CN102279067B - Method and device for metering cooling capacity and heating capacity at tail end of fan coil of central air-conditioning system - Google Patents

Abstract

The invention proposes a method and device for measuring the cooling and heating capacity of a fan coil unit, which is based on the corrected relationship between the cooling and heating capacity under the actual working condition of the fan coil unit and the cooling and heating capacity under the nominal working condition. When measuring, it is only necessary to detect the wind speed state of the fan coil unit, the inlet water temperature and the inlet air temperature and humidity of the fan coil unit, and then the cooling capacity of the fan coil unit under actual working conditions can be obtained. That is, through the direct detection of easy-to-measure data, the accurate measurement of cold and heat can be realized indirectly. The invention combines the advantages of dual temperature on the water side, heat exchange on the wind side and time measurement, avoids the measurement of the water flow, thereby greatly reducing the cost of the metering device, improving the stability of the data and the service life of the device; The air state measurement of the air outlet section is replaced by the air inlet section, which makes the parameter measurement easier and easier to measure, and improves the operability of the engineering application of the measurement. At the same time, the influence of the water side and wind side parameters of the fan coil unit on the cooling and heat is considered and taken into account, which greatly improves the accuracy of measurement.

Description

A method and device for measuring cooling and heat at the end of a fan coil unit in a central air-conditioning system

technical field

The invention belongs to the technical field of energy metering and billing, and in particular relates to a cooling and heat metering technology at the end of a fan coil unit of a centralized air-conditioning system.

Background technique

Accurate measurement and reasonable billing of cold and heat in air-conditioning systems are not only beneficial to building energy conservation, but also beneficial to property management. Fan coil unit is the most common terminal form of central air conditioning system. At present, the cooling capacity measurement methods for fan coil air conditioning systems mainly include: timing method, water side dual temperature flow measurement method and wind side heat transfer measurement method.

The timing method is to accumulate the running time of the fan coil unit. It only considers the fan power at different wind speeds, and does not consider the changes in the chilled water flow rate and chilled water temperature of the fan coil unit. The measurement accuracy is low and the error is large, which is not conducive to the operation of the air conditioner. Reasonable charges.

The water-side dual-temperature flow measurement method requires a flowmeter and two thermometers at each end. This method is the most accurate measurement method in theory, and the key to ensuring its measurement accuracy is the flowmeter. The commonly used flow meters are mechanical, turbine, electromagnetic and ultrasonic, and the measurement accuracy and stability are quite different. Among them, the electromagnetic type and ultrasonic type with higher precision are more expensive. Therefore, although the measurement accuracy is high, the initial investment is large, the installation is complicated, and the maintenance is difficult.

The air side heat transfer measurement method calculates the fan coil unit heat transfer by measuring the air volume at the outlet of the fan coil unit and the enthalpy value of the inlet and outlet air. Although the high investment of water measurement is avoided, finding a measuring point position that can represent the average state of the air needs to be determined through experiments, which is not conducive to engineering applications.

Contents of the invention

In order to overcome the defects of the existing method for measuring the cooling capacity at the end of the fan coil unit of the central air conditioning system, the present invention provides a method and device for energy measurement at the end of the fan coil unit of the central air conditioner, which can not only accurately measure but also be economical and simple.

The technical solution adopted by the present invention to solve the technical problems is based on the following analysis:

In the cooling condition in summer, according to the heat balance, the heat transfer amount of the water side and the wind side of the fan coil unit is:

                            (1)

(1)

In the formula: ——The heat exchange rate of the fan coil unit, kW;

——水的质量比热，

=4.18kJ/(kg·℃)；

- mass specific heat of water,

=4.18kJ/(kg·℃);

——水的质量流量，kg/s；

——The mass flow rate of water, kg/s;

——冷冻水进水温度，℃；

- chilled water inlet temperature, °C;

- chilled water outlet temperature, °C;

——空气流量，kg/s；

——air flow rate, kg/s;

——空气进口焓值，kJ/kg；

—Enthalpy value of air inlet, kJ/kg;

—Enthalpy value of air outlet, kJ/kg.

