Annular circulation system based on natural gas verification

Abstract

The utility model discloses a loop circulation system based on natural gas verification. The loop circulation system comprises a loop unit, a temperature control unit, a flow control unit, a flow detection unit and a main control unit, natural gas circulates in the loop unit; the temperature control unit comprises a heat exchanger arranged on the loop unit and a cooling unit connected with the heat exchanger; the cooling unit comprises a hydraulic balance device, a refrigerating unit, a water return pipe group and a water outlet pipe group; a regulating valve and a compensating heater are arranged on the water outlet pipe group; a first return pipe group and a second return pipe group are arranged between the water outlet pipe group and the return pipe group; the flow detection unit comprises a working-grade standard flow meter and a detected flow meter which are arranged on the loop unit; the flow control unit comprises a circulating fan and a backflow regulator which are arranged on the loop unit; according to the system, the temperature, the pressure and the flow of the natural gas in the loop can reach the preset range quickly and accurately, the maintaining capability is high, the verification precision is high, and operation is easy.

Description

TECHNICAL FIELD

[0001] The utility model relates to natural gas testing equipment technical field, concretely relates to a kind of loop circulation system based on natural gas testing. BACKGROUND

[0002] According to relevant needs, all trade handover natural gas flow meter needs to be sent to natural gas flow meter testing agency for testing, and the testing agency currently adopts loop testing system for testing, and the main working principle of the loop testing system is as follows: according to the temperature, pressure and flow stability requirements in the testing process according to the testing procedure, natural gas is injected into the circulating process system, and when the required testing pressure is reached, the gas injection process is closed, the pressure is kept stable, and the gas medium of the loop system is also kept stable. Start the loop power equipment (circulating fan), and set the required testing flow according to the requirements of the testing procedure. However, in the existing loop testing system, the temperature of the pressurized gas is high, and if the gas is not cooled in time, the uncertainty of the measurement result will be increased, and the testing result obtained by the loop testing method will be inaccurate. SUMMARY

[0003] The utility model aims at providing a kind of loop circulation system based on natural gas testing, which can quickly and accurately control the temperature, pressure and flow of natural gas in the loop to be within the preset range, has strong holding capacity, high testing accuracy and simple operation.

[0004] To achieve the above object, the utility model adopts the following technical scheme:

[0005] A kind of loop circulation system based on natural gas testing, the control system includes loop unit, temperature control unit, flow control unit, flow detection unit and main control unit;Natural gas circulates in the loop unit;

[0006] The temperature control unit includes a heat exchanger arranged on the loop unit and a cooling unit connected with the heat exchanger, the cooling unit is used to control the tube side temperature of the heat exchanger, and the natural gas of the loop unit keeps stable temperature after passing through the tube side of the heat exchanger;

[0007] The cooling unit includes a hydraulic balance device, a refrigerating unit arranged on the primary side of the hydraulic balance device and a return water pipe group and a water outlet pipe group arranged on the secondary side of the hydraulic balance device, the return water pipe group injects cooling water in the heat exchanger into the hydraulic balance device, and the cooling water enters the refrigerating unit for cooling through the primary side of the hydraulic balance device, and then flows into the water outlet pipe group through the hydraulic balance device after cooling, and the water outlet pipe group injects the cooled water into the heat exchanger again for cooling operation;

[0008] A plurality of regulating valves are arranged in parallel on the outlet pipe group, a first return pipe group and a second return pipe group are arranged between the outlet pipe group and the return pipe group, the first return pipe group and the second return pipe group are arranged on both sides of the plurality of regulating valves; a compensation heater is arranged on the outlet pipe group, and the compensation heater is used for heating water in the outlet pipe group;

[0009] The flow detection unit comprises a working standard flowmeter arranged on the loop unit and a detected flowmeter, and the working standard flowmeter is used for calibrating the detected flowmeter.

[0010] The flow control unit comprises a circulating fan and a return flow regulator arranged on the loop unit, and the circulating fan and the return flow regulator circulate natural gas in the loop unit according to a preset flow range; the circulating fan comprises a high-speed explosion-proof motor and a fan body connected through a magnetic coupler, and the fan body is connected in series on the loop unit.

