JP2012017901A - Condensation performance evaluation method, and heat transfer pipe for condenser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct evaluation of a condensation performance of a heat transfer pipe where an effect of inundation is reflected in a single pipe.SOLUTION: A condensation performance evaluation method includes: a condensation step of condensing a refrigerant vapor on an outer surface of a sample pipe 40; an evaluation step of evaluating the condensation performance of the sample pipe 40 when the sample pipe 40 condensing the refrigerant vapor. In the condensation step, the refrigerant vapor is condensed by the sample pipe 40 while a liquid coolant 22, which is a liquified material of the refrigerant vapor, is dropped or sprayed to the sample pipe 40.

Description

  The present invention relates to a condensation performance evaluation method for evaluating the condensation performance of a heat transfer tube used for condensing refrigerant vapor, and a condenser heat transfer tube for condensing refrigerant vapor.

  In general, a turbo refrigerator, a screw refrigerator, or the like, which is an example of a heat exchanger, includes a condenser that condenses refrigerant vapor. The condenser incorporates a tubular heat transfer tube through which a cooling fluid flows, and is configured to condense the refrigerant vapor by bringing the refrigerant vapor into contact with the outer surface of the heat transfer tube.

  As heat transfer tubes used in the condenser, various heat transfer surface (tube outer surface) shapes have been proposed in order to achieve good heat transfer performance. As an example, as shown in FIG. 8, a raised portion 51 that is continuous in the circumferential direction (see the arrow in the figure) is formed on the heat transfer surface (outer surface of the tube), and the distal end portion of the raised portion 51 extends to the proximal end portion. Some of them are provided with valleys 52 (see, for example, Patent Document 1). In such a heat transfer tube, the outer surface of the tube is cooled below the saturation temperature by the cooling fluid flowing in the tube, whereby the refrigerant vapor contacting the outer surface of the tube is condensed on the outer surface of the tube and becomes liquid. At this time, on the outer surface of the tube, the condensed liquid film flows into the groove 53 or the valley 52 located between the raised portions 51 due to the action of the surface tension of the liquid or the action of gravity. Therefore, the liquid film does not stay in the peak portion 54 in the raised portion 51, and as a result, good heat transfer performance can be obtained.

  By the way, when actually configuring a heat exchanger, as shown in FIG. 9, for example, a large number of heat transfer tubes 61a, 61b,. It is common to arrange them in a honeycomb form. It is known that in the case of a configuration in which the refrigerant vapor is condensed using the heat transfer tube group 61 formed by such a large number of heat transfer tubes 61a, 61b, ..., heat transfer may be deteriorated due to indentation (for example, Patent Document 2). reference). In the indentation, the condensate is dripped from the upper heat transfer tube 61a in the gravity direction in the shell 60, and the portion of the heat transfer tube 61b in the lower shell in the gravitational direction in the shell 60 that is covered with the dripping liquid decreases. As a result, the refrigerant vapor condensing action in the lower heat transfer tube 61b in the gravity direction is hindered.

Japanese Patent Application Laid-Open No. 51-81072 Japanese Patent Laid-Open No. 07-71886

  About the heat exchanger tube used for a condenser, it is possible to employ | adopt the pipe | tube outer surface shape disclosed by the above-mentioned patent document 1. FIG. However, in recent years, there has been a strong demand for further improvement in heat transfer performance (that is, condensation performance) in a heat transfer tube for a condenser in order to improve the performance and size of the heat exchanger. This is because if the condensation performance of the heat transfer tube is improved, the amount of exchange heat in the heat exchanger can be increased, and a heat exchanger having the same amount of exchange heat can be manufactured in a smaller size.

In order to further improve the condensation performance in a heat transfer tube for a condenser, the heat transfer coefficient on the outer surface of the tube when the heat transfer tube actually condenses the refrigerant vapor is measured, and the heat transfer tube is based on the measurement result. It is necessary to review and evaluate the outer shape of the pipe according to the evaluation result after grasping and evaluating the condensation performance in the pipe. In other words, it is essential to evaluate the condensation performance of the heat transfer tube in order to find the outer shape of the tube that realizes further improvement in condensation performance.

  Conventionally, the condensation performance evaluation of a heat transfer tube is usually performed in a single tube state. This is because if the test is performed in the state of a tube group in which a large number of tubes are arranged, an evaluation (test) apparatus becomes large, and a lot of cost is required for that purpose.

