In a gravity convection oven, the temperature distribution is based on warm air moving upwards. There is no fan that actively distributes the air inside the chamber. The benefit of this technology is very low air turbulence for gentle drying and heating.
In a mechanical convection – or forced air – oven an integrated fan actively moves the air inside the chamber. This results in an even temperature distribution throughout the chamber. One benefit is optimal temperature uniformity for reproduceable results. For example, this type of convection is ideal in material testing and for drying protocols with very tight temperature requirements. Another advantage is a faster drying process compared to gravity convection. When opening the door, the temperature will recover faster to the set temperature level in a mechanical convection oven.
Select Thermo Scientific heating and drying ovens are capable of operating at up to 330°C, and as low as ambient +10°C. See the chart below to select the right model of heating and drying oven based on your temperature and application needs.
Application | Material/Sample | Sample Requirements | Recommended Heratherm Heating & Drying Oven |
Drying |
Glassware |
Fast drying |
Gravity convection ovens for gentle drying, mechanical convection for fast drying. Advanced Protocol Ovens for highest temperature accuracy and selection of fan speed. Advanced Protocol Security Ovens for additional sample safety. You may also consider a Thermo Scientific vacuum oven for speedy drying at low temperatures. |
Powders |
Temperatures between 37°C and 70°C |
||
Paper, textile |
Temperature around 37°C |
||
Soil, sand |
Temperature around 37°C |
||
Electronics |
Temperatures around 37°C to around 50°C | ||
Pharmaceutical preparations | Temperature around 37°C |
||
Material testing |
Cables |
Highest temperature accuracy; safe processes |
Advanced Protocol Ovens with programming capabilities. Select the mechanical convection models for our highest temperature accuracy. Advanced Protocol Security Ovens offer additional sample safety. |
Plastics |
Highest temperature accuracy; safe processes |
||
Curing |
Paint |
Gentle heating |
Gravity convection for gentle heating Advanced Protocol Ovens for high temperature accuracy – low fan speed is appropriate for gentle heating needs. Advanced Protocol Security Ovens for additional sample security. |
Adhesives |
Gentle heating |
||
Plastics |
Gentle heating |
||
Metals |
Gentle heating |
||
Heated storage |
Pills, drugs |
Gentle heating, safe processes |
|
Volcanization |
Rubber |
Gentle heating |
Heat transfer under vacuum
Heat transfer to samples in a vacuum is mainly reached via the shelving. Unlike in regular heating and drying ovens, there is no heat transfer via convection. A good contact of the samples with the shelving is therefore crucial for the heating and drying effectiveness. If samples are in containers, it’s important that the containers have a good temperature conductivity.
How to measure temperature in a vacuum oven
To measure the chamber temperature, the probe needs to have full contact with the shelf. For best results it is recommended to connect the probe with a piece of metal with high temperature conductivity.
Tips for inert gas applications
The use of inert gas atmosphere might be required to avoid oxidation processes, related to presence of oxygen. If the application requires replacing the vacuum with an inert gas, use only a non-combustible, nonflammable, non-corrosive gas – such as nitrogen or argon. Purging the chamber several times will help reduce the oxygen content to a minimum.
Note that vacuum ovens chambers are not made for positive pressure. The gas inflow therefore should be controlled and conducted with low pressure.
A precision valve is incorporated into the inert gas connection so that the gas can be dispensed accurately, reducing drying times and helping to reduce or prevent condensation. Furthermore, the precision valve can safely prevent blowing of powders when the vacuum chamber is ventilated.
Using a vacuum for drying requires a lower temperature than standard drying ovens. Under a vacuum humidity evaporates below the usual boiling point of the liquid that needs to be removed – resulting in a gentler drying process for delicate samples. Process times are up to six times faster than in conventional drying ovens.
This graph illustrates that water will evaporate at a much lower temperature than 100 °C, with lower pressure inside a vacuum oven.
Offered with various temperature ranges and sizes, Thermo Scientific Vacuum Ovens are designed with safety, reliability and efficiency in mind—and offer features that can tailor your vacuum oven to your specific applications.
Thermo Scientific vacuum ovens provide temperature uniformity and reproducible drying and heat treatment for pharmaceutical, food, electronics, medical devices and aerospace applications, such as:
Smart Vue Pro monitoring can be configured with Thermo Scientific heating and drying and vacuum ovens and data can be monitored on the Thermo Fisher Cloud.