Definition
A heated and refrigerated thermostatic chamber is a laboratory equipment that establishes and maintains a uniform and stable temperature environment in a closed or open tank through active temperature control technology. It is usually composed of core components such as tanks, circulation pumps, heaters, refrigeration systems, temperature sensors, and control systems. The device is capable of providing precise temperature control over a wide temperature range (common -80°C to +200°C, which varies by model) according to the set needs, providing reliable temperature conditions for sample reactions, instrument calibration, physical property testing, and other processes.
Principle
The working principle of the heating-refrigeration thermostatic tank is based on closed-loop feedback control. The core process is that a temperature sensor (e.g. the platinum resistor PT100) monitors the temperature of the medium in the tank in real time and transmits the signal to the controller. The controller compares the measured value with the user's set value and calculates the control amount through a specific control algorithm such as the PID algorithm. If the measured temperature is lower than the set value, the controller will drive the heating element to work. If the measured temperature is higher than the set value, the refrigeration system is started to cool down. At the same time, the built-in circulation pump promotes the continuous flow of liquid (thermal conductive medium) in the tank, ensuring that heat is transferred quickly and evenly throughout the working area, thereby reducing temperature gradients and achieving temperature uniformity in space.
Its temperature control process can be simplified into a feedback control system model. The relationship between the controller's output action (e.g., heating power P_heat or cooling power P_cool) and temperature deviation (ΔT = T_set - T_actual) can be adjusted by control algorithms to optimize response speed and stability.
Measurement and calibration methods
The evaluation of the performance of heating and refrigeration thermostatic tanks mainly focuses on temperature stability, uniformity and accuracy. Measurements are usually carried out according to relevant national or international standards (such as JJF 1030-2010 "Specification for Technical Performance Testing of Thermostatic Tanks").
Temperature uniformity measurement: Multiple calibrated high-precision temperature probes (such as standard platinum resistance thermometers) are placed in the tank working area to measure the temperature at different spatial points at the same time. Uniformity is usually defined as the difference between the maximum and minimum temperature values of each measurement point within a specified period of time.
Temperature fluctuation measurement: Fix a temperature probe at the center of the work area to record its temperature change over a period of time (e.g. 15 minutes). Volatility is usually defined as half the difference between the maximum and minimum temperature values during that time period.
Temperature accuracy calibration: Set the tank at multiple different temperature points, use a higher-level standard thermometer to measure the actual temperature in the tank, and compare it with the displayed value of the device, and the deviation is the temperature accuracy index. Regular such calibrations are the basis for reliable experimental results.
Influencing factors
The performance of the thermostatic tank is affected by a combination of factors. Environmental conditions are the main external factors, including ambient temperature, humidity and air circulation, which will affect the heat dissipation efficiency and temperature control stability of the equipment. The specific heat capacity, viscosity, thermal conductivity, operating temperature range and cleanliness of the medium will directly affect the heat transfer efficiency and temperature uniformity. The characteristics of the equipment itself, such as the matching of heating and cooling power, the flow rate and flow rate of the circulation pump, the parameter setting of the control algorithm, and the efficiency of the insulation layer, together determine the dynamic response of the system and the final temperature control quality. In addition, the way the user uses it, such as the heat capacity of the workload, whether the sample holder is placed to impede media circulation, whether the tank lid is open, etc., can also interfere with the local temperature field.
Main application areas:
The heating and refrigeration thermostatic tank has a wide range of applications. In the field of metrology, it is commonly used in the calibration and verification of temperature sensors, thermometers, temperature transmitters and other instruments. In materials research, it is used for performance testing of polymer materials, metals, composites, etc. at specific temperatures, such as thermal deformation temperature determination. In the petrochemical industry, it is used for the detection of pour point, freezing point, viscosity and other indicators of petroleum products. In the field of biological and food science (non-medical drugs), it can provide a constant temperature environment for enzymatic reactions, cell culture (non-therapeutic purposes), food shelf life testing, etc. In addition, it is also an important supporting equipment for various analytical instruments such as rotary evaporators, refractometers, viscometers, fermenters, etc., providing them with precise temperature control conditions.
Key points to consider in selection
Choosing the right heating and cooling thermostat requires a comprehensive evaluation of actual needs. The first consideration is the temperature range, ensuring that the maximum and minimum operating temperatures of the equipment cover the experimental requirements with appropriate margins. The second is the working volume and notch size, which need to accommodate the sample to be tested or supporting instrument parts. In terms of performance parameters, attention should be paid to temperature fluctuations, uniformity, and the time required to reach the set temperature (settling time), which must meet the accuracy requirements of relevant experimental standards or methods. Depending on the use case, special features such as built-in program heating/cooling capabilities, remote communication interfaces, anti-corrosion designs, or low-volatile media tanks may need to be considered. Equipment reliability, safety (e.g. overheating protection, low liquid level protection) and noise level during operation are also aspects that cannot be ignored. Finally, operating costs, including power consumption, refrigerant type, and maintenance and replacement intervals of the required thermal media, should also be factored into long-term use considerations.