  However, in the conventional condensation performance evaluation performed in the state of a single tube, the influence of the indentation disclosed in Patent Document 2 is not considered. In other words, since the influence of inundation is not considered, there is a flaw between the condensation performance evaluated in the state of a single tube and the condensation performance of each tube that makes up the tube group when an actual heat exchanger is configured. There is a risk that. Therefore, in the conventional single pipe evaluation, it is difficult to find the outer shape of the pipe that can suppress the deterioration of the condensation performance (heat transfer performance) due to the influence of the indentation.

  Therefore, the present invention provides a condensation performance evaluation method that makes it possible to perform condensation performance evaluation of a heat transfer tube in consideration of the influence of inversion without requiring a large-scale configuration and a lot of costs. It aims at providing the heat exchanger tube for condensers which can control condensation performance degradation by the influence of foundation.

  The first aspect of the present invention includes a condensation step of condensing refrigerant vapor on the outer surface of a test tube used as a heat transfer tube of a condenser, and heat transfer on the outer surface of the tube when the test tube condenses the refrigerant vapor. A condensing performance evaluation method having an evaluation step of evaluating the condensing performance of the test tube based on a rate, wherein the condensing step drops or spreads a liquid refrigerant which is a liquid material of the refrigerant vapor on the test tube. However, the condensation performance evaluation method is characterized in that the refrigerant vapor is condensed by the test tube.

  According to a second aspect of the present invention, in the condensation performance evaluation method according to the first aspect, the liquid refrigerant is dropped or sprayed onto the test tube in a single tube state.

  According to a third aspect of the present invention, in the condensation performance evaluation method according to the first aspect or the second aspect, the dropping amount or the spraying amount of the liquid refrigerant to the test tube is controlled to a desired amount.

  According to a fourth aspect of the present invention, there is provided a heat transfer tube for a condenser which is formed in a tubular shape and is configured to condense refrigerant vapor on the outer surface of the tube, and the tube outer surface is annular in the circumferential direction of the outer surface of the tube. Alternatively, a fin that is continuous in a spiral shape is formed by cutting, and the notch portion formed from the tip end portion to the base end portion of the fin has a continuous direction of the fin. And a formation height from the base end portion to the tip end portion of the fin is 0.8 to 1.1 mm.

  According to a fifth aspect of the present invention, in the heat transfer tube for a condenser according to the fourth aspect, the arrangement pitch of the fins adjacent to each other in the tube axis direction of the heat transfer tube for the condenser is 0.5 to 0.7 mm. It is characterized by.

  According to a sixth aspect of the present invention, in the heat transfer tube for a condenser according to the fourth aspect or the fifth aspect, the formation depth of the notch from the tip of the fin is 0.25 to 0.9 mm. It is characterized by that.

  According to a seventh aspect of the present invention, in the heat transfer pipe for a condenser according to the fourth aspect, the fifth aspect, or the sixth aspect, a spiral rib is provided on the inner surface of the condenser.

  According to an eighth aspect of the present invention, there is provided a heat transfer tube for a condenser that is formed in a tubular shape and is configured to condense refrigerant vapor on the outer surface of the tube, and the tube outer surface is annular in the circumferential direction of the outer surface of the tube. Alternatively, a fin that is continuous in a spiral shape is formed by cutting, and the notch portion formed from the tip end portion to the base end portion of the fin has a continuous direction of the fin. The fins and the notches are arranged on the condenser heat transfer tube while dropping or spraying liquid refrigerant, which is a liquid material of the refrigerant vapor, on the condenser heat transfer tube. It is a heat exchanger tube for a condenser having a dimensional shape determined based on an evaluation result of condensation performance obtained by condensing the refrigerant vapor on the outer surface of the tube.

  According to the present invention, the condensation performance evaluation of the heat transfer tube is performed while dripping or spraying the liquid refrigerant, so the condensation performance evaluation is performed in consideration of the influence of the inundation without requiring a large-scale apparatus configuration and a lot of costs. As a result, it is possible to obtain a condenser heat transfer tube capable of suppressing deterioration of condensation performance due to the influence of inundation. That is, further improvement in condensation performance of the condenser heat transfer tube can be easily realized, thereby contributing to high performance and miniaturization of the heat exchanger.

