JP2009222360A - Heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat exchanger suitable for a refrigerant circuit using a single refrigerant composed of a refrigerant whose molecular formula is expressed by C<SB>3</SB>H<SB>m</SB>F<SB>n</SB>(m=1-5, n=1-5, and m+n=6) and having one double bond in the molecular structure, or a mixed refrigerant including the single refrigerant. <P>SOLUTION: In the heat exchanger 10, a relation between a distance S between centers of vertically adjacent heat transfer tubes and an outer diameter D of the heat transfer tube is expressed as 2.5<S/D<3.5. A relation between length L of a refrigerant route and the outer diameter D of the heat transfer tube is expressed as 0.28×D<SP>1.17</SP><L<1.10×D<SP>1.17</SP>. An outdoor heat exchanger 4 and an indoor heat exchanger 6 are designed based on the relational expressions. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heat exchanger, and more particularly to a heat exchanger suitable for a refrigerant circuit using a low-pressure refrigerant.

  From the viewpoint of protecting the global environment, the refrigerant used in the refrigerant circuit of the air conditioner is required to have a low global warming potential and not contribute to the destruction of the ozone layer. It has been developed (see, for example, Patent Document 1).

The refrigerant (C ₃ H _m F _n ) disclosed in Patent Document 1 has characteristics that a theoretical COP is relatively high and a global warming potential is low. However, since this refrigerant has a relatively high boiling point and is a so-called low-pressure refrigerant, there is a possibility that the input of the compressor is increased due to the pressure loss in the heat exchanger and the operation efficiency is lowered.
JP-A-4-110388

An object of the present invention is that the molecular formula is represented by C ₃ H _m F _n (where m = 1 to 5, n = 1 to 5, and m + n = 6) and has one double bond in the molecular structure. An object of the present invention is to provide a heat exchanger suitable for a refrigerant circuit using a single refrigerant composed of a refrigerant or a mixed refrigerant containing the single refrigerant.

The heat exchanger according to the first invention has a molecular formula represented by C ₃ H _m F _n (where m = 1 to 5, n = 1 to 5, and m + n = 6) and has a double bond in the molecular structure. A heat exchanger for a refrigerant circuit that uses a single refrigerant composed of one organic compound or a mixed refrigerant containing the single refrigerant, and includes a plurality of heat transfer tubes and a plurality of plate-like fins. The heat transfer tube forms one or a plurality of refrigerant paths through which the refrigerant flows. The plate-like fins are arranged so as to be stacked at a predetermined interval, and a plurality of heat transfer tubes penetrate substantially vertically. The relationship between the center-to-center distance S between the heat transfer tubes adjacent in the vertical direction and the outer diameter D of the heat transfer tube is 2.5 <S / D <3.5, and the length L of the refrigerant path and the outside of the heat transfer tube The relationship with the diameter D is 0.28 × D ^1.17 <L <1.10 × D ^1.17 .

  Since the refrigerant is a low-pressure refrigerant, it is susceptible to pressure loss in the heat transfer tube. However, in this heat exchanger, the refrigerant path length L, the outer diameter D of the heat transfer tube, and the center distance S of the heat transfer tube. Is applied to the above relational expression, the influence of the pressure loss of the refrigerant in the heat transfer tube can be minimized.

  A heat exchanger according to a second invention is the heat exchanger according to the first invention, wherein the refrigerant is a single refrigerant consisting of 2,3,3,3-tetrafluoro-1-propene or the single refrigerant. It is a mixed refrigerant containing.

  Since the single refrigerant composed of 2,3,3,3-tetrafluoro-1-propene or the mixed refrigerant containing the single refrigerant is a low-pressure refrigerant, it is susceptible to the pressure loss in the heat transfer tube, In this heat exchanger, the relationship between the refrigerant path length L, the outer diameter D of the heat transfer tube, and the center-to-center distance S of the heat transfer tube is applied to the above relational expression, so that the pressure loss of the refrigerant in the heat transfer tube Can be minimized.

  A heat exchanger according to a third invention is the heat exchanger according to the first invention, wherein the refrigerant is a mixed refrigerant containing 2,3,3,3-tetrafluoro-1-propene and difluoromethane.

