Heat source system

Abstract

To provide a heat source system which can appropriately execute an operation unit control using a new index showing a load of variable speed turbo hear source unit such as a variable speed turbo freezer.SOLUTION: A heat source system includes: a plurality of heat source units 1, 2 including a variable speed turbo heat source unit 1; and an operation unit control device 3 for controlling the number of operation units in the plurality of heat source units 1, 2. The operation unit control device 3 calculates a load index value of the variable speed turbo heat source unit 1 by multiplying the relative value of an opening of a suction guide vane 16 of the variable speed turbo heat source unit 1 with the relative value of a rotation speed of a compressor 11 of the variable speed turbo heat source unit 1. When the load index value is above the first reference value, the number of operation units in the heat source units is increased. When the load index value is below the second reference value, the number of operation units in the heat source units is decreased.SELECTED DRAWING: Figure 1

Description

【Technical Field】 【0001】 The present invention relates to a heat source system including a plurality of heat source machines for air conditioning and temperature control, and particularly relates to the control of the number of operating heat source machines including variable speed turbo heat source machines such as variable speed turbo chillers and variable speed turbo heat pumps. 【Background Art】 【0002】 Generally, heat source machines are equipped with a function to adjust their output, and the output is increased or decreased in accordance with the increase or decrease of the load so that the temperature of a heat transfer medium such as chilled water falls within a predetermined range. However, generally, there is an appropriate load for a heat source machine, and when there are a plurality of heat source machines, it is necessary to control the number of operating heat source machines according to the total load in order to maintain the load of each heat source machine within an appropriate range. Further, if all the heat source machines are always operated, the operating time of each heat source machine becomes unnecessarily long, maintenance increases, and the power of auxiliary machines (pumps, fans, etc.) is wasted, which is not preferable from the viewpoint of energy saving. 【0003】 Therefore, in a heat source system having a plurality of heat source machines, in addition to the output control of each heat source machine, it is necessary to appropriately switch the number of operating heat source machines according to the increase or decrease of the load. Although the switching of the number of operating heat source machines is often performed manually, devices that perform this automatically are widely spread and are called operating number control devices and the like. 【0004】 A very diverse number of methods have been proposed and are used for the control of the number of operating machines. Representative methods of controlling the number of operating machines are as follows. In the following description, for the sake of convenience, a chilled water (for cooling) system is taken as an example, but basically the same applies to a heating (for heating) system, a brine (sub-zero heat source using antifreeze) system, and the like. Also, the names of the respective control methods are given for convenience of explanation and are not universal names. 【0005】 (Optimal Control Method) The optimal control method is a method that calculates various evaluation indicators such as power consumption and CO2 emissions according to the number of operating units from the operating conditions and load status of each heat source machine, and estimates whether the number of operating units is optimal using the evaluation indicators. Since it can optimize various parameters such as not only the number of operating units but also the flow rates of chilled water and cooling water, it has a high energy-saving effect. On the other hand, the optimal control method requires a large amount of information regarding the characteristics of heat source machines, auxiliary machines (pumps and fans), and facility piping (pressure loss), and it takes time and cost to collect and set these data. In addition, the computational load is high and it incurs costs for equipment, etc. Also, when the characteristics of heat source machines change due to external factors such as fouling of heat source machines, the optimal number of operating units may not be achieved. In particular, it is difficult to adopt the optimal control method at small-scale sites. 【0006】 (Temperature reference method) The temperature reference method monitors the outlet temperature of chilled water from each heat source machine or the temperature after the confluence of chilled water from multiple heat source machines, and increases the number of operating units when this temperature exceeds the upper limit reference value, and decreases the number of operating units when it falls below the lower limit reference value. Generally, a heat source machine adjusts the cooling capacity of the heat source machine so that the outlet temperature of the chilled water becomes the set target temperature. When the load exceeds the maximum cooling capacity of the heat source machine, the outlet temperature of the chilled water exceeds the target temperature because the chilled water cannot be cooled to the target temperature. On the other hand, when the load is below the minimum cooling capacity of the heat source machine, cooling becomes excessive and the temperature of the chilled water falls below the target temperature. Therefore, this temperature reference method detects fluctuations in the outlet temperature of the chilled water and increases or decreases the number of operating units to optimize the total cooling capacity. 【0007】 This temperature reference method is the simplest method, but according to this method, it is not possible to judge the excess or deficiency of the number of operating units until the chilled water temperature deviates from the target temperature. Therefore, it can only be used at sites where a certain degree of deviation of the chilled water temperature is allowed. Also, since the chilled water temperature is likely to fluctuate due to sudden increases or decreases in load, unnecessary increases and decreases in the number of operating units may occur due to false detection, and in some cases, the fluctuations in the chilled water temperature itself when the number of operating units increases and decreases may cause instability in repeatedly increasing and decreasing the number of operating units. 【0008】 (Output reference method) The output reference method calculates the refrigeration output of each heat source unit, increases the number of operating units when this exceeds the upper limit reference value, and decreases the number of operating units when it falls below the lower limit reference value. Since the number of operating units is controlled based on the refrigeration output of each individual heat source unit, the increase or decrease in the number of operating units can be carried out before the chilled water outlet temperature deviates, and the fluctuation of the chilled water temperature is also small. 【0009】 However, depending on the operating conditions of the heat source unit, the control of the number of operating units may not be properly performed. That is, generally, the cooling capacity of a heat source unit changes depending on the temperature of the cooling medium (cooling water for a water-cooled unit and outside air temperature for an air-cooled unit), the fouling state of the heat exchanger, etc. For this reason, the heat source unit may exhibit a cooling capacity greater than the rated cooling capacity (the cooling capacity increases), or conversely, when dirt or the like accumulates in the heat exchanger or there are minor malfunctions, the maximum cooling capacity may be less than the rated capacity (the cooling capacity decreases). In this case, even when it is actually not necessary to increase the number of operating units because the cooling capacity has increased, the number of operating units may be increased. On the other hand, since the cooling capacity has decreased and the refrigeration output does not reach the upper limit reference value, although the number of operating units should be increased, it may fall into a state where the number of operating units cannot be increased. Also, since the refrigeration output is calculated by measuring the chilled water flow rate, the equipment cost is also likely to be high. 