WO2014036935A1 - 中央空调载冷剂变温度变压力控制系统 - Google Patents

中央空调载冷剂变温度变压力控制系统 Download PDF

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Publication number
WO2014036935A1
WO2014036935A1 PCT/CN2013/082890 CN2013082890W WO2014036935A1 WO 2014036935 A1 WO2014036935 A1 WO 2014036935A1 CN 2013082890 W CN2013082890 W CN 2013082890W WO 2014036935 A1 WO2014036935 A1 WO 2014036935A1
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Prior art keywords
heat exchange
brine
temperature
control valve
control
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PCT/CN2013/082890
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English (en)
French (fr)
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林铖
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Lin Cheng
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Publication of WO2014036935A1 publication Critical patent/WO2014036935A1/zh

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B25/00—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00
    • F25B25/005—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00 using primary and secondary systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/70—Control systems characterised by their outputs; Constructional details thereof
    • F24F11/80—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air
    • F24F11/83—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/70—Control systems characterised by their outputs; Constructional details thereof
    • F24F11/80—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air
    • F24F11/83—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers
    • F24F11/84—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers using valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/70—Control systems characterised by their outputs; Constructional details thereof
    • F24F11/80—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air
    • F24F11/83—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers
    • F24F11/85—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers using variable-flow pumps

Definitions

  • the invention relates to a method for controlling the temperature and pressure of a brine in a central air conditioner.
  • the flow head of the pump in the central air conditioner and the heat exchange capacity of the heat exchanger are generally selected according to the maximum load, and the margin is left. However, in actual operation, the load rate is often low, so as shown in Figure 1, the end heat exchange equipment 3
  • a control system is generally installed, and the refrigerant control valve 5 may be a regulating valve or an on-off valve, and the controller 6 is based on the control point temperature sensor 4
  • the deviation between the reading (usually indoor temperature or outlet temperature) and the set value turn off (or turn off) the large (or open) brine control valve to adjust the refrigerant flow, and then adjust the heat transfer , so that the control point temperature reaches the set value or fluctuates around the set value.
  • the pump 2 is not properly adjusted, which causes waste of energy. So generally for the pump 2 Use variable frequency speed regulation or number adjustment to adapt its flow head to the system requirements. At the same time, the coolant supply temperature is reset, and the cold heat source can also be reduced. Power consumption. However, in the prior art, the above adjustment does not have a perfect control model.
  • the flow head adjustment strategy of the pump is generally used in the following manner: a constant temperature difference mode and a constant pressure difference mode.
  • the constant temperature difference mode controls the temperature of the refrigerant to return to the temperature difference ⁇ T Constant, although the logic is simple and easy to implement, but because the system's flow and load changes are not consistent, resulting in end underflow or overcurrent.
  • Constant pressure difference mode control constant pressure differential pressure difference ⁇ P Constant.
  • the constant pressure difference should be set at the most unfavorable loop, but because the pipe network is complicated, the most unfavorable loop is not constant, and it is difficult to find the ideal constant pressure difference and pressure difference.
  • the temperature of the coolant transporting the cold and heat source is generally set by means of the outdoor temperature or the load rate.
  • the heat exchange requirements at the respective end heat exchange equipment are different, the adjustment will not be in place, or part of the adjustment.
  • the heat exchange capacity at the end heat exchange equipment is insufficient.
  • ZL200810026583.X A central air conditioning system that can simultaneously control the temperature difference between the air conditioner and the temperature of the supply and return water is disclosed.
  • the temperature difference between the inlet and outlet water flowing through the end device of the air conditioner and the water supply amount can be controlled to ensure that the water system allocates water according to the demand.
  • its solution is limited to the end heat exchange equipment, and there is no mention of an optimized implementation of the overall system.
  • the end heat exchange equipment control system uses two temperature sensors, water inlet and outlet, which increases complexity and cost.
  • the technical problem mainly solved by the invention is that in the dynamic operation of the variable flow of the system, under the premise of satisfying the heat exchange amount of the end heat exchange device, the pump delivery pressure is maximized and improved (in the case of cooling, such as heating) Then reduce) the coolant delivery temperature.
  • a control system for a terminal heat exchange device in a central air conditioner that indirectly transfers heat through a refrigerant comprising: a controller, a brine control valve.
  • the utility model is characterized in that: the opening degree of the brine control valve is adjustable; the refrigerant coolant outlet temperature sensor is provided; and the brine coolant outlet temperature is one of the control parameters, the opening of the brine control valve is adjusted; the controller has The communication interface and the coolant outlet temperature control parameters are given by the communication.
  • the control system has a control physical quantity and a physical quantity target value; and is characterized in that: according to the physical quantity and the target value, the target value of the brine outlet temperature is calculated; and the brine control valve opening degree is adjusted to make the brine outlet temperature Reach the target value.
  • control system is characterized in that: the end heat exchange device has a fan with an adjustable air volume; and the air volume of the fan is adjusted according to the temperature of the coolant outlet.
  • control system is characterized in that the valve body of the brine control valve is provided with a hole through which the sensor element of the coolant outlet temperature sensor is inserted into the flow path.
  • the control system is characterized in that: the refrigerant control valve driver has a built-in temperature collecting circuit, and is connected with a brine outlet temperature sensor; the controller controls the driver by means of communication.
  • the control system is characterized in that the connecting line of the brine control valve driver and the brine outlet temperature sensor has an intermediate plug connector.
  • the control system is characterized in that there are three wires connected between the controller and the driver, two of which are power lines and one is a communication line.
  • a method for measuring heat exchange amount as claimed in claim 1
  • the control system is characterized in that the heat exchange power is calculated according to the temperature of the brine outlet and the air volume of the fan, and the heat exchange power is accumulated by time to obtain the heat exchange amount.
  • a method as claimed in claim 1 The calibration method of the refrigerant outlet temperature sensor of the control system is characterized in that: a brine temperature sensor is set as a reference sensor at a typical position of the pipe network; the brine is in a circulating state; The thermal equipment is in a no-load state and the brine control valve is opened; the reference sensor is used to read the coolant outlet temperature sensor of the quasi-end heat exchange device.
  • a method for controlling the delivery pressure of a brine for use in a cold heat source, a pump, a coolant line, and according to claim 1 The central air conditioner of the terminal heat exchange device and the communication network of the control system is characterized in that when the opening degree of the refrigerant control valve of all the end heat exchange devices is not fully opened, the refrigerant delivery pressure is lowered; When the coolant control valve of a terminal heat exchange device is fully open and still cannot meet the flow demand, the delivery pressure of the brine is increased.
  • a method for controlling the temperature of a refrigerant delivery temperature comprising a cold heat source, a pump, a coolant line, and the use of claim 1
  • the central air conditioner of the terminal heat exchange device and the communication network of the control system is characterized in that: when the refrigerant outlet temperature of all the end heat exchange devices is greater than the limit value in the cooling condition, the brine is increased.
  • the control method is characterized in that: when calculating the coolant delivery temperature, the state of the end heat exchange device as a bottleneck is ignored; and the limit value of the coolant outlet temperature of the end heat exchange device as the bottleneck is changed The thermal calculation results are used to override the control.
  • a method for controlling a differential pressure of a branch for use in claim 12 The central air conditioner brine branch of the control system is characterized in that: a control valve with an adjustable opening is installed on the branch trunk; when the branch is as claimed in claim 1 When the refrigerant control valve of the control system is not fully open, the control valve is closed; when the coolant control valve of the control system of claim 1 is fully opened, the control valve of the control system is still not fully satisfied. When the flow demand is required, open the above control valve.
  • FIG. 1 Traditional variable flow central air conditioning system
  • Coolant delivery temperature sensor 10. Coolant delivery temperature sensor
  • FIG. 4 Relationship between cooling capacity and chilled water flow at different inlet temperatures
  • Figure 6 Schematic diagram of the cascade adjustment of the indoor temperature ⁇ brine outlet temperature ⁇ brine control valve
  • FIG. 8 Schematic diagram of air volume adjustment with chilled water outlet temperature
  • Figure 9 Schematic diagram of air volume adjustment with chilled water outlet when leveling
  • FIG. 12 Schematic diagram of the refrigerant circulation branch
  • Valve body 18. Spool 19. Driver 20. Internal connection 21. Tee 22. Temperature sensor 23. Pipe
  • Valve body 18. Spool 19. Drive 22. Temperature sensor 23. Pipe
  • FIG. 16 Schematic diagram of terminal heat exchange equipment control system wiring
  • the central air conditioner in this manual refers not only to the summer refrigeration system but also to the winter heating system.