It is a schematic block diagram of the condensation performance evaluation apparatus which enforces the condensation performance evaluation method which concerns on one Embodiment of this invention. It is a perspective view which shows the tube outer surface shape of the heat exchanger tube for condensers which concerns on one Embodiment of this invention. It is explanatory drawing which shows the detail of the test tube used as evaluation object by the condensation performance evaluation method which concerns on one Embodiment of this invention. It is explanatory drawing which shows one specific example of the evaluation result obtained by the condensation performance evaluation method which concerns on one Embodiment of this invention, and is a figure which shows the relationship between a refrigerant | coolant spraying amount and a heat transfer rate. It is explanatory drawing which shows a specific example of the evaluation result obtained by the condensation performance evaluation method which concerns on one Embodiment of this invention, and is a figure which shows the relationship between the fin pitch of a pipe outer surface, and a heat transfer coefficient. It is explanatory drawing which shows a specific example of the evaluation result obtained by the condensation performance evaluation method which concerns on one Embodiment of this invention, and is a figure which shows the relationship between the fin height of a pipe outer surface, and a heat transfer rate. It is explanatory drawing which shows a specific example of the evaluation result obtained by the condensation performance evaluation method which concerns on one Embodiment of this invention, and is a figure which shows the relationship between the notch depth in the fin of a pipe outer surface, and a heat transfer coefficient. It is a perspective view which shows an example of the pipe outer surface shape of the conventional heat exchanger tube for condensers. It is explanatory drawing which shows an example of the inundation which arises in the condenser which comprises a heat exchanger.

  Hereinafter, an embodiment of a condensation performance evaluation method and a heat transfer tube for a condenser according to the present invention will be described.

<Condensation performance evaluation device>
First, a schematic configuration of a condensation performance evaluation apparatus (hereinafter simply referred to as “evaluation apparatus”) used for carrying out the condensation performance evaluation method of the present embodiment will be described. FIG. 1 is a schematic configuration diagram of an evaluation apparatus described in this embodiment.

The evaluation apparatus has a structure in which a condenser 10 and an evaporator 20 having a tubular outer shell are connected at a plurality of locations by a tubular pipe 31. The outer shells of the condenser 10 and the evaporator 20 are formed of, for example, a stainless steel tube having an outer diameter of 165.2 mm, a thickness of 5.5 mm, and a length of 976 mm, and are arranged to extend in the horizontal direction. Both end edges of the outer shells of the condenser 10 and the evaporator 20 are sealed with, for example, stainless steel wall materials. Moreover, the piping 31 is formed, for example by the stainless steel pipe material of outer diameter 89.1mm and thickness 4.5mm, and is arrange | positioned so that it may extend in a perpendicular direction. Note that the condenser 10 and the evaporator 20 are also connected by a recovery pipe (not shown), and liquid refrigerant obtained by condensation in the condenser 10 is recovered by the evaporator 20 through the recovery pipe. Yes.

  In the shell of the condenser 10, a test tube 40 used for an evaluation test by the evaluation device is installed so as to extend in the horizontal direction in a single tube state. This sample tube 40 is used as a heat transfer tube for a condenser, and is formed of, for example, a copper tube material. In addition, although it is desirable to install the test tube 40 in the state of a single tube, it is not limited to this, and it is also conceivable to install a plurality of tubes side by side. Further, in the shell of the condenser 10, the spray tube 11 is installed on the upper side in the weight direction from the test tube 40 so as to extend in parallel with the test tube 40.

  The test tube 40 in the condenser 10 is configured such that cooling water, which is an example of a cooling fluid, flows from the inlet side toward the outlet side. With this cooling water, the outer surface of the test tube 40 is cooled below the saturation temperature of the refrigerant vapor. The inlet / outlet temperature of the cooling water is measured by platinum resistance thermometers 12a and 12b which are an example of a thermometer. The flow rate of the cooling water is measured by an electromagnetic flow meter 13 that is an example of a flow meter.

  A pressure gauge 14 for measuring the pressure in the shell is connected to the shell of the condenser 10.

  On the other hand, the boiling promotion heat transfer tube 21 is installed in the shell of the evaporator 20 so as to extend in the horizontal direction. Furthermore, the liquid refrigerant 22 is filled in the shell of the evaporator 20 so that the boiling promotion heat transfer tube 21 is submerged.

  The boiling promotion heat transfer tube 21 in the evaporator 20 is configured such that hot water, which is an example of a heating fluid, flows from the inlet side toward the outlet side. This warm water raises the temperature of the liquid refrigerant 22 in the evaporator 20 and raises the pressure thereof to form refrigerant vapor, which is sent into the condenser 10 through the pipe 31. The inlet / outlet temperature of the hot water is measured by platinum resistance thermometers 23a and 23b which are an example of a thermometer. The flow rate of the hot water is measured by an electromagnetic flow meter 24 that is an example of a flow meter.