【0010】 (Modulating valve opening method) In a heat source unit having a modulating valve, such as an absorption chiller having a gas control valve, when the opening degree of the modulating valve exceeds the upper limit reference value, the number of operating units is increased, and when it falls below the lower limit reference value, the number of operating units is decreased. In a heat source unit driven by fuel or steam, such as an absorption chiller or an absorption refrigerator, the heat source output is controlled by adjusting the fuel (gas control valve) or the amount of steam (steam valve). When the opening degree of the modulating valve is maximum, the heat source unit exhibits the maximum cooling capacity under the operating conditions, and when the opening degree of the modulating valve is minimum, it exhibits the minimum cooling capacity. Therefore, the control of the number of operating units can be performed using the opening degree of the modulating valve. 【0011】 The advantage of this method lies in the fact that the number of operating units can be surely increased or decreased. That is, even under conditions where the capacity increases or decreases due to factors such as the cooling water temperature and dirt, if the load is large, the control valve will always try to increase to the maximum opening, and if the load is small, it will be throttled to the minimum opening. And these are also the conditions where it is actually necessary to increase or decrease the number of operating units. Therefore, when the maximum and minimum capacities of the heat source machine increase or decrease due to external conditions, there is no unintended increase or decrease in the number of operating units, and the number of operating units can be increased or decreased when necessary, which is a preferable method in this regard. 【0012】 However, this control valve opening method can only be adopted by a heat source machine that increases or decreases the refrigeration capacity with a single control valve. For example, in the case of a fixed-speed turbo refrigerator, the same control can be performed by regarding the opening of the compressor suction guide vane as the control valve opening. However, a variable-speed turbo refrigerator has two parameters, namely the rotational speed of the compressor and the opening of the compressor suction guide vane, and this method cannot be used. 【Prior Art Documents】 【Patent Documents】 【0013】 【Patent Document 1】 Japanese Unexamined Patent Application Publication No. 2012-52719 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0014】 As described above, there are various control methods for the operating unit control method, each having its own advantages and disadvantages. If emphasis is placed on the stability (certainty) of control, the metering valve opening method is preferable. However, in a variable speed turbo chiller, there are two control items, namely, the opening of the suction guide vane and the rotational speed of the compressor, making it difficult to apply the metering valve opening method. Therefore, when using a variable speed turbo chiller, other methods have to be used. In this case, in order to ensure certainty, it is conceivable to combine two or more control methods, that is, to perform control using the capacity standard method while also using the temperature standard method as a backup. However, even with this combined method, there remain drawbacks such as increasing the number of operating units when it is actually unnecessary to do so, or the chilled water temperature deviating from the target temperature unintentionally. 【0015】 Therefore, the present invention provides a heat source system that can appropriately execute the operating unit control by using a novel index indicating the load of a variable speed turbo heat source machine such as a variable speed turbo chiller. 【Means for Solving the Problem】 【0016】 In one aspect, there is provided a heat source system for temperature adjustment, comprising a plurality of heat source machines including a variable speed turbo heat source machine, and an operating unit control device for controlling the number of operating units of the plurality of heat source machines. The variable speed turbo heat source machine includes a compressor for compressing refrigerant gas and an inverter for varying the rotational speed of the compressor. The compressor is provided with a suction guide vane for adjusting the suction flow rate of the refrigerant gas into the compressor. The operating unit control device calculates a load index value of the variable speed turbo heat source machine by multiplying the relative value of the opening of the suction guide vane by the relative value of the rotational speed of the compressor, and is configured to increase the number of operating units of the heat source machine when the load index value exceeds a first reference value, and to decrease the number of operating units of the heat source machine when the load index value is below a second reference value. 【0017】 The load index value can accurately indicate the load of a variable-speed turbo heat source machine having two control ends, namely, the opening degree of the suction guide vane and the rotational speed of the compressor. Therefore, the operating unit number control device can appropriately perform the operating unit number control based on the load index value. The calculation formula of the load index value is simple, and the operating unit number control using the load index value does not become complicated, and the technology of the present invention can be additionally introduced at many sites including existing machines. Even if the cooling / heating capacity of the heat source machine increases or decreases due to operating conditions or fouling of the heat source machine, the operating unit number control device can surely perform the unit number control based on the load index value. When the cooling / heating capacity is increasing, by operating the heat source machine up to above the rated heat output, the number of operating units of the heat source machine can be reduced, the increase in the operating time can be suppressed, and the number of maintenance times can be reduced. In addition to the variable-speed turbo heat source machine, in a heat source system including heat source machines of different types such as an absorption chiller, a fixed-speed turbo freezer, and a positive-displacement compression freezer, the operating unit number control device can perform the operating unit number control of these multiple heat source machines using the load index value. 