Enthalpy efficiency of total cooling capacity is an important index to measure the heat transfer of fan coil units. Its definition is: when the air volume and water volume flowing through the coil unit under wet and cold conditions are definite values, the actual enthalpy difference of the air before and after the coil unit is different from that under standard conditions. The ratio of the air enthalpy difference. Right now:

                                                 (2)

(2)

——全冷量焓效率； In the formula:

——Enthalpy efficiency of total cooling capacity;

——与进水温度相同的盘管表面薄层饱和空气的焓值。

- Enthalpy of a thin layer of saturated air on the surface of the coil at the same temperature as the inlet water.

Substituting formula (2) into (1), the cooling capacity Q of the fan coil unit can be obtained as:

(3)

From the above formula, it can be seen that the air flow rate, total cooling enthalpy efficiency, and the enthalpy value of the inlet air and the air enthalpy at the same inlet water temperature are the main factors affecting the total cooling capacity of the fan coil unit. When the air volume at a certain gear and the water flow rate are determined, the enthalpy efficiency value of the total cooling capacity is a certain value. At this time, the cooling capacity of the fan coil unit is linearly proportional to the difference between the enthalpy value of the air at the air inlet and the enthalpy value of the saturated air at the same temperature as the inlet water. Therefore, the cooling capacity of the fan coil unit under actual working conditions can be expressed as:

                                              (4)

(4)

——实际工况下，风机盘管制冷量，kW； In the formula:

——Under actual working conditions, the cooling capacity of the fan coil unit, kW;

——Enthalpy value of inlet air under standard working conditions, kJ/kg;

——标准工况下，同进水温度的盘管表面饱和空气焓值，kJ/kg；

——Under standard working conditions, the enthalpy value of saturated air on the surface of the coil at the same inlet water temperature, kJ/kg;

——实际工况下，进口空气焓值，kJ/kg；      

——Enthalpy value of inlet air under actual working conditions, kJ/kg;

——实际工况下，同进水温度的盘管表面饱和空气焓值，kJ/kg。

——In actual working conditions, the enthalpy value of saturated air on the surface of the coil at the same inlet water temperature, kJ/kg.

The above analysis shows that by correcting the cooling capacity of the fan coil unit under the standard working condition, the cooling capacity of the fan coil unit under the actual working condition can be obtained. The key lies in mastering the enthalpy value of the inlet air and the saturated air enthalpy at the same temperature as the inlet water. The formula for calculating the enthalpy of moist air is:

   kJ/kg_干空气                            (5)

kJ/kg _{dry air} (5)

——空气温度，℃； In the formula:

——air temperature, °C;

——空气含湿量，kg/kg_干空气。其计算式为：

——air moisture content, kg/kg _{dry air} . Its calculation formula is:

                                              (6)

(6)

In the formula: B—atmospheric pressure, usually taken as 101325Pa;

——空气的饱和水蒸气分压力（根据空气温度可查表获得），Pa；

——The saturated water vapor partial pressure of the air (according to the air temperature can be obtained from the table), Pa;

——空气的相对湿度，%。

——The relative humidity of the air, %.

It can be seen that the cooling capacity measurement of the fan coil unit under the actual working condition can be realized by measuring the inlet air temperature, relative humidity and inlet water temperature, and then calculating according to the above formula.

In winter heating conditions, the analysis method is similar.

Based on the above analysis, the present invention proposes a fan coil cooling and heat measurement method based on the fan coil heat exchange principle and actual cooling and heat correction, which indirectly achieves accurate measurement of cooling and heat through direct detection of easy-to-measure data. The specific measurement steps are as follows:

First, the fan is turned on. If the water valve is also turned on, it is checked whether the user has paid the fee. If the fee has not been paid, the controller sends a command to close the water valve through the parallel output interface, and the monitoring program exits at the same time. If the user has paid the fee, the controller collects the status signals of the high, medium and low speed gears of the fan coil unit, and the timer records the effective running time TH, TM, TL of each gear of the fan coil unit;

Then, input the measured fan coil inlet air dry bulb temperature, relative humidity and inlet water temperature into the calculation program module, calculate according to the above formula, and obtain the fan coil unit heat transfer under actual working conditions;

Finally, the effective running time TH, TM, and TL of each gear are multiplied by the actual heat exchange, and then accumulated to obtain the cooling heat of the end user.

