Pillow Plate Heat Exchangers: Technology, Design, Performance Limits
Pillow plate heat exchangers (pillow plates) are pressure elements constructed from two welded sheets. The defining feature is the internal spot weld pattern – it determines flow cross-sections, pressure resistance, and heat transfer behavior. We have been defining this pattern using our own calculation models since 1958, continuously refining them based on process data and project feedback.
The Spot Pattern – Core Design Parameter
The weld spot pattern is not a constructive detail; it is the critical design parameter. It simultaneously governs:
- Pressure resistance (burst pressure PB, calculated per AD 2000 S5 / ASME Code)
- Flow distribution and dead zone minimization
- Heat transfer coefficients on the inner surface of the plate
- Mechanical stability through work hardening during the inflation process
Our engineers define the spot pattern and inflation height as the integrated result of all relevant process parameters – not sequentially, but as a holistic optimum.
Fluid-Dynamic Advantage over Shell-and-Tube Exchangers
The three-dimensional pillow geometry induces turbulent flow even at low Reynolds numbers. This generates comparatively high internal heat transfer coefficients – earlier and at lower pressure drops than in tube systems.
The design implication:
- Same thermal output with less heat transfer area
- Lower steel requirement compared to shell-and-tube designs
- Lower pressure drop at equivalent thermal performance
We think in systems: from thermodynamic simulation through flow optimization to material-appropriate design.
Pressure Resistance – Verified by Burst Pressure Testing
The pressure resistance of every pillow plate is verified through burst pressure tests on representative samples – in the presence of a certified inspector from the relevant testing authority. Maximum allowable pressures are calculated per AD 2000 Code S5 or the ASME Code.
Burst pressures >450 bar are achievable. Maximum allowable operating pressures PS >70 bar and operating temperatures TS >400 °C are covered by our design methodology.
Fluid Groups — Breadth of Application
Our design expertise covers all relevant fluid groups:
| Fluid Group | Examples |
| Single-phase liquids | Water, thermal oils, high-viscosity coolants |
| Superheated gases | Process gases, air |
| Evaporating media | Natural refrigerants, HFCs |
| Condensing media | Steam, process vapors |
Validated through decades of project experience in chemicals, pharmaceuticals, energy technology, and food processing.