The leader sets the questions; seeking advice from colleagues in the teaching field
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:Having received a request for help from colleagues, I’m sharing this with everyone so we can work together on the design and come up with solutions each on our own. In principle, the cost of electrical components should offer the best cost-performance ratio in terms of automatic control capabilities. For liquid storage and heating, three-phase electricity is required to heat the liquid to 90°C before cold items are added. Once these cold items reach 90°C, the temperature is maintained automatically for 90 minutes before the items are removed; then a second batch of cold items is added, and the temperature of the liquid begins to drop. It is necessary to heat the liquid back to 90°C, maintain that temperature for another 90 minutes, and then remove the items again. This process is repeated N times. Temperature records must be kept during each heating and holding period, and these records should be printed along with the batch number of the items. The temperature must be maintained at exactly 90°C, with a tolerance of ±1°C; otherwise, the items are considered unqualified. Thank you! ! !
Can electric heating be controlled with such precision, to within one degree, positive or negative?
Mm. Is it easy to implement? Let me share some ideas, thanks
I feel like this is at a pretty high level
Process: Two tanks are used – Tank A is for heat retention, while Tank B is used to produce 90-degree liquid. Tank A is located below Tank B, and a pump is used to transfer the liquid from Tank A to Tank B in a steady manner. An electric heater is installed in Tank B, with temperature control via PID regulation. Tank B is equipped with a heating area and a storage area. Control points: Temperature control of Tank B; pump shutdown via interlock alarm for low liquid level in Tank A; pump shutdown via interlock for high liquid level in Tank B. Key points for process calculation: calculation of the heat capacity of the object to be insulated, calculation of the capacities of tanks A and B, calculation of the circulation rate, and calculation of the heating power. Key points for equipment selection: when selecting pumps, the requirements of the medium must be taken into account; when selecting tank B, attention should be paid to the design of the partitions, and when selecting tank A, consideration must be given to the inlet and outlet conditions of the object to be insulated.
Thank you for your thoughtful reply. Actually, I was trying to find out how to control it, and you have given me another approach – I am very grateful!
It can be controlled by a PLC. The PLC first controls the heating system to heat the liquid tank; when the liquid temperature reaches 90 degrees, it sends a command to start adding cold objects. When the liquid temperature falls below 90 degrees ±1 degree, the PLC sends a command to heat the liquid again. Once the liquid temperature reaches 90 degrees, timing begins, with a tolerance of ±1 degree. After 90 minutes have passed, the heated objects are removed, and this process is repeated in a cycle
This post was last edited by Abing on 2017-1-13 at 15:03; it’s a bit messy. Let’s discuss our ideas to see if they align: A heating element is used to heat a certain medium and maintain a temperature of 90°C; this medium then heats another substance, with the heating process lasting 90 minutes, during which the temperature rises from room temperature back to 90°C. If you only need to heat the material to 90°C, this is simple: just connect the power supply of the thermal resistance wire to the relay and interlock it with the temperature set by the temperature controller, setting the temperature of the controller at 90°C. As long as the temperature of the heat transfer medium is below 90°C, the resistance wire is powered to generate heat; heating stops once the temperature reaches 90°C. The problem is that if you want to heat the substance for 90 minutes, it is necessary to use detailed data such as the heat capacity, contact area, weight, density, etc., of the two media involved, in order to calculate the power required for the resistance wire. If only the temperature of the heat transfer medium is controlled, the control scheme is easy to implement and the cost is low.
It’s a good idea; it would be even better if there were a flowchart to make it clear at a glance. :):):):):):):)
I am your supervisor; I’m very angry that you shared the topic without my permission. Come to my office next Monday at 10 a.m. to give an explanation! ! !