Definition
A high and low temperature constant temperature circulation bath is a type of laboratory equipment that provides precise temperature control and circulation functions through liquid media. It can maintain the uniform and stable temperature of the working area in the tank over a wide temperature range (usually from below room temperature to high temperature), and circulate the thermostatic medium to the external device, providing a stable temperature environment for various experiments or testing processes.
Principle
The core working principle of the equipment is based on a closed-loop temperature control system. The system is mainly composed of a reservoir, a heater, a refrigeration unit, a circulation pump, a temperature sensor and a controller. The temperature sensor monitors the temperature of the medium in real time and feeds the signal back to the controller. The controller compares the measured value with the user's set value, outputs the control signal through the proportional-integral-differential algorithm, and dynamically adjusts the power of the heater or the operating state of the refrigeration unit to achieve precise temperature control. The circulation pump continuously moves the media through the internal and external circulation loops of the bath, ensuring uniform temperatures and meeting the heat transfer needs of external equipment. Its basic control logic can be expressed as:
ΔT = Tsetting - Tmeasurement
Controller Output Signal ∝ f (ΔT, Integral, Differential)
By continuous adjustment, Tmeasurementinfinite approach to Tsetting。
Measurement and performance evaluation methodology
The evaluation of equipment performance usually refers to relevant national or international standards (such as the spirit of standards such as DIN 12876 for some methods), mainly focusing on temperature stability, uniformity and accuracy. Temperature stability refers to the magnitude of the temperature of the operating point over time, which is assessed by recording the temperature data at the center point for a long time at a set temperature. Temperature uniformity refers to the temperature difference at different spatial points within the bath's effective operating area at a specific point in time, usually obtained using multiple calibrated probes to measure different positions at the same time. Temperature accuracy refers to the consistency between the displayed temperature of the device and the actual temperature measured according to a standard such as a high-precision platinum resistance thermometer. These parameters are measured after the equipment has reached thermal equilibrium and takes into account the effects of ambient temperature and humidity.
Influencing factors
A variety of factors can affect the final performance and operation of the equipment. The characteristics of the medium are the key factors, and the specific heat capacity, thermal conductivity, viscosity and service temperature range of the medium directly affect the heat transfer efficiency and temperature field uniformity. Environmental conditions such as ambient temperature and ventilation will affect the heat dissipation efficiency of the refrigeration system and the energy consumption of the whole machine. External loads, i.e. the heat capacity and heat exchange power of external devices connected to the circulating loop, can change the thermal equilibrium state of the system. The installation and maintenance of equipment, such as whether the circulation pipeline is smooth, whether the filter is clean, and whether the media is regularly replaced, will also have an impact on the reliability of long-term operation.
Applications
This equipment is widely used in non-medical drug research and testing fields that require precise temperature control. In materials research, it is used for thermal performance testing of polymer materials and composite materials. In the field of chemistry, it provides constant temperature sources for chemical reactors, distillation units, and rotary evaporators. In the petrochemical industry, it is used for the detection of oil viscosity, freezing point and other indicators. In electronic engineering, it is used for environmental adaptability testing of semiconductor components and circuit boards. In addition, it also plays an important role in laboratories in the fields of biotechnology (non-clinical therapeutic direction), food science, metrology calibration, etc.
Key points to consider in selection
The selection process requires a comprehensive evaluation of actual requirements and technical parameters. The temperature range should be clarified first, and the minimum and maximum operating temperatures required should be within the nominal range of the equipment, with an appropriate margin. Secondly, focus on capacity and circulation capacity, the volume of the tank needs to meet the size requirements of the immersion sample or equipment, and the flow and pressure of the circulation pump need to match the resistance of the external circulation loop. In terms of performance parameters, the temperature stability, uniformity and accuracy indicators indicated in the product specification should be carefully verified. It is also necessary to consider the type of medium, and choose suitable media such as silicone oil, water, and ethylene glycol aqueous solution according to the operating temperature. Other factors include ease of use of the control interface, safety features (e.g., low level protection, over-temperature protection), device size and noise level, and the manufacturer's ability to provide technical support and calibration services. By systematically matching requirements with technology, equipment that meets specific experimental requirements can be selected.