To see other variants and accessories, please enter the webcode on our website. webcode 597 KNOWLEDGE LABORATORY CIRCULATORS Operating temperature range The temperature range which is limited by the electronics. Auxiliary equipment can be used to extend the lower end of the temperature range on temperature circulators. Working temperature range The temperature range within the operating temperature range that can be reached by the temperature control system by itself at an ambient temperature of +20°C without auxiliary equipment. Temperature stability Temperature difference between the highest and lowest temperature measured in a laboratory circulator or laboratory bath divided by 2. Temperature homogeneity Temperature difference between the highest and lowest temperature measured in the bath vessel. Temperature display Temperature displays using LED's are easy to read from any viewing angle, even from a relatively long distance away. In addition to the setpoint and actual temperature, the unit should also be able to display high and low temperature warnings. The VFD COMFORT DISPLAY is even more user friendly. For added user comfort, state-of-the-art temperature control systems come with touchscreen displays.. PID and ICC temperature controls The circulator's temperature control device has a significant influence on heating/cooling characteristics. The basic control technology affects the precision and speed of the heating/cooling process. PID controls have proven to be effective in practical application. These controls either operate with fixed control parameters (Xp, Tn, Tv), or ideally the parameters can be adjusted manually. The ICC (Intelligent Cascade Control) is currently the most advanced type of control. Cascade technology delivers perfect results. The control parameters are automatically adjusted and optimized for the particular application. ICC devices are integrated into the JULABO HighTech series of circulators. Pump systems Submerged pumps have a proven track record in the field. They operate without significant wear for long periods of time. In addition to maintaining circulation in the bath, they permanently supply heating/cooling fluid to objects or systems in the pump circuit. It is important to ensure that sufficient pumping capacity is available, particularly in external applications. Electronically controlled pump pressure can have advantages in many applications (for example when delicate glassware is present). Heating and cooling circulators Laboratory circulators are divided into heating and cooling circulators. Heating circulators only have a heating element and can only operate above the ambient temperature. External cooling solutions (tap water or a refrigeration unit) can be added for temperature control applications below ambient temperature. If cooling work is necessary on a regular basis, the use of a cooling circulator with integrated refrigeration unit is recommended. Depending on the model, temperatures as low as -95°C can be achieved. Cooling circulators have the additional advantage that they can cool quickly at high temperatures without additional equipment. It is also advisable to invest in a cooling circulator if there is a frequent need for quick cooling. One feature of cooling systems is proportional cooling, where an electronic value is used to control cooling output. This solution allows precision control of cooling output, and it also saves energy. Early warning systems improve reliability Most circulators offer warning and protection functions. These functions enhance operational reliability and protect the sample. The upper and lower temperature limits as well as the liquid level need to be monitored. Adjustable limits as well as warning and shut-off functions offer enhanced reliability. JULABO early warning systems (DBGM) offer advanced features. The low-level early warning system emits an acoustic signal to indicate insufficient heating/cooling fluid before the system shuts down. Classification is defined in DIN 12876-1 Terminology and classification are defined in DIN 12876, and they provide application information. Circulators are divided into the following categories: Class I: Equipment in this class has a fixed temperature limit and fixed low liquid level protection. The devices are only suitable for use with non-flammable liquids. Class III: Equipment in this class has adjustable excess temperature protection and additional low liquid level protection. The devices are suitable for use with flammable liquids. Attaching an external system The following guidelines must be observed when an external system is attached: • Tubing between the circulator and the external system must be as short as possible. It must be well insulated, and measures must be taken to ensure that tubing does not slip off. • Always use a suitable, low-viscosity heating/ cooling liquid (e.g. JULABO Thermal) • Optimize the energy exchange between the circulator and the external system (e.g. avoid bottlenecks in the lines). • Ensure that the external sensor has good thermal coupling. Heating/cooling fluids De-ionized water is recommended for working temperatures up to +80°C. Distilled water adsorbs composites from the components, and this can result in corrosion. Special fluids can be used to extend the temperature range, for example JULABO Thermal. These fluids have a significantly lower specific thermal capacity, which is another advantage. Consideration must be given to the flash point and fire point during the selection process. The viscosity specified by the circulator manufacturer must not be exceeded even at low temperatures. Alcohol (e.g. ethanol) has a very low flash point, which means that it is not suitable in some applications. Calculating heating and cooling power The following formula can be used for time-dependent calculations: Q = (m × c × dT) / t Q = required cooling/heating power in kW m = material mass in kg c = specific thermal capacity (water=4.2 / ethanol=2.5 / silicone oil =1.8) dT = required temperature differential in °C t = desired cooling/heating time in seconds The total volume (mass) is made up of the individual volumes (e.g. circulator, tubing, reactor jacket and reactor). This simple formula ignores differences in the specific weight of the liquids and power loss factors. Power loss is caused by tubing (length, insulation), double-wall containers (material, thickness and surface area), high ambient temperature and open applications (surface). A safety margin of 20-30% should be included in the calculation to ensure sufficient heating/cooling performance. Cooling circulator with integrated refrigeration unit JULABO early warning system with float and micro switches (DBGM) Heating circulator Temperature control system with externally connected system
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