Thermo King Super Freezer
The Thermo King Super Freezer unit (model CRR-40DF) represents a cutting-edge solution for the transport and storage of deeply frozen products with temperatures down to -70°C. This technical analysis addresses the detailed specification, design properties, and operational characteristics of this advanced refrigeration unit intended for international maritime transport, road transport, and storage.
1. Introduction and Application Spectrum of SuperFreezer Unit
Thermo King SuperFreezer is specially designed for critical applications requiring extremely low temperatures. The unit utilizes cascade technology, which combines two independent refrigeration circuits with different refrigerants to achieve and maintain ultra-low temperatures. This innovative architecture enables safe protection of the most valuable and sensitive cargo.
SuperFreezer unit applications include the transport of pharmaceutical products (including vaccines and API – active pharmaceutical ingredients), biological materials (blood plasma, biological samples), food ingredients (yogurt cultures, seafood), chemical enzymes, semiconductor components, and other temperature-sensitive products. The unit is certified according to the strictest international standards including ISO 1496-2, CE, AHRI, TIR (International Customs Regulations for containers) and USDA.
2. Basic Technical Specifications and Design Properties
| Parameter | Specification | Note |
|---|---|---|
| Manufacturer | Thermo King Corporation | Part of Trane Technologies |
| Model | CRR-40DF | Picture frame type unit |
| Width | 2025.5 mm | Standard ISO container |
| Height | 2235.2 mm | Full container height |
| Depth | 420.0 mm (from rear flange) | Minimal space requirement |
| Weight | 630 kg | Complete unit |
| Electrical Voltage (3-phase) | 400-500 V (60 Hz) / 360-460 V (50 Hz) | ±2.5% tolerance |
| Maximum Power Consumption at Pull-down | 19 kW | Initial cooling cycle |
| Control Circuit | 29 V AC | Low-voltage safety circuit |
| Heating Method | Electric resistance | Defrosting and temperature control |
| Air Leakage through Unit | < 0.5 m³/h (at 76 mm WG) | Controlled atmosphere |
| Heat Leakage through Unit | < 3.4 kcal/h/°C (3.95 W/°C) | Polyurethane insulation |
| Test Pressure (R23) | 39 bar (PED Directive 746) | Safety standard |
| Volume of Pressure Vessels | 26.5 liters | Sum of all vessels |
| Color (RAL) | Off-white RAL 9016/85 (unit) / Black (piping) | Polyester powder coating |
Design Materials and Protection: The unit is constructed from aluminum series 5000 and 6000, which is pre-treated and painted with polyester powder according to ISO standards 7253 and 2409 with classification 1. The coating film thickness is 100 micrometers. Between the evaporator and condenser is placed fire-resistant and CFC-free polyurethane foam (ISO 3582) with nominal density 32 kg/m³ and average thickness 52 mm. All operational components except the evaporator coil are replaceable from the front of the unit.
3. Cooling System – Cascade Architecture with Two Circuits
The heart of the SuperFreezer unit is the cascade cooling system, which operates on the principle of two independent refrigeration circuits. The primary circuit (R-134a) conditions the refrigerant of the secondary circuit, while the secondary circuit (R-23) directly freezes the cargo through the evaporator coil. This system enables the achievement of extremely low temperatures that would be impossible with a single refrigerant.
