JP2014129912A - Air conditioner using direct expansion coils - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner using only direct expansion coils, and capable of detecting an evaporation pressure of refrigerant flowing back to a compressor, and controlling a compression pressure of the compressor based on the value of the evaporation pressure.SOLUTION: An air conditioner using direct expansion coils into which outdoor air is introduced and that cool or heat the outdoor air, controls a cooling temperature of the direct expansion coils by providing a control system based on detection of a room temperature as well as a control system detecting an evaporation pressure of refrigerant flowing back to a compressor and controlling a compression pressure of the compressor on the basis of a value of the detected evaporation pressure, allowing a selection circuit to select signals of these control systems to control the compression pressure of the compressor, and by always circulating the refrigerant in the direct expansion coils in an unfrozen temperature range.

Description

  The present invention relates to an air conditioner that uses a plurality of directly expanded coils, and more particularly to a series of two directly expanded coils that are arranged in parallel, each of which is a directly expanded coil that realizes energy saving. The present invention relates to an air conditioner using

Conventionally, the heat medium (refrigerant) of an air conditioner using a water coil is cold water, hot water, steam, or the like, but the heat medium of the refrigerant coil of the air conditioner of a direct expansion coil is a refrigerant other than water.
Conventionally, strict air conditioning management is required in clean rooms, but normally, the allowable range of set temperature and humidity is controlled within ± 3 ° C. for temperature and within 10% for humidity.
By the way, the heat medium of the air conditioner using a water coil is cold water, hot water, steam, etc., and the heat medium of the refrigerant coil of the air conditioner of the direct expansion coil is a refrigerant, but as described below, There are advantages and disadvantages.

The basic air conditioning system using a water coil in a clean room is as shown in FIG. 1, but the air OA from the outside is heat-exchanged by controlling the cold water coil a with a valve i, and the target is roughly Air supply SA obtained by cooling (heating) below temperature and humidity and finely adjusting with reheat coil b and humidifier c is obtained.
The air state change in this case will be described with reference to the air diagram of FIG. 2. When the outside air OA is in the state of point A in FIG. 2, the water coil a is connected to the refrigerator h or Cold water (hot water, steam) is supplied from the chiller, and by controlling the valve d, the dew point temperature where the coil outlet air temperature is set, in fact, the dew point temperature setting value is lower than the target absolute humidity with a margin The temperature is lowered to (until the target absolute humidity line in FIG. 2) and the process moves to point B.
Thereafter, hot water or steam at a high temperature is controlled by the valve f by the boiler e and supplied to the reheating coil b, reheated from the dew point temperature to a humidifiable temperature, and the air temperature is raised to the point C in FIG. Further, the steam from the boiler e is sprayed from the humidifier c to reach the final target humidity, which is raised to the point D in FIG.

  However, the basic air conditioning system using a conventional water coil as shown in FIG. 1 requires (1) a heat source machine room for installing a heat source device for cooling and reheating, and (2) When considering backup, another system must be installed. (3) Regardless of the number of distributed air conditioners, large heat source equipment operates and it is difficult to reduce the chilled water transport power. 4) There is a problem that the heat source equipment, cold water, reheat coil, and humidification valve control are in different construction categories, and the management items after construction become complicated.

In addition, since the direct expansion coil does not indirectly transfer heat, the cooling and heating efficiency of the direct expansion coil system should exceed that of the water coil. However, since the direct expansion coil is a refrigerant other than water, However, it is difficult to control the pressure and temperature for different phases, and it is difficult to manage fine control.
For example, the basic air conditioning system using a direct expansion coil in a clean room is as shown in FIG. 3, but the use of the water coil a in FIG. The direct expansion coils g1, g2, and g3 are arranged in parallel, and a blower (fan) 1 is arranged downstream. It is difficult to control a wide range of air conditioning with a direct expansion coil. Therefore, three units of the direct expansion coil are arranged in parallel, one unit is operated when the load is low, and all units are operated when the load is high. Is possible.

The air state change in this case will be described with reference to the air diagram of FIG. 2 and the system of FIG. 3 will be described. When the outside air OA is in the state of point A in FIG. Operate all units k1, k2, and k3, and set the coil outlet air temperature and humidity of the direct expansion coils g1, g2, and g3 below the set dew point temperature, and set the dew point temperature to a dew point temperature that is lower than the target absolute humidity with a margin. , Move to point B.
After that, as with the water coil air conditioner, hot water or steam is controlled by the valve e by the boiler e, supplied to the reheating coil b, reheated from the dew point temperature to the humidifiable temperature, and the air temperature is shown in FIG. To C point. Further, the steam from the boiler e is sprayed from the humidifier c to reach the final target humidity, which is raised to the point D in FIG.

