Plate Heat Exchangers

How Plate Heat Exchangers Work

A plate heat exchanger consists of a stack of thin, corrugated metal plates clamped together in a frame. Hot and cold fluids flow through alternate channels between the plates, exchanging heat through the thin metal wall.

The corrugated plate pattern creates turbulent flow at relatively low velocities, which dramatically increases heat transfer coefficients compared to shell-and-tube designs. A PHE can achieve the same heat duty in 20 to 30% of the volume of a shell-and-tube exchanger.

Advantages

• Compact: High heat transfer area per unit volume. Typically 3 to 5 times more compact than equivalent shell-and-tube.
• High efficiency: Turbulent flow on both sides gives heat transfer coefficients 3 to 5 times higher than shell-and-tube.
• Flexible: Plates can be added or removed to change capacity. Easy to modify for changed duty.
• Low fouling: Turbulent flow and smooth plate surfaces resist fouling. Self-cleaning effect.
• Easy maintenance: Open the frame, clean plates in place or remove for cleaning. No tube bundle to pull.
• Close approach temperatures: Can achieve approach temperatures as low as 1 to 2 degrees C. Shell-and-tube typically 5 to 10 degrees C.

Disadvantages

• Gasket limitations: Gaskets (EPDM, NBR, Viton) limit temperature and pressure. Typical max: 150 to 180 degrees C, 25 bar.
• Gasket replacement: Gaskets degrade over time and must be replaced periodically. Can be labour-intensive for large units.
• Not for high viscosity: Very viscous fluids do not flow well through the narrow plate channels. Pressure drop becomes excessive.
• Not for fibrous or large solids: Plate channels are narrow (2 to 5mm). Fibrous or large-particle fluids will block them.
• Leakage risk: A failed gasket can cause cross-contamination between fluids. Not ideal for hazardous or high-purity applications.

Gasket Selection