Thermal Management Control

Implementation of custom solenoid valves in thermal management systems to accurately control flow rate can enable greater vehicle reliability and efficiency

Next generation vehicles require better thermal management control. Controlling components and systems to optimal temperatures can offer increased reliability, efficiency, durability and safety. Developing custom solutions incorporating solenoid valves are emerging as attractive and cost-effective solutions.

These solutions may be obtained using a solenoid valve, a subset of similar solenoid valves or an array of different solenoid valve types. Typically, there are three main electromechanical solenoid valve types used in liquid cooled systems: binary, proportional and latching. The valve’s performance requirements determine what type must be used in each application. A binary and latching valve allow for two positions of flow control either fully open or fully closed. While a proportional valve allows the controller to vary the position of the flow restricting component, changing the fluid output.

With high-end magnetic and fluid modeling software, the performance of any type of solenoid valve can be designed with confidence before producing physical samples. Figure 1 displays a latching and a binary magnetic circuit. Magnetic flux is generated from either a permanent magnet or by applying power to a copper coil. As the magnetic flux increases through the ferritic materials, the parts become saturated, creating a greater magnetic force. The latching circuit incorporates permanent magnets, which requires zero power to stay in the retracted position (position depicted in Figure 1). Adversely, the binary magnetic circuit requires constant power to stay retracted. Magnetic modeling enables the magnetic performance, weight and material selection to be tailored to specific requirements.

Latching magnetic circuit (left) and binary magnetic circuit (right) valve types
Figure 1: Latching magnetic circuit (left) and binary magnetic circuit (right) valve types

Variables such as pressure drop, flow rate and fluid dynamic forces can be optimized based on results from fluid modeling. Figure 2 shows a 3D fluid pressure model. At each positional change the output flow rate can be recorded to create a flow rate curve. Using these baseline platforms, future development will have fewer significant design changes, resulting in improved project timelines and cost savings.

Each custom solenoid valve is designed for a specific application, so its performance is not over or under engineered. Attributes that can be tailored include; response time, solenoid actuation life, temperature rating, outlet flow accuracy, etc. With proper material selection, durability can be increased allowing valves to be compatible with almost any automotive fluid. Proper material selection allows valves to operate at temperatures from -50°C to 200°C. Solenoids can provide response times within milliseconds, with flow control accuracy up to 2%. Solenoids provide the additional benefit of a failsafe position. A typical solenoid has a hard stop with a mechanical return. This is beneficial in safety applications where the device must return to its initial position with a state of zero-power. With the correct attributes, all requirements can be met for many applications.

3D CFD modeling can show any changes in pressure, flow rate and fluid dynamic force
Figure 2: 3D CFD modeling can show any changes in pressure, flow rate and fluid dynamic force

Many vehicles can benefit from this technology. Solenoid valves can be used in the engine compartment; thermal management of batteries, electrical components or systems or the entire cooling system. Since valves do not require proximity to the main pump supply they can be placed strategically throughout the vehicle. As more electronics are added with vehicle advancements, electrical components temperature sensitivity must be considered. This sensitivity requires temperature to be maintained in a tighter operating range. If the performance of these electrical systems or batteries can increase 1-2% using a thermal management system, this could correlate to increased savings and efficiencies in the vehicle.

Implementing a custom solenoid valve for thermal management systems can provide an efficient, cost-effective solution. Having the ability to control flow with different solenoid types allows for the correct solution to be adapted to the specific system’s needs. This brings a robust solution to the market that can resist extreme temperatures, supply highly accurate flow control, provide a failsafe position, and increase vehicle reliability and efficiency.

***First published in Engine Technology International magazine, March 2019***


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