CN217818258U - Heat exchange tube and evaporative cooler with same - Google Patents

Abstract

The application relates to a heat exchange tube and an evaporative cooler with the same, wherein the heat exchange tube comprises a tube body, the outer surface of the tube body is provided with a plurality of linear grooves which extend along the axial direction of the tube body and are mutually separated, and the notches and the cross sections of the linear grooves are rectangular; wherein a first interval between any two adjacent linear grooves in the axial direction of the pipe body is less than a second interval between any two adjacent linear grooves in the circumferential direction of the pipe body. This application can be so that the spraying liquid that falls on the heat exchange tube surface can be followed the axial and spread fast, reduces the volume of rebounding of liquid for the liquid film on heat exchange tube surface distributes evenly, eliminates the dry problem on heat exchange tube surface, thereby improves the heat exchange efficiency of heat exchange tube.

Description

Heat exchange tube and evaporative cooler with same

Technical Field

The application relates to the field of heat exchange, in particular to a heat exchange tube and an evaporative cooler with the same.

Background

The evaporative cooler is an energy-saving and water-saving heat exchanger device, and is particularly suitable for the northern cold and dry climate environment. The working principle of the evaporative cooler is as follows: a fan and spraying equipment are arranged above the heat exchange tube bundle, and when the ambient temperature is low, air is sucked from the lower part of the heat exchange tube bundle to exchange heat with hot fluid in the tube bundle through the suction effect of the fan, so that the air is directly cooled by the air. In summer, when the ambient temperature is high, the fan still sucks air from the lower part of the tube bundle, meanwhile, the spraying equipment above the tube bundle sprays water, the wet bulb temperature at the inlet of the air is greatly reduced under the influence of the sprayed water, and therefore the heat exchange temperature difference of the convection heat exchange is increased; on the other hand, the spray water forms a liquid film on the surface of the heat exchange tube, the spray water is heated by hot fluid in the tube, phase change occurs to generate an evaporation phenomenon, and steam carries a large amount of latent heat, so that the heat exchange efficiency is further improved.

The heat exchange tube is a key element of the evaporative cooler, and in consideration of the spraying process in the work of the evaporative cooler, technicians often adopt the efficient falling film evaporation tube as the heat exchange tube of the evaporative cooler. Chinese patent CN208356130U proposes to adopt an elliptical tube in a falling film evaporator, and the length-to-axis ratio of the elliptical tube is 2:1; the elliptical tube bundles are obliquely arranged, and the included angle between the tube bundles and the horizontal direction is 2-5 degrees. Chinese patent CN113137786A proposes that on the heat exchange tube of horizontal arrangement in the horizontal tube falling film evaporator, set up banded guide plate, the guide plate is arranged perpendicularly, and its minor face both sides are connected the top and the bottom of two upper and lower root canals respectively, and the guide plate is favorable to the liquid film to cover the heat exchange tube surface completely, avoids appearing dryly.

In the evaporative cooler, since the orifices through which the liquid is sprayed are spaced apart, the liquid film is thick where the water drops dropping through the orifices strike the surface of the heat exchange tube, and the other surfaces that do not receive the strike lack the liquid film, the liquid distribution on the surface of the heat exchange tube is uneven, which affects the heat exchange efficiency of the heat exchange tube.

Disclosure of Invention

In view of the above, the present application provides a heat exchange tube and an evaporative cooler having the same, so that spray liquid falling on the outer surface of the heat exchange tube can be quickly spread along the axial direction, the rebound amount of the liquid is reduced, the liquid film is uniformly distributed, and the problem of dryness of the outer surface of the heat exchange tube is solved.

In a first aspect, the present application provides a heat exchange tube, including a tube body, wherein the outer surface of the tube body is provided with a plurality of linear grooves extending along the axial direction of the tube body and spaced from each other, and the notches and the cross sections of the linear grooves are rectangular;

wherein a first interval between any two adjacent linear grooves in the axial direction of the pipe body is less than a second interval between any two adjacent linear grooves in the circumferential direction of the pipe body.

In a first possible embodiment in combination with the first aspect, the linear grooves have a rectangular cross section, and the linear grooves have a width of 0.05 to 0.1mm, a length of 0.3 to 0.6mm, and a depth of 0.03 to 0.8mm.