[0011] The temperature control unit, the flow control unit and the flow detection unit are electrically connected with the main control unit.

[0012] Preferably, the loop unit comprises a main loop pipeline and a loop inlet and a loop outlet arranged on one side of the main loop pipeline, a first valve is arranged in the loop inlet, and a second valve is arranged in the loop outlet; the loop inlet and the loop outlet are connected with the external natural gas pipeline and the main loop pipeline.

[0013] Preferably, a pressure control unit is arranged between the loop inlet and the external natural gas pipeline, and the pressure control unit is used for injecting natural gas in the external natural gas pipeline into the main loop pipeline through the loop inlet according to a preset pressure.

[0014] Preferably, two circulating fans and two heat exchangers are arranged, one circulating fan and one heat exchanger are connected in series as a group, and two groups are connected in parallel.

[0015] Preferably, first, second and third temperature transmitters are arranged at upper, middle and lower positions in the hydraulic balance device; an A1 water pipe joint and an A2 water pipe joint are arranged on a primary side of the hydraulic balance device, a water inlet end of the refrigeration unit is connected with the A1 water pipe joint through a first water inlet pipe group, and a water outlet end of the refrigeration unit is connected with the A2 water pipe joint through a second water inlet pipe group; a B1 water pipe joint and a B2 water pipe joint are arranged on a secondary side of the hydraulic balance device, the return pipe group is connected with the B1 water pipe joint, and the outlet pipe group is connected with the B2 water pipe joint.

[0016] Preferably, a constant pressure water supplement unit is arranged on the water return pipe group, and the constant pressure water supplement unit is used for ensuring the water pressure in the cooling unit; and the constant pressure water supplement unit is connected with the tap water pipe through the softened water module.

[0017] Preferably, when the flow of the primary side of the water balance device is equal to the flow of the secondary side of the water balance device, the temperature at the A1 water pipe joint is equal to the temperature at the B1 water pipe joint, and the temperature at the A2 water pipe joint is equal to the temperature at the B2 water pipe joint, at this time, the medium in the water balance device is relatively static, and the temperature stratification tends to be stable;

[0018] When the flow of the primary side of the water balance device is less than the flow of the secondary side of the water balance device, the temperature at the A1 water pipe joint is equal to the temperature at the B1 water pipe joint, and the temperature at the A2 water pipe joint is greater than the temperature at the B2 water pipe joint, at this time, part of the return water at the B2 water pipe joint participates in the water supply at the B1 water pipe joint, and the temperature in the water balance device gradually increases from top to bottom;

[0019] When the flow of the primary side of the water balance device is greater than the flow of the secondary side of the water balance device, the temperature at the A2 water pipe joint is equal to the temperature at the B2 water pipe joint, and the temperature at the A1 water pipe joint is greater than the temperature at the B1 water pipe joint, at this time, part of the return water at the A2 water pipe joint participates in the return water at the A1 water pipe joint, and the temperature in the water balance device gradually decreases from top to bottom.

[0020] Preferably, when the water pressure in the cooling unit is lower than 1.4 bar, the constant pressure water supplement unit is started to automatically supplement water, and the water supplement is automatically stopped when the water pressure reaches 1.5 bar.

[0021] In the utility model, the main control unit can control the whole system, and the working state of different components and the measured stable, pressure and other values are displayed, the man-machine interaction is strong, and the operation is convenient. The circulating fan and the backflow regulator can circulate the natural gas in the ring according to the set flow, the multiple flow points can be calibrated, and the flow control is accurate. The cooling unit can reduce the heat generated by the circulating fan during operation, and keep the temperature stable.

[0022] The circulating fan is provided with a high-speed explosion-proof motor connected with the fan body through a magnetic coupler, without mechanical connection, no risk of leakage, no high harmonic pollution to the power grid, no electromagnetic interference problem, and high reliability; the magnetic coupling connection can realize soft start and soft stop of the fan body, in the starting process, the high-speed explosion-proof motor first drives the conductor rotor of the magnetic coupler to start, and then drives the permanent magnet rotor to start under full load, the staged starting process is stable, the impact is small, and the mechanical stress on the high-speed explosion-proof motor and the fan body is reduced; since there is no mechanical connection, there is no spark or hot surface, in addition, the design of the magnetic coupling connection can ensure that the power transmission can be quickly cut off in case of failure, further reducing the safety risk.

