1. Working Principle: Miniature Axial Flow System with Noise Reduction Design

The axial muffin fan, also known as the mini axial fan or muffin fan, is a miniaturized axial flow fan specially designed for noise-sensitive scenarios. Its core working principle is based on the axial flow air supply principle, and on this basis, the structural design is optimized to achieve the effect of low noise. Compared with ordinary axial fans, the muffin fan has a more compact structure, and its working process can be divided into three stages: motor drive, impeller air supply and noise reduction optimization.

In terms of motor drive, the axial muffin fan usually adopts a small DC motor or AC motor, and the AC version also has a 220V specification, but the DC version (such as 12V, 24V) is more common. Taking the AC 220V muffin fan as an example, its motor adopts a micro single-phase asynchronous motor with a simplified structure, which uses a capacitor phase-shifting or shaded pole starting method to drive the rotor to rotate. The motor rotor is directly connected to the impeller, and the rotation of the rotor drives the impeller to rotate at high speed. Due to the miniaturization of the motor, its power consumption is very low, usually only 1-10W, and the rotation speed is between 1500-5000 rpm, which can generate sufficient air volume under the condition of small size.

In the aspect of impeller air supply, the muffin fan adopts a special miniaturized impeller design. The impeller is usually made of engineering plastics (such as ABS, PBT) with light weight and high strength, and the number of blades is 3-9 pieces. The blades adopt a streamlined airfoil profile, and the angle of attack is carefully designed to reduce the airflow turbulence during rotation. When the impeller rotates, the blades push the air to flow axially, and the air inlet and outlet of the fan are designed as a circular or square structure with a large opening ratio, which ensures the smooth flow of air and reduces the airflow resistance. At the same time, the gap between the impeller and the fan housing is very small (usually 0.1-0.5mm), which can reduce the air leakage between the impeller and the housing, improve the air supply efficiency, and avoid the noise caused by the airflow passing through the gap.

The most distinctive feature of the muffin fan is its noise reduction optimization design, which is also the origin of its name "muffin" (meaning quiet). The noise reduction design is mainly reflected in three aspects: first, the impeller adopts a low-noise structure, the blade edge is rounded, and the surface is smooth, which can reduce the aerodynamic noise generated by the airflow separation at the blade edge; second, the fan housing is designed with a sound-absorbing structure, and some models are equipped with a sound-absorbing foam layer inside the housing, which can absorb part of the mechanical noise and airflow noise; third, the motor adopts a silent bearing (such as ball bearing with low friction coefficient), which reduces the mechanical noise generated by the rotation of the bearing. In addition, the overall structure of the muffin fan is compact, the vibration during operation is small, and the vibration noise is further reduced by means of shock-absorbing pads or elastic connections.

It is worth noting that the airflow of the muffin fan is relatively concentrated, which is suitable for local targeted heat dissipation. Its working principle also pays attention to the balance between air volume and noise. Under the condition of the same size, increasing the speed can improve the air volume, but it will also increase the noise. Therefore, the design of the muffin fan usually takes low noise as the primary goal, and optimizes the aerodynamic performance to ensure sufficient air volume while controlling the noise.

2. Key Specifications: Miniaturization and High Performance as the Core

The specifications of the axial muffin fan are mainly characterized by miniaturization, and the core technical parameters include size, air volume, static pressure, noise, power, speed, etc. These parameters are more refined than ordinary axial fans, and each parameter is closely related to the application effect of the fan in miniaturized equipment.

Size is the most intuitive specification parameter of the muffin fan. Its overall size is usually between 20mm × 20mm × 6mm and 120mm × 120mm × 38mm, and the common sizes are 40mm × 40mm × 10mm, 60mm × 60mm × 20mm, 80mm × 80mm × 25mm, etc. The size is usually expressed by the length × width × height (for square fans) or diameter × height (for circular fans). The small size makes the muffin fan easy to install in the narrow space inside the equipment, such as the gap between the circuit board and the shell of the electronic equipment.

