ZT-20-200-80H Closed-Loop Refrigerated & Heated Circulator by The Great Wall

Overview

The ZT-20-200-80H Closed-Loop Refrigerated & Heated Circulator is an engineered thermal management system designed for precise, bidirectional temperature control of external process equipment—including jacketed reactors, rotary evaporators, calorimeters, and analytical instrumentation. Operating on a dual-refrigerant cascade architecture (R404A for medium-low temperature stages and R23 for ultra-low sub-zero operation), the unit delivers stable, continuous heat transfer across a wide operational envelope from −80 °C to +200 °C. Its closed-loop design prevents fluid evaporation, oxidation, and contamination, ensuring long-term thermal fluid integrity and consistent heat transfer coefficients. The circulator maintains reactor temperature stability within ±0.5 °C under dynamic load conditions—critical for exothermic/endothermic reaction control, crystallization profiling, and kinetic studies where thermal drift compromises reproducibility.

Key Features

• Integrated cascade refrigeration system enabling uninterrupted operation down to −78 °C while sustaining heating capability up to +200 °C
• SUS304 stainless steel reservoir, fluid pathways, and valve train—resistant to corrosion from common heat transfer fluids (e.g., silicone oils, ethylene glycol/water blends)
• High-flow, low-pulsation circulation pump (30 L/min at 1.5 bar max pressure) optimized for low-pressure-drop external loops
• Tactile LCD interface with real-time display of setpoint, actual bath temperature, outlet temperature, flow status, and fault diagnostics
• Comprehensive safety architecture: phase sequence monitoring, overcurrent cutoff, dual-stage overtemperature shutdown (bath and compressor discharge), high/low refrigerant pressure interlocks, and soft-start delay logic
• Modular design facilitates field serviceability; refrigerant circuits are segregated for independent maintenance

Sample Compatibility & Compliance

The ZT-20-200-80H is compatible with standard laboratory-scale external devices equipped with 3/4″ BSP or NPT inlet/outlet ports. Its closed-loop configuration eliminates volatile emissions, supporting compliance with ISO 14001 environmental management protocols and OSHA ventilation guidelines for indoor lab use. While not intrinsically rated, optional ATEX-compliant explosion-proof variants (ZT-20-200-80H-EX) are available for Class I, Division 1 environments handling flammable solvents. The system supports GLP/GMP workflows through configurable audit trail logging (via optional RS485/Modbus RTU interface) and meets mechanical safety requirements per IEC 61000-6-2 (immunity) and IEC 61000-6-4 (emissions). Fluid compatibility documentation—including thermal stability limits and material compatibility charts for Dow Corning PMX-200, Marlotherm SH, and Therminol VP-1—is provided upon request.

Software & Data Management

The unit operates autonomously via its embedded controller but supports external integration via RS485 serial interface (Modbus RTU protocol) for centralized monitoring in SCADA or LIMS environments. Optional PC software enables remote setpoint scheduling, ramp/soak profile programming, and time-stamped data export (CSV) of temperature, flow, and alarm events. All logged parameters include UTC timestamps and user-accessible metadata tags, satisfying traceability requirements under FDA 21 CFR Part 11 when deployed with validated electronic signature modules. No cloud connectivity is embedded; data residency remains fully on-premise unless interfaced with approved third-party middleware.

Applications

• Precise thermal control of glass-jacketed reaction vessels during Grignard, lithiation, hydrogenation, and polymerization reactions
• Condenser cooling and evaporation temperature regulation in rotary evaporation systems—especially for low-boiling-point solvents (e.g., diethyl ether, pentane)
• Calibration and thermal validation of DSC, TGA, and rheometry cells requiring extended sub-ambient stability
• Temperature cycling of bioreactor jackets during microbial fermentation or cell culture process development
• Stabilization of laser sources, interferometers, and optical benches sensitive to ambient thermal gradients

FAQ

What heat transfer fluids are recommended for operation across the full −80 °C to +200 °C range?

For optimal viscosity-temperature performance and thermal stability, we recommend using a certified low-temperature silicone oil (e.g., DC-704 or similar) below −40 °C, and high-temperature synthetic heat transfer fluids (e.g., Marlotherm SH or Therminol VP-1) above +100 °C. Mixing fluids is strictly prohibited.
Does the ZT-20-200-80H support external PID feedback control?

Yes—the unit accepts analog 0–10 V or 4–20 mA input signals via optional I/O module for cascade control configurations where reactor temperature is measured externally and fed back to modulate circulator output.
Is the system suitable for continuous unattended operation over 72 hours?

Yes, provided ambient conditions remain within specification (5–35 °C, ≤70% RH) and routine preventive maintenance intervals (compressor oil change every 6,000 operating hours, filter replacement every 12 months) are observed.
Can the reservoir volume be expanded beyond 12 L?

No—the internal reservoir is fixed at 12 L to maintain optimal refrigerant charge balance and thermal response time. External expansion tanks may be added downstream but require separate level and temperature monitoring.
What is the minimum allowable flow rate before pump protection activates?

The circulation pump triggers low-flow shutdown if detected flow falls below 5 L/min for more than 30 seconds—preventing dry-run damage and thermal runaway in blocked-loop scenarios.