CN108332453B

CN108332453B - Composite evaporative condenser

Info

Publication number: CN108332453B
Application number: CN201810122190.2A
Authority: CN
Inventors: 韩宗伟; 魏昊天; 白晨光; 付琪; 胡洪昊; 李彪; 孟新巍
Original assignee: Northeastern University China
Current assignee: Northeastern University China
Priority date: 2018-02-07
Filing date: 2018-02-07
Publication date: 2020-01-03
Anticipated expiration: 2038-02-07
Also published as: CN108332453A

Abstract

The invention provides a composite evaporative condenser, which consists of a fan, a water baffle, an air-cooled heat exchanger, a spraying device, a heat dissipation filler, an evaporative heat exchanger, an air inlet grid, a hydrophobic plate, a water collection tank, a water-cooled heat exchanger and a submersible pump. The invention can realize the switching of three operation modes, namely an air cooling mode, a direct evaporative cooling mode and an indirect evaporative cooling mode, through the switch of the valve and the air inlet grid. Meanwhile, the spray device is separated from the heat exchange coil by the condenser, the problems of scaling and corrosion on the surface of the heat exchange coil are solved, the spiral plate type heat exchanger is additionally arranged to supercool the refrigerant, and the condenser has the characteristics of compact structure, high heat exchange efficiency, high operation flexibility, wide application range and the like.

Description

Composite evaporative condenser

Technical Field

The invention belongs to the field of refrigeration air-conditioning equipment, and particularly relates to a composite evaporative condenser.

Background

In recent years, with the deep and rapid development of informatization in China, the demands of people on data processing and information exchange are increasing, and information resources become three major factors of mankind parallel to energy and materials. The power consumption of a refrigerating system in the data center accounts for about 30-40% of the energy consumption of the whole data center. Reducing the energy consumption of the refrigeration system is the most direct and effective measure to improve the energy utilization efficiency of a data center.

The heat pipe heat exchange technology and the vapor compression refrigeration technology are combined and applied to a data machine room which needs to supply cold all year round, the energy saving performance, the reliability and the economy of an air conditioning system of the machine room are considered, and the heat pipe heat exchange technology and the vapor compression refrigeration technology are well popularized. The system can realize free switching of vapor compression refrigeration and heat pipe heat exchange modes through switching of the valve, only the valve and the pipeline are additionally arranged in the traditional air conditioning system, and the two modes share one set of condenser and evaporator, so that the improvement of the heat exchange efficiency of the condenser becomes more important for a data machine room needing cooling all the year round. At present, condensers which are commonly used in a refrigeration device mainly comprise a wind-cooling condenser, a water-cooling condenser and an evaporative condenser, and the application of various cooling technologies has respective disadvantages. For example, the air-cooled condenser has low heat exchange efficiency when the outdoor environment temperature is high, and the water-cooled heat exchanger and the evaporative condenser have the problems of corrosion, scaling, freezing prevention and the like of a heat exchange coil. The development of a condenser capable of realizing efficient and reliable heat exchange all year around has important significance for improving the energy efficiency of a refrigerating system of an all year around cooling object represented by a data center.

Disclosure of Invention

In order to solve the technical problems, the invention aims to provide a composite evaporative condenser which can realize efficient and reliable heat exchange.

The invention provides a composite evaporative condenser, comprising: fan, breakwater, air-cooled heat exchanger, spray set, heat dissipation filler, evaporative heat exchanger, hydrophobic board, header tank, water-cooled heat exchanger and immersible pump:

the condenser consists of a first box body, a second box body and a third box body, wherein the first box body and the third box body have the same internal structure and are symmetrically arranged at two sides of the second box body; in the first box and the third box: the fan is arranged at the top of the box body, and a water baffle is arranged below the fan; the heat dissipation filler is positioned in the middle of the box body, and the spraying device is positioned between the water baffle and the heat dissipation filler; the water collecting tank is positioned at the bottom of the box body, and the evaporative heat exchanger is positioned between the heat dissipation filler and the water collecting tank; the first air inlet grids are embedded on the front surface and the rear surface of the box body and are positioned between the evaporative heat exchanger and the water collecting tank; the water collecting tanks of the first tank body and the third tank body are communicated with each other through a bottom channel of the second tank body;

