Constant-temperature dew-point instrument measuring system and temperature control method thereof

Abstract

The invention belongs to the technical field of dew-point instrument constant temperature control. The invention provides a constant-temperature dew-point instrument system. The constant-temperature dew-point instrument system comprises an electromagnetic valve, an EPC, a vortex tube, an MCU and a constant-temperature cavity, an inlet, a condensation type dew-point instrument and a temperature sensor are arranged in the constant-temperature cavity; the vortex tube is provided with a cold air outlet and a hot air outlet; a cold air outlet of the vortex tube is communicated with an inlet of the constant-temperature cavity through a gas pipeline; the temperature sensor, the electromagnetic valve and the EPC are all connected with the MCU signal circuit; and the electromagnetic valve, the EPC and the vortex tube are sequentially communicated through a gas pipeline. According to the scheme, a constant-temperature environment can be provided for the condensation type dew-point instrument, and the measurement precision of the condensation type dew-point instrument is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of constant temperature control of dew point instruments. Background Art

[0002] Existing chilled mirror dew point meters are usually used in laboratory conditions to measure the dew point of gases. They are currently the humidity measurement method and device with the highest traceability and accuracy. This method has not yet been applied to the monitoring of flue gas humidity at pollution sources. However, the environmental conditions at pollution sources are changeable, and the temperature varies greatly with the seasons and regions. In addition, the working conditions of the equipment are usually near the flue gas, so the temperature range is -20 degrees to 50 degrees. Under these conditions, the working conditions of the dew point meter probe are greatly affected. The working environment temperature of the chilled mirror dew point meter probe is too high, which affects the heat dissipation effect of the probe, thereby affecting the dew point temperature measurement control accuracy. Summary of the invention

[0003] In view of this, the present invention provides a constant temperature dew point meter system, comprising: a solenoid valve, an EPC, a vortex tube, an MCU, and a constant temperature cavity; the constant temperature cavity is provided with an inlet, a condensing dew point meter and a temperature sensor; the vortex tube is provided with a cold air outlet and a hot air outlet; the cold air outlet of the vortex tube is connected to the inlet of the constant temperature cavity through a gas pipeline; the temperature sensor, the solenoid valve and the EPC are all connected to the MCU signal circuit; the solenoid valve, the EPC and the vortex tube are connected in sequence through the gas pipeline.

[0004] Furthermore, the temperature sensor is a PT100 thermistor.

[0005] The present invention also provides a temperature control method for a constant temperature dew point instrument system, comprising the following steps: the MCU controls the on and off of the solenoid valve to realize ventilation and air cut-off control of the instrument air; the MCU controls the EPC to adjust the gas pressure at the EPC outlet, and the pressure change can adjust the amount of cold air in the vortex tube, thereby adjusting the ambient temperature in the constant temperature cavity; the MCU measures the temperature in the cavity through a temperature sensor.

[0006] The solution of the present invention can provide a constant temperature environment for the condensation dew point meter, thereby ensuring the measurement accuracy of the condensation dew point meter. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is the system diagram of the constant temperature dew point instrument. DETAILED DESCRIPTION

[0008] Example

[0009] Chilled mirror dew point meter: It uses optical method to measure the condensation of mirror surface. The mirror temperature is precisely controlled by semiconductor cold plate. The mirror temperature reflects the dew point temperature of gas. The basic principle of chilled mirror dew point meter: When a certain volume of gas is cooled evenly under constant pressure, the partial pressure of gas and water in the gas remains unchanged until the water in the gas reaches saturation. The temperature in this state is the dew point of the gas. Usually, the mirror and its accessories are installed in the measuring room through which the gas flows. The dew point of the gas is determined by measuring the mirror temperature when the number of water molecules leaving and returning to the mirror in unit time reaches dynamic equilibrium. A certain gas humidity corresponds to a dew point temperature; a dew point temperature corresponds to a certain gas humidity. Therefore, the humidity of the gas can be determined by measuring the dew point temperature of the gas.

[0010] Vortex tube: A device that uses the principles of physics to separate the flow of cold and hot gases.

[0011] The present invention provides a constant temperature dew point instrument system, comprising: a solenoid valve 1, an EPC 2, a vortex tube 3, an MCU 4, and a constant temperature cavity 5.

[0012] The solenoid valve, EPC and vortex tube are connected in sequence through a gas pipeline;

[0013] The constant temperature cavity is provided with a condensing dew point meter 6 and a temperature sensor 7; the temperature sensor is a PT100 thermistor.

[0014] The vortex tube is provided with a cold air outlet and a hot air outlet;

[0015] The cold air outlet of the vortex tube is connected to the inlet of the constant temperature cavity through a gas pipeline;

[0016] The instrument air passes through the solenoid valve and EPC (electronic pressure regulator) to the vortex tube, where it is divided into cold air and hot air; the cold air enters the constant temperature cavity, and the hot air is discharged into the ambient air.

[0017] The temperature sensor, solenoid valve and EPC are all connected to the control unit MCU through signal lines.

