PRECISION AIR CONDITIONER WITH AN INDIRECT EVAPORATIVE UNIT

Abstract

The present invention relates to a precision air conditioner with an indirect evaporative unit, which comprises a gas-gas heat exchanger, an external circulation fan, an internal circulation fan, a gas filter module, a gas humidification module, an evaporator, a condenser, a condenser fan, a compressor and an air conditioner enclosure. The combination of indirect evaporative cooling and mechanical refrigeration enables indirect evaporative cooling to operate all year round with high air conditioning and refrigeration efficiency. During summer, mechanical refrigeration is used for secondary cooling to achieve the desired temperature. Further, the condenser of the precision air conditioner is upgraded to an indirect evaporative condenser, and the mechanical refrigeration efficiency can be greatly improved.

Description

RELATED APPLICATION

The present application claims priority to Chinese Patent Application No. 201711379371.5, filed on Dec. 20, 2017, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to the technical field of precision air conditioners, and more particularly to a precision air conditioner with an indirect evaporative unit for a data center.

BACKGROUND OF THE INVENTION

After decades of development, the precision air conditioner technology is mature in all aspects. Due to its ease of use, simple operation and high reliability, the precision air conditioner is widely used in small and medium data centers and other applications where the temperature and humidity requirements are relatively strict. The main problem of the products is the low coefficient of performance (COP), which will lead to a narrower application of such products if no revolutionary innovation is made.

The cooling and refrigeration are required for the data centers throughout the year. Generally, the standard temperature and humidity for the data centers are set at 23±1° C. and 50±10%, respectively. The hot air generated from the data center is at a temperature of 35-44° C. Meanwhile, the highest wet bulb temperature is under 30° C. in China. Thus, it is possible to cool the data center using the exterior low temperature cold source by means of ventilation or heat exchange. From this point of view, it can be seen that the exterior cold source can be theoretically used to cool the hot air exhausted from the server throughout the year. However, in practice, the use of exterior cold sources cannot be maintained for a whole year, either by direct use of fresh air or the use of indirect evaporative cooling alone.

In the case where precision air conditioner is utilized alone, only a low COP can be obtained. In the case where fresh air is utilized alone, conventional treatment methods may not achieve the expected results due to poor domestic air quality. Further, fresh air can only be utilized for a relatively short period of time. The indirect evaporative cooling may extend the time period when the exterior cold sources is utilized. In much of northern China, compressors are used for mechanical refrigeration in less than three months a year. However, there are still many problems with the way it combines with a traditional air conditioner.

Due to the poor domestic air quality, indirect evaporative cooling equipment that normally operates in foreign countries will encounter a lot of troubles in China. For example, dust removal and heat exchanger cleaning require manual treatment, which not only brings a lot of manual work but also cause the equipment to change from working state to the maintenance state.

SUMMARY OF THE INVENTION

Based on the above technical problems, provided is a new precision air conditioner with an indirect evaporative unit, which can make the indirect evaporative cooling working all year round and achieve high coefficient of performance by combining indirect evaporative cooling technology and mechanical refrigeration technology. In summer, the precision air conditioner only needs mechanical refrigeration as a secondary cooling to achieve the desired temperature. Further, in such precision air conditioner, the condenser of the precision air conditioner is upgraded to an indirect evaporative condenser, and the mechanical refrigeration efficiency can be greatly improved.

The technical solution of the present invention will be described as follows.

A precision air conditioner with an indirect evaporative unit comprising: a gas-gas heat exchanger, an external circulation fan, an internal circulation fan, a gas filter module, a gas humidification module, an evaporator, a condenser, a condenser fan, a compressor, an air conditioner enclosure.

The gas-gas heat exchanger is provided with a heat exchanger internal circulation air inlet, a heat exchanger internal circulation air outlet, a heat exchanger external circulation air inlet, a heat exchanger external circulation air outlet, a heat exchanger internal circulation passage, and a heat exchanger external circulation passage, heat exchanger plates. The gas-gas heat exchanger is a type of gas-gas heat exchanger having dividing walls. The heat exchanger plates are arranged to be spaced to form the heat exchanger internal circulation passage and the heat exchanger external circulation passage. Heat is transferred between external air and internal air through the heat exchanger plates of the gas-gas heat exchanger.

