Great Wall ZT-20-200-40H Closed-Loop Refrigerated & Heated Circulator

Overview

The Great Wall ZT-20-200-40H is an integrated, air-cooled closed-loop refrigerated and heated circulator engineered for precise, dynamic temperature control across demanding laboratory and pilot-scale process applications. It operates on a dual-mode thermodynamic architecture—combining independent refrigeration, heating, and pre-cooling circuits—enabling seamless bidirectional thermal regulation without system interruption. Unlike open-bath chillers or single-function heaters, this unit maintains full fluid integrity within a hermetically sealed circulation loop, eliminating evaporation losses at elevated temperatures (>150 °C) and minimizing moisture ingress or condensation risks during sub-zero operation (down to −40 °C). Its design conforms to fundamental requirements of ISO/IEC 17025-compliant calibration environments and supports GLP/GMP-aligned operational traceability when paired with validated software protocols.

Key Features

• Triple-circuit thermal management: Independent refrigeration, electric heating, and pre-cooling subsystems allow concurrent or isolated operation—critical for ramp-hold-cool sequences in reaction calorimetry or polymerization studies.
• Air-cooled condensing system with brazed-plate heat exchanger: Delivers high thermal efficiency in space-constrained labs; eliminates dependency on municipal water supply and associated scaling/fouling risks.
• Magnetically coupled circulation pump: Ensures zero fluid leakage across the full operating range (−40 °C to 200 °C), essential for handling synthetic heat transfer fluids (e.g., silicone oils, glycol/water blends) under vacuum or inert atmosphere conditions.
• Advanced PID + fuzzy logic temperature control algorithm: Achieves ±0.5 °C stability at setpoint, with programmable ramp rates (0.1–10 °C/min) and hold accuracy verified per ASTM E2251-22 Annex A1.
• 5.7-inch bilingual (English/Chinese) TFT touchscreen interface: Supports both fixed-point and multi-segment programmable control (120 programs × 100 segments), real-time graphical plotting of bath and external load temperatures, and configurable alarm thresholds.
• Comprehensive safety architecture: Includes level-sensing float switch, overtemperature cutoff (hardware + software redundant), phase-loss detection, earth-leakage protection (30 mA), and automatic shutdown on flow interruption or pressure anomaly.

Sample Compatibility & Compliance

The ZT-20-200-40H is compatible with a broad spectrum of heat transfer media—including water, 50/50 ethylene glycol/water, silicone oils (e.g., DC200 series), and specialized synthetic thermal fluids—provided viscosity remains within pump operational limits (< 50 cSt at minimum operating temperature). Its sealed-loop construction meets ASTM D1310-20 requirements for fluid containment integrity during thermal cycling. While not intrinsically rated for hazardous area use (ATEX/IECEx), it complies with IEC 61000-6-3 (EMC emissions) and IEC 61000-6-2 (immunity), and its electrical safety design adheres to IEC 61010-1:2010 for laboratory equipment. For regulated environments, optional audit-trail-enabled firmware supports 21 CFR Part 11-compliant electronic records when integrated with validated LIMS or SCADA platforms.

Software & Data Management

The embedded controller logs timestamped temperature, flow, pressure, and fault events internally (≥30 days at 1-min intervals). Data export is supported via USB mass storage or RS485 Modbus RTU protocol (register map provided in technical manual). Optional Ethernet module enables remote monitoring through standard SNMP or HTTP-based APIs, facilitating integration into centralized lab infrastructure management systems. All programmable profiles are stored with user-defined metadata (operator ID, experiment ID, version stamp) and support checksum verification to prevent unauthorized modification. Firmware updates are performed via signed binary packages to ensure cryptographic integrity.

Applications

• Temperature control of jacketed glass reactors (single-, double-, and triple-layer) in pharmaceutical synthesis and fine chemical development.
• Thermal conditioning of material testing fixtures (e.g., tensile testers, rheometers, DSC autosamplers) requiring stable thermal baselines or controlled ramp profiles.
• Process simulation for freeze-drying cycle development, including shelf temperature mapping and condenser thermal load balancing.
• Calibration of temperature-sensitive sensors (RTDs, thermocouples, IR cameras) across extended ranges using NIST-traceable reference probes.
• Supporting vacuum chamber thermal management in thin-film deposition or semiconductor packaging R&D, where outgassing from open baths must be avoided.
• Dynamic thermal stress testing of automotive components (e.g., battery modules, power electronics) under ISO 16750-4 environmental profiles.

FAQ

What heat transfer fluids are recommended for operation at 200 °C?
Silicone-based thermal oils (e.g., Dow Corning DC-200 Fluid 50 cSt) or polyalkylene glycol (PAG) formulations with flash points >250 °C and thermal stability ratings exceeding 200 °C for ≥1,000 hours are suitable. Water-based fluids are strictly prohibited above 100 °C.
Can the unit maintain ±0.5 °C stability while circulating at 30 L/min through a 20-meter external loop?
Yes—stability specification is validated under worst-case hydraulic load (30 L/min, ΔP ≤ 1 bar, ambient 25 °C). Actual performance depends on external loop insulation quality and heat exchange surface area.
Is remote start/stop and setpoint adjustment possible via digital interface?
Yes—RS485 Modbus RTU allows full read/write access to all operational parameters, including setpoint, ramp rate, program selection, and status flags. Ethernet option adds web-based HMI and SNMP trap support.
Does the system comply with FDA 21 CFR Part 11 for electronic records?
The base unit does not include Part 11 features; however, optional firmware upgrade (ZT-20-200-40H-21CFR) provides electronic signatures, audit trails, and role-based access control—validated per IQ/OQ protocols upon installation.
What maintenance intervals are recommended for long-term reliability?
Compressor oil and refrigerant charge require verification every 24 months; heat exchanger fins should be cleaned quarterly in dusty environments; pump bearings are lifetime-lubricated but inspected annually during preventive maintenance.