Principle of High Temperature Vertical Tube Furnace

High temperature vertical tube furnace is a heating device designed with a vertical structure. Its core principle is to achieve uniform heating of materials in high temperature environments through the synergistic effect of conduction, convection, and radiation heat transfer methods. The following is a detailed analysis of its working principle:

1. Structural foundation and heat source type
Vertical structure
The material is added from the top of the furnace, heated by the furnace, and discharged from the bottom of the furnace. This design makes the device compact in structure, occupies a small area, and is easy to install and move. The furnace is usually made of high-temperature resistant materials such as alumina fibers or high-purity quartz wool, and is equipped with furnace tubes (quartz tubes or ceramic tubes) inside, with samples placed inside the tubes.
Type of heat source
Electric heating: Electrical energy is converted into thermal energy through heating elements such as resistance wires, silicon carbon rods, or silicon molybdenum rods, arranged around the furnace tube, and directly heated to the target temperature.

2. Heat transfer method and synergistic effect
Conduction heat transfer
Path: Heating element → Furnace tube → Sample.
Characteristics: The thermal conductivity of the furnace tube material directly affects the heat transfer efficiency. For example, alumina ceramics have low thermal conductivity and are suitable for uniform heating; Graphite has a high thermal conductivity and is suitable for rapid heating.
Function: Ensure efficient heat transfer from the heating element to the inner wall of the furnace tube, and then conduct it to the sample through contact.
convective heat transfer
Path: Gas flow inside the furnace → Heat transfer to the sample.
Characteristic: If a protective gas (such as nitrogen or argon) is introduced, the gas will absorb heat and transfer it to the surface of the sample through flow. The convective heat transfer efficiency depends on the gas flow rate and thermal conductivity.
Function: Promote temperature uniformity inside the furnace and avoid local overheating or overcooling.
Radiative heat transfer
Path: Heating element/furnace tube surface → emitting infrared radiation → directly heating the sample.
Characteristics: Radiant heat transfer dominates at high temperatures, and its efficiency is proportional to the fourth power of temperature.
Function: Provide the main heat during high temperature stages (such as exceeding 800 ℃) to ensure rapid sample heating.

3. Key components and functions
furnace tube
Material: High temperature resistant ceramics or metal alloys, such as quartz, alumina ceramics, or stainless steel.
Function: To carry the sample and serve as a heat transfer medium, ensuring isolation of the sample from high temperature environments (such as preventing oxidation).
insulation layer
Materials: alumina fiber, high-purity quartz cotton, etc.
Function: Reduce heat loss, maintain stable furnace temperature, and improve thermal efficiency.
Gas environment regulation system
Function: By introducing inert gases (such as nitrogen and argon), reducing gases (such as hydrogen), or oxidizing gases (such as oxygen), the furnace atmosphere can be controlled to meet specific process requirements (such as preventing oxidation and carburizing treatment).
control system
Function: Adopting PID regulation technology, real-time monitoring of furnace temperature through thermocouples, and feedback to the control system to adjust heating power, achieving precise control of heating rate, constant temperature time, and cooling curve.

4. Operation process and advantages
operating procedure
Load the sample into the furnace tube.
Set the heating program (such as heating rate, constant temperature time).
Introduce the required gas (such as inert gas protection).
Start heating and the control system automatically adjusts the power.
After the experiment is completed, cool down according to the preset program and remove the sample.
advantage
Temperature uniformity: Three heat transfer methods work together to ensure uniform temperature distribution inside the furnace.
Atmosphere controllability: By using a gas regulation system, different process requirements for the atmosphere can be met.
Efficient and energy-saving: The insulation layer reduces heat loss and improves thermal efficiency.
Safe and reliable: equipped with safety functions such as over temperature protection, over-current protection, and door lock switch.

5. Application Fields
High temperature vertical tube furnaces are widely used in:
Materials Science: Metal Heat Treatment, Ceramic Sintering, Powder Metallurgy.
Semiconductor industry: silicon wafer annealing, photoresist curing.
Chemical engineering: catalytic reactions, vapor deposition.
In the field of new energy: sintering of lithium battery materials and preparation of solar cells.