  • the same cold heat source can be a chiller, or a heat pump hot water unit, a boiler, a heat exchanger, and the like.
  • the brine generally refers to water, and may also be a brine solution and other liquids. This description focuses on the analysis of summer refrigeration conditions, the refrigerant is chilled water, the general technical staff of this profession should be able to use this description to derive the logic of winter heating conditions.
  • Embodiment 1 is a control system of the end heat exchange device 3 of FIG. 2, comprising: a control point sensor 4, a brine control valve 5, a controller 6, and a refrigerant outlet temperature sensor 9.
  • the control point sensor is a room temperature sensor.
  • the brine control valve 5 may be an on-off valve or a regulating valve.
  • the brine control valve 5 in this embodiment must be a regulating valve.
  • the controller 6 adjusts the opening degree of the brine control valve 5 by PID calculation by the deviation of the room temperature from the set temperature, thereby adjusting the cooling capacity so that the room temperature is equal to the set temperature.
  • the air conditioner is selected too small, 2.
  • the set temperature is too low, 3.
  • the heat exchange surface is dirty, 4.
  • the regulating valve working opening is too small , adjustment instability.
  • the brine outlet temperature sensor 9 is used to limit the opening degree of the brine control valve 5 so that the chilled water outlet temperature is not lower than the limit value to ensure that the chilled water does not flow.
  • the limit value can be, but is not limited to, the rated chilled water outlet temperature.
  • the following control method can be adopted: the above PID adjustment control valve opening degree is still used, but it is obtained.
  • the Ts value may be inconsistent.
  • the coolant outlet temperature is 12.0 ° C, but in some equipment, in order to avoid excessive coolant pressure drop, The refrigerant outlet temperature may be greater than 12.0 ° C.
  • the chilled water inlet temperature is not a fixed value, so Ts can be treated in the following ways:
  • Ts is equal to the chilled water inlet temperature plus temperature difference.
  • the method is simple to implement, the chilled water circulation efficiency is high, and the accuracy of the water outlet temperature sensor is low, which is a preferred method.
  • Equal flow method It can be obtained from Fig. 4.
  • the flow rate is constant, the refrigeration capacity is different under different chilled water inlet temperatures, so that the chilled water outlet temperature of different chilled water inlet temperatures at a certain flow rate can be converted as the Ts value.
  • the method is more complicated to implement and the chilled water circulation efficiency is lower.
  • Ts is a fixed value. The method is simple to implement, the chilled water circulation efficiency is low, the working range is small, and the flow control capability is lost as the chilled water inlet temperature rises.
  • the inlet water temperature sensor is not required at each end heat exchange device, but the communication interface is configured on the controller, and the brine delivery temperature sensor 10 is provided at a typical position of the pipe network, and the upper control system
  • Each end heat exchange device Ts is calculated from the brine delivery thermometer and given by communication. It is also possible to specify only the coolant delivery temperature, and each controller derives the Ts value from its own set temperature difference.
  • the typical location of the pipe network can be the main water supply pipe or the branch pipe.
  • the above communication interface can use common communication protocols such as Modbus, BACnet, Lontalk, M-Bus, KNX, etc., can also use a custom protocol, the communication medium can be twisted pair, fiber, or even wireless communication such as Zigbee, Wifi.
  • common communication protocols such as Modbus, BACnet, Lontalk, M-Bus, KNX, etc.
  • the communication medium can be twisted pair, fiber, or even wireless communication such as Zigbee, Wifi.
  • the terminal heat exchange device 3 may also be a fresh air processor, and the control point sensor 4 may adopt a fresh air outlet temperature sensor. It may also be a dehumidifier, in which case the control point sensor 4 may employ an indoor humidity sensor.
  • Embodiment 2 is a control system in Fig. 2 when the end heat exchange device 3 is a fresh air handler in a winter heating system.
  • the minimum opening of the brine control valve In order to prevent the heat exchanger from being too cold and cracked, in the prior art, it is common practice to set the minimum opening of the brine control valve to ensure a minimum flow of the brine. However, because the pressure difference between the inlet and outlet of the brine is not fixed, or the flow is too large, energy is wasted, or the flow rate is too small, and the heat exchanger is frozen.
  • the opening degree control of the brine control valve not only adopts the logic described in Embodiment 1, but also causes the brine outlet temperature to be lower than the limit value Ts, and the temperature of the brine outlet is controlled to be higher than the antifreeze. Set the value to ensure that the heat exchanger does not freeze.
  • the antifreeze setting value can be a fixed value or a change value, which is given by the upper system according to the outdoor temperature.
  • Embodiment 3 is a refrigerant circuit control system of the heat pump unit 13 in the water ring heat pump system of Fig. 5, and the present invention does not relate to the control of other components of the heat pump unit.
  • the brine outlet temperature is controlled to ensure the flow rate, and the brine outlet temperature can be obtained by the following formula:
  • Embodiment 4 is an optimization of the control mode of the brine control valve in Embodiment 1.
  • the number and speed of the pump also change, so the pressure difference between the inlet and outlet of the brine is changed. This causes the refrigerant flow to fluctuate.
  • a constant pressure difference valve is often used to maintain a constant pressure difference between the inlet and outlet of the brine, and a control valve having a certain valve weight is selected, which is costly and has a large resistance loss.
  • a cascade adjustment method is adopted, and an indoor air conditioner is taken as an example.
  • the physical quantity is controlled to room temperature
  • the physical quantity target value is a room temperature set value
  • the deviation between the room temperature and the room temperature set value is first adjusted by the main PID.
  • the target value of the brine outlet temperature is calculated, and then the deviation between the current coolant outlet temperature and the target temperature of the brine outlet temperature is calculated, and the opening degree of the brine control valve is calculated by the secondary PID regulator.
  • the target value of the coolant outlet temperature output by the primary PID regulator should not be lower than Ts.
  • this embodiment can improve the dynamic characteristics, speed up the response, and enhance the anti-interference ability.
  • Embodiment 5 refers to a method of measuring the amount of heat exchange that can be used in the end heat exchange device 3 of Fig. 2.
  • the prior art measurement methods include: a) collecting the temperature difference between the inlet and outlet water and the water flow rate, and calculating the calorific value according to the specific heat. b) Calculate the heat exchange amount according to the air volume of the fan, the switch (switch valve) or the opening degree (regulating valve) of the brine control valve.
  • the method is more accurate but costly.
  • the method cost is low, but the flow rate changes due to the inconsistent pressure difference between the inlet and outlet of the brine, so that the calculation error of the heat exchange amount is large.
  • only the b method is improved, and the heat exchange condition of the heat exchanger characterized by the chilled water outlet temperature is utilized to improve the accuracy.
  • the relationship between the cooling capacity and the chilled water outlet temperature is plotted in Fig. 7. If the air volume of the fan 8 is adjustable, the relationship between the cooling capacity at different air volumes and the chilled water outlet temperature is also plotted. It can be seen from Fig. 7 that the cooling capacity can be calculated according to the coolant outlet temperature and the air volume; the total cooling heat value can be obtained by integrating the cooling capacity by time, which can be used for metering and billing.
  • the influence of the inlet air temperature on the heat exchange amount is not considered.
  • the heat exchange amount can be corrected according to the inlet air temperature.
  • Embodiment 6 is directed to a control system of an indoor air conditioner with adjustable air volume, and the air volume adjustment can be adjusted in multiple stages by using a single-phase tap type motor, or can be steplessly adjusted by using a variable speed motor.
  • the ideal implementation in the prior art is that the air volume is linked with the opening of the brine control valve, for example, the control valve opening degree is 0% to 100% corresponding to the air volume 60. % ⁇ 100%.
  • the control valve opening has a small flow rate. At this time, if the air volume is too small, the air supply temperature difference is large, which affects the comfort. For example, when the valve opening degree is 50%, the refrigerant flow rate may still reach 100%. If the air volume is reduced to 80%, the ratio of the cooling capacity/air volume is greater than the rated working condition, and the air supply temperature difference is increased.
  • the cooling capacity can be calculated; if the cooling capacity/air volume ratio is calculated, if the value is greater than the rated working condition, the supply air temperature difference is also greater than the design working condition, and the air volume should be increased. .
  • Ts is the rated chilled water outlet temperature. When the chilled water outlet temperature is less than or equal to this temperature, the air volume must be 100%, Fl is the minimum air volume, and Tl is the minimum air volume chilled water outlet temperature. When the chilled water outlet temperature is greater than or equal to Tl, the air volume must be Fl.
  • a simplified method can also be used when the fan air volume is stepped, as shown in Figure 9.
