Air conditioning flow meter | Types of central air conditioning flow meters

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1. Why is the flowmeter on the air conditioning pipeline smaller than the main pipeline?

The flowmeter on the air conditioning pipeline is smaller than the main pipeline mainly to meet the requirements of measurement accuracy, fluid dynamics characteristics, pressure drop control, cost and installation. The specific reasons are as follows: the measurement principle of the flowmeter (such as vortex street, orifice plate, ultrasonic wave, etc.) requires the fluid flow velocity to be within a specific range (usually 1-10 m/s) to ensure accuracy. If the main pipeline diameter is directly used, the flow velocity may be too low (such as less than 0.5 m/s), resulting in weak sensor signals and increased measurement errors. For example, when the DN100 main pipeline is paired with a DN50 flowmeter, the flow velocity can be increased from 0.3 m/s to 1.2 m/s, meeting the accuracy requirements of most flowmeters (with an error of ± 1%). Shrinkage design increases the flow rate to make the fluid state more in line with the optimal working range of the flowmeter. According to the Bernoulli equation, as the diameter of a pipeline decreases, the fluid velocity increases and the pressure decreases. The flow meter pipeline is thinner than the main pipeline, which can slow down the high-speed turbulent state of the fluid in the main pipeline, allowing it to pass through the flow meter sensor at a moderate speed, thereby obtaining a more stable flow field distribution. This design can reduce measurement deviation caused by uneven flow velocity. For example, orifice flow meters rely on a fixed relationship between flow velocity and pressure difference. After reducing the diameter, increasing the flow velocity can enhance the press

ure difference signal and improve measurement sensitivity. Although pressure drop control and system efficiency reduction design may increase the local pressure drop (Δ P is proportional to the square of the flow velocity), it can be balanced by calculating the pressure loss and measurement requirements. For example, in a certain case where DN80 is reduced to DN40 and the pressure loss increases from 5 kPa to 20 kPa, it is necessary to ensure that the total pressure drop of the system is within the capacity of the pump or compressor to avoid excessive energy consumption. At the same time, reducing the diameter can reduce the risk of impurity deposition in the fluid, especially suitable for media containing particulate matter, and extend the service life of the flowmeter. The cost and installation limitations of large-diameter flow meters are significantly higher (such as the price of DN200 ultrasonic flow meters being about 2.5 times that of DN100), and some operating conditions have limited space (such as narrow equipment rooms). Shrinkage design can reduce equipment procurement costs and also reduce the difficulty of pipeline renovation. For example, when replacing a flowmeter in an existing system, if the main pipeline is DN150, using a DN100 flowmeter can avoid large-scale pipeline replacement and save engineering costs.

2. Types of central air conditioning flow meters

According to the measurement principle, central air conditioning flow meters can be mainly divided into electromagnetic flow meters, turbine flow meters, ultrasonic flow meters, orifice flow meters, volumetric flow meters and other types. Some old models such as pipeline rotor flow meters and plug-in rotor flow meters have been eliminate

Air conditioning flow meter | Types of central air conditioning flow meters

1. Why is the flowmeter on the air conditioning pipeline smaller than the main pipeline?

2. Types of central air conditioning flow meters

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