However, the basic air conditioning system using a direct expansion coil as shown in FIG. 3 is: (1) Since the direct expansion coil is installed in parallel, it is difficult to stop the outdoor unit due to the load, considering the dehumidification capacity. Cannot handle during operation, maintenance or failure. For example, in the air diagram of FIG. 4, when the direct expansion coils g2 and g3 are stopped and in a bypass state, and only the direct expansion coil g1 is operating, the outlet air temperature and humidity of the direct expansion coil g1 is Although the point B is reached, since the directly expanded coils g2 and g3 are in the bypass state, the air in which these coils are mixed becomes the Bmix point and does not fall below the set dew point temperature. Therefore, it is necessary to always operate all of them.
In addition, (2) since the direct expansion coil outlet temperature is set to be equal to or lower than the target dew point temperature, all outdoor units need to be operated at all times, and the coil outlet air temperature and humidity are considerably lower than the target value at low load. Therefore, since the reheating capability of B → C and the humidification capability of C → D are increased, as a result, energy saving operation is not performed.

  For this reason, the direct expansion coil has a small air conditioner for each room that uses one outdoor unit for each indoor unit such as a home air conditioner that does not require strict control of air temperature and humidity. However, air conditioning equipment with only a direct expansion coil tends to be difficult to be adopted in large factories, etc., and as disclosed in Patent Documents 1 and 2, An air conditioning system has been proposed that can be used in large factories and the like by using it together.

  Therefore, the inventors have disclosed, as Patent Document 3, an air conditioner that uses only a direct expansion coil, which eliminates the need for a heat source device that generates cold water for the water coil, saves space, and enables rotation operation and durability. In addition, it can easily handle backup operation in the event of a failure, and can control temperature and humidity over a wide range in the same way as conventional chilled water coils and parallel arrangements. Reheating coils and humidifiers Air conditioners that can satisfy constant temperature and humidity conditions are installed.

JP 2006-292300 A JP 2008-75978 A Japanese Patent Application No. 2011-202329

The present invention provides an air conditioner that uses only a direct expansion coil to detect the evaporating pressure of the refrigerant returning to the compressor and control the compressing pressure of the compressor based on the value of the evaporating pressure. It is what.
In addition, a heat source device that creates cold water for the water coil is not required, saving space, enabling rotation operation, improving durability, and easily supporting backup operation in the event of a failure. Similar to the arrangement, in addition to the configuration that enables fine control of temperature and humidity over a wide range, the exhaust heat of the refrigeration cycle of the direct expansion coil is used for reheating, realizing energy saving and satisfying constant temperature and humidity conditions It is intended to provide an air conditioner.

In order to solve the above-mentioned problem, the invention of claim 1 is arranged such that two groups of directly expanded coils that are introduced into the outside air and cooled or heated by a refrigerant are arranged in series, and a plurality of upstream first directly expanded coils are arranged in parallel. In the air conditioner in which a plurality of downstream second direct expansion coils are further arranged in parallel,
The downstream second direct expansion coil group can be controlled independently, detects the evaporation pressure of the refrigerant returning to the compressor, controls the compression pressure of the compressor based on the detected evaporation pressure value, and the direct expansion coil In addition to controlling the cooling temperature at room temperature, a control system based on detection of room temperature is also provided, the compression pressure is controlled by selecting signals from these control systems with a selection circuit, and the direct expansion coil is always above the non-freezing range The air conditioner using the direct expansion coil is characterized in that the cooling temperature in the direct expansion coil is controlled so as to circulate with the refrigerant.
According to a second aspect of the present invention, in the air conditioner using the direct expansion coil according to the first aspect, the second direct expansion coil group includes three or four direct expansion coils arranged in parallel. .
According to a third aspect of the present invention, in the air conditioner using the direct expansion coil according to the first or second aspect, a blower also serving as an air supply is interposed between the first direct expansion coil group and the second direct expansion coil group. Characterized by the arrangement.

