Differences between balanced flow meters and porous orifice plates

A balanced flow meter is simply a porous orifice plate; there’s no difference, it’s just called by a different name. However, as the owner, one thing to keep in mind is that standard throttling devices do not require calibration and can be used straight away, whereas balance flow meters are not standard throttling devices and need to be calibrated, which is quite troublesome and requires the cooperation of the manufacturer.

At present, the balance flowmeters produced in China are manufactured by Moore Mensvis in Shanghai; there is also an imported model from Rosemount, a compact orifice plate type that is similar to them

Balance and porosity are features of the new energy-saving type, as they can reduce pressure loss and are better than traditional orifice plates. It’s possible to combine them and choose one with good cost-performance.

I’ve also posted about similar issues, and I saw one friend respond that the balanced flow meter is called an A+K balanced flow meter; it was developed by an American and was originally designed for use in the U.S. space shuttles, before it was made available for commercial use. According to A+K balanced flow meter distributors, porous plate flow meters are based on the A+K design – the principles behind them are similar. Since the A+K balanced flow meter is a non-standard flow meter, it needs to be calibrated, and the calculations have to be sent to the United States for processing. However, it features high precision, a large range ratio, and small front and rear pipe sections.

Balance flow meters and porous orifice flow meters belong to the category of differential pressure flow meters; they are upgraded versions of orifice flow meters. While they share some similarities, there are also differences between them. Their basic principles are both based on Bernoulli’s equation and the continuity equation. The technical capabilities of domestic manufacturers of porous orifice plate flowmeters vary greatly. Calculations are mostly carried out based on the standards for orifice plates, with a lack of experimental data; there is no basis for determining the layout of the orifices. Their performance is essentially equivalent to that of ordinary orifice plates – it’s just a different presentation of the same concept. Eiga Fluid Control (Shanghai) Co., Ltd. has introduced the American A+Qmc balanced flow meter, which is manufactured by an authorized manufacturer in the United States. The A+Qmc balanced flow meter is a patented product manufactured by A+Flow, a company under NASA in the United States. It originated from the need to measure liquid oxygen in the main engines of space shuttles; based on principles of fluid dynamics, simulation data, and experimental results, it features an optimal hole layout designed to ensure equilibrium of kinetic energy and momentum. It is thus a high-performance flow meter.

I originally thought that the “balance” in a flow meter referred to a balance between measurement accuracy and energy consumption; it’s only now that I’ve learned it actually means “kinetic energy balance and momentum balance”. Could you please explain this in detail? Thank you! Additionally, how should “adopting a reasonable opening layout at equal Reynolds numbers” be understood? A certain Reynolds number corresponds to a fluid flowing at a specific velocity; when the Reynolds numbers are equal, it means that there is a particular opening arrangement corresponding to that flow velocity. Conversely, does this mean that for a flow meter with a specific opening arrangement, optimal accuracy can only be achieved for flow rates within this \"corresponding velocity\" range? Does the accuracy drop sharply when the flow rate exceeds a certain range?

This relates to the issue of hole distribution based on fluid dynamics; it is a corporate secret. If it were made public or commercialized, the company would lose its competitiveness. I can give a general overview of it. The flow field distribution across the pipe cross-section is uneven; the flow velocity is highest at the center of the pipe and lowest at the edges. These differences in flow velocity result in different Reynolds numbers. Differential pressure flow meters use the Reynolds number to reflect the flow field, whereas balanced flow meters employ a properly arranged porous structure to regulate the flow field, ensuring that the flow passing through the meter is balanced and streamlined, thereby reducing vortices and keeping the Reynolds number equal in each orifice. When the Reynolds numbers are equal, the flow rates are also equal, resulting in stable and reliable differential pressure signals. Therefore, it is possible to use multiple pressure measurement points as part of a redundant design. When the Reynolds number is too low, the performance of a balanced flow meter suffers significantly; at such times its discharge coefficient becomes unstable. When the Reynolds number reaches a certain value, this discharge coefficient stabilizes. If the Reynolds number is too high and the flow velocity is too fast, the flow velocity through the orifice increases further, and at that point it becomes necessary to consider the possibility of noise... Genuine balanced flow meters indeed require a certain level of technical expertise. Many manufacturers in China use a random distribution of orifices, without any theoretical basis or experimental data; they employ algorithms based on orifice plates, and the calibrations obtained are only temporarily valid. The range, performance, and accuracy of such devices are not on par with those of genuine balanced flow meters. At least in our country, no enterprise is capable of competing with those in the United States. Currently, two domestic companies have introduced products from the U.S., obtaining technical rights, patents, and production licenses there. The A+QMC balanced flow meter produced by Aiga Fluid Control (Shanghai) Co., Ltd. has gained great popularity in the market in recent years and is widely used. The A+K balanced flowmeter industry is on the decline; its former glory is gone, and as the market shrinks, it has gradually shifted focus and stopped dedicating itself to advancing balanced flowmeter technology.

Thank you for the introduction; I see that there are such significant technical differences between the two types of flowmeters, differences that cannot be reflected in their appearance or structure at all.

The balanced flow meter is a new type of differential pressure flow meter developed by the U.S. **National Aeronautics and Space Administration (NASA)** for measuring liquid oxygen, the fuel used in the main engines of space shuttles. It represents the most advanced differential pressure flow meter available today for industrial process control and measurement. Its design was based on thermodynamic modeling, actual flow data, and flow simulations; a specialized software tool was also developed for selection purposes. Four years of research were invested, with a cost of 10 million dollars, and over 1,000 prototype units were created, generating more than 110,000 sets of actual flow data. This flow meter was introduced to the Chinese market in 2008. The authorized manufacturing company in China at present is \"Aiga Fluid Control (Shanghai) Co., Ltd.\\", with the brand name \"A+QMC\“. The so-called balance flow meters available in China are not true balance flow meters; in practice, they use the calculation methods associated with orifice plates, and their performance is equivalent to that of orifice plates.