[0023] The cooling unit can continuously keep the temperature of the natural gas at the outlet of the heat exchanger stable in the set temperature range, the required refrigerating capacity of the heat exchanger outlet is judged through temperature monitoring of the upper, middle and lower positions of the hydraulic balance device, the refrigerating operation amount of the refrigerating unit is adjusted correspondingly, over-adjustment of the beam is avoided, and rapid and accurate stable adjustment control can be realized. When the temperature of the natural gas at the outlet of the heat exchanger is higher or lower than the preset temperature, the main control unit automatically adjusts the number of stages and the opening ratio of the adjusting valve or opens the compensation heater according to the built-in program, realizes automatic temperature reduction or temperature rise control, does not need manual intervention, and can quickly reach a temperature stable state. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a system principle schematic view of the utility model;

[0025] Figure 2 It is a flow control unit and temperature control unit principle schematic view of the utility model;

[0026] Figure 3 It is a cooling unit principle schematic view of the utility model;

[0027] Figure 4 It is a hydraulic balance device structure principle schematic view of the utility model;

[0028] In the figure: 1, loop unit; 2, temperature control unit; 3, flow control unit; 4, flow detection unit; 5, main control unit; 6, external natural gas pipeline; 7, pressure control unit; 8, auxiliary heater; 10, main loop pipeline; 11, loop inlet; 12, loop outlet; 20, heat exchanger; 21, cooling unit; 30, circulating fan; 31, backflow regulator; 40, working standard flow meter; 41, measured flow meter; 81, first temperature transmitter; 82, second temperature transmitter; 83, third temperature transmitter; 84, A1 water pipe joint; 85, A2 water pipe joint; 86, B1 water pipe joint; 87, B2 water pipe joint; 88, first water inlet pipe group; 89, second water inlet pipe group; 210, hydraulic balance device; 211, refrigeration unit; 212, backwater pipe group; 213, water outlet pipe group; 214, regulating valve; 215, first backflow pipe group; 216, second backflow pipe group; 217, compensation heater; 218, constant pressure water supply unit; 219, softened water module; 300, magnetic coupler; 301, high-speed explosion-proof motor; 302, fan body. DETAILED DESCRIPTION

[0029] The utility model will be further described below in combination with the drawings:

[0030] As Figure 1 , Figure 2 , Figure 3 and Figure 4 A loop circulating system based on natural gas calibration, the control system includes loop unit 1, temperature control unit 2, flow control unit 3, flow detection unit 4 and main control unit 5. Temperature control unit 2, flow control unit 3 and flow detection unit 4 are electrically connected with main control unit 5. In this embodiment, main control unit 5 selects industrial computer, passes through RS485 bus communication, has display, memory, and is equipped with modbus communication protocol, and the data interaction of host computer, can show each parameter value measured in the system on the display, and the program of the system operation is built-in in main control unit 5, and the program is set by the operation requirement of the person skilled in the art, and it is the public technical knowledge in the field, and it is not described in detail here. Figure 1 The dashed line connected with main control unit 5 in the figure represents signal line of electrical connection.

[0031] The natural gas is circulated in the loop unit 1. The loop unit 1 comprises a main loop pipeline 10 and a loop inlet 11 and a loop outlet 12 fixedly arranged on one side of the main loop pipeline 10, a first valve is arranged in the loop inlet 11, and a second valve is arranged in the loop outlet 12, both the first valve and the second valve are electrically controlled valves, the opening and closing of the first valve and the second valve can be controlled through the main control unit 5, and the loop inlet 11 and the loop outlet 12 are connected with the external natural gas pipeline 6. A pressure gauge for measuring the pressure of the natural gas in the main loop pipeline 10 is arranged on the main loop pipeline 10, and the pressure value measured by the pressure gauge is transmitted to the main control unit 5 in real time and displayed through the display.

