Common Issues in the Energy-Efficient Design of Domestic Air Conditioning Package Fans

Common Issues in the Energy-Efficient Design of Domestic Air Conditioning Package Fans

1. The Impact of Inaccurate Calculations of Duct Network Resistance for Air Conditioning Package Fans ① Causes of inaccurate calculations of rated duct network resistance: Duct network resistance for air conditioning package fans was not carefully calculated, and resistance coefficients were not used correctly; the effective radius of the system was unreasonable; there was a lack of valid random standards for selecting specific types of air conditioning package fans; and construction supervision overlooked the impact of design changes made on-site during the construction process. The discrepancy between calculated results and actual losses exceeds 30%. The selected rated performance does not align with actual operating performance, and the actual operating performance is subject to variation. When the calculated resistance exceeds the actual requirement, the airflow generated by the fan’s operation causes a significant increase in actual power consumption. Consequently, total pressure efficiency decreases, and the motor’s rated output is reduced. Under overload conditions, the motor may burn out. Changes in the flow curve of the air conditioning package fan have almost no effect. On the contrary, this will inevitably lead to a reduction in operating flow rate, actual power consumption, and fan efficiency. At the same time, as the flow rate decreases, the velocity within the air ducts of the dust collection system will decrease, thereby promoting dust accumulation. Under these conditions, the fan operates under light load, with low efficiency, and without long-term energy savings. (2) Consequences of an incorrect total pressure rating for an air conditioning package fan: When handling exhaust gases from high-temperature furnaces, if the negative pressure of the selected induced draft fan is too high, the furnace’s normal thermal equilibrium will collapse. As the induced air volume increases, combustion or heating within the furnace will be disrupted, resulting in increased energy loss from the heat source. If an induced draft fan is used to exhaust dust-laden exhaust gases, it will operate under negative pressure. Adequate sealing of the pollution source can effectively prevent the spread of harmful pollutants. For example, if the fan’s negative pressure is too high, the intake of materials from the pollution source will increase in various locations, leading to increased wear on the dust collection ducts, higher processing capacity, and material falling from the hopper of the negative-pressure dust collector, making unloading difficult. Consequently, during operation, the machine must be stopped intermittently and periodically to discharge materials. If rainwater or moisture is drawn in through the flange at the bottom of the duct, the material inside the duct will solidify, hindering discharge. 2. Selection of a Fan Capable of Handling Load Fluctuations Since energy and raw material consumption in manufacturing processes fluctuate cyclically, the temperature inside the furnace varies significantly. As a result, the volume of flue gas generated within the furnace fluctuates by 20–30%. Forward-curved fans are not suitable for induction-type air conditioning package fans because their output curve is very steep. If pressure losses in the ductwork network fluctuate significantly, the motor is prone to overload during operation, posing a risk of burnout. Therefore, please select a backward-curved air conditioning package fan. 3. Select an air conditioning unit fan with the appropriate installed capacity. The motor’s power rating should not be too large or too small. If it is too large, the motor will mostly operate under light load, reducing the power factor and wasting electricity. Conversely, if the motor is overloaded, its temperature will frequently rise. This accelerates insulation aging, shortens service life, and makes starting difficult.