The heat treating of samples is widely used in medical, pharmaceutical, biochemical and environmental labs. Heat treatment can be carried out by a variety of methods, though all of these involve the transfer of heat to sample from either a flame or an electrical heat source.
Heat transfer systems can be broadly categorized into either contact or a non-contact. Despite their name, contact heat transfer systems rarely have direct contact with a sample and instead are in contact with the sample holder, which then transfers the heat to the sample.
Non-contact heat transfer systems heat products radiatively, e.g. by exposing the sample to powerful near-infrared (NIR) radiation, and can be used to produce temperatures exceeding 50 °C (122 °F).
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Contact and non-contact heating methods both provide different advantages depending on the application they are used in. This article will explore the different types of heaters in Glas-Col’s range and their benefits in different applications.
Heating Products: Lamps and Bunsen Burners
Bunsen burners are one of the most well-recognized lab tools. It burns a controlled flow of gas beneath a test tube suspended by a clamp or a beaker on gauze and tripod. The upper point of the flame is in direct contact with the sample holder and directly transfers heat to the container.
The use of Bunsen burners was first established around 1850, however the technique has waned in popularity as the use of open flames presents a hazard; especially when heating volatile or explosive samples.
Heating lamps perform a similar function to Bunsen burners as they also project heat onto a sample. However, heating lamps use electrical energy and convert it into NIR radiation via a high watt bulb. The NIR radiation produced by the bulb is focused by a metallic socket into a ‘hotspot’ on the sample, which rapidly transfers energy in the form of heat.
The HOTSPOT Heat Lamp, produced by Glas-Col, can generate temperatures of up to 60 °C (140 °F) at up to a foot away, ideal for sensitive samples and low-heat applications.
Heating Mantles, Tapes, and Cords
Contact heat transfer systems are more appropriate for use in specialized or high-throughput applications. The cords and tapes used for contact-heating can be ten times hotter than heat lamps, allowing temperatures as high as 600 °C (1112 °F) to be reached.
Cords and tapes can be wrapped around the sample container to provide a high contact level and ensure a uniform temperature is applied. Wrap-around heating systems are electrically grounded making them safe for use in different applications.
Heating mantles operate in a similar fashion to wrap-around heaters (such as cords and tapes) but instead have a solid housing. Whilst they are less flexible than cords and tapes they can be designed with unique, application specific structures. Heating mantles take electrical energy and convert it into heat using internal elements; this heat is then directed into the sample container.
The main difference between contact and non-contact heating systems is the distance between the heater and the sample container. A short distance between the two results in less heat loss during transfer. For this reason, contact heaters, such as mantles and cords, conserve more energy than non-contact heaters.
However, direct contact is not always the best choice. Heating lamps remain a popular option for environmental control and for the warming of samples.
This information has been sourced, reviewed and adapted from materials provided by Glas-Col.
For more information on this source, please visit Glas-Col.