[0032] A pressure control unit 7 is arranged between the loop inlet 11 and the external natural gas pipeline 6, and the pressure control unit 7 is used for injecting the natural gas in the external natural gas pipeline 6 into the main loop pipeline 10 through the loop inlet 11 according to a preset pressure. In the embodiment, the pressure control unit 7 is a compressor, and the natural gas injected into the main loop pipeline 10 is specified pressure through the compressor according to system requirements.

[0033] The temperature control unit 2 comprises a heat exchanger 20 arranged on the loop unit 1 and a cooling unit 21 connected with the heat exchanger 20, the cooling unit 21 is used for controlling the tube side temperature of the heat exchanger 20, and the natural gas in the loop unit 1 is subjected to temperature exchange after passing through the tube side of the heat exchanger 20, so that it is kept in a set temperature range and is stable.

[0034] The heat exchanger 20 is used for taking away the heat generated by the natural gas in the main loop pipeline 10 due to the pressurization work of the flow control unit 3, and the temperature change of the gas for calibration should not be more than ±0.5 ℃ during the calibration process, in the embodiment, a tube bundle heat exchanger is selected, which is composed of a group of parallel arranged pipes, the pipes are placed in an outer shell, and one or more channels are formed between the outer shell and the pipe bundle, which allow the second fluid to flow outside the pipe bundle, and the heat exchange between the two fluids can be realized through the heat exchange between the pipe bundle and the outer shell. In operation, the natural gas flows inside the pipe, and the cooling water flows outside the pipe, when the hot fluid passes through the pipe bundle, the heat is transferred to the cold fluid through the pipe wall. If the temperature of the hot fluid is higher than that of the cold fluid, the heat is transferred from the hot fluid to the cold fluid, and vice versa. The heat exchanger 20 has a large heat transfer area, improves the heat exchange efficiency, the pipe bundle can be disassembled, is convenient for cleaning and maintenance, and is suitable for various fluids and a wide range of temperature and pressure.

[0035] The cooling unit 21 comprises a hydraulic balance device 210, a refrigeration unit 211 arranged on the primary side of the hydraulic balance device 210, and a return water pipe group 212 and an outlet water pipe group 213 arranged on the secondary side of the hydraulic balance device 210, the return water pipe group 212 injecting the cooling water in the heat exchanger 20 into the hydraulic balance device 210, entering the refrigeration unit 211 through the primary side of the hydraulic balance device 210 to be cooled, and then flowing into the outlet water pipe group 213 through the secondary side of the hydraulic balance device 210, and the outlet water pipe group 213 injecting the cooled water into the heat exchanger 20 again to be cooled. The hydraulic balance device 210 is used to balance the hydraulic disturbance caused by the simultaneous operation of the constant flow and variable flow systems, effectively prevents the refrigeration unit 211 from stopping due to the reduction of flow, removes the 10 um micro-bubbles and 5 um particle impurities, and has the function of the energy storage buffer tank.

[0036] The flow control unit 3 comprises a circulating fan 30 and a backflow regulator 31 arranged on the loop unit 1, and the circulating fan 30 and the backflow regulator 31 circulate the natural gas in the loop unit 1 according to the preset flow range; the circulating fan 30 comprises a high-speed explosion-proof motor 301 and a fan body 302 connected through a magnetic coupler 300, and the fan body 302 is connected in series on the loop unit 1 to provide power for the flow of the natural gas. The backflow regulator 31 adopts a bypass electric flow valve, which can accurately control the opening and closing and flow control. The flow control is realized by the circulating fan 30 matched with a frequency converter for large flow adjustment. In order to ensure the stable operation of the low flow, the backflow regulator 31 is controlled according to 20% of the maximum flow of a single circulating fan 30, so as to accurately adjust the flow of the medium in the loop unit in the full range.

[0037] The magnetic coupling connection can transmit power without any mechanical contact, can replace the traditional mechanical connection, has strong reliability and safety, can realize soft start, the starting process is stable, the impact is small, and the mechanical stress on the motor and the fan is reduced. The high-speed explosion-proof motor 301 is designed to be compact and firm, greatly reducing the size and weight of the fan; has high efficiency, directly drives the load, and reduces energy loss. Since the high-speed explosion-proof motor 301 is external, cooling does not require an external water cooling system, reducing the risk of water leakage of the loop system, the temperature rise of the fan inlet and outlet is small, greatly reducing the power consumption of the matched heat exchange system and refrigeration system; the replacement parts are convenient, the maintenance and repair of the motor are more convenient; the flow adjustment range is wider, the flow adjustment ratio can reach 1:20, and the small flow adjustment is more accurate.

