Julabo F81-HL Ultra-Low Temperature Heating and Cooling Circulating Bath

Overview

The Julabo F81-HL is an ultra-low temperature heating and cooling circulating bath engineered for high-precision thermal control in demanding laboratory and industrial applications. Designed around a dual-stage vapor-compression refrigeration system—utilizing R404A in the primary stage and R23 in the secondary stage—the F81-HL achieves stable operation down to −81 °C without cryogenic fluids or liquid nitrogen dependency. Its thermodynamic architecture integrates intelligent cascade control (ICC), enabling dynamic load adaptation across the full −81 °C to +100 °C range. Unlike single-stage systems, this configuration maintains consistent refrigeration capacity at extreme sub-zero setpoints while minimizing thermal overshoot and compressor cycling. The unit serves as both a self-contained temperature-controlled bath and a closed-loop external circulation source, supporting jacketed reactors, calorimeters, spectroscopic cells, and material testing fixtures requiring accurate, reproducible thermal environments.

Key Features

• Dual-stage refrigeration system: Optimized for ultra-low temperatures; R404A (GWP 3922) and R23 (GWP 14800) stages operate in series to sustain −81 °C with <0.07 kW refrigeration output at that point.
• Intelligent Cascade Control (ICC): Self-tuning algorithm continuously adjusts PID parameters based on real-time thermal load, ambient conditions, and fluid viscosity—enhancing stability to ±0.02 °C at any setpoint.
• ATC3 three-point calibration: Enables traceable temperature verification using external Pt100 sensors at three independent points (e.g., −40 °C, 0 °C, +60 °C), supporting ISO/IEC 17025-compliant calibration workflows.
• SmartPump™ variable-pressure circulation: Dynamically modulates pump motor torque to maintain constant flow (22–26 L/min) and pressure (0.4–0.7 bar) despite viscosity changes induced by temperature shifts or fluid aging.
• VFD + backlit LCD dual-display interface: Simultaneously shows bath temperature, external sensor reading, setpoint, pump status, and alarm history; waterproof membrane keypad ensures reliable operation in humid or splash-prone labs.
• Integrated safety architecture: Includes low-level detection, overtemperature cutoff (mechanical rotary dial + digital threshold), condensate management via removable air grille, and frost-inhibiting thermal insulation layer for cabinet integrity below −60 °C.

Sample Compatibility & Compliance

The F81-HL accommodates standard silicone oil (e.g., DC200), water-glycol mixtures, and low-viscosity heat transfer fluids compatible with stainless steel 316 wetted parts and fluoropolymer seals. Its DIN 12876-1 Class III (FL) classification certifies suitability for flammable liquids (flash point <60 °C) when used with appropriate ventilation and grounding protocols. All electrical and thermal safety functions conform to IEC 61010-1:2010 and EN 61326-1:2013 (EMC). Optional RS485 and Profibus interfaces support integration into automated GLP/GMP environments where audit trails and user-access controls are required per FDA 21 CFR Part 11.

Software & Data Management

Standard RS232 serial communication enables direct connection to Windows-based PCs running Julabo’s LabView-compatible software suite or third-party SCADA platforms. Data logging includes timestamped bath temperature, external Pt100 input, pump speed, compressor status, and alarm events—exportable in CSV format. The built-in 6×60-step programmable controller supports ramp-hold profiles for accelerated stability testing (e.g., thermal cycling per ASTM E1545 or IEC 60068-2-14). Optional analog I/O module provides 0–10 V or 4–20 mA outputs for interfacing with PLCs or centralized HVAC systems.

Applications

• Low-temperature reaction kinetics studies in synthetic organic chemistry
• Cryogenic calibration of infrared detectors and bolometers
• Thermal validation of pharmaceutical freeze-drying cycles (lyophilization)
• Material property characterization: coefficient of thermal expansion (CTE), glass transition (Tg), and viscoelastic behavior via coupled rheometry
• Stabilization of high-resolution NMR probe temperatures during long-duration acquisitions
• Environmental stress screening (ESS) per MIL-STD-810G Method 502.6

FAQ

What is the minimum achievable temperature with standard lab ambient conditions (25 °C, 50% RH)?
The F81-HL reliably reaches −81 °C under DIN 12876-specified ambient conditions (5–40 °C, non-condensing), provided adequate ventilation and clearance (≥15 cm rear/side) for the air-cooled condenser.
Can the F81-HL be used with flammable solvents?
Yes—its DIN 12876-1 Class III (FL) rating permits use with fluids having flash points below 60 °C, contingent upon proper grounding, explosion-proof ancillary equipment, and adherence to local hazardous area classifications.
Is external temperature control possible without modifying the bath fluid path?
Yes—the integrated Pt100 input allows direct feedback from an external process (e.g., reactor jacket), enabling precise cascade control where the F81-HL acts solely as a thermal actuator.
How does the SmartPump™ adapt to changing fluid viscosity?
Using real-time current draw and rotational feedback, the pump controller modulates voltage to sustain target flow rate and pressure—critical when operating across >100-fold viscosity changes (e.g., silicone oil from 25 °C to −70 °C).
Does the unit support 21 CFR Part 11 compliance for regulated labs?
While the base unit provides electronic audit logs and user-accessible data export, full Part 11 compliance requires optional software licensing and networked deployment with role-based authentication, electronic signatures, and secure database archiving—available through Julabo’s validated LabControl Suite.