【0018】 In one aspect, the operating unit number control device is configured to increase the number of operating units of the heat source machine when the average value of the load index value exceeds a first reference value, and to decrease the number of operating units of the heat source machine when the average value of the load index value is below a second reference value. The operating unit number control device can perform efficient operating unit number control based on the average operating state indicated by the load index value. In one aspect, the operating unit number control device is configured to increase the number of operating units of the heat source machine when the maximum value of the load index value exceeds a first reference value, and to decrease the number of operating units of the heat source machine when the minimum value of the load index value is below a second reference value. The operating unit number control device can perform stable operating unit number control based on the minimum value or the maximum value of the load index value. In one aspect, the relative value of the opening degree of the suction guide vane is the following formula Relative value of the opening degree of the suction guide vane = (Current opening of the suction guide vane - Minimum opening of the suction guide vane) / (Maximum opening of the suction guide vane - Minimum opening of the suction guide vane), and the relative value of the rotational speed of the compressor is calculated by the following formula Relative value of the rotational speed of the compressor = (Current rotational speed of the compressor - Minimum rotational speed of the compressor) / (Maximum rotational speed of the compressor - Minimum rotational speed of the compressor) is calculated by 【Advantages of the Invention】 【0019】 The load index value can accurately indicate the load of the variable-speed turbo heat source machine with two control ends, namely the opening of the suction guide vane and the rotational speed of the compressor. Therefore, the operating unit control device can appropriately perform the operating unit control based on the load index value. The calculation formula of the load index value is simple, and the operating unit control using the load index value is not complicated either. The technology of the present invention can be additionally introduced at many sites including existing machines. Even if the cooling / heating capacity of the heat source machine increases or decreases due to operating conditions or fouling of the heat source machine, the operating unit control device can surely perform the unit control based on the load index value. When the cooling / heating capacity increases, by operating the heat source machine up to above the rated heat output, the number of operating units of the heat source machine can be reduced to suppress the increase in operating time and reduce the number of maintenance times. In addition to the variable-speed turbo heat source machine, in a heat source system including heat source machines of different types such as absorption chillers, fixed-speed turbo chillers, and volumetric compression chillers, the operating unit control device can perform the operating unit control of these multiple heat source machines using the load index value. 【Brief Description of the Drawings】 【0020】 【Figure 1】 It is a schematic diagram showing an embodiment of a heat source system for temperature adjustment. 【Figure 2】 It is a schematic diagram showing an embodiment of a variable-speed turbo chiller. 【Figure 3】 It is a schematic diagram showing an embodiment of an absorption chiller / heater. 【Figure 4】 It is a graph showing an example of changes in the opening degree and rotational speed of a suction guide vane with respect to the refrigeration output at the time of high cooling water temperature and low cooling water temperature. 【Figure 5】 It is a graph representing the graph of FIG. 4 in another aspect. 【Embodiments for Carrying Out the Invention】 【0021】 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of a heat source system for temperature control. The heat source system shown in FIG. 1 includes a plurality of heat source machines 1, 2 including three variable-speed turbo chillers 1 and two absorption chiller / heaters 2, and an operating number control device 3 for controlling the number of operating units of the plurality of heat source machines 1, 2. The heat source machines 1, 2 are provided with heat source control units 5, 6, and these heat source control units 5, 6 are connected to the operating number control device 3 by a communication line 8. 【0022】 Each variable-speed turbo chiller 1 includes a compressor 11 and an inverter 12 for varying the rotational speed of the compressor 11. The variable-speed turbo chiller 1 is an example of a variable-speed turbo heat source machine. As another example of a variable-speed turbo heat source machine, a variable-speed turbo heat pump can be mentioned. The plurality of heat source machines provided in the heat source system may include a variable-speed turbo heat pump instead of or in addition to the variable-speed turbo chiller. Further, the heat source system may be provided with an absorption refrigerator instead of or in addition to the absorption chiller / heater 2. The number of variable-speed turbo chillers 1 and the number of absorption chiller / heaters 2 are not limited to the embodiment shown in FIG. 1. 【0023】 The operating number control device 3 includes a storage device 3a storing a program and an arithmetic device 3b that executes arithmetic operations according to instructions included in the program. The operating number control device 3 is composed of at least one computer. The storage device 3a includes a main storage device such as a random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) and a solid state drive (SSD). Examples of the arithmetic device 3b include a CPU (central processing unit), a GPU (graphics processing unit), a PLC (programmable logic controller), and an FPGA (field programmable gate array). However, the specific configuration of the operating number control device 3 is not limited to these examples. 【0024】 FIG. 2 is a schematic diagram showing an embodiment of the variable speed turbo refrigerator 1. The variable speed turbo refrigerator 1 includes a compressor 11 that compresses a refrigerant gas, a condenser 15 that condenses the compressed refrigerant gas to generate a refrigerant liquid, an evaporator 18 that evaporates the refrigerant liquid to generate a refrigerant gas, an inverter 12 that varies the rotational speed of the compressor 11, and a heat source machine control unit 5 that controls the refrigeration output of the variable speed turbo refrigerator 1. 【0025】 The suction port of the compressor 11 is connected to the evaporator 18 by a refrigerant pipe 14A. The discharge port of the compressor 11 is connected to the condenser 15 by a refrigerant pipe 14B. An expansion valve 20 is attached to a refrigerant pipe 14C extending from the condenser 15 to the evaporator 18. The expansion valve 20 is configured such that its opening degree is adjustable and is composed of, for example, an electric valve with variable opening degree. Note that, in order to improve efficiency, the variable speed turbo refrigerator may be provided with a subcooler that subcools the refrigerant liquid condensed in the condenser, an economizer that lowers the temperature by vaporizing a part of the refrigerant liquid, etc. Also, in order to compress the refrigerant evaporated in the economizer, some have an intermediate suction port provided in the compressor or compress the refrigerant in two stages by combining two compressors, but all can be handled in the same manner as the variable speed turbo refrigerator 1 of this embodiment in the present invention. 【0026】 The compressor 11 includes an impeller 21 and an electric motor 23 that rotates the impeller 21. The impeller 21 may be a single-stage impeller or a multi-stage impeller. The inverter 12 is connected to the electric motor 23 and can change the rotational speed of the electric motor 23 and the impeller 21 (i.e., the rotational speed of the compressor 11) by supplying power with a variable frequency to the electric motor 23. 【0027】 At the suction port of the compressor 11, a suction guide vane 16 for adjusting the suction flow rate of the refrigerant gas into the compressor 11 is arranged. The suction guide vane 16 is located on the suction side of the impeller 21. The suction guide vanes 16 are arranged radially. The suction guide vanes 16 rotate synchronously with each other by a predetermined angle about their own axis by a vane actuator 25, thereby changing the opening degree (angle) of the suction guide vanes 16. The refrigerant gas sent from the evaporator 18 passes through the suction guide vanes 16 and is then pressurized by the rotating impeller 21. The refrigerant gas pressurized by the compressor 11 is sent to the condenser 15 through the refrigerant pipe 14B. 【0028】 The inverter 12 and the vane actuator 25 are electrically connected to the heat source control unit 5, and the operations of the inverter 12 and the vane actuator 25, i.e., the rotational speed of the compressor 11 and the opening degree of the suction guide vanes 16, are controlled by the heat source control unit 5. 