| Component | R-134a Specification | R-23 Specification |
|---|---|---|
| Compressor | Copeland D3DSTA-075E-TFD | Copeland ZF18K4E-TFD-277 |
| Type | 3-cylinder reciprocating | Rotary (scroll) |
| Stroke/Diameter | 61.9 x 63.5 mm | N/A (scroll type) |
| Displacement | 60 m³/h | 20.5 m³/h |
| Speed (60 Hz) | 1750 rpm | N/A |
| Nominal Power | N/A | 6 HP |
| Refrigerant (Charge) | 3.5 kg | 3.2 kg |
| Recommended Oils | Copeland Ultra 22CC, Mobil EAL 22CC, ICI Emkarate RL32CF | Special oil for R-23 |
| Internal Thermal Protection | Automatic reset | Automatic reset |
| High Pressure | 24.1 bar | 30 bar |
| Low Pressure | 1 bar | 2-3 bar |
Evaporator Coil: The evaporator coil is made of copper (DIN 1787, wall thickness 0.45 mm) with aluminum fins (DIN 1712/A199). The fin pitch is 3.17 mm, surface area is 58 m² and the unit has 10 injection points. The coil is treated with a hydrophilic surface resistant to corrosion caused by salt spray. Manufacturers are Dalian, Dunan or equivalent suppliers.
Condenser (Air-cooled): The condenser is constructed from copper (wall thickness 0.45 mm) with copper fins in a circular configuration. The fin pitch is 2.00 mm, surface area is 34.5 m². The unit contains a subcooling area of 4.6 m² for R-134a and 2.3 m² for R-23. UV protection is provided by epoxy e-coat with polyurethane topcoat.
Heat Exchanger: The SWEP B27 type heat exchanger with 34 stainless steel plates has a cooling capacity of 12 kW and maximum working pressure of 30 bar. This component is key to efficient heat transfer between the two cooling circuits.
4. Fans, Motors and Defrosting System
Evaporator Fans: The unit is equipped with three propeller fans with a diameter of 355 mm with eight blades made of glass-reinforced polyamide. The fans run at low speed (1725 rpm at 60 Hz) and are connected directly to the motor shaft with a blade pitch of 22 degrees. The fans run continuously at low speed except during the defrosting cycle.
Condenser and Its Drive: The condensing fan is a propeller type with a diameter of 550 mm with one piece and eight blades. It runs at 1750 rpm (60 Hz) with a blade pitch of 35 degrees and produces an air flow of 6000 m³/h. The condensing fan is driven by a 1.5 kW motor, fully enclosed, non-ventilated type with journal bearings, stainless steel shaft and class F insulation.
Evaporator Fan Motors: Each of the three evaporator fan motors has a nominal power of 0.75 kW and is constructed with separate windings for high and low speed. The motors are fully enclosed, non-ventilated, with journal bearings (6205 and 6203) lubricated with Mobil 28 lubricant. Temperature range is -65°C to 65°C. Each winding has internal thermal protection with automatic reset.
Defrosting System: The unit is equipped with 12 defrosting heaters with a power of 680 W each, with a total defrosting capacity of 8160 W (460V/60 Hz) or 6000 W (380V/50 Hz). The defrosting drain pan with high edges contains two drains and plastic hoses located near the condenser and compressor to prevent freezing in cold ambient conditions.
5. MP3000 Control System and Data Logger – Advanced Temperature Control
The brain of the SuperFreezer unit is the MP3000 microprocessor controller, developed specifically for the regulation and monitoring of refrigerated containers. The controller is equipped with an integrated data logger with a communication port for connection to an optional transmission module via power cable (REFCON system).
Displays and Controls: The MP3000 is equipped with a 4-line LCD display with 20 characters per line for displaying menus and data fields. A five-segment LED display shows the current temperature used in the control algorithm. Eight LED indicators signal various operating states (error, normal operation, defrost, heater, compressor, humidity control, supply/return temperature). The keyboard has 16 universal keys and 4 shortcut keys for easy operation.
Temperature Control – Freezing Mode: The unit operates on the basis of ON-OFF control with the following algorithm: When the return air temperature drops to 1°C below the setting, the compressor stops. The minimum stop time is 10 minutes. When the temperature rises to 1°C above the setting, the R-134a system starts first, and after 30 seconds the R-23 system starts. The minimum operating time is 15 minutes. The overall control accuracy is ±1°C.