With reference to the first aspect or the first possible implementation manner of the first aspect, in a second possible implementation manner, the first pitch is 1 to 3 times the width, and the second pitch is 8 to 12 times the width.

In a third possible embodiment in combination with the first aspect, a total surface area of the plurality of linear grooves is not less than 20% of an outer surface area of the pipe body.

In a fourth possible embodiment in combination with the first aspect, the plurality of linear grooves includes a plurality of groove groups arranged at intervals along an axial direction of the pipe body, and each groove group includes at least two linear grooves arranged at intervals along a circumferential direction of the pipe body.

In combination with the fourth possible embodiment of the first aspect, in a fifth possible embodiment, each of the groove sets includes the same number of the linear grooves;

for any two adjacent groove groups, the linear grooves in the two groove groups are aligned in a one-to-one correspondence manner in the axial direction of the pipe body.

With reference to the fourth possible embodiment of the first aspect, in a sixth possible embodiment, each of the linear grooves in the same groove group has the same length dimension and is aligned along the circumferential direction of the pipe body.

With reference to the first aspect, in a seventh possible implementation manner, the outer surface of the pipe body is a hydrophilic surface subjected to hydrophilic treatment.

In an eighth possible embodiment, in combination with the first aspect, the linear groove is obtained by laser cauterization of the outer surface of the tubular body.

In a second aspect, the present application provides an evaporative cooler comprising a heat exchange tube as provided in the first aspect or any one of the possible embodiments of the first aspect.

According to the heat exchange tube of the application, the surface of its body is provided with a plurality of linear type recesses that extend and separate each other along the axial direction of this body, and the notch and the cross section of linear type recess are the rectangle recess of rectangle. The radius of curvature of the droplet landed on the outer surface of the tube body in the length direction of the rectangular groove is larger than the radius of curvature in the width direction, and thus the capillary force of the droplet in the length direction of the rectangle is smaller than the capillary force in the width direction. Therefore, during the spreading process, the liquid is restrained by the capillary force in the length direction to be less than the capillary force in the width direction, and the liquid is easy to spread and flow along the axial direction, so that the spraying liquid can be fully spread and flow along the axial direction in the period from the time when the spraying liquid drops on the surface of the heat exchange tube to the time when the spraying liquid leaves the heat exchange tube, the rebound amount of the liquid is reduced, and the drying-out is reduced or eliminated.

According to the heat exchange tube of the application, the distance between any two adjacent linear grooves in the axial direction of the tube body is smaller than the distance between any two adjacent linear grooves in the circumferential direction of the tube body. So, compare in the distance of linear type recess along body axial direction, increased the distance of linear type recess along the circumferential direction in other words, reduce the figure of linear type recess in the circumferential direction, will reduce the air stock in the recess and with liquid area of contact, and then reduce the influence of Cassie state. Thus, the lag angle of the liquid drop flowing along the circumferential direction is increased, and the flow rate along the circumferential direction is reduced, so that the spreading range of the liquid drop outside the pipe along the axial direction is expanded.

Drawings

To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description only relate to some embodiments of the present application and are not limiting on the present application.

Fig. 1 is a schematic structural diagram of a heat exchange tube in an embodiment of the present application.

Fig. 2 is an enlarged schematic view of a portion B in fig. 1.

Description of reference numerals:

1-a pipe body, 1 a-the outer surface of the pipe body, 2-a linear groove;

the length of the L-linear groove and the width of the W-linear groove;

d1-first pitch, D2-second pitch.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings of the embodiments of the present application. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the application without any inventive step, are within the scope of protection of the application. It will be understood that some of the technical means of the various embodiments described herein may be replaced or combined with each other without conflict.

In the description of the present application and claims, the terms "first," "second," and the like, if any, are used solely to distinguish one from another as between described objects and not necessarily in any sequential or technical sense. Thus, an object defined as "first," "second," etc. may explicitly or implicitly include one or more of the object. Also, the use of the terms "a" or "an" and the like, do not denote a limitation of quantity, but rather denote the presence of at least one of the two, and "a plurality" denotes no less than two.