Air volume is an important parameter to measure the heat dissipation capacity of the muffin fan. Due to its small size, the air volume is relatively small, usually between 2-50 CFM (cubic feet per minute) or 3.4-85 m³/h. For example, the 40×40×10mm muffin fan has an air volume of about 5 CFM (8.5 m³/h), which is suitable for heat dissipation of small electronic components such as CPU chips; the 80×80×25mm muffin fan has an air volume of about 30 CFM (51 m³/h), which can be used for heat dissipation of small power supplies and communication modules. The air volume of the muffin fan is usually tested under the condition of zero static pressure, because it is mainly used for direct heat dissipation without complex air duct resistance.

Static pressure of the muffin fan is relatively low, usually between 2-20 Pa, which is suitable for scenarios with small airflow resistance. For example, when the fan is directly installed on the surface of the heat sink, the static pressure only needs to overcome the resistance of the heat sink fins. If the application scenario has a certain air duct resistance (such as installing a filter), it is necessary to select a muffin fan with higher static pressure to ensure the air volume.

Noise is the core competitive advantage of the muffin fan, and its noise value is usually between 15-35 dB(A), which is much lower than that of ordinary axial fans (30-45 dB(A)). For example, the 60×60×20mm low-noise muffin fan has a noise of only 20 dB(A) at rated speed, which is equivalent to the sound of breathing, and will not cause noise interference to the environment. The noise of the muffin fan is tested in an anechoic chamber, which includes aerodynamic noise, mechanical noise and electromagnetic noise. The excellent noise reduction design makes it the first choice for noise-sensitive scenarios such as medical equipment and office equipment.

Power and speed are closely related to the performance of the muffin fan. The power of the AC 220V muffin fan is usually between 1-8W, and the speed is between 1500-4500 rpm. For example, the 40×40×10mm AC 220V muffin fan has a power of 2W and a speed of 3000 rpm; the 80×80×25mm model has a power of 6W and a speed of 2500 rpm. Under the same size, the higher the speed, the larger the air volume and the higher the noise; the lower the speed, the smaller the air volume and the lower the noise. Therefore, when selecting, it is necessary to balance the air volume and noise according to the actual needs.

In addition, the protection level, operating temperature range and service life are also important specification parameters of the muffin fan. The protection level is usually IP20-IP54, among which IP54 models are suitable for dusty environments; the operating temperature range is -10℃ to 60℃, which can meet the working needs of most electronic equipment; the service life is usually 30000-60000 hours, and the models using ball bearings have longer service life than those using sleeve bearings.

3. Application Scenarios: Focus on Miniature Equipment and Noise-Sensitive Fields

The axial muffin fan is mainly used in scenarios that require miniaturized heat dissipation and low noise, such as electronic equipment, medical equipment, office equipment, household appliances and other fields. Its small size and low noise characteristics make it irreplaceable in the heat dissipation of core components of small equipment.

In the field of electronic equipment, the muffin fan is widely used in heat dissipation of computers, communication equipment, industrial control equipment and other products. For example, in the CPU heat dissipation system of a notebook computer, a small muffin fan (such as 40×40×10mm) is used to cooperate with the heat pipe and heat sink to form a forced air cooling system. The fan operates at a speed of 3000 rpm, with an air volume of 5 CFM and a noise of 25 dB(A), which can quickly take away the heat generated by the CPU and ensure the stable operation of the notebook computer. In the communication module (such as 5G router), the muffin fan is installed inside the module to dissipate heat for the high-power chip. The AC 220V muffin fan can be directly connected to the mains power supply of the router, avoiding the trouble of additional power conversion.

