In the middle of a hot and steamy summer, many people cannot wait for fall and the rapid cooldown of their local weather. The same goes for anticipating the turn of a cold and snowy winter into warmer spring-like weather. However, in the laboratory, rapid cooldown and heatup often are demanded by many applications. The use of high temperature circulators with rapid heatup and cooldown is one way to make that happen in those applications.
In most high temperature circulators, the compact design does not require a lot of bench or hood space, and closed-system construction prevents harmful fumes from escaping into the laboratory. Having a small filling volume allows the unit to react quickly to exothermic or endothermic reactions. The units also are capable of achieving 752°F (400°C) as a maximum temperature. Combine that with 6 kW of heating capacity and 15 kW of cooling capacity, and it provides a strong, versatile unit.
Space-Saving Design. Space is in high demand in work areas. With the consolidation of laboratories or new equipment consuming floor space, many industrial users are dealing with a crowded work area. Due to long cord lengths, compact high temperature circulators offer a controller that does not need to be placed right next to the unit. This allows the unit to be on the bench while the controller is placed on the wall or in any other convenient location. If the cord is not long enough, accessory connectors can extend the cord length by 16’. The compact design and available accessories give the end user the flexibility to place these units wherever space permits.
Rapid Response. Everything moves at a fast pace these days, especially many temperature-sensitive applications. Whether it is by operator choice or reaction parameters, sometimes a rapid change of temperature is required. The 2-liter filling volume on some high temperature circulators allows these temperature changes to happen quickly.
For example, in one application, the circulator may need to heat up to 394°F (200°C) in a half an hour. After a fixed amount of time, determined by the end user, the unit may need to cool down to 176°F (80°C) as fast as possible. Some circulators include add-on devices that ensure cooling down at a rapid pace is achieved. A connection to tap water, house water or a chiller may be required.
The add-on cooling unit also can help with applications that have a strong exotherm. As mentioned earlier, with potentially 15 kW of cooling, the high temperature circulator will hold the set temperature and neutralize the exotherm. With a 100 platinum sensor connected in the external system, the unit can sense the temperature starting to rise. A valve in the add-on cooling unit will open and call for water to cool down the coil containing bath fluid.
For endothermic reactions, high temperature circulators have strong heating capacities. Some models provide 3 kW of heating while others offer 6 kW of heating. The wattage of the endotherm helps determine which units have enough capacity to heat the reaction and overcome the endotherm.
In open heating baths, the ambient air is a factor in heating to high temperatures. Anyone who has heated oil up above 302°F (150°C) can attest to how this will affect the work area. Because high temperature circulators are closed units, the bath tank is not exposed to the ambient air. This prevents fumes from escaping into the laboratory and also helps in temperature control. With its closed design, the only areas affected are the pump connections, tubing and external vessel. With good insulation, even those areas can be protected. For fast heatup and cooldown times, high temperature circulator units have the capacity to safely control the reaction.
High Maximum Working Temperature. With an upper temperature limit of 752°F (400°C), the units are suitable for applications that require working at a high temperature such as hydrogenation, photovoltaic panel manufacturing, thin-film and polymerization.
There are many benefits for using high temperature circulator units when working at high temperatures. For instance, users are able to use one fluid for the entire working range. While filling the units, air is purged from the system and, because the air is removed, the unit can exceed the fluid flashpoint. This is important because there is no chance of a fire starting.
Another benefit is a cracking-protection setting, which limits the circulator fluid temperature. The fluid that is directly in contact with the heaters will be hotter than fluid that is not touching them. This setting limits the temperature rise so that the fluid contacting the heaters is not excessively hot, which could cause the fluid to break down. It will still heat up but at a pace that protects the fluid, allowing for longer fluid life.
A fluid expansion vessel is essential when heating to high temperatures because fluid expands by 12 percent every 100 degrees. This vessel will capture any fluid that expands from the bath tank. For larger applications, a second expansion vessel can be added. To add to its convenience, the vessel is connected to the cool zone, which will cool down the fluids so they are not as hot as in the heating zone.
Lastly, even at high temperatures, the circulator allows for tight stability. A self-optimizing controller can adjust the PID parameters, allowing the unit to learn the external application and adapt its control features.
High temperature circulator units have the ability increase reliability, accuracy and reproducibility. Fast heatup times are achievable and, with a cooling unit attached, controlling an exotherm and cooling back down to near ambient temperatures are also achievable. Additional accessories and menu options enhance the circulator and the application. The features and benefits of a high temperature circulator help keep the laboratory safe and operating efficiently.