Temperature control unit
A temperature control device is a permanently installed device that, as part of a production system, takes on the temperature control of a medium for the production process . The medium for the transport of heat as energy is mostly oil. However, other fluids can also be used depending on the application. The fluid brought to a set temperature is added to the process via pipelines of the system, where the medium transfers the heat or cold as energy and is returned to the temperature control unit in the closed circuit in order to replenish the lost energy. Often the temperature control devices have both a heating function and a cooling function. The aim of a temperature control device is to supply the set target temperature to the manufacturing process and to keep it constant.
Working principle
Almost all media can be used as an energy source for the temperature control unit. It is common to connect the energy supply to a central thermal oil heating system or to a steam line as an energy supply for very high outputs. The heat is transferred from the source indirectly via the heat exchanger or directly via control valves to the circuit for supplying the system. In the simplest case, the regulation for the supply of the required amount takes place via a two-point controller which controls a control valve. Several temperature sensors are installed in the intelligent devices, which continuously record the temperature changes and, depending on the temperature jumps in the process, have a dynamic control behavior - PID control , and control the actuators, mostly solenoid valves, so that the setpoint temperature at the required point in the process is almost remains constant. The setpoints for the temperature are set directly on the device or specified by an interface from external controls. The newer intelligent devices have digital interfaces via which both the setpoints and the actual values are communicated and thus enable continuous logging of the process parameters.
Electrical connection
For the operation of the temperature control units, the electrical power is only required to control the valves and operate the controller. In order to convey the fluids, additional conveying pumps are required, especially in systems with separate circuits and heat exchangers. The pumps were previously designed for a constant flow rate. The pumps are now also included in the control, and the control changes the delivery rate of the pumps. Thanks to the newer technologies, a better efficiency of the system and energy savings can be achieved. In some applications, electrical heating cartridges are built into the circuit for the production process, which take over the fine adjustment of the temperature control or also serve as an expensive energy carrier in the event of a failure of the main medium in order to maintain production.
Efficiency and areas of application
The temperature control devices are often used in melting processes, as is necessary in plastics processing . For example, plastics are added to the process as granulates, and when processed in extruders and calenders, in addition to the pressure and frictional heat, they are heated with temperature control devices and kept at that temperature. Since the temperature control devices are mostly just the energy converters, their efficiency is relatively high. Most energy losses are conduction losses in the form of heat and radiation losses from the device.
Individual evidence
- ↑ Sigurd Lohmeyer, Günther Engel, Peter Friel, Johannes Schlag, Andreas Tomanek, Konrad Uhlig: The special properties of plastics II . expert verlag, 1995, ISBN 978-3-8169-0303-1 , p. 141 ( limited preview in Google Book search).