  One end of a conduit 32 is connected to the lower part of the shell of the evaporator 20. The other end of the conduit 32 is connected to the side wall of the condenser 10 and communicates with the spray tube 11 in the condenser 10. A pump 33 is disposed in the middle of the path of the conduit 32, and the liquid refrigerant 22 in the evaporator 20 is supplied to the spray pipe 11 through the conduit 32 by driving the pump 33. The pump 33 is driven via an inverter (not shown), and the pump discharge amount is adjusted by the inverter. A flow meter 34 for monitoring the flow rate of the liquid refrigerant 22 is disposed in the middle of the path of the conduit 32 between the pump 33 and the spray pipe 11, and the pump discharge amount is feedback-controlled based on the monitoring result. Thus, the supply amount of the liquid refrigerant 22 to the spray tube 11 can be adjusted.

For example, φ1.5 mm holes are provided at intervals of 8 mm in the tube axis direction in the spray tube 11 in the condenser 10 to which the liquid refrigerant 22 is supplied. Through this hole, the liquid refrigerant 22 supplied to the spray tube 11 is sprayed to the test tube 40 located below the spray tube 11. Here, “spreading” refers to spraying the liquid refrigerant 22 in the form of a mist. Note that the liquid refrigerant 22 may be dropped on the test tube 40 instead of being sprayed. “Drip” refers to dropping the liquid refrigerant 22 in the form of droplets. Whether the liquid refrigerant 22 is sprayed or dripped can be switched by appropriately setting the size of a hole provided in the spray pipe 11, the supply amount of the liquid refrigerant 22 to the spray pipe 11, and the like.

<Condensation performance evaluation method>
Subsequently, the procedure of the condensation performance evaluation method performed using the evaluation apparatus having the above-described configuration, that is, the procedure of the condensation performance evaluation method of the present embodiment will be described.

  The condensation performance evaluation method of this embodiment has at least a condensation step and an evaluation step. As long as these steps are included, the presence or absence of steps other than these steps does not matter.

(Condensation process)
In the condensing process, the refrigerant vapor sent from the evaporator 20 through the pipe 31 is actually condensed using the test tube 40 installed in the condenser 10 of the evaluation apparatus. However, the condensation of the refrigerant vapor by the test tube 40 at this time is performed by spraying the liquid refrigerant 22 which is a liquid material of the refrigerant vapor from the hole provided in the spray tube 11 to the test tube 40 in a single tube state. While doing.

  For example, as a specific example of the condensation process, the processing operation described below is performed. First, the test tube 40 in a single tube state is installed in the condenser 10, and after evacuating the system, for example, R 134 a as the liquid refrigerant 22 is sealed in the evaporator 20. Next, for example, the cooling water adjusted so that the inlet temperature becomes 30 ° C. is passed through the test tube 40 in the condenser 10 while adjusting the flow rate so that the flow velocity becomes 1.3 m / s. . Further, R134a in the evaporator 20 is supplied to the spraying tube 11 by driving the pump 33, and R134a is sprayed from the spraying tube 11 to the test tube 40 in the condenser 10. As a result, the outer surface (heat transfer surface) of the test tube 40 is covered with the sprayed R134a, and the portion contributing to the condensation of the refrigerant vapor is reduced.

  When spraying R134a from the spray tube 11, the supply amount of R134a to the spray tube 11 is adjusted through control of the pump discharge amount so that the spray amount becomes a desired amount. By controlling the amount of R134a sprayed from the spray tube 11 in this way, it is possible to simulate the state in which the test tube 40 is arranged in the middle or lower stage of the tube group. In other words, the outer surface of the test tube 40 is covered by controlling the amount of R134a sprayed from the spray tube 11 to be variable depending on which stage in the tube group the test tube 40 is supposed to be arranged. The amount of R134a is adjusted. The same applies to the case where R134a is dropped instead of spraying. In addition, about the value of the desired amount used as an adjustment target, the relationship between the desired amount and the supply amount of R134a to the spray tube 11, etc., it is based on the specifications of the heat exchanger to be configured, empirical rules obtained through experiments, etc. It is conceivable to determine in advance.

  Thereafter, while controlling the temperature and flow rate of the hot water flowing through the boiling promotion heat transfer tube 21 in the evaporator 20, the temperature of the R134a in the evaporator 20 is raised and increased. Then, the refrigerant vapor obtained by raising the temperature of R134a and raising the pressure thereof is sent into the condenser 10 through the pipe 31. At this time, referring to the pressure measurement value by the pressure gauge 14, the temperature rise and pressure increase for the R 134 a in the evaporator 20 are adjusted so that the saturation temperature of the refrigerant vapor becomes 35 ° C., for example.

