid density [kg/m 3 ] of the refrigerant.   
     
     
         5 : The header of  claim 4 , wherein the reference apparent gas speed U GS  [m/s] that is the maximum value within the range of variation in the apparent gas speed of the refrigerant flowing into the flow space of the header manifold satisfies a condition U GS ≥3.1/(ρ G   0.5 )×[σ×g×(ρ L −ρ G )] 0.25 , where ρ G  is the gas density [kg/m 3 ] of the refrigerant, σ is a surface tension [N/m] of the refrigerant, g is the gravitational acceleration [m/s 2 ], and ρ L  is the liquid density [kg/m 3 ] of the refrigerant. 
     
     
         6 : The header of  claim 1 , wherein, when a center position of the flow space of the header manifold in a horizontal plane is defined as 0%; a position of a wall surface of the flow space of the header manifold in the horizontal plane is defined as 100% on either side; a direction of insertion of each of the plurality of branch tubes in the horizontal plane is defined as an X direction; and a width direction of each of the plurality of branch tubes that is orthogonal to the X direction in the horizontal plane is defined as a Y direction, tips of all of the plurality of branch tubes are positioned in an area within 50% on either side in the X direction; and center axes of all of the plurality of branch tubes are positioned in an area within 50% on either side in the Y direction. 
     
     
         7 : The header of  claim 6 , wherein the tips of all of the plurality of branch tubes are positioned in an area within 25% on either side in the X direction, and the center axes of all of the plurality of branch tubes are positioned in an area within 25% on either side in the Y direction. 
     
     
         8 : The header of  claim 7 , wherein the tips of all of the plurality of branch tubes are positioned at 0% in the X direction, and the center axes of all of the plurality of branch tubes are positioned at 0% in the Y direction. 
     
     
         9 : The header of  claim 1 , wherein, when a flow rate [kg/h] of the refrigerant is M R ; the quality of the refrigerant flowing into the header manifold in a rated heating operation is x; and an effective passage-section area [m 2 ] of the header manifold is A, the quality x of the refrigerant flowing into the header manifold satisfies a condition 0.05≤x≤0.30, and a parameter (M R ×x)/(31.6×A) concerning a thickness of a liquid film formed of the refrigerant falls within a range 0.004×10 6 ≤(M R ×x)/(31.6×A)≤0.120×10 6 . 
     
     
         10 : The header of  claim 9 , wherein, when the flow rate [kg/h] of the refrigerant is M R ; the quality of the refrigerant flowing into the header manifold in the rated heating operation is x; and the effective passage-section area [m 2 ] of the header manifold is A, the quality x of the refrigerant flowing into the header manifold satisfies the condition 0.05≤x≤0.30, and the parameter (M R ×x)/(31.6×A) concerning the thickness of the liquid film formed of the refrigerant falls within a range 0.010×10 6 ≤(M R ×x)/(31.6×A)≤0.120×10 6 . 
     
     
         11 : The header of  claim 1 , wherein, when the flow rate [kg/h] of the refrigerant is M R  and the quality of the refrigerant flowing into the header manifold in the rated heating operation is x, the quality x of the refrigerant flowing into the header manifold satisfies the condition 0.05≤x≤0.30, the inside diameter D [m] of the header manifold falls within a range 0.010≤D≤0.018, and a parameter (M R ×x)/31.6 concerning the thickness of the liquid film formed of the refrigerant falls within a range 0.427≤(M R ×x)/31.6≤5.700. 
     
     
         12 : The header of  claim 1 , wherein, when the quality of the refrigerant flowing into the header manifold in the rated heating operation is x and the effective passage-section area [m 2 ] of the header manifold is A, the quality x of the refrigerant flowing into the header manifold satisfies the condition 0.05≤x≤0.30, the inside diameter D [m] of the header manifold falls within the range 0.010≤D≤0.018, and a parameter x/(31.6×A) concerning the thickness of the liquid film formed of the refrigerant falls within a range 1.4×10≤x/(31.6×A)≤8.7×10. 
     