[0018] The control unit MCU controls the on and off of the solenoid valve to control the ventilation and air cut-off of the instrument. The MCU controls the EPC to adjust the gas pressure at the EPC outlet. The pressure change can adjust the amount of cooling air in the vortex tube, and then adjust the ambient temperature in the constant temperature cavity. The control unit MCU measures the temperature inside the cavity through the temperature sensor.

[0019] When the condensing dew point meter is working normally, its dew point temperature is usually below zero degrees, and the mirror of the dew point meter is usually in a cooling state. The cooling is achieved through Peltier semiconductors, and the outside of the probe housing is in a heat dissipation state, which causes the ambient temperature to rise. If the ambient temperature is not cooled, when the ambient temperature reaches a certain level, the Peltier cooling plate refrigeration reaches full power working state, the outside cannot dissipate heat, and the inside is no longer cooled. The system will give an alarm error, affecting its normal operation.

[0020] The constant temperature control method of the present invention comprises the following steps:

[0021] The control unit MCU measures the temperature in the cavity through the temperature sensor. If it is higher than 7.5 degrees;

[0022] The control unit MCU increases the gas pressure at the EPC outlet so that the temperature in the cavity is between 5.5-7.5 degrees;

[0023] The control unit MCU can adaptively adjust the temperature and power according to the cavity temperature and the cooling power of the cold plate of the dew point meter: the control unit MCU determines whether the cooling power of the cold plate of the dew point meter is greater than 90%; if greater than 90%;

[0024] The control unit MCU increases the gas pressure at the EPC outlet so that the temperature in the chamber is between 3.5-5.5 degrees;

[0025] The control unit MCU determines whether the cooling power of the cold plate of the dew point meter is greater than 90%; if greater than 90%;

[0026] The control unit MCU increases the gas pressure at the EPC outlet so that the temperature in the cavity is between 1.5-3.5 degrees;

[0027] Until the cooling capacity of the dew point meter is less than 90%.

[0028] The instrument air is output through the solenoid valve and EPC pressure regulating vortex tube cooling air volume, adjusting the gas temperature in the constant temperature chamber, the temperature sensor senses the temperature, the MCU controls the temperature, the PID controls, and dynamically adjusts the EPC pressure; Under normal circumstances, the dew point meter has a measurement range of (-40 to 0) degrees, and its optimal working temperature is (5 to 10) degrees. If it exceeds this range, the MCU alarm output; The MCU controls the temperature to set at 7.5 degrees, and the PID dynamically adjusts the EPC output pressure to ensure that the temperature in the constant temperature box is stable at around 7.5 degrees; The instrument air supply pressure range is 0.4 to 0.6 MPa, and the flow rate is greater than 100L / min; In special cases, the cooling power range of the dew point meter Peltier semiconductor refrigeration module is 0-99%. Under the same dew point, the higher the ambient temperature, the worse the heat dissipation effect, and the higher the cooling power. The MCU dynamically associates the cooling power with the temperature control setting temperature, with 7.5 degrees as the initial temperature, and automatically adjusts the temperature value according to the cooling power of the cooling plate, so that the cooling plate power does not exceed 90%; that is, when the cooling plate power exceeds 90%, the MCU automatically and span-type lowers the set temperature of the thermostat, and the span value is 2 degrees, which can be adjusted multiple times at regular intervals to ensure that the cooling plate power is less than 90%.

Claims

1. Constant temperature dew point instrument system, characterized by: include: Solenoid valve, EPC, vortex tube, MCU, constant temperature chamber; The constant temperature cavity is provided with an inlet, a condensation dew point meter and a temperature sensor; The vortex tube is provided with a cold air outlet and a hot air outlet; The cold air outlet of the vortex tube is connected to the inlet of the constant temperature cavity through a gas pipeline; The temperature sensor, solenoid valve and EPC are all connected to the MCU signal circuit; The solenoid valve, EPC and vortex tube are sequentially connected through a gas pipeline.

2. The constant temperature dew point instrument system according to claim 1, characterized in that: The temperature sensor is a PT100 thermistor.

3. The temperature control method of the constant temperature dew point instrument system according to any one of claims 1 to 2, characterized in that: The steps include: The control unit MCU measures the temperature in the cavity through the temperature sensor. If it is higher than 7.5 degrees; The control unit MCU increases the EPC outlet gas pressure so that the temperature inside the cavity is between 5.5-7.5 degrees.

4. The temperature control method of the constant temperature dew point instrument system according to claim 3 is characterized in that: The control unit MCU can adaptively adjust the temperature and power according to the cavity temperature and the cooling power of the cold plate of the dew point meter: The control unit MCU determines whether the cooling power of the cold plate of the dew point meter is greater than 90%; if greater than 90%; The control unit MCU increases the gas pressure at the EPC outlet so that the temperature in the chamber is between 3.5-5.5 degrees; The control unit MCU determines whether the cooling power of the cold plate of the dew point meter is greater than 90%; if greater than 90%; The control unit MCU increases the gas pressure at the EPC outlet so that the temperature in the cavity is between 1.5-3.5 degrees; Until the cooling capacity of the dew point meter is less than 90%.

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