  When the refrigerant vapor is sent through the pipe 31, in the condenser 10, the outer surface of the test tube 40 is cooled below the saturation temperature by the cooling water flowing in the test tube 40, and the outer surface of the test tube 40 is cooled. The refrigerant vapor in contact with the liquid is condensed and becomes liquid. However, at this time, R134a from the spray tube 11 is sprayed on the test tube 40. Therefore, the test tube 40 condenses the refrigerant vapor in a state where the state arranged in the middle stage or the lower stage in the tube group is created in a simulated manner, that is, in a state in which the influence of the assumed inundation is reflected.

(Evaluation process)
In the evaluation step, the heat transfer coefficient on the outer surface of the sample tube 40 when the sample tube 40 condenses the refrigerant vapor in the condensation step is measured. And based on the measurement result of the heat transfer coefficient, the condensation performance of the test tube 40 is evaluated.

  The method for measuring the heat transfer coefficient is not particularly limited, and may be performed using a known method. Therefore, the detailed description regarding the measurement method is omitted here.

  The evaluation of the condensation performance may be a relative evaluation or an absolute evaluation. In the case of relative evaluation, the heat transfer coefficient is measured for a plurality of test tubes 40 having different tube outer surface shapes, and the measurement results of the respective heat transfer coefficients are compared. Judgment is made. In the case of absolute evaluation, the measurement result of the heat transfer coefficient on the outer surface of the test tube 40 is compared with a preset reference value, and whether or not the performance (condition) specified by the reference value is satisfied. Determine whether.

  If this kind of condensation performance is repeatedly evaluated for test tubes 40 having various tube outer surface shapes, the tube outer surface shape that improves the condensation performance, more specifically, the condensation performance (heat transfer performance) due to the influence of the indentation It becomes possible to find a pipe outer surface shape that can suppress deterioration.

<Configuration of heat exchanger tube for condenser>
Next, the condenser heat transfer tube in which the outer shape of the tube is determined through the condensation performance evaluation by the above-described condensation performance evaluation method will be described. FIG. 2 is a perspective view showing a tube outer surface shape of the heat transfer tube for a condenser described in the present embodiment.

  The heat exchanger tube for a condenser described in the present embodiment is obtained by processing, for example, a copper tube material, and is described below by processing the heat transfer element surface of the tube main body 41 (a smooth surface before processing). It has a tube outer surface shape. On the outer surface of the tube corresponding to the outer peripheral surface of the tube main body 41, fins 42 that are annularly or spirally continuous in the circumferential direction of the outer surface of the tube (see the arrow in the figure) are raised and raised by cutting. Is formed. In the fin 42, valley-shaped notches 43 formed from the tip end portion 42 a to the base end portion 42 b of the fin 42 are arranged at predetermined intervals along the continuous direction of the fin 42. By having such a tube outer surface shape, a plurality of fins 42 are arranged at a predetermined pitch in the tube axis direction on the tube outer surface of the condenser heat transfer tube, and a groove 44 is disposed between adjacent fins 42. It will be.

The heat exchanger tube for a condenser having such a tube outer surface shape can be produced by sequentially performing knurling and cutting. In the knurling, a knurling device having a roll having a plurality of ridges in a spiral shape is mounted on a tool post of a lathe, and this knurling device is fixed to the chuck and brought into contact with the surface of a rotating tube. This is done by moving the tool post along the lead screw. As a result, shallow grooves having a small and continuous interval at a predetermined pitch are formed on the surface of the tube. This shallow groove can be manufactured not only by knurling but also by cutting with a cutting tool. Further, after a shallow groove is formed on the surface of the tube by knurling, cutting is performed in a direction intersecting with the groove (for example, 45 °). Several cutting tools having the same or slightly different cutting edge formation are prepared, each mounted on a plurality of tool rests, and brought into contact with the surface of a rotating tube in the manner of forming a multi-thread screw. For the cutting at this time, cutting that deforms spontaneously without cutting the surface of the tube is used. By repetitive cutting, it becomes possible to bring a fine and deep groove close to each other. By this cutting, the surface of the tube has a deep groove 44 that is spirally continuous and has a small interval, and a V-shaped notch 43 that is isolated by the groove 44 and is shallower than the groove 44 from the tip. Fins 42 are formed. The tip 42a of the fin 42 is above the tube surface before cutting, and the depth of the groove 44 after cutting is larger than the cutting depth of the cutting tool. In the above description, the case where a spiral groove is formed on the pipe surface has been shown as an example. However, when applied to a flat plate surface, the groove does not need to be spiral, and is formed, for example, in a straight line. May be.

