A tunnel freezer is a highly efficient device that uses low-temperature, high-speed airflow to rapidly freeze food. It is widely used in the food, pharmaceutical, and chemical industries. Its core features are a negative pressure environment and a multi-layer mesh belt conveyor structure. This system reduces the core temperature of food to below -18°C within 20-40 minutes, preventing ice crystals from damaging the cell structure and preserving the food's nutrients and taste to the maximum extent possible.
I. Operating Principle and Structure
Operating Principle
A tunnel freezer uses a negative pressure system to lower the temperature inside the tunnel to below the freezing point of the food. High-speed airflow accelerates heat exchange. During food conveyance, surface moisture rapidly condenses into frost, forming a protective layer that blocks oxygen ingress. Simultaneously, moisture within the food crystallizes evenly at low temperatures, preventing large ice crystals from piercing cell walls and thus preserving the food's texture.
Structure
Conveyor System: Utilizing a single or multi-layer stainless steel mesh belt (a double mesh belt design can shorten the tunnel length), the food moves through the freezing zone at a constant speed, ensuring even cooling. Refrigeration System: Consisting of a compressor, condenser, and evaporator, it uses refrigerants such as Freon or liquid nitrogen to achieve rapid cooling. Liquid nitrogen quick freezers utilize -196°C liquid nitrogen to directly vaporize and absorb heat, resulting in higher freezing efficiency.
Air Circulation System: High-efficiency fans circulate cold air within the tunnel. A unique wind field design optimizes air velocity and temperature uniformity, minimizing windage and energy consumption.
Control System: Integrated PLC and touchscreen control supports real-time adjustment of parameters such as temperature, speed, and time, and features manual/automatic mode switching.
II. Technical Features and Advantages
High Quick Freezing Efficiency
Short Freezing Time: Depending on the type and thickness of food, freezing time is as short as 20-40 minutes, over 50% shorter than traditional freezing equipment.
High Output: The continuous production mode enables a single unit to process several tons of food per day, meeting the needs of large-scale industrial production. Low Energy Consumption: The all-aluminum or copper-aluminum evaporator offers high heat transfer efficiency. Combined with a high-efficiency fan and variable frequency drive technology, energy consumption per unit of production is 20%-30% lower than traditional equipment.
Excellent Frozen Product Quality
Fine Ice Crystals: Rapid freezing keeps ice crystal diameters below 50μm, preventing cell structure damage and preserving the original texture and taste of food.
Nutrient Retention: Nutrient loss during freezing is less than 5%, ensuring color and flavor similar to fresh food.
Long Shelf Life: Frozen food maintains a shelf life over three times longer than traditional freezing equipment, extending shelf life to 12-18 months.
Easy Operation and Hygiene
High Level of Automation: One-touch start and process profile storage are supported, along with over 20 preset quick-freezing programs, reducing manual intervention.
Easy Cleaning: The all-stainless steel interior and open design facilitate regular cleaning and comply with HACCP hygiene standards.
Safety and Reliability: The double-sealed door and anti-freeze heating system ensure smooth opening, preventing cold air leakage and microbial growth. III. Application Areas and Case Studies
Food Industry
Quick-frozen fruits and vegetables, such as asparagus, potatoes, and corn kernels, maintain their crispness and vitamin content.
Quick-frozen meats, such as cut meats, chicken nuggets, and fish fillets, reduce juice loss and increase yield.
Quick-frozen pasta, such as dumplings, spring rolls, and glutinous rice balls, prevent cracking and deformation, and enhance product value.
Pre-prepared meals, such as seasoned crayfish and spicy rabbit, quickly lock in freshness and meet the standardized requirements of chain restaurants.
Pharmaceutical and Chemical Industries
Pharmaceutical: Suitable for cryogenic storage of biological products such as vaccines and serums, ensuring the stability of active ingredients.
Chemical: Suitable for cryogenic freezing of powdered raw materials, preventing clumping and deterioration.
Typical Case Studies
Shenzhen Dejieli Liquid Nitrogen Quick Freezer: A single machine has a freezing capacity of 5,000 kg/h. Utilizing -196°C liquid nitrogen ultra-low temperature freezing technology, ice crystals are less than 20 μm in diameter. It is widely used in high-end food processing, including seafood and meat. Shandong Onar Tunnel Quick Freezer: Utilizing a rigid polyurethane foam chamber and imported frequency converters, it supports stepless speed regulation and continuous production. Its frozen products meet export food hygiene standards and are selected by numerous domestic food companies.
IV. Selection and Maintenance Recommendations
Selection Parameters
Freeze-drying Area: Select based on production scale, e.g., 0.12 m2 (laboratory model) to 30 m2 (production model).
Cold Trap Temperature: The general standard is -60°C, with -80°C optional for special needs.
Plate Temperature Uniformity: Medical equipment must maintain a temperature uniformity within ±1.5°C.
Ultimate Vacuum: The no-load ultimate vacuum should be above 15 Pa.
Maintenance
Regular Cleaning: Clean internal dust and debris weekly, and inspect the equipment's operating status monthly.
Replacement of Wear Parts: Replace seals and drive chains quarterly, and inspect the compressor and fan annually.
Leak Detection: When the equipment is out of service for an extended period, perform a leak detection and automotive-grade maintenance (such as adding lubricating oil and hydraulic fluid).