【0029】 The evaporator 18 exhibits a refrigeration effect by taking heat from the chilled water (fluid to be cooled) with the refrigerant liquid and evaporating the refrigerant liquid. The compressor 11 compresses the refrigerant gas generated in the evaporator 18, and the condenser 15 generates the refrigerant liquid by cooling and condensing the compressed refrigerant gas with the cooling water (cooling fluid). The refrigerant liquid is depressurized by passing through the expansion valve 20. The depressurized refrigerant liquid is sent to the evaporator 18. 【0030】 FIG. 3 is a schematic diagram showing an embodiment of the absorption chiller 2. As shown in FIG. 3, the absorption chiller 2 includes a regenerator 31, a condenser 32, an evaporator 33, and an absorber 34. The absorption chiller 2 is configured to perform heat transfer by circulating a refrigerant while undergoing a phase change with respect to a solution (absorbent liquid), and to generate chilled water. In the present embodiment, an aqueous LiBr solution is used as the solution, and water (H2O) is used as the refrigerant, but the present invention is not limited thereto, and other combinations of refrigerants and solutions (absorbent liquids) may be used. 【0031】 A partition wall 36 is provided between the regenerator 31 and the condenser 32, and the condenser 32 and the regenerator 31 communicate with each other above the partition wall 36. In one embodiment, the regenerator 31 and the condenser 32 may both be formed in a shell-and-tube type within a single can body. 【0032】 The regenerator 31 includes a burner 41 that burns the gas supplied from the gas line 40, and a gas control valve 43 as a metering valve that adjusts the flow rate of the gas supplied to the burner 41 through the gas line 40. The solution is transferred from the absorber 34 to the regenerator 31 through the diluted solution transfer pipe 45. The gas burned by the burner 41 forms a flame, and due to the heat of the flame, the refrigerant contained in the solution in the regenerator 31 evaporates, generating refrigerant gas. As a result, the solution is concentrated within the regenerator 31. The concentrated solution is transferred to the absorber 34 through the solution transfer pipe 46. The refrigerant gas flows into the condenser 32. The gas control valve 43 is connected to the heat source machine control unit 6, and the operation of the gas control valve 43, that is, the intensity of the flame formed by the burner 41, is controlled by the heat source machine control unit 6. 【0033】 The refrigeration output of the absorption chiller 2 is changed by the opening degree of the gas control valve 43 as a metering valve that adjusts the flow rate of the gas supplied to the burner 41. That is, when the opening degree of the gas control valve 43 increases, the refrigeration output of the absorption chiller 2 increases, and when the opening degree of the gas control valve 43 decreases, the refrigeration output of the absorption chiller 2 decreases. 【0034】 In one embodiment, instead of the burner 41, the regenerator 31 may be provided with a heating pipe through which a heating fluid such as steam flows. In this case, the refrigerant contained in the solution in the regenerator 31 is heated by the heating fluid in the heating pipe and evaporated to become refrigerant gas. The flow rate of the heating fluid flowing through the heating pipe is adjusted by a heating fluid flow rate regulating valve as a metering valve connected to the heating pipe. That is, the refrigerating output of the absorption chiller is changed by the opening degree of the heating fluid flow rate regulating valve as a metering valve. Note that there are also so-called double-effect or triple-effect absorption chillers that reheat the absorption solution with the refrigerant vapor evaporated in the regenerator. However, since generally there is one metering valve for these as well, they can be handled in the same manner as the absorption chiller 2 of this embodiment without any problem. 【0035】 The condenser 32 is configured to condense the refrigerant gas flowing in from the regenerator 31. The condenser 32 is provided with a condenser cooling water pipe 47 through which cooling water flows. The condenser cooling water pipe 47 is disposed inside the condenser 32. One end of the condenser cooling water pipe 47 is connected to the absorber cooling water pipe 50 in the absorber 34 via a pipe 48. The refrigerant gas flowing in from the regenerator 31 is condensed by being cooled by the cooling water flowing through the condenser cooling water pipe 47. The condensed refrigerant is supplied from the condenser 32 to the evaporator 33 through the refrigerant supply pipe 51. 【0036】 A partition wall 53 is provided between the evaporator 33 and the absorber 34, and the evaporator 33 and the absorber 34 communicate with each other above the partition wall 53. In one embodiment, the evaporator 33 and the absorber 34 may both be formed in a shell-and-tube type within one can body. 【0037】 The evaporator 33 is configured to evaporate the refrigerant condensed in the condenser 32 with cold water to cool the cold water. The evaporator 33 is provided with a cold water pipe 62 through which cold water flows, and a refrigerant spray nozzle 63 for spraying the refrigerant toward the cold water pipe 62. One end of the refrigerant transfer pipe 65 is connected to the bottom of the evaporator 33, and the other end of the refrigerant transfer pipe 65 is connected to the refrigerant spray nozzle 63. A refrigerant pump 66 for pumping the refrigerant through the refrigerant transfer pipe 65 to the refrigerant spray nozzle 63 is disposed in the refrigerant transfer pipe 65. 【0038】 The refrigerant sprayed from the refrigerant spray nozzle 63 contacts the cold water pipe 62 through which cold water flows and evaporates. The evaporator 33 cools the cold water flowing through the cold water pipe 62 by the latent heat of vaporization when the refrigerant evaporates. The refrigerant gas generated in the evaporator 33 flows into the absorber 34 from above the partition wall 53. The refrigerant remaining in the evaporator 33 without evaporating is stored at the bottom of the evaporator 33. 【0039】 The absorber 34 includes an absorber cooling water pipe 50 through which cooling water flows and a solution spray nozzle 71 that sprays a solution toward the absorber cooling water pipe 50. The absorber cooling water pipe 50 is connected to the condenser cooling water pipe 47 of the condenser 32 via a pipe 48. The cooling water flows through the absorber cooling water pipe 50 and then flows into the condenser cooling water pipe 47 through the pipe 48. The solution spray nozzle 71 is configured to spray the concentrated solution generated by the regenerator 31. The concentrated solution absorbs and dilutes the refrigerant gas flowing in from the evaporator 33. The diluted solution is stored at the bottom of the absorber 34. 【0040】 A diluted solution pump 74 for pumping the diluted solution to the regenerator 31 is arranged in the diluted solution transfer pipe 45. The diluted solution is transferred to the regenerator 61 through the diluted solution transfer pipe 45 by the diluted solution pump 74. In this way, cold water is generated while the refrigerant circulates. When heating is performed with the absorption chiller, by opening a switching valve (both not shown) in the communication pipe that sends the refrigerant vapor generated in the regenerator to the evaporator, the refrigerant vapor is sent to the evaporator, and the cold water (warm water during heating) is heated by its condensation heat. The condensed refrigerant liquid returns to the absorber through a dilution valve (not shown). 【0041】 The heat source system shown in FIG. 1 includes an absorption chiller 2, but an absorption refrigerator may be provided instead of or in addition to the absorption chiller 2. The configuration of the absorption refrigerator is basically the same as that of the absorption chiller 2, except that there is no communication pipe used during heating as described above. 