in the second box: the fan is positioned at the top of the second box body, and the air-cooled heat exchanger is arranged below the fan; the heat dissipation filler is positioned in the middle of the second box body, a spraying device is arranged above the heat dissipation filler, and the water baffle is positioned between the air-cooled radiator and the spraying device; the water-cooling heat exchanger is positioned at the bottom of the second box body, and a hydrophobic plate is arranged above the water-cooling heat exchanger; the second air inlet grids are embedded in the front surface and the rear surface of the second box body and are positioned between the heat dissipation filler and the drainage plate; the air-cooled heat exchanger is connected with the water-cooled heat exchanger through a connecting pipe; and the spraying devices in the first box body, the second box body and the third box body are communicated and connected with the water-cooling heat exchanger.

In the composite evaporative condenser, the water-cooled heat exchanger is a spiral plate heat exchanger, the heat exchanger is formed by rolling two parallel steel plates into mutually separated spiral flow passages, cover plates are welded on the upper surface and the lower surface, cold and hot fluids flow in the two flow passages respectively, and the water-cooled heat exchanger is provided with a first inlet, a first outlet, a second inlet and a second outlet.

In the composite evaporative condenser, the refrigerant flows into the air-cooled heat exchanger, flows in from the first inlet of the water-cooled heat exchanger through the connecting pipe after being cooled, and flows out from the first outlet of the water-cooled heat exchanger after being cooled again, so that the whole flow of the refrigerant in the condenser is completed.

In the composite evaporative condenser, cooling water flows into the water-cooled heat exchanger from a second inlet under the drive of the submersible pump, the cooling water after heat exchange flows out of a second outlet of the water-cooled heat exchanger and then is divided into a left branch and a right branch, the left branch and the right branch extend upwards along the left wall surface and the right wall surface of the second box body, then pass through the wall surface of the second box body, respectively enter the spraying devices of the first box body and the third box body, are sprayed out by the nozzle, sequentially pass through the heat dissipation filler and the evaporative heat exchanger under the action of gravity, and respectively fall into the water collection tanks of the first box body and the third box body;

the cooling water divided into the two branches converges in the spraying device of the second box body, is uniformly sprayed on the surface of the heat dissipation filler from the nozzle, falls on the drain board under the action of gravity, is divided into a left water flow and a right water flow through the drain board, and flows into the water collection tanks of the first box body and the third box body respectively.

In the composite evaporative condenser, the evaporative heat exchanger is an indirect evaporative cooler; the primary air respectively enters the heat exchange pipes of the evaporative heat exchangers of the first box body and the third box body, enters the second box body after evaporation and heat exchange, sequentially sweeps the heat dissipation filler, the water baffle and the air-cooled heat exchanger of the second box body upwards, and finally flows into the atmosphere through the fan on the second box body.

In the composite evaporative condenser, secondary air respectively enters the first air inlet grids of the first box body and the third box body, then sequentially sweeps upwards through the evaporative heat exchanger, the heat dissipation filler and the water baffle in the first box body and the third box body, and finally flows into the atmosphere through the fans on the first box body and the third box body.

In the composite evaporative condenser of the invention, the second air inlet grid is a movable air inlet grid with an adjustable opening and closing state; when the second air inlet grid is opened, outdoor air enters the second box body from the second air inlet grid, sequentially sweeps upwards the heat dissipation filler, the water baffle and the air-cooled heat exchanger in the second box body, and finally flows into the atmosphere through the fan on the second box body.

In the composite evaporative condenser, the air-cooled heat exchanger is a fin heat exchange coil or a light pipe type heat exchanger.

In the composite evaporative condenser, the drain plate is of a herringbone structure and is fixed in the second box body, and drain openings communicated with the first box body and the third box body are formed in the tail ends of the two sides of the drain plate.