     
         13 : The header of  claim 1 ,
 wherein, when the quality of the refrigerant flowing into the header manifold in the rated heating operation is x, the quality x of the refrigerant flowing into the header manifold satisfies the condition 0.05≤x≤0.30, and the apparent gas speed U SG  [m/s] of the refrigerant flowing into the header manifold falls within a range 1≤U SG ≤10, and   wherein the apparent gas speed U SG  [m/s] is defined as U SG =(G×x)/ρ G , where G is the flow speed [kg/(m 2 s)] of the refrigerant flowing into the header manifold, x is the quality of the refrigerant, and ρ G  is the gas density [kg/(m 3 )] of the refrigerant; and the flow speed [kg/(m 2 s)] of the refrigerant is defined as G=M R /(3600×A), where M R  is the flow rate [kg/h] of the refrigerant flowing into the header manifold in the rated heating operation, and A is the effective passage-section area [m 2 ] of the header manifold.   
     
     
         14 : The header of  claim 1 , wherein the branch tubes are provided with tube-shape-converting joints each converting the tip of a corresponding one of the branch tubes inserted into the header manifold from a flat tubular shape for connection to a corresponding one of flat heat-transfer tubes included in a heat exchanger into a round tubular shape. 
     
     
         15 : The header of  claim 1 , wherein the branch tubes are each obtained by extending part of the heat-transfer tube included in the heat exchanger. 
     
     
         16 : The header of  claim 1 , wherein the plurality of branch tubes each have a flat tubular shape. 
     
     
         17 : The header of  claim 1 , wherein, when a pitch between adjacent ones of the plurality of branch tubes is Lp and a length of a stagnation area in an upper part of the header manifold is Lt, a relationship Lt≥2×Lp is established. 
     
     
         18 : The header of  claim 1 , wherein an uppermost one of the plurality of branch tubes is connected to an upper end of the header manifold from an upper side. 
     
     
         19 : The header of  claim 1 , wherein the refrigerant employed is R32, R410A, or CO 2 . 
     
     
         20 : The header of  claim 1 , wherein the refrigerant employed is a mixture of at least two or more kinds of refrigerant having different boiling point differences that are selected from olefin-based refrigerant, HFC refrigerant, hydrocarbon refrigerant, CO 2 , and DME. 
     
     
         21 : A heat exchanger comprising:
 a plurality of heat-transfer tubes arranged in such a manner as to project therefrom on both sides;   a first header connected to one end of each of the plurality of heat-transfer tubes;   a second header connected to an other end of each of the plurality of heat-transfer tubes; and   a plurality of fins joined to each of the plurality of heat-transfer tubes,   wherein the heat exchanger forms part of a refrigeration cycle circuit through which refrigerant circulates,   wherein the second header is the header of  claim 1 ,   wherein the header manifold of the second header has a flow space that communicates with each of the plurality of branch tubes connected to corresponding one of the plurality of heat-transfer tubes, and wherein when the heat exchanger serves as an evaporator, gas-liquid two-phase refrigerant flows upward in the flow space and is discharged into the plurality of branch tubes.   
     
     
         22 : The heat exchanger of  claim 21 , wherein the second header is divided into at least two pieces in a height direction, the two pieces being connected to each other on an upstream side in a direction in which the refrigerant flows into the heat exchanger in a heating operation. 
     
     
         23 : An air-conditioning apparatus comprising:
 a compressor, an indoor heat exchanger, an expansion device, and an outdoor heat exchanger that form a refrigeration cycle circuit through which refrigerant circulates,   wherein the outdoor heat exchanger is the heat exchanger of  claim 21 , and   wherein the air-conditioning apparatus includes a controller configured to control the compressor or the expansion device such that the quality x of the refrigerant flowing into the second header falls within the range 0.05≤x≤0.30 in the rated heating operation.   
     