  According to the air conditioner using the direct expansion coil of the present invention, (1) the evaporating pressure of the refrigerant returning to the compressor is detected, and the compressing pressure of the compressor is controlled by the detected evaporating pressure value. Fine control is also possible in the direct expansion coil, and since the direct expansion coil does not indirectly transfer heat, the cooling / heating efficiency of the system of the direct expansion coil exceeds that of the water coil, and energy saving operation is possible. (2) When operating the compressor, in addition to a control system that controls the compression pressure of the compressor based on the value of the evaporation pressure, a control system that detects the room temperature is also provided, and signals from these control systems are selected by a selection circuit. Thus, the compression pressure is controlled, and the cooling temperature in the direct expansion coil is controlled so that the direct expansion coil 35 always circulates with the refrigerant in the non-freezing region or more, so that a freezing accident can be avoided. (3) In addition to avoiding freezing, by changing the value that limits the evaporation pressure (evaporation temperature) of the direct expansion coil 31, the evaporation temperature is always kept higher than a certain level (see the solid line refrigeration cycle in FIG. 7). High efficiency operation becomes possible. Further, (4) since the coil evaporation temperature can be controlled, in the case of air conditioning where there is a demand for non-condensing operation, the evaporation pressure (evaporation temperature) is kept above the air dew point temperature, that is, the non-condensing coil 31 is not cooled. Condensation operation is also possible.

Further, (5) since the multi-stage (two-stage) parallel direct expansion coil group is further arranged, it becomes possible to control the dew point temperature at which the direct expansion coil outlet temperature is set by fine step number control. In particular, since the second direct expansion coil group 3 is arranged in four stages in parallel in the embodiment, accurate temperature / humidity control can be performed at a position close to the supply air. In addition, the small number of stages control provides a lower energy performance coefficient than the conventional system, and the error of the directly expanded coil outlet air temperature is about ± 3 ° C., so less energy is used for reheating and humidification. Note that this apparatus is also compatible with reheating coils and heat pumps (refrigerants).
In addition, (6) air conditioners using direct expansion coils, unlike conventional air-coil air conditioners, do not require cooling with cold water, so a heat source for producing cold water is not necessary, Only the machine installation space is required, and the machine room of the cold heat source for the water coil is not required.

  Moreover, (7) Rotation operation is possible by combining a parallel-arranged direct expansion coil group and a parallel-arrangement direct expansion coil group in a series of two stages, and the rotation operation enables the direct expansion coil group and the outdoor unit The service life can be extended, and backup operation when some of the direct expansion coils and outdoor units fail can be easily handled. (8) In addition, since a plurality of directly expanded coil groups arranged in parallel are arranged in series in two stages to perform supply air dew point temperature control, after performing rough cooling control on the upstream directly expanded coil group, The temperature and humidity can be finely controlled with a group of directly expanded coils, and a wide range of temperature and humidity control is possible. In addition, the control that satisfies the constant temperature and humidity conditions is possible.

  Further, (9) since the blower 7 also serving as the air supply is disposed between the first direct expansion coil group 2 and the second direct expansion coil group 3, a part of the first direct expansion coil group 2 is stopped. However, the aspirated air is agitated and the cooling is made uniform, and the conditioned air in the same state can be evenly blown to the plurality of downstream second direct expansion coil groups 3. Since almost the same load is applied to the direct expansion coil, there is no bias in operation, the service life can be extended, and there are few failures.

Configuration schematic diagram of conventional air conditioning system using water coil, FIG. 1 and FIG. 3 are air line diagrams for explaining changes in the state of conventional air, Configuration schematic diagram of an air conditioning system in which three conventional direct expansion coils are arranged in parallel, FIG. 3 is an air diagram illustrating problems in the air conditioner of FIG. The schematic diagram of the air conditioner using the direct expansion coil group of the embodiment of the present invention and using the exhaust heat of the direct expansion coil for the reheating coil, An air diagram of the reheating coil of the example, Mollier diagram of the refrigeration cycle of the example, The figure of the graph of the measurement result of the air-conditioning control stability (operating condition) corresponding to the change of the state of the outside air OA in the embodiment, An air diagram illustrating the state of the outside air OA and the operating state of each direct expansion coil in the embodiment, The figure of the graph of the measurement result of the driving | running condition corresponding to the change of the state of the external air OA of an Example, It is explanatory drawing explaining the example of a combination of rotation and backup operation in an Example.

A preferred embodiment of an air conditioner using a direct expansion coil of the present invention will be described with reference to the drawings.
[Example 1]
FIG. 5 is an overall system diagram of the clean room air conditioner 1 using the direct expansion coil according to the embodiment. The outside air OA (from the right side in FIG. 5) is introduced, and the first is cooled upstream by the refrigerant. One direct expansion coil group 2 is arranged, the second direct expansion coil group 3 is arranged downstream, and further, the reheating coil 4, the first humidifier 51 and the second humidifier 52 are arranged downstream thereof. . In addition, although the air conditioner 1 of a present Example is used for a clean room, since a heating apparatus etc. usually exist in a room and raises indoor temperature, it demonstrates by the case where a cooling function is used. In the present invention, “outside air” does not mean only outdoor air, but air that takes in air conditioning from outside the target air conditioner.
The first directly expanded coil group 2 includes three directly expanded coils 21, a directly expanded coil 22, and a directly expanded coil 23 arranged in parallel in three stages against the air flow. The direct expansion coils of the base are connected to the outdoor unit 24 including the compressor 241, the condenser 243, the fan 242, and the like through expansion (control) valves 211 (221, 231), respectively, and are controlled independently.

