What is Spiral Heat Exchanger?
A Spiral Heat Exchanger is a specialized type of heat exchanger designed around two long, flat plates that are coiled around a central core to form two concentric, spiral flow channels for the two fluids. One fluid flows through the inner channel, and the other fluid flows through the outer channel in a counter-current flow pattern.
Core Principle: The two fluids flow through long, uninterrupted spiral passages. Heat is transferred through the metal plate separating the channels. The long flow path and centrifugal force create turbulence at low flow rates, leading to high heat transfer efficiency and reduced fouling.
Key Components and Their Functions
The design is distinct from other heat exchangers, with several unique parts:
- Spiral Plates: The two long metal plates that are coiled to form the channels. They are the primary heat transfer surface.
- Central Core: The starting point around which the plates are wound. It forms the inlet for one of the channels and provides structural support.
- Spacer Pins: These are welded to the plates at regular intervals before coiling. They are critical as they:
- Maintain the precise gap between the plates, defining the channel width.
- Provide mechanical support and prevent channel deformation under pressure.
- Covers / End Plates: Flat plates that are bolted to the sides of the spiral assembly to contain the fluids and create a sealed unit. They can be fully welded or have gasketed designs for easier cleaning.
- Nozzles: Inlet and outlet ports for the two fluids. They are located at the center and the periphery of the unit.
Common Applications
Spiral heat exchangers are niche specialists, chosen for difficult fluids that would quickly foul other exchanger types:
- Wastewater Treatment: Heating and cooling of sludge and effluent.
- Pulp & Paper Industry: Handling black liquor, white liquor, and other fibrous, fouling streams.
- Chemical Processing: Heating and cooling of polymers, resins, solvents, and slurries.
- Food & Beverage: Handling viscous fluids like syrups, gelatin, and pastes.
- HVAC: As geothermal heat exchangers or for recovering heat from foul condensate.