Fig. 1 and 2 show one embodiment of a heat exchange tube according to the present application, which comprises a tube body 1, and an outer surface 1a of the tube body 1 is provided with a plurality of linear grooves 2 extending in an axial direction of the tube body 1 while being spaced apart from each other. The notch of the linear groove 2 is rectangular, and the cross section of the linear groove 2 in the radial direction of the pipe body 1 is also rectangular, and therefore, it will be referred to as a rectangular groove hereinafter. The first distance D1 between any two adjacent linear grooves 2 in the axial direction of the pipe body 1 is less than the second distance D2 between any two adjacent linear grooves 2 in the circumferential direction of the pipe body 1. The first distance D1 and the second distance D2 are both linear distances, as can be seen in fig. 2.

On the surface of a solid, the spreading performance of a liquid is expressed in terms of the contact angle of the liquid and a gas. When the contact angle is less than 90 deg., it is called a hydrophilic surface, and when the contact angle is less than 10 deg., it is called a superhydrophilic surface. When the contact angle is greater than 90 °, it is called a hydrophobic surface, and when the contact angle is greater than 150 °, it is called a superhydrophobic surface. The wettability of solid surfaces is a result of the combination of the physical properties of the material and the roughness of the surface. Early studies of the correlation of surface condition and wettability by Wenzel theory showed that the actual contact area of a liquid with a solid surface was larger than that of an ideal smooth surface. Thus, when the surface is a hydrophilic surface, the hydrophilic property is enhanced in a rough surface as compared with a smooth surface; in contrast, when the surface is a hydrophobic surface, the hydrophobic nature of a rough surface is more hydrophobic than a smooth surface. The rough surface can be divided into two categories: regular, ordered (engineered) rough surfaces and random, disordered (random) rough surfaces. The heat exchange surface is often roughened by sand blasting in engineering so as to improve the wettability of the surface. The surface structure produced by this method is random and disordered, the roughness of the surface is usually expressed by the average roughness, and the wettability produced by the method is isotropic. On spray equipment in evaporative coolers, the spray orifices are separated, with a distance between the spray orifices. When the spraying liquid drops on the surface of the heat exchange tube, the liquid film is distributed unevenly, and the liquid film on the heat exchange surface is required to be distributed evenly, so that the liquid can be quickly spread along the axial direction of the heat exchange tube, and the surface between the adjacent liquid drops is wetted. In the case of the isotropic wettability, since the liquid is influenced by gravity during the flow in the circumferential direction and the flow velocity is higher than the flow velocity in the axial direction, a large amount of the liquid flows downward and exits the heat exchange tube, and the flow in the axial direction and the spreading are influenced. In order to overcome this drawback, it is required that wettability is directional, that is, wettability in the axial direction is stronger than wettability in the circumferential direction.

According to the heat exchange tube provided by the embodiment, the heat exchange tube has the outer surfaces of a large number of micro linear grooves which are regularly arranged, so that the heat exchange tube has the characteristics and the performance of a conventional rough surface, the surface wettability of the micro grooves is adjusted by controlling the parameters such as the shapes, the intervals and the like of the micro grooves, the axial wettability and the circumferential wettability are different, and the spraying liquid can fully spread and flow along the axial direction in the time period after dropping on the surface of the heat exchange tube until leaving the heat exchange tube, so that the dryness is avoided. The specific analysis is as follows:

in practice, the heat exchange tubes may be arranged horizontally in an evaporative cooler. After impacting the surface of the heat exchange tube, the falling liquid drops can spread in the horizontal direction, namely the axial direction of the tube body 1, under the driving of the self kinetic energy (derived from the conversion of the potential energy of the liquid drops), and the spreading of the liquid drops needs to overcome the constraint of the capillary force of the gas-liquid interface and the viscous friction force in the flowing process. According to the young-laplace theory, it is believed that the gas-liquid interface at the rectangular groove has two major axis curvatures, respectively a curvature along the length direction and a curvature along the width direction. The capillary force generated by the curved surface is related to the curvature radius, and the larger the curvature radius is, the smaller the capillary force is; conversely, the smaller the radius of curvature, the greater the capillary force. In the case of a rectangular groove, the radius of curvature of the droplet in the length direction of the rectangular groove is larger than the radius of curvature in the width direction, and thus the capillary force of the droplet in the length direction of the rectangular groove is smaller than the capillary force in the width direction. Therefore, the liquid is restrained by a capillary force in the lengthwise direction less than in the widthwise direction during the spreading process. Therefore, considering the influence of the capillary force of the liquid on the surface of the heat exchange tube, under the condition that the length direction of the rectangular groove is parallel to the axial direction of the heat exchange tube, the spreading performance of the liquid along the axial direction (namely the length direction) of the heat exchange tube is stronger than the spreading performance along the circumferential direction of the heat exchange tube, the liquid can more easily spread and flow along the axial direction, and thus the liquid film on the outer surface of the heat exchange tube is more uniform.

