Heat Exchangers vs. Cooling Fans: Which Determines GPU Server Cooling Efficiency?-Capital-Cooling fan manufacturer

This is an excellent question. Simply put, neither the heat exchanger nor the cooling fan alone determines the cooling efficiency of a GPU server. Instead, they are two indispensable parts of a tightly coordinated system.

You can imagine the entire cooling system as a team: the heat exchanger is responsible for "absorbing and transferring" heat, while the cooling fan is responsible for "blowing it away." A weakness in either side becomes a bottleneck for the entire system.

Heat Exchanger without a Fan ≈ Ineffective

Fan without a Heat Exchanger ≈ Inefficient Air Cooling

Division of Labor and Cooperation: Indispensable

1.Heat Exchanger

Role: The Heat Mover. The core component determining the "upper limit."

Working Principle: Its core task is to efficiently absorb heat from the GPU chip and transfer it to a medium (air or liquid) where it can be carried away. In air cooling systems, it is usually a metal block with dense fins; in liquid cooling systems, it is the "cold plate" in direct contact with the GPU.

Key Metrics: Thermal conductivity of the material (e.g., copper is better than aluminum), contact area with the GPU, and surface area of fins or microchannels.

Core Challenge: High-performance heat exchangers = High Airflow Resistance.

Denser fins ❄ → Higher air resistance ⚠ → Higher requirements for fans

2.Cooling Fan

Role: The Heat Expeller.

Working Principle: By forcing air movement (convection), it rapidly carries away the heat accumulated on the heat exchanger and exhausts it outside the server.

Key Metrics: Airflow (CFM, determines how much heat can be taken away) and Static Pressure (determines how well it can "punch through" dense heat exchanger fins).

Core Challenge: If fan capability is insufficient:

❌ Airflow cannot penetrate the heat exchanger.

❌ Heat accumulates.

❌ GPU throttles or even crashes.

Even the best heat exchanger is useless!

Key Conclusion: Why You Can't Look at Just One Side?

A common misconception is focusing only on fan speed or airflow while ignoring the "impedance" of the cooling system.

High Impedance System: The fins of GPU server heat exchangers are very dense, creating huge resistance as air passes through.

Fan Selection Key: In this case, Static Pressure is more important than Airflow. A fan with high airflow but low static pressure cannot effectively "push" air through dense fins; most of the wind will escape through gaps with less resistance, leading to poor cooling efficiency.

Golden Rule: When selecting a fan for a GPU heat exchanger, don't just look at airflow; you must look at Static Pressure.

Therefore, cooling efficiency is determined by both the "heat exchange capability" and the "effective airflow of the fan under specific impedance." An excellent heat exchanger needs a matched high-static-pressure fan to unleash its full potential.

Scenario	Result
Strong Heat Exchanger + Weak Fan	❌ Cooling Failure
Weak Heat Exchanger + Strong Fan	⚠ Average Efficiency
Strong Heat Exchanger + Strong Fan	✅ Optimal Solution

Conclusion:

Heat Exchanger: Determines "theoretically how much heat can be dissipated."

Fan: Determines "how much heat is actually carried away."

Final Performance = Fan Capability × Heat Exchanger Efficiency

Evolution of Cooling Technology: From Air to Liquid

As the power consumption of GPUs in AI servers continues to climb (single card consumption can exceed 1000W), traditional air cooling is nearing its limits, and liquid cooling is becoming mainstream.

Cooling Method	Core Principle	Advantages	Application Scenarios
Air Cooling	GPU → Heatsink/Heat Pipe → Fan → Hot Air	Low cost, mature tech, simple maintenance	Medium/Low power density servers
Cold Plate Liquid Cooling	GPU → Cold Plate → Coolant → External HX → Fan	High efficiency, lower noise, better PUE	High power density AI servers (Current Mainstream)
Immersion Cooling	Server fully submerged in dielectric coolant	Ultimate efficiency, almost silent, PUE near 1.0	Ultra-high density, extreme efficiency requirements

Notably, even in liquid cooling systems, fans still play a significant role (e.g., cooling the external heat exchangers in cold plate systems), though their workload and design focus have shifted.

How to Optimize GPU Server Cooling?

In addition to hardware selection, daily maintenance and intelligent control are crucial:

Regular Cleaning: Dust on cooling fins and fans severely obstructs airflow, drastically reducing efficiency. Use compressed air for cleaning regularly.

Optimize Airflow Paths: Ensure cables inside the chassis are tidy to avoid blocking airflow, creating efficient "front-to-back" or "bottom-to-top" paths.

Intelligent Speed Control (PWM): Modern server fans generally support PWM speed control, automatically adjusting RPM based on real-time GPU temperature. This ensures cooling performance under high load while reducing noise and power consumption under low load.

