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The experiments detailed in this thesis give necessary preliminary information for analyzing the theoretical potential of direct exhaust pulse energy harvesting through expander devices. A detailed review of pertinent literature determined that there has been little specific focus on directly converting exhaust pulse energy into useful power. Crank position resolved exhaust pressure was measured as engine load and speed were varied to quantify their influences. Potential theoretical improvements average a 15.6% increase in overall fuel conversion efficiencies while indicated power can potentially be increased by an average of 14.3% for the operating conditions tested. A potential increase of up to 20% in indicated specific fuel consumption was shown. With increasing regulations on combustion engine efficiencies, emissions, and fuel requirements, the ability to reduce waste energy through improving existing waste energy recovery (WER) technologies and proposing novel WER strategies that maximize WER have the potential to be extremely valuable.

The development and implementation of technologies that improves Heating Ventilation & Air Conditioning (HVAC) system efficiency, including unique waste heat recovery methods, are sought while considering financial constraints and benefits. Recent studies have found that through the use of advanced waste heat recovery systems, it is possible to reduce building’s energy consumption by 30%. Oscillating heat pipes (OHP) exists as a serpentine-arranged capillary tube, possesses a desirable aerodynamic form factor, and provides for relatively high heat transfer rates via cyclic evaporation and condensation of an encapsulated working fluid with no internal wicking structure required. In last two decade, it has been extensively investigated for its potential application in thermal management of electronic devices. This dissertation focuses on the application of OHP in waste heat recovery systems. To achieve the goal, first a feasibility study is conducted by experimentally assessing a nine turn copper-made bare tube OHP in a typical HVAC ducting system with adjacent air streams at different temperatures. Second, for a prescribed temperature difference and volumetric flow rate of air, a multi-row finned OHP based Heat Recovery Ventilator (OHP-HRV) is designed and analyzed for the task of pre-conditioning the intake air. Additionally, the energy and cost savings analysis is performed specifically for the designed OHP-HRV system and potential cost benefits are demonstrated for various geographical regions within the United States. Finally, an atypically long finned OHP is experimentally investigated (F-OHP) under above prescribed operating condition. Helical fins are added to capillary size OHP tubes at a rate of 12 fins per inch (12 FPI), thereby increasing the heat transfer area by 433%. The coupled effect of fins and oscillation on the thermal performance of F-OHP is examined. Also, F-OHP’s thermal performance is compared with that of bare tube OHP of similar dimension and operating under similar condition. It was determined that OHP can be an effective waste heat recovery device in terms of operational cost, manufacturability, thermal and aerodynamic performance. Moreover, it was also determined that OHP-HRV can significantly reduce energy consumption of a commercial building, especially in the winter operation.

The ever-growing demand for cyber-physical infrastructures has significantly affected worldwide energy consumption and environmental sustainability over the past two decades. Although the average heat load of the computing infrastructures has increased, the supportive capacity of cooling infrastructures requires further improvement. Consequently, energy-efficient cooling architectures, real-time load management, and waste heat utilization strategies have gained attention in the data center (DC) industry. In this dissertation, essential aspects of cooling system modularization, workload management, and waste-heat utilization were addressed. At first, benefits of several legacy and modular DCs were assessed from the viewpoint of the first and second laws of thermodynamics. A computational fluid dynamics simulation-informed thermodynamic energy-exergy formulation captured equipment-level inefficiencies for various cooling architectures and scenarios. Furthermore, underlying reasons and possible strategies to reduce dominant exergy loss components were suggested. Subsequently, strategies to manage cooling parameters and IT workload were developed for the DCs with rack-based and row-based cooling systems. The goal of these management schemes was to fulfill either single or multiple objectives such as energy, exergy, and computing efficiencies. Thermal models coupled to optimization problems revealed the non-trivial tradeoffs across various objective functions and operation parameters. Furthermore, the scalability of the proposed approach for a larger DC was demonstrated. Finally, a waste heat management strategy was developed for new-age infrastructures containing both air- and liquid-cooled servers, one of the critical issues in the DC industry. Exhaust hot water from liquid-cooled servers was used to drive an adsorption chiller, which in turn produced chilled water required for the air-handler units of the air-cooled system. This strategy significantly reduced the energy consumption of existing compression chillers. Furthermore, economic and environmental assessments were performed to discuss the feasibility of this solution for the DC community. The work also investigated the potential tradeoffs between waste heat recovery and computing efficiencies. / Thesis / Doctor of Philosophy (PhD)

Analytical, closed-form solutions governing thermoelectric behavior are derived. An analytical model utilizing a thermal circuit is presented involving heat transfer into, through, out of, and around a thermoelectric device. A nondimensionalization of the model is presented. Linear heat transfer theory is applied to the model to obtain a series of closed form equations predicting net power output for the thermoelectric device. Fluid streams flowing through shrouded heat sinks with square pin fins are considered for the thermal pathways to and from the device. Heat transfer and pressure drop are characterized in a manner conducive to an analytical model using previously published experimental results. Experimental data is presented which validates and demonstrates the usefulness of the model in predicting power output for commercially available thermoelectric generators. A specific design for a thermoelectric power harvester is suggested consisting of a pattern of thermoelectric generators. An economic model for calculating payback time is developed. An optimization process is demonstrated that allows for the payback time of such a system to be minimized through optimization of the physical design of the system. It is shown that optimization of the thermal pathways dramatically reduces payback time. Optimized design of a system is discussed in light of theoretical cases with feasible payback times.

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