Key factors in selection
As the basic equipment of the laboratory, the thermostatic chamber is widely used in material testing, food analysis, chemical synthesis and environmental monitoring. To choose a suitable thermostatic tank, it is necessary to focus on two aspects: the circulation method determines the temperature uniformity and temperature control efficiency, and the temperature control range matches the test conditions of specific experimental materials. The following is a systematic analysis of two types of core parameters.
Circular mode analysis
The circulation method refers to the flow form of the liquid medium in the thermostatic tank, which directly affects the temperature stability and the temperature difference between samples. There are two main categories:
Natural convection: Relies on the natural flow generated by the thermal expansion and contraction of the liquid, with a simple structure, suitable for static samples or extremely low temperature requirements. Its temperature uniformity is generally kept within ±0.5°C, but the temperature rises slowly, which is suitable for long-term stability testing.
Forced cyclic type: Drive the liquid flow through the pump body, which can be subdivided into internal circulation and external circulation. The internal circulation allows the liquid in the tank to flow forcefully, making the temperature field uniform, suitable for parallel testing of multiple samples. The external circulation transports thermostatic liquid to external devices (such as refractometers and viscometers) through the interface to achieve remote temperature control. The temperature uniformity of forced circulation can reach ±0.1°C, but the pump body noise and energy consumption are slightly higher.
When choosing, if the experiment involves high-precision temperature gradients or the combined use of external instruments, forced cycling is recommended; If only a single sample is left at a constant temperature, natural convection is more economical. In addition, it is necessary to ensure that the viscosity of the liquid medium (water, oil or silicone oil) matches the head of the pump body to avoid circulation obstruction.
Temperature control range consideration
The temperature control range determines the type of experiment that the thermostatic chamber can apply, usually in the common range of -40°C to +200°C. However, the actual selection needs to determine the lower and upper limits according to the phase transition temperature, reaction rate and material tolerance of the sample.
Low temperature range (-40°C to 0°C): Commonly used glycol or alcohol water baths for cold storage, low-temperature crystallization or viscosity measurement. The insulation layer of the tank should be thick enough to avoid the ambient temperature dropping too quickly. If it is below -40°C, mechanical refrigeration should be considered, and a low-volatile solvent should be selected for the circulating medium.
Medium temperature range (0°C to 100°C): Water-based media can be satisfied, and is widely used in biochemical samples, food enzyme activity detection or general material heat treatment. The focus of this range selection is on the corrosion resistance of the pump body, especially when antifreeze or buffer salt is added.
High temperature range (100°C to 200°C): It is necessary to switch to oil bath or silicone oil, which has good thermal stability but low volatility, and needs to be equipped with a sealing cover. When the temperature exceeds 150°C, the tank should be made of stainless steel and equipped with an active heat dissipation structure to prevent overshoot.
The larger the temperature control range, the better, and the wide range is often accompanied by poor low temperature uniformity. If the experiment is often carried out in a narrow temperature range (e.g., -20°C to +40°C), it is better to choose a model that only covers this range to achieve better temperature control results.
Joint selection recommendations
The thermostatic tank is not a single parameter that determines performance, and the circulation method and temperature control range need to be considered together:
If the temperature control range spans multiple zones (e.g., -40°C to +150°C), forced circulation must be selected because natural convection is less uniform over a wide temperature range.
If you mainly work in the low temperature area and take into account the high temperature, prefer the forced circulation tank with double pump head or independent external circulation design to avoid the aging of the pump seal at high temperature.
For laboratories that require precise temperature control and multitasking, it is recommended to configure the forced cycle type with programmable temperature control and support ramp-hold mode.
For example, a typical food laboratory needs to test the viscosity of ice cream at -10°C and the oxidation stability of oil at 180°C, and should use a forced circulation type with a temperature control range of -30°C to +200°C, and have two sets of silicone oils with different viscosities.
Comparison of technical parameters
| Circular mode | Applicable scenarios and characteristics |
| Natural convection | Single sample resting; Simple structure and low cost; The temperature uniformity is about ±0.5°C |
| Forced internal circulation | multiple samples need a uniform temperature field; uniformity±0.1°C; Pump noise needs to be considered |
| Forced external circulation | constant temperature of external equipment; The pump body provides pressure; The interface must be well sealed |
| Temperature control zone | Recommended media and precautions |
| 0°C to +100°C | deionized water or add antifreeze; Pay attention to daily replacement to prevent the growth of microorganisms |
| -40°C to 0°C | ethylene glycol-water-alcohol mixture; Make sure the slot cover is sealed to prevent frost buildup |
| +100°C to +200°C | silicone oil or high-stability mineral oil; Equipped with ventilation devices to prevent the accumulation of oil fumes |
Quote reference
1. General technical conditions for laboratory thermostatic equipment (test method for circulating pump flow and temperature field uniformity in current industry standards)
2. The analysis section on the temperature gradient of liquid baths in the Technical Manual of Temperature Calibration and Temperature Control
3. A review paragraph of the selection case of thermostatic tank in the recent literature in the field of material testing