  • Fm is the mid-range air volume
  • Fl is the low-speed air volume.
  • the chilled water outlet temperature has a dead zone of Tb1 and Tb2. In the dead zone, the air volume is not shifted.
  • the outlet temperature may also be the outlet temperature target value.
  • the influence of the inlet air temperature on the heat exchange amount is not considered.
  • the air volume control value can be corrected according to the inlet air temperature.
  • Embodiment 7 is a calibration method of the brine outlet temperature sensor 9 of the end heat exchange device 3 of Fig. 2. In use, the temperature sensor will produce drift. In the prior art, in order to ensure the accuracy, the sensor must be recalibrated and returned to the factory at regular intervals, and the cost is high.
  • a reference sensor is disposed in a typical position of the pipe network such as a brine delivery trunk, a brine delivery branch pipe, and the like, such as the brine delivery temperature sensor 10 in FIG.
  • the pump 2 is turned on to make the brine in a circulating state
  • the fan 8 is turned off to be in a no-load state
  • the large-load coolant control valve 5 is opened.
  • the heat exchange amount of the heat exchanger 7 is approximately zero, and the brine is cooled.
  • the outlet temperature is approximately the coolant delivery temperature, and the reading of the temperature sensor 10 can be used to calibrate the coolant outlet temperature sensor 9.
  • the brine delivery temperature should be kept as constant as possible, and the brine circulation should be as large as possible.
  • Embodiment 8 is a control method of the carrier carrying pressure in the central air conditioning system of Fig. 2.
  • the maximum flow rate of each end heat exchange device is controlled, and no overcurrent phenomenon occurs.
  • the pump's delivery energy is consumed by the throttling of the brine control valve, or the pressure is too low, resulting in insufficient flow of some end heat exchange equipment.
  • the opening degree signal of the brine control valve of each end heat exchange device is collected. If all the control valve opening degrees are less than 100%, the pressure difference between the inlet and outlet of the refrigerant at each end heat exchange device is If there is excess, the lift of the pump can be reduced. When the opening of a certain control valve reaches 100%, the pressure difference between the inlet and outlet of the brine is insufficient, and the lift of the pump needs to be increased.
  • the head of the pump is minimized while ensuring the heat exchange capacity of each end heat exchange device.
  • an appropriate dead zone can be set, such as when all the control valve opening degrees are less than 80%, the pump head is reduced.
  • the highest head can be set to avoid excessive head lift caused by failure of individual end heat exchange equipment.
  • the appropriate adjustment rate can be set to avoid the oscillation of the head change too fast.
  • the lift adjustment of the pump increases the disturbance of the system. Therefore, the end heat exchange device can achieve better results by using the cascade adjustment method in Embodiment 4.
  • the pump head can be closed-loop adjusted by setting the pressure sensor. Because of the correlation between the head and the flow of the centrifugal pump, the flow can be adjusted by setting the flow sensor to adjust the head indirectly.
  • the speed open-loop adjustment can also be used directly.
  • Embodiment 9 is a control method of the coolant delivery temperature in the central air conditioning system of Fig. 2. Taking the chiller as an example, each time the chilled water supply temperature is increased by 1 °C, the cooling efficiency can be increased by 3%-5%, but the cooling capacity of the end heat exchange equipment is reduced by 5% ⁇ 10%. If the chilled water supply temperature is to be increased, the heat exchange capacity of all end heat exchange equipment must be rich.
  • the chilled water outlet temperature can characterize the cooling capacity.
  • the cooling capacity is less than the rated value (for example, the cooling capacity when the chilled water outlet temperature is equal to Ts is taken as the rated value). Therefore, when the chilled water outlet temperature of all the end heat exchange devices is greater than Ts, the chilled water supply temperature can be increased. If the chilled water outlet temperature of a terminal heat exchange device is equal to Ts, and the cooling capacity is still insufficient, the chilled water supply temperature must be lowered to increase the cooling capacity of the end heat exchange equipment.
  • the chilled water supply temperature is the highest (even if the chiller is the most energy-efficient) while ensuring the heat exchange capacity of each end heat exchange device.
  • an appropriate dead zone can be set. For example, when the chilled water outlet temperature of all the end heat exchange devices is greater than Ts+1 °C, the chilled water supply temperature is increased.
  • the chilled water has different influent temperatures, and the required chilled water flow rate is different.
  • the chilled water flow only needs 57% of the rated flow, such as 8 ° C water
  • chilled water flow requires 68% of the rated flow.
  • the chilled water supply temperature is increased, and the chilled water circulation volume needs to be increased.
  • the chilled water supply temperature is lowered, and the chilled water circulation is reduced.
  • the above control method only provides the necessary conditions for increasing the temperature of the chilled water supply.
  • the power consumption of the chiller under different working conditions and the power consumption of the pump under different circulation quantities should be calculated.
  • An example is calculated as follows:
  • the secondary pump variable flow system the current chiller power consumption is 200kw, 7 °C water, according to the chiller performance curve, when the water is increased to 8 °C, the same cooling capacity, power consumption is reduced to 190kw.
  • the current secondary pump consumes 15kw. According to the current performance curve of each end heat exchange equipment, the total chilled water circulation is increased by 15% compared to 7°C when it is increased to 8°C. Using the cubic principle of closed system power and flow, it is estimated that the water is increased to 8 °C, and the power consumption of the chilled water pump is
  • the minimum flow rate of the chiller is generally required to be about 50% of the rated flow.
  • the end is controlled. Over-current of the heat exchange equipment, when the system load rate is 50% ⁇ 75%, the flow rate of the chiller has reached the minimum flow, and the bypass valve 15 needs to be opened. At this time, it is better to increase the water supply temperature and increase the circulation amount.
  • the power of the chilled water pump at 8 ° C can be estimated as follows:
  • the chilled water outlet temperature can be replaced with a target value.
  • Embodiment 10 is an optimization based on Embodiment 9 when the following conditions are encountered: a) the chilled water outlet temperature of some end heat exchange equipment is less than or equal to Ts, but the cooling capacity still cannot meet the demand, and the chilled water supply temperature must be lowered. However, the chilled water outlet temperature of all other end heat exchange equipments is greater than or equal to Ts. b) The chilled water outlet temperature of some end heat exchange equipment is equal to Ts, which cannot increase the chilled water supply temperature; however, the chilled water outlet temperature of all other end heat exchange equipments is greater than Ts. At this time, these end heat exchange devices are called the 'bottleneck' of the water supply temperature control, which is an obstacle to further save the power consumption of the chiller.
  • the chilled water supply temperature is 7 ° C, which is adjusted to 8 ° C.
  • the Ts of the end heat exchange equipment is adjusted from 12 ° C to 13 ° C (set value) according to the isothermal difference method. However, for the end of the bottleneck heat exchange equipment, if the calculation result of the heat exchange amount method is 11.8 ° C, the Ts is controlled to exceed 11.8 ° C (overshoot value).
  • the current temperature of the chilled water supply is 8 °C.
  • the heat exchanger equipment at the end of the bottleneck is required to be lowered to 7 °C, but the state is still ignored.
  • the water supply of 8 °C is still used, but the Ts is controlled by the 13 °C (set value) to be 11.8 °C. Beyond the value).
  • the conversion of the heat exchange method can be converted according to the heat exchange capacity of the working conditions.
  • the example is as follows: the chilled water supply temperature is 12 ° C, which is adjusted to 13 ° C, and the Ts of the end heat exchange equipment is from 17 ° C according to the isothermal difference method. Adjust to 18 ° C (set value).
  • the end-of-bottle heat exchange equipment is calculated according to the heat exchange method such as the cooling capacity of the chilled water supply temperature of 7 °C, and the effective solution is not obtained (that is, the cooling at the chilled water supply temperature of 7 °C cannot be achieved regardless of the flow rate at this time).
  • the amount of overshoot can be converted to the cooling capacity at the chilled water supply temperature of 12 ° C.
  • the result is 16.9 ° C (that is, the cooling capacity at this time is equal to the cooling capacity at the chilled water supply temperature of 12 ° C).
  • the Ts of the end of the bottleneck heat exchange equipment will have a set value, an overshoot value, and the overshoot value will be the actual control.
  • the set value is still used as the standard for judging the chilled water supply temperature in Embodiment 9. If the chilled water outlet temperature is lower than the set value, it indicates that the cooling capacity is insufficient, and the chilled water supply temperature is too high; if the chilled water outlet temperature is higher than or equal to the setting The value indicates that the chilled water supply temperature has met the demand. At this time, the end heat exchange equipment is no longer a bottleneck, and the overrun control can be released.