【0042】 Next, the operation of the number-of-operating-units control device 3 will be described. The number-of-operating-units control device 3 is configured to control the number of operating units of the heat source machines 1 and 2 of the heat source system shown in FIG. 1 based on the load index value described below. More specifically, the number-of-operating-units control device 3 receives, from the heat source machine control unit 5 of one of the variable speed turbo chillers 1 that is in operation among the three variable speed turbo chillers 1 of the heat source system shown in FIG. 1, the value of the opening degree of the suction guide vane 16 of that variable speed turbo chiller 1 and the value of the rotational speed of the compressor 11 of that variable speed turbo chiller 1, calculates the relative value of the opening degree of the suction guide vane 16 and the relative value of the rotational speed of the compressor 11, and is configured to calculate the load index value of the variable speed turbo chiller 1 by multiplying the relative value of the opening degree of the suction guide vane 16 by the relative value of the rotational speed of the compressor 11. Further, the number-of-operating-units control device 3 is configured to increase the number of operating units of the heat source machine when the load index value exceeds the first reference value, and to decrease the number of operating units of the heat source machine when the load index value is lower than the second reference value. The first reference value is a value larger than the second reference value. 【0043】 The load index value is represented by the following formula. Load index value = Relative value of the opening degree of the suction guide vane 16 × Relative value of the rotational speed of the compressor 11 【0044】 The relative value of the opening degree of the suction guide vane 16 and the relative value of the rotational speed of the compressor 11 are represented by the following formulas. Relative value of the opening degree of the suction guide vane 16 = (Current opening degree of the suction guide vane 16 - Minimum opening degree of the suction guide vane 16) / (Maximum opening degree of the suction guide vane 16 - Minimum opening degree of the suction guide vane 16) Relative value of the rotational speed of the compressor 11 = (Current rotational speed of the compressor 11 - Minimum rotational speed of the compressor 11) / (Maximum rotational speed of the compressor 11 - Minimum rotational speed of the compressor 11) 【0045】 The above rotational speed (including the maximum rotational speed and the minimum rotational speed) corresponds to the rotational speed of the compressor 11, the rotational speed of the motor 23, or the driving frequency of the motor 23. The minimum rotational speed of the compressor 11 is the minimum rotational speed determined by the electrical or mechanical limitations of the motor 23, the inverter 12, or the compressor 11, and is usually 20% to 40% of the rated rotational speed. In the calculation of the load index value, the minimum rotational speed of the compressor 11 may be conveniently set to 0. 【0046】 The opening degree of the suction guide vane 16 can be represented by the angle (degrees) from the fully closed position, and it is handled in this way in this embodiment. In this case, the maximum opening degree is generally the angle at which the compression capacity of the compressor is maximized, and is about 90 to 120 degrees. The minimum opening degree is often not 0 in practice to avoid the compressor 11 being operated at a cut-off, but the minimum opening degree of the suction guide vane 16 may be conveniently set to 0 degrees. 【0047】 Hereinafter, the operation number control based on the load index value will be described in detail. The variable speed turbo refrigerator 1 adjusts the refrigeration output of the variable speed turbo refrigerator 1 by changing the opening degree of the suction guide vane 16 at the inlet of the compressor 11 and the rotational speed of the compressor 11. More specifically, the heat source control unit 5 first adjusts the refrigeration output by increasing or decreasing the rotational speed of the compressor 11, and then further adjusts the refrigeration output by changing the opening degree of the suction guide vane 16. Generally, when the rotational speed of the turbo refrigerator increases, the refrigeration output increases, and when it decreases, the refrigeration output decreases. When adjusting the refrigeration output by the rotational speed, the opening degree of the suction guide vane 16 is maximized. 【0048】 In the variable speed turbo refrigerator 1, if the rotational speed of the compressor 11 is reduced too much, so-called surging will occur, and thus the rotational speed cannot be reduced below a certain lower limit value. This lower limit value of the rotational speed is determined by the minimum work required to boost the refrigerant pressure from the pressure in the evaporator 18 to the pressure in the condenser 15. Therefore, here the lower limit value of the rotational speed of the compressor 11 is called the "work rotational speed". The work rotational speed is determined by calculation based on the pressure in the condenser 15 or the pressure in the condenser 15 and the pressure in the evaporator 18. Since the work rotational speed changes according to the pressure in the condenser 15, that is, the cooling water temperature, the range in which the refrigeration output can be changed only by the rotational speed of the compressor 11 varies depending on the cooling water temperature. Note that the work rotational speed may also be determined by calculation based on the cooling water temperature. 【0049】 When the rotational speed of the compressor 11 decreases and reaches the work rotational speed, the heat source control unit 5 then adjusts the refrigeration output by increasing or decreasing the opening degree of the suction guide vane 16. At this time, the rotational speed of the compressor 11 is maintained at the work rotational speed. The reason is that changing the rotational speed often results in less loss than changing the opening degree of the suction guide vane 16, and it is more efficient to reduce the rotational speed as much as possible and control the insufficient part by the opening degree of the suction guide vane 16. 【0050】 The suction guide vane 16 changes the characteristics of the compressor 11 by swirling the refrigerant gas sucked into the compressor 11, reducing the relative speed between the refrigerant gas and the impeller of the compressor 11, reducing the compressed air volume, and lowering the refrigeration output. The suction guide vane 16 can change the compressed air volume without significantly reducing the efficiency of the compressor 11. 【0051】 Next, the behavior change of the variable speed turbo refrigerator 1 when the temperature of the cooling water decreases will be described. First, when the temperature of the cooling water decreases, the pressure in the condenser 15 decreases. As a result, the head of the compressor 11 drops, the air volume increases, and the refrigeration output rises. Generally, since the rated output (100% output) of the refrigerator is set when the cooling water temperature is high, when the cooling water temperature drops, the maximum output of the variable speed turbo refrigerator 1 exceeds 100% of the rated output. On the other hand, since the work rotation speed decreases, the control range of the refrigeration output according to the rotation speed becomes wider. 【0052】 On the other hand, when the head of the compressor 11 drops, the minimum refrigeration output increases. As a result, the range in which the refrigeration output can be controlled by the opening degree of the suction guide vane 16 becomes even smaller. Note that although the correlation between the rotation speed of the compressor 11 and the opening degree of the suction guide vane 16 and the refrigeration output is not linear, since it has a positive correlation, the increasing and decreasing directions of the rotation speed of the compressor 11 and the opening degree of the suction guide vane 16 coincide with the increasing and decreasing directions of the refrigeration output. 【0053】 Figure 4 is a graph showing an example of changes in the opening degree of the suction guide vane 16 and the rotation speed of the compressor 11 with respect to the refrigeration output when the cooling water is at a high temperature and when the cooling water is at a low temperature. In Figure 4, the horizontal axis represents the relative value (%) of the refrigeration output when the rated refrigeration output is 100%, and the vertical axis represents the relative value (%) of the opening degree of the suction guide vane 16 and the relative value (%) of the rotation speed of the compressor 11. 