The air conditioner enclosure is arranged around the precision air conditioner with an indirect evaporative unit. The air conditioner enclosure is provided with an internal circulation air inlet, an internal circulation air exhaust passage, an external circulation air inlet, an external circulation air intake passage, and an external circulation air exhaust passage.

The internal circulation air inlet is connected to the heat exchanger internal circulation air inlet, and the external circulation air intake passage is connected to the heat exchanger external circulation air inlet.

The external circulation fan is arranged above the gas-gas heat exchanger.

The internal circulation fan is arranged below the gas-gas heat exchanger.

The gas filter module, which is connected with the external circulation air inlet, is arranged in the external circulation air intake passage. The gas filter module is arranged perpendicularly or substantially perpendicularly.

The gas humidification module is arranged between the gas filter module and the gas-gas heat exchanger.

The evaporator is arranged in the internal circulation air exhaust passage below the gas-gas heat exchanger.

The condenser is arranged below or above the external circulation air intake passage and communicates with the external circulation air intake passage.

The condenser fan is arranged below or above the condenser.

The compressor is connected to the evaporator and the condenser.

The precision air conditioner with an indirect evaporative unit has a complete external air circulation as follows. The external air goes through the gas filter module and enters the external circulation air intake passage, and then enters the heat exchanger external circulation passage after being humidified by the gas humidification module. Heat is transferred between the external air and the internal air flowing in the heat exchanger internal circulation passage through the heat exchanger plates, and then the external air enters the external circulation air exhaust passage, and then is exhausted to the exterior by the external circulation fan.

The precision air conditioner with an indirect evaporative unit has a complete internal air circulation as follows. The internal air enters the heat changer internal circulation passage from the internal circulation air inlet. Heat is transferred between the internal air and the external air flowing in the heat exchanger external circulation passage through the heat exchanger plates. The internal air goes through the evaporator and then is cooled. The internal air then enters the internal circulation air exhaust passage, and then is exhausted to the interior by the internal circulation fan.

The precision air conditioner with an indirect evaporative unit has a complete condenser cooling gas-circulation as follows. The external air goes through the gas filter module and enters the external circulation air intake passage, and then enters the condenser after being humidified by the humidification module. Heat is transferred between the external air and the condenser, and then the external air is exhausted to the exterior by the condenser fan.

In another embodiment, the gas-gas heat exchanger is a cuboid having a rectangular cross section. The heat exchanger external circulation air outlet is arranged on the top of the gas-gas heat exchanger. The heat exchanger internal circulation air outlet is arranged on the bottom of the gas-gas heat exchanger. The heat exchanger external circulation air inlet is arranged at the bottom-right corner of the gas-gas heat exchanger. The heat exchanger internal circulation air inlet is arranged at the top-left corner of the gas-gas heat exchanger.

In another embodiment, the gas-gas heat exchanger has a hexagonal cross section. The heat exchanger employs a counter-flow arrangement in the middle portion and a cross-flow arrangement at the inlet or outlet for the external air and the internal air.

In another embodiment, the gas-gas heat exchanger has a pentagonal cross section. The heat exchanger employs a counter-flow arrangement in the middle portion and a cross-flow arrangement at the inlet or outlet for the external air and the internal air.

In another embodiment, the gas-gas heat exchanger has a cross section of a combination of two quadrangles. The heat exchanger employs a cross-flow arrangement in the middle portion and at the inlet or outlet for the external air and the internal air.

In another embodiment, a cleaning nozzle to spray liquid is arranged inside the heat exchanger.

In another embodiment, the gas filter module comprises an automatic dust removal assembly for periodically removing dust from a filter screen.