In the composite evaporative condenser, a fifth valve is arranged between the water-cooling heat exchanger and the submersible pump, and a sixth valve is arranged on a connecting pipe for connecting the air-cooling heat exchanger and the water-cooling heat exchanger; a first valve and a second valve are arranged on a branch of the water-cooled heat exchanger connected with the spraying device in the first box body; a third valve and a fourth valve are arranged on a branch of the water-cooled heat exchanger connected with the spraying device in the third box body; the switching of the operation modes of the condenser is realized by adjusting the switching states of the first valve, the second valve, the third valve, the fourth valve, the fifth valve, the sixth valve and the second air inlet grid.

The invention provides a composite evaporative condenser, which simultaneously applies an air cooling technology, a water cooling technology and an evaporative cooling technology, can switch three operation modes, namely an air cooling mode, a direct evaporative cooling mode and an indirect evaporative cooling mode according to different operation working conditions, and utilizes spray water cold energy to supercool a refrigerant by means of a spiral plate type heat exchanger. The invention also separates the heat exchanger from the spraying device, and solves the problems of scaling, corrosion and the like on the surface of the heat exchange tube in the condenser. Meanwhile, the evaporative cooling function of the invention can reduce the cooling limit of the condenser side of the system from the dry bulb temperature to the wet bulb temperature, even lower, thereby not only greatly improving the performance of the vapor compression refrigeration mode, but also improving the running performance and running time of the heat pipe heat exchange mode, and ensuring that the air conditioning system of the machine room has energy conservation, reliability and economy.

Drawings

Fig. 1 is a schematic structural view of a composite evaporative condenser according to the present invention;

FIG. 2 is a longitudinal sectional view of a water-cooled heat exchanger according to the present invention;

FIG. 3 is a transverse sectional view of the water-cooled heat exchanger according to the present invention;

fig. 4 is a schematic view of an evaporative heat exchanger according to the present invention.

Detailed Description

As shown in fig. 1, the composite evaporative condenser of the present invention includes: a first casing 1, a second casing 3, and a third casing 7. The box body is internally provided with a fan 4, a water baffle 28, an air-cooled heat exchanger 5, a spraying device 6, a heat dissipation filler 26, an evaporative heat exchanger 11, a first air inlet grid 23, a second air inlet grid 9, a hydrophobic plate 10, a water collecting tank 22, a water-cooled heat exchanger 17 and a submersible pump 14. The first box body 1 and the third box body 7 have the same internal structure and are symmetrically arranged at two sides of the second box body 3.

The first casing 1 and the third casing 7 have the same internal structure, and in the first casing 1 and the third casing 7: the fan 4 is arranged at the top of the corresponding box body, and a water baffle 28 is arranged below the fan 4; the heat dissipation filler 26 is positioned in the middle of the box body, and the spraying device 6 is positioned between the water baffle 28 and the heat dissipation filler 26; the water collecting tank 22 is positioned at the bottom of the box body, and the evaporative heat exchanger 11 is positioned between the heat dissipation filler 26 and the water collecting tank 22; the first air inlet grids 23 are embedded on the front surface and the rear surface of the box body and are positioned between the evaporative heat exchanger 11 and the water collecting tank 22; the water collecting tanks of the first tank body 1 and the third tank body 7 are communicated with each other through a bottom channel of the second tank body 3.

In the second casing 3: the fan 4 is positioned at the top of the second box body 3, and the air-cooled heat exchanger 5 is arranged below the fan 4; the heat dissipation filler 26 is positioned in the middle of the second box body 3, the spraying device 6 is arranged above the heat dissipation filler 26, and the water baffle 28 is positioned between the air-cooled heat exchanger 5 and the spraying device 6; the water-cooling heat exchanger 17 is positioned at the bottom of the second box body 3, and a hydrophobic plate 10 is arranged above the water-cooling heat exchanger 17; the second air inlet grids 9 are embedded in the front and rear surfaces of the second box body 3 and are positioned between the heat dissipation filler 26 and the hydrophobic plate 10; the air-cooled heat exchanger 5 is connected with the water-cooled heat exchanger 17 through a connecting pipe; the spraying devices 6 in the first box body 1, the second box body 3 and the third box body 7 are communicated to form a spraying system, and the spraying system is connected with a water-cooling heat exchanger 17.