  Since the mixed refrigerant containing 2,3,3,3-tetrafluoro-1-propene and difluoromethane is a low-pressure refrigerant, it is easily affected by pressure loss in the heat transfer tube. In this heat exchanger, The relationship between the refrigerant path length L, the heat transfer tube outer diameter D and the heat transfer tube center-to-center distance S is applied to the above relational expression, thereby minimizing the effect of refrigerant pressure loss in the heat transfer tube. Can be suppressed.

A heat exchanger according to a fourth aspect is the heat exchanger according to the first aspect, wherein the refrigerant is a mixed refrigerant containing 2,3,3,3-tetrafluoro-1-propene and pentafluoroethane. .
Since the mixed refrigerant containing 2,3,3,3-tetrafluoro-1-propene and pentafluoroethane is a low-pressure refrigerant, it is easily affected by pressure loss in the heat transfer tube. In this heat exchanger, The relationship between the refrigerant path length L, the heat transfer tube outer diameter D, and the heat transfer tube center-to-center distance S is applied to the above relational expression, thereby minimizing the effect of refrigerant pressure loss in the heat transfer tube. Can be suppressed.

  In the heat exchanger according to any one of the first invention, the second invention, the third invention, and the fourth invention, the relationship between the refrigerant path length L, the outer diameter D of the heat transfer tube, and the center-to-center distance S of the heat transfer tube. Is applied to the above relational expression, the influence of the pressure loss of the refrigerant in the heat transfer tube can be minimized.

<Refrigerant circuit>
FIG. 1 is a refrigerant circuit of an air conditioner. The air conditioner 1 has a refrigeration circuit in which a compressor 2, a four-way switching valve 3, an outdoor heat exchanger 4, an expansion valve 5, and an indoor heat exchanger 6 are connected by a refrigerant pipe. In FIG. 1, solid and broken arrows indicate the flow direction of the refrigerant, and the air conditioner 1 can switch between the heating operation and the cooling operation by switching the flow direction of the refrigerant with the four-way switching valve 3. . During the cooling operation, the outdoor heat exchanger 4 serves as a condenser, and the indoor heat exchanger 6 serves as an evaporator. In the heating operation, the outdoor heat exchanger 4 serves as an evaporator and the indoor heat exchanger 6 serves as a condenser.

The refrigerant circuit is filled with a mixed refrigerant composed of two types of organic compounds, HFO-1234yf (2,3,3,3-tetrafluoro-1-propene) and HFC-32 (difluoromethane). The refrigerant used in this embodiment is a mixed refrigerant composed of 78.2% by mass of HFO-1234yf and 21.8% by mass of HFC-32. The chemical formula of HFO-1234yf is represented by CF ₃ CFCH ₂ , and the chemical formula of HFC-32 is represented by CH ₂ F ₂ .

<Structure of heat exchanger>
FIG. 2 is a front view of the heat exchanger according to the embodiment of the present invention. In FIG. 2, a heat exchanger 10 is a cross fin type heat exchanger, and is a basic model of the outdoor heat exchanger 4 and the indoor heat exchanger 6 shown in FIG. The heat exchanger 10 includes fins 11 and heat transfer tubes 12. The fin 11 is a thin aluminum flat plate, and a plurality of through holes are formed in one fin 11. The heat transfer tube 12 includes a straight tube 12a that is inserted into the through hole of the fin 11, and a first U-shaped tube 12b and a second U-shaped tube 12c that connect ends of adjacent straight tubes 12a. The straight pipe 12a and the first U-shaped pipe 12b are integrally formed, and the second U-shaped pipe 12c has an end portion of the straight pipe 12a by welding or the like after the straight pipe 12a is inserted into the through hole of the fin 11. Connected to

(Relationship between tube outer diameter and center distance of heat transfer tube and heat exchanger performance)
FIG. 3 is a cross-sectional view of the heat exchanger when cut along line AA in FIG. 2. In FIG. 3, the pipe outer diameter of the straight pipe 12 a is D, and the distance between the centers of the heat transfer pipes 12 adjacent in the vertical direction is S. In general, the smaller the center-to-center distance S, the better the fin efficiency, but the ventilation resistance increases. Conversely, as the center-to-center distance S increases, the fin efficiency decreases, but the ventilation resistance also decreases. The fin efficiency is a ratio between the actual heat radiation amount radiated from the entire heat transfer surface of the fin and the heat radiation amount radiated when it is assumed that the total heat transfer surface of the fin is equal to the temperature of the refrigerant. .