  In the heat transfer tube for a condenser having the above-described outer shape of the tube, when the refrigerant vapor is condensed, the liquid film generated on the outer surface of the tube by the condensation or the liquid film formed by combining the liquid droplets is the surface tension of the liquid. Or an action of gravity is added to this and flows to the groove 44 or the notch 43 portion. Therefore, the liquid film in the vicinity of the tip 42a of the fin 42 becomes thin, and the refrigerant vapor is intensely condensed there. That is, the liquid film does not stay in the vicinity of the tip 42a of the fin 42. Further, when the liquid film flowing into the groove 44 reaches a thickness up to the bottom of the notch 43, the flow is disturbed by the notch 43, and as a result, the liquid film is broken and flows into the adjacent groove 44. As a result, the liquid film is kept in a uniform and thin state on the entire outer surface of the tube, thereby obtaining good heat transfer performance.

  Further, the condenser heat transfer tube described in the present embodiment is provided with a spiral rib 45 on the tube inner surface in addition to the above-described tube outer surface shape. The formation method of the rib 45 is not particularly limited, and may be performed using a known method. Therefore, the detailed description regarding the formation method of the rib 45 is abbreviate | omitted here. In the heat transfer tube for a condenser having such a rib 45 on the inner surface of the tube, the heat transfer efficiency between the heat transfer tube for the condenser and the cooling water flowing in the tube is improved as compared with the case where the rib 45 is not provided. Therefore, it contributes to the improvement of the condensation performance (heat transfer performance) in the condenser heat transfer tube through the improvement of the heat transfer efficiency with the cooling water.

<Evaluation example of heat exchanger tube for condenser>
Next, a specific example of the evaluation result of the condensation performance in the case where the heat exchanger tube for a condenser having the outer shape of the tube described above is used as a test tube to be evaluated will be described. The specific example of the evaluation result described here is obtained by performing the evaluation under the conditions exemplified in the description of the condensation performance evaluation method described above.

FIG. 3 is an explanatory diagram showing details of the test tube that is an evaluation target in the present embodiment. From the left in the figure, the tube outer diameter (Df (mm)), fin height (Hf (mm)), fin pitch (Pf (mm)) indicating the distance between the fins, and the tip of the fin are provided after the fins are formed. The notch depth (Dc (mm)), the number of ribs in the circumferential direction (N (pieces)), the rib depth (Dr (mm)) of the rib 45 provided in the pipe, and the angle of the groove 44 with respect to the pipe axis. The rib angle (β (°)) is indicated.

  Example No. shown in the figure. 1-No. 11 is an example of a test tube in which the evaluation result of the condensation performance according to the present embodiment was good. Each of these test tubes has the tube outer surface shape described with reference to FIG. 2, but the dimensions and shapes thereof are different from each other. Further, in the figure, the comparative example No. is also shown for those for which the evaluation result was not good. 1, No. 1 2 is also shown.

  FIG. 4 is a diagram illustrating the relationship between the refrigerant spray amount and the heat transfer coefficient. According to FIG. 1, No. 1 3 is a comparative example. Compared with the case of 1, it can be seen that the deterioration of the heat transfer coefficient can be suppressed even if the amount of liquid refrigerant sprayed is increased. That is, the condensation performance deterioration due to the influence of the inundation can be suppressed. This is considered to be mainly due to the influence of the difference in the height dimension of the fins 42.

FIG. 5 is a diagram showing the relationship between the fin pitch on the outer surface of the pipe and the heat transfer coefficient, and summarizes the heat transfer coefficient on the outer surface of the pipe when the amount of liquid refrigerant sprayed is 7.0 kg / (m · min). It is. The plot in the figure is shown in Example No. 1, no. 2, no. 3, no. 4, no. Cases 5 are shown in order. According to FIG. 1-No. As in each case 5, it is understood that the fin pitch is preferably in the range of 0.5 to 0.7 mm. Here, the fin pitch refers to an arrangement pitch (see symbol Pf in FIG. 2) between adjacent fins 42 in the tube axis direction of the condenser heat transfer tube. That is, in order to be able to suppress the degradation of condensation performance due to the influence of the indentation, it is preferable to set the arrangement pitch of the fins 42 in the tube axis direction within a range of 0.5 to 0.7 mm.