     
         24 : An air-conditioning apparatus comprising:
 a compressor, an indoor heat exchanger, an expansion device, and an outdoor heat exchanger that form a refrigeration cycle circuit through which refrigerant circulates,   wherein the outdoor heat exchanger is the heat exchanger of  claim 21 , and   wherein the air-conditioning apparatus includes
 a first temperature sensor provided on a downstream side, in the heating operation, of the indoor heat exchanger; 
 a second temperature sensor provided on the indoor heat exchanger; and 
 a controller configured to calculate an outlet temperature difference of the indoor heat exchanger from a temperature detected by the first temperature sensor and a temperature detected by the second temperature sensor in the heating operation, and to control the compressor or the expansion device such that the quality x of the refrigerant flowing into the second header falls within the range 0.05≤x≤0.30 in the rated heating operation. 
   
     
     
         25 : An air-conditioning apparatus comprising:
 a compressor, an indoor heat exchanger, an expansion device, and an outdoor heat exchanger that form a refrigeration cycle circuit through which refrigerant circulates,   wherein the outdoor heat exchanger is the heat exchanger of  claim 21 , and   wherein the air-conditioning apparatus includes
 a gas-liquid separator provided between the outdoor heat exchanger and the expansion device; 
 a gas bypass pipe that allows gas refrigerant obtained through separation by the gas-liquid separator to flow directly to the compressor; 
 a gas-bypass regulating valve provided at the gas bypass pipe; and 
 a controller configured to control the gas-bypass regulating valve in accordance with operating conditions such that the quality x of the refrigerant flowing into the second header falls within the range 0.05≤x≤0.30. 
   
     
     
         26 : An air-conditioning apparatus comprising:
 a compressor, a four-way valve, an indoor heat exchanger, an expansion device, and an outdoor heat exchanger that form a refrigeration cycle circuit through which refrigerant circulates, the air-conditioning apparatus being capable of performing a heating operation and a cooling operation by switching a flow of the refrigerant at the four-way valve,   wherein the outdoor heat exchanger is the heat exchanger of  claim 21 , and   wherein the air-conditioning apparatus includes
 a gas-liquid separator provided between the outdoor heat exchanger and the expansion device; 
 a gas bypass pipe that allows gas refrigerant obtained through separation by the gas-liquid separator to flow directly to the compressor; 
 a gas-bypass regulating valve provided at the gas bypass pipe; 
 a header-preceding regulating valve provided at a downstream side, in the heating operation, of the gas-liquid separator; and 
 a controller configured to control the expansion device, the gas-bypass regulating valve, and the header-preceding regulating valve in the heating operation such that the quality x of the refrigerant flowing into the second header falls within the range 0.05≤x≤0.30, and to control the header-preceding regulating valve in the cooling operation such that the gas-liquid separator is used as a liquid storage. 
   
     
     
         27 : A header comprising:
 a plurality of branch tubes; and   a header manifold having a flow space that communicates with the plurality of branch tubes and in which gas-liquid two-phase refrigerant flows in from an inlet of the header manifold upward and is discharged into the plurality of branch tubes,   the header being for use in an operation mode, the operation mode including an operation condition in which the refrigerant flows in a flow pattern such that more gas-phase portion, than liquid-phase portion, of the gas-liquid two-phase refrigerant flowing to the header manifold is present around a center axis of the header manifold,   the header including an entrance portion in which the refrigerant flows upward, the entrance portion being provided between the inlet of the header manifold and a branch tube of the branch tubes closest to the inlet, the entrance portion having an entrance length L [m] satisfying a condition L≥5D, where D is the inside diameter [m] of the header manifold,   wherein, when a center position of the flow space of the header manifold in a horizontal plane is defined as 0% and a position of a wall surface of the flow space of the header manifold in the horizontal plane is defined as 100% on either side, a tip of each of the branch tubes inserted into the header manifold is positioned in an area within 50% on either side, and   tips of the branch tubes connected to a lower part of the header manifold are positioned at a part in which more gas-phase portion, than the liquid-phase portion, of the refrigerant is present.   
     
