The Contherm range spans five distinct models. Each is engineered around a shared set of proven core components — heat transfer cylinder, mechanical seals, and scraping blades — but the configurations differ meaningfully in terms of viscosity range, pressure capability, installation orientation, and surface area. Choosing the wrong model adds unnecessary capital cost or, worse, limits throughput and increases maintenance demand.

Contherm Core

Contherm Core is the entry-level model, designed specifically for low to medium-viscosity products in the 1,000–50,000 cP range. It uses the same pressure vessel components, mechanical seals, and scraping blades as the traditional Contherm, but in a simplified horizontal frame. Up to three units can be stacked vertically, which minimises pipe runs and reduces installation complexity. The horizontal configuration also means all components are accessible at floor level — a practical advantage during routine service. Capital expenditure savings of up to 15% are achievable compared with more complex single-wall configurations, according to Alfa Laval product data.

Contherm and Contherm HP

The traditional Contherm is the most versatile model in the range. It handles viscosities well above 50,000 cP, supports aerated products, and can be configured for cryogenic cooling. Each vertical unit has its own hydraulic lifting device for safe, fast rotor removal during maintenance. The Contherm HP shares this foundation but is built for system pressures up to 41 bar (600 psi), twice the rating of a standard single-wall unit. A self-aligning rotor design eliminates coupling components and simplifies installation. Both models accept a wide range of blade materials, rotor diameters, and seal configurations to suit specific product and process requirements.

Contherm Max

Contherm Max is a double-wall scraped surface heat exchanger. Its inner and outer heat transfer surfaces together deliver 4.5 times more surface area than the largest traditional single-wall Contherm unit, providing the thermal equivalent of three conventional single-wall scraped surface heat exchangers in a single vertical footprint. The product path between the two walls is 55 mm wide, which keeps shear forces low — an important factor for products containing large particles or shear-sensitive ingredients. A single-drive motor reduces energy consumption by 10–30% compared with equivalent multi-unit configurations. The unit arrives fully assembled, requiring no connection to walls or ceilings, which reduces installation time and floor space requirements by up to 80% versus horizontally installed alternatives.

Convap scraped surface evaporator

Convap is a modified Contherm designed for continuous evaporation rather than heating or cooling. Operating under vacuum, it concentrates viscous and heat-sensitive products to extremely high solids levels — in some applications up to 99% total solids. A vapour dome and separator vessel are integrated into the unit to allow vapour separation from the concentrate. Products that become progressively more viscous during concentration are well-suited to the Convap because the continuous scraping action prevents burn-on, even as the product thickens. Typical applications include fruit purées, protein solutions, sugar concentrates, coffee extracts, and pharmaceutical or chemical solutions requiring controlled evaporation.

Scraped surface heat exchangers serve any process where the product's physical properties prevent effective heat transfer in conventional equipment. High viscosity increases the boundary layer resistance at the heat transfer wall; fouling deposits insulate the surface; large or fragile particles need gentle handling to preserve product integrity. Each of the industries below presents one or more of these challenges at scale.

Food and beverage processing

Food manufacturers represent the largest application segment for scraped surface heat exchangers. Products such as hummus, nut butters, pizza sauces, and fruit pie fillings share high viscosity and a tendency to foul conventional heat transfer surfaces. Prepared foods containing vegetable pieces, meat chunks, or fruit particulates need gentle handling to prevent particle damage during heating or cooling. Scraped surface technology addresses both requirements simultaneously: the rotating blades remove the fouling layer continuously while the wide product path and low rotational speeds protect particle structure.

Processing lines for these products typically position a scraped surface heat exchanger downstream of a mixing or blending stage and upstream of filling. The unit heats the product to pasteurisation temperature, holds it at temperature via an adjacent hold tube, and then cools it before packaging. CIP is carried out in place using recommended cleaning protocols, so the unit does not need to be disassembled between production runs — an operational advantage that reduces downtime and water consumption.

Confectionery and crystallising products

Sugar-based confectionery products including caramel, nougat, fondant, and biscuit creams crystallise as they cool, which creates fouling conditions that conventional equipment cannot manage. The Contherm's continuous scraping action prevents crystalline deposits from accumulating on the heat transfer wall, maintaining throughput and product consistency throughout the cooling cycle. One confectionery producer operating six Contherm units reported that the equipment eliminated the need for daily cleaning cycles that would otherwise cause hours of production downtime, according to Alfa Laval reference data.

Personal care and pharmaceutical applications

Personal care and pharmaceutical processes often impose stricter hygienic design requirements than food applications. The Contherm range is built on aseptic technology and is available with USDA and 3A hygienic design certifications. Flushed seal options support aseptic processing conditions. Products such as skin creams, lotions, gels, and pharmaceutical solutions span a wide viscosity range and frequently contain heat-sensitive active ingredients that cannot withstand elevated temperatures for extended periods. Low rotational speeds and the low internal pressure drop of the Contherm Max are well-matched to these constraints, as they minimise shear stress and thermal exposure time.

