Browsing by Author "Richard R. Johnson, Committee Member"

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Experimental Evaluation of HVAC Energy Conservation Options for Modular Classrooms
(2005-11-29) Freeman, Jacob Thomas; James W. Leach, Committee Chair; Herbert M. Eckerlin, Committee Member; Richard R. Johnson, Committee Member
In this study, three modular classrooms at one school campus and two modular classrooms at a second campus were monitored to measure the effectiveness of the heating ventilating and air conditioning systems to provide healthy interior conditions and to compare the energy savings made possible by several types of HVAC system design improvements. All of the classrooms are similar in construction and all are located in similar environments near Raleigh, NC. One classroom at each campus has a water source heat pump designed specifically for mobile buildings. The water exchanges heat with the earth and the atmosphere through a PVC heat exchanger that lies on top of the ground in the crawl space. The three classrooms at one campus are occupied throughout the summer, while the two classrooms at the other campus are not occupied for approximately two months during the summer. At the campus with year round occupation, one air source heat pump is monitored in standard configuration. The other air source heat pump is equipped with an exhaust-to-inlet air heat exchanger to recover energy in the ventilation air. The last classroom at this campus with the water source heat pump is also equipped with an exhaust-to-inlet air heat exchanger. At the campus with two months of summer vacation, the air source heat pump does not have energy recovery ventilation but has a nighttime setback thermostat. The water source heat pump at this campus also does not have energy recovery ventilation but has a nighttime setback thermostat.
Modeling Fluid Flows and Heat Transfer in Industrial Processes Using GOTHIC Software
(2003-08-18) Cooper, Phillip Shawn; Herbert M. Eckerlin, Committee Member; Richard R. Johnson, Committee Member; James W. Leach, Committee Chair
Energy conservation measures in manufacturing plants and commercial facilities often involve modifications to convective processes. Examples of equipment used to carry out these processes include heating, ventilating, and air-conditioning equipment, refrigeration equipment, dust collection systems, drying and curing ovens, kilns, and melting cupolas. Because requirements and operating conditions change over time, there is often a need to modify existing equipment. The potential for energy savings may be very large, but engineers and plant managers are still reluctant to take action because it is not easy to predict the overall effects of proposed changes in such complex systems. This work documents a case study to demonstrate how GOTHIC may be employed to improve a typical industrial process. GOTHIC is a general purpose thermal-hydraulics computer program originally developed for design, licensing, safety and operating analyses of nuclear power plant containments and other confinement buildings. It is a state-of-the-art program that solves conservation equations for mass, momentum, and energy for multi-component, multi-phase flows. The phase balance equations are coupled by mechanistic models for interface mass, energy and momentum transfer that cover the entire flow regime from bubbly flow to film/drop flow, as well as single phase flows. The code is user-friendly, and is capable of modeling systems with many components. The case study evaluates proposed changes to a forced convection system for cooling urethane foam logs. The logs, which are about 30 ft2 in cross section by 200 ft in length, form when liquid chemicals react on an enclosed conveyor. The exothermic reaction continues for a few hours after the log is formed. Therefore, about 25 logs are stored in racks at one time and cooled by refrigerated air. A ventilation system removes fumes from the storage area. The system is inefficient and costly to operate because the cooling airflow pattern is not optimized, and because cool air is removed by ventilation system. The GOTHIC code makes it possible to easily and quickly predict flows and air temperatures in the complex geometry, transient temperatures within the logs, and to optimize the cooling system. Model predictions are compared to experimental data.
Optimization of a Geothermal Heat Pump System with Aboveground Water Storage
(2003-04-08) Forrest, Andrew Ryan; Richard R. Johnson, Committee Member; Herbert M. Eckerlin, Committee Member; James W. Leach, Committee Chair
This study investigates and recommends design improvements for a geothermal heat pump system with aboveground water storage. It builds on a previous study that tested a 3-ton geothermal heat pump on a mobile classroom at Wilson Mills Elementary School in Johnston County, North Carolina. The previous experiment used two 1,000 gallon polyethylene bladders filled with saltwater for freeze protection. Using TRNSYS, a model of the original system was constructed and validated by comparing model predictions to measured performance. TRNSYS models of several new designs and theories were constructed to evaluate potential design improvements. The system models were evaluated based on predicted performance for a typical meteorological year, and on other criteria such as initial cost, maintenance, and portability. This resulted in a new optimized system design in which the water storage volume is reduced to 120 gallons, and the predicted electrical energy requirements are about two-thirds of those of an air source heat pump. The predominant design improvement to the system is the implementation of a heat exchanger constructed of PVC pipe. Detailed design, costs, and assembly procedures for the PVC heat exchanger are presented in this study.