JP2009014318A - Air conditioning system and its operating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suitable air conditioning system for a secondary coolant circulation type air conditioning system composed of a primary-side cold water circuit and a secondary-side coolant circuit. <P>SOLUTION: Along with starting control, cold water temperature Ta and coolant evaporation pressure Pa of the secondary-side coolant circuit are measured (S201). Next, present cold water temperature Ta is compared with critical cold water temperature Tc, and present evaporation pressure Pa is compared with critical evaporation pressure Pc (S202). When Ta is higher than Tc and Pa is higher than Pc, which means both the temperature and the pressure are over the critical values, operation of a compressor 4c is started so as to operate an auxiliary coolant circuit (or continue the operation if the circuit is already operating) (S203). When Ta is as low as or lower than Tc or Pa is as low as or lower than Pc, which means either value is below the critical value, the operation of the compressor 4c is stopped to stop the auxiliary coolant circuit (or continue the stop if the circuit is already stopped) (S204). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an air conditioning system and a method for operating the same, and more particularly to an air conditioning system suitable for a secondary refrigerant circulation air conditioning system including a primary side chilled water circuit and a secondary side refrigerant circuit.

Conventionally, as a technique related to an air conditioning system in a multi-story building or the like, an air conditioning system (hereinafter referred to as a secondary refrigerant circulation air conditioning system) configured by a primary side chilled water circuit and a secondary side refrigerant circuit has been disclosed (for example, Patent Document 1 and Patent Document 2). Such a conventional secondary refrigerant circulation air conditioning system 100 includes a primary chilled water circuit 103 and a secondary refrigerant circuit 104 as shown in FIG. The primary-side chilled water circuit 103 includes a heat source unit 101, primary-side chilled water pipes 103a and 103b that circulate cold water generated by the heat source unit in a building, and a circulation pump 103c. The heat source unit 101 is connected to a cooling water circuit 102 including a cooling water pipe 102a, a cooling tower 102b, and a cooling water pump 102c. The secondary refrigerant circuit 104 includes a secondary refrigerant pump unit (hereinafter referred to as a refrigerant unit) 112, an air conditioner (hereinafter referred to as AHU) 108, and a refrigerant pipe 113 that connects them. The refrigerant unit 112 stores therein a condenser 105 that exchanges heat with cold water supplied from the primary-side cold water circuit 103, a refrigerant tank 106, and a refrigerant pump 107. Further, the AHU 108 stores an evaporator 109, a blower fan 110, and a refrigerant pipe 113 that connects the refrigerant unit and the evaporator 109. With such a configuration, there is no need to provide cold water piping in the building, and troubles due to water leakage and the like can be solved.
JP 2004-28484 A JP-A-8-261517

When such a conventional secondary refrigerant circulation type air conditioning system is applied to a machine room air conditioner that houses an ICT device or the like, there are the following problems.
Normally, in machine room air conditioning, it is common not to perform dehumidification from the viewpoint of energy saving, but to perform high sensible heat operation control, but depending on the indoor environment conditions, it may be necessary to actively dehumidify. However, in the case of the secondary refrigerant circulation type air conditioning system, the refrigerant evaporation temperature in the evaporator depends on the primary side cold water temperature, so that the dehumidifying operation control becomes difficult when the cold water temperature is relatively high. In this case, it is difficult to control the evaporation temperature by lowering the primary side cold water temperature because it hinders the control of the other air conditioners connected to the heat source unit.

Furthermore, when the cold water temperature rises for some reason, such as a heat source machine failure, the AHU blown air temperature rises.
The present invention is for solving the above-described problem, and in a secondary refrigerant circulation air conditioning system, humidity control, blowing temperature control, and the like are stably performed for each AHU without being affected by the primary side cold water temperature. It provides control technology that can be used.

The gist of the present invention is as follows. That is,
The invention of claim 1 is a heat source unit, a primary side chilled water circuit that circulates chilled water generated in the heat source unit in a building, a first condenser that exchanges heat with the chilled water in the primary side chilled water circuit, and a refrigerant tank. A secondary refrigerant circuit comprising a refrigerant pump, an air conditioner (AHU) including a first evaporator and a blower fan, and a first refrigerant pipe connecting these, and a first condenser outlet side A second evaporator that exchanges heat with the refrigerant, an expansion valve on the inlet side of the second evaporator, a second condenser that exchanges heat with cold water on the outlet side of the first condenser, a compressor, and An air conditioning system comprising an auxiliary refrigerant circuit including a second refrigerant pipe to be connected.