  In addition, when the center-to-center distance S is constant, the fin efficiency increases as the pipe outer diameter D increases, but the ventilation resistance increases. Conversely, the smaller the pipe outer diameter D, the lower the fin efficiency, but the lower the ventilation resistance. That is, there is an optimum condition for improving the heat exchanger performance between the pipe outer diameter D and the center-to-center distance S.

  FIG. 4 is a graph showing the relationship between S / D and heat exchanger performance when the fan power is constant and D = 7 mm. In FIG. 4, the heat exchanger performance shows a high value in a range of 2.5 <S / D <3.5, and outside the range, the heat exchanger performance is degraded. That is, FIG. 4 shows that the relationship between the outer diameter D and the center-to-center distance S is 2 in the outdoor heat exchanger 4 and the indoor heat exchanger 6 of the refrigerant circuit using the mixed refrigerant of HFO-1234yf and HFC-32. .5 <S / D <3.5 suggests that optimum heat exchanger performance can be obtained.

(Relationship between refrigerant path length of heat exchanger and heat exchanger performance)
FIG. 5A is a conceptual diagram of the heat exchanger when the refrigerant path of the heat exchanger in FIG. 2 is one, and FIG. 5B is the case where the refrigerant path of the heat exchanger in FIG. 2 is two. It is a conceptual diagram of this heat exchanger, (c) is a conceptual diagram of a heat exchanger when the refrigerant path of the heat exchanger of FIG. 2 is branched into two from the middle.

  In FIG. 5 (a), the heat exchanger 10 has one refrigerant path, and is therefore called a one-pass heat exchanger 101. If the heat exchanger 10 has six heat transfer tubes 12 and the length of one heat transfer tube 12 is H, the refrigerant path length of the one-pass heat exchanger 101 is about 6H.

  In FIG. 5B, the heat exchanger 10 is called a two-pass heat exchanger 102 because two refrigerant paths are formed by the flow divider 90. The refrigerant path length of the two-pass heat exchanger 102 corresponds to half of the one-pass heat exchanger 101, about 3H.

  In FIG. 5C, the heat exchanger 10 is referred to as a 1-2 pass heat exchanger 103 because one refrigerant path is branched into two refrigerant paths through the flow divider 90 from the middle. Since the 1-2 pass heat exchanger 103 has a common refrigerant path and an independent refrigerant path, the refrigerant path length cannot be simply calculated. Therefore, the actual pressure loss of the 1-2 pass heat exchanger 103 is obtained, and if it is one refrigerant path, the length of the refrigerant path corresponding to the pressure loss of the refrigerant path is obtained and the value is obtained. Is the refrigerant path length.

  FIG. 6 is a graph showing the relationship between the refrigerant path length and the pressure loss. For example, when the pressure loss of the refrigerant in the 1-2 pass heat exchanger 103 in FIG. 5C is p, the refrigerant path length is 3.6H from the graph. In this way, the one-pass heat exchanger 101, the two-pass heat exchanger 102, and the 1-2-pass heat exchanger 103 having different refrigerant path lengths can be made from one basic heat exchanger 10. In other words, the refrigerant path length can be set by changing the quantity of refrigerant paths.

  Next, the relationship between the refrigerant path length and the heat exchanger performance will be described. Incidentally, the heat exchanger performance Q is expressed by the equation Q = KA × dT using the heat reflux rate K, the heat transfer area A, and the temperature difference dT between air and the refrigerant. The recirculation rate K is the reciprocal of the combined resistance of the air-side thermal resistance and the refrigerant-side thermal resistance. The combined resistance 1 / K is expressed by the equation 1 / K = 1 / ha + R / hr using the air-side heat transfer coefficient ha, the refrigerant-side heat transfer coefficient hr, and the internal / external heat transfer area ratio R.