As shown in fig. 2 and 3, the water-cooled heat exchanger 17 is a spiral plate heat exchanger, which is a novel heat exchanger, the heat exchanger is formed by rolling two parallel steel plates into mutually separated spiral flow passages, the upper and lower surfaces are welded with cover plates, and cold and hot fluids flow in the two flow passages respectively, because the curvature of the spiral passage is uniform, the liquid flows in the equipment without large steering, the flow resistance is small, two heat transfer media can flow in a full-countercurrent manner, even if the two small temperature difference media flow, an ideal heat exchange effect can be achieved, and under the condition of the same pressure loss, the heat transfer capacity of the spiral plate heat exchanger is 3-5 times that of a tubular heat exchanger.

The water-cooled heat exchanger 17 is provided with a first inlet 20, a first outlet 18, a second inlet 15 and a second outlet 19, and a water discharge port 16.

The air-cooled heat exchanger 5 is a fin heat exchange coil or a light pipe type heat exchanger, the fin heat exchange coil shown in fig. 1 can be adopted in specific implementation, and the heat exchange area between air and the air-cooled heat exchanger 5 is increased by arranging fins, so that the effect of enhancing heat exchange is achieved.

The refrigerant flows into the air-cooled heat exchanger 5, is cooled, flows in from the first inlet 20 of the water-cooled heat exchanger 17 through the connecting pipe, is cooled again, and flows out 18 from the first outlet of the water-cooled heat exchanger 17, and the whole flow of the refrigerant in the condenser is completed.

The cooling water flows into the water-cooled heat exchanger 17 from the second inlet 15 under the driving of the submersible pump 14, the cooling water after heat exchange flows out from the second outlet 19 of the water-cooled heat exchanger 17 and then is divided into a left branch and a right branch, the left branch and the right branch extend upwards along the left wall and the right wall of the second box body 3, then pass through the wall of the second box body 3, respectively enter the spraying devices 6 of the first box body 1 and the third box body 7, are sprayed out by the nozzles, sequentially pass through the heat dissipation filler 26 and the evaporative heat exchanger 11 under the action of gravity, and respectively fall into the water collection tanks 22 of the first box body 1 and the third box body 7.

The cooling water divided into two branches converges to the spraying device 6 of the second box body 3, is uniformly sprayed on the surface of the heat dissipation filler 26 from a nozzle, then falls on the hydrophobic plate 10 under the action of gravity, is divided into a left water flow and a right water flow through the hydrophobic plate 10, and respectively flows into the water collection tanks 22 of the first box body 1 and the third box body 7.

As shown in fig. 4, the evaporative heat exchanger 11 is an indirect evaporative cooler, such as a plate-type indirect evaporative cooler and a tube-type indirect evaporative cooler. In specific implementation, a fin tube type indirect evaporative cooler as shown in fig. 4 can be adopted, the first box body 1 and the third box body 7 are arranged in the first box body and the third box body, and are bilaterally symmetrical about the second box body 3, primary air flows out of the heat exchange tubes, secondary air flows out of the heat exchange tubes, and the fins are used for increasing the contact area between air and spray water and strengthening heat and mass exchange between the air and the water. The air to be processed in the heat exchange tube of the evaporative heat exchanger 11, namely the primary air, enters the heat exchange tube of the evaporative heat exchanger 11, enters the second box body 3 after evaporation heat exchange, sequentially sweeps upwards the heat dissipation filler 26, the water baffle 28 and the air cooling heat exchanger 5 of the second box body 3, and finally flows into the atmosphere through the fan 4 on the second box body 3. Air for evaporating moisture outside the heat exchange pipes of the evaporative heat exchanger 11, namely secondary air, respectively enters the corresponding box bodies from the first air inlet grids 23 of the first box body 1 and the third box body 7, then sequentially sweeps upwards the evaporative heat exchanger 11, the heat dissipation filler 26 and the water baffle 28 in the first box body 1 and the third box body 7, and finally flows into the atmosphere through the fans 4 on the first box body 1 and the third box body 7.

