Side-by-Side Fan Testing:
Selecting the Right Fan Based on Field Performance
Selecting the Right Fan Based on Field Performance
Replacing or upgrading the fans of an Air-Cooled Heat Exchanger (ACHE) can offer
significant improvements in airflow, cooling capacity, energy efficiency and noise
performance. But selecting the right fan is not simply a matter of comparing
datasheets.
Fan diameter, blade profile, blade angle, number of blades, rotational speed, tip
clearance, fan ring geometry and system resistance all influence the actual
performance of a fan once installed in an air cooler.
A fan that performs well on paper does not automatically provide the best
performance in the field.
This is where side-by-side fan testing provides value.
From Catalogue Performance to Actual Performance
Fan manufacturers provide valuable performance data for their products. However, an operating ACHE is not a laboratory test bench.
The fan operates as part of a complete aerodynamic system.
The bundle introduces pressure resistance. Fan rings and inlet geometry influence
airflow distribution. Structural members can disturb the incoming air. Tip clearance affects recirculation. Motor power and transmission limitations restrict the available operating range.
Even environmental and site conditions can influence the result.
For this reason, ENTHALPEX approaches fan upgrades from the perspective of the
complete air-side system, rather than evaluating the fan as an isolated component.
The question is therefore not:
“Which fan has the best specification?”
The relevant question is:
“Which fan configuration performs best in this specific Air-Cooled Heat
Exchanger?”
The Side-by-Side Approach
A side-by-side test allows different fan configurations to be evaluated directly on the equipment for which the upgrade is being considered.
ENTHALPEX first establishes the performance of the existing configuration through a structured baseline measurement.
Depending on the objective of the project, this may include:
- Air velocity and volumetric airflow
- Fan rotational speed
- Motor power consumption
- Static pressure
- Ambient conditions
- Noise levels
- Fan and drive condition
- Fan tip clearance
- Relevant process temperatures and operating conditions
Based on the existing installation, operating requirements and available design
information, ENTHALPEX then selects one or more suitable fan configurations for evaluation.
The selected fan is installed and the measurements are repeated under controlled
and, as far as practically possible, comparable conditions.
The result is a direct before-and-after comparison based on measured field
performance.
More Than Changing the Fan
One of the most important aspects of fan optimization is that the fan itself cannot be considered separately from its installation.
Simply installing a different blade design while maintaining the existing configuration may leave significant performance potential unused.
ENTHALPEX therefore evaluates the complete configuration, including parameters
such as:
Fan diameter and blade profile
Different blade geometries can produce significantly different pressure and airflow characteristics.
Number of blades and blade angle
The configuration must be matched to the required operating point and available motor power.
Rotational speed
Increasing airflow is valuable only when the resulting power demand, mechanical
limitations and noise remain acceptable.
Tip clearance
Excessive clearance between the blade tip and fan ring can result in air recirculation and reduced effective airflow.
Fan ring and inlet geometry
The aerodynamic interaction between the fan and surrounding structure can have a substantial influence on actual performance.
System resistance
Ultimately, the fan must operate against the resistance of the installed heat exchanger bundle and surrounding geometry.
The objective is therefore not to install the most powerful fan.
It is to identify the optimum fan-system configuration.
Independent by Design
There is another important difference in the ENTHALPEX approach.
We are not a fan manufacturer.
ENTHALPEX is an independent Air-Cooled Heat Exchanger specialist and is not commercially tied to a specific fan manufacturer or technology.
This allows the evaluation to start with the requirements of the ACHE rather than with a predetermined product.
Different fan technologies and manufacturers can be considered based on their suitability for the application. The technical evaluation, configuration and field measurements remain independent.
This separation is particularly valuable for asset owners considering a larger fan retrofit.
Instead of selecting a technology first and attempting to demonstrate its benefits afterwards, the process can be reversed:
Measure → Evaluate → Select → Test → Verify → Scale
Test Before You Retrofit
A fan upgrade across an entire air cooler bank can represent a substantial investment.
At the same time, relatively small improvements in airflow can have a meaningful effect on heat rejection capability, particularly when an ACHE is operating close to its thermal limitation during high ambient temperatures.
A side-by-side test provides an opportunity to verify the improvement on a limited scale before committing to a full retrofit.
For example, one fan cell can remain in its existing configuration while another is equipped with the proposed optimized configuration. Their performance can then be measured and compared under similar ambient and operating conditions.
Where required, multiple configurations can be evaluated.
This creates a practical decision gate:
Does the measured improvement justify implementation across the remaining fan cells?
If the answer is yes, the retrofit can proceed with considerably more technical confidence.
If the expected improvement is not achieved, the configuration can be reconsidered before significant capital is committed.
Performance Is Not Just Airflow
The fan configuration producing the highest airflow is not necessarily the best solution.
The optimum configuration depends on the operational objective.
For a thermally constrained ACHE, maximizing airflow and cooling capacity may be the priority.
For another installation, the objective may be to maintain existing airflow while reducing electrical power consumption.
At noise-sensitive locations, acoustic performance may become an important selection criterion.
In other applications, mechanical reliability, maintainability or available motor capacity may limit the possible configurations.
For this reason, ENTHALPEX can evaluate fan configurations against several performance indicators simultaneously:
Airflow — Power — Cooling Performance — Noise — Reliability
The preferred configuration is the one that provides the best overall result for the specific application.
Turning Fan Selection into an Engineering Decision
Fan retrofits should not have to rely solely on assumptions, catalogue curves or vendor claims.
By combining ACHE engineering, independent fan selection and field performance measurements, side-by-side testing turns fan selection into a measurable engineering decision.
It provides asset owners with something particularly valuable before a larger retrofit:
evidence from their own equipment.
At ENTHALPEX, we believe optimization should be demonstrated where it ultimately matters — in the field.
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