Electrohydrodynamically Driven Thermal Management for Space and Terrestrial Applications – An Experimental and Numerical Study

O'Connor, Nathaniel

Etd

Electrohydrodynamically Driven Thermal Management for Space and Terrestrial Applications – An Experimental and Numerical Study

Öffentlich Deposited

The rapid development of modern electronics has resulted in significant computational power in increasingly small packaging. However, a significant challenge remains in effectively controlling the temperature of electronic components, especially in harsh environments such as space. With the revitalized interest in space development through NASA’s Artemis Program and the increasing commercialization of space, development of improved thermal management technologies is needed with the objectives of reducing the mass and increasing the efficiency of heat transfer systems. Electrohydrodynamic (EHD) pumps have been identified as an advanced technology to support NASA’s future human, robotic, and deep space missions. Electrohydrodynamic conduction pumps in particular have the advantage of being lightweight, with no moving parts, and are highly effective for thermal enhancement. The first goal of this research is to provide fundamental understanding of the EHD conduction mechanism and how the performance of a pump varies with fluid temperature. Future implementation of EHD conduction pumping on satellites will be subjected to changing temperature environments when orbiting the Earth. Thermophysical and electrical properties of the working fluid are all functions of temperature, and existing studies in the literature have reported both increasing and decreasing performance with temperature. An experimental setup was fabricated to carefully control the working fluid temperature and measure the static pressure generation of the EHD conduction pumps designed in the previous studies. This experimental study validated the theoretical model of EHD conduction and observed changes in pumping regime based on experimental conditions. It was also observed that there exists a strong transient effect which is also temperature dependent. With this validated model, the pumping performance can be predicted as a function of nondimensional numbers that define the system. This understanding of the performance behavior is critical for the future design and optimization of thermal control systems based on EHD conduction. Another primary goal of this research is to further develop EHD conduction pumping by exploring its use for terrestrial and space applications. In the next study, new EHD conduction pumps were designed and fabricated for use as a smart flow distribution mechanism for a microchannel evaporator. Microchannel heat exchangers have advantages in compactness and the ability to remove very high heat fluxes but are susceptible to two-phase flow instabilities. EHD conduction 29 was demonstrated to be capable of effectively redistributing flow in a parallel microchannel evaporator, allowing for optimization of the heat exchanger, and recovery from a near dry out condition was demonstrated at 77.5 W/cm2. In another study, novel helical EHD conduction pumps were developed via additive manufacturing methods, using SLS, SLA, and silk screen printing. This pumping design is also the first of its kind and can generate a swirling flow for thermal enhancement. This pump was numerically simulated, and a test loop was built to demonstrate its performance, achieving local heat transfer coefficient improvements of up to 70%. The final main goal of this research is to further the understanding of EHD conduction pumping coupled with dielectrophoretic vapor removal for sustaining thin liquid film flow boiling in microgravity. In conjunction with the low mass of EHD-based pumping mechanisms, the pumping of thin liquid films can further reduce the overall weight of the system. Experiments were conducted to explore the effect of non-condensable gas on the performance of electrically driven liquid film flow boiling and found that the application of electric fields can mitigate the thermal performance losses. Increasing concentrations of non-condensable gas significantly improved the critical heat flux of the system, however the power consumption also increased due to the humidity present in air. The effect of pulsating voltage was also studied for EHD conduction liquid film pumping and dielectrophoresis in isolation and synchronously. Pulsation was shown to impact the liquid film flow behavior through imaging data, and improvements in single phase heat transfer and boiling critical heat flux were observed. These studies represent the first steps in the development of an electrically driven radial pulsating heat pipe as a next generation thermal management approach. From the presented studies, the body of knowledge and understanding of EHD conduction pumping applied for thermal management of electronics in space has been expanded. Though this research is targeted for electronics cooling in space, utilization of EHD conduction pumping for enhancement of existing terrestrial systems, such as vapor-compression cycle refrigeration, has the potential for improving the overall system efficiency. There is also the potential to improve the thermal performance of electronics, such as those in data centers found throughout the world. Thus, the future implementation of EHD has the potential for significant cost savings, and reduction in carbon footprint.

Creator