The second direct expansion coil group 3 is disposed downstream of the first direct expansion coil group 2, and the direct expansion coils 31 to 33, which are three direct expansion coils, are provided with an air flow. Are arranged in three parallel stages, and are operated and controlled independently.
Between the first direct expansion coil group 2 and the second direct expansion coil group 3, a blower (fan) 7 that blows air OA as the supply air SA is disposed, and the blower 7 that also serves as the supply air is the first one. Even if a part of one direct expansion coil group 2 is shut down, the intake air is agitated and the cooling is made uniform, and the conditioned air in the same state is uniformly blown to a plurality of downstream second direct expansion coil groups 3. Is. Therefore, almost the same load is applied to the direct expansion coils 31, 32, 33 of the second direct expansion coil group 3, so that there is no bias in operation, the service period can be lengthened, and there are few failures. The position of the conventional blower (fan) 7 ′ is usually arranged at the most downstream as shown by the dotted line in FIG. 5, and in this case, the direct expansion coils 31, 32 of the second direct expansion coil group 3 are arranged. , 33 has the disadvantage of being sent unbalanced conditioned air.
The four direct expansion coils 31 to 33 of the second direct expansion coil group 3 are independently operated and controlled, and the air conditioning state is finely adjusted downstream of the second direct expansion coil group 3 to achieve the target temperature and humidity. In order to do so, the reheating coil 4, the first humidifier 51 and the second humidifier 52 are provided.

Here, the cooling cycle will be described by taking the direct expansion coil 31 among the plurality of direct expansion coils of the second direct expansion coil group 3 as an example.
The refrigerant that has been cooled by the direct expansion coil 31 is connected to the compressor 35, the condenser 37 that constitutes the outdoor unit 371, and the fan 371. The refrigerant that has been compressed by the compressor 35 and has risen in temperature is exhausted by the condenser 37, The refrigerant exhausted by the condenser 37 is cooled by the expansion valve 38 and circulated through the direct expansion coil 31 to cool the agitated air from the blower 7. The other directly expanded coils 32 and 33 have the same configuration and are independently controlled.
The compressor 35 is normally controlled by the compressor operation control circuit 392 so that the temperature value detected by the room temperature sensor 313 becomes the set temperature, while the pressure sensor 311 and the temperature sensor 312 are This is for controlling the degree of refrigerant superheating of the direct expansion coil 31 to a constant temperature by the operation of the compressor 35 and so as not to be less than or equal to the coil refrigeration zone Y1. The evaporating pressure from the direct expansion coil 31 is directly detected, and this value is input to the central control device 39. The central control device 39 inputs the value to the selection circuit 391 and the detected evaporating pressure value from the direct expansion coil 31 is constant. Or is preferentially selected so as not to be equal to or lower than the coil refrigeration zone Y1, and is input to the compressor operation control circuit 392 to control the drive of the compressor 35.

That is, in order to obtain a driving operation frequency command from the compressor operation control circuit 392 of the compressor 35, a cooling pressure request of the control system via the arithmetic control circuit 393 is obtained from the value of the room temperature sensor 313 which is the dew point temperature center from the room. A signal A and a cooling pressure request signal B when the refrigerant is in the refrigeration region or more in the arithmetic control circuit in the central controller 39 from the value from the pressure sensor 311 that detects the coil evaporation pressure (evaporation temperature) from the direct expansion coil 31; Is selected by the selection circuit 391, and the cooling pressure request signal C that can be cooled in the range where the refrigerant does not fall below the refrigeration region is selected, so that the refrigerant pressure of the compressor 35 is maintained as high as possible to operate with high efficiency operation. As described above, the selection signal C selected by the selection circuit 391 is input to the operation control circuit 392 of the compressor 35, and the direct expansion coil 35 is always circulated by the refrigerant in the non-freezing region or higher. It maintained so that it is possible to avoid freezing accident direct expansion coil 35.
In addition to avoiding the above freezing, by changing the value that limits the evaporation pressure (evaporation temperature) of the direct expansion coil 31, the evaporation temperature is always kept higher than a certain value (see the solid line refrigeration cycle in FIG. 7). Efficient operation is possible.
Further, since the coil evaporation temperature can be controlled, in the case of air conditioning in which there is a demand for non-condensing operation, the evaporating pressure (evaporating temperature) is kept above the air dew point temperature, that is, non-condensing operation of the direct expansion coil 31 to be cooled is also performed. It becomes possible.
A reheating coil 4 and humidifiers 51 and 52 are arranged downstream of the second direct expansion coil group 3. The water in the boiler 6 is heated to produce hot water or steam, and these are expanded (control) valves (valves). The reheating coil 4 is supplied via 421 and heated, and finally the air conditioning state is finely adjusted to a target temperature.
Further, rough humidification is performed by the upstream first humidifier 51 by steam that heats the water in the boiler 6, and the supply air SA is humidified to the final target humidity by the downstream second humidifier 52.