In the above, AHU fan air volume control means and compressor rotation speed control means for controlling any one or more of the AHU blown air temperature, the dehumidification amount, or the first evaporator heat exchange amount are further provided. It is characterized (claim 2).
The invention of claim 3 is that in each of the above inventions, by performing either or both of increasing and decreasing the AHU fan air volume and increasing or decreasing the compressor rotational speed, the AHU blown air temperature, the dehumidifying amount, or the evaporator heat exchange amount It is the operating method of the air conditioning system characterized by controlling any one or more of these to the target range.

  In this case, the refrigerant flow rate of the secondary refrigerant circuit can be further controlled so as to maintain the gas-liquid two-phase state at the outlet of the first evaporator (Claim 4) or controlled so as to be in the gas phase state. (Claim 5).

  The invention according to claim 6 compares the measured dew point temperature of the AHU intake air with the target dew point temperature in each of the air conditioning systems described above, and reduces the AHU fan air volume when the measured dew point temperature is higher than the target dew point temperature. If the refrigerant evaporation temperature in the first evaporator is higher than the target dew point temperature when the AHU fan air volume reaches the lower limit value, the auxiliary refrigerant circuit starts operating, and then the dew point temperature of the AHU intake air When the measured value falls below the target dew point temperature, the operation of the auxiliary refrigerant circuit is stopped, and the AHU fan air volume is returned to the default value.

  According to the seventh aspect of the present invention, in each of the air conditioning systems, when at least one of the primary side cold water temperature or the refrigerant evaporation pressure of the first evaporator is equal to or higher than a set temperature or a set pressure, the auxiliary refrigerant circuit After that, when the primary side chilled water temperature falls below the set temperature and the evaporation pressure falls below the set pressure, or when it does not fall below the set temperature and set pressure for a certain period of time, the auxiliary refrigerant circuit An operation compensation method for an air conditioning system, characterized in that the operation is stopped.

  The operation of each of the above inventions will be described below. Tables 1 and 2 summarize the relationship between each control means and the air conditioning effect. The reason for dividing into the case of gas-phase (gas) return and the case of gas-liquid two-phase return is that the degree of refrigerant superheat in the evaporator varies depending on the amount of refrigerant flow and affects the cooling capacity. FIG. 5 is a graph showing the relationship between the refrigerant flow rate and the cooling capacity. In the figure, R1 is a gas phase return region, and in this range, the cooling capacity increases as the refrigerant flow rate increases. The superheat degree becomes 0 at the boundary between R1 and R2, and the cooling capacity becomes maximum at this refrigerant flow rate. Furthermore, it becomes a gas-liquid two-phase return region (R2) as the refrigerant flow rate increases. In this region, the heat exchange efficiency of the evaporator decreases as the gas-liquid ratio decreases, but the cooling capacity is substantially constant. When the refrigerant flow rate further increases, the liquid return region (R3) is obtained. In this region, the cooling capacity increases slightly as the pipe flow rate increases.

In view of this, Table 1 shows the amount of heat exchange of the evaporator (cooling capacity) when the AHU fan air volume or the compressor rotation speed of the auxiliary refrigerant circuit is increased or decreased in the case of gas-phase return and gas-liquid two-phase return. It shows the effect on the blown air temperature and the minimum evaporator temperature. The symbol of each effect column represents the following contents. That is,
“+”: “Increases and becomes higher”
"-": "Small / Lower"
“0”: “Almost no change”

  By controlling the control means shown in Table 1 alone or in combination, the cooling capacity, blowing temperature, and minimum evaporator temperature can be controlled. Table 2 shows the controllability by each control means.

一例として、気相戻り条件において「除湿制御」を行うためには、ＡＨＵファンについては蒸発器最低温度欄を（−）とする風量減少（Ａ２）が必要となる。これにより目標値に達しないときは、補助冷媒回路（コンプレッサ）の運転を行えばよい（Ｂ１）。

As an example, in order to perform “dehumidification control” under the gas-phase return condition, the air volume reduction (A2) is required for the AHU fan with the evaporator minimum temperature column set to (−). Accordingly, when the target value is not reached, the auxiliary refrigerant circuit (compressor) may be operated (B1).