On the other hand, in the circumferential flow process of the liquid drops after impacting the surface, the liquid is subjected to gravity, and the flow mechanism of the liquid drops is different from that of the horizontal flow. In this case, the influence of the lag angle of the droplets is taken into consideration. The retardation angle is defined as a difference between the advancing angle and the receding angle. The size of the lag angle reflects the size of the adhesive force of the flowing liquid, and the smaller the lag angle is, the easier the flowing is; conversely, the larger the lag angle, the larger the adhesion force and the more difficult the flow. The magnitude of the lag angle is linked to the surface microstructure. When the rectangular grooves are covered with the liquid film, a small amount of gas is easily present at the bottoms thereof, so that the liquid film forms a Cassie state. In the Cassie state, the lag angle is small, and the circumferential flow speed and the circumferential flow rate of the liquid become large under the action of gravity. This is detrimental to the flow of liquid in the axial direction and wetting of the surface between the drops. In this regard, the first distance D1 of two linear grooves 2 that are arbitrarily adjacent in the axial direction of the pipe body 1 < the second distance D2 of two linear grooves 2 that are arbitrarily adjacent in the circumferential direction of the pipe body 1. So, compare in the distance of linear type recess 2 along body 1 axial direction, increased linear type recess 2 along the distance of circumferential direction in other words, reduce the number of linear type recess 2 in the circumferential direction, will reduce the air stock in the recess and with liquid area of contact, and then reduce the influence of Cassie state to increased along the lag angle of the liquid drop of circumferential flow, increased along the adhesive force of circumferential flow, reduced along the flow of circumference, enlarged the scope that liquid was spreaded along the axial.

The size and the space of the linear grooves 2 are not too large or too small. The linear groove 2 having an excessively large size makes it impossible to provide the pipe body 1 with the characteristics and properties of a rough surface with which the liquid cannot be brought into the above-mentioned contact state, and the linear groove 2 having an excessively small size is difficult to machine. In general, the linear grooves 2 preferably have a width W of 0.05 to 0.1mm, a length L of 0.3 to 0.6mm and a depth of 0.03 to 0.8mm. The first distance D1 is preferably 1 to 3 times the width W, and the second distance D2 is preferably 8 to 12 times the width W. Moreover, the total surface area of all the linear grooves 2 is preferably not less than 20% of the area of the nonlinear groove region (smooth surface region) of the pipe body 1.

It is to be noted that the surface area of the single rectilinear groove 2 is: the sum of the areas of the bottom wall surface and the four side wall surfaces of the linear groove 2.

Referring to fig. 2 in conjunction with fig. 1, in the present embodiment, the plurality of linear grooves 2 includes a plurality of groove sets (not all four sets are shown in fig. 2) arranged at intervals along the axial direction of the pipe body 1, and each groove set includes at least two linear grooves 2 arranged at intervals along the circumferential direction of the pipe body 1. In other words, all the linear grooves 2 on the outer surface of the pipe body 1 are arranged in a plurality of groups spaced apart from one another in the axial direction of the pipe body 1, and each groove group includes at least two linear grooves 2 spaced apart in the circumferential direction of the pipe body 1.

Referring to fig. 2 in conjunction with fig. 1, in the present embodiment, the number of the straight-line grooves 2 in each groove set is equal. For any two adjacent groove groups, the linear grooves 2 are aligned in a one-to-one correspondence in the axial direction of the pipe body 1. Each of the linear grooves 2 in the same groove group has the same length dimension and is aligned in the circumferential direction of the pipe body 1. Further, all the linear grooves 2 have the same length and width dimensions. This design has the advantage of facilitating the production of the linear grooves 2, which linear grooves 2 are obtained, in the present embodiment, by laser ablation of the outer surface of the tubular body 1.

The outer surface of body 1 in this embodiment is the hydrophilic surface through hydrophilic treatment to promote the hydrophilic performance of body 1 outer surface, and further promote the range of spreading of liquid drop at body 1 outer surface.

