In the name of GodIn the name of God

عنوان پروژه عنوان پروژه

Spiral Heat ExchangersSpiral Heat Exchangersاستفاده از اين مطلب با ذكر منبع مجاز مي باشد استفاده از اين مطلب با ذكر منبع مجاز مي باشد

دانشگاه صنعتي شريف دانشگاه صنعتي شريف آزمايشگاه انتقال حرارت دانشكده مهندسي شيمي و نفت آزمايشگاه انتقال حرارت دانشكده مهندسي شيمي و نفت

This presentation contains a brief This presentation contains a brief introductory description to the spiral introductory description to the spiral heat exchanger, followed by information heat exchanger, followed by information on construction, construction materials, on construction, construction materials, operating limitsoperating limitsand principal applications.and principal applications.

Where appropriate, a comparison is made Where appropriate, a comparison is made with conventionalwith conventionalshell and tube heat exchangers to shell and tube heat exchangers to emphasize size and weight reductions that emphasize size and weight reductions that can becan beachieved by using compact heat achieved by using compact heat exchangers.exchangers.

ContentsContents

IntroductionIntroductionConstructionConstructionOperating LimitsOperating LimitsPrincipal ApplicationsPrincipal ApplicationsComparison with Shell and Tube Heat Comparison with Shell and Tube Heat ExchangerExchanger

IntroductionIntroduction

The classic design of a spiral heat exchanger isThe classic design of a spiral heat exchanger issimple;simple;the basic spiral element is constructed of two the basic spiral element is constructed of two metal strips rolled around a central core forming metal strips rolled around a central core forming two concentric spiral channels.two concentric spiral channels.These channels are alternately welded, These channels are alternately welded,

ensuring that the hot and cold fluids cannot ensuring that the hot and cold fluids cannot intermix.intermix.

The heat exchanger can be optimized for The heat exchanger can be optimized for the process concerned by using different the process concerned by using different channel widths. channel widths. Channel width is normally in the range 5 to Channel width is normally in the range 5 to 30 millimeters.30 millimeters.

Spiral Heat Exchanger With EndSpiral Heat Exchanger With End--Cap Removed (Giving Access to Cap Removed (Giving Access to One SpiralOne SpiralChannel)Channel)

) (Courtesy of GEA Process Technology)

Spiral heat exchangers tend to be selfSpiral heat exchangers tend to be self--cleaning.cleaning.The smooth and curved channels result in aThe smooth and curved channels result in alower fouling tendency with difficult fluids. lower fouling tendency with difficult fluids. This selfThis self--cleaning effect results in reducedcleaning effect results in reducedoperating costs particularly when the unit is operating costs particularly when the unit is horizontally mounted.horizontally mounted.

ConstructionConstruction

In some cases double spacing may be In some cases double spacing may be used.used.

These double channel systems are used These double channel systems are used when there is awhen there is alarge flow rate or small pressure drop, but large flow rate or small pressure drop, but should not be used for fouling media or should not be used for fouling media or mediamediacontaining solids.containing solids.

Spiral Heat Exchanger ManufactureSpiral Heat Exchanger Manufacture

Typically spiral heat exchangers are Typically spiral heat exchangers are available in three configurations:available in three configurations:

Type 1 Type 1 –– Media in full counterMedia in full counter--current flow.current flow.Type 2 Type 2 –– One medium in cross flow whilst One medium in cross flow whilst the other is in spiral flow.the other is in spiral flow.Type 3 Type 3 –– Combination design.Combination design.

Type 1 Type 1 –– Media in full counterMedia in full counter--current flow.current flow.

The hot fluid enters at the centre of the The hot fluid enters at the centre of the unit and flows from the inside outward. unit and flows from the inside outward. The coldThe coldfluid enters at the periphery and flows fluid enters at the periphery and flows towards the centre.towards the centre.

Type 1 Type 1 -- Spiral FlowSpiral Flow--Spiral Flow Heat Spiral Flow Heat ExchangerExchanger

Type 2 Type 2 –– One medium in cross flow whilst One medium in cross flow whilst the other is in spiral flow.the other is in spiral flow.

