Wayne L. Staats

Design of an Integrated Loop Heat Pipe Air-Cooled Heat Exchanger for High Performance Electronics

The continually increasing heat generation rates in high performance electronics, radar systems and data centers require development of efficient heat exchangers that can transfer large heat loads. In this paper, we present the design of a new high-performance heat exchanger capable of transferring 1000 W while consuming less than 33 W of input electrical power and having an overall thermal resistance of 0.05 K/W. The low thermal resistance is achieved by using a loop heat pipe with a single evaporator and multiple condenser plates that constitute the array of fins. Impellers between the fins are driven by a custom permanent magnet synchronous motor in a compact volume of 0.1 × 0.1 × 0.1 m to maximize the heat transfer area and reduce the required airflow rate and electrical power. The design of the heat exchanger is developed using analytical and numerical methods to determine the important parameters of each component. The results form the basis for the fabrication and experimental characterization that is currently under development.

A Technique for Performing Electrical Impedance Myography in the Mouse Hind Limb: Data in Normal and ALS SOD1 G93A Animals

Objective To test a method for performing electrical impedance myography (EIM) in the mouse hind limb for the assessment of disease status in neuromuscular disease models. Methods An impedance measuring device consisting of a frame with electrodes embedded within an acrylic head was developed. The head was rotatable such that data longitudinal and transverse to the major muscle fiber direction could be obtained. EIM measurements were made with this device on 16 healthy mice and 14 amyotrophic lateral sclerosis (ALS) animals. Repeatability was assessed in both groups. Results The technique was easy to perform and provided good repeatability in both healthy and ALS animals, with intra-session repeatability (mean ± SEM) of 5% ±1% and 12% ±2%, respectively. Significant differences between healthy and ALS animals were also identified (e.g., longitudinal mean 50 kHz phase was 18±0.6° for the healthy animals and 14±1.0° for the ALS animals, p = 0.0025). Conclusions With this simple device, the EIM data obtained is highly repeatable and can differentiate healthy from ALS animals. Significance EIM can now be applied to mouse models of neuromuscular disease to assess disease status and the effects of therapy.

A portable air jet actuator device for mechanical system identification.

System identification of limb mechanics can help diagnose ailments and can aid in the optimization of robotic limb control parameters and designs. An interesting fluid phenomenon--the Coandă effect--is utilized in a portable actuator to provide a stochastic binary force disturbance to a limb system. The design of the actuator is approached with the goal of creating a portable device which could be deployed on human or robotic limbs for in situ mechanical system identification. The viability of the device is demonstrated by identifying the parameters of an underdamped elastic beam system with fixed inertia and stiffness and variable damping. The nonparametric compliance impulse response yielded from the system identification is modeled as a second-order system and the resultant parameters are found to be in excellent agreement with those found using more traditional system identification techniques. The current design could be further miniaturized and developed as a portable, wireless, unrestrained mechanical system identification instrument for less intrusive and more widespread use.

Investigation of a Multiple Impeller Design for a High Performance Air-Cooled Heat Sink

A high-performance air-cooled heat sink that incorporates a novel heat pipe with multiple parallel condenser layers and interdigitated blower impellers is presented. A flow circuit model was developed in order to predict the air flow performance of a 15-layer impeller system using experimental measurements from a single layer. A 15-layer impeller system was constructed to validate the flow circuit model. The performance of the multi-layer system was investigated by using a hot wire anemometer to compare flow between layers and by measuring the inflation rate of a bag enclosing the air outlets. This work addresses important issues that allow the extension of the air flow modeling and experimental results from a single impeller design to a multilayer stack of impellers operating in parallel and sharing a common inlet.Copyright

Design of a Wireless, Passive, Single-Use Emergency Call System

In order to improve patient access to nurses during emergencies, a wireless wrist-mounted call button system was developed. The goal of this project was to create a simple, easy-to-use system that features a completely passive, wireless call button. Three major problems in existing systems – inability for patients to locate or reach the button, unnecessary user interface complexity, and the introduction of a potential vector for hospital-contracted illness – were addressed in the design. The wireless nature of the device ensures that it is always near the patient. A single-button interface considerably simplifies its use in comparison to multi-button systems, eliminating the possibility of incorrect button presses. Finally, the proposed call button uses inexpensive technologies and can be manufactured for such a low cost that it can be offered as a single-use device, eliminating the possibility of patient-topatient disease transmission. Using radio-frequency identification (RFID) technology, patients are able to call for hospital staff from any location in the hospital that is covered by readers. The call button uses a passive RFID tag that can be turned on or off by a mechanical switch. A second tag is used to notify the system when a patient is out of range. The design was prototyped and tested, and future improvements are suggested.

Development and Testing of an Integrated Sandia Cooler Thermoelectric Device (SCTD).

This report describes a FY14 effort to develop an integrated Sandia Cooler T hermoelectric D evice (SCTD) . The project included a review of feasible thermoelectric (TE) cooling applications, baseline performance testing of an existing TE device, analysis and design development of an integrated SCTD assembly, and performance measurement and validation of the integrated SCTD prototype.

Development of the Sandia Cooler.

This report describes an FY13 effort to develop the latest version of the Sandia Cooler, a breakthrough technology for air-cooled heat exchangers that was developed at Sandia National Laboratories. The project was focused on fabrication, assembly and demonstration of ten prototype systems for the cooling of high power density electronics, specifically high performance desktop computers (CPUs). In addition, computational simulation and experimentation was carried out to fully understand the performance characteristics of each of the key design aspects. This work culminated in a parameter and scaling study that now provides a design framework, including a number of design and analysis tools, for Sandia Cooler development for applications beyond CPU cooling.

Integration of a Multiple-Condenser Loop Heat Pipe in a Compact Air-Cooled Heat Sink

We present the characterization of a compact, high performance air-cooled heat sink with an integrated loop heat pipe. In this configuration, heat enters the heat sink at the evaporator base and is transferred within the heat pipe by the latent heat of vaporization of a working fluid. From the condensers, the heat is transferred to the ambient air by an integrated fan. Multiple condensers are used to increase the surface area available for air-cooling, and to ensure the equal and optimal operation of the individual condensers, an additional wick is incorporated into the condensers. We demonstrated with this design (10.2 cm × 10.2 cm × 9 cm), a total thermal resistance of less than 0.1 °C/W while dissipating a heat load of 500 W from a source at 75 °C. Furthermore, constant thermal resistance was observed in the upright as well as sideways orientations. This prototype is a proof-of-concept demonstration of a high performance and efficient air-cooled heat sink design that can be readily integrated for various electronics packaging and data center applications.© 2013 ASME

Scaling the performance of an air-cooled loop heat pipe with the addition of modular condensers

We report the performance of a novel air-cooled loop heat pipe with a planar condenser and planar evaporator, and the performance improvement expected from a multiple-condenser version of the device. The condensers are developed in a modular design, and the heat pipe is configured to allow the installation of multiple, stacked condensers. An analytical model is developed to predict the scaling of convective thermal resistance with the addition of condensers. The result of the model is compared with the thermal resistance measured from a single-condenser prototype (0.18-0.23°C/W), and the effect of condenser count on thermal resistance is discussed. The heat pipe is intended for the integration into a high-performance air-cooled heat sink.