Here, an air diagram as reheating in the cooling cycle in the second directly expanded coil group 3 in the embodiment will be described with reference to FIG.
In the air diagram of FIG. 6, the outside air OA is cooled from the point j to the point k by the first direct expansion coil group 2, and further cooled to the point l by the second direct expansion coil group 3, and then the reheat coil. 4 is heated to room temperature to room temperature. In addition, since the 1st, 2nd humidifiers 51 and 52 operate | move in winter, they do not operate at the time of air_conditioning | cooling in which the 2nd direct expansion coil group 3 etc. operate | move. In this air diagram, the required energy is A1.

Next, the refrigeration cycle of the embodiment will be described with reference to FIG. 7. Conventionally, the evaporating pressure setting and the like from the direct expansion coil 31 have been operated with the same setting after the initial setting. This is because, as mentioned above, the direct expansion coil is a refrigerant other than water, so it is difficult to control the pressure and temperature for different phases such as liquid and gas. As a result, the air condition cannot be controlled precisely, and when the air load such as the air volume changes suddenly, there is a disadvantage that it falls below the freezing zone Y1 shown in the Mollier diagram of FIG. However, it was set so that the saturated vapor line was exceeded with sufficient margin and the refrigerant was transferred to the compressor 35 after it became a complete gas.
That is, the conventional refrigeration cycle is V ′ → X → Y ′ → Z ′ → V ′, and the refrigerant is changed from the compression step (V ′) by the compressor 35 to the condenser 37 and the fan 371 in the condensation step (X). The refrigerant is exhausted and cooled by reducing the pressure in the expansion step (Y ′), and the cooled refrigerant cools the air in the refrigerant step (Z ′) by the direct expansion coil 31, and the refrigerant whose temperature has increased is compressed. Reflux to vessel 35.

On the other hand, the refrigeration cycle of the embodiment is V → X → Y → Z → V indicated by a solid line, and the compression load in the compressor 35 is shortened by Y2 as compared with the conventional dotted refrigeration cycle, and the compression load accordingly. However, the refrigerant is cooled by reducing the pressure from the compression step (V) in the compressor 35 to the condenser 37 in the condensation step (X) and the pressure in the expansion step (Y). The air is cooled in the refrigerant step (Z) by the direct expansion coil 31 with the refrigerant, and the refrigerant returns to the compressor 35.
In the embodiment, the evaporating pressure from the direct expansion coil 31 is directly detected, and the driving of the compressor 35 is controlled by the evaporating pressure detected by the pressure sensor 311, and the cooling process of the solid line refrigeration cycle is performed as necessary. Since it can change arbitrarily to (Z), the air state can be arbitrarily changed within a range Y2 that does not become the refrigeration region Y1 of the coil, and conventionally, the compression start point U ′ in the compressor 35 can be changed. However, since the compression start point U can be arbitrarily changed in the embodiment, it is not necessary to exceed the saturated vapor line unnecessarily, and the refrigeration cycle can be efficiently executed with a minimum value exceeding the saturated vapor line. I can do it.
Thus, in the present embodiment, in the refrigeration cycle in which the direct expansion coil 31 is incorporated, the cooling of the direct expansion coil 31 can be varied by the evaporation pressure of the direct expansion coil 35 within the range of the capacity of the compressor 35.

Here, the experimental results of the above-described configuration in this example will be described.
Example of operation experiment Design air volume: 4000m3 / h (Outside air intake: 20%)
Air supply target: dew points 4.9 ° C DP and 3 ° C DP
Coil combination: in series ... 2 rows Number of stages ... (windward) 3 outdoor units, 3 stages
(Leeward side) 3 outdoor units, 3 stages Generally, the direct expansion coil has a theoretical efficiency that increases as the temperature difference between the high temperature source and the low temperature source is small, and the rated operation is efficient.
Further, as described above, the six direct expansion coils 21, 22, 23, 31, 32, and 33 of this embodiment can be controlled in temperature, and one direct expansion coil is sufficient in a small room. However, in a clean room that air-conditions a large amount of air, it can be dealt with by using a plurality of directly expanded coils.

