RESEARCH AREAS
Ground-source heat pump systems
Design software
Dr. Spitler and his students developed the widely used design software GLHEPRO, currently in Version 5. Version 1 was released in 1994. GLHEPRO allows users to size ground heat exchangers used with ground-source heat pump systems. See Spitler (2000) or the current user’s manual.
More recently, Dr. Spitler and his students have worked on developing new methods that can automatically select borehole configurations given property constraints and determine the required depth. In some cases, this can lead to significant savings in drilling costs. See Spitler, et al. (2022) West and Spitler (2022), Cook and Spitler (2021), Spitler, et al. (2020a, 2020b).
Thermal response testing and in situ thermal conductivity measurement
Measurements of ground thermal conductivity and borehole thermal resistance provide key data used to design ground heat exchangers. Dr. Spitler and his students developed equipment and methodology for performing these tests (Austin, et al. 2000). Similar work was started in Sweden about the same time by Profs. Hellström and Nordell, and their then-student Dr. Gehlin. Drs. Spitler and Gehlin (2015) have reviewed the history and technology.
Ground heat exchanger performance
A quantitative understanding of the performance of the ground heat exchanger is necessary for both design calculations and simulations. Work in this area, much of which involved collaboration with my colleague from University of Lund in Sweden, Dr. Javed, includes experimental and computational investigation of borehole thermal resistance (Javed and Spitler 2016,2017), development of convection correlations for groundwater-filled boreholes (Spitler, et al. 2016), and measurements of pressure loss in borehole heat exchangers (Javed and Spitler 2022).
Field measurement of GSHP system performance
Dr. Spitler, his students and Dr. Gehlin from the Swedish Geoenergy Center have worked on monitoring the performance of ground-source heat pump systems in two buildings: the ASHRAE Headquarters building in Atlanta (Spitler, et al. 2017; Southard, et al. 2014a, 2014b) and Studenthuset, a building on the University of Stockholm campus (Spitler and Gehlin 2019, 2022). In addition, Drs. Gehlin and Spitler led an International Energy Agency annex under the Heat Pumping Technologies Technology Collaboration Program: Annex 52 - Long term performance measurement of GSHP Systems serving commercial, institutional and multi-family buildings.
Simulation of GSHP systems
Simulation of ground heat exchangers and ground-source heat pump systems is an important part of design, predicting system performance, and economic analysis. An early contribution by Dr. Spitler and his students was the short time step g-function (Yavuzturk and Spitler 2000, Xu and Spitler 2006). A ground heat exchanger model that considers fluid transit time effects (Mitchell and Spitler 2020) is particularly useful for whole building energy simulation programs that may utilize time steps on the order of minutes.
Other work includes models of standing column wells (Deng, et al. 2005), models for undisturbed ground temperatures (Xing and Spitler 2017a, 2017b, Xing, et al. 2017), a slinky heat exchanger model (Xiong et al. 2015)
References
Austin, W., C. Yavuzturk, J.D. Spitler. 2000. Development of An In-Situ System and Analysis Procedure for Measuring Ground Thermal Properties. ASHRAE Transactions. 106(1): 365-379. https://hdl.handle.net/11244/330741
Cook, J.C. and J.D. Spitler. 2021. Faster computation of g-functions used for modeling of ground heat exchangers with reduced memory consumption. Proceedings of Building Simulation 2021, Bruges, Belgium. September 1-3, 2021.