In the field of medical equipment, the muffin fan is used in equipment such as medical monitors, ultrasonic diagnostic instruments, and laser treatment equipment. These equipment have high requirements for noise, and the working environment is usually a quiet hospital ward or clinic, so low-noise heat dissipation components are required. For example, the medical monitor needs to work continuously for 24 hours, and the internal power supply module and signal processing module will generate heat. A 60×60×20mm muffin fan with a noise of 20 dB(A) is used for heat dissipation. The fan operates stably, and the noise is almost inaudible, which does not affect the work of medical staff and the rest of patients. At the same time, the muffin fan with IP54 protection level can prevent the entry of dust and droplets, ensuring the cleanliness and safety of the medical equipment.

In the field of office equipment, the muffin fan is used in printers, copiers, scanners and other equipment. These equipment generate heat during the working process (such as the fuser of the printer), and need to be dissipated in time to avoid paper jams or equipment failures caused by overheating. For example, the fuser of a laser printer works at a high temperature (about 180℃), and a 80×80×25mm muffin fan is installed near the fuser to blow cold air to the fuser. The fan has an air volume of 30 CFM and a static pressure of 15 Pa, which can effectively reduce the temperature of the fuser and ensure the printing quality. The low noise of the fan also ensures that the office environment is not disturbed.

In the field of household appliances, the muffin fan is used in small household appliances such as microwave ovens, coffee machines, and air purifiers. For example, the control panel of the microwave oven will generate heat during use, and a small muffin fan (such as 30×30×8mm) is used to dissipate heat for the control panel. The fan is small in size and can be installed in the narrow space of the microwave oven shell. The AC 220V model can be directly connected to the power supply of the microwave oven, which is convenient and reliable. In the small air purifier, the muffin fan is used to drive the air to pass through the filter screen, and its low noise ensures that the air purifier can be used normally in the bedroom at night.

In addition, the muffin fan is also used in automotive electronics (such as on-board navigation, in-vehicle air conditioners), aerospace equipment (small avionics) and other fields, which fully reflects its wide application prospects in miniaturized and low-noise heat dissipation scenarios.

4. Core Advantages: Miniaturization, Low Noise and High Reliability

Compared with ordinary axial fans and other types of fans, the axial muffin fan has unique advantages in size, noise, reliability and installation, which makes it the preferred heat dissipation component for miniaturized equipment.

First of all, the size is compact and the installation is flexible. The muffin fan has a small overall size, the smallest model can be as small as 20×20×6mm, which can be easily installed in the narrow space inside the equipment, such as between the circuit board and the shell, or inside the module. Its installation method is also very flexible, and it can be fixed by screws, adhesive tapes or buckles. For example, the small muffin fan used in the mobile hard disk box is fixed on the circuit board by adhesive tape, which is simple and fast, and does not occupy too much space. The compact size makes the muffin fan can be applied to various miniaturized equipment, expanding the scope of heat dissipation solutions.

Secondly, the noise is extremely low, and the environmental adaptability is strong. Low noise is the most prominent advantage of the muffin fan. Through the optimization of impeller structure, motor bearing and housing design, its noise can be controlled below 35 dB(A), and the low-noise model can even reach 15 dB(A). This makes the muffin fan very suitable for noise-sensitive scenarios such as bedrooms, offices, and hospitals. For example, the air purifier used in the bedroom uses a muffin fan, which will not affect the user's sleep even if it works continuously at night. Compared with ordinary axial fans, the noise of the muffin fan is reduced by 10-20 dB(A), which is a qualitative improvement in noise performance.

Thirdly, the performance is stable and the reliability is high. The muffin fan adopts a simplified structure, with few parts and high integration, which reduces the probability of failure caused by component matching. The motor uses high-quality bearings and windings, and the impeller is made of high-strength engineering plastics, which can withstand long-term high-speed rotation. The service life of the muffin fan is usually 30000-60000 hours, which is much longer than that of ordinary small fans. For example, the muffin fan used in the industrial control module can work continuously for 5 years (about 43800 hours) without failure, ensuring the stable operation of the industrial control system.

