Cold Storage Engineering: Core Knowledge and Development Trends

1. Definition and Essential Attributes

Cold storage engineering is a comprehensive project integrating construction engineering and mechanical and electrical engineering, designed to create a controllable low-temperature environment for the storage, preservation, and turnover of specific items. Its core goal is to maintain the quality and safety of stored goods by precisely regulating temperature, humidity, and gas composition, while ensuring energy efficiency, operational stability, and safety of the entire system. It is widely recognized as a key link in the cold chain logistics industry, with strict technical requirements covering building structure, thermal insulation, refrigeration systems, and intelligent management.

2. Classification of Cold Storage Engineering

2.1 Classification by Function

• Storage-type cold storage: Mainly used for long-term storage of goods, such as agricultural products, fresh food, and frozen commodities. It features large scale, stable temperature (usually maintained within a fixed range), and focuses on reducing goods loss during long-term storage. Typical examples include large fresh-keeping warehouses for fruits and vegetables and frozen storage for meat.

• Circulation-type cold storage: Designed for goods transshipment and short-term storage, commonly used in logistics transfer links. It requires high efficiency of goods in and out of the warehouse, and the refrigeration system must have the capability of rapid temperature adjustment to cope with frequent cargo turnover.

2.2 Classification by Application Field

• Food industry cold storage: The largest application scenario, including fresh-keeping warehouses (0℃~5℃), refrigerated warehouses (-10℃~-18℃), and freezing warehouses (-20℃~-35℃). It is used to store fruits, vegetables, meat, seafood, and processed food, ensuring food safety and extending shelf life.

• Medical industry cold storage: Has extremely strict temperature control requirements (precision up to ±0.5℃), used for storing vaccines, drugs, biological samples, and other medical supplies. It must comply with GSP (Good Supply Practice for Drugs) and other regulatory standards to ensure the effectiveness and safety of medical materials.

• Special cold storage: Including controlled atmosphere warehouses (regulating oxygen and carbon dioxide concentration to extend fresh-keeping period) and ultra-low temperature cold storage (≤-40℃ for biological products and special materials).

3. Core Technical System of Cold Storage Engineering

3.1 Thermal Insulation System: The Foundation of Energy Conservation

Thermal insulation performance directly determines the energy consumption and operational stability of cold storage. Polyurethane spraying is the preferred thermal insulation solution due to its excellent comprehensive performance, and its application involves material selection, thickness calculation, and construction control.

3.1.1 Material Selection

Comparing mainstream thermal insulation materials, polyurethane spraying has obvious advantages in cold storage scenarios:

3.1.2 Key Parameters for Polyurethane Selection

• Density: Determined by cold storage temperature. 35-40kg/m³ for high-temperature cold storage, 40-45kg/m³ for medium-temperature, 45-50kg/m³ for low-temperature, and ≥50kg/m³ for ultra-low temperature.

• Flame Retardant Grade: Must reach B1 grade or above to meet fire safety requirements, with low smoke density and no toxic gas emission.

• Closed Cell Rate: ≥90% to prevent condensation and moisture penetration, ensuring long-term insulation effect.

3.1.3 Thickness Calculation Method

The thickness of polyurethane spraying is calculated using the simplified formula: δ = λ×(t2 - t1)÷q, where:

• δ: Insulation thickness (m)

• λ: Thermal conductivity of polyurethane (0.024 W/(m·K) for conventional use)

• t1: Cold storage design temperature (℃)

• t2: Local extreme minimum ambient temperature (℃)

• q: Allowable heat flux (0.3-0.6 W/(㎡·K), lower for low-temperature cold storage)

In practical construction, the thickness of ceilings and floors should be increased by 2-3cm, and a 1-2cm safety margin should be reserved to compensate for construction deviations.

3.2 Structural Design: Safety and Durability

Cold storage structures must balance thermal insulation, structural stability, and equipment installation needs, following national standards such as GB 50072-2010 Code for Design of Cold Storage.

• Structural Types: Civil engineering structures (suitable for large multi-layer cold storage with good durability), prefabricated structures (short construction period, high seismic performance), and plate frame structures (lightweight, suitable for small cold storage).

• Key Design Points: Adopt reinforced concrete frame structure to ensure stability; strengthen thermal insulation and moisture-proof treatment of enclosures; reserve sufficient space for refrigeration equipment and pipelines; design arc-shaped internal and external corners to avoid cracking due to stress concentration.

3.3 Refrigeration System: Core of Temperature Control

The refrigeration system is the "heart" of cold storage, consisting of compressors, evaporators, condensers, and expansion valves. Its selection and configuration directly affect temperature control precision and energy efficiency.

• Compressors: Screw compressors are widely used for their high efficiency and stability, while piston compressors are suitable for small and medium-sized cold storage.

• Energy-Saving Technologies: Inverter refrigeration units adjust operating frequency according to load; environmentally friendly refrigerants (R290, R600a) replace traditional ones to reduce environmental impact; waste heat recovery technology recycles heat from refrigeration for defrosting and domestic water.

4. Intelligent and Environmental Protection Development Trends

4.1 Green Construction

Modular construction reduces construction waste; photovoltaic building integration (BIPV) technology uses solar energy to supply power for lighting and auxiliary equipment; environmentally friendly insulation materials (modified polyurethane, vacuum insulation panels) achieve low VOC emissions and recyclability.

4.2 Intelligent Management

IoT sensors collect real-time temperature and humidity data, which is transmitted to the cloud platform via 5G. AI algorithms automatically optimize refrigeration parameters, reducing energy consumption by 25%-40% and food loss rate by over 30%. Remote monitoring and intelligent scheduling realize unattended operation and rapid fault response.

4.3 Resource Recycling

Build a closed-loop resource system: classify and recycle packaging waste with a recovery rate of over 85%; purify and reuse waste oil from refrigeration systems; treat cleaning wastewater for floor flushing and green irrigation. Some advanced projects convert organic waste into biomass energy through anaerobic fermentation.

5. Construction and Acceptance Key Points

• Construction Control: Polyurethane spraying is conducted in layers (10-15mm per layer) after the previous layer is cured; construction temperature should be above 10℃; seal gaps of doors, windows, and pipes with polyurethane foam.

• Acceptance Standards: Use the needle insertion method to detect thickness, with a deviation of ≤±5mm; sample test closed cell rate to ensure it is ≥90%; check for no cracks, bubbles, or missing spraying on the surface.

Conclusion

Cold storage engineering is a technology-intensive field that continues to evolve with the demands of energy conservation, environmental protection, and intelligence. From material selection and structural design to system operation and management, every link requires strict technical control. With the deepening of the "double carbon" goal and the upgrading of cold chain logistics, intelligent and environmentally friendly cold storage will become the mainstream, transforming from a single storage function to an integrated service platform, providing strong support for food safety, medical security, and sustainable development.