[0038] In the embodiment, two circulating fans 30 and two heat exchangers 20 are arranged, one circulating fan 30 and one heat exchanger 20 are connected in series as a group, and two groups are arranged in parallel.

[0039] The flow detection unit 4 comprises a working standard flow meter 40 arranged on the loop unit 1 and a detected flow meter 41, and the working standard flow meter 41 is used for calibrating the detected flow meter 40, and when the pressure, flow and temperature in the main loop pipeline 10 reach the set requirements, the corresponding flow point of the detected flow meter 40 is calibrated.

[0040] A plurality of regulating valves 214 are arranged in parallel on the outlet water pipe group 213, and a first backflow pipe group 215 and a second backflow pipe group 216 are arranged between the outlet water pipe group 213 and the return water pipe group 212, and the first backflow pipe group 215 and the second backflow pipe group 216 are arranged on both sides of the plurality of regulating valves 214 arranged in parallel; a compensation heater 217 is arranged on the outlet water pipe group 213, and the compensation heater 217 is used for heating the water in the outlet water pipe group 213.

[0041] The first temperature transmitter 81, the second temperature transmitter 82 and the third temperature transmitter 83 are arranged at the upper, middle and lower positions in the hydraulic balance device 210 respectively; the A1 water pipe joint 84 and the A2 water pipe joint 85 are fixedly arranged on the primary side of the hydraulic balance device 210, and the water inlet end of the refrigerating unit 211 is connected in communication with the A1 water pipe joint, and the auxiliary heater 8 is further arranged on the first water inlet pipe group 88, and when the top temperature of the hydraulic balance device 210 is lower than 6℃ (the shutdown temperature of the refrigerating unit 211), the auxiliary heater 8 is started to maintain the minimum load operation of the unit, so as to ensure that the refrigerating unit 211 does not shut down, and the auxiliary heater 8 is an electric heater, and the opening and closing of the auxiliary heater 8 is controlled by the main control unit 5. The temperature transmitter for detecting temperature, the pressure transmitter for detecting pressure, the circulating pump for providing circulating power for water and the electric control flow valve are arranged on the first water inlet pipe group 88. The temperature transmitter, the pressure transmitter, the circulating pump and the electric control flow valve are electrically connected with the main control unit 5.

[0042] The water outlet end of the refrigerating unit 211 is connected in communication with the A2 water pipe joint 85 through the second water inlet pipe group 89. The temperature transmitter for detecting temperature and the electric control flow valve for controlling opening and closing are arranged on the second water inlet pipe group 89. The temperature transmitter and the electric control flow valve are electrically connected with the main control unit 5.

[0043] The B1 water pipe joint 86 and the B2 water pipe joint 87 are arranged on the secondary side of the hydraulic balance device 210, one end of the return water pipe group 212 is connected to the B1 water pipe joint 86, and one end of the outlet water pipe group 213 is connected to the B2 water pipe joint 87. The pressure transmitter, the thermometer, the temperature transmitter and the electric control flow valve are arranged on the return water pipe group 212. The electric control flow valve, the circulating pump, the pressure transmitter, the flow meter and the temperature transmitter are arranged on the outlet water pipe group 213, and the electric control flow valve, the circulating pump, the pressure transmitter, the flow meter and the temperature transmitter are electrically connected with the main control unit 5.

[0044] In a preferred embodiment, a constant pressure water supply unit 218 is arranged on the return water pipe group 212, and is used to ensure the water pressure in the cooling unit 21; the constant pressure water supply unit 21 is connected to a tap water pipe through a softened water module 219, the softened water module 219 softens the water in the tap water pipe, and then supplies the softened water to the constant pressure water supply unit 21; the softened water module 219 selects a full-automatic softened water device on the market, and the constant pressure water supply unit 218 selects a constant pressure water supply device on the market. When the water pressure in the cooling unit 21 is lower than 1.4 bar, the constant pressure water supply unit 218 is started to automatically supply water, and the water supply is automatically stopped when the water pressure reaches 1.5 bar.