     
         28 : The header of  claim 27 , wherein, when a center position of the flow space of the header manifold in a horizontal plane is defined as 0%; a position of a wall surface of the flow space of the header manifold in the horizontal plane is defined as 100% on either side; a direction of insertion of each of the plurality of branch tubes in the horizontal plane is defined as an X direction; and a width direction of each of the plurality of branch tubes that is orthogonal to the X direction in the horizontal plane is defined as a Y direction, tips of all of the plurality of branch tubes are positioned in an area within 50% on either side in the X direction; and center axes of all of the plurality of branch tubes are positioned in an area within 50% on either side in the Y direction. 
     
     
         29 : The header of  claim 27 , wherein
 the inflow pipe is attached to the entrance portion such that the inflow pipe is inclined, and   a condition (L 2 +L 3 )≥6D is satisfied where L 2  is a combined length [m] of a portion of the entrance portion and a strait portion of the inflow pipe, and L 3  is a length [m] of the inclined portion of the inflow pipe.   
     
     
         30 : The header of  claim 27 ,
 wherein in the operation condition,   a reference apparent gas speed U GS  [m/s] that is a maximum value within a range of variation in an apparent gas speed of the refrigerant flowing into the flow space of the header manifold satisfies a condition U GS ≥α×L×(g×D) 0.5 /(40.6×D)−0.22α×(g×D) 0.5 , where α is a void fraction of the refrigerant, L is an entrance length [m], g is a gravitational acceleration [m/s 2 ], and D is the inside diameter [m] of the header manifold, and   wherein the void fraction a of the refrigerant is defined as x/[x+(ρ G /ρ L )×(1−x)], where x is the quality of the refrigerant, ρ G  is a gas density [kg/m 3 ] of the refrigerant, and ρ L  is the liquid density [kg/m 3 ] of the refrigerant.   
     
     
         31 : The header of  claim 27 , wherein in the operation condition,
 the reference apparent gas speed U GS  [m/s] that is the maximum value within the range of variation in the apparent gas speed of the refrigerant flowing into the flow space of the header manifold satisfies a condition U GS ≥3.1/(ρ G   0.5 )× [σ×g×(ρ L −ρ G )] 0.25 , where ρ G  is the gas density [kg/m 3 ] of the refrigerant, σ is a surface tension [N/m] of the refrigerant, g is the gravitational acceleration [m/s 2 ], and ρ L  is the liquid density [kg/m 3 ] of the refrigerant.   
     
     
         32 : The header of  claim 27 , wherein the branch tubes are provided with tube-shape-converting joints each converting the tip of a corresponding one of the branch tubes inserted into the header manifold from a flat tubular shape for connection to a corresponding one of flat heat-transfer tubes included in a heat exchanger into a round tubular shape. 
     
     
         33 : The header of  claim 27 , wherein the branch tubes are each obtained by extending part of the heat-transfer tube included in the heat exchanger. 
     
     
         34 : The header of  claim 27 , wherein an uppermost one of the plurality of branch tubes is connected to an upper end of the header manifold from an upper side. 
     
     
         35 : The header of  claim 27 , wherein the refrigerant employed is a mixture of at least two or more kinds of refrigerant having different boiling point differences that are selected from olefin-based refrigerant, HFC refrigerant, hydrocarbon refrigerant, CO 2 , and DME. 
     
     
         36 : An air-conditioning apparatus comprising a refrigerant circuit including a compressor, and indoor heat exchanger, and expansion device, an outdoor heat exchanger, in which refrigerant circulates, wherein
 the header of  claim 27  is provided at at least one of the indoor heat exchanger and the outdoor heat exchanger.   
     
     
         37 : The air-conditioning apparatus of  claim 36 , wherein
 at least one header connected to the outdoor heat exchanger of the refrigeration cycle circuit,   a gas-liquid separator provided at a refrigerant path between the heat outdoor heat exchanger and the expansion device, and   a gas-bypass regulating valve provided at a gas bypass pipe that allows gas refrigerant obtained through separation by the gas-liquid separator to flow directly to the compressor, wherein   the air-conditioning apparatus is configured to bypass a part of the refrigerant by the gas-bypass pipe under at least one condition in the heating operation to adjust the pattern of flow of the refrigerant.