Great Wall DLSB-5/20 Cryogenic Constant-Temperature Circulator for Rotary Evaporator Cooling

Overview

The Great Wall DLSB-5/20 Cryogenic Constant-Temperature Circulator is a precision-engineered recirculating chiller designed specifically to provide stable, low-temperature coolant supply for rotary evaporators and other vacuum-based or exothermic laboratory systems. Operating on a closed-loop mechanical refrigeration principle, the unit employs a hermetically sealed compressor, high-efficiency condenser, and optimized expansion valve system to achieve and maintain a setpoint temperature of −20 °C in its 5-liter reservoir. Its primary function is to absorb heat from external equipment—such as rotary evaporator condensers, cold traps, or reaction jackets—and return thermally stabilized fluid at consistent flow and pressure. This enables efficient solvent condensation during rotary evaporation, improves recovery yields, and prevents vapor breakthrough under reduced pressure. The DLSB-5/20 is not a standalone cryostat but a dedicated circulation platform engineered for thermal stability, long-term reliability, and seamless integration into multi-instrument workflows common in synthetic chemistry, natural product isolation, and pharmaceutical process development.

Key Features

• Hermetically sealed, internationally sourced compressor ensuring extended service life and minimal maintenance intervals
• Microprocessor-controlled digital thermostat with ±0.3 °C temperature stability and real-time LED readout
• Corrosion-resistant internal wetted parts—including stainless-steel reservoir, fluoropolymer-coated pump head, and EPDM seals—designed to minimize contamination of heat-transfer fluids (e.g., ethanol/water or ethylene glycol mixtures)
• Adjustable centrifugal circulation pump delivering up to 20 L/min at pressures sufficient to overcome typical system backpressure (≤0.3 MPa)
• Integrated over-temperature, low-level, and phase-loss protection circuits compliant with IEC 61000-6-2 EMC standards
• Front-panel accessible fluid fill port, drain valve, and quick-connect fittings compatible with standard 1/4″–3/8″ tubing

Sample Compatibility & Compliance

The DLSB-5/20 circulator is compatible with all major rotary evaporator platforms (including Buchi, IKA, Heidolph, and LabTech) via standard hose barb or threaded connections. It supports use with common low-freezing-point heat-transfer media, including aqueous ethylene glycol (up to 60 wt%), ethanol/water blends, and silicone oils—subject to viscosity limits (<50 cSt at operating temperature). The unit meets structural and electrical safety requirements per GB 4793.1–2007 (equivalent to IEC 61010-1) for laboratory equipment. While not certified to UL or CE for direct export without regional adaptation, its architecture aligns with foundational design principles required for FDA 21 CFR Part 11–aligned environments when paired with validated SOPs and audit-trail-capable software interfaces. It is routinely deployed in laboratories adhering to ISO/IEC 17025 quality management systems for method validation involving temperature-sensitive distillation steps.

Software & Data Management

The DLSB-5/20 operates via embedded firmware with no proprietary software dependency. Temperature setpoint, actual bath temperature, and operational status (compressor/pump on/off) are displayed locally. For integration into centralized lab data systems, optional RS485 Modbus RTU output (available on DLSB-5/20-Plus variants) enables connection to SCADA, LIMS, or ELN platforms for time-stamped logging of thermal performance. When used in GLP or GMP contexts, users may configure external data loggers (e.g., Omega OM-DAQPRO-5300) to record temperature deviation history for audit readiness. No cloud connectivity or remote control functionality is built-in—consistent with security-first instrumentation practices in regulated research settings.

Applications

• Cooling condenser coils of rotary evaporators during low-boiling-point solvent removal (e.g., dichloromethane, ether, pentane) at ≤10 mbar
• Thermal stabilization of cold traps in vacuum manifold systems for solvent capture and moisture suppression
• Temperature-controlled jacketing of glass reactors during cryogenic Grignard or organolithium additions
• Supporting chilled feed streams for preparative HPLC fraction collectors or inline UV detectors requiring thermal drift mitigation
• Secondary cooling loop for laser-based analytical instruments (e.g., Raman spectrometers) where primary chillers are unavailable
• Long-duration incubation support for enzymatic assays requiring sub-ambient thermal control (−10 °C to −20 °C)

FAQ

What is the minimum achievable temperature for the DLSB-5/20 model?

The DLSB-5/20 is rated for a stable setpoint of −20 °C under standard ambient conditions (25 °C, 50% RH) with recommended coolant mixture (30% ethylene glycol / 70% deionized water). Actual performance may vary slightly depending on ambient load, insulation of external lines, and flow resistance.

Can this unit be used with organic solvents directly in the reservoir?

No. The reservoir must be filled only with water-miscible, non-corrosive heat-transfer fluids approved by Great Wall (e.g., inhibited ethylene glycol solutions or ethanol/water blends). Pure acetone, THF, or chlorinated solvents will degrade seals and compromise pump integrity.

Is the pump flow rate adjustable?

Yes. A calibrated flow control valve allows manual adjustment between ~5 L/min and 20 L/min, enabling optimization for low-backpressure rotary evaporators or higher-resistance external loops.

Does the DLSB-5/20 include overload or dry-run protection?

Yes. Integrated level sensors automatically disable the pump if reservoir volume falls below 1.5 L, and thermal cutoffs interrupt compressor operation if internal coil temperature exceeds safe thresholds.

What maintenance intervals are recommended for routine operation?

Compressor oil and refrigerant charge require no scheduled servicing under normal use. Annual inspection of coolant pH (target 7.0–8.5), seal integrity, and filter screen cleaning is advised. Replace reservoir fluid every 12 months or after contamination events.