ORCID Identifier(s)

0000-0002-7577-1892

Graduation Semester and Year

2021

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering

Department

Civil Engineering

First Advisor

Xinbao Yu

Abstract

Each year, ice and snow adversely impact U.S. transportation infrastructure during the cold season, causing an extensive impact on the U.S. economy. Bridges are key elements in the transportation network and the most vulnerable sections of the road to ice and snow. Conventional snow and ice removal system (CSRS) is proven not to be a satisfactory solution as it causes induced damages and issues, such as accelerating bridge deck corrosion, safety issues, travel delays, and environmental damages. Thus, the geothermal heat pump de-icing system (GHDS) is introduced as a sustainable solution for bridge deck de-icing, which utilizes renewable geothermal energy and prevents the problems associated with CSRS. Current GHDS designs mostly rely upon embedded hydronic loops in concrete decks. To extend the GHDS for existing bridges, a new external hydronic deck has been developed, which employs attached hydronic heating pipes to the bottom surface of the bridge deck. In this study, a novel external geothermal heating system is developed and implemented on a full-scale bridge deck, located in the Dallas-Fort Worth metroplex in Texas, USA. Primarily, this study presents the design and implementation procedure of a novel external geothermal heating system on a full-scale bridge deck for de-icing operations in field conditions for the first time. It tests and analyzes the system's heating performance and the bridge deck's thermal response under multiple winter events. The details and information pertaining to the design and construction of the hydronic loops, a ground heat exchanger (GHE), and the monitoring system, are presented and can be pivotal for the designers of similar projects. The test results showed that the system was successful in de-icing the bridge deck and maintaining the bridge deck surface temperature above freezing in the event with a minimum ambient temperature of -6.2 °C. Experimental results also indicated that the external heating system was able to transfer about 55% of the supplied heat to the bridge deck surface. Moreover, this study investigates the thermal and energy performance of the 131 m borehole heat exchanger as well the subsurface ground temperature distribution during heat injection and extraction due to bridge solar collector and de-icing tests. According to the result, the heat injection by bridge solar-collector test resulted in a noticeable rise in the ground temperature surrounding the heat exchangers. The result proved that the stored thermal energy can be preserved for utilization in the winter de-icing test. Also, the field tests’ results proved the feasibility of the bridge solar collector to address the thermal imbalance issue in the ground. Moreover, in this study, a 3D transient FE model is developed in COMSOL Multiphysics to assist in further investigation of the GHE performance and overcome the limitation of the experimental tests. As one of the disadvantages of the finite element (FE) models is huge computational time, a computationally efficient model is developed which sacrifices the temperature distribution inside the borehole and simulates the borehole wall temperature with less computational time, a high level of accuracy, and convenient meshing. The proposed model is verified against the experimental data and was found to be as accurate as of the conventional model in simulating outlet fluid temperature, borehole wall temperature, and soil temperature surrounding the borehole. The outcome of the analysis confirmed, application of the proposed model greatly reduced the required number of mesh elements and consequently computational time in comparison to the conventional model. Finally, this study performs a scenario-based life-cycle cost-benefit analysis (LCCBA) on the geothermal heat pump de-icing system (GHDS) to investigate the economic viability of this system for the case of North Texas. The result of the base case analysis showed the benefits of the GHDS outweigh its costs. In addition, the results of the sensitivity analysis, using the Monte Carlo Simulation (MCS), indicated traffic flow enhancement is the most dominant variable affecting the overall result. However, for the daily traffic volume of 24000 vehicles, the benefits were estimated to be 2.32 times greater than the costs with 95% reliability. Generally, the analysis output demonstrated, for the bridges with a minimum daily traffic volume of 7000 vehicles, the application of the GHDS is economically viable.

Keywords

Bridge de-icing, Geothermal de-icing system, Geothermal energy, Ground temperature, Hydronic heating system, Ground heat exchangers, Finite element modeling (FEM), Life-cycle cost-benefit analysis (LCCBA)

Disciplines

Civil and Environmental Engineering | Civil Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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