The following are key considerations and purchasing guidelines for matching temperature control equipment:
1. Temperature range:
It must fully cover the minimum and maximum temperatures required by the process.
(1) Refrigeration lower limit: What is the minimum temperature required by the process? (e.g. -30°C, -50°C, -80°C). The minimum temperature of the equipment should be lower than the process requirements (reserve a margin).
(2) Heating upper limit: What is the maximum temperature required by the process? (e.g. 150°C, 200°C, 250°C). The maximum temperature of the equipment should be higher than the process requirements.
Note: The tolerance range of glass reactors is usually -80°C to +200°C, but drastic temperature changes (ΔT < 80°C) should be avoided. The actual selection is based on the process requirements.
2. Temperature control accuracy and stability:
(1) Accuracy: The accuracy requirements of the process for temperature control (e.g. ±0.5°C, ±1°C, ±2°C). Synthesis reactions and crystallization usually require within ±1°C.
(2) Stability: The ability to maintain the set temperature for a long time is as important as accuracy. Choose equipment with excellent PID control algorithms.
3. Heat transfer medium:
Select according to temperature range:
(1) > 0°C: Water (needs to be antibacterial), deionized water, purified water (pharmaceutical).
(2) -40°C to +200°C: Silicone oil (most commonly used, good thermal stability, non-flammable, moderate viscosity). Avoid using low-quality oils with low flash points or easy to decompose at high temperatures.
(3) -50°C to -80°C: Ethylene glycol aqueous solution (low cost, high viscosity, low efficiency), special low-temperature synthetic fluid (higher efficiency, high cost).
(4) > 200°C: High-temperature heat transfer oil (high flash point, excellent thermal stability).
Key requirements: low viscosity (especially good low-temperature fluidity), high specific heat capacity, high thermal conductivity, chemical inertness, good thermal stability, non-toxic/low toxicity, non-flammable.
4. Circulation pump performance:
(1) Flow rate: Sufficient circulation flow rate is the key to ensuring heat exchange efficiency. It needs to meet the resistance requirements of the jacket/reactor wall. Generally, a flow rate range of 15-40 L/min is recommended for most small and medium-sized glass reactors (1L-50L). Insufficient flow rate is a common cause of temperature control failure!
(2) Pressure (head): The ability to overcome the resistance of pipes, valves and jackets. Ensure that the maximum head of the pump is greater than the total resistance of the system.
(3) Material: The pump head and seal must be resistant to media and temperature (316L stainless steel, PTFE/FFKM seal).
(4) Type: Magnetic drive pump (leak-free) is the first choice.
5. Interface and connection:
(1) Interface size: The circulation inlet and outlet sizes (such as G1/2", G3/4", G1") must match the reactor jacket interface. If they do not match, a conversion joint is required.
(2) Pipe material: Heat-resistant and medium-resistant (commonly used silicone tubes, PTFE tubes, metal hoses). The length should be as short as possible, and good insulation should be done to reduce heat loss/cooling loss.
6. Safety protection:
(1) Over-temperature/low-temperature protection: Independent multiple hardware protection (temperature limiter).
(2) Low liquid level protection: Prevent dry-burning heaters or pumps from idling.
(3) Pressure/pressure relief device: Closed systems require safety valves/expansion tanks.
(4) Leakage protection: Standard.
(5) Explosion-proof requirements: If handling flammable and explosive solvents, the entire machine or key components must meet the corresponding explosion-proof level (such as Ex d IIB T4 Gb).
7. Control system and functions:
(1) User interface: Clear and easy to operate, displaying set temperature, actual temperature, pump speed, alarm information, etc.
(2) Program control: If multiple heating/cooling/holding programs are required, choose a programmable model.
(3) Data recording: Record temperature curves and events, and support export (USB, RS232, Ethernet). Comply with GMP data integrity requirements (if applicable).
(4) Communication: Optional Modbus, Profibus and other interfaces can be integrated into the host computer system.
8. Brand and service:
(1) Choose a brand with a good reputation in the field of laboratory temperature control equipment.
(2) Consider after-sales service response speed, spare parts supply and technical support capabilities.