ECNU Hedong Canteen Dual-Temperature Cold Storage Project

Core Refrigeration System Configuration

This project adopts a dual independent refrigeration system with German BITZER semi-hermetic piston condensing units. Separate circuits for freezer and chiller zones eliminate cross-odor interference and temperature mutual impact.

Technical Design Highlights

R449A refrigerant is applied to replace traditional R404A, cutting GWP significantly from 3922 to 1397. Fully verified for BITZER compressors, it improves cooling efficiency by 6–8% under freezing conditions.

The freezer adopts 6mm large-fin spacing evaporators to delay frost bridging and reduce defrost frequency. The chiller uses 4.5mm fin spacing to enhance heat exchange under humid conditions, with automatic shutdown defrost to lower energy consumption.

Each unit is equipped with an independent oil separator, liquid receiver, filter drier and sight glass, ensuring stable lubrication and refrigerant cleanliness, and guaranteeing reliable low-load operation during university vacation periods.

Sanitary Cold Storage Structure & Construction

Dual-color steel polyurethane insulated panels are used for the enclosure: 150mm B1 fire-rated panels (40±2kg/m³ density) for the freezer and 100mm panels for the chiller. Panels are installed with eccentric hook connection and on-site foam sealing for complete cold bridge elimination.

The floor is fully covered with 5mm patterned aluminum plates, with all joints argon-arc welded and polished for seamless transition with curved internal corners. The anti-slip, corrosion-resistant and impact-resistant aluminum floor is laid on a vapor barrier and XPS insulation layer to prevent frost heave.

The freezer is fitted with self-closing swing doors with embedded frame anti-condensation heaters. The chiller adopts pinch-proof automatic rebound doors. Linked air curtains activate synchronously with door switches to block humid hot air infiltration during door opening.

Intelligent Control & Energy-saving Strategy

Powered by Siemens Logo! 8.3 controller and PT100 temperature sensors, the system delivers independent PID regulation for dual zones, achieving high precision temperature control within ±0.8°C.

A custom rapid cooling response mode is programmed to handle frequent impulse heat loads during meal peaks. The system identifies temperature rising slopes after stock loading, extends cooling cycles and temporarily relaxes start-stop protection to avoid frequent compressor cycling, restoring standard precision once the set temperature is stabilized.

EC variable-speed condenser fans adjust rotation speed automatically based on condensing pressure, with night static mode limiting operating noise below 52 dB(A) to comply with campus noise regulations.

Integrated 4G DTU module enables real-time remote alarm push to canteen managers and maintenance teams. Traceable temperature and humidity historical data accessible via mobile mini-programs fully meets HACCP food safety supervision standards.

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