As shown in FIG. 1, the drain board 10 is of a herringbone structure and is fixed in the second box 3, and drain ports communicated with the first box 1 and the third box 7 are formed at the two ends of the drain board 10.

As shown in fig. 1, the submersible pump 14 is a variable-frequency submersible pump, the condenser needs different amounts of cooling water under different modes of operation or under different working conditions in the same mode, the design of the variable-frequency submersible pump has the effect of matching with the required amount of the cooling water, and meanwhile, the operation energy consumption of the condenser is reduced, so that the purposes of economy and energy conservation are achieved.

As shown in fig. 1, in the air inlet grilles related to the composite evaporative condenser of the present invention, the first air inlet grilles 23 on the first box 1 and the third box 7 are non-adjustable fixed air inlet grilles; the second air inlet grid 9 on the second box body 3 is a movable air inlet grid with adjustable opening and closing states. When the condenser operates in the indirect evaporative cooling mode, the second air inlet grid 9 is in a closed state, so that the mixing of outdoor air and cooled primary air in the second box body 3 is prevented, the temperature of the primary air is reduced, and the heat exchange effect on the side of the air-cooled heat exchanger 5 is influenced. Under the operation condition of other modes, the second air inlet grid 9 is in an open state, outdoor air can flow into the second box body 3 from the second air inlet grid 9, then sequentially sweeps upwards the heat dissipation filler 26 and the water baffle 28 in the second box body 3, exchanges heat with the air-cooled heat exchanger 5, and finally flows into the atmosphere through the fan 4 on the second box body.

The condenser of the invention has no external equipment and does not need to be assembled. The surface of the integral box body of the condenser is only provided with an inlet and an outlet of the refrigerant and a water outlet of the cooling water. The refrigeration system piping may be directly connected to the condenser.

As shown in fig. 1, a fifth valve 13 is provided between the water-cooled heat exchanger 17 and the submersible pump 14, and a sixth valve 25 is provided on a connection pipe connecting the air-cooled heat exchanger 5 and the water-cooled heat exchanger 17. A first valve 27 and a second valve 24 are arranged on a branch of the water-cooled heat exchanger 17 connected with the spraying device 6 in the first box body 1; and a third valve 8 and a fourth valve 12 are arranged on a branch of the water-cooling heat exchanger 17 connected with the spraying device 6 in the third box body 7. The switching of the operation modes of the condenser is realized by adjusting the switch states of the first valve 27, the second valve 24, the third valve 8, the fourth valve 12, the fifth valve 13, the sixth valve 25 and the second air inlet grid 9.

The composite evaporative condenser can be operated in an operation mode with high energy efficiency ratio selected from three operation modes according to different operation working conditions. The three related operation modes are respectively an air cooling mode, a direct evaporative cooling mode and an indirect evaporative cooling mode.

Air cooling mode: when the temperature difference between the ambient air dry bulb temperature and the condensing temperature can satisfy the condensing load, the condenser related to the invention can run in a dry mode without water circulation, namely an air cooling mode. In specific implementation, the water in the condenser is completely drained through the water outlet 21 of the water collecting tank 22 and the water outlet 16 of the water-cooled heat exchanger 17, so that the water is prevented from freezing in the condenser. The second air inlet grid 9 on the second box body 3 is in an open state, so that enough low-temperature air enters the second box body 3. The fans on the first box body 1 and the third box body 7 are shut down, and only the fan on the second box body 3 is operated. In this case, the air cooling mode is adopted, and the condenser only needs one fan for power consumption.

