Industrial coolers do not always operate under the same conditions as when they were originally designed. Changes in process flow, fluid properties, ambient temperature, fouling, control settings or production requirements can alter the heat duty and available operating margin.

Thermal modelling provides a structured way to assess these changes before equipment is modified, refurbished or replaced. By combining measured plant data with engineering calculations, it can help identify whether the limiting factor is heat transfer capacity, flow, pressure drop, fouling, airflow or another operating constraint.

For existing equipment, the objective is not simply to produce a calculated result. The model should help engineers compare realistic operating scenarios, understand the likely constraint and determine what action should be investigated next.

Establish the Measured Operating Envelope

A useful thermal model begins with representative operating data rather than relying only on the original equipment datasheet.

Depending on the equipment and process, relevant inputs may include:

Process flow rates
Inlet and outlet temperatures
Fluid properties
Cooling-medium conditions
Pressure drop
Ambient temperature
Fouling history
Control valve position
Pump or fan operating conditions
Current production requirements

Data should ideally cover representative operating conditions, including normal production, higher loads and turndown where applicable.

Instrument condition also matters. If temperature, flow or pressure measurements are inaccurate, the resulting heat balance may not represent actual equipment performance. Calibration information, instrument uncertainty and operating trends should therefore be considered before relying on a limited set of measurements.

For applications involving shell and tube equipment, Extran’s shell and tube heat exchanger capability includes thermal and mechanical design for heat transfer equipment.

Validate the Heat Balance Before Making a Decision

Once the operating data has been assembled, the next step is to determine whether the measured conditions produce a credible heat balance.

The review should consider whether the calculated duty is consistent with observed process behaviour. Differences between calculated and measured results may indicate inaccurate instrumentation, incorrect fluid properties, bypass flow, fouling or changes in operating conditions.

This validation step is important because a model can produce precise calculations from inaccurate inputs. The objective is therefore to establish whether the available data provides a sufficiently reliable basis for comparing equipment performance.

Where fouling or equipment condition may be influencing performance, inspection and servicing can provide additional information. Extran’s service and refurbishment capability includes cleaning, repair, rebuilding and modification of heat transfer equipment, as well as on-site servicing where removing equipment from service is impractical.

Compare Multiple Process Scenarios

Changing process conditions rarely occur at a single design point. A thermal review can be more useful when several realistic operating scenarios are compared.

Depending on the application, these may include:

Normal operating conditions
Maximum production demand
Reduced process flow
Changes in fluid concentration or viscosity
Higher summer ambient temperature
Reduced cooling-medium flow
Cold-start conditions
Planned future production increases

Comparing these cases can help identify the condition that creates the smallest operating margin.

For example, a cooler may perform adequately during normal operation but approach its thermal limit during higher ambient conditions. Another unit may have sufficient heat transfer area but encounter excessive pressure drop when process flow increases.

For air cooled equipment, ambient temperature and airflow are important considerations because the temperature difference between the process fluid and cooling air influences heat rejection. Extran’s Air Cooled Heat Exchangers capability covers the design, manufacture, supply, service and maintenance of fin fan coolers.

Identify the Actual Equipment Constraint

The purpose of scenario modelling is to investigate what is limiting performance.

Possible constraints may include:

Insufficient heat transfer area
Excessive pressure drop
Fouling
Insufficient cooling flow
High ambient conditions
Fan performance
Pump limitations
Control valve position
Changed operating conditions
Mechanical condition of the equipment

The distinction matters because replacing equipment is not necessarily the appropriate first response.

If fouling is reducing performance, cleaning or refurbishment may address the problem. If a control limitation is responsible, changing the heat exchanger may not resolve the underlying issue. If the analysis indicates that the existing equipment cannot meet the revised duty under the required conditions, modification or replacement can then be investigated.

Thermal modelling therefore becomes most useful when it supports a defined engineering decision rather than being treated as a standalone calculation.

Compare the Available Intervention Options

Once the likely limiting factor has been identified, practical responses can be compared.

Depending on the findings, options may include:

Cleaning or servicing the existing cooler
Adjusting operating or control conditions
Reviewing fan or pump operation
Modifying the heat transfer surface
Replacing a tube bundle or other component
Increasing available heat transfer area
Replacing the existing equipment
Assessing a different cooling arrangement

Each option should be considered against the process requirement, mechanical condition, pressure limitations, access requirements, shutdown requirements and expected operating conditions.

Extran states that its refurbishment work can include modifications and design checks that help determine whether equipment should be repaired or rebuilt.

For new or modified equipment, Extran’s New Commissions capability includes thermal modelling, mechanical calculations and CAD design. Extran also states that existing installations can be modelled to assess the effect of changing process conditions on equipment output.