  FIG. 6 is a diagram showing the relationship between the fin height on the outer surface of the pipe and the heat transfer coefficient, and summarizes the heat transfer coefficient on the outer surface of the pipe when the spray amount of the liquid refrigerant is 7.0 kg / (m · min). It is. The plot in the figure is the comparative example No. from the left in the figure. 1, no. 2, Example No. 8, no. 3, no. 7, no. The cases of 6 are shown in order. According to FIG. 8, no. 3, no. 7, no. If the fin height is 6, the comparative example No. 1, no. Compared to 2, it can be seen that a good heat transfer coefficient can be obtained. That is, in order to be able to suppress the degradation of condensation performance due to the influence of the indentation, the fin height on the outer surface of the pipe is set to the example No. 8, no. 3, no. 7, no. Like each case of 6, it is preferable to set it in the range of 0.8-1.1 mm. Here, the fin height refers to the formation height (see symbol Hf in FIG. 2) from the base end portion 42b to the tip end portion 42a of the fin 42 formed on the outer surface of the pipe.

  FIG. 7 is a diagram showing the relationship between the notch depth in the fins on the outer surface of the pipe and the heat transfer coefficient, and summarizes the heat transfer coefficients on the outer surface of the pipe when the spray amount of the liquid refrigerant is 7.0 kg / (m · min). It is a thing. The plot in the figure is shown in Example No. from the left in the figure. 11, no. 3, no. 10, no. The cases of 9 are shown in order. According to this figure, the influence of the notch depth is not as remarkable as the fin pitch and fin height described above, but the performance is improved by increasing the depth. 11, no. 3, no. 10, no. It can be seen that, as in each case of 9, the notch depth is preferably in the range of 0.25 to 0.9 mm. Here, the notch depth refers to the depth of formation of the notch 43 from the tip 42a of the fin 42 formed on the outer surface of the pipe (see symbol Dc in FIG. 2). That is, in order to make it possible to suppress deterioration of condensation performance due to the influence of the indentation, it is preferable that the formation depth of the notch 43 in the fin 42 on the outer surface of the pipe is in the range of 0.25 to 0.9 mm.

  Regarding the fin pitch, fin height, and notch depth, it is conceivable that all of these values fall within the numerical ranges described above. In that case, the notch depth is the formation depth of the notch portion 43 formed in the fin 42, and thus does not exceed the fin height of the fin 42. However, if all of these are not included in the numerical range described above, but are included in the numerical range described above for at least one of the fin pitch, fin height, and notch depth, all of these are out of the numerical range. Compared with the case where it is, it is possible to obtain a favorable heat transfer rate.

<Operational effects of this embodiment>
As described above, in the present embodiment, it is possible to perform the condensation performance evaluation reflecting the influence of the indentation by dropping or spraying the liquid refrigerant 22. Therefore, the outer surface of the pipe that can suppress deterioration of the condensation performance (heat transfer performance) due to the influence of the inundation while avoiding the need for a large-scale apparatus configuration and many costs for the condensation performance evaluation of the test tube 40. The shape can be found.

  Moreover, in this embodiment, the liquid refrigerant 22 is dripped or sprayed on the test tube 40 in a single tube state. Therefore, unlike the case where the condensation performance evaluation is performed in the state of a tube group in which a large number of tubes are arranged, the evaluation (testing) device does not become large, and therefore, a lot of cost is not required. . That is, the condensation performance evaluation of the heat transfer tube reflecting the influence of the inundation can be performed without requiring a large-scale configuration or many costs. In order to simplify the apparatus configuration, reduce costs, etc., it is desirable that the test tube 40 is in a single tube state. For example, a small number of test tubes 40 such as 2 to 3 are installed side by side. However, compared with the case of a tube group in which a large number of tubes are arranged, it is possible to realize simplification of the apparatus configuration and cost reduction.

  Further, in the present embodiment, when the liquid refrigerant 22 is dropped or sprayed on the test tube 40, the dropping amount or the spraying amount is controlled so as to be a desired amount. Therefore, the test tube 40 is arranged in any stage in the tube group. Even in such a case, the arrangement state can be simulated. This means that the condensing performance of the test tube 40 can be evaluated while accurately reflecting the influence of the indentation in the arrangement state, regardless of the stage in the tube group. That is, by making it possible to control the dripping amount or the spraying amount, versatility, flexibility, and the like regarding the application target of the condensation performance evaluation can be sufficiently ensured.