  When the number of refrigerant paths is reduced and the refrigerant path length is increased, the amount of refrigerant flowing through one refrigerant path is increased and the refrigerant side heat transfer coefficient hr is improved. Since the evaporation temperature increases, the temperature difference dT between the air and the refrigerant decreases, and the heat exchanger performance Q decreases.

  On the other hand, when the number of refrigerant paths is increased to shorten the refrigerant path length, the pressure loss is reduced, the evaporation temperature at the heat exchanger inlet is lowered, and the temperature difference dT between the air and the refrigerant is increased. Since the amount of refrigerant flowing through one refrigerant path is reduced, the refrigerant side heat transfer coefficient hr is lowered, and the heat exchanger performance Q is lowered.

  That is, the outdoor heat exchanger 4 and the indoor heat exchanger 6 of the refrigerant circuit using the mixed refrigerant of HFO-1234yf and HFC-32 are the outdoor heat exchanger and the indoor heat corresponding to the conventional refrigerant (for example, 410A refrigerant). In order to achieve optimum heat exchanger performance, it is necessary to design after clarifying the relationship between the heat transfer tube outer diameter D and the refrigerant path length L.

  FIG. 7 is a graph showing the relationship between the refrigerant path length when D = 7 mm, the refrigerant-side heat transfer coefficient and the pressure loss, and FIG. 8 shows the refrigerant path length and heat when D = 7 mm. It is a graph which shows exchanger performance. As shown in FIG. 7, as the refrigerant path length becomes shorter, the pressure loss decreases, but the refrigerant-side heat transfer coefficient also decreases. As a result, as shown in FIG. 8, the heat exchanger performance is also lowered due to the decrease in the refrigerant side heat transfer coefficient. On the other hand, when the refrigerant path length is increased, the heat exchanger performance once reaches a peak and then decreases. That is, FIG. 8 suggests that there is a refrigerant path length suitable for the heat transfer tube outer diameter.

FIG. 9 is a graph plotting the refrigerant path length L against the heat transfer tube outer diameter D. FIG. In FIG. 9, square black dots indicate the optimum refrigerant path length with respect to the outer diameter of the heat transfer tube, and the lower limit value of the refrigerant path length with respect to the outer diameter of the heat transfer tube is on a straight line y = 0.28 × ^1.17 . The upper limit is on a straight line y = 1.10 × ^1.17 . That is, in the outdoor heat exchanger 4 and the indoor heat exchanger 6 of the refrigerant circuit using the mixed refrigerant of HFO-1234yf and HFC-32, the refrigerant path length L is 0.28 × D ^1.17 <L <1. It is suggested that optimal heat exchanger performance can be obtained by setting the range of 10 × D ^1.17 .

<Refrigerant used in refrigerant circuit>
(Single refrigerant)
In the said embodiment, although the mixed refrigerant | coolant which consists of two types of organic compounds of HFO-1234yf and HFC-32 is used as a refrigerant | coolant, it is not limited to it. For example, FIG. 10 is a component table of the refrigerant used in the refrigerant circuit including the heat exchanger according to the present embodiment, and the molecular formula is C ₃ H _m F _n (where m = 1), such as HFO-1234yf. ˜5, n = 1 to 5 and m + n = 6), and a single refrigerant composed of an organic compound having one double bond in the molecular structure may be used.

Specifically, HFO-1225ye (1,2,3,3,3-pentafluoro-1-propene, chemical formula: CF ₃ —CF═CHF), HFO-1234ze (1,3) shown in the upper part of FIG. , 3,3-tetrafluoro-1-propene, chemical formula: CF ₃ —CH═CHF), HFO-1234ye (1,2,3,3-tetrafluoro-1-propene, chemical formula: CHF ₂ —CF═CHF) , HFO-1243zf (3,3,3-trifluoro-1-propene, chemical formula: CF ₃ —CH═CH ₂ ), 1,2,2-trifluoro-1-propene, chemical formula: CH ₃ —CF═CF ₂ ), 2-fluoro-1-propene, (chemical formula: CH ₃ —CF═CH ₂ ) and the like. For convenience of explanation, these single refrigerants are classified as basic refrigerants.

