The difference between blast and non-blast
Laboratory drying ovens are common equipment for heat treatment, constant weight or moisture removal of samples. The core difference is whether it is equipped with a forced air convection system, that is, two modes: blower and non-blower (natural convection). Selection should be based on experimental purpose, sample characteristics and standard requirements.
Differences in working principles
The blast drying oven creates internal airflow circulation through the built-in air mechanism, so that the hot air is evenly distributed, the heating is fast and the temperature uniformity is good, usually fluctuating in the range of ±0.5°C to ±1°C. The non-blast drying oven relies on the natural rising convection of hot air, with low heat transfer efficiency, large temperature gradient (the temperature difference between the top layer and the bottom layer can reach 5-10°C), and the heating is slower.
Key performance comparison
| Parameters | Description |
|---|---|
| Temperature uniformity | The temperature difference of the blast type laboratory site is small, generally ± 1°C; The non-blasted type may exceed ±3°C. |
| Rate of warming | The blast type is fast, about 5-10°C/min; The non-blast type is slow, about 1-3°C/min. |
| Airflow influence | the blast type has airflow disturbance; Non-blasting type stationary without interference. |
| Temperature control accuracy | The blast type can be adjusted by PID, and the accuracy is high. The non-blasting type has lower accuracy. |
Definition of applicable scenarios
Blast drying ovens are suitable for: experiments that require rapid drying, large quantities of samples, and high temperature consistency requirements, such as moisture content determination and material aging test. Non-blast drying ovens are suitable for: dusty, lightweight powders (e.g. solid fuels), where samples need to be avoided being blown away, or when standards require slow heating (e.g. some wood moisture tests).
Sample stability considerations
Some samples (e.g., heat-sensitive substances, bioactive materials) may accelerate oxidation or mechanical loss in the airstream, where non-blasting mode is more secure. The blast mode helps ventilation and ventilation, volatile or flammable gases, but it is necessary to pay attention to whether the gas type is qualified.
Energy consumption and usage costs
The blower type generally has 10%-20% higher energy consumption due to the continuous operation of the fan. However, due to its rapid heating rise, the total drying time is shortened, and the cost per sample processing may be lower. The non-blower type equipment has a simple structure and slightly lower maintenance costs.
Recommended steps for selection
The first step is to query the fastest requirements for temperature uniformity in the experimental standard. The second step is to evaluate the physical and chemical properties of the sample. The third step is to compare the temperature performance indicators of the equipment (such as fluctuation). The fourth step is the size of the processing volume (the blast type is suitable for multi-layer batches).
References
1. General Technical Conditions for Laboratory Instruments, Part 7: Drying Oven.
2. Technical data of temperature parameter test method in constant temperature drying oven.
3. Material drying experiment operation and equipment selection guidebook.