Fresh air handling unit air volume measuring method based on heat recovery core body pressure difference

Abstract

The invention discloses a fresh air handling unit air volume measuring method based on heat recovery core body pressure difference. The fresh air handling unit air volume measuring method specifically comprises the following steps that firstly, the pressure difference is measured; step 2, resistance calibration; step 3, wind speed calculation; 4, dynamically correcting the resistance coefficient of the core body; 5, air volume output control and alarm are carried out; the invention relates to the technical field of heating ventilation air conditioners. According to the fresh air handling unit air volume measuring method based on the heat recovery core body pressure difference, the heat recovery core body serves as a natural throttling device, the air volume is measured through the inherent resistance characteristic of the heat recovery core body, the production cost is reduced, and the real-time air volume is calculated by measuring the front-back pressure difference of the heat recovery core body and combining temperature and pressure compensation and the pre-calibrated core body resistance coefficient; the method has the advantage of being high in air volume calculation precision, the problem of data drift is effectively solved by dynamically adjusting the resistance coefficient of the core body, accurate fault alarm of the air conditioner can be achieved by combining monitoring of operation data and comparative analysis of historical data, and the fault shutdown risk is effectively eliminated.

Description

Technical Field

[0001] The present invention relates to the technical field of heating, ventilation and air conditioning, and in particular to a method for measuring the air volume of a fresh air unit based on the pressure difference of a heat recovery core. Background Art

[0002] Existing civil heat recovery fresh air units generally do not have measures to stabilize the air volume in real time during operation. The calibrated air volume of the unit is only the air volume measured on the test bench for a specific working condition. In actual use, the actual operating air volume is different due to the different resistance of the external piping system. Changes in resistance with components such as the filter during operation will also cause changes in air volume, which in turn causes the indoor air volume balance to be destroyed, resulting in energy waste and environmental deterioration. In particular, in the radiant cooling system, it is easy to cause excessive local humidity and lead to condensation on the radiant surface.

[0003] Existing heat recovery fresh air units typically require additional orifice plates, venturi tubes, or wind speed sensors to measure supply and exhaust airflow. This increases installation space, equipment costs, system pressure drop, and maintenance complexity. Therefore, a low-cost, easy-to-install and maintain method for measuring airflow within the unit is urgently needed. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for measuring the air volume of a fresh air unit based on the pressure difference of a heat recovery core, which solves the problems raised in the above-mentioned background technology.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: a method for measuring the air volume of a fresh air unit based on the pressure difference of a heat recovery core, specifically comprising the following steps:

[0006] Step 1: Pressure difference measurement: Place pressure difference sensors and temperature sensors at the air inlet and outlet of the clean heat recovery core of the heat recovery fresh air unit to collect pressure difference and temperature data;

[0007] Step 2: Resistance calibration: Use standard air volume measurement equipment to obtain the pressure difference of the clean heat recovery core under different air volumes. Perform fitting processing on the pressure difference under different air volumes to obtain the core resistance coefficient and air volume curve, completing the core resistance coefficient calibration and pressure difference calibration;

[0008] Step 3: Calculate wind speed: Obtain temperature and pressure compensation based on temperature data and calculate wind volume;

[0009] Step 4: Dynamic correction of core resistance coefficient: Adjust the fan speed according to the preset logic until the current pressure difference is equal to the pressure difference calibrated in step 2, calculate the real-time air volume corresponding to the current pressure difference, obtain the calibrated air volume corresponding to the current pressure difference based on the core resistance coefficient and air volume curve, and dynamically adjust the core resistance coefficient based on the ratio of the real-time air volume to the calibrated air volume;

[0010] Step 5. Air volume output control and alarm: Use the PID control module to control the fan speed to meet the target air supply and exhaust volume based on the dynamically adjusted core resistance coefficient, and establish an alarm mechanism based on the fan speed and pressure difference. When the alarm mechanism requirements are met, the corresponding alarm will be issued.

[0011] The present invention is further configured as follows: the method of collecting the pressure difference includes:

[0012] Several pressure difference sensors are respectively set up upstream and downstream of the fresh air channel and the exhaust channel of the heat recovery core, and the average value of the several pressure difference sensors is used as the calculated pressure difference.

[0013] The present invention is further configured as follows: the core resistance and air volume curve includes:

[0014] K=f(Q)

[0015] Where K is the core resistance coefficient and Q is the air volume.

[0016] The present invention is further configured as follows: the method of obtaining temperature and pressure compensation according to temperature data includes:

[0017]

[0018] Where ρ is the gas density, P is the absolute pressure of the gas, R is the gas constant, which is 287 j / (kg·T), and T is the absolute temperature of the gas.