  Next, with reference to FIG. 6, the influence of the auxiliary refrigerant circuit operation on the secondary refrigerant circuit will be described. Assuming that the cooling load is constant, initially, the refrigeration cycle when only the secondary refrigerant circuit is in operation is L1. In cycle L1, A → B is the pressure increasing process by the refrigerant pump, B → C is the pressure loss process up to the first evaporator, C → D is the evaporation process in the first evaporator, and D → E is the first evaporator. The pressure loss process from E to A, E → A, is the condensation process in the first condenser. The evaporation temperature at this time is T1. Thereafter, for example, the evaporating temperature rises as the condensing temperature rises due to the rising of the cold water temperature, and the refrigeration cycle becomes L2. The evaporation temperature at this time is T2. By operating the auxiliary refrigerant circuit at this stage, the condensation temperature of the secondary refrigerant circuit can be lowered, and the refrigeration cycle becomes L3 = L1, and the initial evaporation temperature can be maintained.

According to the present invention, discharge temperature control, humidity control, and the like can be performed for each AHU regardless of the primary-side chilled water temperature, and the auxiliary refrigerant circuit can be operated even when only the secondary-side refrigerant circuit cannot handle the load. Can be supported.
Moreover, even if the temperature of the cold water rises for some reason, such as a heat source machine failure, it is possible to avoid an increase in the AHU blown air temperature by operating the auxiliary refrigerant circuit.

  Hereinafter, each embodiment of the secondary refrigerant circulation air conditioning system according to the present invention will be described in more detail with reference to FIGS. In order to avoid redundant explanation, the same components are denoted by the same reference numerals in the respective drawings. Needless to say, the scope of the present invention is described in the claims and is not limited to the following embodiments.

<First embodiment>
A first embodiment of the present invention will be described with reference to FIGS. In the present embodiment, dehumidification control is realized by AHU fan air volume operation and auxiliary refrigerant circuit operation. This embodiment is applicable regardless of the return state of the refrigerant. FIG. 1 is a diagram showing a secondary refrigerant circulation air conditioning system 1 according to the present embodiment. The secondary refrigerant circulation air conditioning system 1 includes a primary side chilled water circuit 2, a secondary side refrigerant circuit 3, and an auxiliary refrigerant circuit 4.
The primary-side chilled water circuit 2 includes a heat source device 10 that is disposed on the roof of a building and serves as a chilled water generation source, a primary-side chilled water pipe 5 that circulates chilled water in the building, and a branched chilled water pipe 5a as main components.

Moreover, the secondary side refrigerant circuit 3 is provided with the refrigerant | coolant unit 6, AHU7, and the refrigerant | coolant piping 8 which connects these as main structures. The refrigerant unit 6 includes, as main components, a condenser 6a, a refrigerant tank 6b, and a refrigerant pump 6c for exchanging heat between the cold water supplied via the branch cold water pipe 5a and the refrigerant. Moreover, AHU7 is provided with the evaporator 7a and the blowing fan 7b. Below the evaporator 7a, a drain pan 7e and a drain pipe 7d are provided for receiving condensed water generated by heat exchange and discharging it to the outside. Further, a suction air dew point temperature Td detection sensor S1 is disposed in the vicinity of the suction port 7c of the AHU 7, and a pressure sensor S2 for detection of the refrigerant pressure Pa is disposed in the refrigerant pipe of the evaporator 7a.
With the above configuration, the secondary refrigerant circuit 3 temporarily stores the refrigerant condensed by exchanging heat with cold water in the condenser 6a in the refrigerant tank 6b, and then conveys the refrigerant to the evaporator 7a with the refrigerant pump 6c. A refrigeration cycle is configured in which the refrigerant that has evaporated by cooling the intake air is returned to the condenser 6a.

  Next, the auxiliary refrigerant circuit 4 has an auxiliary condenser 4a that exchanges heat with the outlet side cold water of the condenser 6a of the primary side chilled water circuit 2, and an auxiliary evaporation that exchanges heat with the outlet side refrigerant of the condenser 6a of the secondary side refrigerant circuit 3. An expansion valve 4e, a compressor 4c, and an auxiliary refrigerant pipe 4d connecting them are provided as main components on the inlet side of the auxiliary unit 4b and the auxiliary evaporator 4. With the above configuration, in the auxiliary refrigerant circuit 4, the refrigerant gas whose pressure has been increased by the compressor 4 c is conveyed to the auxiliary condenser 4 a, where it dissipates heat to the cold water returning to the heat source unit 10 and condenses itself into a high-pressure refrigerant liquid. . Further, the refrigerant is conveyed to the auxiliary evaporator 4b while being self-evaporated by adiabatic expansion in the expansion valve 4e, where it absorbs heat from the refrigerant in the secondary refrigerant circuit 3 and evaporates to return to the compressor 4c as refrigerant gas. As described above, a system is constructed in which the secondary refrigerant cooled as a whole by the condenser 6a is further cooled by the auxiliary evaporator 4b and supplied to the AHU 7 by the secondary refrigerant circuit and the auxiliary refrigerant circuit.

