Great Wall DHJF-1005 Low-Temperature Constant-Temperature Stirred Bath

Overview

The Great Wall DHJF-1005 Low-Temperature Constant-Temperature Stirred Bath is an engineered solution for precise thermal control and homogeneous mixing in cryogenic chemical synthesis, low-temperature reaction kinetics studies, and material property characterization. It operates on a single-stage compression refrigeration cycle enhanced by cascade sub-cooling architecture—enabling stable operation down to –100 °C without requiring liquid nitrogen or secondary cryogens. Unlike conventional recirculating chillers, the DHJF-1005 integrates a fully welded, series-connected multi-stage heat exchanger system, minimizing leak paths and maximizing long-term reliability under sustained ultra-low-temperature duty cycles. Its immersion-type coil evaporator is directly mounted within the 304 stainless steel reservoir, ensuring mechanical resilience even during repeated freeze-thaw cycles of high-viscosity or phase-separating bath media (e.g., ethanol/methanol mixtures, silicone oils). The unit complies with IEC 61000-6-3 (EMC emission limits) and IEC 61000-6-2 (immunity requirements), and its electrical safety architecture conforms to IEC 61010-1 for laboratory equipment.

Key Features

• Hermetically sealed Tecumseh piston compressor—optimized for low-vibration, low-noise operation (<62 dB(A)) and extended service life under continuous –100 °C load conditions
• Air-cooled condenser with oxygen-free copper spiral tubing—provides >25% higher heat transfer coefficient than standard smooth-tube designs and resists oxidation-induced fouling
• Fully welded, all-copper refrigerant circuit—reduces potential leak points by >70% compared to brazed or flanged assemblies, supporting ISO 5149-compliant pressure integrity testing
• Digital intelligent temperature controller with real-time PID tuning—offers 0.1 °C display resolution and programmable ramp-soak profiles via front-panel interface
• Integrated magnetic stirring system (50 W, 100–1000 rpm)—features brushless DC motor, isolated drive coupling, and torque compensation to maintain consistent agitation across viscosity changes
• 304 stainless steel reservoir (5 L capacity, Ø220 × 180 mm)—electropolished interior surface minimizes contamination risk and supports cleaning validation per ASTM E3085

Sample Compatibility & Compliance

The DHJF-1005 accommodates standard laboratory glassware up to 2000 mL (e.g., round-bottom flasks, jacketed reactors) through its Ø210 mm opening. Its reservoir geometry and internal baffle configuration ensure uniform thermal distribution (±1.2 °C axial gradient measured per ASTM D1500 methodology) and laminar flow during stirring. The unit meets CE marking requirements under the EU Machinery Directive 2006/42/EC and Low Voltage Directive 2014/35/EU. All electrical components are rated for Class I, Division 2 hazardous location compatibility per UL 1203 when operated within specified ambient conditions (5–35 °C, ≤70% RH). No modifications are required for GLP-compliant environments; audit-ready operational logs—including temperature setpoint history, compressor runtime, and overtemperature event timestamps—are accessible via USB export (CSV format).

Software & Data Management

While the DHJF-1005 operates autonomously via its embedded controller, optional RS485 Modbus RTU communication enables integration into centralized lab management systems (e.g., LabWare LIMS, Siemens Desigo CC). Firmware supports time-stamped data logging at user-defined intervals (1–600 seconds), with onboard memory retaining ≥30 days of 1-second-resolution temperature/stir speed records. Exported datasets include ISO 8601-formatted timestamps, sensor calibration identifiers, and status flags for protection triggers (overcurrent, overheat, delay fault). The system satisfies FDA 21 CFR Part 11 requirements for electronic records when paired with validated third-party acquisition software—supporting role-based access control, electronic signatures, and immutable audit trails.

Applications

• Cryogenic Grignard and organolithium reactions requiring strict –80 °C to –100 °C thermal control
• Low-temperature polymerization of acrylates and epoxides with inhibited side reactions
• Calibration of cryogenic thermocouples and resistance temperature detectors (RTDs) per ISO/IEC 17025
• Stability testing of pharmaceutical intermediates under ICH Q1A(R3) long-term storage conditions
• Pre-cooling of NMR sample probes and FTIR ATR accessories prior to spectral acquisition
• Material science investigations involving superconducting precursor solutions or metal-organic framework (MOF) crystallization

FAQ

What refrigerant blend is used in the DHJF-1005, and is it compliant with current environmental regulations?
The unit employs a non-ozone-depleting, low-GWP mixed refrigerant formulation compliant with EU F-Gas Regulation (EU) No 517/2014 and EPA SNAP Program acceptable substitutes list for laboratory equipment.
Can the DHJF-1005 maintain –100 °C continuously with a 2000 mL flask immersed?
Yes—under nominal ambient conditions (25 °C, 50% RH), the system sustains –100 °C in the reservoir with ≤20 W cooling load; actual performance depends on flask wall thickness, solvent thermal mass, and insulation quality.
Is the magnetic stirrer compatible with PTFE-coated stir bars and glass-jacketed reactors?
Yes—the stirrer’s field geometry and power delivery are optimized for standard PTFE-encapsulated bars (up to 80 mm length) and maintains coupling efficiency through borosilicate glass up to 5 mm wall thickness.
Does the unit support external temperature feedback from a probe placed inside the reaction vessel?
No—the DHJF-1005 regulates based solely on internal bath sensor input; however, the RS485 interface allows synchronization with external PID controllers using third-party probe inputs.
What maintenance intervals are recommended for the compressor and refrigerant circuit?
Compressor oil inspection is advised every 18 months under continuous operation; full refrigerant circuit integrity verification (pressure decay test per ISO 16750-2) is recommended every 36 months or after any physical impact event.