It can be seen from the above steps that when measuring, it is only necessary to detect the wind speed state of the fan coil unit, the inlet water temperature and the inlet air temperature and humidity of the fan coil unit, and then the accurate measurement of the cooling capacity can be realized. The principle is the correction relationship between the cooling and heating capacity under the actual working conditions of the aforementioned fan coil unit and the cooling and heating capacity under the nominal working conditions. By correcting the cooling capacity of the fan coil unit at the corresponding gear wind speed, the cooling capacity of the fan coil unit under actual working conditions can be obtained. The key lies in mastering the enthalpy value of the inlet air and the saturated air enthalpy at the same temperature as the inlet water. At normal temperature and pressure, air can be treated as an ideal gas. According to the ideal gas state equation, all state quantities of the studied air can be determined by any two independent air parameters. The air flow at the air inlet of the fan coil unit belongs to confluence, and its air flow uniformity is better than that at the outlet. Therefore, the measuring point does not need to be determined experimentally. Moreover, instruments for measuring air dry-bulb temperature and relative humidity are relatively abundant and economical. The enthalpy of saturated air at the coil surface is determined by measuring the temperature of the chilled water entering the coil. Water temperature sensors at room temperature are also widely used and economical. It can be seen that the measurement method proposed by the present invention combines the advantages of dual temperature on the water side, heat exchange on the wind side and time measurement, and avoids: 1) the measurement of the water flow. Therefore, the cost of the metering device is greatly reduced, and the stability of the data and the service life of the device are improved; 2) The measurement of the air state of the outlet section. Therefore, the parameter measurement is more convenient and easy to measure, and the engineering application operability of the measurement is improved. At the same time, compared with the time type, the influence of the water side and wind side parameters of the fan coil unit on the cooling and heat is calculated, which greatly improves the accuracy of measurement.

The above method is realized by adopting the terminal metering device of the fan coil unit of the central air-conditioning system, which is a terminal controller with functions of data collection, processing, storage, display and communication. The terminal controller is composed of a single-chip MCU with timing, data processing, calculation and storage functions, a display terminal, a power module and a communication module, as shown in Figure 1. MCU contains microprocessor MPU, serial/parallel input and output interface, program memory Flash, data memory, EEPROM, timer/counter, watchdog and other components. The MCU stores the calculation results, displays the cooling capacity consumed by the user through the display module, communicates with the upper management computer through the communication network, and transmits the relevant data to the management computer. The database is used for unified storage and management, which is convenient for query and printing. In this way, a central air-conditioning system fan coil terminal billing system with collection, processing, control and management functions is formed. The wiring principle of the terminal billing system is shown in Figure 2. If the terminal controller is not equipped with a communication module, it constitutes a simple terminal controller. The simple terminal controller can be used alone, and has the characteristics of applicability, economy, and easy installation.

、相对湿度

和进水温度

；风机盘管三档风速信号KH、KM、KL；各档位的有效运行时间TH、TM、TL。 The parameters measured by the metering device include: fan coil inlet air dry bulb temperature

,Relative humidity

and inlet water temperature

; Fan coil three-speed wind speed signal KH, KM, KL; Effective running time TH, TM, TL of each gear.

The content of the metering device pre-stored in the chip includes: the heat transfer Q under the high, medium and low gears corresponding to different fan coil models under standard working conditions (refer to the national standard "Fan coil unit GB/T19232-2003"); Partial pressure of saturated water vapor for different air temperatures; related formulas required for calculations in metering programs.

