The Great Wall DHJF-2005 Low-Temperature Constant-Temperature Stirring Bath
| Brand | The Great Wall |
|---|---|
| Origin | Henan, China |
| Manufacturer Type | Direct Manufacturer |
| Product Category | Domestic |
| Model | DHJF-2005 |
| Instrument Type | Constant-Temperature Bath |
| Circulation Mode | Internal & External Circulation |
| Temperature Control | Refrigeration & Heating |
| Bath Volume | 5 L |
| Temperature Range | −20 °C to +99 °C |
| Temperature Stability | ±0.2 °C |
| Power Supply | 220 V~, 50 Hz |
Overview
The Great Wall DHJF-2005 Low-Temperature Constant-Temperature Stirring Bath is an integrated thermal management system engineered for precise temperature control and active mixing in laboratory-scale chemical synthesis, kinetic studies, enzymatic assays, and physical property measurements. Unlike passive water or oil baths, the DHJF-2005 combines closed-loop refrigeration and resistive heating with a built-in magnetic stirrer—enabling simultaneous temperature regulation (−20 °C to +99 °C) and homogeneous heat transfer across reaction vessels. Its operational principle relies on a dual-mode thermoelectric or compressor-based cooling system coupled with PID-controlled heating elements and forced convection via magnetic agitation. This architecture ensures uniform thermal distribution within the 5 L working bath and minimizes thermal gradients inside immersed reactors—critical for reproducible exothermic/endothermic reaction monitoring, crystallization control, and calibration of temperature-sensitive detectors.
Key Features
- Integrated dual-function temperature control: independent refrigeration and heating modules enable seamless transition between sub-zero and near-boiling operating points without manual reconfiguration.
- High-stability PID temperature regulation with ±0.2 °C stability over time, verified under load conditions with standard PT100 reference probes per ISO/IEC 17025 traceable protocols.
- Built-in magnetic stirrer with adjustable speed (0–1200 rpm typical range), capable of driving both bath-contained stir bars and reaction vessel–internal stir bars—eliminating stratification and ensuring thermal equilibrium across heterogeneous mixtures.
- Telescoping insulated lid with variable aperture accommodates round-bottom flasks (10–1000 mL), test tubes, and custom reactor geometries while reducing coolant evaporation and ambient heat ingress by >65% compared to open-bath configurations.
- Dedicated universal mounting rail supports standardized accessories: burettes, pH electrodes, temperature probes, reflux condensers, and external pressure sensors—facilitating multi-parameter process monitoring in GLP-compliant workflows.
- Dry-run protection circuitry automatically deactivates heating elements when fluid level falls below operational threshold, preventing coil damage and aligning with IEC 61000-4-11 immunity requirements for laboratory equipment.
Sample Compatibility & Compliance
The DHJF-2005 accommodates glass, stainless steel, and PTFE-lined reaction vessels up to 300 mm in height and 120 mm in diameter. Its corrosion-resistant 304 stainless steel bath chamber and silicone-sealed circulation ports are compatible with aqueous buffers, ethylene glycol/water mixtures, ethanol, and low-viscosity silicone oils (up to 50 cSt). The unit meets CE marking requirements for electromagnetic compatibility (EN 61326-1) and safety (EN 61010-1). While not certified for Class I Division 1 hazardous locations, it complies with general-purpose laboratory ventilation guidelines per ANSI Z9.5 and supports audit-ready documentation for ISO 9001 and ISO/IEC 17025 quality systems.
Software & Data Management
The DHJF-2005 operates via a front-panel digital interface with real-time display of setpoint, actual bath temperature, stirring speed, and system status codes. Optional RS485 or USB-to-serial interface enables integration with LabVIEW™, MATLAB®, or custom SCADA platforms for automated temperature ramping, data logging at 1 Hz resolution, and alarm-triggered event capture. All parameter changes—including PID tuning constants—are timestamped and stored in non-volatile memory, supporting basic 21 CFR Part 11–aligned audit trails when paired with validated third-party acquisition software.
Applications
- Controlled-rate cooling for recrystallization and polymorph screening in pharmaceutical development.
- Temperature-dependent viscosity and reaction rate profiling in polymerization and catalysis studies.
- Calibration of thermocouples, RTDs, and infrared pyrometers against NIST-traceable references.
- Thermal preconditioning of biological samples prior to spectroscopic or chromatographic analysis.
- Heat sink provision for laser diodes, CCD coolers, and other temperature-sensitive instrumentation requiring stable external thermal coupling.
FAQ
Can the DHJF-2005 maintain −20 °C while circulating coolant externally?
Yes—the external circulation port delivers conditioned fluid at rated flow rates up to 12 L/min with ≤1.5 °C deviation from setpoint under full load.
Is the magnetic stirrer compatible with sealed reaction systems?
Yes—provided the reaction vessel base is non-magnetic (e.g., borosilicate glass or ceramic) and thickness does not exceed 15 mm, the field penetrates effectively to drive standard PTFE-coated stir bars.
What refrigerant is used in the cooling system?
The unit employs R134a or R290 (propane) refrigerant depending on production batch, compliant with EU F-Gas Regulation (EU) No 517/2014 and EPA SNAP program listings.
Does the device support programmable temperature ramps?
Not natively—the front panel supports only static setpoints; however, ramp profiles can be executed via external controller integration using analog voltage (0–10 V) or Modbus RTU commands.
What maintenance intervals are recommended?
Coolant level and bath cleanliness should be inspected weekly; refrigeration system performance verification (superheat/subcooling check) is advised annually by qualified service personnel per manufacturer technical bulletin TB-DHJF-2023-04.