In this embodiment, the tube body 1 is a copper tube. In other embodiments, the tubular body 1 may also be a steel tube, such as a stainless steel tube or a carbon steel tube.

The embodiment also provides a manufacturing method of the heat exchange tube, which comprises the following steps:

s1: and taking a copper pipe of phi 19, and cleaning the copper pipe before laser ablation. The step S1 specifically includes:

and S101, cleaning the surface of the fabric piece in a cleaning tank by using a laundry detergent. Then, deionized water is ultrasonically cleaned.

S102, immersing the heat exchange tube in 2.0mol/L HCL aqueous solution to remove the metal oxide film.

S103, ultrasonically cleaning by using deionized water to remove residual acid liquor on the surface of the heat exchange tube; and then blown dry using nitrogen.

And S2, carrying out laser ablation on the cleaned copper pipe. The operating parameters for laser ablation are as follows:

power (W)	50
		Frequency (kHZ)	80
Pulse width (ns)	400
		Scanning speed (mm/s)	20000
Filling space (mm)	0.01

After laser ablation treatment, a large number of rectangular grooves are formed on the surface of the copper pipe, and the shape and the arrangement size of each rectangular groove are as follows:

length L (mm) of the rectangular groove	0.3
		Width W (mm) of the rectangular groove	0.05
Depth h (mm) of the rectangular groove	0.03
		Axial spacing of rectangular groove D1 (mm)	0.05
Circumferential spacing of rectangular groove D2 (mm)	0.4

And S3, performing hydrophilic treatment on the copper pipe subjected to the laser ablation treatment. The step S3 specifically includes:

and S301, soaking the copper pipe in deionized water again, and performing ultrasonic cleaning treatment.

S302, preparing a metal oxide solution formed by mixing NaClO, naOH, na3PO4 and distilled water; wherein the mass ratio of NaClO, naOH, na3PO4 and distilled water is 3.75:5:10:100.

s303, immersing the copper pipe into the prepared metal oxidation liquid, and keeping the temperature at 95 ℃ for 15 minutes.

And S304, blowing the oxidized copper pipe by using nitrogen.

Through the test, the heat exchange tube provided by the embodiment has an outer surface contact angle of about 4 degrees, and the heat exchange coefficient is improved by 2.2 times compared with that of a smooth copper tube. The total heat transfer coefficient of the evaporative cooler provided with the heat exchange tube with the structure is improved by 1.6 times compared with that of the evaporative cooler provided with a conventional smooth copper tube.

Claims (10)

1. A heat exchange tube comprises a tube body, and is characterized in that a plurality of linear grooves which extend along the axial direction of the tube body and are mutually separated are arranged on the outer surface of the tube body, and the notches and the cross sections of the linear grooves are rectangular;

wherein a first interval between any two adjacent linear grooves in the axial direction of the pipe body is less than a second interval between any two adjacent linear grooves in the circumferential direction of the pipe body.

2. The heat exchange tube of claim 1, wherein the linear grooves have a width of 0.05 to 0.1mm, a length of 0.3 to 0.6mm and a depth of 0.03 to 0.8mm.

3. A heat exchange tube according to claim 2, wherein the first pitch is 1 to 3 times the width and the second pitch is 8 to 12 times the width.

4. A heat exchange tube according to any one of claims 1 to 3, wherein the total surface area of the plurality of linear grooves is not less than 20% of the outer surface area of the tube body.

5. The heat exchange tube of claim 1, wherein the plurality of linear grooves comprises a plurality of groove groups arranged at intervals in the axial direction of the tube body, each of the groove groups comprising at least two of the linear grooves arranged at intervals in the circumferential direction of the tube body.

6. The heat exchange tube of claim 5 wherein each of said groove sets comprises the same number of said linear grooves;

for any two adjacent groove groups, the linear grooves in the two groove groups are aligned in a one-to-one correspondence manner in the axial direction of the pipe body.

7. The heat exchange tube of claim 5, wherein each of the linear grooves in the same groove group has the same length dimension and is aligned in a circumferential direction of the tube body.

8. A heat exchange tube according to claim 1, wherein the outer surface of the tube body is a hydrophilic surface subjected to hydrophilic treatment.

9. The heat exchange tube of claim 1, wherein the linear grooves are obtained by laser cauterization of the outer surface of the tube body.

10. An evaporative cooler comprising a heat exchange tube as claimed in any one of claims 1 to 9.

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