Translate the Model Into a Practical Engineering Scope

A modelling result should ultimately produce a clear engineering scope.

The preferred option should identify:

The process duty being addressed
The operating conditions used for assessment
The limiting factor identified
The proposed equipment or maintenance response
Required shutdown or access
Relevant mechanical considerations
Expected operating conditions after the work
Measurements required for post-work verification

This creates a traceable connection between plant data, thermal calculations and the eventual engineering work.

Where cooling equipment forms part of a larger packaged process, the physical arrangement may also become part of the solution. Extran’s Heating & Cooling Process Skids capability covers the design and fabrication of process skid packages incorporating heat transfer equipment, piping and structural components.

At this stage, the Extran engineering capability can be considered alongside the actual process data, equipment history and site requirements rather than treating modelling as a replacement for engineering review.

Remeasure After the Change

The modelling process should not necessarily end when equipment is cleaned, modified or replaced.

Post-work measurements provide an opportunity to compare actual performance with the conditions used during the engineering assessment. Where practical, using consistent measurement points and operating conditions can make the comparison more meaningful.

Useful measurements may include:

Process inlet temperature
Process outlet temperature
Cooling-medium temperature
Flow rate
Pressure drop
Ambient conditions
Pump or fan operating conditions

This comparison can help determine whether the selected intervention addressed the original constraint and may provide a new operating baseline for future performance reviews.

Results will depend on the quality and representativeness of the measurements, the fluid properties used, equipment condition and the assumptions applied during the engineering assessment. Modelling results should therefore be reviewed in the context of the actual plant by appropriately qualified engineers.

Example: A Cooler After a Production Change

Consider a plant where production increases and the process fluid becomes more concentrated. The cooler continues to operate acceptably during some periods but approaches its required outlet temperature during higher-demand conditions.

A single design-point calculation may not explain the change.

A scenario-based model can compare the original operating condition with the higher production case. It can then assess the effect of flow, fluid properties, ambient temperature and other relevant variables.

The outcome may show that the cooler has sufficient heat transfer area but is constrained by another operating factor. Alternatively, the analysis may indicate that the revised duty exceeds the available thermal capacity under the required operating conditions.

The appropriate response should follow from that finding rather than being assumed beforehand.

If servicing restores the required performance, replacement may not be necessary. If the model indicates a fundamental capacity limitation, equipment modification or replacement can then be assessed against the revised process requirement.

Information to Provide for a Thermal Modelling Assessment

A thermal modelling review is more useful when the available information reflects actual plant conditions.

Where available, operators should provide:

Existing equipment drawings and datasheets
Process flow rates
Inlet and outlet temperatures
Operating and design pressures
Fluid composition or relevant properties
Cooling-medium conditions
Pressure-drop information
Ambient operating conditions
Fouling and maintenance history
Previous inspection findings
Current production requirements
Any proposed future process changes

This information helps establish the operating envelope and identify which scenarios should be included in the assessment.

The final modelling approach should be appropriate to the equipment, process and available data. Where information is incomplete or uncertain, the limitations should be recognised rather than presenting the model output as an exact representation of plant performance.

Frequently Asked Questions

What data is needed for process thermal modelling?

Useful information can include flow rates, inlet and outlet temperatures, fluid properties, pressure conditions, fouling history, equipment drawings and current operating trends. Representative measurements provide a stronger basis for the assessment.

Can thermal modelling determine whether a cooler needs replacement?

Thermal modelling can support the decision, but it should be considered alongside equipment condition, inspection findings, operating data, pressure drop and maintenance history. The assessment should help determine whether replacement, modification, servicing or another intervention warrants further investigation.

Why do changing process conditions affect cooler performance?

Heat transfer performance depends on factors including flow, temperature difference, fluid properties, available surface area and fouling. When these conditions change, equipment that previously met the required duty may have less operating margin.

What should happen after a cooler is modified or serviced?

Post-work measurements can be compared with the operating conditions used during the assessment. Recording temperatures, flow, pressure drop and relevant ambient or cooling-medium conditions can help verify the outcome and establish a useful new operating baseline.

Conclusion

Thermal modelling is most useful when it connects measured plant behaviour with a practical engineering decision. The process should establish representative duty cases, validate the input data, identify the limiting factor, compare intervention options, develop the preferred engineering scope and measure performance after the work where appropriate.

For changing process conditions, this approach can help maintenance, operations and procurement teams understand whether an existing cooler should be serviced, modified or assessed for replacement.

Extran’s current engineering information confirms that its New Commissions capability includes thermal modelling of existing installations to assess how changing process conditions can affect equipment output.

For a project-specific discussion, call us on +61 3 9761 7766 to discuss your operating data, equipment drawings, inspection history and proposed process changes.

Thermal Modelling for Changing Process Conditions in Industrial Coolers