When to Use a Plate Heat Exchanger Instead of a Shell and Tube Heat Exchanger

Choosing between a plate heat exchanger and a shell and tube heat exchanger is not a straightforward preference between two interchangeable options. Each type has a defined application range where it performs best, and selecting outside that range creates problems that become apparent in service. Specifying a plate heat exchanger for a duty it cannot handle reliably leads to premature failure or performance shortfall. Specifying a shell and tube unit for a duty better suited to plate construction may result in unnecessary capital cost and a larger installation footprint than the application requires.

Heat exchanger type selection should follow from the process conditions, not from familiarity with one equipment type. Understanding when each type is the right choice, and when neither is appropriate without modification or alternative design, is central to making a sound engineering decision. This article covers the conditions that favour plate heat exchanger uses, the conditions that favour shell and tube construction, and the practical considerations that affect the selection for Australian industrial applications.

What Makes Plate Heat Exchangers Suited to Certain Applications

High Heat Transfer Efficiency in a Small Footprint

Plate heat exchangers achieve a high rate of heat transfer per unit of surface area relative to shell and tube construction. The corrugated plate pattern creates turbulence in the fluid passing through the narrow channels between plates, which keeps the thermal boundary layer thin and maintains a high heat transfer coefficient. The result is a unit that achieves a given heat duty in a significantly smaller physical footprint than an equivalent shell and tube exchanger.

This compactness is an advantage in facilities where floor space is constrained, where the equipment must fit within an existing building or module, or where the installed weight of the heat exchanger affects the structural design of the supporting platform. In offshore installations, modular plant, and urban industrial facilities with limited available space, the size advantage of plate heat exchangers can be a deciding factor in the heat exchanger type selection.

For the same heat duty, a plate heat exchanger uses less total surface area than a shell and tube unit because the higher heat transfer coefficient produces more heat transfer per square metre of surface. This means less material, a smaller frame, and reduced weight for the same duty. Within the operating range of plate construction, this is a clear advantage.

Cleanability and Plate Access in Gasketed Designs

Plate heat exchangers in gasketed configuration can be fully disassembled by releasing the tie bolts and separating the plate stack. Each plate is individually accessible for visual inspection, mechanical cleaning, or replacement. This makes gasketed plate construction the appropriate choice for duties where the process fluid deposits fouling on the heat transfer surfaces and the fouling must be removed by mechanical methods.

In food, beverage, and pharmaceutical processing, where hygiene is a regulatory requirement and the heat transfer surfaces must be cleanable to a defined standard, gasketed plate heat exchangers are the standard choice for liquid heating and cooling duties within their operating range. The ability to inspect every plate surface after cleaning and before reassembly provides a level of assurance that is not achievable with the inaccessible tube-side surfaces of a shell and tube exchanger.

Plate heat exchanger uses in these industries are driven by the combination of high thermal efficiency, compact size, and the practical necessity of full surface access for cleaning and inspection. For duties where these factors align with the process conditions, the plate design is the more practical choice.

Where Shell and Tube Heat Exchangers Remain the Better Choice

High Pressure and High Temperature Services

Shell and tube heat exchangers handle a much wider range of operating pressure and temperature than plate construction. Pressure vessel design codes allow shell and tube units to be designed for virtually any combination of pressure, temperature, and material consistent with the available tube and shell materials. Plate heat exchangers, including brazed types, are limited to pressure and temperature ranges defined by the plate material thickness, the gasket or brazing material, and the plate geometry.

Plate heat exchanger uses are not feasible for high-pressure gas cooling, steam service at elevated pressures, cryogenic applications, or any duty that exceeds the pressure or temperature rating of the plate and gasket materials available for the specific fluid service. In these applications, shell and tube heat exchangers are the only practical equipment type capable of achieving the required design conditions within a standard engineering framework. A shell tube heat exchanger designed to the appropriate pressure vessel standard can handle the full range of industrial pressures and temperatures without the operating limit constraints that apply to plate construction.

Oil and gas processing, power generation, and petrochemical applications regularly involve combinations of pressure, temperature, and fluid type that place them firmly outside the application range of plate construction. Shell and tube design is the default starting point for these duties, and the heat exchanger design for these applications is governed by API 661, AS 1210, or ASME VIII as appropriate.

Multiphase and Particulate-Laden Fluid Services

The narrow flow channels in a plate heat exchanger are not suited to fluids containing large solids, fibres, or other particulate matter that would block or damage the channel. Fluids that are highly viscous may not distribute evenly across the plate stack, leading to uneven flow and localised fouling. Multiphase streams involving partial vaporisation or condensation require design features, including adequate vapour disengagement space, that are not available in standard plate heat exchanger construction.

Shell and tube heat exchangers handle these duties through appropriate shell geometry, baffle design, and tube bundle configuration. A shell with adequate cross-sectional area for vapour flow, combined with appropriate tube pitch to prevent bridging of solids between tubes, can accommodate duties that would be impractical in a plate design. These considerations are part of the heat exchanger design process for each specific application.

Process Conditions That Drive Heat Exchanger Type Selection

Temperature Approach and Close Thermal Duty

Plate heat exchangers can achieve very close temperature approaches between the two fluid streams because the counter-current flow arrangement and high heat transfer coefficient allow efficient heat exchange even when the temperature difference between the two streams is small. This makes plate construction appropriate for heat recovery duties where maximising the amount of heat recovered from one stream to another requires a close temperature approach.