(Mixed refrigerant)
Moreover, you may use the mixed refrigerant | coolant which consists of any one of the said basic refrigerant | coolants and any one of the 2nd component shown in FIG. For example, it is a mixed refrigerant with 22% by mass of HFC-32. Furthermore, the ratio of HFC-32 may be 6% by mass or more and 30% by mass or less, preferably 13% by mass or more and 23% by mass or less, and more preferably 21% by mass or more and 23% by mass or less. If it is.

Further, it may be a mixed refrigerant of any one of the above basic refrigerants and 10% by mass or more of HFC-125 (pentafluoroethane, CF ₃ —CHF ₂ ), and the ratio of HFC-125 is 10% by mass or more. If it is 20 mass% or less, it is preferable.

Further, any one of the above basic refrigerants, HFC-134 (1,1,2,2-tetrafluoroethane, CHF ₂ -CHF ₂ ), HFC-134a (1,1,1,2-tetrafluoroethane, _{CH 2 F-CF 3),} HFC-143a (1,1,1- _{trifluoroethane, CH 3 CF 3), HFC} -152a (1,1- _{difluoroethane, CHF 2 -CH 3), HFC} -161 ( fluoro _{ethane, CH 3 -CH 2 F),} HFC-227ea (1,1,1,2,3,3,3- _{heptafluoropropane, CF 3 -CHF-CF 3)} , HFC-236ea (1,1,1 , 2,3,3-hexafluoropropane, CF ₃ —CHF—CHF ₂ ), HFC-236fa (1,1,1,3,3,3-hexafluoroethane, CF ₃ —CH ₂ —CF ₃ ), And HFC 365mfc _{(1,1,1,3,3-pentafluorobutane, CF 3 -CH 2 CF 2 -CH} 3) of may be any one of the mixed refrigerant.

  The mixed refrigerant is a mixed refrigerant of any one of the basic refrigerants and an HFC-based refrigerant, but is not limited thereto, and any one of the basic refrigerants and a hydrocarbon-based refrigerant. A mixed refrigerant may be used.

Specifically, any one of the above basic refrigerants, methane (CH ₄ ), ethane (CH ₃ —CH ₃ ), propane (CH ₃ —CH ₂ —CH ₃ ), propene (CH ₃ —CH═CH _2). ), Butane (CH ₃ —CH ₂ —CH ₂ —CH ₃ ), isobutane (CH ₃ —CH (CH ₃ ) —CH ₃ ), pentane (CH ₃ —CH ₂ —CH ₂ —CH ₂ —CH ₃ ), A mixed refrigerant with any one of 2-methylbutane (CH ₃ —CH (CH ₃ ) —CH ₂ —CH ₃ ) and cyclopentane (cyclo-C ₅ H ₁₀ ) may be used.

In addition, any one of the above basic refrigerants, dimethyl ether (CH ₃ —O—CH ₃ ), bis-trifluoromethyl sulfide (CF ₃ —S—CF ₃ ), carbon dioxide (CO ₂ ), and helium (He) Or a mixed refrigerant with any one of the above.

  Moreover, in the said embodiment, although the mixed refrigerant | coolant which consists of two types of refrigerant | coolants of HFO-1234yf and HFC-32 is used as a refrigerant | coolant, any one of the said basic refrigerant | coolants and any two of said 2nd components are used. A mixed refrigerant consisting of one may be used. For example, a mixed refrigerant composed of 52% by mass of HFO-1234yf, 23% by mass of HFC-32, and 25% by mass of HFC-125 is preferable.