The metering device of the present invention uses the terminal controller directly installed on the fan coil at the end of the central air-conditioning system to simultaneously collect air intake parameters (dry bulb temperature, relative humidity) and fan coil inlet water temperature, and record the fan coil at the third gear. The running time under the wind speed, and according to the correction principle of the actual heat transfer of the fan coil unit, the internal calculator is used to calculate and display the actual air conditioning cooling capacity of the fan coil unit.

When billing the air conditioner, you only need to record the cooling capacity displayed by the metering device, and subtract it from the last meter reading data, which is the cooling capacity of the billing cycle, and multiply it by the charging unit price standard of the unit cooling capacity to get corresponding fees. So as to realize the metering and charging methods similar to electric meters and water meters. Users can also read the consumption by themselves and calculate the monthly air-conditioning fee to ensure the transparency and fairness of metering and billing.

Description of drawings

Fig. 1 Structural block diagram of the metering device at the fan coil end of the central air-conditioning system;

Figure 2 The schematic diagram of the wiring of the metering device at the fan coil end of the central air-conditioning system;

Fig. 3 The main program block diagram of metering and monitoring at the fan coil end of the central air-conditioning system;

Figure 4 The schematic diagram of the terminal controller circuit;

Figure 5 Schematic diagram of the analog input circuit.

Detailed ways

The present invention will be further described below in conjunction with the embodiments and accompanying drawings.

The circuit realization scheme of the present invention: the terminal billing device of the fan coil unit of the central air-conditioning system is a terminal controller with functions of data collection, processing, storage, display and communication. The terminal controller is composed of a single-chip MCU with timing, data processing, calculation and storage functions, a display terminal, a power module and a communication module, as shown in Figure 1. MCU contains microprocessor MPU, serial/parallel input and output interface, program memory Flash, data memory, EEPROM, timer/counter, watchdog and other components. If the terminal controller is not equipped with a communication module, it constitutes a simple terminal controller. The simple terminal controller can be used alone, and has the characteristics of applicability, economy, and easy installation.

等输入计算程序模块，按照所述计算公式，即获得实际工况下的风机盘管换热量

，其计算公式如下：  The monitoring program of the terminal controller is stored in the Flash memory, and is started to run by the fan opening signal. The controller collects the status signal of the water valve through the parallel input interface. When the water valve is closed by the user, the monitoring program exits; when the water valve is opened, it checks whether the user has paid the fee. If the fee has not been paid, the controller sends a command to close the water valve through the parallel output interface. , and the monitoring program exits. If the user has paid the fee, the controller collects the status signals of the high, medium and low speed gears of the fan coil unit, and the timer records the effective running time TH, TM, TL of each gear of the fan coil unit; bulb temperature ,Relative humidity and inlet water temperature

etc. input into the calculation program module, according to the calculation formula, the fan coil heat transfer heat under the actual working condition can be obtained

, its calculation formula is as follows:

                                              (4)

(4)

——实际工况下，风机盘管制冷量，kW； In the formula:

——Under actual working conditions, the cooling capacity of the fan coil unit, kW;

——Enthalpy value of inlet air under standard working conditions, kJ/kg;

——标准工况下，同进水温度的盘管表面饱和空气焓值，kJ/kg；

——Under standard working conditions, the enthalpy value of saturated air on the surface of the coil at the same inlet water temperature, kJ/kg;

——实际工况下，进口空气焓值，kJ/kg；      

——Enthalpy value of inlet air under actual working conditions, kJ/kg;

——实际工况下，同进水温度的盘管表面饱和空气焓值，kJ/kg；

——In actual working conditions, the enthalpy value of the saturated air on the surface of the coil at the same inlet water temperature, kJ/kg;

——风机盘管标准工况下的换热量，kW；

——The heat exchange rate of the fan coil unit under the standard working condition, kW;

Among them, the enthalpy value of the inlet air and the saturated air enthalpy value on the surface of the coil at the same inlet water temperature are calculated using the following formula for calculating the enthalpy of humid air:

kJ/kg _{dry air} (5)

