What factors can affect the temperature uniformity of a precision oven?

The application areas of precision ovens cover industries such as electronics and semiconductors, pharmaceuticals and biology, chemicals and materials, universities and research institutions, and some scenarios can also be expanded to hardware, food processing, and other fields!

The temperature uniformity of precision ovens is influenced by multidimensional factors such as equipment design, system configuration, and operating conditions. The core can be summarized into the following six categories, each of which directly determines whether the temperature distribution inside the oven is balanced:

1、 Hot air circulation system

Hot air circulation is the key to achieving uniform temperature inside the box, and any poor circulation will directly create temperature blind spots:

Fan performance and power: Insufficient fan power and low speed, unable to generate sufficient hot air flow, insufficient exchange of cold and hot air inside the box; Aging of the fan and damage to the impeller can also lead to a decrease in cycle efficiency and an increase in local temperature deviation.

Air duct design: Unreasonable air duct layout and blocked air ducts can cause hot air to not cover the entire inner space, resulting in situations where "local air cannot be blown and local air is blown too forcefully"; High quality design will adopt a circulation path of "upward return" or "side return", combined with deflectors to evenly spread hot air.

Circulation method: Forced horizontal circulation is suitable for flat workpieces, and forced vertical circulation is suitable for vertically placed samples. If the circulation method does not match the workpiece placement, it will block the hot air path and affect uniformity.

2、 Heating element configuration

The layout and performance of heating elements directly affect the uniformity of heat output:

Heating element distribution: Uneven distribution of heating tubes/heating plates can lead to excessive heat in local areas and low temperature in areas far away from the heating element; High quality ovens will use "evenly distributed tubes around" or "bottom+side wall combination heating" to avoid single point overheating.

Heating element type and power matching: Far infrared heating heats up quickly but concentrates heat, and if not paired with hot air circulation, it is prone to local overheating; Electric heating tubes provide milder heating, but their power does not match the volume of the inner container, which can also disrupt uniformity.

Heating element aging: Scaling of the heating tube and aging of the resistance wire can lead to a decrease in local heating power, resulting in a situation of "insufficient heating in some areas".

3、 Inner Tank Structure and Space Design

The physical structure of the inner liner determines the efficiency of hot air circulation and heat conduction:

Inner tank capacity and shape: If the fan power is not synchronized and matched for an excessively large inner tank, it will be difficult for the hot air to cover the entire area; Irregular inner chambers are prone to forming blind spots for hot air, while square/rectangular inner chambers are more conducive to hot air circulation.

Inner liner material and surface treatment: Excessive thermal conductivity of the inner liner material can lead to local heat accumulation, while mirror stainless steel, high reflectivity, and uniform thermal conductivity can reduce local temperature differences; The inner wall of the liner is rough and has oil and dirt accumulation, which can absorb heat and affect the heat reflection efficiency.

Internal tooling placement: Excessive number of layers, poor thermal conductivity of layer materials, or dense placement of workpieces/samples that obstruct air vents can block hot air circulation and create localized low-temperature zones.

4、 Sealing and insulation performance

Inadequate sealing or insulation can cause external cold air to seep in, internal heat to dissipate, and disrupt temperature balance

Door sealing: The aging, damage, and improper installation of the door seal can cause cold air to seep into the box door, forming a "low-temperature zone near the door"; The double-layer door structure has better sealing effect than the single-layer door, which can reduce cold and heat exchange.

Insulation layer performance: Insufficient insulation layer thickness, aging material, or gaps between the inner and outer boxes can lead to rapid local heat dissipation and temperature deviation.

Sealing of the cavity: There are gaps at the welding points of the inner liner, and the ventilation/dehumidification ports are not tightly sealed, which can cause hot air leakage or cold air to enter, affecting the overall temperature uniformity.

5、 Control system and sensor configuration

The accuracy of the control system and the position of the sensors determine the timeliness and accuracy of heat regulation:

Location of temperature sensor: If the sensor is installed near the heating element, it will misjudge the overall temperature inside the box, causing the controller to stop heating in advance, and the temperature in the area far away from the sensor will not meet the standard; High quality design will install sensors in the center of the inner container or the hot air return area, which is closer to the actual average temperature.

Precision of PID control system: Ordinary mechanical temperature controllers have lagging regulation, which can easily lead to fluctuations of "over temperature - cooling - over temperature"; The high-precision PID intelligent controller can adjust the heating power in real time, reduce temperature fluctuations, and indirectly ensure uniformity.

Heating power adjustment method: on-off heating can easily cause sudden temperature increases and decreases, while pulse width modulation or graded heating can smoothly adjust power and make heat output more uniform.

6、 Operating conditions and environment

Even if the device itself is well-designed, improper use can damage temperature uniformity:

Load situation: Excessive loading capacity and large differences in thermal conductivity of the load can lead to uneven local heat absorption and different temperature recovery rates; There may also be differences in the uniformity between empty and full loads.

Frequency and duration of door opening: Frequent opening of doors or prolonged opening of doors can lead to a large amount of cold air entering, causing a sudden drop in temperature inside the box and easily resulting in local temperature differences when restoring balance.

Environmental temperature and ventilation: Placing the oven in a high/low temperature environment with poor ventilation around can result in uneven heat dissipation from the outer box, indirectly affecting the temperature distribution of the inner pot; High environmental humidity can accelerate the aging of the insulation layer, further reducing uniformity.