Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Analysis of energy and savings of using ground loop or steam to change temperature of the bulding heat pump loop in Norm Asbjornson Hall(Montana State University - Bozeman, College of Engineering, 2023) Kuikel, Shraddha; Chairperson, Graduate Committee: Kevin AmendeThe need for efficient and sustainable environmental conditioning systems in buildings has become increasingly important in the face of rising energy costs and environmental concerns. This thesis aims to assess the optimization of the control logic to maximize energy savings and costs associated with utilizing ground loop or steam to modify the temperature of a heat pump loop in ground source heat pumps (GSHP) in Norm Asbjornson Hall (NAH) building at Montana State University (MSU). The study begins by providing a comprehensive review of existing literature on GSHP systems, their working principles, and the various methods employed to alter the temperature of the heat pump loop. The research methodology involves determining the conditions under which it is economically viable to operate ground loops and/or a steam heat exchanger to maintain the heat pump loop temperature within a set operating range. This is done by deriving an equation that utilizes the coefficient of performance (COP) and entering water temperature (EWT) of the heat pump loop. Energy and cost analysis is then conducted to assess the energy efficiencies for different cases. The findings reveal that both steam and ground loops can effectively alter the temperature of heat pump loops, providing enhanced temperature control and increased energy efficiency. The analysis shows that each strategy does have important financial and environmental implications, nevertheless. Due to the equipment, infrastructure, and operational expenditures, steam injection is primarily utilized to raise the loop's temperature for heating mode only, and at extreme situations when the ground loop cannot provide enough energy to maintain the heat pump loop temperatures. However, compared to steam injection, ground loops, which can be used for both heating or cooling, offer significant energy savings and lower long-term maintenance costs, albeit needing a sizable initial investment. In summary, the thesis explores how to optimize control logic to save energy and costs using ground loop or steam to adjust building heat pump loop temperature. The study evaluates energy, cost, and environmental impact of the proposed control logic optimization approach. The findings aim to provide insights into informed decision-making regarding the adoption of this alternative method.Item The design and testing of an axial condenser fan(Montana State University - Bozeman, College of Engineering, 2021) Kirk, David Michael; Chairperson, Graduate Committee: Kevin AmendeAxial or propeller fans are a subset of turbomachinery whose application is prevalent in everyday life. In the case of heating, ventilation, air conditioning, and refrigeration (HVAC&R), fans can be a large source of inefficient energy consumption due to their physical operating nature. With the global push for more efficient systems, components of HVAC&R equipment such as fans have become a focal point for researchers in academia and industry alike. Technological improvements in research equipment such as computational fluid dynamics (CFD) and additive manufacturing play a large role in achieving these improved efficiencies. The goal of this research is to improve the efficiency of an axial fan intended for cooling a micro-channel heat exchanger that is used in rooftop condenser units. A higher efficiency retrofit fan was iteratively designed using a commercial CFD software package, Star CCM+, which constitutes much of the research conducted in this project. The iterative models show that significant efficiency gains can be achieved through incremental alterations of classical fan blade geometry elements such as pitch, camber, skew, cross section loft path, chord length, thickness, etc. A physical model of the fan design thought to be the optimal choice for experimental analysis was 3D printed and tested using an AMCA Standard 210 setup. Upon analysis of the physical test results, several discrepancies between simulated and actual results were discovered, highlighting the importance of CFD model validation in the design process. Despite the efficiency gains and advancements in user-friendly packaged software, the simulation underpredicted the power demand and incorrectly depicted the fan's performance at critical operating points showing that improper usage of these experts' tools can inadvertently lead to developed solutions with significant error. While the designed fan achieves an improved peak static efficiency and volumetric flow rate of 53.9% and 4334 CFM respectively, it ultimately did not meet the operating parameters of the specific unit it was designed for and further improvements to the CFD model are needed.Item Performance characterization of shallow helical ground heat exchangers for ground source heat pump applications(Montana State University - Bozeman, College of Engineering, 2016) Alvarez Revenga, Francisco Javier; Chairperson, Graduate Committee: Kevin AmendeThe use of the ground as heat source or sink medium for heating and cooling the human built environment has the potential of saving energy and reducing greenhouse gas emissions significantly. One of the main components of this system is the heat exchanger that is buried in the ground. This thesis explores the performance of a specific type of ground heat exchanger (GHE): the shallow vertical helical GHE. This type of GHE occupies considerably less land when compared to horizontal configurations and are less influenced by outdoor temperature and weather conditions. When compared to traditional deep vertical U-tube probes, savings on drilling costs can be significant. However, performance data and design information is limited for these types of heat exchangers, which has limited their adoption amongst ground source heat pump (GSHP) system designers and installers. Various in-situ heating and cooling tests were performed at a residence in Bozeman, Montana, with a system containing three helical GHEs. The heat exchangers are coupled with a GSHP with variable capacity compressors. Moreover, a recently developed numerical model (named CaRM-He) was