  • This embodiment avoids the increase of the heat exchange capacity of the individual end heat exchange equipment, and affects the improvement of the refrigeration efficiency of the whole system, but the cost is to reduce the circulation efficiency of the chilled water, so it is more suitable for the number of heat exchangers at the end of the bottle diameter. Less (increased chilled water circulation flow) and located in a favorable loop (no need for a higher pump head).
  • Embodiment 11 is a differential pressure control method of the brine circulation branch in Fig. 12.
  • the ⁇ P pressure difference is too large, causing the opening degree of all the brine control valves of the branch to be small, resulting in control instability and valve core wear.
  • the branch control valve 16 is disposed on the branch main pipe.
  • the refrigerant control valves of all the end heat exchange devices of the branch are not fully opened, it indicates that the ⁇ P' is excessive, and the small branch control valve 16 is required to be closed.
  • the coolant control valve of a certain end heat exchange device in the branch is fully open but the flow rate is still insufficient, it indicates that ⁇ P' is insufficient, and the large branch control valve 16 is required to be opened.
  • an appropriate dead zone can be set. For example, when all the control valve opening degrees of the branch are less than 80%, the small branch control is turned off. Valve 16.
  • the state of the bypass control valve 16 can replace the state of all the refrigerant control valves of the branch, that is, if the branch control valve 16 has an opening degree of 100% but the flow rate is still insufficient. , indicating that the branch pressure difference ⁇ P is insufficient, it is necessary to increase the lift of the pump; if the opening control valve 16 opening degree is less than 100%, it means that the branch pressure difference ⁇ P is excessive, allowing the pump head to be lowered.
  • Embodiment 12 is a temperature sensor integrated control valve.
  • the coolant outlet temperature sensor of the terminal heat exchange device is installed and used together with the brine control valve.
  • the two are independently installed, the control valve is generally installed in the outlet pipe section, and the temperature sensor is used to ensure sensitivity.
  • it is a plug-in installation.
  • the valve body 17 is first connected to the inner joint 20, then the tee 21 is connected, and then the temperature sensor 22 is installed, and finally the duct 23 can be connected.
  • the installation workload is large, the cost is high, the joints are numerous, the leakage risk is large, and the installation size is also large.
  • the structure adopted in this embodiment is as shown in Fig. 14.
  • the valve body 17 of the control valve is provided with a threaded hole through which the temperature sensor 22 is fastened to the valve body 17, and the temperature sensitive element is inserted into the flow path. The above work is completed and leak tested before leaving the factory, so the pipe 23 can be directly connected at the site.
  • the embodiment uses less two parts of the inner joint and the three-way joint, and three threaded joints are omitted at the site, which greatly saves the workload and reduces the risk of leakage.
  • the regulating valve illustrated in Fig. 14 is a threaded joint. If it is a flange joint regulating valve, the prior art requires opening a hole in the pipe, soldering the temperature sensor base, and then screwing the temperature sensor. This embodiment can also achieve similar beneficial effects.
  • Embodiment 13 is an optimization of Embodiment 12, characterized in that the opening mounting position of the temperature sensor 22 is downstream of the spool 18. In practical applications, the fluid often carries impurities and is easily clogged at the inlet of the spool 18. After the blockage occurs, it needs to be cleaned up. If the temperature sensor 22 is mounted upstream of the spool, the probe inserted into the flow path will affect the cleaning operation.
  • Embodiment 14 is the circuit of the control valve shown in Embodiment 13.
  • the upper computer needs to adjust the opening degree of the control valve and collect the temperature of the coolant outlet.
  • analog signals are generally used to transmit data, so that the wiring is complicated and susceptible to interference.
  • the temperature sensor 22 is inserted into the control valve driver 19, and analog-to-digital conversion is completed.
  • the driver and the upper controller only need three connecting lines, +24V and 0V provide working power, DATA is the communication line, the upper controller transmits the valve opening command to the driver through digital communication, and reads the valve position opening signal and temperature sensor.
  • the readings are simple, the wiring is good, and the anti-interference performance is better.
  • the temperature sensor 22 is connected by a plug connector 24, which can flexibly disconnect the temperature sensor 22, and facilitates the repair and replacement of the temperature sensor 22.
  • the valve body 17 and the temperature sensor 22 can be installed first, and the temperature sensor 22 can be connected through the plug connector 24 when the driver 19 is mounted.
  • the temperature sensor is not limited to the 2-wire system, and a three-wire or four-wire thermal resistor may also be used.
  • a part of the logic of the upper controller may also be built in the driver. As described in Embodiment 4, the upper controller may only transmit the coolant outlet temperature control value, and the driver controls the valve opening degree through the PID adjustment to control the temperature sensor reading.