In another embodiment, the gas humidification module further comprises a variable-frequency water pump, wherein water pressure is adjusted by adjusting working load of the variable-frequency water pump during the operation of the air conditioning system. The gas humidification module further comprises a plurality of sets of nozzles, each of which corresponds to a specific start-up pressure. The nozzle will work when the pressure is greater than or equal to the start-up pressure of the corresponding nozzle.

In another embodiment, the external circulation air exhaust passage of the air conditioner enclosure is curved, and the external circulation air is distributed to both sides of the air conditioner enclosure and exhausted to the exterior.

In another embodiment, the internal circulation fan and the external circulation fan are centrifugal electronically commutated fans. The flow direction changes by 90 degrees or nearly 90 degrees after the air passes through the fan.

The present invention has the following advantages.

The present invention provides a new apparatus by combining two ways of cooling, including mechanical refrigeration and indirect evaporative cooling. The apparatus may cool the air exhausted from the server by means of indirect evaporative cooling in spring, autumn and winter. In summer, indirect evaporative cooling is employed for preliminary cooling, and mechanical cooling is employed to cool the air if the air does not reach the expected 23° C., thus saving energy. It would be possible for the data centers in most of the area north of the Yangtze River in China that the compressor runs no more than 3 months, which will greatly improve the energy efficiency throughout the year. In addition, in summer when the variable-frequency compressor operates, the mechanical refrigeration efficiency may be greatly improved due to the low-load operation of the compressor and the use of indirect evaporative condenser. The present invention provides a design of a new gas-gas heat exchanger with automatic cleaning function. The present invention further provides a design of an automatic dust removal device, which can adapt to the windy and dusty natural environment of the North of China.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a precision air conditioner with an indirect evaporative unit according to an embodiment of the present invention.

FIG. 2 is a perspective view of the gas-gas heat exchanger shown in FIG. 1.

FIG. 3 shows a cross-section of a gas-gas heat exchanger.

FIG. 4 shows another shape of the cross-section of the gas-gas heat exchanger.

FIG. 5 shows another shape of the cross-section of the gas-gas heat exchanger.

FIG. 6 shows another shape of the cross-section of the gas-gas heat exchanger.

REFERENCE NUMERALS

11-internal circulation air inlet, 12-heat exchanger internal circulation air inlet, 13-heat exchanger internal circulation air outlet, 14-internal circulation air outlet, 21-external circulation air inlet, 22-heat exchanger external circulation air inlet, 23-heat exchanger external circulation air outlet, 24-external circulation air outlet, 31-condenser air inlet, 32-condenser air outlet, 41-external circulation air intake passage, 42-heat exchanger external circulation passage, 43-external circulation air exhaust passage, 44-heat exchanger internal circulation passage, 45-internal circulation air exhaust passage, 46-condenser air exhaust passage; 51-evaporator, 52-condenser, 53-compressor, 54-gas filter module, 55-gas humidification module, 56-gas-gas heat exchanger, 61-internal circulation fan, 62-external circulation fan, 63-condenser fan.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described more fully hereinafter with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention may be made in many different forms and is not limited to the embodiments described herein. These embodiments are provided to explain the disclosure of the invention in detail.

It should be noted that when an element is referred to as being “fixed” to another element, it may refer to that the element is directly arranged on the other element, or that there is an intermediate element arranged between them. When an element is referred to as being “connected” to another element, it may refer to that the element is directly connected to the other element, or that there is an intermediate element arranged between them.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. The terminology is used to describe embodiments in the description, but is not intended to limit the invention.

