HRS Unicus Series: Scraped Surface Heat Exchanger (SSHE).

The Unicus is a scraped surface heat exchanger for high fouling and viscous fluid applications. It has specially designed and developed to offer a solution for those difficult heat transfer applications where very viscous fluids are used or fouling appears. The design is based on a traditional shell and tube heat exchanger with scraping elements inside each interior tube. The scrapers are moved back and forth by hydraulic action. The scraping action has two very important advantages:

• The reciprocating movement of the scrapers cleans the heat exchange surface. This keeps heat transfer high and reduces downtime as cleaning in place can be avoided.
• Besides, the scraping movement introduces turbulence in the fluid increasing heat transfer.

This design makes the Unicus the ideal heat exchanger for any applications where fouling or low heat transfer is a limiting factor. The Unicus can be applied in industrial and hygienic applications.

The gentle movement of the scrapers allows working with delicate products (such as food products with whole fruit or vegetable pieces) without destroying the integrity of the product.

Continuous improvements have allowed HRS Heat Exchangers to apply the Unicus for a wide range of markets and applications. By increasing the stroke speed of the scraper bar we have been able to increase the heat transfer rates considerably. By adding new scraper types we have adapted to the difficulties that new products may present. The increased range of models available has made it possible to offer economic solutions for small to big duty applications. From food industry to environmental industry, from biomass to evaporation applications, the Unicus is a robust solution where other types of heat exchangers fail to deliver a good result.

In the following animation you can see the virtual assembly of a Unicus Scraped Surface Heat Exchanger and its operation.

Characteristics of the Unicus

The Unicus is a heat exchanger that consists of three main parts:

• The shell and tube part: Inside each interior tube a scraper bar is fitted.
• The separation chamber: This space separates the shell and tube heat exchanger from the drive cylinder that moves the scraper bars.
• The cylinder: This part provides the energy that moves the scraper bars. The cylinder can be pneumatic (smaller models) or hydraulic (bigger models).

A key component of the Unicus is the seal that separates the inner tube volume from the separation chamber. The seal prevents leakage of the product to the exterior. Several types of seals have been developed depending on the application.

Better heat transfer through scraping

The scraping system consists of a stainless steel rod to which the scraping elements are fitted. Various types of scrapers have been developed for the different applications the Unicus can handle. Materials such as Teflon and Peek (polyaryletheretherketone) are used. 120º scrapers allow for working with big particulates. The 360º scrapers are ideal for viscous fluid without particulates. As the product changes we adapt the geometry of the scraper. Scraping means fouling free heat transfer surfaces. No loss of heat transfer due to fouling.

Another advantage of the scraping action is the introduction of extra turbulence in the product. This results in a better transport of the product to and from the heat exchange surface which enhances heat transfer rates significantly.

In the following animation you can see a simulation of a viscous fluid with particulates passing through the scraped tubes of a Unicus.

Unicus, a scalable solution

Like with any ordinary shell and tube heat exchanger scale up to bigger duties is as simple as increasing the shell diameter and fitting more interior tubes in the shell. Unicus models are available as tube in tube version (1 interior tube only) up to models with 80 tubes inside. This allows us to supply Unicus models in the range of 0,7 to 100 m2 of heat transfer area. A standard range of models up to 10 m2 is available for hygienic food applications and other industrial applications. The bigger range of models is tailored to the application it is intended for.

Products.

• Dairy: Cheese, yogurt, creams, deserts, whey concentrate, ice cream, condensed milk.
• Fruits: Juice concentrate, fruit preparation, fruit puree, diced fruit.
• Vegetables: Fried vegetables, tomato concentrate.
• Convenience food: Eggs, mashed potatoes, ketchup, mayonaise, baby food, dressings, spreads, fats, oils.
• Protein: Visceras, meat slurry, MDM, meat stuffing, minced meat, pet food.
• Confectionary: Chocolate, pie filling, creams, pastes, marmalade, syrups, gelatine, starch, butter,maragarine.
• Beverage: Coffee extract, juice freezing, juice concentrate, yeast-malt extracts.
• Cosmetics: Lotion, cream, gel.
• Environmental waste: Waste concentration: brine, manure, food plant effluent, chemical waste, solvent recovery.
• Biofuels: Oil extraction for biodiesel, biomass pretreatment, thermal hydrolysis, fermentationdigestate concentration.

Processes.

• Heating.
• Cooling.
• Pasteurization.
• Crystalization.
• Evaporation.*

Evaporation.*

HRS Heat Exchangers designs a special version of the Unicus for evaporation applications. The principle is the same: a shell and tube heatexchanger with scraping rods in the interior tubes. During evaporation, fouling and reduced heat transfer can become a problem for traditional evaporators (falling film type etc.). In case of the Unicus, the scraping action keeps the heat transfer surface clean and maintains heat transfer high. This allows the Unicus to concentrate to levels where traditonial technolgies fail. This makes the Unicus the ideal solution for concentration of environmental waste where volume reduction is vital. The Unicus evaporators can be applied in a multi-effect setup or in combination with mechanical vapor recompression. Also vacuum concentration is not a problem for the Unicus evaporator. The scraped surface operation allows continuous operation and reduces downtime of the plant.

Materials

• Shell side: AISI 304 stainless steel.
• Tube side: AISI 316L stainless steel.

Connections.

• Shell side: DIN flange.
• Tube side: Clamp / Flange

Finishing.

• External finish: Polished.
• Product side: Roughness < 0,8 micron (food grade finish).

Design conditions.

• Shell side: 10 barg / 185 ºC.
• Tube side: 16 barg / 185 ºC.

^† The surface area and volumes shown are for 6,0 meter length models.

^‡ The power consumption is for a stroke rate of the scraper bar around 10-14 cycles/minute.

Unicus evaporator models can be supplied with areas up to 120 m2. Contact HRS Heat Exchangers for further details.

These models can be supplied with a pneumatic cylinder in stead of a hydraulic cylinder. The requiered air pressure is a minimum of 8 bar. Ask HRS Heat Exchangers for further details.