Logic and Practical Case Analysis of SANYO DENKI San Ace Forward/Reverse Cooling Fans-Capital-Cooling fan manufacturer

SANYO DENKI San Ace "forward/reverse" cooling fans mainly refer to two types of products with different technological logics, which have essential differences in principle and application scenarios.

Reversible Flow Fan

The core logic of this fan is to control the impeller of a single fan to rotate in two directions through an external signal, thereby achieving a switch in airflow direction.

Working Principle: Through external signals such as PWM, the fan can be controlled to rotate clockwise or counterclockwise, achieving the two functions of "air supply" and "exhaust".

Core Advantages:

（1）Dual-Purpose in One Unit: One fan can replace two sets of fans responsible for forward and reverse ventilation in traditional solutions, saving installation space and cost.

（2）Balanced Performance: Whether rotating forward or reverse, it can provide almost the same airflow and static pressure performance, ensuring stable cooling efficiency.

（3）Intelligent Control: Supports PWM speed regulation, allowing precise control of airflow direction and volume based on demand, achieving energy saving and noise reduction.

Practical Cases

This type of fan is particularly suitable for scenarios that require periodic changes in airflow direction.

（1）Beverage Vending Machines/Food Display Cabinets: During daytime refrigeration, the fan blows air forward to promote cold air circulation; at night or when defrosting is needed, the fan blows air in reverse for dehumidification or auxiliary defrosting.

（2）Home Ventilation Systems: Can automatically switch between air intake (introducing fresh air) and exhaust (expelling stale air) modes based on indoor air quality, achieving intelligent ventilation.

Counter Rotating Fan

The core logic of this fan is to integrate two sets of independent, counter-rotating impellers within the same fan frame.

Working Principle: The front and rear sets of impellers rotate at high speed in opposite directions. The rear-stage impeller rectifies and accelerates the airflow generated by the front-stage impeller, causing the airflow to superimpose, thereby significantly increasing wind pressure and volume.

Core Advantages:

（1）Ultra-High Static Pressure: This is its most prominent advantage. It can generate static pressure far exceeding that of ordinary fans, powerfully penetrating environments with extremely high wind resistance, such as high-density heatsink fins and filters.

（2）Compact and Efficient: Within limited space (e.g., 1U/2U servers), it provides static pressure approaching that of centrifugal fans, solving the heat dissipation challenge for high-density equipment.

（3）Stable Airflow: The counter-rotating design can effectively reduce airflow turbulence and vortices, helping to lower noise while improving efficiency.

Practical Cases

This type of fan is designed specifically to meet extreme heat dissipation challenges, especially for equipment with compact space and high thermal density.

（1）GPU Servers/Data Centers: Inside server chassis, heatsink fins are dense, and airflow path resistance is immense. With its ultra-high static pressure, the counter-rotating fan can ensure sufficient cold air penetrates the heatsink to carry away the massive heat generated by core components like CPUs and GPUs.

（2）Communication Equipment and Power Modules: In industrial inverters, communication base stations, and other equipment, space is limited and heat generation is concentrated. Using a counter-rotating fan can significantly improve heat dissipation capability without increasing the number or size of fans, ensuring stable equipment operation.

（3）Energy Storage Cabinets (Sealed + Safety): Maintains long-term unobstructed airflow paths and stable temperature control capability.

Comparison Results

Comparison Item	Reversible Flow Fan	Counter Rotating Fan
Core Logic	Switches airflow direction: Single impeller rotates bidirectionally.	Enhances static pressure: Dual impellers rotate in opposite directions.
Main Purpose	To achieve switching between air supply and exhaust functions.	To provide powerful wind force to penetrate high wind resistance in limited space.
Typical Application	Vending machines, ventilation systems (need to change airflow direction).	Servers, communication equipment (need to overcome high wind resistance).

One Fan Replaces Two: Structural Optimization + Cost Reduction

Traditional Dual-Airflow Solution:

Requires 2 sets of fans (air intake + air exhaust / forward & reverse airflow paths).

Forward/Reverse Solution:

A single fan achieves bidirectional airflow.