[0045] When the flow rate of the primary side of the water balance device 210 is equal to the flow rate of the secondary side of the water balance device 210, the temperature at the A1 water pipe joint 84 is the same as the temperature at the B1 water pipe joint 86, and the temperature at the A2 water pipe joint 85 is the same as the temperature at the B2 water pipe joint 87; at this time, the medium in the water balance device 210 is relatively static, and the temperature stratification tends to be stable; this state is the ideal state.

[0046] When the flow rate of the primary side of the water balance device 210 is less than the flow rate of the secondary side of the water balance device 210, the temperature at the A1 water pipe joint 84 is the same as the temperature at the B1 water pipe joint 86, and the temperature at the A2 water pipe joint 85 is greater than the temperature at the B2 water pipe joint 87; at this time, part of the return water at the B2 water pipe joint 87 participates in the water supply at the B1 water pipe joint 86, and the temperature in the water balance device 210 gradually increases from top to bottom; this state is the case where the refrigeration capacity cannot meet the demand of the cooling operation energy.

[0047] When the flow rate of the primary side of the water balance device 210 is greater than the flow rate of the secondary side of the water balance device 210, the temperature at the A2 water pipe joint 85 is the same as the temperature at the B2 water pipe joint 87, and the temperature at the A1 water pipe joint 84 is greater than the temperature at the B1 water pipe joint 86; at this time, part of the return water at the A2 water pipe joint 85 participates in the return water at the A1 water pipe joint 84, and the temperature in the water balance device 210 gradually decreases from top to bottom. This state is the case where the refrigeration capacity exceeds the demand of the cooling operation energy.

[0048] The refrigeration operation of the cooling unit 21 includes a precooling phase and a temperature regulation phase;

[0049] The precooling phase includes:

[0050] M1, after obtaining the refrigeration command of the master control unit 5, a set of refrigeration unit 211 of the primary side of the hydraulic balance device 210 is started, and the circulating pump in the first water inlet pipe group 88 injects water into the refrigeration unit 211, so that the water circulates between the hydraulic balance device 210, the first water inlet pipe group 88, the refrigeration unit 211 and the second water inlet pipe group 89, and the water temperature is reduced;

[0051] M2, the temperature of the hydraulic balance device 210 is monitored in real time by the first temperature transmitter 81, the second temperature transmitter 82 and the third temperature transmitter 83, when the temperature at the top of the hydraulic balance device 210 reaches the preset value 7℃, the pre-cooling stage is completed, and the pre-cooling stage completion signal is fed back to the master control unit 5.

[0052] When the first set of circulating fans 30 is running, the master control unit 5 interlocks to start the circulating pump of the secondary side of the hydraulic balance device 210 in the corresponding cooling unit 21 (i.e. the circulating pump in the water outlet pipe group 213); when the second set of circulating fans 30 is running, the master control unit 5 interlocks to start the circulating pump of the secondary side of the hydraulic balance device 210 in the corresponding cooling unit 21; when the two sets of circulating fans 30 are running at the same time, the master control unit 5 interlocks to start the circulating pump of the secondary side of the hydraulic balance device 210 in the cooling unit 21, one of which is frequency conversion operation, and the other is fixed frequency operation.

[0053] The temperature regulation stage includes: real-time monitoring of the temperature of natural gas at the outlet of the heat exchanger 20, adjusting the number and opening ratio of the regulating valves 214 in the return water pipe group 212 by comparing the detected temperature with the set temperature, and regulating the temperature.

[0054] When the temperature of natural gas at the outlet of the heat exchanger 20 exceeds the preset temperature (20℃+0.5℃), gradually open the number and opening ratio of the regulating valves 214 in the return water pipe group 212, increase the flow of cooling water into the heat exchanger 20, and cool down; in this embodiment, the regulating valves 214 are arranged in parallel in three, which are DN50, DN100 and DN150.