This will be described with respect to the directly expanded coils 21, 22, 23, 31, 32, 33 of this embodiment. The coils 21, 22, 23 are proportionally controlled with the target of the air enthalpy state at the point k in the air diagram shown in FIG. And the number of stages is controlled. If the outside air OA falls below the point j to the point where the optimum efficiency of the operating refrigerator cannot be maintained, and one of the coils 21, 22, 23 is stopped when the air condition can be lowered to the k-point enthalpy by operating two refrigerators And keep the operating refrigerator efficiency close to the highest point. As described above, one refrigerator can be stopped.
Similarly, when the outside air OA further decreases, the operation shifts to one unit operation. This makes it possible to stop the two refrigerators. When the outside air OA falls below the k-th enthalpy, all three units stop.

On the other hand, the direct expansion coils 31, 32, and 33 are precisely controlled by changing the refrigerator evaporation pressure with the target of the dew point temperature at point i or the dry bulb temperature at point m. By restricting the operation to the non-freezing range, the coil can be prevented from freezing and precise control can be performed.
In the operation in which the freezing limit is not applied, as shown in FIG. 8, a highly accurate operation of ± 0.5 ° C. DP is realized with respect to the target dew point of 4.9 ° C. DP. Even in the state where the freezing limit is added, high precision control of ± 0.7 ° C. DP is realized by avoiding freezing with respect to the target dew point 3 ° C. DP, which is a low dew point impossible with the conventional method. In both cases, re-humidification is not implemented and energy-saving operation is realized.
As with the direct expansion coils 21, 22, and 23, the direct expansion coils 31, 32, and 33 are also stopped in sequence when the capacity of the direct expansion coils 31, 22, and 23 is reduced due to the decrease in the outside air working rate and the refrigerator operation falls below the maximum efficiency point. Go.

In this way, by stopping the refrigerator according to the decrease in the outside air conditions, maintaining the high efficiency operation of the refrigerator, implementing the planned low-tension operation, extending the life of the refrigerator, the operating state Realize easy maintenance.
Backup operation in the event of a refrigeration machine failure can be easily realized by immediately starting the idle refrigeration machine.

[Example 2]
In the above-described rotation operation, the upstream two direct expansion coils 21 and 22 (configuration with the upper two in FIG. 5) and the downstream four direct expansion coils 31, 32, 33, and 34 (FIGS. 9, 10, Next, another embodiment 21, 22, 31, 32, 33, 34 in which one of the dotted lines is added to the three in FIG. 5 will be described. In the air diagram of FIG. In the state of the high temperature and high humidity area A, a high load is required to achieve the target temperature and humidity, and the direct expansion coil is operated. Next, the outside air OA is slightly higher than the high temperature and high humidity area A. In the state of the B region where the humidity is low, since the load is slightly reduced, one of the six units can be rested, and in this embodiment, the direct expansion coil 34 can be stopped. In addition, when stopping the direct expansion coils 33 and 34, the passage of the conditioned air is naturally stopped by a damper or the like.
Further, when the outside air OA is in the C region where the humidity is lower than that in the B region, the load is further reduced. Therefore, any two of the six units can be rested. In this embodiment, the direct expansion coils 33 and 34 are used. Can be stopped.

Similarly, when the outside air OA is in the D region where the humidity and temperature are lower than those in the C region, the load is further reduced. Therefore, any three of the six units can rest, and in this embodiment, the direct expansion coil 32, 33, 34 can be stopped.
Similarly, when the outside air OA is in the E region where the humidity and temperature are lower than those in the D region, the load is also small, so that any four of the six units can be rested. The direct expansion coils 31 to 34 of the expansion coil group 3 are stopped, and only the first direct expansion coil group 2 is operated to realize energy saving.

Referring to FIG. 10 which graphs the measurement result of the operation state in the actual embodiment at this time, FIG. 10 shows the case where the inlet air condition (decreasing enthalpy) in the air conditioner 1 is changed. It is the graph which measured temperature and humidity at an exit.
First, the humidity will be described. The upper side (thin line) in FIG. 10 is a graph relating to the change in humidity. The inlet humidity to the air conditioner 1 is about 90 to 80% and the state of the outside air (inlet) OA is Even if the A-to-E region is changed, the direct expansion coil groups 1 and 2 are switched to the corresponding operating state, and the number of directly-expanded coil operating units is gradually reduced corresponding to the A to E region. It can be seen that the outlet humidity: W is maintained at 50 to 60%.

