Design Solution

Temperature Design Concept

The six cold rooms are divided into three temperature zones based on storage purposes:

One freezer at -18~-15°C for finished quick-frozen food;

Two chill rooms at 0~5°C for fresh raw materials and food accessories;

Two constant-temperature rooms locked at 2~8°C exclusively for pharmaceutical excipients (temperature range non-adjustable at will);

One adjustable turnover room at 10~18°C.

Each room is equipped with an independent temperature control system supporting stepless regulation within its designated range, covering the full temperature spectrum from -18°C to 18°C. The pharmaceutical zones are separately fitted with humidity control modules to maintain relative humidity at 45%–65% in compliance with GSP standards.

Refrigeration System Design

An independent direct-expansion refrigeration system is adopted with one unit per room. New freezers are equipped with Bitzer 4TES-9Y air-cooled piston condensing units, while chill and constant-temperature rooms use Bitzer 4TCS-8.2Y units with R404A refrigerant.

The two original cold rooms retain their existing insulated enclosures; only compressors and air coolers are replaced and connected to the new centralized electric control system.

Dual-evaporator redundant design is applied to pharmaceutical constant-temperature rooms: one primary and one standby evaporator automatically switch within 30 seconds upon failure to prevent temperature spikes.

Condensers are oversized by 15% to cope with Shanghai’s hot summers, ensuring stable unit operation at ambient temperatures up to 40°C with discharge pressure kept below 1.8 MPa.

Backup System Design

One spare 4TES-9Y compressor is installed, connectable to any cold room’s refrigerant circuit via manifold valves. Manual switching puts the spare unit into service within 10 minutes if the main unit malfunctions.

A Santak C1K online UPS supplies power to temperature monitoring systems, alarm modules and core control cabinet components, providing no less than 4 hours of backup runtime during power outages to guarantee uninterrupted temperature logging and fault alerts.

Equipment List

Construction Process

Insulated Panel Installation

Interlocking polyurethane insulated panels are used for enclosure construction. A PE moisture barrier is laid on the floor prior to floor panel installation. Wall and ceiling panels are locked with eccentric hooks, and all joints are filled on-site with polyurethane foam and sealed with food-grade mildew-resistant sealant.

Freezer floors are reinforced with an additional 50mm steel-reinforced concrete protective layer to withstand rack and forklift loads.

Double sealing is implemented at all panel joints in pharmaceutical zones, and partition walls between rooms adopt double-layer panel structures to block odor penetration. Cold storage doors are fitted with electric heating anti-condensation gaskets and automatic door closers to reduce cold loss and ingress of hot humid air during openings.

Refrigeration Equipment Installation

Outdoor condensing units are mounted on dedicated factory equipment platforms with concrete shock-absorbing foundations. Unit horizontal deviation is controlled within 2mm/m, with a minimum 1.5m clearance around each unit for maintenance and ventilation to avoid hot air recirculation short circuits.

Indoor air coolers are suspended via hangers with shock-absorbing springs, with air outlets aligned along the room’s length to prevent direct cold blast onto stored goods.

Before renovating original cold rooms, old pipelines are purged with 0.8MPa nitrogen to remove debris and residual compressor oil. New units are connected only after passing pressure testing, with all connection work scheduled for low-traffic night shifts when room temperatures remain stable.

Piping Construction

TP2 seamless copper tubes are used for refrigerant piping, with all welding performed under nitrogen shielding to avoid oxide scale inside pipes. Suction lines slope 3‰ toward compressors, and oil traps are installed along long pipe runs to ensure smooth oil return.

After piping installation, a 2.4MPa nitrogen pressure holding test is conducted for 24 hours; a pressure drop ≤0.02MPa is deemed qualified. The system is then vacuumed below -0.1MPa. Once vacuum pressure holds steady for 2 hours without rebound, R404A refrigerant is charged to rated specifications.

Electrical System Installation

Power cables and signal cables are laid separately with a minimum horizontal separation of 200mm to eliminate electromagnetic interference that distorts temperature readings. Each compressor unit is protected by an independent circuit breaker, thermal overload relay and phase sequence protector; control cabinets are equipped with surge protection to withstand thunderstorm weather common in Shanghai.

Temperature and humidity recorders for pharmaceutical zones feature independent power supply and data transmission circuits, isolated from refrigeration control systems. This satisfies GSP rules prohibiting monitoring equipment linkage with refrigeration machinery and guarantees authentic, independent monitoring data.

Commissioning & Acceptance

Temperature Testing

Stepwise gradient cooling commissioning is adopted: the set temperature is lowered gradually at 5°C per hour. After stable 24-hour operation, temperature uniformity testing is carried out.

5 measuring points are arranged inside the freezer, while 9 points are deployed in pharmaceutical constant-temperature rooms per GSP requirements, covering corners, doorways, air outlets and upper/lower rack levels. Data is collected every 10 minutes.

Test results:

-18°C freezer: temperature fluctuation ≤±0.7°C, maximum indoor temperature difference 0.9°C;

2~8°C pharmaceutical room: temperature fluctuation ≤±0.3°C, maximum indoor temperature difference 0.5°C.

All indicators meet design and compliance standards.

Operational Testing

A 72-hour continuous full-load test is completed. Condenser air intake is partially blocked to simulate 38°C high ambient temperature; compressor discharge temperature, operating pressure and current all stay within rated ranges.

Door opening heat load test results:

After 5 minutes of full door opening, freezer temperature rises 1.8°C and recovers to setpoint within 12 minutes after door closure;

Pharmaceutical room temperature rises 1.2°C and returns to normal within 8 minutes.

Spare unit switching test: the standby unit starts fully within 120 seconds after the main unit shuts down, with no excessive temperature deviation inside the room.

Acceptance Procedure

The construction contractor first completes full-system self-inspection and issues a self-check report, pipeline pressure test records and raw temperature validation data.

The client then collaborates with a third-party cold chain testing institute to conduct itemized acceptance in accordance with GB 50072 Cold Storage Design Standard, food SC hygiene specifications and pharmaceutical GSP requirements, covering enclosure insulation performance, refrigeration operating parameters, electrical safety and compliance of temperature control systems. A dedicated GSP temperature validation report is issued separately for pharmaceutical zones.

All test items passed inspection on November 18, 2025. Both parties signed the final acceptance document, marking official project handover and commissioning.

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