  • Embodiment 15 is the communication mode between the driver and the controller in Embodiment 14. Typically, there is a one-to-one connection between the controller and the drive. But in the following scenario, one controller needs to connect multiple drives:
  • the controller needs to be connected to a refrigeration control valve driver and a heating control valve driver.
  • a plurality of end heat exchange devices in one space share a single controller.
  • the indoor operation panel and the controller are separate structures. Thus, if one-to-one communication is still used, the wiring is too complicated and will occupy too many communication ports.
  • the bus method is used for communication. As shown in FIG. 16, each driver and the indoor operation panel are connected through a communication bus, and each device is configured with a different communication address, and the information can be exchanged without interference according to a predefined communication protocol.

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Abstract

一种中央空调载冷剂变温度变压力控制系统，由冷热源（1），泵（2），载冷剂输配管网，一个或多个末端换热设备（3），及连接各设备的通讯网络组成。其中末端换热设备（3）由控制点温度传感器（4），载冷剂出口温度传感器（9），载冷剂控制阀（5），控制器（6），热交换器（7），风机（8）组成。末端换热设备（3）通过载冷剂出口温度限制载冷剂流量。泵（2）的压力通过各末端换热设备（3）的载冷剂控制阀（5）的开度调节。载冷剂输送温度通过各末端换热设备（3）的载冷剂出口温度调节。

Description

中央空调载冷剂变温度变压力控制系统 技术领域
本发明涉及一种中央空调中载冷剂的温度及压力的控制方式。
背景技术
中央空调中泵的流量扬程，热交换器的换热能力，一般均按最大负荷选用，且留有裕量。但实际运行中，往往负荷率较低，因此如图 1 所示，在末端换热设备 3 处，一般安装有控制系统，载冷剂控制阀 5 可以是调节阀也可以是开关阀，控制器 6 根据控制点温度传感器 4 读数（一般为室内温度或出风温度）与设定值之间的偏差，关小（或关闭）开大（或开启）载冷剂控制阀，以调整载冷剂流量，进而调整换热量，使控制点温度达到设定值或在设定值附近波动。
但如仅调整末端换热设备 3 处的载冷剂流量，未对泵 2 进行适当的调节，将造成能量浪费。所以一般对泵 2 采用变频调速或台数调节，以使其流量扬程适应系统的需求。同时对载冷剂供给温度进行再设定，也可以减小冷热源 1 的功耗。但在现有技术中，上述调整没有完善的控制模型。
现有技术中对泵的流量扬程调节策略常用以下方式：恒温差方式与定压差方式。
恒温差方式控制载冷剂送回温差△ T 恒定，虽然逻辑简单，容易实现，但由于系统的流量与负荷的变化并不一致，导致末端欠流量或过流量。
定压差方式控制定压差点压差△ P 恒定。理论上定压差点应设于最不利环路，但是由于管网复杂，最不利环路并不是恒定不变的，很难找到理想的定压差点与压差值。
现在技术中对冷热源的载冷剂输送温度一般采用室外温度或负荷率的方式进行再设定，但因为各个末端换热设备处的换热需求不一，将造成调整不到位，或部分末端换热设备处换热能力不足。
ZL200810026583.X 揭示了一种可以同时控制空调温度和供回水温度差的中央空调系统，可控制流经空调末端设备的进、出水温度差和供水量，保证了水系统按需分配水量。但其方案仅局限于末端换热设备处，未提及整体系统的优化实施方案。且其末端换热设备控制系统采用了进水及出水两个温度传感器，增加了复杂性及成本。
技术问题
本发明主要解决的技术问题：在系统变流量动态运行中，在满足末端换热设备的换热量的前提下，最大限度地减小泵的输送压力、提高（在制冷时，如为供热则降低）载冷剂输送温度。
技术解决方案
本发明解决上述技术问题的技术方案包括以下：
1、 一种通过载冷剂间接传热的中央空调中末端换热设备的控制系统，包含：控制器，载冷剂控制阀。其特征在于：载冷剂控制阀的开度可调；具有载冷剂出口温度传感器；以载冷剂出口温度为控制参数之一，对载冷剂控制阀开度进行调节；控制器上具有通讯接口，载冷剂出口温度控制参数由通讯给定。
2、 如权利要求 1 所述控制系统，有一个控制物理量，及物理量目标值；其特征在于：据上述物理量及目标值，计算载冷剂出口温度目标值；调节载冷剂控制阀开度，使载冷剂出口温度达到目标值。
3、 如权利要求 1 所述控制系统，特征在于：末端换热设备有风量可调的风机；根据载冷剂出口温度，调整风机的风量。
4、 如权利要求 1 所述控制系统，特征在于：载冷剂控制阀阀体上开有孔，载冷剂出口温度传感器敏感元件通过该孔插入到流道中。
5、 如权利要求 4 所述控制系统，特征在于：上述温度传感器敏感元件安装在控制阀阀芯的下游。
6、 如权利要求 4 所述控制系统，特征在于：载冷剂控制阀驱动器内置温度采集电路，并连接载冷剂出口温度传感器；控制器对驱动器采用通讯方式控制。
7、 如权利要求 6 所述的控制系统，特征在于：载冷剂控制阀驱动器与载冷剂出口温度传感器的连接线有中间插接头。
8、 如权利要求 6 所述的控制系统，特征在于：控制器与驱动器之间接线有三根，其中两根是电源线，一根是通讯线。
9、 如权利要求 6 所述的控制系统，特征在于：控制器与驱动器之间的通讯采用总线方式。
10、 一种换热量计量方法，用于如权利要求 1 所述控制系统，其特征在于：根据载冷剂出口温度及风机风量，计算换热功率，将换热功率按时间累积，得到换热量。
11、 一种用于如权利要求 1 所述的控制系统的载冷剂出口温度传感器的使用中较准方法，其特征在于：在管网的典型位置设置载冷剂温度传感器作为基准传感器；使载冷剂处于循环状态；使末端换热设备处于无负荷状态，并开启载冷剂控制阀；用上述基准传感器读数较准末端换热设备的载冷剂出口温度传感器。
12、 一种载冷剂输送压力的控制方法，用于含冷热源、泵、载冷剂管路、采用如权利要求 1 所述控制系统的末端换热设备、通讯网络的中央空调中，其特征在于：当所有末端换热设备的载冷剂控制阀的开度均未全开时，降低载冷剂输送压力；当某末端换热设备的载冷剂控制阀已全开仍不能满足流量需求时，增加载冷剂的输送压力。
13、 一种载冷剂输送温度的控制方法，用于含冷热源、泵、载冷剂管路、采用如权利要求 1 所述控制系统的末端换热设备、通讯网络的中央空调中，其特征在于：当在制冷工况时，所有末端换热设备的载冷剂出口温度均大于其限定值时，提高载冷剂输送温度；当在供热工况时，所有末端换热设备的载冷剂出口温度均小于其限定值时，降低载冷剂输送温度；当在制冷工况时，某末端换热设备的载冷剂出口温度小于等于其限定值仍不能满足换热需求，降低载冷剂输送温度；当在供热工况时，某末端换热设备的载冷剂出口温度大于等于其限定值仍不能满足换热需求，提高载冷剂输送温度。
14、 如权利要求 13 所述的控制方法，其特征在于：在计算载冷剂输送温度时，忽略作为瓶颈的末端换热设备的状态；对上述作为瓶颈的末端换热设备的载冷剂出口温度限定值以等换热量法计算结果进行超越控制。
15、 一种支路压差控制方法，用于采用如权利要求 12 所述控制系统的中央空调载冷剂支路上，其特征在于：有一个开度可调的控制阀，安装于支路干管上；当此支路上所有如权利要求 1 所述的控制系统的载冷剂控制阀均未全开时，关小上述控制阀；当此支路上某个如权利要求 1 所述的控制系统的载冷剂控制阀已全开仍不能满足流量需求时，开大上述控制阀。
有益效果
a) 控制载冷剂不过流，避免了泵的输送能量的浪费。
b) 防止冬季新风换热器被冻裂。
c) 无需安装载冷剂进口温度传感器，节省成本。
d) 通过串级调节，避免了因为管路压差变化引起载冷剂流量变化，造成调节振荡失稳。
e) 在控制阀小开度范围内调节时，控制更稳定。
f) 对阀权度的要求低，减小系统阻力。
g) 在载冷剂流量，风量联合调节时，避免送风温差过大。
h) 减少安装工作量，节省成本，减少泄漏危险，减小安装尺寸。
i) 不影响杂质堵塞的清理。
j) 减少接线工作量，方便安装维修，抗干扰，扩展性强。
k)提高计量精度。
l)节省了较准成本。
m)保证末端换热设备流量需求的前提下，最大限度节省泵的耗能。
n) 在保证末端换热设备换热能力的前提下，最大限度提高冷热源的效率。
o) 以增加流量补偿个别末端换热设备的代价，提高整个系统冷热源的效率。
p)避免某支路因载冷剂进出口压差过大，末端换热设备的控制阀均在小开度下运行，造成控制失稳、节流噪音及阀芯磨损。
Description Of Drawings
图 1 ：传统变流量中央空调系统
1. 冷热源 2. 泵 3. 末端换热设备 4. 控制点传感器 5. 载冷剂控制阀 6. 控制器 7. 热交换器 8. 风机
图 2 ：载冷剂变温度变压力控制中央空调系统
1. 冷热源 2. 泵 3. 末端换热设备 4. 控制点传感器 5. 载冷剂控制阀 6. 控制器 7. 热交换器 8. 风机 9. 载冷剂出口温度传感器 10. 载冷剂输送温度传感器
图 3 ： 7 ℃ 进水时，制冷量及冷冻水出口温度与冷冻水流量关系图
图 4 ：不同进水温度时，制冷量与冷冻水流量关系图
图 5 ：水环热泵系统
1. 冷热源 2. 泵 5. 载冷剂控制阀 6. 控制器 7. 热交换器 8. 风机 9. 载冷剂出口温度传感器 11. 蒸发器 12. 压缩机 13. 热泵单元
图 6 ：室内温度→载冷剂出口温度→载冷剂控制阀的串级调节原理图
图 7 ：不同风量时，制冷量与冷冻水出口温度关系图
图 8 ：风量随冷冻水出口温度调节示意图
图 9 ：有级调节时风量随冷冻水出口温度调节示意图
图 10 ：二次泵变流量系统
1. 冷热源 2. 泵（二次泵） 3. 末端换热设备 14. 一次泵
图 11 ：一次泵变流量系统
1. 冷热源 2. 泵（二次泵） 3. 末端换热设备 15. 旁通阀
图 12 ：载冷剂循环支路示意图
3. 末端换热设备 4. 控制点传感器 5. 载冷剂控制阀 6. 控制器 7. 热交换器 8. 风机 9. 载冷剂出口温度传感器 16. 支路控制阀
图 13 ：现有技术中控制阀与温度传感器分别安装结构图
17. 阀体 18. 阀芯 19. 驱动器 20. 内接 21. 三通 22. 温度传感器 23. 管道
图 14 ：温度传感器控制阀一体化结构图
17. 阀体 18. 阀芯 19. 驱动器 22. 温度传感器 23. 管道
图 15 ：温度传感器控制阀一体化电路图
19. 驱动器 22. 温度传感器 24. 插接头
图 16 ：末端换热设备控制系统接线示意图
6. 控制器 19. 驱动器 25. 室内操作面板
 本发明的实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
本说明书中中央空调不仅指夏季制冷系统，也包括冬季供热系统。同理冷热源可以是冷水机组，也可以是热泵热水机组、锅炉、热交换器等。载冷剂通常指的是水，也可以是卤水溶液及其它液体。本说明着重分析夏季制冷工况，载冷剂为冷冻水，本专业普通技术人员均应能通过本说明，推导出冬季供热工况运行逻辑。
实施例1是图2中末端换热设备3的控制系统，包含：控制点传感器4、载冷剂控制阀5、控制器6、载冷剂出口温度传感器9。以室内空调器为例，控制点传感器即为室温传感器。
现有技术中载冷剂控制阀5可以是开关阀，也可以是调节阀，为达到本发明的有益效果，本实施例中载冷剂控制阀5必须是调节阀。
现有的技术中控制器6通过室温与设定温度的偏差，通过PID运算，调节载冷剂控制阀5的开度，从而调节制冷量，使室温等于设定温度。
有以下几个原因，可能造成载冷剂流量超出额定流量：1.空调器选型过小，2.设定温度过低，3.热交换表面脏堵，4.调节阀工作开度太小，调节失稳。
如图3所示，冷冻水流量越大，制冷量随流量增长越是缓慢，冷冻水出口温度则随之下降。因此冷冻水流量过大，冷冻水循环效率（以单位流量换热量为指标）降低，徒增泵的能耗，对提高制冷量效果有限。
因此在本实施例中，采用载冷剂出口温度传感器9，限定载冷剂控制阀5开度，使冷冻水出口温度不低于限定值，来保证冷冻水不过流。限定值可以但不限于采用额定冷冻水出口温度。
对冷冻水出口温度的限制，可以采用以下控制方式：仍旧采用上述PID调节控制阀开度，但求得
Figure PCTCN2013082890-appb-I000001
S阀门动作速度
Ts冷冻水出口限定值
T当前冷冻水出口温度
a比例系数
当T<Ts时，强制以速度S关闭控制阀，当T>Ts时，限制开阀动作速度小于等于S。
每个末端换热设备的换热特性不同，Ts值有可能不一致，常规的设计，载冷剂出口温度为12.0℃,但是在某些设备上，为了避免过大的载冷剂压降，载冷剂出口温度有可能大于12.0℃.