Next, the temperature will be described. The lower side of FIG. 10 is a graph related to the change in temperature. The inlet temperature of the air conditioner 1 Y decreases from about 33 ° C. to about 18 ° C., and the state of the outside air (inlet) OA is When changing from A to E region, switching according to the operation state of the direct expansion coil, and gradually reducing the number of operation of the direct expansion coil, when the operation of the direct expansion coil is newly stopped by switching the region on the way However, the outlet temperature: Z is still in the range of 10.3-12.6 ° C.
In this way, a part of the direct expansion coil can be stopped outside the high-temperature and high-humidity A region, and if the low tension is assembled, the direct expansion coil and the outdoor unit can be efficiently rested. Rotation operation can be performed to extend the service life of directly expanded coils and outdoor units.

In addition, according to this embodiment, backup operation at the time of failure can be easily handled, and this will be described along with FIG. 11 together with an example of rotation.
In FIG. 11, six fully expanded coils are operated in the high temperature and high humidity A region, but in the C region where the load is reduced, each of the directly expanded coils 21, 22, 31, 32, 33, 34 is Since it can be controlled independently, the two directly expanded coils and the outdoor unit associated with them can be rested. In this case, since each direct expansion coil 21, 22, 31, 32, 33, 34 can be controlled independently, the selection of two units is optional when the capacity is the same. The direct expansion coils 31 and 32 can be rested as described above, and the direct expansion coils 33 and 34 and the outdoor units associated with them can be rested as in the C region operation 2, so that the next C region operation can be performed. 1 and 2 may be operated alternately.

In the normal operation, as shown at both ends of the middle stage in FIG. 11, the linear expansion coils 21 and 22 are operated in the E region and the four linear expansion coils 31 to 34 are stopped in normal operation. However, as shown in the lower ends (a) and (f) of FIG. 11, when the directly expanded coils 21 and 22 have to be stopped due to failure or maintenance, four directly expanded coils 31 to 34 are connected. If it is operated, the normal cooling capacity can be secured.
Similarly, when the direct expansion coils 31 and 32 are rested as in the C region operation 1 in FIG. 11, as shown in the lower part (b) of FIG. If it must be stopped, the normal cooling capacity can be secured by operating four of the direct expansion coils 31 and 32 and the direct expansion coils 21 and 22, and the lower ( As shown in c), when the direct expansion coils 21 and 22 have to be stopped due to failure or maintenance, the normal cooling capacity can be secured by operating four of the direct expansion coils 31 to 34. .

Further, when the direct expansion coils 33 and 34 are rested as in the C region operation 2 of FIG. 11, the direct expansion coils 31 and 32 are stopped due to failure or maintenance as shown in (d) in the lower part of FIG. If this is unavoidable, the normal cooling capacity can be ensured by operating four of the direct expansion coils 33 and 34 and the direct expansion coils 21 and 22, and (e As shown in (4), if the direct expansion coils 21 and 22 have to be stopped due to failure or maintenance, the normal cooling capacity can be ensured by operating four of the direct expansion coils 31 to 34.
Thus, the rotation operation improves the efficiency of each direct expansion coil group, and as described above, each direct expansion coil itself can be finely controlled to enable efficient operation. Driving is possible.

As detailed above, according to each embodiment,
(1) Since the evaporation pressure of the refrigerant returning to the compressor is detected and the compression pressure of the compressor is controlled by the detected value of the evaporation pressure, fine control is possible even in the direct expansion coil. Since there is no indirect heat transfer, the heating and cooling efficiency of the direct expansion coil system exceeds that of the water coil, enabling energy-saving operation.
(2) In operation of the compressor, in addition to a control system for controlling the compression pressure of the compressor according to the value of the evaporation pressure, a control system for detecting the room temperature is also provided, and signals from these control systems are selected by the selection circuit 391. Since the compression pressure is controlled by selection and the cooling temperature in the direct expansion coil is controlled so that the direct expansion coil 35 always circulates with the refrigerant in the non-freezing region or higher, a freezing accident can be avoided.
(3) In addition to avoiding freezing, by changing the value that limits the evaporation pressure (evaporation temperature) of the direct expansion coil 31, the evaporation temperature is always kept higher than a certain level (see the solid line refrigeration cycle in FIG. 7). High efficiency operation becomes possible.
(4) Since the coil evaporation temperature can be controlled, in the case of air conditioning that requires non-condensing operation, the evaporating pressure (evaporating temperature) is kept above the air dew point temperature, that is, the non-condensing operation of the direct expansion coil 31 to be cooled. Is also possible.