【0054】 Figure 5 is a graph representing the graph of Figure 4 in another form, schematically showing how the opening degree of the suction guide vane 16 and the rotation speed of the compressor 11 are controlled within the range from the minimum to the maximum refrigeration output when the cooling water is at a high temperature and when the cooling water is at a low temperature. In Figure 5, the refrigeration output when the refrigeration capacity increases when the cooling water is at a low temperature is defined as the "maximum refrigeration output", and the refrigeration output is represented by the relative value with respect to this. In Figures 4 and 5, "high temperature" and "low temperature" mean that the cooling water temperature is relatively high or low within the operable range of the heat source machine, and do not mean that the temperature is absolutely high or low. 【0055】 When the refrigeration output is low, the refrigeration output is controlled by the opening degree of the suction guide vane 16, and when the refrigeration output is high, it is controlled by the rotational speed of the compressor 11. Hereinafter, the control by the opening degree of the suction guide vane 16 is referred to as vane opening control, and the control by the rotational speed of the compressor 11 is referred to as rotational speed control. 【0056】 During vane opening control, the rotational speed of the compressor 11 is maintained at the working rotational speed, and the opening degree of the suction guide vane 16 varies within the range of 0 to 100%. During rotational speed control, the opening degree of the suction guide vane 16 is maintained at 100%, and the rotational speed of the compressor 11 varies within the range from the working rotational speed to 100% of the rotational speed. 【0057】 In this embodiment, the heat source control unit 5 of the variable speed turbo refrigerator 1 calculates the working rotational speed based on the ratio of the pressures of the condenser 15 and the evaporator 18 and a table stored in a storage device (not shown) of the heat source control unit 5, and while changing the rotational speed of the compressor 11 between the working rotational speed and the maximum rotational speed, controls the rotational speed so that the outlet chilled water temperature of the refrigerator 1 becomes the set target value. At this time, the opening degree of the suction guide vane 16 is set to the maximum opening degree (100%) (rotational speed control mode). The above table is created as follows. During the actual operation of the variable speed turbo refrigerator 1, while changing the rotational speed of the compressor 11, surging is intentionally generated a plurality of times, and a plurality of observed values of the rotational speed of the compressor 11 when surging occurs and the ratio of the pressure in the condenser 15 to the pressure in the evaporator 18 (hereinafter referred to as the pressure ratio) are obtained, and a table showing the correlation between the rotational speed of the compressor 11 and the pressure ratio when surging occurs is created. The table created in this way is stored in a storage device (not shown) of the heat source control unit 5. 【0058】 When the refrigeration output does not drop to the required level even when the rotational speed of the compressor 11 is lowered to the working rotational speed, the heat source control unit 5 changes the opening degree of the suction guide vane 16 within the range from the maximum opening degree to the minimum opening degree while maintaining the rotational speed of the compressor 11 at the working rotational speed, and controls so that the outlet chilled water temperature of the heat source machine 1 becomes the target value (vane opening control mode). 【0059】 Here, the load index value will be described. In the rotational speed control range, the opening degree of the suction guide vane 16 is always 100%. Therefore, only the opening degree of the suction guide vane 16 cannot be used as the load index value. On the other hand, during the vane opening degree control, the rotational speed of the compressor 11 is constant at the work rotational speed. However, the rotational speed does not change from 0 to 100%, but changes within the range from the work rotational speed to 100% rotational speed. 【0060】 Therefore, during the rotational speed control, the rotational speed (%) of the compressor 11 is used as the load index value, and during the vane opening degree control, the product of the work rotational speed (%) and the opening degree (%) of the suction guide vane 16 is used as the load index value. The opening degree of the suction guide vane 16 is from 0 to 100%. Since the work rotational speed during the vane opening degree control is the actual rotational speed, the actual rotational speed can be used instead of the work rotational speed in the calculation of the load index value. By doing so, during the rotational speed control, since the opening degree of the suction guide vane 16 is always 100%, it becomes the same formula mathematically. That is, at all times, by using the aforementioned formula, the load index value can be calculated without changing the calculation method between the vane opening degree control and the rotational speed control. This indicates that there is no discontinuity in the formula for calculating the load index value, and it has favorable characteristics as a control index. 【0061】 Hereinafter, calculation examples of the load index value will be shown in several specific cases. (1) During the rotational speed control mode (when the cooling water is at a high temperature) When the work rotational speed is 90%, the relative value of the rotational speed is 95%, and the relative value of the opening degree of the suction guide vane 16 is 100%, the load index value = 100% × 95% = 95% (2) During the rotational speed control mode (when the cooling water is at a low temperature) When the work rotational speed is 70%, the relative value of the rotational speed is 80%, and the relative value of the opening degree of the suction guide vane 16 is 100%, the load index value = 100% × 80% = 80% (3) During the opening degree control of the suction guide vane 16 (when the cooling water is at a high temperature) When the work rotational speed is 90%, the relative value of the rotational speed is 90%, and the relative value of the opening degree of the suction guide vane 16 is 80%, the load index value = 80% × 90% = 72% (4) When controlling the opening degree of the suction guide vane 16 (when the cooling water is at a low temperature) When the workpiece rotation speed is 70%, the relative value of the rotation speed is 70%, and the relative value of the opening degree of the suction guide vane 16 is 60%, the load index value = 70% × 60% = 42% 【0062】 In the cases of (1) and (2) above, due to the rotation speed control mode, the relative value of the rotation speed of the compressor 11 is equal to or higher than the workpiece rotation speed, and the relative value of the opening degree of the suction guide vane 16 is 100%. In the cases of (3) and (4) above, since it is the vane opening degree control mode, the relative value of the rotation speed of the compressor 11 is equal to the workpiece rotation speed, and the opening degree of the suction guide vane 16 is between 0 and 100%. 【0063】 In the heat source system shown in FIG. 1, when only the variable speed turbo chiller 1 is operating, the operation number control device 3 increases the number of operating units when the load index value of the variable speed turbo chiller 1 during operation exceeds the first reference value, and decreases the number of operating units when the load index value is lower than the second reference value. 