Evaporator for Fish Freeze IQF Tunnel

Evaporator for Fish Freeze IQF Tunnel

Principle of operation

The fish IQF tunnel evaporator is the core heat transfer component of the quick-freezing system, and its working principle is based on the process of evaporation and heat absorption in the refrigerant cycle:

Refrigerant cycle: The low-temperature, low-pressure liquid refrigerant (e.g. ammonia, Freon or carbon dioxide) enters the heat exchanger tubes of the evaporator, absorbs heat from the air outside the tubes and then evaporates into a gaseous state, while causing the surrounding air temperature to drop drastically (usually down to - 30℃~-45℃).

Cold air circulation: the fan drives the low-temperature air to flow at high speed in the tunnel (the wind speed is generally 3~10m/s), which is in direct contact with the fish on the conveyor belt, and takes away the heat from the fish body quickly through forced convection to realize the single-unit quick-freezing.

Temperature control: the heat exchange efficiency of the evaporator is closely related to the refrigerant flow, fan airflow and temperature field distribution in the tunnel, which needs to be precisely adjusted by the automated control system to ensure that the center temperature of the fish body is reduced to below -18℃ within a short period of time (usually 10~30 minutes).

Structural Characteristics

Core component design

Heat exchanger tube material:

Stainless steel (e.g. 304, 316L) or corrosion-resistant aluminum tubes are used to avoid corrosion by moisture, salt and microorganisms in the fish processing environment, which is in line with food hygiene standards.

The tube diameter is usually 10~25mm, and the thickness of tube wall is 0.5~1.5mm, taking into account the strength and thermal conductivity efficiency.

Fin structure:

The fins are made of stainless steel or aluminum foil, with hydrophilic or anticorrosive treatment on the surface to prevent frost buildup.

The fin spacing is adjusted according to the working conditions (generally 2~5mm): too small a spacing is easy to frost and blockage, too large affects the heat transfer area; fish quick-freezing scenes, often using variable-pitch fins, the entrance spacing is larger to reduce the initial frost, and the exit spacing is smaller to strengthen the heat transfer.

Frame and support:

Stainless steel frame is welded or bolted to ensure structural strength and facilitate installation and maintenance; the bottom is equipped with a drainage slot to discharge defrosting water in time and prevent bacteria from accumulating in the water.

Applications

Fish processing industry

Raw material quick-freezing: suitable for cod, salmon, shrimp, squid and other seafood monomer quick-freezing, especially suitable for export frozen food processing enterprises, to meet the quality requirements of the international market for quick-frozen aquatic products.

Prefabricated dish processing: used for quick freezing of semi-finished products such as fish ball, fish dumpling, minced fish, etc. to prevent microbial reproduction and prolong shelf life.

Equipment Matching Scenario

Matching with mesh belt IQF tunnel, spiral quick-freezer and other equipments, the processing capacity ranges from 500kg/h to 5000kg/h, and the size of evaporator can be customized according to the scale of the production line (e.g. length 5~20m, width 2~4m).

Special working conditions

For high humidity environment (e.g. fish thawing and then quick-freezing), the evaporator can be strengthened defrosting design, to avoid frequent frost affecting the production efficiency; for deep-sea fish (e.g. Antarctic krill), the evaporator can be customized ultra-low-temperature evaporator (the temperature is as low as - 50 ℃ or less), to ensure rapid freezing.