Definition
Stirring thermostatic oil tank is a commonly used temperature control equipment in laboratories, which provides a uniform and stable high-temperature and constant temperature environment for samples or reaction vessels by heating the medium oil and cooperating with the stirring system. It is commonly used in experimental processes that require precise temperature control above room temperature to hundreds of degrees Celsius.
Principle
The core working principle of the stirring thermostatic oil tank is based on heat conduction and convection. The equipment is equipped with medium oil with high boiling point and good thermal stability. The heating element heats the medium oil, and the temperature sensor monitors the oil temperature in real time and feeds the signal back to the control system. The control system adjusts the heating power according to the difference between the set temperature and the measured temperature to achieve precise temperature control. At the same time, the built-in stirring device works continuously to promote the circulation of media oil in the tank, thereby eliminating temperature gradients and ensuring uniform and consistent temperature at all points in the tank.
Its temperature control process can be simplified into a closed-loop feedback system. Set the set temperature to Tset, the measured temperature is Tmeas, then the control system is designed to minimize the error e = Tset - Tmeas。 The output power P of the heater is adjusted by the proportional-integral-differential algorithm, and the relationship can be expressed as: P = f(Kp·e + Ki∫e dt + Kd·de/dt), where Kp, Ki, Kdis the control parameter.
Measurement and calibration methods
The performance evaluation of the stirring constant temperature tank mainly focuses on temperature uniformity and stability. Temperature uniformity refers to the temperature difference between spatial points in the effective working area of the tank at the same time. To measure, multiple calibrated, high-precision platinum resistance thermometers are placed in different positions in the tank and temperature readings are recorded at the same time. Temperature stability refers to the degree to which the temperature fluctuates over time at a certain point in the tank, usually by monitoring the temperature at a single point for a long time.
Calibration should be carried out with reference to relevant national or international standards, such as JJF 1030-2010 "Specification for Technical Performance Testing of Thermostatic Chambers". During the calibration process, a standard thermometer should be used to compare and correct the display temperature of the equipment to ensure the accuracy of its value transmission.
Influencing factors
The performance of the stirring thermostatic oil tank is affected by a variety of factors. The characteristics of the media oil are key factors, and its boiling point, flash point, viscosity, and thermal stability determine the safe operating temperature range and heat transfer efficiency of the equipment. Environmental conditions such as ambient temperature and ventilation will affect the heat dissipation of the equipment, thereby interfering with the temperature control accuracy. The thermal load of the controlled object, i.e., the number, material, and specific heat capacity of the sample or container placed in the tank, absorbs heat and can cause temperature fluctuations. In addition, the setting of the stirring speed directly affects the intensity of thermal convection, with too low a speed leading to a decrease in uniformity, while too high a speed may cause violent shaking of the oil surface or excessive bubbles. The heating power of the device itself, the temperature control algorithm and the accuracy of the sensor are also the basis for determining its performance.
Main application areas:
Stirring constant temperature oil tanks are widely used in scientific research and industrial testing fields that require high temperature and constant temperature environments. In materials science, it is used for thermal deflection temperature and Vicat softening point testing of polymer materials. In the petrochemical field, it is used for high-temperature viscosity determination and oxidation stability test of lubricating oil, asphalt and other products. In the electronic and electrical industry, it is used for thermal aging tests of cables and insulation materials. In addition, it is also commonly used in metrology departments to verify and calibrate temperature sensors and thermometers, as well as to provide a stable high-temperature reaction environment for chemical reactions.
Key points to consider in selection
When choosing a stirring thermostatic oil tank, it is necessary to comprehensively consider a number of technical parameters to meet the specific experimental needs. The temperature range is the primary indicator, and it is necessary to ensure that the maximum temperature of the equipment can cover the experimental requirements and leave appropriate margins. The tank volume and opening size need to be able to accommodate the labware. The temperature uniformity and stability index are directly related to the reliability of the experimental conditions, and the equipment with the corresponding performance level should be selected according to the temperature error allowed by the experiment. The type of media oil needs to be matched to the operating temperature and its safety considerations. The mixing system should provide smooth and adjustable mixing force. The user-friendliness of the control system and the program control function are also aspects to improve the efficiency of experiments. Finally, the safety protection functions of the equipment, such as overheating protection and low liquid level protection, are necessary conditions to ensure long-term safe operation.