Design Solution

Temperature Design Logic

The warehouse design benchmark temperature is set at -20°C, with the operating control range of -18°C ~ -20°C. Ambient thermal parameters are calculated based on Shanghai’s extreme summer high temperature of 38°C.

Heat load calculation covers heat infiltration from 8 daily door openings, heat carried by incoming goods, heat dissipation from lighting and equipment. A 15% cooling capacity redundancy is reserved to guarantee stable temperatures under peak operation conditions.

Refrigeration System Design

Two fully independent piston refrigeration systems are configured, each serving one 300 m³ cold storage room, with a single system capable of fully meeting the cooling demand of its corresponding warehouse. Bypass pipelines and switching valves are installed between the two systems. If one unit malfunctions, valves can be switched to allow the other system to temporarily bear the cooling load of the faulty warehouse, securing product storage safety.

Air-cooled condensers are adopted, eliminating the need for municipal cooling water supply, matching the supporting conditions of the logistics park and lowering operation & maintenance difficulty.

Backup System Design

The control system is equipped with an uninterruptible power supply (UPS), which can sustain temperature data collection and upload functions for no less than 2 hours during mains power failure. The refrigeration system is fully fitted with pressure and temperature protection devices that automatically shut down the unit and trigger alarms once abnormal conditions occur.

Equipment Configuration

Construction Process

The total construction cycle of this project is 28 days, strictly executed in accordance with the construction schedule.

During insulation panel installation, 150mm-thick polyurethane sandwich panels with tongue-and-groove joints are used for wall and ceiling assembly. Polyurethane foam is injected to seal all panel seams. Aluminum trim strips and vapor barrier films are applied at the joints between panels and floors to prevent moisture infiltration into the insulation layer.

For refrigeration equipment installation, air-cooled condensing units are mounted on outdoor machinery room platforms with concrete vibration-damping bases; unit horizontal deviation is controlled within 0.1 mm/m. Indoor air coolers are ceiling-hung with a 200 mm ventilation gap reserved between coolers and ceilings. Air outlets are arranged along the warehouse length to ensure even air distribution.

Seamless steel pipes are used for piping construction with full GTAW argon arc welding; pipe ends are polished and cleaned prior to welding. After piping installation, a 2.4 MPa nitrogen pressure retention test is performed for 24 hours, with allowable pressure drop limited to ≤0.02 MPa. The system is then vacuumed down to below -0.1 MPa. All pipes are wrapped with 30 mm rubber & plastic thermal insulation cotton and covered with aluminum foil for outer protection.

In electrical installation, power cables and signal cables are laid separately with a minimum spacing of 200 mm to avoid signal interference. Control cabinets are reliably grounded with grounding resistance tested below 4 Ω. Temperature sensors are installed at warehouse return air zones and cargo storage areas to ensure readings accurately reflect actual storage temperatures.

Commissioning & Acceptance

Temperature Testing

A no-load cooling test is carried out first. Under an ambient temperature of 32°C, both warehouses cool down from an initial room temperature of 25°C to -20°C in an average of 2 hours and 47 minutes, meeting design standards.

After temperature stabilization, 9 temperature measuring points are set inside each warehouse (3 layers vertically, 3 points per layer). Continuous 24-hour monitoring data shows temperature deviation at all points is no more than ±0.6°C, satisfying uniformity requirements.

Operational Testing

A 72-hour continuous full-load test is conducted, simulating 8 daily door openings of 10 minutes each. Test results show the maximum temperature rise during door opening reaches 1.8°C, and temperatures drop back below -18°C within an average of 12 minutes after door closure.

In dual-system switchover testing, the total time for valve switching and unit startup is less than 30 seconds, with no obvious temperature fluctuation during the process.

Acceptance Workflow

The construction team first completes self-inspection and rectifies all installation defects. Project engineers then conduct separate acceptance checks for four modules: warehouse insulation, refrigeration system, electrical system and control system.

Finally, the client and a third-party testing institute are invited to verify temperature uniformity and issue an official test report. Once all parameters comply with design and code requirements, both parties sign the final acceptance certificate.

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