Effective and Safe Heat Transfer for Viscous and Particulate Fluids by using Scraped Surface Heat Exchangers in Food, Dairy, beverage and allied Industries.
In general, the more viscous the fluid, the lower the heat transfer is. This means that very viscous fluids require a very large heat transfer area. Scraped surface heat exchangers vigorously mix the fluid, which helps to move the fluid to and from the heat exchange surface. This increases heat transfer rates, so the total area required for heat exchange is reduced.
For difficult heat transfer applications, with high viscosities and where fouling can become a problem, the preferred option is a scraped surface heat exchanger. Scraped surface heat exchangers keep heat transfer high and the heat transfer surface is constantly cleaned.
HRS offers two technologies for scraped surface heat transfer: the patented HRS Unicus Series which reciprocates and R Series which rotates, each designed for specific needs.
HRS Unicus Series
Increase in processing of viscous products from food, pharmaceuticals to environmental require advanced technology with good return on investment. Traditional methods used for evaporation, crystallization and high fouling applications are insufficient to meet industry demands for better quality, capacities and cost efficiency.
UNICUS heat exchanger is formed by a tube bundle inside a shell. Scraping elements attached to rods are placed inside each tube of Unicus. The movement of these rods is programmed from the control panel and powered by a hydraulic power unit.All inner tubes include moving bars that support the scraping and mixing elements, This unique design heat exchanger surface clean of fouling and agitate the flow to boost the overall heat transfer coefficient by action.(unlike conventional scraped surface heat exchangers that move in rotation).
Fouling During Heat Transfer
Fouling occurs when particulate or viscous matter sticks and degrades at the tube walls. Another form of fouling is crystallization where, due to cooling or increasing concentration, components in the fluid change to the solid state and deposit on the heat exchanger surface. These layers work as an insulator for heat transfer, causing performance to drop.
UNICUS enables scraping of the heat transfer where fouling layers need removal to maintain high heat transfer in place. Scraped surface heat exchangers mix the fluid vigorously, which helps to move the fluid to and from the heat exchange surface. This increases heat transfer rates, so the total area required for heat exchange is reduced.
The patented UNICUS series is a scraped surface heat exchanger has been specially designed and developed to offer a solution for those difficult heat transfer applications, like evaporation, crystallization of chemical, food, environmental applications where product viscosity is usually high.
The UNICUS Series heat exchanger consists of three main parts:
Material of Construction
UNICUS can be designed and manufactured in various grade of tube and shell material as per process requirements.
Materials: Shell side: AISI 304 stainless steel; Tube side: AISI 316L stainless steel
Connections: Shell side: Flange; Tube side: clamp / flange
External Finish: Satin or Polished: Product side: <0.8 microns
Design conditions: Shell side: 10 bar(g) / 185°C; Tube side: 16 bar(g) / 185°C
Scraping elements are manufactured in different materials like Teflon, polysulphone, peek, etc. in sizes of 1200 and 1800 or 3600. Scraping/mixing blades in PTFE and silicone (both FDA approved). Metallic blades are available for non-hygienic applications.
SCRAPING ELEMENTS & SEALS
Scraping blades are designed to be light, highly chemically resistant and thermally more efficient, thus reducing both weight and energy consumptions with an effective scraping action. They are combined with a silicon spring or peek segments to fit tightly to the tube surface.
The design temperature is 165°C. The design pressure is 16 bar on the product side and 10 bar on the service side. Higher pressure ratings are available subject to a revision of material compatibility, component thickness and connection types.
DIN11851, ISO clamps, aseptic ISO clamps or sterile flanges on the product side and DIN11851, DIN2576 flanges or ISO clamps on the service side. Other couplings can be made available as required. The mounting is usually done on SS 304 skid frame. The units can be installed horizontally or vertically.
Two scraped surface heat exchanger solutions have been developed for different types of applications – UNICUS Reciprocating Scraped Surface Heat Exchanger & UNICUS Rotating Scraped Surface Heat Exchanger.
UNICUS can have series or parallel flow configuration depending on the application. It can work horizontally or vertically because the scraping is alternating. This allows the units to work at all flow rates without any limitation, regardless of the temperatures, program or product nature. Product flow can be in single or multiple pass.
UNICUS: A SCALABLE SOLUTION
UNICUS Series models are available in versions containing just one tube, up to models with 80 tubes inside. This allows UNICUS Series models to have heat transfer areas between 0.7 and 100 m². A standard range of models up to 10 m² is available for hygienic food applications and other industrial applications, while the larger of models are tailored to final use.
UNICUS is suitable for heat transfer applications in a very wide range of industries and has multiple uses, including:
Rotating Scraped Surface Heat Exchangers – HRS R Series
The HRS R Series is a scraped surface heat exchanger designed for the most difficult heat transfer applications, for example where very high viscosities and highly fouling fluids need heat treatment.
Unlike the HRS Unicus Series, where the scraper movement is reciprocal, the HRS R Series technology uses a rotary scraper rod. This scraper rod can reach velocities up to 300 rpm resulting in very high levels of shear and mixing at the heat transfer surface; dramatically increasing the heat transfer rate.
The R and RHD Series has been developed for both hygienic and industrial applications. Each inner tube contains a scraper bar fitted with a helical screw which rotates at high speed and enhances flow through the tube whilst reducing pressure drop. In addition, the continuous scraping action eliminates fouling on the inner tube wall, ensuring that the heat transfer area is clean at all times.
The R and RHD Series are suitable for heat transfer applications on a wide range of products and applications:
Some of the unique features of the R and RHD Series include:
- Large heat transfer area
- Single and multiple tube options, all with removable tubes
- Reduced pressure drop
- High level of product recovery
- Low noise level gearbox
- Energy Efficient
- Multipass version available