Continuous Ice Cream Freezer

Overview

A continuous ice cream freezer turns liquid mix into soft, aerated frozen product in a single pass, unlike a batch freezer that fills, freezes, and empties one drum at a time. Chilled mix from the ageing tank is pumped into a Freezing Cylinder whose inner wall is held below the freezing point by a refrigerant jacket. A rotating dasher scrapes the thin frozen film off the wall while air is metered into the stream, so the product leaving the outlet is partly frozen and whipped to a target overrun. Downstream equipment handles hardening, filling, and packaging. The continuous design suits plants running steady volumes because output and quality hold constant for hours rather than swinging batch to batch.

Freezing cylinder

The Freezing Cylinder is the core heat exchanger. An Inner Barrel of honed 316L stainless steel presents a smooth bore to the mix, and a welded Refrigerant Jacket inside the Jacket Shell floods the barrel exterior with evaporating refrigerant. As mix contacts the wall it freezes into a thin layer that must be removed before it insulates the surface, which is the whole reason for the scraping action. The barrel is closed by a Front Head carrying the product outlet and a Rear Head carrying the mix inlet and the dasher drive penetration, each sealed with a sanitary Head Seal.

Dasher and scraping

Inside the barrel, the Dasher and Scraper Assembly does two jobs at once. A Dasher Shaft carries two spring-loaded Scraper Blade units that shave the frozen film off the wall on every pass, exposing fresh warm mix to the cold surface and keeping the heat transfer rate high. The same rotor carries Beater Bar elements that fold the injected air into the slurry to build a fine bubble structure. Blade pressure comes from a set of Coil Spring elements so the edge tracks the bore as it wears. Dasher speed runs from 150 to 600 rpm: faster speeds whip more air and warm the product slightly, slower speeds give a stiffer draw, so speed becomes one of the operator's main quality levers.

Drive and torque sensing

Turning the dasher against stiff frozen product takes real torque, so the Dasher Drive uses a Dasher Drive Motor feeding a reduction Gearbox Housing with a Helical Gear Pair stack and a Drive Coupling to the shaft. A Drive Torque Sensor on the drive reads how hard the dasher is working, and because torque tracks product stiffness, the control system uses it as a viscosity signal. When the draw gets too stiff the controller can raise the evaporating temperature or slow the mix, and when it gets too soft it does the opposite. The motor runs from a Variable-Frequency Drive so speed is set in software rather than by belt changes.

Refrigeration

The Refrigeration System circuit removes the freezing load from the jacket. A Refrigerant Compressor of 15 to 55 kW raises refrigerant pressure, a Condenser rejects the heat, and a Liquid Receiver buffers liquid before a Expansion Valve meters it into the jacket at the right rate to hold the draw temperature near -5 °C. A Suction Accumulator keeps liquid from reaching the compressor, and a Pressure Sensor on each side closes the control loop. Ammonia is common in large dairy plants for its efficiency, while R404A appears on smaller skid-mounted units.

Overrun and air injection

Overrun is the volume of air beaten into the product, expressed as a percentage of the mix volume, and it sets the texture and yield. The Overrun and Air Injection feeds filtered air from an Air Compressor through a Sterile Air Filter and a Air Mass Flow Controller into the Air Injection Port on the mix line. Metering air by mass flow, rather than by pressure alone, gives a repeatable overrun across changes in mix rate. A Back-Pressure Valve holds the cylinder at 3 to 6 bar so the air stays dissolved and finely dispersed until the product leaves. Premium ice cream runs lower overrun near 80%, economy product runs higher toward 120%.

Mix feed, product pump, and control

The Mix Feed System system draws mix from a Balance Tank through a Mix Strainer and meters it with a Mix Feed Pump and a Mix Flow Meter. On the outlet, the Product Pump is a positive-displacement head that pushes the stiff aerated product to the filler at a steady pressure. Tying it together, the Control Panel and Instrumentation reads the Product Temperature Probe, the Viscosity Sensor, and the Overrun Meter, then trims the drives and the expansion valve to hold all three on target. When a run ends, the CIP System cleans the cylinder and pumps in place, sending caustic and acid through a CIP Spray Head without opening the sanitary boundary.