Shell and tube exchangers achieve close approaches through multi-pass tube arrangements, which allow the tube-side fluid to traverse the shell length multiple times, improving the effective mean temperature difference. The design is more complex and the unit larger than a plate exchanger achieving the same approach, but there is no fundamental limitation on the achievable approach for a shell and tube design within the constraints of the operating pressures and temperatures.

Heat exchanger service capabilities at our AS 9001 accredited workshop cover both plate and shell and tube equipment, supporting the maintenance and performance restoration of both types throughout their service life.

Fouling Potential and Cleanability

The narrow plate channel in a plate heat exchanger creates a higher fluid velocity for a given flow rate than the equivalent shell and tube arrangement, which reduces the rate of deposit accumulation on the plate surface. However, when fouling does occur in the narrow channel, the restricted passage amplifies the effect on flow distribution and pressure drop compared to the relatively larger passages in a shell and tube unit.

High-fouling fluids, including those carrying suspended solids, biological contamination, or fluids that precipitate deposits at operating temperatures, are better suited to shell and tube construction where the tube-side diameter provides more tolerance for partial fouling before flow is significantly restricted. This is one of the key factors in heat exchanger type selection for duties involving fluids with significant fouling potential.

Physical Footprint, Fouling, and Operability

Space and Weight Constraints

For duties within the operating range of plate construction, the size and weight advantage over shell and tube equipment is significant. A plate heat exchanger achieving a given thermal duty may occupy a fraction of the floor space of a shell and tube unit rated for the same duty. This advantage is most relevant on offshore platforms, in modular processing plants, and in existing facilities where installing additional equipment within the available space is constrained.

Where the heat duty is large, the pressure or temperature is beyond the plate range, or the fluid is not compatible with plate construction, shell and tube equipment is the appropriate solution regardless of the size comparison. Equipment selection must be driven by technical suitability first, and size and cost are secondary considerations that are only meaningful after the technically feasible options have been identified.

Operability at Variable Load

Gasketed plate heat exchangers can be adapted to changes in duty by adding or removing plates within the limits of the frame design. If the process load increases after commissioning, plates can be added to increase surface area and restore the target outlet temperature. If the duty decreases, plates can be removed. This adaptability is an operational advantage not available with shell and tube construction, where the tube count and bundle size are fixed at manufacture.

Our Victorian engineering team works through the process duty, operating range, and site constraints with clients before making a recommendation on heat exchanger type selection. Both plate and shell and tube options are assessed against the specific application requirements before a direction is recommended.

Hybrid Applications Using Both Equipment Types

Using Plate and Shell and Tube Equipment in the Same Circuit

Many Australian industrial plants use both plate and shell and tube heat exchangers in the same process circuit, with each type assigned to the duty it is best suited to. A common arrangement uses shell and tube equipment for high-temperature or high-pressure initial cooling, followed by plate heat exchangers for final cooling to the target outlet temperature where the pressure and temperature are within the plate operating range.

This arrangement takes advantage of the compact size and high thermal efficiency of plate construction for the lower-temperature stage while maintaining the mechanical robustness of shell and tube design for the more demanding conditions at the inlet of the cooling circuit. Oil and air coolers in hydraulic and lube oil systems provide a third category of heat transfer equipment that may be installed alongside plate and shell and tube equipment in the same facility, each serving a different fluid circuit.

Process Skid Integration of Mixed Equipment Types

Where a process circuit includes multiple heat transfer duties, heating and cooling process skids can incorporate different heat exchanger types within a single engineered package. The skid design accounts for the process conditions at each stage and selects the appropriate heat exchanger type for each duty within the package.

Pre-fabricated process skids incorporating plate and shell and tube equipment are used in oil and gas, mining, and general industrial applications in Australia. Shop fabrication and testing of the complete package before delivery reduces site installation scope and allows functional verification of the full thermal circuit before it is connected to the surrounding process.

How Industrial Operators Make the Final Selection

Starting with Process Conditions and Working to Equipment Selection

The selection process begins with the process data: inlet and outlet temperatures for both streams, flow rates, operating pressure, fluid composition and properties, fouling tendency, and the space and weight constraints at the installation site. Heat exchanger applications that fall within the operating range of plate construction can be assessed against both plate and shell and tube options on the basis of cost, size, and maintenance requirements.

Where the process conditions place the duty outside the range of plate construction, the selection defaults to shell and tube without requiring a detailed comparison. Where both options are technically feasible, the decision is made on the basis of the factors that matter most for the specific application: compactness, maintenance access, adaptability, or capital cost.

For industrial heat transfer applications in Australia, the duty profile over the life of the equipment should also influence the selection. A duty that is expected to change significantly after commissioning favours the adaptability of a gasketed plate unit. A permanent, stable duty where the process conditions are well-defined may favour the simplicity and robustness of a shell and tube design.

Conclusion

Plate heat exchangers offer compactness, high thermal efficiency, and maintenance accessibility for duties within their operating range. Shell and tube heat exchangers handle the full range of industrial pressures, temperatures, and fluid types, making them the default choice for demanding applications that exceed the limits of plate construction.

Many Australian industrial operations use both types, with heat exchanger applications assigned to the equipment best suited to each duty in the plant. The starting point for any heat exchanger type selection decision is the process conditions, not the equipment type.

Call +61 3 9761 7766 or contact us to discuss the heat exchanger type suited to your specific application.