The medium in cross flow passes through the The medium in cross flow passes through the open channels of the spiral usually in aopen channels of the spiral usually in avertical direction. The service fluid spiral flows vertical direction. The service fluid spiral flows through the other channel, welded shut,through the other channel, welded shut,with side wall inlet and central outlet fed through with side wall inlet and central outlet fed through the side wall as shown in Figure the side wall as shown in Figure This design can be used as either a condenser This design can be used as either a condenser or vaporizer.or vaporizer.

Type 2 Type 2 -- Cross FlowCross Flow--Spiral Flow Heat ExchangerSpiral Flow Heat Exchanger

·· Type 3 Type 3 –– Combination design.Combination design.

A gas or vapor mixture to liquid exchanger A gas or vapor mixture to liquid exchanger combines the above two designs.combines the above two designs.the hot stream enters at the top and flows the hot stream enters at the top and flows tangentially through the exchanger exiting tangentially through the exchanger exiting at the side.at the side.

Type 3 Type 3 -- Combination CrossCombination Cross--Flow and Spiral FlowFlow and Spiral Flow--Spiral FlowSpiral Flow

Operating LimitsOperating Limits

The maximum design temperature is 400C The maximum design temperature is 400C set by the limits of the gasket material.set by the limits of the gasket material.Special designs without gaskets can operate Special designs without gaskets can operate with temperatures up to 850oC. with temperatures up to 850oC. design pressure is usually 15 bar, with design pressure is usually 15 bar, with pressures up to 30 bar attainable with special pressures up to 30 bar attainable with special designs.designs.

Principal ApplicationsPrincipal Applications

The design is ideal for fluids prone to fouling, or The design is ideal for fluids prone to fouling, or polluted with particles as a result of the relatively polluted with particles as a result of the relatively large channel width. large channel width. Hence, it is ideal for use in the food industry Hence, it is ideal for use in the food industry It has many applications in the chemical It has many applications in the chemical industryindustrySpiral heat exchangers provide temperature Spiral heat exchangers provide temperature control of sewage sludge digesters plus other control of sewage sludge digesters plus other public and industrial waste plants.public and industrial waste plants.

Other applications:Other applications:Spiral heat exchangers have perfect counterSpiral heat exchangers have perfect counter--current current flow paths that permit the best possible overlap of flow paths that permit the best possible overlap of exit temperatures.exit temperatures.

As such, they can As such, they can maximisemaximise the heat recovery on the heat recovery on largelarge--scale cogeneration projects .scale cogeneration projects .

Spiral exchangers can be mounted directly onto the Spiral exchangers can be mounted directly onto the head of distillation columns acting in a condensing head of distillation columns acting in a condensing or reflux role. or reflux role.

Specific advantagesSpecific advantages

Ease of installationEase of installationlow pressure droplow pressure droplarge flow crosslarge flow cross--section.section.There are many condensing applications There are many condensing applications in all process industries particularly for in all process industries particularly for condensing under vacuum.condensing under vacuum.

Comparison with Shell and Tube Heat Comparison with Shell and Tube Heat ExchangerExchanger

Optimum flow conditions on both sides of the Optimum flow conditions on both sides of the exchanger.exchanger.An even velocity distribution, with no deadAn even velocity distribution, with no dead--spots.spots.An even temperature distribution, with no hot or coldAn even temperature distribution, with no hot or cold--spots.spots.More thermally efficient with higher heat transfer More thermally efficient with higher heat transfer coefficients.coefficients.Copes with exit temperature overlap, or crossover.Copes with exit temperature overlap, or crossover.Small hold up times and volumes.Small hold up times and volumes.··Removal of one cover exposes the total surface area of Removal of one cover exposes the total surface area of one channel providing easy inspection cleaning and one channel providing easy inspection cleaning and maintenance.maintenance.

For the same duty, a spiral heat For the same duty, a spiral heat exchanger heat transfer area would be exchanger heat transfer area would be 90m2 compared to90m2 compared to60m2 for a plate and frame design or 60m2 for a plate and frame design or 125m2 for a shell and tube design. 125m2 for a shell and tube design.

Heat Exchanger Size Comparison for Plate, Spiral, and Heat Exchanger Size Comparison for Plate, Spiral, and Shell and Tube HeatShell and Tube Heat

ExchangersExchangers