Definition
Refrigeration and stirring thermostatic tank is a commonly used equipment in laboratories that provides a stable and uniform temperature environment for samples or reaction systems by integrating refrigeration, heating and stirring functions. It typically consists of a tank that houses the working medium, a temperature control system, a stirring unit, and a refrigeration module that can maintain a set temperature over a wide temperature range, such as -30°C to 100°C, which varies depending on the model. This equipment is widely used in materials testing, chemical synthesis, biological culture, and physical properties research, and is one of the basic tools for laboratories to conduct precise temperature control experiments.
Principle
The working principle of the refrigeration stirring thermostat is based on thermodynamic equilibrium and fluid dynamics. The core is to achieve temperature stability through a closed-loop control system: first, a temperature sensor (such as a platinum resistor) monitors the temperature of the medium in the tank in real time and feeds back the signal to the controller; The controller compares the set value with the actual value and adjusts the power output of the refrigeration or heating unit through a proportional-integral-differential algorithm. Refrigeration modules usually use compressor cooling or Peltier effect to reduce temperature; The heating unit provides heat through a resistive wire or film heater. At the same time, the built-in agitator (such as a propeller or magnetic agitator) continuously agitates the working medium (commonly deionized water, glycol solution, or silicone oil) to promote even heat distribution and reduce temperature gradients, thereby ensuring consistent temperature at all points in the tank. The whole system can be expressed as a temperature control function: T_actual = f(P_heat, P_cool, t), where T_actual is the actual temperature, P_heat and P_cool are heating and cooling power, respectively, and t is the time, and the system dynamically adjusts the power to bring the T_actual close to the set value T_set.
Calibration method
The temperature measurement of the refrigeration stirring tank mainly relies on built-in sensors, but it needs to be calibrated regularly to ensure accuracy. Calibration is usually carried out with reference to international standards such as ISO 9000 series or national metrology specifications JJF 1030, using external standard thermometers such as high-precision platinum resistance thermometers or glass mercury thermometers. The specific steps include: setting the thermostatic groove to the target temperature point (e.g., 0°C, 25°C, 50°C), and after the temperature stabilizes, place the standard thermometer in different positions (center and edge) in the tank, record the readings and compare them with the displayed values of the device. The error calculation can refer to the formula: ΔT = T_display - T_standard, where ΔT is the deviation, T_display is the temperature displayed by the device, and T_standard is the standard thermometer measurement. If the deviation exceeds the allowable range (e.g. ±0.1°C), the device sensor or controller needs to be corrected. In daily use, it is recommended that users evaluate temperature uniformity through multi-point monitoring and record the potential impact of environmental conditions (e.g., humidity, air pressure) on the measurement.
Factors affecting temperature stability
The performance of the refrigeration stirring thermostatic tank is affected by a variety of factors. The choice of working medium in the tank is the key: the heat capacity, viscosity and thermal conductivity of different media vary greatly, for example, silicone oil is suitable for the high temperature range but has high viscosity, which may increase the stirring load; Deionized water has good thermal conductivity but is easy to evaporate, and antifreeze needs to be added at low temperatures. Environmental conditions such as laboratory ventilation and ambient temperature fluctuations can also interfere with thermal balance, leading to reduced temperature control accuracy. The characteristics of the equipment itself, such as mixing speed, heating and cooling power matching, sensor response time and tank insulation design, are all related to temperature stability. In addition, load changes (e.g., in large sample containers) can alter heat capacity and require rebalancing of the system. Users can reduce the impact of these factors by optimizing the media type, controlling environmental disturbances, and setting the stirring parameters reasonably.
Applications
Refrigeration and stirring thermostatic tanks play an important role in several industries. In the chemical field, it is used for temperature control in catalytic reactions, polymer synthesis and other processes; In materials science, it can support viscosity determination, coating curing testing and metal corrosion research; It is often used in the food industry to simulate storage conditions and detect product stability; For environmental monitoring, it is used to calibrate sensors or culture microbial samples. Different applications have specific requirements for temperature range, accuracy, and uniformity, such as 37°C±0.1°C for some biochemical experiments, and -20°C for low-temperature testing of materials. The versatility of the equipment makes it a versatile platform for laboratories, adapting to diverse experimental needs.
Equipment selection
When choosing a refrigeration and mixing thermostatic tank, it is necessary to comprehensively consider the technical parameters and experimental needs. The temperature range should cover the minimum and maximum points required for the experiment, and leave a margin. The temperature control accuracy and uniformity indicators need to meet the requirements of standard methods, for example, general chemical experiments may accept an accuracy of ± 0.5°C, while precision measurements need to be within ±0.1°C. The tank volume needs to match the sample size, taking into account the medium capacity and thermal inertia. The cooling capacity needs to adapt to the need for rapid cooling, and the heating power should be able to compensate for the heat loss. The mixing system should provide adjustable speed to ensure adequate media flow. Other factors include equipment safety (e.g., overheating protection), energy consumption levels, ease of maintenance, and compatibility (e.g., the presence of an external circulation interface). It is recommended that users evaluate these parameters based on actual application scenarios and refer to relevant industry standards such as ASTM E77 or GB/T 26808 for selection.