Browsing by Subject "Cooling"

Now showing 1 - 4 of 4
  • Thumbnail Image
    ItemOpen Access
    Constructal Vascularized Structures for Cooling and Mechanical Strength
    (2013) Cetkin, Erdal

    This dissertation shows how to use Constructal theory in order to design vascular structures with high cooling performance and mechanical strength. The vascular structures consist of grid, tree and hybrid (grid + tree) designs. The four chapters show how the cooling performance and mechanical strength can be increased by varying the vascular structure embedded in a plate for different models and boundary conditions. Chapter 2 shows that the fastest spreading or collecting flow (i.e. the steepest S curve) is discovered by allowing the tree architecture to morph freely. The angles between the lines of the invading tree architecture can be morphed (changed, selected) such that the overall flow proceeds along the fastest route, covering the greatest territory at any moment. Chapter 3 shows development of vascular designs that provide cooling and mechanical strength at the same time. This concept is illustrated with a circular plate vascularized with embedded channels. Chapter 4 shows how vascular design controls the cooling and mechanical performance of a solid slab heated uniformly and loaded with uniform pressure. Chapter 5 shows that a plate heated by a randomly moving beam can be cooled effectively by fluid that flows through a vasculature of channels embedded in the plate. In sum, constructal design governs the evolution of flow structures that offer flow access and mechanical strength at the same time.

  • Thumbnail Image
    ItemOpen Access
    Effect of Size on Ground-Coupled Heat Pump Performance
    (2013) Alalaimi, Mohammad Ali

    Here we document and explain a general trend in the performance of refrigeration and heat pump systems: larger installations are more efficient. We show analytically why the performance of the system must increase with the size of the installation. The second law efficiency of refrigeration systems must increase with their size. We also show that the power requirement a ground-coupled heat pump system must decrease as the size of the ground heat exchanger increases. From these two trends emerges the trade off between the size of the heat pump and the size of the ground heat exchanger. The challenge is to find the optimum size of the ground-coupled heat pump. We show numerically the optimum heat pump size and the ground heat exchanger size that correspond to minimum total power requirement subject to a cost constraint.

  • Thumbnail Image
    ItemOpen Access
    Electric Power Plant Water Use in North Carolina: Forced Evaporation and Emission Controls
    (2010-04-30T13:51:18Z) Morton, Victoria
    The link between water use and electricity generation is very strong and largely omitted from the public policies aimed at sustainable generation of electricity. Electricity is required for treating and pumping water to its destination, and water is required for electricity generation at thermoelectric power plants for cooling purposes, and for the operation of environmental control devices that reduce air emissions. North Carolina is ranked 9th in the United States for electricity total net production, according to the Energy Information Administration. Thermoelectric power freshwater withdrawals far outstrip all other water withdrawal categories; by the year 2000, thermoelectric power freshwater withdrawals were approaching 8,000 million gallons per day, and as the population continues to grow in North Carolina, that number can only be expected to increase. They make some of the largest water withdrawals in the state of North Carolina, but they only consume approximately 3% of the water they intake. The consumptive use percentage of 3% is misleading because it doesn’t take into account forced evaporation. As mentioned previously, power plants require intake water to use for cooling purposes in the electricity generation process. The withdrawn cooling waters, once run through the plant, are returned to rivers/lakes at a higher temperature than the ambient water temperature. This higher temperature water causes additional evaporation (forced evaporation) from the river/lake. Forced evaporation should be of particular concern to North Carolina due to the severe droughts that have occurred in the region in recent history which threaten energy production as well as other water uses (ex. drinking water supply). In this project we find that forced evaporation represents an average 22% increase in power plant water consumption in North Carolina, when compared to water consumption occurring during electricity generation on-site. We also look at the impact that air emission controls have on the plants water consumption. If carbon emissions are required to be controlled in the future, then water use at all power plants will increase, on average, approximately 5%. The water lost to forced evaporation and emissions controls will add additional strain to power plants located in drought prone regions.
  • Thumbnail Image
    ItemOpen Access
    Event Detection Using Linear Regression and Historical Weather Data
    (2015-04-23) Garafola, Nicholas
    The Research Triangle Institute (“RTI”) seeks to minimize water consumption by automating the process of detecting water and energy over- and under-consumption events associated with cooling systems. The Central Utility Plant (“CUP”), which serves roughly 25% of gross built area on RTI’s main campus, has contributed to past over-consumption events due to mechanical failure of cooling tower water makeup float valves. RTI’s facilities team would like to assemble data and examine the relationship between atmospheric conditions and water consumption. This project entails development of a data cleaning and analysis tool based in Microsoft Excel that allows RTI facilities and operations teams to periodically update a predictive model in response to changing facility parameters that are external to the model, including changes in building footprint, occupancy and HVAC settings. The final deliverable includes a user guide that explains the functions of the Excel tool as well as the limitations of predictions based on linear regression models.