Technical information - Welded spiral heat exchangers

How do spiral heat exchangers work

Alfa Laval spiral heat exchangers are circular units containing two concentric spiral flow channels, one for each fluid. The different media flow counter currently: one fluid enters the centre of the unit and flows towards the periphery, the other enters the unit at the periphery and moves towards the centre. The channels are curved and have a uniform cross section. There is no risk of intermixing.

The product channel is normally open on one side and closed on the other. The channel for the heating/cooling medium can sometimes be closed on both sides, depending on the cleanliness of the heating/cooling medium. Each channel has one connection in the centre and one on the periphery of the heat exchanger.

The single-channel geometry also creates a scrubbing effect that we refer to as the SelfClean™ design. If fouling does occur in the heat transfer channel, the cross-section of this part of the channel is decreased. However, since the entire flow must still pass through the channel, the velocity increases, the resulting fluid force then flushing away any accumulations of deposits as they form.

Compare this design with shell-and-tube heat exchangers where the flow enters different tubes in parallel. When tubes start to foul, pressure drop increases pushing the fluid to find alternative flow paths. The result is that fouling and clogging of the tubes happens very quickly. With Alfa Laval spirals, on the other hand, fouling and clogging is virtually eliminated.

Our welded spiral product range

Alfa Laval’s SelfClean™ construction makes SpiralPro model heat exchangers a smart choice when working with dirty fluids, sludges, emulsions, slurries, fibres or particle loaded liquids. Since the fluids flow continuously in one single channel, the fluid force acts against any deposits, “pushing” them through the channel and out the other end.

The compact nature of the SpiralPro model often allows several large shell-and-tubes heat exchangers to be replaced by one single SpiralPro exchanger. This creates considerable infrastructure benefits in addition to reducing maintenance and cleaning requirements. If the unit needs cleaning, the covers can easily be removed for washing with a hydro jet.

Applications

• Fouling liquids containing solids, fibres, liquors, slurries and sludges
• Liquid-to-liquid preheating, heating, cooling, interchanging and heat recovery

Download product leaflet           Watch product animation

SpiralPro model heat exchangers optimized for duties involving steam heating of liquids that are highly fouling are also available. Like all SpiralPro units, these are fully accessible for quick and easy cleaning with hydro jets.
The counter-current flow also ensures a very close temperature approach for maximum thermal efficiency.

Applications

• Fouling liquids containing solids or fibres, liquors, slurries and sludges and other challenging fluids that require heating by steam

Watch product animation

SpiralCond model heat exchangers offer a highly efficient solution for challenging two-phase duties, including both condensing and evaporation (reboiling). SpiralCond’s compact design and the fact that it is configured vertically results in a very small footprint, compared to equivalent shell-and-tube exchangers, while also reducing supporting structures, and piping complexity.

SpiralCond units have cross-flow rather than counter-current flow. Each unit is fully customized according to the duty required, with channel spacing adjusted to provide the lowest pressure drop. SpiralCond is therefore ideally suited to vacuum condensing applications.

Applications

• Gases: pure vapour and mixtures with inert gases
• Vapour/liquid: top condensers, reflux condensers, vacuum condensers, vent condensers, reboilers with fouling fluids, gas coolers 

Download product leaflet           Watch product animation

For condensing and evaporation applications where multiple cooling media are involved, Alfa Laval can deliver SpiralCond model heat exchangers integrated in a column. Like the single stand-alone SpiralCond, this configuration has cross-flow and open channels for extremely low pressure drop in vacuum situations.

The high efficiency of SpiralCond allows the column to be both shorter in height and smaller in diameter than traditional column solutions, thus offering major savings in infrastructure and installation costs.

Applications

• Vapour-liquid: top condensers, reflux condensers, vacuum condensers and vent condensers

Unique features of Alfa Laval Welded spiral heat exchangers

Superior cleaning and extended performance

The SelfClean design of Alfa Laval spirals provides a reliable solution for fouling and clogging in duties involving challenging fluids, sludges, emulsions, slurries, fibres or particle loaded liquids.

Each circuit on a spiral unit consists of a single flow channel. This continuously curving, single-channel geometry creates high turbulence to minimize fouling from the start. If fouling does start to occur, local velocity increases, since the entire flow must still pass through the channel. This creates a scrubbing effect that flushes away any accumulations of deposits as they form.

An additional benefit of this design is that it eliminates the risk of dead spots and stagnation for more efficient heat transfer.

Automated, reliable channel enclosure

The manufacturing of Alfa Laval’s spiral heat exchangers incorporates an automated process for bending the edge of the channels. This is followed by a cold-metal-transfer automatic welding machine for the final closure weld.

The combined effect of this so-called RollWeld technique is consistent quality of the channel closure. That, in turn, is critical for the strength and corrosion resistance of the channel welds and thus the reliability of the overall unit.

A custom solution for high-pressure duties

For customers whose processes demand higher design and differential pressures than traditional spiral heat exchangers can provide, Alfa Laval offers capabilities to fully tailor a unique solution to match their needs.

We design our HighP spiral heat exchangers using a range of features, including a double gasket system, a self-supporting internal coil, and a special body and shell with bolted cover. Our experienced engineers work with you throughout the design process to make sure you get the ideal heat exchanger for your specific challenges.