Direct Benefits:

Reduced BOM cost

Reduced PCB/structural space

Reduced wiring harness complexity

Item	Traditional Fan	Forward/Reverse Fan
Initial Cost	Low	Slightly Higher
Number of Fans	Many	Few
Maintenance Frequency	High	Low
Failure Rate	Medium	Low
Lifecycle Cost	High	Significantly Reduced

Engineering Selection Recommendations

When conducting engineering selection, the core is to match the fan's performance with the device's thermal management needs.

A common misconception is to focus only on airflow (CFM) while ignoring static pressure (Pa).

In reality, fan performance must be evaluated in conjunction with the device's airflow path characteristics.

（1）Clarify the Equipment's Heat Dissipation Scenario

Scenario Type	Airflow Path Characteristics	Primary Selection Indicator	Recommended Fan Type
High-Impedance Scenario	Complex airflow path with dense heatsink fins, filters, etc., resulting in high airflow resistance.	High Static Pressure (Pa)	Counter Rotating Fan
Low-Impedance Scenario	Unobstructed airflow path with low airflow resistance, e.g., open-chassis.	High Airflow (CFM)	Conventional High-Airflow Axial Fan
Requires Airflow Switching	Periodic air supply and exhaust are needed.	Bidirectional Airflow Function	Reversible Flow Fan
Outdoor/Harsh Environment	Presence of dust, water, extreme temperatures, etc.	High Ingress Protection (IP) Rating	Waterproof and Dustproof Fan (e.g., IP68)

（2）Interpretation of Key Performance Parameters

Airflow and Static Pressure (CFM & Pa)

Core Point: In high-impedance scenarios, even with high airflow, if static pressure is insufficient, the effective airflow passing through the heatsink will drop sharply, leading to cooling failure. For example, SANYO DENKI's counter-rotating fans (such as the 9GV series) can reach a static pressure of 1400Pa, specifically designed to penetrate high-resistance airflow paths.

Noise Level (dB(A)):

Fan noise mainly comes from wind shear and motor vibration. In medical equipment, office environments, or data centers with high silence requirements, noise must be a key consideration. Generally, under the premise of meeting static pressure and airflow requirements, a model with lower noise should be selected.

Power Consumption and Energy Efficiency (W):

For equipment running 7x24 hours, fan power consumption directly affects overall energy consumption. Choosing a fan with lower power consumption for equivalent performance can significantly reduce operating costs.

（3）Intelligent Control and Reliability Features

Modern cooling solutions not only require "being able to dissipate heat" but also "intelligently and reliably dissipating heat".

PWM Intelligent Speed Regulation:

Through PWM signals, the system can adjust fan speed in real-time based on data from temperature sensors. It reduces speed under low load to save energy and reduce noise, and runs at full speed under high load to ensure heat dissipation.

Status Monitoring (FG/Alarm):

Speed Signal (FG): Outputs the fan's real-time speed, allowing the system to monitor if the fan is working properly.

Stall/Low-Speed Alarm: When the fan is jammed by foreign objects or the speed is abnormal, it can send an alarm to the system for early warning, preventing equipment damage from overheating.

（4）Environmental Adaptability and Lifespan

Ingress Protection (IP Rating): For scenarios like outdoor cabinets, charging piles, and energy storage cabinets, it is essential to choose fans with the corresponding IP rating. For example, IP68-rated fans can effectively prevent dust ingress and prolonged water immersion, ensuring reliability in harsh environments.

Operating Temperature and Lifespan:

Confirm whether the fan's rated operating temperature range can cover the highest/lowest ambient temperatures the equipment might encounter. Industrial applications typically require fans to maintain a lifespan of tens of thousands of hours even at 60℃ or higher temperatures.

Capital Technology Co., Limited is the chief agent of SANYO DENKI, one of the leading enterprises of the cooling fan industry.

We are a factory who also have our own independent brand CAPITAL product series.

The main products are cooling fan, DC/AC fan, radiator, filter, reactor etc.

We can provide customer with the most professional and perfect technical support, welcome to contact me at anytime at rainlee@szcpt.com.

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