Smith EVS 300 - Heat Losses in the Smith College Steam Tunnel

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1 Heat Losses in the Smith College Steam Tunnel EVS 300 Project Joyce Cheung ‘09 Submitted to: Prof. L. David Smith Environmental Science & Policy Seminar Smith College 8 May 2009 2Abstract The Smith College Steam Tunnel transports steam generated in the Physical Plant to student houses and academic buildings on campus for heating purposes. However, heat is lost in this process because the existing pipe insulation is not 100% efficient. Therefore, this project aims to (1) estimate the amount of heat that is lost when steam is transported from the Smith College Physical Plant to other buildings on campus, (2) determine the percentage decrease in heat loss when insulation is added, and (3) discern whether a heat exchanger unit is feasible. After a site study of the steam tunnel, it was estimate that approxima tely 20W of power is released per foot of insulated steam pipe. This heat loss can be diminished by adding insulation, but can also be used to heat buildings such as the Lyman Plant House & Conservatory. Mineral fiber was rendered as a more efficient insulator and if the steam pipes were retrofitted with 1.5 in of this material on top of the existing asbestos insulation, energy savings can amount to $294,000 per year. In terms of installing a heat exchanger to heat the plant house, there is insufficient space for this unit because the heat exchanger requires a cross sectional area of 170ft2, yet the basement of Lyman is only has the available space of 45ft2. However, both options should still be taken into consideration as a long‐term investment for Smith College to decrease steam production. 3Acknowledgements I sincerely express my gratitude to all who have me along this project. Specifically, I recognize Rob Nicholson, the conservatory manager at the Botanic Garden Lyman Plant House, for proposing this project. I would like to thank Todd Holl and, the energy manager for the Five Colleges, Inc., for his time and contribution to my heat loss analysis. I want to acknowledge Denise McKay, an assistant professor of engineering, who had guided me in my heat exchanger calculations; Fran Raymond, the chief engineer at the Facilities Management, for providing the map of the steam tunnels; and L. David Smith, the director of the Environmental Science & Policy Program at Smith College, for giving me the foundation to initiate this project. You have provided me with invaluable information, and I truly appreciate your help. Sincerely, Joyce Cheung 4Table of Contents I. Introduction ..................................................................................................................... 5 II. Methodology................................................................................................................... 9 III. Results.......................................................................................................................... 11 IV. Discussion .................................................................................................................... 17 V. Literature Cited............................................................................................................. 19 VI. Appendices .................................................................................................................. 20 Appendix A: Map of the Smith College Steam Tunnel......................................... 20 Appendix B: Calculations for Sizing Heat Exchanger ........................................... 21 Appendix C: Site Survey – Thermal Images.......................................................... 24 Appendix D: Cost Estimate for Adding Insulation................................................ 37 5I. Introduction Smith College employs a steam heating system in order to generate and provide heat to buildings on campus. However, a question heretofore unasked is whether the entire stream of steam is actually delivered to the specified destinations ‐ how much heat is lost to the atmosphere as the steam is transferred from the Physical Plant to an academic building? The more heat that is dissipated during this process, the more steam the cogeneration plant would need to produce in order to meet the demands of the campus. Therefore, Todd Holland, the energy manager for the Five Colleges, Inc. was interested to see how heat loss can be diminished by adding insulation. In addition, since this thermal energy can be put into good use, Robert Nicholson from the Lyman Plant House & Conservatory wanted to determine whether heat exchangers can be installed to use the heat from the steam tunnel to warm the greenhouse. Thus, the main purpose of this project was to (1) estimate the amount of heat that is lost when steam is transported from the Smith College Physical Plant to other buildings on campus, (2) determine the percentage decrease in heat loss when insulation is added, and (3) discern whether a heat exchanger unit is feasible. The Steam Tunnel The Smith College Steam Tunnel was built in 1946. This tunnel houses the steam pipes needed to transport the steam generated in the Physical Plant to heat student houses and academic buildings on campus. The steam tunnel has two valve chambers: Valve Chamber A extends from the Physical Plant to the Lyman Plant House & Conservatory; Valve Chamber B extends to John M. Greene Hall (Appendix A). This steam tunnel is located approxi mately 4ft below grade and has a total length of approximately 3500ft. 6Insulation & Heat Loss The pipes in the steam tunnel are insulated with 2” of asbestos covered by a canvas jacket. However, a large amount of heat still escapes from these pipes and simply dissipates upward out of the tunnel through the ground. For instance, oftentimes during the winter we see patches of grass amidst snow on Tyler Lawn and College Lane (Fig. 1). These areas with melted snow actually correspond to the path of the steam tunnel illustrated in Appendix A. Thus, the heat is escaping from the steam tunnels and warming the ground, which melts the snow. Figure 1: Melted snow on Tyler Lawn As suggested by Todd Holland, this project will investigate the impact of adding an additional layer of asbestos to the steam pipes. By decreasing the amount of heat dissipation, the cogeneration plant would not need to produce as much steam. The Lyman Plant House & Conservatory The steam tunnel runs under the Lyman


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