<Features>
The heat exchanger 10 is an organic compound having a molecular formula of C ₃ H _m F _n (where m = 1 to 5, n = 1 to 5, and m + n = 6) and having one double bond in the molecular structure. It is used as a heat exchanger of a refrigerant circuit using a single refrigerant composed of a compound or a mixed refrigerant containing the single refrigerant. The heat exchanger 10 includes a plurality of heat transfer tubes 12 and a plurality of plate-like fins 11. The heat transfer tube 12 forms one or a plurality of refrigerant paths through which the refrigerant flows. The plate-like fins 11 are arranged substantially parallel to the air flow direction, and a plurality of heat transfer tubes penetrates substantially vertically. The relationship between the center-to-center distance S between the heat transfer tubes adjacent in the vertical direction and the outer diameter D of the heat transfer tube is 2.5 <S / D <3.5, and the length L of the refrigerant path and the outside of the heat transfer tube The relationship with the diameter D is 0.28 × D ^1.17 <L <1.10 × D ^1.17 . As a result, the influence of the pressure loss of the refrigerant in the heat transfer tube is minimized. The specific refrigerant used is a single refrigerant composed of 2,3,3,3-tetrafluoro-1-propene, a mixed refrigerant containing the single refrigerant, or 2,3,3,3-tetra It is a mixed refrigerant containing fluoro-1-propene and difluoromethane, or a mixed refrigerant containing 2,3,3,3-tetrafluoro-1-propene and pentafluoroethane.

  As described above, the present invention is useful for a heat exchanger of a refrigerant circuit that uses a low-pressure refrigerant.

Air conditioner refrigerant circuit. The front view of the heat exchanger which concerns on embodiment of this invention. Sectional drawing of a heat exchanger when cut | disconnecting by the AA line of FIG. The graph which shows the relationship between S / D and a heat exchanger performance when fan power is constant and D = 7mm. (A) The conceptual diagram of a heat exchanger when the refrigerant path of the heat exchanger of FIG. 2 is made into one. (B) The conceptual diagram of a heat exchanger when the refrigerant path of the heat exchanger of FIG. 2 is two. (C) The conceptual diagram of a heat exchanger when the refrigerant path of the heat exchanger of FIG. 2 is two from the middle. The graph which shows the relationship between refrigerant path length and pressure loss. The graph which shows the relationship between refrigerant | coolant path | route length, a refrigerant | coolant side heat transfer rate, and a pressure loss when D = 7mm. The graph which shows the refrigerant | coolant path length and heat exchanger performance in case D = 7mm. The graph which plotted the refrigerant | coolant path | route length L with respect to the heat exchanger tube outer diameter D. FIG. The refrigerant | coolant component table used for the refrigerant circuit containing the heat exchanger which concerns on this embodiment.

Explanation of symbols

4 Outdoor Heat Exchanger 6 Indoor Heat Exchanger 10 Heat Exchanger 11 Plate Fin 12 Heat Transfer Tube

Claims (4)

Single refrigerant comprising an organic compound having a molecular formula of C ₃ H _m F _n (where m = 1 to 5, n = 1 to 5, and m + n = 6) and having one double bond in the molecular structure Or a heat exchanger of a refrigerant circuit using a mixed refrigerant containing the single refrigerant,
A plurality of heat transfer tubes (12) forming one or more refrigerant paths for the refrigerant to circulate;
A plurality of plate-like fins (11) arranged so as to be stacked at a predetermined interval, and through which the plurality of heat transfer tubes (12) penetrate substantially vertically;
With
The relationship between the center-to-center distance S between the heat transfer tubes (12) adjacent in the vertical direction and the outer diameter D of the heat transfer tubes (12) is as follows.
2.5 <S / D <3.5,
And
The relationship between the length L of the refrigerant path and the outer diameter D of the heat transfer tube (12) is
0.28 × D ^1.17 <L <1.10 × D ^1.17 ,
Is,
Heat exchanger (4, 6, 10). The refrigerant is a single refrigerant composed of 2,3,3,3-tetrafluoro-1-propene or a mixed refrigerant containing the single refrigerant.
The heat exchanger (4, 6, 10) according to claim 1. The refrigerant is a mixed refrigerant containing 2,3,3,3-tetrafluoro-1-propene and difluoromethane.
The heat exchanger (4, 6, 10) according to claim 1. The refrigerant is a mixed refrigerant containing 2,3,3,3-tetrafluoro-1-propene and pentafluoroethane.
The heat exchanger (4, 6, 10) according to claim 1.

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