  In addition, if the tube outer surface shape of the condenser heat transfer tube is determined through the condensation performance evaluation described in the present embodiment, the condenser heat transfer tube can reliably suppress the condensation performance deterioration due to the influence of the indentation. . That is, in the condenser heat transfer tube obtained in the present embodiment, the fins 42 and the notches 43 on the outer surface of the condenser drop or spray the liquid refrigerant 22 on the condenser heat transfer tube, Since it has a dimension and shape determined based on the evaluation result of the condensation performance obtained by condensing the refrigerant vapor on the outer surface of the pipe, it is possible to reliably suppress deterioration of the condensation performance due to the influence of the inhibition, and to prevent the influence of the inhibition. Compared to the case where no consideration is given, further improvement in the condensation performance of the heat transfer tube for the condenser is expected. Therefore, if the heat exchanger tube is constructed by incorporating the condenser heat transfer tube into the condenser, it can contribute to high performance and downsizing of the heat exchanger.

  Furthermore, the outer surface shape of the condenser heat transfer tube is the fin pitch, fin height, and notch depth described in the present embodiment, and ribs 45 are formed on the inner surface of the condenser heat transfer tube as described in the present embodiment. If it does so, about the heat exchanger tube for condensers, compared with things other than the structure demonstrated by this embodiment, a condensation performance (heat transfer performance) will improve reliably. That is, according to the present embodiment, it is possible to provide a condenser heat transfer tube that is extremely effective for the induration, and thereby it is possible to reliably achieve high performance, downsizing, etc. of the heat exchanger. become.

  It should be noted that the disclosure content in the present embodiment is merely an example of a preferred embodiment of the present invention. That is, the technical scope of the present invention is not limited to the contents of the present embodiment, and may be changed as appropriate without departing from the scope of the invention. In particular, specific numerical values, materials, and the like exemplified in the present embodiment are not limited to these, and can be implemented with appropriate modifications.

  DESCRIPTION OF SYMBOLS 11 ... Condenser, 11 ... Spreading tube, 20 ... Evaporator, 21 ... Boiling promotion heat transfer tube, 22 ... Liquid refrigerant, 32 ... Conduit, 33 ... Pump, 34 ... Flow meter, 40 ... Test tube, 41 ... Tube body, 42 ... fin, 42a ... tip, 42b ... proximal end, 43 ... notch, 44 ... groove, 45 ... rib

Claims (8)

A condensing step of condensing refrigerant vapor on the outer surface of the test tube used as a heat transfer tube of the condenser;
An evaluation step of evaluating the condensation performance of the test tube based on the heat transfer coefficient at the outer surface of the tube when the test tube condenses the refrigerant vapor,
The condensation performance evaluation method characterized in that in the condensation step, the refrigerant vapor is condensed by the test tube while dropping or spraying a liquid refrigerant that is a liquid material of the refrigerant vapor to the test tube. The condensing performance evaluation method according to claim 1, wherein the liquid refrigerant is dropped or sprayed on the test tube in a single tube state. The condensation performance evaluation method according to claim 1 or 2, wherein a dripping amount or a spraying amount of the liquid refrigerant to the test tube is controlled to a desired amount. A heat transfer tube for a condenser formed in a tubular shape and configured to condense refrigerant vapor on the outer surface of the tube,
On the outer surface of the tube, fins that are continuously or annularly formed in the circumferential direction of the outer surface of the tube are formed by being raised by cutting.
In the fins, notches formed from the front end portion of the fin toward the base end portion are arranged at predetermined intervals along the continuous direction of the fin,
A heat transfer tube for a condenser, wherein a formation height from a base end portion to a tip end portion of the fin is 0.8 to 1.1 mm. The heat exchanger tube for a condenser according to claim 4, wherein an arrangement pitch of the fins adjacent to each other in the tube axis direction of the heat exchanger tube for the condenser is 0.5 to 0.7 mm. The heat transfer tube for a condenser according to claim 4 or 5, wherein a formation depth of the notch from the tip of the fin is 0.25 to 0.9 mm. The heat transfer tube for a condenser according to claim 4, 5 or 6, wherein a spiral rib is provided on the inner surface of the tube. A heat transfer tube for a condenser formed in a tubular shape and configured to condense refrigerant vapor on the outer surface of the tube,
On the outer surface of the tube, fins that are continuously or annularly formed in the circumferential direction of the outer surface of the tube are formed by being raised by cutting.
In the fins, notches formed from the front end portion of the fin toward the base end portion are arranged at predetermined intervals along the continuous direction of the fin,
The fins and the notches are obtained by condensing the refrigerant vapor on the outer surface of the condenser heat transfer tube while dripping or spraying liquid refrigerant, which is a liquid material of the refrigerant vapor, on the condenser heat transfer tube. A heat transfer tube for a condenser, characterized in that it has a dimension and shape determined based on a result of evaluating the obtained condensation performance.

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