Defrosting Cycle: Defrost is controlled by a sensor in the evaporator coil. The cycle is activated when the temperature difference between the return sensor and the setting reaches a preset value and 6 hours of compressor operation have elapsed since the previous defrost. Defrost automatically terminates when the temperature in the coil reaches 18°C or if the temperature exceeds 8°C for longer than 35 minutes (at voltage > 400 V) or 45 minutes (at voltage < 400 V). Defrost is also limited to a maximum of 90 minutes (60 Hz) or 120 minutes (50 Hz). Additional safety is provided by a defrost timer with an initial 12-hour period, which increases by 6 hours up to a maximum of 36 hours.
Data Logger and Data Recording: The integrated microprocessor-based data logger records temperatures in Flash memory at preset intervals (0.5, 1, 2 or 4 hours). Temperatures from three USDA sensors, controller supply and return air sensors and set temperature are recorded. With one-hour intervals, temperature information is available for the last 625 days. The data logger continues to record 120 temperature records even after the container is disconnected from power, with a battery backing up the clock for at least 10 years.
6. Safety Elements and Regulatory Systems
Electrical Safety Elements: The unit is equipped with a Klixon thermostat with cutoff at 54°C (with reset at 32°C) to protect the compressor, condenser and evaporator motors. The main circuit breaker has a capacity of 32 A and protects the electrical circuit from overload.
Cooling Regulatory Elements: The system contains a Danfoss expansion valve (TX), dryer with moisture indicator (built into the receiver), R-134a receiver (copper construction with glass window) or R-23 receiver (stainless steel with glass window), Superior shut-off valve, Danfoss check valve, Danfoss solenoids and pressure relief valve. All components including piping are epoxy coated for corrosion protection.
Cooling System Safety Elements: The unit contains a high-pressure switch (R-134a: 24.1 bar ± 0.68 bar, R-23: 30 bar ± 0.68 bar) with reset at 16.4 bar (R-134a) or 22 bar (R-23). Low-pressure switch (R-23 only) with reset at 0.65 bar ± 0.68 bar stops both compressors at low pressure. Mercury pressure relief valve (34 bar ± 3.4/-1.0 bar) is built into the receiver. Pressure gauges (MSI, range 0-200 Psig for low pressure, 0-500 Psig for high pressure) and glass window for R-134a (solder version) allow visual inspection of the system condition.
Pressure Equalization Safety Valve: The unit is equipped with a pressure equalization valve (manufacturer AVK Plast A/S) located under the condensing motor. The valve has an opening pressure of 1400 Pa (140 mm WG), opening force of 0.4 kg (4 N) and internal diameter of 60 mm. This valve prevents excessive vacuum in the container.
7. Operating Capacity and Test Results
| Parameter | Value | Conditions / Note |
|---|---|---|
| Test Method | AHRI 1110-69 | Approved evaluation method |
| Unit Serial Number | A001018172 | MSFU 856740-4 |
| Ambient Temperature | 37.8°C (100°F) | Standard test condition |
| Frequency | 60 Hz | North America |
| Cooling Capacity at -60°C (return temperature): | ||
| Evaporator Fan | 550 W | Fan power |
| Return Fan | 5,850 W | Cooling power |
| Net Power | 13,200 W | Total cooling power |
| Power Factor | 0.81 | Electrical efficiency |
| Cooling Capacity at -30°C (return temperature): | ||
| Evaporator Fan | 550 W | Fan power |
| Return Fan | 8,250 W | Cooling power |
| Net Power | 16,300 W | Total cooling power |
| Power Factor | 0.84 | Electrical efficiency |
| Pressure Parameters: | ||
| High Pressure (R-23) | 30 bar | Operating pressure |
| High Pressure (R-134a) | 24.1 bar | Operating pressure |
| Low Pressure (R-23) | 2-3 bar | Operating pressure range |
| Low Pressure (R-134a) | 1 bar | Operating pressure |
| Test Results: | ||
| Lowest Achievable Temperature (pull-down test) | -71.7°C | Return sensor in ambient environment, 38°C |
| Container Heat Leakage | U = 35.23 W/°K | Measured on test container |
| Adjustable Temperature Range | -65°C to -10°C | MP3000 Controller |
| Control Accuracy | ±1°C | Lifetime accuracy |
| Ambient Temperature Operating Range | -30°C to 50°C | Full unit functionality |