SANYO DENKI Fan Engineering Case Studies & Recommendations

Case 1: AI GPU Server Cooling (High Power Density Scenario)

Pain Point: NVIDIA H100/A100 GPU clusters generate massive heat, and server chassis space is compact with high airflow resistance. Ordinary fans have high airflow but cannot "penetrate" thick heatsinks, failing to lower core temperatures.

Solution: Adopt the San Ace 200 9GA Series large-size high-static-pressure fans.

Actual Results:

Strong Penetration: This series provides static pressure up to 1350 Pa, forcing airflow through dense liquid cooling heat exchangers or air cooling fins.

Energy Efficiency: Compared to the previous generation (9GV series), the 9GA series reduces power consumption by approximately 36% while maintaining equivalent airflow and static pressure. For data centers with tens of thousands of fans, this directly lowers PUE values.

Smart Thermal Control: Supports PWM speed control to reduce speed under low load, saving energy and reducing noise.

Case 2: 1U Ultra-Thin Server Cooling (Extreme Space Scenario)

Pain Point: 1U servers are only 44.45mm high, packed with CPUs, GPUs, and memory, leaving minimal space for fans (usually only 40mm thickness). Airflow channels are narrow with extremely high resistance.

Solution: Adopt the San Ace 36 9HV Series high-speed "blower" fans.

Actual Results:

Ultra-High Speed: Speeds reach 32,500 RPM. Despite the small size (36mm), they generate an amazing 1400 Pa static pressure.

Solving Heat Buildup: This "small body, big power" characteristic is specifically designed to solve heat accumulation in narrow spaces, preventing CPU/GPU throttling due to overheating.

Case 3: Industrial & Medical Equipment (High Reliability/Low Noise Scenario)

Pain Point: Industrial environments have high ambient temperatures (possibly exceeding 60℃) and require 24/7 operation; medical equipment requires low noise.

Solution: Adopt the San Ace 40 9RA Series or Counter Rotating Series.

Actual Results:

Long Life: The 9RA series lifespan reaches 60,000 hours in 60℃ environments, significantly reducing maintenance costs.

Low Noise: The newly released 9RA series (April 2026) reduces noise by 7 dB(A) compared to the previous generation through structural optimization, suitable for noise-sensitive scenarios.

Counter Rotating Tech: For extremely high impedance scenarios, two sets of impellers rotate in opposite directions, doubling air pressure and solving the problem of traditional fans "failing to blow."

Recommended Model List (Categorized by Application)

To facilitate your selection, we have picked three of the most representative models:

Recommended Scenario	Core Requirement	Recommended Series/Model	Key Parameter Highlights	Reason for Recommendation
GPU Server / Liquid Cooling HX	High Airflow + High Static Pressure	San Ace 200 9GA Series (e.g., 9GA2048P0G001)	Size: 200x70mm Airflow: 30.7 m³/min (1084 CFM) Static Pressure: 1350 Pa Power: 384W (Low Power Ver.)	The current top choice for AI servers. Large size, high efficiency, static pressure sufficient to blow through complex water cooling radiators, and the new model saves 36% power over the old one.
1U/2U Rack Server	Ultra-High Static Pressure + Small Size	San Ace 36 9HV Series (e.g., 9HV3612P3K001)	Size: 36x36x28mm Speed: 32,500 RPM Static Pressure: 1400 Pa	The "King of Pressure" in small sizes. Designed specifically for narrow airflow channels, capable of overcoming extremely high resistance to prevent server crashes.
Industrial Power / Medical	Long Life + Low Noise	San Ace 40 9RA Series (e.g., 9RA1212P4G001)	Size: 120x120x25mm Lifespan: 60k hours (@60℃) Noise: As low as 47dB	The 2026 new主力 (main force). Balances performance and silence, and complies with RoHS environmental standards, suitable for industrial environments with high stability requirements.
Extreme Impedance / Special	Ultimate Pressure	Counter Rotating Series (e.g., 9CRA Series)	Structure: Dual impellers rotating in reverse Feature: Double Air Pressure	The ultimate "trump card" when ordinary fans simply cannot blow (e.g., extremely thick cooling towers).

Selection Advice

1.Look at Static Pressure (Pa), not just Airflow (CFM):
If you are using it for GPU servers or heat exchangers with dense fins, please focus on the static pressure value. The reason SANYO DENKI's 9GA and 9HV series are expensive is that their static pressure is far higher than ordinary fans, allowing them to extract heat from "dead corners."

2.Focus on PWM Intelligent Speed Control:

Most recommended models (such as 9GA2048P0G001) support PWM control. This means you can let the fans run at low speed and quietly during standby via the motherboard or controller, and instantly ramp up speed when the GPU is fully loaded, protecting hardware while saving power.

3.Balance Size and Efficiency:

If your rack space permits, prioritize large-size fans like the 200mm (9GA series) rather than stacking many small fans. Large fans run at lower speeds, are quieter, and have longer lifespans while providing the same airflow.

If you are looking for a cooling solution for a specific device, you can tell us the approximate power consumption (TDP) and installation space dimensions, and we can help you match the model more precisely.

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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