[0019] The present invention is further configured as follows: the formula for calculating the air volume in step 3 is:

[0020]

[0021] Where Q is the air volume, K is the core resistance coefficient, ΔP is the pressure difference, T is the absolute temperature of the gas, and P is the absolute pressure of the gas.

[0022] The present invention is further configured as follows: the preset logic in step 4 includes: timing triggering dynamic adjustment of the core resistance coefficient, active triggering dynamic adjustment of the core resistance coefficient, and abnormal triggering dynamic adjustment of the core resistance coefficient, wherein the abnormal triggering dynamic adjustment of the core resistance coefficient includes:

[0023] The deviation between the current differential pressure and the calibrated differential pressure is greater than ±15%.

[0024] The present invention is further configured as follows: in step 4, the method of dynamically adjusting the core resistance coefficient according to the ratio of the real-time air volume to the calibrated air volume includes:

[0025]

[0026] Where Kactual is the updated core resistance coefficient, Q_initial is the calibrated air volume, Q_current is the real-time air volume, K lab is the target core drag coefficient.

[0027] The present invention is further configured such that the alarm mechanism in step 5 includes:

[0028] Core blockage warning mechanism: Real-time monitoring of the pressure difference deviation from historical data at a specific fan speed. If the pressure difference increase exceeds the preset threshold, a cleaning alarm is triggered;

[0029] Core air leakage warning mechanism: Real-time monitoring of the pressure difference deviation from historical data at a specific fan speed. If the pressure difference drops beyond a preset threshold, an air leakage alarm is triggered.

[0030] Pipeline system blockage warning: Real-time monitoring of the deviation between the air volume and historical data at a specific fan speed. If the air volume drop exceeds the preset threshold, a pipeline blockage alarm is triggered;

[0031] Pipeline system air leakage warning: Real-time monitoring of the deviation between the air volume and historical data at a specific fan speed. If the air volume increase exceeds the preset threshold, the pipeline air leakage alarm is triggered.

[0032] The present invention provides a method for measuring the air volume of a fresh air unit based on the pressure difference of a heat recovery core. It has the following beneficial effects:

[0033] The present invention uses the heat recovery core as a natural throttling device and utilizes its inherent resistance characteristics to measure the air volume, eliminating additional sensors and reducing production costs. At the same time, by measuring the pressure difference before and after the heat recovery core, the real-time air volume is calculated in combination with temperature and pressure compensation and the pre-calibrated core resistance coefficient. It has the advantage of high air volume calculation accuracy and effectively solves the problem of data drift by dynamically adjusting the core resistance coefficient. Combined with the monitoring of operating data and the comparative analysis of historical data, it can also realize accurate fault alarm of the air conditioner, effectively eliminating the risk of fault shutdown. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic diagram of the test bench data calibration process in an embodiment of the present invention;

[0035] Figure 2 Schematic diagram of the dynamic correction process of the core resistance coefficient in an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the data initialization process in an embodiment of the present invention;

[0037] Figure 4 Schematic diagram comparing the calculated air volume and the measured air volume in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0039] See also Figure 1-4 The embodiment of the present invention provides the following technical solution: a method for measuring the air volume of a fresh air unit based on the pressure difference of a heat recovery core, specifically comprising the following steps:

[0040] Step 1: Pressure difference measurement: Install pressure difference sensors and temperature sensors at the air inlet and outlet of the clean heat recovery core of the heat recovery fresh air unit to collect pressure difference and temperature data. The sensor measurement range should be selected according to the characteristics of the heat recovery core. Comfort air conditioning uses 0-500Pa. The measurement accuracy should be less than or equal to ±1% FS. In order to reduce the impact of uneven airflow distribution, the pressure difference can be collected in the following ways:

[0041] Several pressure difference sensors are respectively set up upstream and downstream of the fresh air channel and the exhaust channel of the heat recovery core, and the average value of the several pressure difference sensors is used as the calculated pressure difference.

[0042] Step 2: Resistance calibration: Use standard air volume measurement equipment on the test bench to obtain the pressure difference of the clean heat recovery core under different air volumes. The specific process is as follows: Figure 1 As shown, the pressure difference under different air volumes is fitted to obtain the core resistance coefficient and air volume curve, namely the KQ curve, to complete the core resistance coefficient calibration and pressure difference calibration, and store the KQ curve in the control unit of the heat recovery fresh air unit. The actual operation control can select the target core resistance coefficient K according to the set air volume. lab The core resistance and air volume curves include:

[0043] K=f(Q)

[0044] Where K is the core resistance coefficient and Q is the air volume.