(4) A multi-stage (two-stage) parallel direct expansion coil group is further arranged so that the direct expansion coil outlet temperature can be set by fine stage control even at large air volumes and loads that cannot be handled by a single refrigerator. The dew point temperature can be controlled. In particular, since the second direct expansion coil group 3 is arranged in four stages in parallel in the embodiment, accurate temperature / humidity control can be performed at a position close to the supply air.
(5) By arranging the direct expansion coil groups 2 and 3 in series, according to the air conditions at each stage, the refrigerator performs the optimum evaporating pressure operation, so that the energy performance coefficient is better than the conventional system, Since the error of the air temperature at the outlet of the direct expansion coil is about ± 0.6 ° C, less energy is used for reheating and humidification. Note that this apparatus is also compatible with reheating coils and heat pumps (refrigerants).
(6) The air conditioner using the direct expansion coil of the embodiment is different from the air conditioner using the conventional water coil, so that it is not necessary to cool with cold water. Only an outdoor unit installation space is required, and a machine room with a cold heat source for the water coil is not required.

(7) Rotation operation is possible by combining a parallel-arranged direct expansion coil group and a parallel-arrangement direct expansion coil group in a two-stage series installation. Long life of the direct expansion coil group and outdoor unit is achieved by rotation operation. In addition, it is possible to easily cope with backup operation when some directly expanded coils and outdoor units are out of order.
(8) In addition, since a plurality of directly expanded coil groups arranged in parallel are arranged in series in two stages to perform supply air dew point temperature control, after performing rough cooling control on the upstream directly expanded coil group, The temperature and humidity can be finely controlled with a group of directly expanded coils, and a wide range of temperature and humidity management is possible. In addition, a reheat coil and humidifier are installed in the lee as in the case of conventional water coils. In addition, it is possible to perform control that satisfies the constant temperature and humidity conditions.
(9) Since the blower 7 also serving as the air supply is disposed between the first direct expansion coil group 2 and the second direct expansion coil group 3, even if a part of the first direct expansion coil group 2 stops operating The aspirated air can be agitated and the cooling can be made uniform, and the conditioned air in the same state can be evenly blown to the plurality of downstream second direct expansion coil groups 3. Since almost the same load is applied to the expansion coils 31, 32, 33, and (34), there is no bias in operation, the service period can be extended, and there are few failures.
Of course, the present invention is not limited to the above-described embodiments as long as the features of the present invention are not impaired.

a ... cold water coil, b ... reheat coil, c ... humidifier, d ... valve,
e ・ Boiler, f ・ Valve, g1, g2, g3 ・ ・ Direct expansion coil,
h ・ ・ Refrigerator, i ・ ・ Valve, k1, k2, k3 ・ ・ Outdoor unit,
l. Blower (fan),
1. Air conditioner,
2. First direct expansion coil group, 21, 22, 23 ... Direct expansion coil,
211, 221, 231 .. Expansion (control) valve,
24..Outdoor unit, 241, ... Compressor, 242, ... Fan, 243 ... Condenser,
3. Second direct expansion coil group 31, 32, 33, (34), direct expansion coil,
311 .. Pressure sensor 312 Temperature sensor 313 Room temperature sensor 35 Compressor 36 Three-way valve
37 ... Condenser, 371 ... Outdoor unit,
38,382,383,384 ..expansion valve,
39 ... Central control unit, 391 ... Selection circuit, 392 ... Operation control circuit,
393 .. arithmetic control circuit,
4. Reheat coil, 41 Control valve (valve)
51..First humidifier, 511..Control valve (valve),
52 .. Second humidifier, 521 .. Control valve (valve),
6. Boiler,
7. Blower (fan)

Claims (3)

Two groups of direct expansion coils that introduce outside air and are cooled or heated by a refrigerant are arranged in series, a plurality of upstream first direct expansion coils are arranged in parallel, and a plurality of downstream second direct expansion coils are also included. In air conditioners arranged in parallel,
The downstream second direct expansion coil group can be controlled independently, detects the evaporation pressure of the refrigerant returning to the compressor, controls the compression pressure of the compressor based on the detected evaporation pressure value, and the direct expansion coil In addition to controlling the cooling temperature at room temperature, a control system based on detection of room temperature is also provided, the compression pressure is controlled by selecting signals from these control systems with a selection circuit, and the direct expansion coil is always above the non-freezing range The air conditioner using the direct expansion coil is characterized in that the cooling temperature in the direct expansion coil is controlled by circulating in the refrigerant.   The air conditioner using the direct expansion coil according to claim 1, wherein the second direct expansion coil group includes three or four direct expansion coils arranged in parallel.   The air conditioner using a direct expansion coil according to claim 1 or 2, wherein a blower also serving as an air supply is disposed between the first direct expansion coil group and the second direct expansion coil group.

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