The secondary refrigerant circulation air conditioning system 1 is configured as described above. Next, the humidity control operation flow in the secondary refrigerant circulation air conditioning system 1 will be described with reference to FIG. A command necessary for control is performed by a control unit (not shown) provided in the system.
With the start of control, the dew point temperature Td of the intake air is measured by the dew point temperature sensor S1 (S101). Next, the dew point temperature Td is compared with the target dew point temperature T0 (S102). Here, the target dew point temperature T0 is a numerical value that is updated at regular intervals corresponding to the room temperature and the target relative humidity.

  When Td ≦ T0, that is, below the target dew point temperature, the fan air volume is returned to the default value to avoid further dehumidification (S115). When Td> T0, that is, when the current dew point temperature is higher than the target dew point temperature, the dehumidification control is continued (or shifted). First, it is determined whether or not the fan air volume has already reached the lower limit (S103). If the fan air volume has not reached the lower limit, the fan air volume is decreased by one step (S105). As a result, the amount of circulating air is reduced, the evaporator temperature is lowered, and the sensible heat ratio is lowered, so that it is possible to approach the dew condensation condition.

When the fan air volume has already reached the lower limit, the lower limit rotational speed is maintained (S104). Further, the refrigerant pressure Pa is measured by the pressure sensor S2 (S106), and the refrigerant evaporation temperature Tv is calculated based on the measured value (S107). Next, the refrigerant evaporation temperature Tv and the target dew point temperature Td are compared (S108). When Tv <Td, it corresponds to the dehumidifying condition, so the operation is continued as it is (YES in S108).

When Tv ≧ Td, the compressor 4c is started to operate and the auxiliary refrigerant circuit 4 is operated in order to lower the evaporation temperature and adapt to the dehumidifying conditions (S109). After starting the operation, the dew point temperature Td of the intake air is measured every predetermined time (S110). Next, the current dew point temperature and the target dew point temperature T0 are compared (S111). When Td> T0, the auxiliary refrigerant circuit 4 continues to operate for a predetermined time (S114). When Td ≦ T0, that is, when the temperature is equal to or lower than the target dew point temperature, the operation of the compressor 4c is stopped and the operation returns to the operation of only the secondary side refrigerant circuit (S112).
By performing the above control at appropriate intervals, the room humidity can be maintained at the target humidity while dehumidifying.

<Second Embodiment>
Next, another embodiment of the present invention will be described with reference to FIGS. In the present embodiment, when the primary side cold water temperature is abnormal, the minimum air conditioning is ensured by only the secondary side refrigerant circuit and the auxiliary refrigerant circuit for emergency evacuation. This embodiment can be applied under the condition where the gas-liquid two-phase return or the superheat degree control is used to control the gas-phase return. Referring to FIG. 3, the configuration of the secondary refrigerant circulation air conditioning system 20 according to the present embodiment is different from the above-described secondary refrigerant circulation air conditioning system 1 in that the chilled water supply temperature Tc of the primary chilled water circuit is measured. Temperature sensor S3 is provided. About another structure, since it is the same as the secondary refrigerant circulation type air conditioning system 1, duplication description is abbreviate | omitted.

  Next, the operation control flow in the present embodiment will be described with reference to FIG. With the start of control, the cold water temperature Ta and the refrigerant evaporation pressure Pa of the secondary refrigerant circuit are measured (S201). Next, the current cold water temperature Ta and the limit cold water temperature Tc, and the current evaporation pressure Pa and the limit evaporation pressure Pc are compared. When Ta> Tc and Pa> Pc, i.e., both exceed the limit values (YES in S202), the compressor 4c is started to operate the auxiliary refrigerant circuit (continue if already operating). (S203). When Ta ≦ Tc or Pa ≦ Pc, that is, when any value is below the limit value (NO in S202), the operation of the compressor 4c is stopped and the auxiliary refrigerant circuit is stopped (already stopped). (S204).

  In the present embodiment, Ta> Tc and Pa> Pc are set as the auxiliary refrigerant circuit operating condition in S202 and the following, but Ta> Tc or Pa> Pc may be set as the criterion. Furthermore, it is possible to control only one of the cold water temperature Ta and the evaporation pressure Pa as a criterion.