——空气温度，℃； In the formula:

——air temperature, °C;

——空气含湿量，kg/kg_干空气；其计算式为：

——air moisture content, kg/kg _{dry air} ; its calculation formula is:

                                              (6)

(6)

In the formula: B—atmospheric pressure, usually taken as 101325Pa;

——空气的饱和水蒸气分压力（根据空气温度确定），Pa；

——the saturated water vapor partial pressure of the air (determined according to the air temperature), Pa;

——空气的相对湿度，%。

——The relative humidity of the air, %.

When billing the air conditioner, you only need to record the cooling capacity displayed by the metering device, and subtract it from the last meter reading data, which is the cooling capacity of the billing cycle, and multiply it by the charging unit price standard of the unit cooling capacity to get corresponding fees. So as to realize the metering and charging methods similar to electric meters and water meters. Users can read the consumption by themselves and calculate the monthly air-conditioning fee to ensure the transparency and fairness of metering and billing.

The wiring principle of the terminal billing system is shown in Figure 2. The single-chip MCU stores the calculation results, displays the cooling capacity consumed by the user through the display module, communicates with the upper management computer through the communication network, and transmits relevant data to the management computer. The database is used for unified storage and management, which is convenient for query and printing, thus forming a central air-conditioning system fan coil terminal billing system with functions of collection, processing, control and management.

The form is described in the detailed description of the specific embodiment. The block diagram of the monitoring program of the central air-conditioning system fan coil terminal billing device of the present invention is shown in FIG. 3 . When the user turns on any wind speed switch, the terminal controller starts to execute the monitoring program. The program first starts the timer in the controller (when the timer is full, interrupts the timing program to update the timer time), then collects the status signal of the third-speed wind speed switch, and makes a judgment: Is the wind speed switch set to low speed? If yes, start timer 1, otherwise judge whether the wind speed switch is set to medium speed, if yes, start timer 2, otherwise start timer 3; then the controller collects the status of the water valve, if the water valve is closed, it exits the monitoring program; if the water valve When it is turned on, the following operations are performed: the host computer inquires whether the user has paid the fee on time. If the fee has not been paid, the terminal controller will issue a command to close the water valve. , display, store, and upload to the upper management machine and other operations. In this embodiment, MCU adopts AT89S52 single-chip microcomputer of ATMEL company, communication module adopts MAX487E, liquid crystal display module adopts SG12864, power module adopts switching power supply. Through the necessary software and hardware design, the functions of fan coil energy consumption measurement, display and communication with the management computer (PC) are realized.

Fig. 4 is the circuit diagram of the present invention, and AT89S52 single-chip microcomputer has 4 8 quasi-bidirectional I/O interfaces P0, P1, P2, P3, each bit of each interface has output latch, output driver, input register. For each interface, byte input and output operations can be performed, and bit operations can also be performed. The 18th and 19th pins of the AT89S52 microcontroller are connected to the crystal oscillator, the 40th pin is connected to the Vcc terminal of the power module, and the 20th pin is connected to the GND terminal of the power module.

X5045 is a programmable control circuit integrating three functions of watchdog, voltage monitoring and serial EEPROM. Among them, the watchdog provides protection function for the system. When the system breaks down and exceeds the set time, the watchdog responds to the CPU through the RESET signal. The voltage monitoring function can protect the system from low voltage, when the power supply voltage drops below the allowable range, the system will reset until the power supply voltage returns to a stable value. X5045 and AT89S52 single-chip microcomputer adopt SPI bus interface mode. This interface circuit expands 4 kB serial EEPROM for AT89C52 single-chip microcomputer. Wind speed timer data. The minimum storage period of the internal data of the EEPROM of the X5045 is 100 years, and it can be erased and written more than 1 million times. As shown in the figure, the X5045 chip has a total of 8 pins, of which the 3rd and 8th pins are connected to +5V power supply, and the 4th pin is grounded; the chip select input terminal CS, the serial data output terminal SO, and the serial clock input terminal SCK , The serial data input terminal SI is connected with the 21, 22, 23, 24 pins of the P2 port of the AT89S52 single-chip microcomputer respectively; the reset output terminal RESET is connected with the 9th pin of the single-chip microcomputer.