| Maximum Noise Level | ≤ 80 dB(A) | 250 Hz band, 1.5 m distance, 1.2 m above ground, 50 Hz |
8. International Standards and Certifications
The SuperFreezer unit is fully certified according to the strictest international standards and regulations:
- ISO 1496-2: Specification for refrigeration units in transport containers
- AHRI 1110-69: Test method for evaluation of refrigeration equipment
- ATP (Accord on the International Carriage of Perishable Foodstuffs): International agreement for the transport of perishable food
- TIR (Customs Convention on the International Transport of Goods under Cover of TIR Carnets): International customs regulations for containers
- USDA (United States Department of Agriculture): American agricultural requirements for refrigeration units
- CE: European conformity certification with safety and health regulations
- Pharma GDP (Good Distribution Practice): Good distribution practice for pharmaceutical products
- ATO (Sprenger Institute): Certification of independent testing institute
- American Bureau of Shipping, Lloyds, Bureau Veritas: Classification societies for maritime transport
- PED Directive 746: Directive on pressure equipment
9. Special Features and Additional Equipment
Auto PTI (Performance Test Inspection): The unit contains three automated tests built into the microprocessor:
- Test 1 (Functional Test): Progressively energizes the compressor, fan motors and heating elements, tests energy consumption and compares it with the calculated value. It also tests the controller, temperature sensors and all contactors.
- Test 2 (PTI Test): Automatically tests cooling capacity at -60°C and defrost operations. Tests the controller, contactors, temperature sensors and performs high-pressure testing.
- Test 3 (Manual Functional Test): Allows switching of individual components to check energy consumption and relevant power.
Additional Features:
- Hinged and removable evaporator doors with quick-release stainless steel locks for easy access
- Sequential component startup to minimize peak current
- Random time delay on first startup to minimize peak current
- Safety straps and handle integrated into heater access doors
- Energy-efficient on-demand defrosting system
- Tinned and numbered wire conductors according to UL1647
- Lightweight composite fans for condenser and evaporator
- Minimal depth of only 420 mm from rear flange
- Manually controlled commercial by-pass mode for special operations
- Quick connectors R-134a on suction, discharge and receiver
- 12 V battery (1.9 A) for backup during power failure
- Two Z-profiles on rear wall for additional rigidity
- REFCON remote monitoring system (optional) with transmission via power cable according to ISO 10368
10. Conclusion: Technical Excellence for Critical Applications
Thermo King SuperFreezer CRR-40DF represents the pinnacle of technological development in the field of ultra-low temperature refrigeration equipment. The cascade cooling system with two independent circuits (R-134a and R-23) enables unprecedented capability to achieve and maintain temperatures down to -71.7°C with accuracy of ±1°C. The unit is equipped with an advanced MP3000 microprocessor controller with integrated data logger, which records temperature data for up to 625 days and enables remote monitoring via the REFCON system.
The unit’s design solution – including corrosion-resistant aluminum construction, fire-resistant polyurethane insulation and a comprehensive safety system – ensures reliability even in the most demanding conditions of maritime transport. The unit meets all relevant international standards (ISO 1496-2, AHRI, ATP, USDA, CE, Pharma GDP) and is certified by recognized classification societies (ABS, Lloyds, Bureau Veritas).
SuperFreezer is an ideal solution for the pharmaceutical industry (vaccines, API, biological materials), biotechnology applications (blood plasma, tissue cultures), food industry (seafood, food ingredients) and special chemical products that require extreme cold and maximum temperature control precision. The combination of excellent technical specifications, reliability and compliance with the strictest international standards makes SuperFreezer the first choice for the transport of the most valuable and sensitive cargo in the world.
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