As shown in FIG. 1, the precision air conditioner with an indirect evaporative unit according to the embodiment of the present invention comprises a gas-gas heat exchanger 56, an internal circulation fan 61, an external circulation fan 62, a gas filter module 54, a gas humidification module 55, an evaporator 51, a condenser 52, a compressor 53, a condenser fan 63, and an air conditioner enclosure in which the entire precision air conditioner is enclosed. The air conditioner further comprises an internal circulation air inlet 11, heat exchanger internal circulation air inlet 12, heat exchanger internal circulation air outlet 13, internal circulation air outlet 14, external circulation air inlet 21, heat exchanger external circulation air inlet 22, heat exchanger external circulation air outlet 23, external circulation air outlet 24, condenser air inlet 31, and condenser air outlet 32. The internal circulation fan 61 is arranged below the heat exchanger 56, and the external circulation fan 62 is arranged above the heat exchanger 56. The condenser fan 63 is arranged above or below the condenser 52 and communicates with the external circulation air intake passage 41. The internal air enters the precision air conditioner from the internal circulation air inlet 11, and is exhausted to the interior from the internal circulation air outlet 14. The external air enters the precision air conditioner from the external circulation air inlet 21, and is exhausted to the exterior from the external circulation air outlet 24 and condenser air outlet 32.

In this embodiment, the external air refers to air that enters the exterior through the external circulation air inlet, and the internal air refers to air that enters the interior through the internal circulation air inlet.

In this embodiment, a complete external air circulation is as follows. The external air is filtered by the gas filter module 54 and humidified by the gas humidification module 55 and then enters the external circulation air intake passage 41. Subsequently, the external air enters the heat exchanger external circulation passage 42 in the gas-gas heat exchanger 56. Heat is transferred to the internal air through the wall. The external air then enters the external circulation air exhaust passage 43 and is exhausted to the exterior by the external circulation fan 62.

A complete internal air circulation is as follows. The internal air enters the heat exchanger internal circulation passage 44 in the gas-gas heat exchanger 56 from the internal circulation air inlet 11. Heat is transferred to the external air through the wall. The internal air is cooled by the evaporator 51 and then enters the internal circulation air exhaust passage 45 and is exhausted to the interior by the internal circulation fan 61.

The gas-gas heat exchanger 56 is a type of gas-gas heat exchanger having dividing walls, in which the heat exchanger external circulation passage 42 and the heat exchanger internal circulation passage 44 are completely separated by the heat exchange plates of the gas-gas heat exchanger 56, such that heat is transferred between the external air and the internal air through the heat exchange plates.

A complete condenser cooling gas-circulation is as follows. The external air is filtered by the gas filter module 54 and humidified by the gas humidification module 55 and then enters the external circulation air intake passage 41. Subsequently, the external air enters the condenser 52, such that heat is transferred to the condenser. The external air enters the condenser air exhaust passage 46 and is then exhausted to the exterior by the condenser fan 63. Generally, after the exterior air passes through the gas humidification module 55, its temperature is lowered to become low temperature exterior air, so that the operating temperature of the condenser according to the embodiment is lower than the temperature of the exterior air, resulting in a higher cooling efficiency of mechanical refrigeration.

As shown in FIG. 2, the gas-gas heat exchanger 56 is a type of gas-gas heat exchanger having dividing walls, and includes heat exchanger plates, a heat exchanger external circulation air inlet 22, a heat exchanger external circulation air outlet 23, a heat exchanger internal circulation air inlet 12 and heat exchanger internal circulation air outlet 13, wherein the heat exchanger external circulation passage 42 and the heat exchanger internal circulation passage 44 are spaced and formed by the heat exchanger plates arranged to be spaced. It is further provided with air inlet and outlet. The internal air goes through the heat exchanger internal circulation passage 44 in the heat exchanger, entering from the heat exchanger internal circulation air inlet 12 and exiting from the heat exchanger internal circulation air outlet 13. The external air goes through the heat exchanger external circulation passage 42 in the heat exchanger, entering from the heat exchanger external circulation air inlet 22 and exiting from the heat exchanger external circulation air outlet 23.