  In this embodiment, an air conditioner having two refrigerant circulation systems is used. However, three or more refrigerant circulation systems may be provided. Furthermore, it is good also as a form which carries out cooperation control of several air conditioners.

  The present invention can be widely applied to a secondary refrigerant circulation type air conditioning system regardless of a heat source system, a refrigerant, an air conditioning system, a building structure, and the like.

It is a figure showing secondary refrigerant circulation type air harmony system 1 concerning a first embodiment. It is a figure which shows the humidity control operation | movement flow in 1st embodiment. It is a figure which shows the secondary refrigerant | coolant circulation type air conditioning system 20 which concerns on 2nd embodiment. It is a figure which shows the capability compensation driving | operation control flow in 2nd embodiment. It is a figure which shows the relationship between a refrigerant | coolant flow volume and cooling capacity. It is a figure explaining the effect which an auxiliary refrigerant circuit operation gives to a secondary side refrigerant circuit. It is a figure which shows the conventional secondary refrigerant circulation type air conditioning system.

Explanation of symbols

1, 20... Secondary refrigerant circulation air conditioning system 2... Primary side chilled water circuit 3... Secondary side refrigerant circuit 4. Auxiliary condenser 4b ... Auxiliary evaporator 4c ... Compressor 4d ... Auxiliary refrigerant piping 5 ... Primary cold water piping 6 ... Refrigerant unit 6a ... Condensation ··· Refrigerant tank 6c ··· Refrigerant pump 7a ··· Evaporator 7b ··· Blowing fan 7c ··· Suction port 7d ··· Drain pipe 7e ··· Drain pan 8 ... Refrigerant piping 10 ... Heat source machine S1 ... Dew point temperature sensor S2 ... Pressure sensor S3 ... Temperature sensor

Claims (7)

A heat source machine,
A primary-side chilled water circuit that circulates cold water generated in the heat source machine in the building;
A first condenser that exchanges heat with the cold water in the primary chilled water circuit, a refrigerant tank, a refrigerant pump, an air conditioner (AHU) that includes a first evaporator and a blower fan, and a first refrigerant pipe that connects them. A secondary side refrigerant circuit comprising:
A second evaporator for exchanging heat with the refrigerant on the outlet side of the first condenser, an expansion valve on the inlet side of the second evaporator, and a second condenser for exchanging heat with cold water on the outlet side of the first condenser And an auxiliary refrigerant circuit comprising a compressor and a second refrigerant pipe connecting them,
An air conditioning system comprising: AHU fan air volume control means and compressor rotation speed control means for controlling any one or more of the AHU blown air temperature, dehumidification amount, or first evaporator heat exchange amount are further provided. The air conditioning system according to claim 1. In the air conditioning system according to claim 1 or 2,
Control one or more of the AHU blown air temperature, dehumidification amount, or evaporator heat exchange amount within the target range by either increasing or decreasing the AHU fan air volume or increasing or decreasing the compressor speed. A method of operating an air conditioning system characterized by the above. 4. The method of operating an air conditioning system according to claim 3, further comprising controlling the refrigerant flow rate of the secondary refrigerant circuit so as to maintain a gas-liquid two-phase state at the outlet of the first evaporator. 4. The method of operating an air conditioning system according to claim 3, wherein the refrigerant flow rate of the secondary refrigerant circuit is further controlled so as to be in a gas phase state at the outlet of the first evaporator. In the air conditioning system according to claim 1 or 2,
Compare the measured dew point temperature of the AHU intake air with the target dew point temperature.
When the measured dew point temperature is higher than the target dew point temperature, reduce the AHU fan air volume,
When the AHU fan air volume reaches the lower limit, and the refrigerant evaporation temperature in the first evaporator is higher than the target dew point temperature, the operation of the auxiliary refrigerant circuit is started.
Thereafter, when the measured dew point temperature of the AHU intake air falls below the target dew point temperature, the operation of the auxiliary refrigerant circuit is stopped, and the AHU fan air volume is returned to the default value.
A humidity control operation method for an air conditioning system. The air conditioning system according to any one of claims 1 to 3,
When at least one of the primary side cold water temperature or the refrigerant evaporation pressure of the first evaporator is equal to or higher than a set temperature or a set pressure, the operation of the auxiliary refrigerant circuit is started,
Thereafter, when the primary chilled water temperature falls below the set temperature and the evaporation pressure falls below the set pressure, or when it does not fall below the set temperature and set pressure for a certain period of time, the operation of the auxiliary refrigerant circuit is stopped.
A capability-compensated operation method for an air-conditioning system.

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