[0055] When the temperature of natural gas at the outlet of the heat exchanger 20 reaches the preset temperature, the regulating valve 214 maintains the current opening; in this embodiment, the preset temperature is 20℃.

[0056] When the temperature of natural gas at the outlet of the heat exchanger 20 is lower than the preset temperature (20℃-0.5℃), the number and opening ratio of the regulating valves 214 in the return water pipe group 212 are adjusted in the opposite direction, and the flow of cooling water into the heat exchanger 20 is reduced, so that the temperature of natural gas at the outlet of the heat exchanger 20 tends to the preset temperature (20℃) and stabilizes.

[0057] When the natural gas at the outlet of the heat exchanger 20 does not need to be cooled, the parallel regulating valves 214 are all in the closed state, at this time, the water in the water return pipe group 212 is returned to the middle water outlet pipe group 213 through the first water return pipe group 88, the fluid circulation is realized, and the pressure blocking phenomenon is prevented.

[0058] When the parallel regulating valves 214 are all in the closed state and the temperature of the natural gas at the outlet of the heat exchanger 20 is still lower than the set temperature, at this time, the compensation heater 217 is started to increase the temperature of the water in the water return pipe group 212, and when the temperature of the natural gas at the outlet of the heat exchanger 20 reaches the set temperature, the compensation heater 217 is automatically stopped.

[0059] When the top temperature of the hydraulic balance device 210 is higher than 12℃, the refrigerating capacity of the refrigerating unit 211 is increased, and the rapid cooling is realized by increasing the working frequency of the circulating pump in the first water inlet pipe group 88 and increasing the refrigerating capacity of the refrigerating unit 211. When the middle temperature of the hydraulic balance device 210 is higher than 12℃, the second set of refrigerating units 211 is started; when the bottom temperature of the hydraulic balance device 210 is higher than 12℃, the main control unit 5 sends an over-temperature alarm to remind the operator to check the system condition; when the middle temperature of the hydraulic balance device 210 returns to 7℃, the second set of refrigerating units 211 is closed.

[0060] When the circulating fan 30 controls the total flow of the working standard flow meter 40 to be within 5% of the calibration flow point, it is determined that the current flow point is stable and effective. When the system determines that the total flow fluctuation range of the working standard flow meter 40 is not more than 5% of the preset value, the temperature fluctuation range of the working standard flow meter 40 is not more than 0.5℃, and the pressure fluctuation range of the working standard flow meter 40 is not more than 0.5% within a certain time, the three adjustments are satisfied at the same time, at this time, the calibration of the flow point is automatically started.

[0061] The above embodiments are only a number of descriptions of the concept and implementation of the present application, and do not limit the present application. Under the concept of the present application, the technical solutions without substantial changes are still within the protection scope.

Claims

1. A loop circulating system for natural gas rating, characterized by: The loop circulating system comprises a loop unit, a temperature control unit, a flow control unit, a flow detection unit and a master control unit; natural gas circulates in the loop unit; The temperature control unit comprises a heat exchanger arranged on the loop unit and a cooling unit connected with the heat exchanger, the cooling unit is used for controlling the tube side temperature of the heat exchanger, and the natural gas of the loop unit keeps temperature stable after passing through the tube side of the heat exchanger; The cooling unit comprises a hydraulic balance device, a refrigeration unit arranged on the primary side of the hydraulic balance device and a return water pipe group and an outlet water pipe group arranged on the secondary side of the hydraulic balance device, the return water pipe group injects cooling water in the heat exchanger into the hydraulic balance device, the cooling water enters the refrigeration unit through the primary side of the hydraulic balance device to be cooled, and then flows into the outlet water pipe group through the hydraulic balance device, and the outlet water pipe group injects the cooled water into the heat exchanger again to be cooled; The flow detection unit comprises a working standard flowmeter arranged on the loop unit and a detected flowmeter, and the working standard flowmeter is used for calibrating the detected flowmeter; The flow control unit comprises a circulating fan and a backflow regulator arranged on the loop unit, the circulating fan and the backflow regulator circulate the natural gas in the loop unit according to a preset flow range; the circulating fan comprises a high-speed explosion-proof motor and a fan body connected through a magnetic coupler, and the fan body is connected in series on the loop unit; The temperature control unit, the flow control unit and the flow detection unit are electrically connected with the master control unit.