In an instance, temperature of the internal circulation return air for a data center employing the present precision air conditioner is 35° C., while temperature of the supply air should be controlled at 23° C. indoors. In summer, when temperature of the external air is 37° C. and the relative humidity is 50% (the wet bulb temperature is 28° C.), the use of indirect evaporative cooling alone may not cool the inner circulation return air to the expected 23° C. Therefore, it is necessary to operate the compressor for secondary cooling. The specific working process is as follows. When entering the external circulation passage of the precision air conditioner, the external air is humidified through the gas humidification module and achieves a relative humidity approximate to 100% and a gas temperature approximate to 28° C. After passing through the gas-gas heat exchanger, temperature of the external air rises to 34.3° C. In the internal circulation, the internal air at 35° C. is cooled to 28.7° C. after passing through the gas-gas heat exchanger, and then further cooled to 23° C. by the evaporator. In such process, the relative cooling capacity is approximately (35° C.-28.7° C.)/(35° C.-23° C.)=52.5%, that is, indirect evaporative cooling accounts for 52.5% of the total cooling load of this data center. Therefore, mechanical refrigeration needs to provide only 47.5% of the cooling capacity. The energy efficiency of a compressor operating under these conditions is much higher than its energy efficiency at full load. Alternatively, when temperature of the external air is 30° C. and the relative humidity is 40% (the wet bulb temperature is 20° C.), the external air is humidified through the gas humidification module and achieves a relative humidity approximate to 100% and a gas temperature approximate to 20° C. After passing through the gas-gas heat exchanger, temperature of the external air rises to 33.5° C. The internal air at 35° C. is cooled to 21.5° C. after passing through the gas-gas heat exchanger. In this case, the indirect evaporative cooling satisfies the cooling requirement of the internal air, so that it is not necessary to operate the compressor.

The present invention provides a new apparatus by combining two ways of cooling, including mechanical refrigeration and indirect evaporative cooling. The apparatus may cool the air exhausted from the server by means of indirect evaporative cooling in spring, autumn and winter. In summer, indirect evaporative cooling is employed for preliminary cooling, and mechanical cooling is employed to cool the air if the air does not reach the expected 23° C., thus saving energy. It would be possible for the data centers in most of the area north of the Yangtze River in China that the compressor runs no more than 3 months, which will greatly improve the energy efficiency throughout the year. In addition, in summer when the variable-frequency compressor operates, the mechanical refrigeration efficiency may be greatly improved due to the low-load operation of the compressor and the use of indirect evaporative condenser.

In one embodiment, as shown in FIG. 1, heat exchanger external circulation air inlet 22, heat exchanger external circulation air outlet 23, heat exchanger internal circulation air inlet 12, heat exchanger internal circulation air outlet 13 are respectively arranged at the bottom-right corner, upper side, at the top-left corner and lower side of the gas-gas heat exchanger 56. In other embodiments, the inlet and outlet for the internal air and the external air may be arranged elsewhere, as long as the internal air and the external air flow in a counter-flow manner inside the gas-gas heat exchanger 56. The so-called counter-flow manner means that the heat exchanger internal circulation passage 44 and the heat exchanger external circulation passage 42 are arranged parallel to each other.

In the present invention, the gas-gas heat exchanger 56 may have other shapes as shown in FIGS. 3, 4, 5, and 6. It comprises heat exchanger plates, heat exchanger external circulation air inlet 22, heat exchanger external circulation air outlet 23, heat exchanger internal circulation air inlet 12, heat exchanger internal circulation air outlet 13, heat exchanger external circulation passage 42 and heat exchanger internal circulation passage 44.

The gas-gas heat exchanger shown in FIG. 3 is a cuboid having a rectangular cross section, wherein the heat exchanger external circulation passage 42 and heat exchanger internal circulation passage 44 are arranged in a counter-flow manner inside the heat exchanger, and are arranged in a cross-flow manner at the inlet or outlet.

As shown in FIGS. 4 and 5, the gas-gas heat exchanger has a hexagonal or a hexagonal cross section, wherein the heat exchanger external circulation passage 42 and heat exchanger internal circulation passage 44 are arranged in a counter-flow manner inside the heat exchanger, and are arranged in a cross-flow manner at the inlet or outlet.

As shown in FIG. 6, the gas-gas heat exchanger has a cross section of a combination of two quadrangles, wherein the heat exchanger external circulation passage 42 and heat exchanger internal circulation passage 44 are arranged in a cross-flow manner inside the heat exchanger, and are arranged in a cross-flow manner at the inlet or outlet.

