In this article, the servo property of a high-performance magnetorheological valve will be evaluated by closing the pressure feedback loop. The magnetorheological valve developed in this study has two separately controllable fluid flow channels and is especially designed for high-frequency applications. A state space model of the magnetorheological valve from the control signal to the pressure output will be identified, and the identified model is used for tuning a proportional–integral–derivative controller and for simulation of the closed-loop system. Finally, the controller will be implemented to a control computer, and the pressure output will be controlled in a real-time control loop. By analyzing the dynamic and static performance of the magnetorheological servo valve, it can be stated that the magnetorheological valve has a good potential for high-frequency pressure and force control applications.
The purpose of this article is to demonstrate that additive manufacturing is a viable method for producing counterflow heat exchangers that have a very high power to volume ratio. For this study, a heat exchanger with 144 flow channels in a checkerboard pattern was designed and additively manufactured from AlSi10Mg. The heat exchanger was tested by measuring the heat transfer between two liquids in a counterflow setup , where it reached exceptionally high performance when considering its volume and weight. The heat transfer properties of the heat exchanger were verified analytically through calculations, which identified that the high surface roughness of the channels provides a significant improvement in heat transfer properties. The heat transfer capabilities were measured on two separate occasions to investigate the possible change of properties of additively manufactured heat exchangers over time when used with tap water. A moderate decrease in heat flow and increase in pressure drop were noted between the measurements. The deterioration of heat transfer capabilities could present a significant challenge for additively manufactured heat transfer applications and will be closer examined in future research.
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