Chemical and specialty processing

Chemical applications often involve materials that are simultaneously highly viscous, prone to fouling, and subject to high system pressures. Fatty acids, solvents, and petroleum jelly all fall into this category. The Contherm HP, rated to 41 bar (600 psi), handles process conditions that exceed the capability of standard single-wall scraped surface heat exchangers. Where the objective is concentration rather than temperature change, the Convap scraped surface evaporator extends the application envelope to moisture removal under vacuum, supporting production of concentrates, pastes, and slurries across chemical and pharmaceutical sectors.

Operating principle and core components

A scraped surface heat exchanger consists of a cylindrical heat transfer wall, a rotating rotor carrying scraping blades, and an annular channel through which the heating or cooling medium flows. Product enters at the base of the cylinder and moves upward through the product path. Heating or cooling media travels in the opposite direction — counter-current to the product — through the narrow annular space between the heat transfer wall and an insulated outer jacket. Counter-current flow maximises the temperature differential between media and product along the full length of the cylinder, which drives efficient heat transfer across the entire surface area.

Rotating blades are attached to the rotor and press against the inner cylinder wall through centrifugal force. As the rotor turns, the blades continuously sweep fresh product against the heat transfer surface and remove any material that has begun to foul or deposit. This action achieves two things at once: it keeps the wall clean, preventing the insulating fouling layer from forming, and it replaces the stagnant boundary layer of product at the wall with bulk product from the centre of the flow path. Both effects increase the effective heat transfer coefficient relative to an equivalent static surface.

At the end of a production run, the product is either drained or displaced by water. Product loss is minimal because hold-up volumes are low by design. CIP is then carried out in place using standard cleaning protocols without disassembling the unit.

The double-wall design of Contherm Max

The Contherm Max extends the standard principle by introducing a second concentric heat transfer wall. Product flows through the annular gap between the inner and outer cylinders — a path approximately 55 mm wide. Scraping blades mounted on a rotating assembly clean both the inner surface of the outer cylinder and the outer surface of the inner cylinder simultaneously. Media flows through both the inner cylinder and the outer jacket.

This geometry provides 4.5 times more surface area than the largest traditional-size Contherm unit, heating or cooling the product from both sides at once. Because the product path is relatively wide and the rotational speed is low, shear forces on the product remain low — an important factor for shear-sensitive emulsions, products with large particles, or formulations where texture depends on controlled crystallisation.

Selection criteria

Selecting the correct scraped surface heat exchanger requires matching equipment capability to four primary process parameters: viscosity, particle size, system pressure, and thermal duty.

Viscosity is the primary driver. Products in the 1,000–50,000 cP range are well-served by Contherm Core. Above 50,000 cP, the traditional Contherm or Contherm HP is required, depending on pressure requirements. The Contherm Max is optimised for low to medium-viscosity products where throughput, floor space, or energy consumption are the primary constraints.

Particle size determines rotor geometry. The Contherm range accommodates particles up to 25 mm in diameter. Rotor diameter selection affects the clearance available for particles, and larger rotor diameters reduce the annular gap, which limits maximum particle size. For large or fragile particulates, the 55 mm product path of the Contherm Max provides the greatest clearance and the lowest shear conditions.

System pressure drives the choice between the standard Contherm and the Contherm HP. Standard single-wall units are rated to 15 bar (220 psi). The Contherm HP handles up to 41 bar (600 psi), which is required in processes where the product generates high internal pressures during heating — as occurs with some starch-based or high-solids formulations — or where the process line upstream operates at elevated pressure.

Thermal duty — the combination of flow rate, temperature differential, and product thermal properties — determines the number of units and the total surface area required. Because the Contherm Max provides 4.5 times the surface area of the largest traditional single-wall unit in a single compact footprint, it reduces both the unit count and the total floor space required for a given thermal duty.

Comparison with plate and tubular heat exchangers

Plate heat exchangers are efficient and compact for low-viscosity, non-fouling products, but their narrow flow channels create high pressure drops with viscous fluids and clog quickly with particulates. Tubular heat exchangers tolerate higher viscosity and larger particles, but they provide lower heat transfer coefficients and require more surface area to achieve equivalent thermal duty. Scraped surface heat exchangers carry a higher capital cost than either alternative; however, for products that cause fouling, the reduction in cleaning frequency, downtime, and maintenance offsets this over the equipment lifetime. Alfa Laval data from deployed installations documents energy savings of up to 33% and floor space reductions of up to 80% when switching from multi-unit horizontal configurations to a single Contherm Max, illustrating how total cost of ownership figures can shift when the comparison accounts for operational costs rather than purchase price alone.

Certification and hygienic design

The Contherm range is manufactured to ASME and PED pressure vessel standards. USDA and 3A hygienic design certifications are available for applications in food, dairy, and pharmaceutical sectors where those standards are required. Heat transfer surfaces are available in 316L stainless steel or Duplex 2205, honed to a hygienic finish. Scraping blades are manufactured from FDA- and EU-compliant polymer materials, including metal-detectable grades. These material and certification choices allow the same fundamental design to serve both food-grade and pharmaceutical-grade processing environments.