Preferably, the gas-gas heat exchanger 56 comprises a cleaning nozzle to spray liquid, by which the interior of the heat exchanger 56 can be periodically cleaned to prevent clogging of the heat exchanger external circulation passage.

Preferably, the gas filter module 54 further comprises an automatic dust removal assembly for periodically removing dust from the filter screen, by which the gas filter module can be dusted periodically without manually changing the filter.

Preferably, the gas humidification module 55 further comprises a variable-frequency water pump, wherein the water pressure is adjusted by adjusting working load of the variable-frequency water pump during the operation of the air conditioning system. The gas humidification module further comprises a plurality of sets of nozzles, each of which corresponds to a specific start-up pressure. The nozzle will work when the pressure is greater than or equal to the start-up pressure of the corresponding nozzle. With the plurality of sets of nozzles, the nozzles may work normally in a wide range of water pressure.

Preferably, the external circulation air exhaust passage 43 of the air conditioner enclosure is curved, and the external circulation air is distributed to both sides of the apparatus and exhausted to the exterior.

Preferably, the compressor 53 is a variable-frequency compressor, and the amount of compression can be changed by controlling the frequency of the compressor, thereby achieving precise control of the cooling capacity and low-load operation of the compressor.

Preferably, both the internal circulation fan 61 and the external circulation fan 63 are centrifugal electronically commutated fans. The flow direction changes by 90 degrees or nearly 90 degrees after the air passes through the fan. The nearly 90 degrees turn of the airflow makes the entire precision air conditioner more compact and space saving.

Any combinations of the technical features of the above embodiments may be allowable. All combinations of the technical features of the above embodiments will not described in detail. However, as long as there is no contradiction in the combination of these technical features, it is considered to be within the scope of the invention.

It should be noted that the above embodiments are only used to explain the preferred technical solutions of the present invention, and are not limited thereto. Although the present invention is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the modifications or equivalent substitutions of the present invention are not intended to be excluded from the scope of the invention.

Claims

1. A precision air conditioner with an indirect evaporative unit, comprising:

a gas-gas heat exchanger, an external circulation fan, an internal circulation fan, a gas filter module, a gas humidification module, an evaporator, a condenser, a condenser fan, a compressor, an air conditioner enclosure;

wherein the gas-gas heat exchanger is provided with a heat exchanger internal circulation air inlet, a heat exchanger internal circulation air outlet, a heat exchanger external circulation air inlet, a heat exchanger external circulation air outlet, a heat exchanger internal circulation passage, and a heat exchanger external circulation passage and heat exchanger plates; the gas-gas heat exchanger is a type of gas-gas heat exchanger having dividing walls, and the heat exchanger plates are arranged to be spaced to form the heat exchanger internal circulation passage and the heat exchanger external circulation passage; heat is transferred between external air and internal air through the heat exchanger plates of the gas-gas heat exchanger;

wherein the air conditioner enclosure is arranged around the precision air conditioner with an indirect evaporative unit; the air conditioner enclosure is provided with an internal circulation air inlet, an internal circulation air exhaust passage, an external circulation air inlet, an external circulation air intake passage and an external circulation air exhaust passage;

wherein the internal circulation air inlet is connected to the heat exchanger internal circulation air inlet, and the external circulation air intake passage is connected to the heat exchanger external circulation air inlet;

wherein the external circulation fan is arranged above the gas-gas heat exchanger;

wherein the internal circulation fan is arranged below the gas-gas heat exchanger;

wherein the gas filter module, which is connected with the external circulation air inlet, is arranged in the external circulation air intake passage; the gas filter module is arranged perpendicularly or substantially perpendicularly;

wherein the gas humidification module is arranged between the gas filter module and the gas-gas heat exchanger;

wherein the evaporator is arranged in the internal circulation air exhaust passage below the gas-gas heat exchanger;

wherein the condenser is arranged below or above the external circulation air intake passage and communicates with the external circulation air intake passage;