Direct evaporative cooling mode: when the temperature difference between the ambient air wet bulb temperature and the condensing temperature can satisfy the condensing load, the condenser operates in a direct evaporative cooling mode. In specific implementation, the first valve 27 and the third valve 8 in the spraying system are closed, the second valve 24, the fourth valve 12 and the fifth valve 13 are opened, the spraying in the first box 1 and the third box 7 is stopped, and only the spraying in the second box 3 is carried out. The second air inlet grid 9 on the second box 3 is in an open state, and at this time, air entering the second box 3 from the second air inlet grid 9 and air flowing into the evaporative heat exchangers 11 in the first box 1 and the third box 7 enter. The fans on the first box body 1 and the third box body 7 are shut down, and only the fan on the second box body 3 is operated. At the moment, the spray water and the air flowing in from the second air inlet grid 9 perform heat and mass exchange on the heat dissipation filler in the second box body 3, the temperature is reduced in an enthalpy manner, the cooling air with the temperature close to the wet bulb temperature of the ambient air performs heat exchange with the refrigerant in the air-cooled heat exchanger 5 upwards, and the cooling water with the temperature close to the wet bulb temperature of the ambient air in the water collection tank 22 flows into the water-cooled heat exchanger 17 to cool the refrigerant again to achieve supercooling. The process is in a direct evaporative cooling mode, and for the condenser, the power consumption equipment comprises a submersible pump and a fan.

Indirect evaporative cooling mode: when the temperature difference between the approximate dew point temperature of the ambient air (the temperature between the wet bulb temperature and the dew point temperature of the ambient air is named as the approximate dew point temperature) and the condensation temperature can meet the condensation load, the condenser operates in the indirect evaporative cooling mode. In specific implementation, all valves in the spraying system are in an open state. The second air inlet 9 on the second box 3 is in a closed state, so that the mixing of outdoor air and cooled primary air in the second box is prevented, the primary air temperature is reduced, and the heat exchange effect on the side of the air-cooled heat exchanger 5 is influenced. Fans on the first box body 1, the second box body 3 and the third box body 7 are all in an opening state. At this time, the spray water of the first box 1 and the third box 7 is cooled by the heat dissipation filler 26, and then contacts with the secondary air to cool the primary air in the evaporative heat exchanger at equal humidity, and then the primary air flows into the second box 3, and on the heat dissipation filler of the second box 3, the heat and mass exchange is performed with the spray water in the second box 3, and the isenthalpic cooling is performed. The primary air close to the dew point temperature of the ambient air exchanges heat with the refrigerant in the air-cooled heat exchanger 5 upwards, and the cooling water close to the wet bulb temperature of the ambient air in the water collection tank 22 flows into the water-cooled heat exchanger 17 to cool the refrigerant again to achieve supercooling. The process is an indirect evaporative cooling mode, and for the condenser, the power consumption equipment comprises a submersible pump and three fans.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the scope of the present invention, which is defined by the appended claims.

Claims

1. A compound evaporative condenser comprising: fan, breakwater, air-cooled heat exchanger, spray set, heat dissipation filler, evaporation formula heat exchanger, hydrophobic board, header tank, water-cooled heat exchanger and immersible pump, its characterized in that:

the composite evaporative condenser consists of a first box body, a second box body and a third box body, wherein the first box body and the third box body have the same internal structure and are symmetrically arranged on two sides of the second box body; in the first box and the third box: the fan is arranged at the top of the box body, and a water baffle is arranged below the fan; the heat dissipation filler is positioned in the middle of the box body, and the spraying device is positioned between the water baffle and the heat dissipation filler; the water collecting tank is positioned at the bottom of the box body, and the evaporative heat exchanger is positioned between the heat dissipation filler and the water collecting tank; the first air inlet grids are embedded on the front surface and the rear surface of the box body and are positioned between the evaporative heat exchanger and the water collecting tank; the water collecting tanks of the first tank body and the third tank body are communicated with each other through a bottom channel of the second tank body;

in the second box: the fan is positioned at the top of the second box body, and the air-cooled heat exchanger is arranged below the fan; the heat dissipation filler is positioned in the middle of the second box body, a spraying device is arranged above the heat dissipation filler, and the water baffle is positioned between the air-cooled heat exchanger and the spraying device; the water-cooling heat exchanger is positioned at the bottom of the second box body, and a hydrophobic plate is arranged above the water-cooling heat exchanger; the second air inlet grids are embedded in the front surface and the rear surface of the second box body and are positioned between the heat dissipation filler and the drainage plate; the air-cooled heat exchanger is connected with the water-cooled heat exchanger through a connecting pipe; and the spraying devices in the first box body, the second box body and the third box body are communicated and connected with the water-cooling heat exchanger.