在系统运行过程中，冷冻水进口温度并不是一个定值，因此Ts可以有以下几种处理方式：
1.等温差法：Ts等于冷冻水进口温度加上温差。本方法实现简单，冷冻水循环效率高，对出水温度传感器的精度要求较低，是优选方法。
2.等流量法：从图4可得，流量一定时，不同冷冻水进口温度下，制冷量不同，从而可以换算出一定流量下不同冷冻水进口温度的冷冻水出口温度，做为Ts值。本方法实现较复杂，冷冻水循环效率较低。
3.固定法：Ts为固定值。本方法实现简单，冷冻水循环效率低，工作范围较小，随冷冻水进口温度升高，将失去流量控制能力。
4.等换热量法，从图4可得，同样的制冷量，对应不同的冷冻水进水温度，所需的流量不同，从而换算出一定冷量下不同冷冻水进口温度的冷冻水出口温度，做为Ts值。本方法实现较复杂，其它缺点与固定法类似。
在本实施例中，每个末端换热设备处不需设置进水温度传感器，而是在控制器上配置通讯接口，并在管网典型位置设有载冷剂输送温度传感器10，上位控制系统从载冷剂输送温度计算出各个末端换热设备Ts，并通过通讯给定。也可以仅给定载冷剂输送温度，各个控制器再由自身的设定温差得出Ts值。
管网典型位置可以是供水总干管，也可以是支干管。
上述的通讯接口，可以采用常见的通讯协议，如Modbus，BACnet, Lontalk, M-Bus, KNX等，也可以采用自定义协议，通讯介质可以采用双绞线、光纤，甚至采用Zigbee, Wifi等无线通讯方式。
上述实施例中末端换热设备3也可以是新风处理机，此时控制点传感器4可以采用新风出口温度传感器。也可以是除湿机，此时控制点传感器4可以采用室内湿度传感器。
实施例2是图2中当末端换热设备3为冬季供热系统中新风处理机的控制系统。为了防止换热器温度过低而冻裂，现有技术中，通常做法是设置载冷剂控制阀的最小开度，保证最小的载冷剂流量。但是因为载冷剂进出口压差不固定，或造成流量过大、能量浪费，或造成流量过小、换热器结冻。
在本实施例中，载冷剂控制阀的开度控制不但要采用实施例1中所述的逻辑，使载冷剂出口温度低于限定值Ts，而且需控制载冷剂出口温度高于防冻设定值，以保证换热器不结冻。
防冻设定值可以是固定值，也可以是变化值，由上位系统根据室外温度，通过通讯给定。
实施例3是图5水环热泵系统中热泵单元13的载冷剂回路控制系统，本发明不涉及热泵单元其它部件的控制。
在现在技术中，较为理想的做法是，采用恒压差控制阀控制流量恒定，及电动开关阀与热泵单元联锁，成本较高，且流量不能调节。
本实施例控制载冷剂出口温度来保证流量，载冷剂出口温度可以用下式求出：
Figure PCTCN2013082890-appb-I000002
Ts载冷剂出口控制温度
Figure PCTCN2013082890-appb-I000003
压缩机负荷率如不可卸载，则为1.0
△T理论载冷剂进出口温差
Ti载冷剂进口温度
以上控制方式，压缩机非满载时，载冷剂流量也保持不变，如需在压缩机非满载运行时，按比例减小载冷剂流量，则可令Φ恒等于1.0。但应注意，当流量减小到一定程度时，须转为定流量控制，以避免管内流速过低，流态由紊流转为层流，换热系数急剧下降。
实施例4是针对实施例1中载冷剂控制阀控制方式的优化。在实际运行中，因为系统中其它末端换热设备的载冷剂控制阀的阀位是在不断变化的，泵的台数与转速也随之变化，因此载冷剂进出口压差是变化的，造成载冷剂流量随之波动。
在传统的PID控制方式下，以上持续不断的干扰将造成室温的波动，甚至控制失稳振荡。
同时，载冷剂进出口压差常常大于设计压差，造成控制阀有效调节区变小，易超调造成控制失稳振荡。
在现有技术中，常采用设置恒压差阀的方式，保持载冷剂进出口压差恒定，同时选择具备一定阀权度的控制阀，成本高昂，阻力损失大。
本实施例采用串级调节的方式，以室内空调器为例，参考图6，控制物理量为室温，物理量目标值为室温设定值，先由室温与室温设定值的偏差，经主PID调节器计算出载冷剂出口温度目标值，再由当前载冷剂出口温度与载冷剂出口温度目标值的偏差，经副PID调节器计算出载冷剂控制阀的开度。当然，如在实施例1中所述，主PID调节器输出的载冷剂出口温度目标值应不低于Ts。
因为载冷剂流量→载冷剂出口温度的传递环节的时间常数远小于载冷剂流量→室内温度环节，本实施例能改善动态特性，加快响应，增强抗干扰能力。
实施例5指可用于图2中末端换热设备3的换热量计量方法。现有技术的计量方式有：a）采集进出水温差及水流量，根据比热计算热值。b）根据风机的风量，载冷剂控制阀的开关（开关阀）或开度（调节阀），计算换热量。a方法较精确，但成本高。b方法成本低，但因为载冷剂进出口压差不一致造成流量的变动，使换热量的计算误差较大。本实施例仅对b方法进行改进，利用冷冻水出口温度所表征的热交换器换热情况，提高精度。
将制冷量与冷冻水出口温度的关系绘于图7，如果风机8风量可调，则将不同风量下的制冷量与冷冻水出口温度的关系也一同绘上。由图7可知，根据载冷剂出口温度及风量，可以计算出制冷量；将制冷量按时间积分，就可得到总制冷热值，可以用于计量计费。
本实施例未考虑进风温度对换热量的影响，实际应用中，可以根据进风温度对换热量进行修正。
实施例6针对的是风量可调的室内空调器的控制系统，风量调节可以采用单相抽头式电机多级可调，也可以采用变速电机无级可调。此类系统，如果需要对载冷剂流量与风量联合调节，现有技术中较理想的实现方式是风量与载冷剂控制阀开度联动，例如控制阀开度0%~100%对应风量60%~100%。
但是因为载冷剂进出口压差常常大于设计压差，造成控制阀开度小流量大，此时如果风量过小，送风温差大，影响舒适度。例如50%阀门开度时，制冷剂流量仍然可能达100%，如果风量减为80%，则制冷量/风量之比大于额定工况，送风温差加大。
如图7所示，根据载冷剂出口温度及风量，可以计算出制冷量；计算制冷量/风量比，此数值如大于额定工况，则送风温差也大于设计工况，应加大风量。
如果需要对制冷量/风量之比精确控制，就需要换热器详尽的性能数据，一般工程上要求不高，可以用简化的方法，如图8所示，Ts是额定冷冻水出口温度，显而易见，冷冻水出口温度小于等于此温度时，风量须为100%，Fl为最低风量，Tl为最低风量冷冻水出口温度，当冷冻水出口温度大于等于Tl时，风量须为Fl。
当风机风量为有级调节时，也可以采用简化方法，如图9所示。Fm为中档风量，Fl为低档风量，为避免风机频繁换档，冷冻水出口温度有Tb1，Tb2的死区，在死区内，风量不换档。
当载冷剂控制阀的开度调节采用实施例2所述的串级调节时，上述出口温度也可以采用出口温度目标值。
本实施例未考虑进风温度对换热量的影响，实际应用中，可以根据进风温度对风量控制值进行修正。
实施例7是图2中末端换热设备3的载冷剂出口温度传感器9的较准方法。在使用中，温度传感器会产生漂移，现有技术中，为保证精度，每隔一段时间，须对传感器回厂重新标定较准，成本较高。
本实施例在管网典型位置如载冷剂输送干管、载冷剂输送支干管等设置基准传感器，如图2中的载冷剂输送温度传感器10。实施较准时，开启泵2使载冷剂处于循环状态，关闭风机8使其处于无负荷状态，开大载冷剂控制阀5，此时热交换器7的换热量近似零，载冷剂出口温度近似为载冷剂输送温度，可以用载冷剂输送温度传感器10的读数较准载冷剂出口温度传感器9。
为减小载冷剂出口温度与载冷剂输送温度的偏差，在较准时，载冷剂输送温度应尽量保持不变，同时载冷剂循环量应尽量大。