Fourthly, the power consumption is low, and the energy saving effect is good. The muffin fan uses a micro motor, and the power consumption is usually only 1-8W, which is much lower than that of ordinary axial fans (5-50W). For equipment that works continuously for a long time (such as servers, medical monitors), the low power consumption of the muffin fan can greatly reduce the overall energy consumption of the equipment, save electricity costs, and meet the requirements of energy conservation and environmental protection. For example, a server room with 100 servers, each using a 5W muffin fan, consumes only 500W of power per hour for the fan, which is 60% lower than using ordinary 12W axial fans.

5. Selection Points: Focus on Matching Miniature Scenarios and Performance Balance

The selection of axial muffin fans needs to focus on the characteristics of miniaturized application scenarios, and comprehensively consider factors such as size constraints, heat dissipation requirements, noise limits, and power supply conditions. The selection process should follow the steps of "clarifying constraints → confirming performance requirements → matching environmental conditions" to ensure that the selected fan can meet the actual application needs.

The first step in selection is to clarify the size constraints. The installation space of the muffin fan is usually very limited, so it is necessary to first confirm the maximum size of the fan that the equipment can accommodate (length × width × height). For example, if the reserved installation space of the electronic module is 50mm × 50mm × 15mm, then the selected muffin fan size should be less than or equal to this size, such as 40×40×10mm or 50×50×10mm. It should be noted that the installation space should also reserve a certain margin for the fan's power cord and installation accessories to avoid installation difficulties.

The second step is to confirm the core performance requirements, including air volume and noise. Air volume needs to be calculated according to the heat dissipation power of the equipment. The heat dissipation power Q (W) = C × ρ × Qv × ΔT, where C is the specific heat capacity of air (1005 J/(kg·K)), ρ is the air density (1.2 kg/m³), Qv is the air volume (m³/s), and ΔT is the allowable temperature rise (K). Assuming that the heat dissipation power of the electronic component is 50W, the allowable temperature rise is 10K, then Qv = Q/(C×ρ×ΔT) = 50/(1005×1.2×10) ≈ 0.00415 m³/s = 14.94 m³/h. Therefore, a muffin fan with an air volume of not less than 15 m³/h should be selected. Noise needs to be determined according to the application environment. For example, in the bedroom or hospital ward, the noise should be controlled below 25 dB(A); in the office, it can be relaxed to below 35 dB(A).

The third step is to match the power supply conditions and installation method. The muffin fan has AC and DC power supply modes. The AC version includes 220V, 110V and other specifications, and the DC version includes 12V, 24V and other specifications. When selecting, it is necessary to confirm the power supply voltage of the equipment to avoid mismatching. For example, the industrial control equipment usually uses 24V DC power supply, so the 24V DC muffin fan should be selected; the household appliance uses 220V AC power supply, so the 220V AC muffin fan can be directly selected. The installation method should be determined according to the equipment structure. For example, if the equipment has a reserved screw hole, the screw-fixed muffin fan should be selected; if the installation space is limited, the adhesive-fixed model can be selected.

The fourth step is to consider environmental conditions and reliability requirements. Environmental conditions include operating temperature, humidity, dust concentration, etc. For high-temperature environments (such as near the fuser of the printer), the muffin fan with a high-temperature resistant housing and motor should be selected, and the operating temperature range should be above 60℃; for humid environments (such as bathroom appliances), the model with a protection level of not less than IP44 should be selected. Reliability requirements are reflected in the service life and bearing type. For equipment that needs to work continuously for a long time (such as servers), the muffin fan with ball bearings and a service life of more than 50000 hours should be selected; for general household appliances, the sleeve bearing model with a service life of 30000 hours can be selected to reduce costs.

Finally, it is necessary to pay attention to the brand and quality. The quality of the muffin fan has a great impact on the stability of the equipment. Well-known brands (such as Nidec, Delta, Sunon) have stricter quality control in the production process, and the product performance and reliability are more guaranteed. At the same time, these brands can provide detailed technical parameters and after-sales services, which is convenient for users to select and maintain.