2. The composite evaporative condenser, as recited in claim 1, wherein said water-cooled heat exchanger is a spiral plate heat exchanger, which is formed by winding two parallel steel plates to form spiral flow passages spaced apart from each other, and cover plates are welded to the upper and lower surfaces of the heat exchanger, and the cold and hot fluids flow through the two flow passages, respectively, and said water-cooled heat exchanger is provided with a first inlet, a first outlet, a second inlet and a second outlet.

3. The composite evaporative condenser, as recited in claim 2, wherein the refrigerant flows into the air-cooled heat exchanger, is cooled, flows in from the first inlet of the water-cooled heat exchanger through the connecting pipe, and flows out from the first outlet of the water-cooled heat exchanger after being cooled again, thereby completing the overall flow of the refrigerant in the composite evaporative condenser.

4. The composite evaporative condenser as recited in claim 2, wherein the cooling water is driven by the submersible pump to flow into the water-cooled heat exchanger from the second inlet, the cooling water after heat exchange flows out from the second outlet of the water-cooled heat exchanger and then is divided into two branches, which extend upward along the left and right walls of the second tank, and then pass through the walls of the second tank, and then enter the spraying devices of the first tank and the third tank, and then are sprayed out by the nozzle, and then sequentially pass through the heat-dissipating filler and the evaporative heat exchanger under the action of gravity, and then fall into the water-collecting tanks of the first tank and the third tank, respectively;

5. A composite evaporative condenser, as claimed in claim 1, wherein said evaporative heat exchanger is an indirect evaporative cooler; the primary air respectively enters the heat exchange pipes of the evaporative heat exchangers of the first box body and the third box body, enters the second box body after evaporation and heat exchange, sequentially sweeps the heat dissipation filler, the water baffle and the air-cooled heat exchanger of the second box body upwards, and finally flows into the atmosphere through the fan on the second box body.

6. A composite evaporative condenser, as claimed in claim 1, wherein the secondary air enters the first box from the first air inlet grid of the first box and the third box, passes through the evaporative heat exchanger, the heat-dissipating filler and the water baffle plate of the first box and the third box in sequence, and finally flows into the atmosphere through the fans of the first box and the third box.

7. The composite evaporative condenser, as recited in claim 1, wherein said second air inlet grill is a movable air inlet grill which can be opened and closed; when the second air inlet grid is opened, outdoor air enters the second box body from the second air inlet grid, sequentially sweeps upwards the heat dissipation filler, the water baffle and the air-cooled heat exchanger in the second box body, and finally flows into the atmosphere through the fan on the second box body.

8. A composite evaporative condenser, as claimed in claim 1, wherein the air-cooled heat exchanger is a finned heat exchange coil or a light pipe heat exchanger.

9. A composite evaporative condenser, as recited in claim 1, wherein the drain plate has a herringbone structure and is fixed in the second tank, and drain ports communicating with the first tank and the third tank are formed at both ends of the drain plate.

10. A composite evaporative condenser, as set forth in claim 4, wherein a fifth valve is provided between the water-cooled heat exchanger and the submersible pump, and a sixth valve is provided on the connection pipe connecting the air-cooled heat exchanger and the water-cooled heat exchanger; a first valve and a second valve are arranged on a branch of the water-cooled heat exchanger connected with the spraying device in the first box body; a third valve and a fourth valve are arranged on a branch of the water-cooled heat exchanger connected with the spraying device in the third box body; the switching of the operation modes of the composite evaporative condenser is realized by adjusting the switching states of the first valve, the second valve, the third valve, the fourth valve, the fifth valve, the sixth valve and the second air inlet grid.