实施例8是图2中央空调系统中载冷剂载送压力的控制方法。通过采用实施例1所述的末端换热设备控制系统，在实现系统变流量运行的同时，每个末端换热设备的最大流量得到控制，不会发生过流现象。但如果载冷剂的输送压力没有得到适当的控制，或压力过高造成泵的输送能量被载冷剂控制阀的节流白白消耗，或压力过低造成某些末端换热设备流量不足。
本实施例采集每个末端换热设备的载冷剂控制阀的开度信号，如果所有的控制阀开度都小于100%，说明每个末端换热设备处载冷剂进出口压差均是过剩的，则可以减小泵的扬程。当某个控制阀开度达100%流量仍不足时，说明载冷剂进出口压差不足，需要提高泵的扬程。
通过以上控制方式，在保证每一个末端换热设备的换热能力的同时，使泵的扬程最小。
在应用中，考虑到控制阀的线性特性及控制的稳定性，可以设定适当的死区，如当所有的控制阀开度都小于80%时，才减小泵的扬程。
在实际应用中，可以设置最高扬程，避免个别末端换热设备的故障导致扬程过高。同时可设置适当的调节速率，以避免扬程变化过快产生振荡。
水泵的扬程调整，增加了系统的扰动。因此末端换热设备如采用实施例4中的串级调节方法可以达到更优的效果。
水泵扬程可以采用设置压力传感器的方式进行闭环调节，因为离心水泵的扬程与流量的相关性，也可以采用设置流量传感器的方式调节流量，从而间接调节扬程；也可以直接采用转速开环调节。
实施例9是图2中央空调系统中载冷剂输送温度的控制方法。以冷水机组为例，每提高冷冻水供水温度1℃，可以提高制冷效率3%-5%，但是末端换热设备制冷量降低5%~10%。如果要提高冷冻水供水温度，所有末端换热设备的换热能力须有富裕。
从图3可以看出，冷冻水出口温度可以表征制冷量大小，当冷冻水出口温度大于Ts时，制冷量小于额定值（如以冷冻水出口温度等于Ts时的制冷量作为额定值）。因此当所有末端换热设备的冷冻水出口温度均大于Ts时，可以提高冷冻水供水温度。如某个末端换热设备的冷冻水出口温度等于Ts时，制冷量仍不足，则须降低冷冻水供水温度以提高末端换热设备的制冷量。
通过以上控制方式，在保证每一个末端换热设备的换热能力的同时，使冷冻水供水温度最高（即使冷水机组最节能）。
在应用中，考虑到控制的稳定性，可以设定适当的死区，如当所有末端换热设备的冷冻水出口温度均大于Ts+1℃时，才提高冷冻水供水温度。
从图4可以看出，相同的制冷量时，冷冻水的进水温度不同，所需要的冷冻水流量不同。比如80%额定制冷量时，如7℃进水，冷冻水流量只需额定流量的57%，如8℃进水，冷冻水流量需额定流量的68%。可见，提高冷冻水供水温度，冷冻水循环量需加大，相反降低冷冻水供水温度，冷冻水循环量减小。
因此以上控制方式仅提供了提高冷冻水供水温度的必要条件，实际应用时，是否提高供水温度，应计算冷水机组的在不同工况下的功耗及水泵在不同循环量下功耗来决定。举例计算如下：
如图10所示的二次泵变流量系统，当前冷水机组功耗为200kw，7℃进水，根据冷水机组性能曲线，当提高到8℃进水,同样制冷量，功耗降为190kw。
当前二次泵功耗15kw，根据当前每台末端换热设备的性能曲线，统计当提高到8℃进水，总的冷冻水循环量需比7℃时提高15%。用闭式系统功率与流量的三次方原理，估算出提高到8℃进水，冷冻水泵功耗为
Figure PCTCN2013082890-appb-I000004
因为190+23＜200+15，所以提高到8℃供水温度较7℃供水节能。
再举例如图11所示的一次泵变流量系统，为避免冷水机组的换热恶化，各厂商一般要求冷水机组的最低流量为额定流量的50%左右，在应用本发明后，由于控制了末端换热设备的过流，在系统负荷率在50%~75%之时，冷水机组流量就已达到最低流量，需开启旁通阀15。此时提高供水温度，增加循环量有更佳的效益。
假设其它条件与上例相同，8℃供水时冷冻水泵的功率可以如此估算：
Figure PCTCN2013082890-appb-I000005
ß为冷水机组侧压降占系统总压降的百分比。假设ß＝0.1，得结果约为19kw。190+19 < 200+15
以上计算仅证明8℃供水较7℃供水节能，但在8℃是否为最节能的供水温度，还需要更多的评估。
为避免供水温度过低或过高，实际应用中可以设置合适的上下限。
在末端换热设备采用实施例4所述的串级调节时，冷冻水出口温度可以用目标值代替。
实施例10是在实施例９基础上的优化，当遇到下列情况：a）某些末端换热设备的冷冻水出口温度小于等于Ts，但制冷量仍不能满足需求，须降低冷冻水供水温度；但其它所有末端换热设备的冷冻水出口温度均大于等于Ts。b）某些末端换热设备的冷冻水出口温度等于Ts，无法提高冷冻水供水温度；但其它所有末端换热设备的冷冻水出口温度均大于Ts。此时这些末端换热设备称之为供水温度控制的'瓶颈'，是进一步节省冷水机组功耗的障碍。
本实施例在按照实施例9的逻辑进行供水温度控制时，不考虑瓶颈末端换热设备的状态，显然因此可以采用更高的供水温度，节省了冷水机组的功耗，但将造成瓶颈末端换热设备的换热量不足，因此本实施例对瓶径末端换热设备的Ts采用等换热量法进行超越控制，通过提高流量弥补冷冻水进水温度过高所造成的换热量不足。例如：
1、冷冻水供水温度为7℃，将其调整为8℃，末端换热设备的Ts按等温差法从12℃调整为13℃（设定值）。但对于瓶颈末端换热设备，等换热量法计算结果为11.8℃，则其Ts被超越控制为11.8℃（超越值）。
2、当前冷冻水供水温度8℃，瓶颈末端换热设备要求降低到7℃，但忽略其状态，仍采用8℃供水，但其Ts由13℃（设定值）被超越控制为11.8℃（超越值）。
3、等换热量法的换算可以按相对工况换热量换算，举例如下：冷冻水供水温度为12℃，将其调整为13℃，末端换热设备的Ts按等温差法从17℃调整为18℃（设定值）。瓶径末端换热设备如按7℃冷冻水供水温度下的制冷量等换热量法计算，得不到有效解（即无论此时流量多少，都无法达到7℃冷冻水供水温度下的制冷量），此时超越值可按12℃冷冻水供水温度下的制冷量换算，结果为16.9℃（即此时的制冷量等于12℃冷冻水供水温度下的制冷量）。
实施超越控制后，瓶颈末端换热设备的Ts将有一个设定值，一个超越值，超越值起实际控制作用。设定值仍作为实施例9中判断冷冻水供水温度的标准，如冷冻水出口温度低于设定值，表明制冷量不足，冷冻水供水温度过高；如冷冻水出口温度高于等于设定值，表明冷冻水供水温度已满足需求，此时该末端换热设备不再是瓶颈，可以解除超越控制。
本实施例避免了因个别末端换热设备的换热量不足，而影响整个系统制冷效率的提高，但其代价是降低了冷冻水的循环效率，因此比较适用于瓶径末端换热设备数量较少（增加的冷冻水循环流量较少），且位于有利环路的情况（不需较高水泵的扬程）。
实施例11是图12中的载冷剂循环支路的压差控制方法。作为有利回路的载冷剂循环支路，往往△P压差过大，造成本支路的所有载冷剂控制阀的开度偏小，造成控制失稳、阀芯磨损。
本实施例在支路干管上设置支路控制阀16，当本支路所有末端换热设备的载冷剂控制阀均未全开，说明△P'过剩，需关小支路控制阀16。当本支路中某末端换热设备的载冷剂控制阀已全开但流量仍不足时，说明△P'不足，需开大支路控制阀16。
与实施例8类似，考虑到控制阀的线性特性及控制的稳定性，可以设定适当的死区，如当本支路所有的控制阀开度都小于80%时，才关小支路控制阀16。
