A low-temperature constant temperature reaction bath is a device that combines a refrigeration system with a temperature control system to achieve precise temperature control. It is widely used in scientific research and industrial scenarios such as chemical synthesis, material preparation, and biological experiments that require low-temperature or constant temperature environments. Its core function is to provide stable and uniform low-temperature or constant temperature conditions for the reaction system. The following elaborates on the usage details from the aspects of equipment composition, operation process, precautions, and maintenance points.

1、 Equipment composition and working principle

1. Core components

-Refrigeration system: Typically, compressor refrigeration technology (such as variable frequency compressors) is used to achieve heat exchange through a condenser, evaporator, and expansion valve.

-Circulating pump: drives the thermal conductive medium (such as ethylene glycol aqueous solution, silicone oil, etc.) to circulate in the system, ensuring uniform temperature distribution.

-Temperature controller: PID intelligent temperature control system, capable of setting target temperature and real-time monitoring, with an accuracy of ± 0.1 ℃.

-Reaction tank: A transparent or metal tank body that accommodates a reaction vessel, made of materials that are resistant to low temperatures (such as stainless steel or antifreeze glass).

2. Working principle

The refrigerant absorbs heat and evaporates in the evaporator, taking away heat; After compressing the gaseous refrigerant, the compressor releases heat in the condenser; The circulation pump transports the low-temperature medium to the reaction tank and maintains the system temperature through heat exchange.

2、 Preparation before use

1. Cleaning and Inspection

-Clean up the residual medium or impurities in the reaction tank to avoid blocking the circulation pipeline.

-Check if the power cord, plug, and grounding are in good condition, and confirm that there is no risk of leakage.

-Verify that the temperature sensor probe is clean and securely fixed to avoid poor contact causing temperature control failure.

2. Medium selection and filling

-Media type:

-Water based media (such as ethylene glycol aqueous solution): suitable for -20 ℃~room temperature, low cost but easy to freeze.

-Silicone oil: suitable for a wide temperature range (-50 ℃~200 ℃), but high viscosity requires regular replacement.

-Alcohol solution: Highly volatile, requires frequent fluid replacement, suitable for short-term low-temperature experiments.

-Filling amount: The medium needs to cover the circulation pipeline, usually adding 2/3~3/4 of the reaction tank volume to avoid overflow caused by excessive amount.

3. Environmental confirmation

-Place on a well ventilated countertop, away from flammable materials and heat sources.

-Ensure that there is no obstruction around the device for easy heat dissipation and operation.

3、 Operation process

1. Startup and parameter settings

-Connect the power, turn on the device switch, and wait for the control panel to initialize.

-Set target temperature: Enter numerical values according to experimental requirements (such as -10 ℃), taking care not to exceed the nominal range of the equipment (such as -40 ℃~100 ℃).

-Adjust the stirring speed (if any): Medium speed (such as 300-500rpm) can promote the flow of the medium and avoid local supercooling or overheating.

2. Operation monitoring

-Observing the temperature control curve: After the equipment is started, the temperature will gradually decrease and tend to stabilize, and you need to wait for about 10-30 minutes (depending on the temperature difference).

-Regularly check the liquid level of the medium and replenish any evaporated or leaked parts.

-Avoid frequent power on/off: Short pauses can switch to "standby" mode to extend the lifespan of the compressor.

3. Sample placement and retrieval

-Immerse the reaction vessel (such as a flask or test tube) into the medium to ensure even heating.

-Use tweezers or specialized tools to take and place samples, avoiding direct contact with low-temperature surfaces by hand.

-Long term experiments require sealing (such as rubber plugs) to prevent condensation or medium contamination of the sample.

4. Shutdown steps

-Stop the experiment in advance: Turn off the heating or cooling function, and turn off the power after the temperature naturally returns to room temperature.

-Discharge medium: If it is necessary to replace the medium, the medium should be drained first, the pipeline should be rinsed with clean water, and then new medium should be injected.

4、 Key precautions

1. Safety risk prevention and control

-Antifreeze injury: Wear low-temperature protective gloves during operation to avoid direct skin contact with metal parts below -20 ℃.

-Explosion prevention: Glass containers should be checked for cracks to avoid sudden cooling and heating that may cause explosions.

-Fireproof flower: Keep the equipment away from open flames. In case of refrigerant leakage, immediately cut off the power and ventilate.

2. Parameter limitations

-Prohibit setting temperatures beyond the specified range (such as setting the device to -30 ℃, not to -40 ℃).

-Avoid long-term no-load operation, otherwise it may cause compressor overheating and damage.

3. Operation taboos

-Do not forcefully start the compressor when the medium is insufficient, otherwise the compressor may burn out due to lack of liquid.

-Do not directly throw high-temperature samples (such as freshly heated flasks) into the reaction tank, and pre cool them to near the tank temperature.

5、 Maintenance and upkeep

1. Daily maintenance

-Clean the reaction tank after the experiment, rinse it with clean water and dry it to prevent residual medium from corroding the tank body.

-Regularly clean the dust screen (located at the inlet of the compressor) to avoid dust blocking and affecting heat dissipation.

2. Long term discontinuation treatment

-Drain the medium and inject a small amount of clean water. Power on for 1-2 hours per month to prevent compressor aging.

-Store in a dry environment and cover with dust-proof cloth.

3. Troubleshooting

-Unstable temperature control: Check if the sensor probe is loose or if the medium flow is insufficient.

-Low refrigeration efficiency: It may be due to excessive dust accumulation in the condenser, which requires cleaning or refrigerant replenishment.

-Abnormal noise or shaking: Check if the screws of the circulation pump are loose or if there are bubbles in the pipeline.