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 Lavals SelfClean™-konstruktion gør SpiralPro-modelvarmevekslere til et smart valg, når der arbejdes med snavsede væsker, slam, emulsioner, opslæmninger, fibre eller partikelbelastede væsker. Da væskerne strømmer kontinuerligt i en enkelt kanal, modvirker væskekraften eventuelle aflejringer ved at "skubbe" dem gennem kanalen og ud i den anden ende.

SpiralPro-modellens kompakte karakter tillader ofte, at flere store rørvarmevekslere erstattes af en enkelt SpiralPro-veksler. Dette giver, ud over at reducere vedligeholdelses- og rengøringsbehov, også betydelige infrastrukturelle fordele. Hvis enheden skal rengøres, kan dækslerne nemt fjernes, så der kan vaskes med en hydrojet.

Anvendelsesformål

• Fouling-væsker indeholdende faste stoffer, fibre, lud, opslæmninger og slam
• Forvarmning, opvarmning, køling, udskiftning og varmegenvinding af væske-til-væske

SpiralPro-modelvarmevekslere optimeret til opgaver med dampopvarmning af væsker, hvor der forekommer stærk fouling, er også tilgængelige. Ligesom alle SpiralPro-enheder er disse fuldt tilgængelige til hurtig og nem rengøring med hydrojets.
Modstrøms-flowet sikrer også en meget tæt temperatur-approach for maksimal termisk effektivitet.

Anvendelsesformål

• Fouling-væsker indeholdende faste stoffer eller fibre, lud, opslæmninger og slam og andre udfordrende væsker, der kræver opvarmning med damp

SpiralCond-modelvarmevekslere tilbyder en yderst effektiv løsning til udfordrende to-faseopgaver, herunder både kondensering og fordampning (reboiling). SpiralConds kompakte design og det faktum, at det er konfigureret lodret, resulterer i et meget lille fodaftryk sammenlignet med tilsvarende rørvekslere, samtidig med at det reducerer understøttende strukturer og rørkompleksitet.

SpiralCond-enheder har kryds-flow i stedet for modstrøms-flow. Hver enhed er fuldt tilpasset til den krævede opgave, med kanalafstand indstillet til at give det laveste trykfald. SpiralCond er derfor ideel til vakuumkondenserende applikationer.

Anvendelsesformål

• Gasser: ren damp og blandinger med ædelgasser
• Damp/væske: topkondensatorer, refluxkondensatorer, vakuumkondensatorer, aftrækskondensatorer, reboilers med fouling-væsker, gaskølere 

Alfa Laval kan levere SpiralCond-modelvarmevekslere integreret i en søjle til kondenserings- og fordampningsapplikationer, hvor flere kølemedier er involveret. Ligesom den enkeltstående selvstændige SpiralCond har denne konfiguration kryds-flow og åbne kanaler for ekstremt lavt trykfald i vakuumsituationer.

Den høje effektivitet af SpiralCond gør det muligt for søjlen at være både lavere i højde og mindre i diameter end traditionelle søjleløsninger, hvilket giver store besparelser i infrastruktur- og installationsomkostninger.

Anvendelsesformål

• Damp-væske: topkondensatorer, refluxkondensatorer, vakuumkondensatorer og aftrækskondensatorer

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.