在实施例8中应用本实施例时，则支路控制阀16的状态可替代本支路所有载冷剂控制阀的状态，即若支路控制阀16开度达100%但流量仍不足时，代表支路压差△P不足，需提高泵的扬程；若支路控制阀16开度小于100%，代表本支路压差△P过剩，允许降低泵的扬程。
实施例12是一种温度传感器一体式控制阀。本发明中末端换热设备的载冷剂出口温度传感器都与载冷剂控制阀配套安装使用，在现有技术中，两者为独立安装，控制阀一般安装在出口管段，温度传感器为保证灵敏度，一般为插入式安装，如图13所示，阀体17先要连接内接20，再连接三通21，然后安装温度传感器22，最后才能连接管道23。安装工作量大，成本高，接头多，泄漏危险大，安装尺寸也较大。
本实施例采用的结构如图14所示，控制阀的阀体17上开有螺纹孔，温度传感器22通过该螺纹孔紧固在阀体17上，温敏元件插入到流道中。上述工作在出厂前就已完成并试漏，所以在现场直接连接管道　23就可使用。
对比图13，本实施例少用了内接与三通2个配件，现场少了3个丝扣接头，大大节省了工作量，减少泄漏危险。
图14示意的调节阀是螺纹接头，如果是法兰接头调节阀，现有技术需在管道上开孔，焊接温度传感器底座，然后螺纹紧固温度传感器。本实施例同样能达到类似有益效果。
实施例13是实施例12的优化，其特征是温度传感器22的开孔安装位置在阀芯18的下游。在实际应用中，流体常带有杂质，容易在阀芯18进口处堵塞。发生堵塞后，需要进行清理。如果温度传感器22安装在阀芯上游，则插入流道的探头将影响清理工作。
实施例14是实施例13所示控制阀的电路。在本发明中，上位机需调节控制阀的开度，并采集载冷剂出口温度值，在现有技术中，一般采用模拟信号来传递数据，如此接线较复杂，并且易受干扰。
本实施例如图15所示，温度传感器22接入控制阀驱动器19内，并完成模数转换。驱动器与上位控制器仅需三根连接线，+24V与0V提供工作电源，DATA是通讯线，上位控制器通过数字通讯方式向驱动器传送阀门开度指令，并读取阀位开度信号及温度传感器读数，接线简单，抗干扰性能较好。
本实施例中温度传感器22的接线采用了插接头24，可以灵活脱开温度传感器22的连接，方便温度传感器22的维修更换。当驱动器19与阀体17是分体结构时，阀体17及温度传感器22可以先行安装，驱动器19安装时可以通过插接头24连接温度传感器22。
本实施例中温度传感器不局限于2线制，也可以采用三线或四线制热电阻。驱动器内也可以内置上位控制器的部分逻辑，如实施例4中所述，上位控制器可以仅传送载冷剂出口温度控制值，驱动器通过PID调节控制阀开度，控制温度传感器读数。
实施例15是实施例14中驱动器与控制器之间的通讯方式。通常情况下，控制器与驱动器之间为一对一连接。但是在以下情景中，一个控制器需要连接多个驱动器：
1.四管制系统中，控制器需要连接一个制冷控制阀驱动器及一个供热控制阀驱动器。
2.一个空间内的多个末端换热设备共用一个控制器。
在有的应用中，室内操作面板与控制器是分体结构。这样，如果仍采用一对一通讯方式，接线太复杂，同时将占用控制太多的通讯端口。
本实施例采用总线方法通讯，同图16所示，将各个驱动器、室内操作面板通过通讯总线连接起来，各个设备配置不同的通讯地址，按照预定义的通讯规约，可以互不干扰地交换信息。
采用本实施例后，不同的控制部件只要遵循协议，就可以挂在总线上，系统的扩展性将大大增强。

Claims (15)

1. 一种通过载冷剂间接传热的中央空调中末端换热设备的控制系统，包含：控制器，载冷剂控制阀；其特征在于：
载冷剂控制阀的开度可调；
具有载冷剂出口温度传感器；
以载冷剂出口温度为控制参数之一，对载冷剂控制阀开度进行调节；
控制器上具有通讯接口，载冷剂出口温度控制参数由通讯给定。
2. 如权利要求 1 所述控制系统，有一个控制物理量，及物理量目标值；其特征在于：
根据上述物理量及目标值，计算载冷剂出口温度目标值；
调节载冷剂控制阀开度，使载冷剂出口温度达到目标值。
3. 如权利要求 1 所述控制系统，特征在于：
末端换热设备有风量可调的风机；
根据载冷剂出口温度，调整风机的风量。
4. 如权利要求 1 所述控制系统，特征在于：
载冷剂控制阀阀体上开有孔，载冷剂出口温度传感器敏感元件通过该孔插入到流道中。
5. 如权利要求 4 所述控制系统，特征在于：
上述温度传感器敏感元件安装在控制阀阀芯的下游。
6. 如权利要求 4 所述控制系统，特征在于：
载冷剂控制阀驱动器内置温度采集电路，并连接载冷剂出口温度传感器；
控制器对驱动器采用通讯方式控制。
7. 如权利要求 6 所述的控制系统，特征在于：
载冷剂控制阀驱动器与载冷剂出口温度传感器的连接线有中间插接头。
8. 如权利要求 6 所述的控制系统，特征在于：
控制器与驱动器之间接线有三根，其中两根是电源线，一根是通讯线。
9. 如权利要求 6 所述的控制系统，特征在于：
控制器与驱动器之间的通讯采用总线方式。
10. 一种换热量计量方法，用于如权利要求 1 所述控制系统，其特征在于：
根据载冷剂出口温度及风机风量，计算换热功率，将换热功率按时间累积，得到换热量。
11. 一种用于如权利要求 1 所述的控制系统的载冷剂出口温度传感器的使用中较准方法，其特征在于：
在管网的典型位置设置载冷剂温度传感器作为基准传感器；
使载冷剂处于循环状态；
使末端换热设备处于无负荷状态，并开启载冷剂控制阀；
用上述基准传感器读数较准末端换热设备的载冷剂出口温度传感器。
12. 一种载冷剂输送压力的控制方法，用于含冷热源、泵、载冷剂管路、采用如权利要求 1 所述控制系统的末端换热设备、通讯网络的中央空调中，其特征在于：
当所有末端换热设备的载冷剂控制阀的开度均未全开时，降低载冷剂输送压力；
当某末端换热设备的载冷剂控制阀已全开仍不能满足流量需求时，增加载冷剂的输送压力。
13. 一种载冷剂输送温度的控制方法，用于含冷热源、泵、载冷剂管路、采用如权利要求 1 所述控制系统的末端换热设备、通讯网络的中央空调中，其特征在于：
当在制冷工况时，所有末端换热设备的载冷剂出口温度均大于其限定值时，提高载冷剂输送温度；
当在供热工况时，所有末端换热设备的载冷剂出口温度均小于其限定值时，降低载冷剂输送温度；
当在制冷工况时，某末端换热设备的载冷剂出口温度小于等于其限定值仍不能满足换热需求，降低载冷剂输送温度；
当在供热工况时，某末端换热设备的载冷剂出口温度大于等于其限定值仍不能满足换热需求，提高载冷剂输送温度。
14. 如权利要求 13 所述的控制方法，其特征在于：
在计算载冷剂输送温度时，忽略作为瓶颈的末端换热设备的状态；
对上述作为瓶颈的末端换热设备的载冷剂出口温度限定值以等换热量法计算结果进行超越控制。
15. 一种支路压差控制方法，用于采用如权利要求 12 所述控制系统的中央空调载冷剂支路上，其特征在于：
有一个开度可调的控制阀，安装于支路干管上；
当此支路上所有如权利要求 1 所述的控制系统的载冷剂控制阀均未全开时，关小上述控制阀；当此支路上某个如权利要求 1
所述的控制系统的载冷剂控制阀已全开仍不能满足流量需求时，开大上述控制阀。
PCT/CN2013/082890 2012-09-04 2013-09-03 中央空调载冷剂变温度变压力控制系统 WO2014036935A1 (zh)

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