【0064】 In one embodiment, the operation number control device 3 increases the number of operating units when the average value of the load index value of the variable speed turbo chiller 1 during operation exceeds the first reference value, and decreases the number of operating units when the average value of the load index value is lower than the second reference value. The operation number control device 3 compares the average value of the load index value within the above-mentioned predetermined time with the first reference value and the second reference value every time a predetermined time (for example, 10 seconds) elapses. The first reference value is a value larger than the second reference value. The operation number control device 3 can perform efficient operation number control based on the average operation state indicated by the load index value. 【0065】 In other embodiments, when the maximum value of the load index value of the variable speed turbo chiller 1 during operation exceeds the first reference value, the number of operating units is increased, and when the minimum value of the load index value falls below the second reference value, the number of operating units is decreased. Every time a predetermined time (for example, 10 seconds) elapses, the operating unit number control device 3 compares the maximum value of the load index value within the predetermined time with the first reference value, and compares the minimum value of the load index value within the predetermined time with the second reference value. The first reference value is a value larger than the second reference value. When using the maximum and minimum values instead of the average value, even when there are differences in the capabilities of each heat source machine and the variation in the load index value is large, the operating unit number control device 3 can perform stable control of the number of operating units based on the maximum or minimum value of the load index value. 【0066】 The absorption chiller 2 controls the opening degree of the gas control valve 43 (see FIG. 3), which is a metering valve, so that the outlet temperature of the chilled water becomes the target temperature, and adjusts the gas combustion at the burner 41 to adjust the refrigeration output. When the regenerator 31 shown in FIG. 3 is provided with a heating pipe through which a heating fluid (for example, steam) flows instead of the burner 41, the absorption chiller 2 controls the opening degree of the heating fluid flow control valve, which is a metering valve, so that the outlet temperature of the chilled water becomes the target temperature, and adjusts the refrigeration output by adjusting the flow rate of the heating fluid flowing through the heating pipe with the heating fluid flow control valve. Since the absorption chiller 2 basically controls the refrigeration output only by the opening degree of the metering valve (for example, the gas control valve 43 or the heating fluid flow control valve), there are no vane opening control modes and rotational speed control modes such as those of the variable speed turbo chiller 1. 【0067】 The operating unit number control device 3 monitors the states of the heat source machines 1 and 2 via the communication line 8, and can switch the operation / stop of the heat source machines 1 and 2 or change the operation state via the communication line 8. The operating unit number control device 3 can, for example, limit the heat source machines to be operated according to the season or change the priority order of operation. For example, in winter, only the absorption chiller 2 is operated in the heating mode, in summer, the turbo chiller 1 is preferentially operated, and when the load cannot be covered, the absorption chiller 2 can be additionally operated. 【0068】 In the heat source system shown in FIG. 1, when the operating heat source machine is only the absorption chiller 2, the operating number control device 3 is configured to control the operating number of the heat source machine based on the opening degree of the regulating valve (for example, the gas control valve 43 or the heating fluid flow rate regulating valve) of the absorption chiller 2. More specifically, when the opening degree of the regulating valve of the absorption chiller 2 during operation exceeds the third reference value, the operating number of the heat source machine is increased, and when the opening degree of the regulating valve is lower than the fourth reference value, the operating number of the heat source machine is decreased. The third reference value is a value larger than the fourth reference value. 【0069】 In one embodiment, when the average value of the opening degree of the regulating valve of the absorption chiller 2 during operation exceeds the third reference value, the operating number control device 3 increases the operating number of the heat source machine, and when the average value of the opening degree of the regulating valve is lower than the fourth reference value, the operating number control device 3 decreases the operating number of the heat source machine. The third reference value is a value larger than the fourth reference value. In another embodiment, when the maximum value of the opening degree of the regulating valve of the absorption chiller 2 during operation exceeds the third reference value, the operating number control device 3 increases the operating number of the heat source machine, and when the minimum value of the opening degree of the regulating valve is lower than the fourth reference value, the operating number control device 3 decreases the operating number of the heat source machine. The third reference value is a value larger than the fourth reference value. Note that the first reference value may be used as the third reference value, and the second reference value may be used as the fourth reference value. 【0070】 The heat source system shown in FIG. 1 has an absorption chiller 2, but instead of the absorption chiller 2, an absorption refrigerator may be used. Even in this case, the operating number control device 3 can control the operating number of the heat source machine based on the opening degree of the regulating valve (for example, the gas control valve or the heating fluid flow rate regulating valve) of the absorption refrigerator during operation, similar to the absorption chiller 2. 【0071】 When the variable speed turbo chiller 1 and the absorption type chiller / heater 2 are operating simultaneously, the operating unit number control device 3 treats the load index value of the variable speed turbo chiller 1 and the opening degree of the regulating valve of the absorption type chiller / heater 2 as equivalent to the load index value of the variable speed turbo chiller, and performs the operating unit number control of the heat source machine. Specifically, when the maximum value (or the average value of these) of the load index value of the variable speed turbo chiller 1 and the opening degree of the regulating valve of the absorption type chiller / heater 2 exceeds the first reference value, the operating unit number of the heat source machine is increased, and when the minimum value (or the average value of these) of the load index value of the variable speed turbo chiller 1 and the opening degree of the regulating valve of the absorption type chiller / heater 2 is below the second reference value, the operating unit number of the heat source machine is decreased. As described above, since the load index value relatively indicates the load of the heat source machine, it can also be treated equivalently to the regulating valve opening degree, etc. 【0072】 In one embodiment, the above-described first reference value, second reference value, third reference value, and fourth reference value may be increased or decreased according to the number of heat source machines in operation. Specifically, at least one of the first reference value and the third reference value is increased, and at least one of the second reference value and the fourth reference value is decreased as the number of heat source machines in operation increases. By changing the first reference value, second reference value, third reference value, and fourth reference value based on the number of heat source machines in operation in this way, it is possible to avoid frequent repetition of increases and decreases in the operating unit number. 