As shown in Figure 4, R1~R3 are current limiting resistors, D1~D3 are rectifier diodes, and D4~D6 are reverse protection diodes. The third gear wind speed detection signal of the fan coil unit is input to the 1st, 2nd and 3rd pins of the P1 port of the AT89S52 microcontroller through the optocoupler TLP521-1. When any of the high, medium and low wind speed switches of the fan coil unit is turned on, the current limiting resistor and diode of the corresponding circuit are turned on, and the corresponding microcontroller pin is at low level (0), while the other two wind speed detection pins pin is high (1). The control signal of the fan coil water valve comes from the 5th pin of the P1 port of the AT89S52 single chip microcomputer. After the photoelectric isolation, the opening and closing control of the valve is realized through the relay J1. As shown in the figure, when the 5th pin is set high, the optocoupler is turned on, the relay J1 coil passes current, the electrical circuit of the water valve is turned on, and the water valve is closed; when the 5th pin is set low, the optocoupler is cut off, The electrical circuit of the water valve is shut off. The water valve state detection signal is input to the fourth pin of the P1 port of the AT89S52 microcontroller through the optocoupler TLP521-1.

和进水温度

传感器相连，经模数转换器转换为数字量后，输出到与D0-D7引脚相连的移位寄存器74HC165的A-H引脚端，再通过74HC165的Q引脚输出，并经光电隔离后接AT89S52单片机的P1口的第6引脚，将信号送入单片机中。ADC0809CCN的通道选择端ADD A、ADD B引脚通过光电隔离后接单片机P1口的7、8引脚，ADC0809CCN的地址锁存端ALE引脚和起动转换端START引脚通过光电隔离后都接到单片机P1口的12引脚，74HC165的时钟端CLK引脚、控制端SH/LD引脚通过光电隔离后分别接单片机P3口的14引脚、15引脚。 As shown in Figure 5, the IN0-IN2 pins of the input terminal of the analog-to-digital converter ADC0809CCN are respectively connected to the air dry bulb temperature of the fan coil unit. ,Relative humidity

and inlet water temperature

The sensor is connected, after being converted into a digital quantity by an analog-to-digital converter, it is output to the AH pin of the shift register 74HC165 connected to the D0-D7 pin, and then output through the Q pin of the 74HC165, and then connected to AT89S52 after optical isolation The 6th pin of the P1 port of the single-chip microcomputer sends the signal to the single-chip microcomputer. The ADD A and ADD B pins of the channel selection terminal of ADC0809CCN are connected to the 7 and 8 pins of the P1 port of the microcontroller through photoelectric isolation, and the ALE pin of the address latch terminal of ADC0809CCN and the START pin of the start conversion terminal are connected to The 12-pin of the P1 port of the single-chip microcomputer, the CLK pin of the clock terminal of the 74HC165, and the SH/LD pin of the control terminal are respectively connected to the 14-pin and 15-pin of the P3 port of the single-chip microcomputer after optical isolation.

The present invention adopts the liquid crystal display module SG12864. In the figure, the connection between the SG12864 and the AT89S52 single-chip microcomputer adopts the direct access method, that is, the liquid crystal display module is used as a memory or I/O device, and the single-chip microcomputer operates the liquid crystal display module by accessing the memory or I/O device. As shown in Figure 4, the 8-bit data lines DB0~DB7 of the display module are connected to the 32nd~39th pins of the P0 port of the AT89S52 microcontroller; the instruction/data selection line D/I, the read/write selection line R/W and the chip selection The signal lines CS1 and CS2 are respectively connected to the 25th, 26th, 27th, and 28th pins of the P2 port of the single-chip microcomputer; E is the enable signal line, which is connected to the NOR output of the 16th and 17th pins of the P3 port of the single-chip microcomputer.