used to compare the experimental results with the simulated performance. The model is based on the analogy between thermal and electrical phenomena, where the domain (comprised of GHE, surrounding ground, grouting material, and heat carrier fluid) is discretized as a linked network of thermal nodes with thermal capacitances and resistances. Heat exchanger outlet temperature as predicted by CaRM-He model was compared with experimental data, resulting in different degrees of accuracy. This research presents a method to characterize the performance of these types of GHEs, and a comprehensive analysis of uncertainties and sources of error inherent to in-situ testing. Also, it is recommended that the model is improved to include extraneous heat inputs and horizontal runs. Still however, the advantages of this ground coupling method and the possibility to predict its performance make the helical GHE an interesting alternative for the geothermal designer.Item Characterization of airflow through an air handling unit using computational fluid dynamics(Montana State University - Bozeman, College of Engineering, 2015) Byl, Andrew Evan; Chairperson, Graduate Committee: Erick JohnsonHVAC equipment manufacturers spend a considerable amount of time and effort updating existing product lines in order to meet the ever-increasing demand for energy efficient systems. As a major part of HVAC systems, an air handling unit (AHU) controls the airflow through the system and regulates the indoor air quality. Plenum fans used in AHUs inherently produce a rotational airflow, which can create highly unstructured airflow as it enters a heat exchanger located downstream. This in turn leads to lower heat transfer rates and premature heat exchanger failure. As such, airflow uniformity is presently regarded as an important consideration in designing these systems. Through advancements in computer technologies within the last decade, computational fluid dynamics (CFD) has become an economical solution allowing HVAC equipment designers to numerically model prototypes and reduce the time required to optimize a given design and identify potential failure points. While CFD analysis also offers the ability to visualize and characterize the airflow through an AHU system, it has often been used to model individual components such as fans or heat exchangers without analyzing them as a single unit. This work presents the CFD models used to characterize the airflow within an AHU in order to aid in understanding the effects that flow uniformity has on heat exchanger performance. The airflow uniformity was analyzed over a range of volumetric flow rates, and experiments were used to validate the baseline simulations. Different baffle designs were then added into the validated simulations to observe their influence on both airflow uniformity and heat transfer performance. Results indicate that airflow uniformity is, by itself, an insufficient metric to predict heat transfer performance. Additionally, steady-state CFD analyses performed on simplified geometries are shown to provide a sufficient model to be used for further optimization, when the inlet conditions are well specified.Item Green's function simulation method for earth-air heat exchangers(Montana State University - Bozeman, College of Engineering, 2015) Denowh, Chantz Michael; Chairperson, Graduate Committee: David A. Miller; Kevin Amende (co-chair)Earth-air heat exchangers (EAHXs), or earth-tubes, decrease building heating/cooling loads by pre-conditioning supply air in underground pipes. Air circulates underground to exchange heat with the surrounding soil before entering the building. The concept is fairly simple, but the field currently lacks fundamental information of the energy interactions in common EAHX installations. This identifies the need of a model framework inclusive of all EAHX design considerations, time-dependent climate conditions, and EAHX types to support the completion of this fundamental information. The EAHX types in this study include installations under locations free of structures (under yard) and under foundational slabs (under slab). This research develops the groundwork of this framework through a versatile model using the Green's Function method and numeric integration. The Green's Function method incorporates the majority of time-dependent heat transfer mechanisms surrounding EAHXs through long and short time solution components. The long time component calculates the initial soil temperature distribution in the under yard, non-radiant under slab, and radiant under slab installations. The under yard simulations were successfully validated using experimental soil temperature data from around the United States. The non-radiant under slab temperatures produced unrealistic results in some locations, but the novel Green's Function method in this location has significant potential for under slab EAHX applications. Results from the long time solution feed into the short time solution as a space-dependent initial condition. The short time solution uses a finite difference approach to calculate the heat transfer along the EAHX length. This method was validated using computation fluid dynamics with good agreement. The two components work together to quickly simulate a large number of EAHX installations. The research includes an example optimization procedure to demonstrate the framework's versatility. It successfully optimized the EAHX lengths for 95% effectiveness in cooling on the hottest day of the year in 15 locations around the United States.Item A simulation approach to the thermal-hydraulic design of cored ceramic brick regenerative heat exchangers(Montana State University - Bozeman, College of Engineering, 1977) Upshaw, Gary AlanItem Microbially influenced corrosion of stainless steel 304 under halogenated fluids(Montana State University - Bozeman, College of Engineering, 1991) Agrawal, VivekItem Design of a high temperature falling bed air preheater for direct coal-fired MHD power generation using liquid slag droplets(Montana State University - Bozeman, College of Engineering, 1977) Prill, Raymond LeeItem Seed run-off in an MHD air preheater(Montana State University - Bozeman, College of Engineering, 1978) Nash, Rosanne MarieItem Experimental measurement of biofilm in a heat exchanger(Montana State University - Bozeman, College of Engineering, 1989) Heal, Douglas Wayne