[0045] Step 3: Wind speed calculation: Obtain temperature and pressure compensation based on temperature data. The methods include:

[0046]

[0047] Where ρ is the gas density, P is the absolute pressure of the gas, R is the gas constant, which is 287 j / (kg·T), and T is the absolute temperature of the gas.

[0048] Since the heat recovery core acts as an airflow resistance component, its pressure difference is proportional to the square of the air volume. The formula for calculating the air volume is:

[0049]

[0050] Where Q is the air volume, K is the core resistance coefficient, ΔP is the pressure difference, T is the absolute temperature of the gas, and P is the absolute pressure of the gas.

[0051] Further instructions, initialization after initial installation, as shown in the attached Figure 3 As shown, after the piping system is installed, the initialization operation is manually triggered, and the stabilized air volume, pressure difference, and fan speed are recorded according to the calibrated air volume points, and a lookup table is established and stored in the control unit.

[0052] In this step, since the internal pressure change of the heat recovery fresh air unit accounts for less than 1% of the atmospheric pressure, the effect on the result is very small. In practical applications, only the local atmospheric pressure correction is considered, which can be selected from the local meteorological parameters according to the season. No additional atmospheric pressure sensor is required. For high humidity environments, the impact of water vapor on air density needs to be considered. This method should mainly be used for comfort air-conditioning equipment, and the control accuracy requirements are not high. Therefore, humidity correction is ignored, and combined with temperature and pressure compensation, it can solve the measurement accuracy problem in high altitude and high and low temperature application sites.

[0053] Step 4: Dynamic correction of core drag coefficient: Dynamically adjust the core drag coefficient according to the preset logic. The preset logic includes:

[0054] Timed triggering to dynamically adjust the core resistance coefficient, such as automatically triggering after the air conditioner has been running for 3000 hours;

[0055] Active triggering to dynamically adjust the core resistance coefficient, manual active triggering;

[0056] Abnormal triggering dynamically adjusts the core resistance coefficient, such as when the current pressure difference deviates from the calibrated pressure difference by more than ±15%, or when the current fan speed deviates from the fan speed N_initial in the lookup table by more than ±10%.

[0057] After triggering, adjust the fan speed until the current pressure difference is equal to the pressure difference calibrated in step 2. Calculate the real-time air volume corresponding to the current pressure difference. Obtain the calibrated air volume corresponding to the current pressure difference based on the core resistance coefficient and air volume curve. Then, dynamically adjust the core resistance coefficient based on the ratio of the real-time air volume to the calibrated air volume. The methods include:

[0058]

[0059] Where K actual is the updated core resistance coefficient, Q_initial is the calibrated air volume, Q_current is the real-time air volume, K lab is the target core drag coefficient;

[0060] Update the core resistance coefficient in the control unit for daily air volume calculation, then exit the correction mode, restore the normal operation control logic of the fan, and record the time of this correction, the core resistance coefficient before and after correction, and the environmental parameter log.

[0061] Step 5. Air volume output control and alarm: The PID control module is used to control the fan speed to meet the target air supply and exhaust volume according to the dynamically adjusted core resistance coefficient. During operation, the fan speed is adjusted in real time according to the set air volume, and the supply and exhaust air volumes are always controlled to run according to the set values ​​to ensure stable operating air volume, avoid air volume deviation caused by filter blockage and other reasons, and cause the indoor pressure balance to be destroyed. At the same time, it can ensure that the air volume is supplied on demand, which greatly improves the stability and energy saving of the fresh air system.

[0062] An alarm mechanism is established based on the fan speed and pressure difference. When the alarm mechanism requirements are met, a corresponding alarm is issued. Specifically, the alarm mechanism includes:

[0063] Core blockage warning mechanism: Real-time monitoring of the pressure difference deviation from historical data at a specific fan speed. If the pressure difference increase exceeds the preset threshold, a cleaning alarm is triggered;

[0064] Core air leakage warning mechanism: Real-time monitoring of the pressure difference deviation from historical data at a specific fan speed. If the pressure difference drops beyond a preset threshold, an air leakage alarm is triggered.

[0065] Pipeline system blockage warning: Real-time monitoring of the deviation between the air volume and historical data at a specific fan speed. If the air volume drop exceeds the preset threshold, a pipeline blockage alarm is triggered;

[0066] Pipeline system air leakage warning: Real-time monitoring of the deviation between the air volume and historical data at a specific fan speed. If the air volume increase exceeds the preset threshold, the pipeline air leakage alarm is triggered.

[0067] Further explanation: the alarm mechanism also includes data cross-validation and sensor early warning: it is linked with the fan speed and power data to verify the rationality of the air volume, prevent the failure of a single sensor, and trigger the corresponding sensor alarm when a single data anomaly occurs.

