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Technical Features and Development Trends of Fully Premixed Wall-Hung Boilers
Release Date:
2022/05/25 10:15
In recent years, driven by favorable government policies on natural gas and growing public awareness of energy conservation and environmental protection, the wall-mounted boiler market has entered a period of rapid growth.
Condensing wall-mounted boilers stand out for their environmental benefits and have become the heating solution of choice for many households during the winter! Now, let’s take a closer look at the technical features and future trends of fully premixed wall-mounted boilers.
In conventional atmospheric combustion, excessive air is supplied to the furnace (excess air ratio = 1.2–2), resulting in only heat absorption and a corresponding decrease in thermal efficiency.
The water vapor in the flue gas condenses into condensate in the low-temperature section of the heat exchanger, releasing its latent heat of vaporization and thereby enhancing the heat exchanger’s thermal efficiency. In addition, compared with conventional atmospheric combustion, the amount of air entering the furnace is significantly reduced.
The moisture content of the flue gas in the residual air is significantly reduced, leading to a marked decline in condensation efficiency. The thermal efficiency of the air-fired condensing furnace is enhanced through staged combustion and intelligent control. The furnace employs mist-based control, ensuring that the combustion power remains constant throughout the entire process. During the initial heating phase, the rated power can be used for heating. Combustion is regulated by both airflow and intelligent control, with the furnace operating under mist control. Throughout the process, the combustion power does not vary; in the early stages of heating, the rated power can be utilized.
Once the outlet water temperature reaches the set point, the system automatically switches to low-power standby mode to maintain constant-temperature control. Thanks to intelligent control, the combustion output dynamically adjusts to match changes in water temperature, thereby eliminating gas wastage. This type of gas elimination and atmospheric pre-mixing combustion is also known as premixed combustion: the gas is injected through the nozzle, where it mixes with a portion of the incoming air at the nozzle inlet, achieving partial mixing.
A portion of the primary air-mixed gas is ejected from the burner’s flame ports, drawing secondary air into the flame zone and facilitating secondary combustion with the incompletely combusted gases.
The primary and secondary combustion flames are relatively long, with lower flame temperatures; if the heat exchanger is located too close (approximately 130 mm), the flames will come into direct contact with the heat exchanger, leading to incomplete combustion.
Secondary air has a low thermal density due to the negative-pressure combustion within the fan-replacement chamber. The heat exchanger facilitates heat exchange. Fifth, all preheating modes are suboptimal, resulting in unstable combustion and a narrow combustion range. If the gas-to-air ratio is incorrect, ignition becomes exceedingly difficult. Therefore, to ensure the safe and stable operation of the equipment, all installation and commissioning personnel for premix wall-hung boilers must possess professional installation and adjustment skills. Backfiring in any premix combustion system can lead to serious consequences, particularly when using metal-fiber burners.
The burner consists of a pressure-reducing plate and an outer mesh. In a drum-type burner, there are three pressure-reducing plates and an outer mesh plate; during flashback, the gap between the pressure-reducing plate and the outer mesh plate can experience a deflagration.
When metal fibers come into contact with the flashback arrestor, the mixed gas within the arrestor can ignite and cause a flashback. Therefore, when adjusting the combustion conditions, it is essential to stay as far away as possible from the flashback zone. The selection of the wall-mounted boiler is a critical component of the entire system; an incorrect choice can lead to complete failure of the unit. In condensing wall-mounted boilers, the heat exchanger consists of a primary heat exchanger and a condensing heat exchanger. Similarly, in wall-mounted boilers, the heat exchanger is also composed of a primary heat exchanger and a condensing heat exchanger.
The best option is to combine the two approaches, which can reduce heat loss and lower costs. For more information on the technical features and future development trends of fully premixed wall-mounted boilers, please feel free to contact us at any time!
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