【0073】 In the embodiments described so far, the plurality of heat source machines included in the heat source system are a combination of the variable speed turbo chiller 1 and the absorption type chiller / heater 2, or a combination of the variable speed turbo chiller 1 and the absorption chiller, but the above-described operating unit number control is applicable not only to the above embodiments, but also to a heat source system including at least one of a variable speed turbo heat pump, a fixed speed turbo chiller, a fixed speed turbo heat pump, a positive displacement compression chiller, an absorption type chiller / heater, and an absorption chiller in addition to the variable speed turbo chiller 1. 【0074】 In some cases, for example, when it is desired to operate a turbo chiller preferentially over an absorption chiller (such as when it is desired to preferentially utilize renewable power, etc.), or conversely, when it is desired to operate an absorption chiller preferentially (such as when the power supply and demand is tight and power saving is required), the control is performed as follows. 【0075】 First, set the priority for each heat source machine. For example, when it is desired to operate a variable speed turbo chiller preferentially, the priority of the variable speed turbo chiller is set to "1", and the priority of the absorption chiller is set to "2". Although it is called the priority, it is better that the priorities are the same for the same type of heat source machines (there are multiple heat source machines with the same priority). 【0076】 Here, as described above, when the load index value and the maximum value (or average value) of the modulation valve opening degree of the heat source machine during operation exceed the first reference value, the heat source machine with the highest priority (the smallest numerical value) among the stopped heat source machines is operated. If there are multiple heat source machines with the highest priority among the stopped heat source machines, the heat source machine to be operated is determined by the one with a short operation time, etc., or by a random number, etc. 【0077】 Also, when the load index value and the minimum value (or average value) of the modulation valve opening degree of the heat source machine during operation are below the second reference value, the heat source machine with the lowest priority (the largest numerical value) among the heat source machines during operation is stopped. If there are multiple heat source machines with the lowest priority among the heat source machines during operation, the heat source machine to be operated is determined by the one with a long operation time, etc., or by a random number, etc. 【0078】 Note that the combination of the operation priorities of each heat source machine should be made changeable all at once by changing the so-called operation mode. For example, in the "power consumption suppression priority" mode, the priority of the absorption chiller is set higher than that of the variable speed turbo chiller, and in the "CO2 emission suppression priority" mode, the priority of the absorption chiller is set lower than that of the variable speed turbo chiller. By doing so, it becomes possible to operate according to the index prioritized in that situation, such as power saving and suppression of CO2 emissions. 【0079】 The above-described embodiments are described for the purpose of enabling those with ordinary knowledge in the technical field to which the present invention pertains to implement the present invention. Various modifications of the above embodiments are naturally possible for those skilled in the art, and the technical idea of the present invention can also be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is construed in the broadest scope in accordance with the technical idea defined by the claims. 【Explanation of Signs】 【0080】 1 Variable speed turbo chiller 2 Absorption chiller / heater 3 Operating unit control device 5,6 Heat source machine control unit 8 Communication line 11 Compressor 12 Inverter 14A,14B,14C Refrigerant piping 15 Condenser 16 Suction guide vane 18 Evaporator 20 Expansion valve 21 Impeller 23 Electric motor 25 Vane actuator 31 Regenerator 32 Condenser 33 Evaporator 34 Absorber 36 Partition wall 40 Gas line 41 Burner 43 Gas control valve 45 Dilute solution transfer pipe 46 Solution transfer pipe 47 Condenser cooling water pipe 48 Pipe 50 Absorber cooling water pipe 51 Refrigerant supply pipe 53 Partition wall 62 Cold water pipe 63 Refrigerant spray nozzle 65 Refrigerant transfer pipe 66 Refrigerant pump 71 Solution spray nozzle 74 Dilution solution pump

Claims

[Claim 1] A heat source system for temperature control, Multiple heat source units, including a variable-speed turbo heat source unit, The system includes an operating unit control device that controls the number of operating units of the aforementioned multiple heat source units, The aforementioned variable-speed turbo heat source unit includes a compressor for compressing refrigerant gas and an inverter for varying the rotational speed of the compressor. The compressor is equipped with suction guide vanes that adjust the suction flow rate of refrigerant gas into the compressor. The aforementioned control device for the number of operating vehicles is The load index value of the variable-speed turbo heat source is calculated by multiplying the relative value of the opening degree of the suction guide vane by the relative value of the rotational speed of the compressor. In the above calculation, the load index value is continuously calculated by using a common calculation formula in a rotational speed control mode in which the rotational speed of the compressor is controlled while maintaining the opening of the suction guide vane at its maximum opening, and in a vane opening control mode in which the opening of the suction guide vane is controlled while maintaining the rotational speed of the compressor at a workpiece rotational speed determined based on the work required to increase the pressure of the refrigerant. When the load index value exceeds the first reference value, the number of operating heat source units is increased. A heat source system configured to reduce the number of operating heat source units when the load index value falls below a second reference value. [Claim 2] The aforementioned control device for the number of operating vehicles is When the average value of the load index exceeds the first reference value, the number of operating heat source units is increased. The heat source system according to claim 1, wherein the system is configured to reduce the number of operating heat source units when the average value of the load index falls below a second reference value. [Claim 3] The aforementioned control device for the number of operating vehicles is When the maximum value of the load index exceeds the first reference value, the number of operating heat source units is increased. The heat source system according to claim 1, wherein the number of operating heat source units is reduced when the minimum value of the load index falls below a second reference value. [Claim 4] The relative value of the opening of the aforementioned suction guide vane is given by the following formula Relative value of the opening of the suction guide vane = (Current opening of the suction guide vane - Minimum opening of the suction guide vane) It is calculated by (maximum opening of the suction guide vane - minimum opening of the suction guide vane), The relative value of the rotational speed of the compressor is given by the following formula Relative value of the compressor's rotational speed = (Current rotational speed of the compressor - Minimum rotational speed of the compressor) (Maximum compressor rotational speed - Minimum compressor rotational speed) The heat source system according to claim 1, calculated by... [Claim 5] The plurality of heat source units include different types of heat source units whose heat source output is controlled by a metering valve, The heat source system according to claim 1, wherein the operating unit number control device controls the number of operating units of the plurality of heat source units by using the load index value of the variable-speed turbo heat source unit and the opening degree of the metering valve of the different type of heat source unit as equivalent indicators.

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