2. A loop circulating system for natural gas certification based on claim 1, characterized by: The loop unit comprises a main loop pipeline and a loop inlet and a loop outlet arranged on one side of the main loop pipeline, a first valve is arranged in the loop inlet, and a second valve is arranged in the loop outlet; the loop inlet and the loop outlet are connected with the external natural gas pipeline and the main loop pipeline.

3. A loop circulating system for natural gas certification based on claim 2, characterized by: A pressure control unit is arranged between the loop inlet and the external natural gas pipeline, and the pressure control unit is used for injecting the natural gas in the external natural gas pipeline into the main loop pipeline through the loop inlet according to a preset pressure.

4. The loop circulating system for natural gas rating based on claim 1 or 3, characterized by: Two circulating fans and two heat exchangers are arranged, one circulating fan and one heat exchanger are connected in series as a group, and two groups are connected in parallel.

5. The loop circulating system for natural gas rating based on claim 1, characterized by: First, second and third temperature transmitters are arranged at upper, middle and lower positions in the hydraulic balance device; A1 and A2 water pipe joints are arranged on the primary side of the hydraulic balance device, a first water inlet pipe group is connected with the A1 water pipe joint in communication, and a second water inlet pipe group is connected with the A2 water pipe joint in communication; B1 and B2 water pipe joints are arranged on the secondary side of the hydraulic balance device, the return water pipe group is connected with the B1 water pipe joint, and the outlet water pipe group is connected with the B2 water pipe joint.

6. The loop circulating system for natural gas rating based on claim 4, characterized by: A constant pressure water supplementing unit is arranged on the return water pipe group, and the constant pressure water supplementing unit is used for ensuring the water pressure in the cooling unit; the constant pressure water supplementing unit is connected with a tap water pipe through a softened water module.

7. The loop circulating system for natural gas rating based on claim 5, characterized by: When the flow rate of the primary side of the hydraulic balance device is equal to the flow rate of the secondary side of the hydraulic balance device, the temperature at the A1 water pipe joint is the same as the temperature at the B1 water pipe joint, and the temperature at the A2 water pipe joint is the same as the temperature at the B2 water pipe joint, at which time the medium in the hydraulic balance device is relatively stationary, and the temperature stratification tends to be stable; When the flow rate of the primary side of the hydraulic balance device is less than the flow rate of the secondary side of the hydraulic balance device, the temperature at the A1 water pipe joint is the same as the temperature at the B1 water pipe joint, and the temperature at the A2 water pipe joint is greater than the temperature at the B2 water pipe joint, at which time a portion of the return water at the B2 water pipe joint participates in the supply of water at the B1 water pipe joint, and the temperature in the hydraulic balance device gradually increases from top to bottom; When the flow rate of the primary side of the hydraulic balance device is greater than the flow rate of the secondary side of the hydraulic balance device, the temperature at the A2 water pipe joint is the same as the temperature at the B2 water pipe joint, and the temperature at the A1 water pipe joint is greater than the temperature at the B1 water pipe joint, at which time a portion of the return water at the A2 water pipe joint participates in the return of water at the A1 water pipe joint, and the temperature in the hydraulic balance device gradually decreases from top to bottom.

8. The loop circulating system for natural gas rating based on claim 6, characterized by: When the water pressure in the cooling unit is less than 1.4 bar, the constant-pressure water supplementing unit is started to automatically supplement water, and the supplementing of water is automatically stopped when the water pressure reaches 1.5 bar.

9. The loop circulating system for natural gas rating based on claim 1, characterized by: A plurality of adjusting valves are arranged in parallel on the water outlet pipe group, and a first return pipe group and a second return pipe group are arranged between the water outlet pipe group and the return water pipe group, and the first return pipe group and the second return pipe group are arranged on both sides of the plurality of adjusting valves.

10. The loop circulating system for natural gas rating based on claim 1, characterized by: A compensation heater is arranged on the water outlet pipe group, and the compensation heater is used to warm the water in the water outlet pipe group.

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