The present invention adopts the MAX487E communication module produced by MAXIM Company to communicate with the upper computer. MAX487E is a differential balanced transceiver chip, which is a low-power transceiver used for conversion between TTL protocol and 485 protocol. It contains a driver and a receiver, adopts half-duplex communication mode, has 128 nodes, and is lightning-resistant , anti-static shock, limited slope drive and fault protection and other functions. The receiver output RO is connected to the 10th pin of the P3 port of the AT89S52 microcontroller, the driver input DI is connected to the 11th pin of the P3 port of the microcontroller, the driver output enable port is connected to the 13th pin of the P3 port of the microcontroller, and the receiver The output enable terminal is connected to GND.

The power module adopts switching power supply, input AC220V, output DC±5V, DC±12V.

Claims (3)

1. A method for measuring cold and heat at the fan coil end of a central air-conditioning system, the specific measurement steps are as follows: Step 1: The fan is turned on. If the water valve is also turned on, check whether the user has paid the fee. If the fee has not been paid, the controller sends a command to close the water valve through the parallel output interface, and the monitoring program exits at the same time; High, medium and low speed gear state signals of the duct fan, and the timer records the effective running time TH, TM, TL of each gear of the fan coil; Step 2: Input the measured fan coil inlet air dry bulb temperature, relative humidity and inlet water temperature into the calculation program module to obtain the fan coil unit heat transfer Q ^s under actual working conditions. The calculation formula is as follows: ${\mathrm{<span\; class="notranslate">\; Q</span>}}^{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}^{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$ In the formula: Q ^s ——under the actual working condition, the heat exchange rate of the fan coil unit, kW; i ₁ ——Inlet air enthalpy value under standard working conditions, kJ/kg; i _w ——Under standard working conditions, the enthalpy value of saturated air on the surface of the coil at the same inlet water temperature, kJ/kg;

——Enthalpy value of inlet air under actual working conditions, kJ/kg;

——In actual working conditions, the enthalpy value of the saturated air on the surface of the coil at the same inlet water temperature, kJ/kg; Q——the heat transfer rate of the fan coil unit under standard working conditions, kW; Among them, the enthalpy value of the inlet air and the saturated air enthalpy value on the surface of the coil at the same inlet water temperature are calculated using the following formula for calculating the enthalpy of humid air: i=1.01t+d(2500+1.84t)kJ/kg _{dry air} (5) In the formula: t—air temperature, ℃; d——air moisture content, kg/kg _{dry air} ; its calculation formula is:

In the formula: B—atmospheric pressure, usually taken as 101325Pa; P _{q b} —— saturated water vapor partial pressure of air, Pa;

— relative humidity of the air, %; Step 3: Multiply the effective running time TH, TM, and TL of each gear by the actual heat exchange capacity, and then accumulate and calculate to obtain the cooling heat of the end user. 2. a central air-conditioning system fan coil unit end cooling and heat metering device that realizes the method described in claim 1, it is a controller with data acquisition, processing, storage, display and communication functions; it is characterized in that: said The metering device includes a single-chip MCU with functions of timing, data processing, calculation and storage, a display terminal, a power supply module and a communication module; the MCU stores the calculation results, displays the cooling capacity consumed by the user through the display terminal, and communicates with the The upper management computer communicates, transmits the relevant data to the upper management computer, and uses the database for unified storage and management. 3. The cooling and heat metering device at the end of the fan coil unit of the central air-conditioning system according to claim 2, characterized in that: the MCU contains a microprocessor MPU, serial/parallel input and output interfaces, program memory Flash, data memory, EEPROM , timer/counter, and watchdog components; the program memory Flash pre-stores the heat exchange Q corresponding to the high, medium, and low gears of different fan coil unit models under standard working conditions, and the Q corresponding to different air temperatures Saturated water vapor partial pressure, there are related formulas required for calculation in the measurement program.

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