wherein the condenser fan is arranged below or above the condenser;

wherein the compressor is connected to the evaporator and the condenser,

wherein the precision air conditioner has a complete external air circulation as follows: the external air goes through the gas filter module and enters the external circulation air intake passage, and then enters the heat exchanger external circulation passage after being humidified by the gas humidification module; heat is transferred between the external air and the internal air flowing in the heat exchanger internal circulation passage through the heat exchanger plates, and then the external air enters the external circulation air exhaust passage, and then is exhausted to the exterior by the external circulation fan;

wherein the precision air conditioner has a complete internal air circulation as follows: the internal air enters the heat changer internal circulation passage from the internal circulation air inlet; heat is transferred between the internal air and the external air flowing in the heat exchanger external circulation passage through the heat exchanger plates; the internal air goes through the evaporator and then is cooled; the internal air then enters the internal circulation air exhaust passage, and then is exhausted to the interior by the internal circulation fan;

wherein the precision air conditioner has a complete condenser cooling gas-circulation as follows: the external air goes through the gas filter module and enters the external circulation air intake passage, and then enters the condenser after being humidified by the humidification module; heat is transferred between the external air and the condenser, and then the external air is exhausted to the exterior by the condenser fan.

2. The precision air conditioner with an indirect evaporative unit according to claim 1,

wherein the gas-gas heat exchanger is a cuboid having a rectangular cross section; and

wherein the heat exchanger external circulation air outlet is arranged on the top of the gas-gas heat exchanger, the heat exchanger internal circulation air outlet is arranged on the bottom of the gas-gas heat exchanger, the heat exchanger external circulation air inlet is arranged at the bottom-right corner of the gas-gas heat exchanger, and the heat exchanger internal circulation air inlet is arranged at the top-left corner of the gas-gas heat exchanger.

3. The precision air conditioner with an indirect evaporative unit according to claim 1,

wherein the gas-gas heat exchanger has a hexagonal cross section; and

wherein the gas-gas heat exchanger employs a counter-flow arrangement in the middle portion and a cross-flow arrangement at the inlet or outlet for the external air and the internal air.

4. The precision air conditioner with an indirect evaporative unit according to claim 1,

wherein the gas-gas heat exchanger has a pentagonal cross section; and

wherein the gas-gas heat exchanger employs a counter-flow arrangement in the middle portion and a cross-flow arrangement at the inlet or outlet for the external air and the internal air.

5. The precision air conditioner with an indirect evaporative unit according to claim 1,

wherein the gas-gas heat exchanger has a cross section of a combination of two quadrangles; and

wherein the gas-gas heat exchanger employs a cross-flow arrangement in the middle portion and at the inlet or outlet for the external air and the internal air.

6. The precision air conditioner with an indirect evaporative unit according to claim 1, wherein a cleaning nozzle to spray liquid is arranged inside the gas-gas heat exchanger.

7. The precision air conditioner with an indirect evaporative unit according to claim 1, wherein the gas filter module comprises an automatic dust removal assembly for periodically removing dust from a filter screen.

8. The precision air conditioner with an indirect evaporative unit according to claim 1,

wherein the gas humidification module further comprises a variable-frequency water pump, and water pressure is adjusted by adjusting working load of the variable-frequency water pump during the operation of an air conditioning system;

wherein the gas humidification module further comprises a plurality of sets of nozzles, each of which corresponds to a specific start-up pressure, and the nozzle will work when the pressure is greater than or equal to the start-up pressure of the corresponding nozzle.

9. The precision air conditioner with an indirect evaporative unit according to claim 1, wherein the external circulation air exhaust passage of the air conditioner enclosure is curved, and the external circulation air is distributed to both sides of the air conditioner enclosure and exhausted to exterior.

10. The precision air conditioner with an indirect evaporative unit according to claim 1,

wherein the internal circulation fan and the external circulation fan are centrifugal electronically commutated fans; and

wherein flow direction changes by 90 degrees or nearly 90 degrees after the air passes through the fan.