[0068] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for measuring the air volume of a fresh air unit based on the pressure difference of a heat recovery core, characterized by: The specific steps include: Step 1: Pressure difference measurement: Place pressure difference sensors and temperature sensors at the air inlet and outlet of the clean heat recovery core of the heat recovery fresh air unit to collect pressure difference and temperature data; Step 2: Resistance calibration: Use standard air volume measurement equipment to obtain the pressure difference of the clean heat recovery core under different air volumes. Perform fitting processing on the pressure difference under different air volumes to obtain the core resistance coefficient and air volume curve, completing the core resistance coefficient calibration and pressure difference calibration; Step 3: Calculate wind speed: Obtain temperature and pressure compensation based on temperature data and calculate wind volume; Step 4: Dynamic correction of core resistance coefficient: Adjust the fan speed according to the preset logic until the current pressure difference is equal to the pressure difference calibrated in step 2, calculate the real-time air volume corresponding to the current pressure difference, obtain the calibrated air volume corresponding to the current pressure difference based on the core resistance coefficient and air volume curve, and dynamically adjust the core resistance coefficient based on the ratio of the real-time air volume to the calibrated air volume; Step 5. Air volume output control and alarm: Use the PID control module to control the fan speed to meet the target air supply and exhaust volume based on the dynamically adjusted core resistance coefficient, and establish an alarm mechanism based on the fan speed and pressure difference. When the alarm mechanism requirements are met, the corresponding alarm will be issued.

2. The method for measuring the air volume of a fresh air unit based on the heat recovery core pressure difference according to claim 1, characterized in that: The method of collecting the pressure difference includes: Several pressure difference sensors are respectively set up upstream and downstream of the fresh air channel and the exhaust channel of the heat recovery core, and the average value of the several pressure difference sensors is used as the calculated pressure difference.

3. The method for measuring the air volume of a fresh air unit based on the heat recovery core pressure difference according to claim 1, characterized in that: The core resistance and air volume curve includes: K=f(Q) Where K is the core resistance coefficient and Q is the air volume.

4. The method for measuring the air volume of a fresh air unit based on the heat recovery core pressure difference according to claim 1, characterized in that: The method of obtaining temperature and pressure compensation according to temperature data includes: Where ρ is the gas density, P is the absolute pressure of the gas, R is the gas constant, which is 287 j / (kg·T), and T is the absolute temperature of the gas.

5. The method for measuring the air volume of a fresh air unit based on the pressure difference of a heat recovery core according to claim 4, characterized in that: The formula for calculating the air volume in step 3 is: Where Q is the air volume, K is the core resistance coefficient, ΔP is the pressure difference, T is the absolute temperature of the gas, and P is the absolute pressure of the gas.

6. The method for measuring the air volume of a fresh air unit based on the heat recovery core pressure difference according to claim 1, characterized in that: The preset logic in step 4 includes: timing triggering dynamic adjustment of the core resistance coefficient, active triggering dynamic adjustment of the core resistance coefficient, and abnormal triggering dynamic adjustment of the core resistance coefficient, wherein the abnormal triggering dynamic adjustment of the core resistance coefficient includes: The deviation between the current differential pressure and the calibrated differential pressure is greater than ±15%.

7. The method for measuring the air volume of a fresh air unit based on the heat recovery core pressure difference according to claim 1, characterized in that: In step 4, the method of dynamically adjusting the core resistance coefficient according to the ratio of the real-time air volume to the calibrated air volume includes: Where K actual is the updated core resistance coefficient, Q_initial is the calibrated air volume, Q_current is the real-time air volume, K lab is the target core drag coefficient.

8. The method for measuring the air volume of a fresh air unit based on the heat recovery core pressure difference according to claim 1, characterized in that: The alarm mechanism in step 5 includes: Core blockage warning mechanism: Real-time monitoring of the pressure difference deviation from historical data at a specific fan speed. If the pressure difference increase exceeds the preset threshold, a cleaning alarm is triggered; Core air leakage warning mechanism: Real-time monitoring of the pressure difference deviation from historical data at a specific fan speed. If the pressure difference drops beyond a preset threshold, an air leakage alarm is triggered. Pipeline system blockage warning: Real-time monitoring of the deviation between the air volume and historical data at a specific fan speed. If the air volume drop exceeds the preset threshold, a pipeline blockage alarm is triggered; Pipeline system air leakage warning: Real-time monitoring of the deviation between the air volume and historical data at a specific fan speed. If the air volume increase exceeds the preset threshold, the pipeline air leakage alarm is triggered.

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