Deng, Z., S.J. Rees, J.D. Spitler. 2005. A Model for Annual Simulation of Standing Column Well Ground Heat Exchangers. HVAC&R Research. 11(4):637-655. https://doi.org/10.1080/10789669.2005.10391159
Javed. S. and J.D. Spitler. 2016. Calculation of borehole thermal resistance. In S.J. Rees Advances in ground-source heat pump systems. London: Woodhead Publishing. https://doi.org/10.1016/B978-0-08-100311-4.00003-0
Javed, S. and J.D. Spitler. 2017. Accuracy of Borehole Thermal Resistance Calculation Methods for Grouted Single U-tube Ground Heat Exchangers. Applied Energy.187:790-806. https://doi.org/10.1016/j.apenergy.2016.11.079
Javed, S. and J.D. Spitler. 2022. Vertical Ground Heat Exchanger Pressure Loss – Experimental Comparisons and Calculation Procedures. Geothermics 105: 102546. https://doi.org/10.1016/j.geothermics.2022.102546
Mitchell, M. S. and J. D. Spitler. 2020. An Enhanced Vertical Ground Heat Exchanger Model for Whole-Building Energy Simulation. Energies 13(16): 4058. https://doi.org/10.3390/en13164058
Southard, L.E., X. Liu, J.D. Spitler. 2014a. Performance of HVAC Systems at ASHRAE HQ – Part 2. ASHRAE Journal. December 2014, 56(12):12-23.
Southard, L.E., X. Liu, J.D. Spitler. 2014b. Performance of HVAC Systems at ASHRAE HQ – Part 1. ASHRAE Journal. September 2014, 56(9):14-24.
Spitler, J.D. 2000. GLHEPRO -- A Design Tool For Commercial Building Ground Loop Heat Exchangers. Proceedings of the Fourth International Heat Pumps in Cold Climates Conference, Aylmer, Québec. August 17-18, 2000.
Spitler, J.D., T.N. West and X. Liu. 2022. Ground Heat Exchanger Design Tool with RowWise Placement of Boreholes. IGSHPA Research Track. Las Vegas. Dec. 6-8
Spitler, J.D. and S.E.A. Gehlin. 2015. Thermal response testing for ground source heat pump systems - An historical review. Renewable and Sustainable Energy Reviews. 50:1125-1137. https://doi.org/10.1016/j.rser.2015.05.061
Spitler, J. D. and S. Gehlin. 2019. Measured Performance of a Mixed-Use Commercial-Building Ground Source Heat Pump System in Sweden. Energies 12(10): 2020. https://doi.org/10.3390/en12102020
Spitler, J.D. and S. Gehlin. 2022. 5-year performance of a Swedish mixed-use ground source heat pump system. REHVA Journal. 59(4):27-36.
Spitler, J.D., J.C. Cook and X. Liu. 2020a. Recent Experiences Calculating g-functions for Use in Simulation of Ground Heat Exchangers. GRC Transactions, 44:296-315.
Spitler, J.D., J.C. Cook and X. Liu. 2020b. A Preliminary Investigation on the Cost Reduction Potential of Optimizing Bore Fields for Commercial Ground Source Heat Pump Systems. Proceedings. 45th Workshop on Geothermal Reservoir Engineering. Stanford University, Stanford, California, February 10-12, 2020
Spitler, J.D., L.E. Southard, X. Liu. 2017. Ground-source and air-source heat pump system performance at the ASHRAE headquarters building. 12th IEA Heat Pump Conference. Rotterdam. May 15-18. ISBN 978-90-9030412-0.
West, T.N. and J.D. Spitler. 2022. Approximate g-functions for selection of borehole field configurations used with ground-source heat pump systems. European Geothermal Congress 2022. Berlin, Germany. 17-21 October 2022
Xu, X., J. D. Spitler. 2006. Modeling of Vertical Ground Loop Heat Exchangers with Variable Convective Resistance and Thermal Mass of the Fluid. Proceedings of the 10th International Conference on Thermal Energy Storage – Ecostock 2006, Pomona, NJ.
Xing, L. and J. D. Spitler. 2017a. Prediction of undisturbed ground temperature using analytical and numerical modeling. Part I: Model development and experimental validation. Science and Technology for the Built Environment 23(5): 787-808. https://doi.org/10.1080/23744731.2016.1258371
Xing, L. and J. D. Spitler. 2017b. Prediction of undisturbed ground temperature using analytical and numerical modeling. Part II: Methodology for developing a world-wide dataset. Science and Technology for the Built Environment 23(5): 809-825. https://doi.org/10.1080/23744731.2016.1262705
Xing, L., J. D. Spitler and A. Bandyopadhyay. 2017. Prediction of undisturbed ground temperature using analytical and numerical modeling. Part III: Experimental validation of a world-wide dataset. Science and Technology for the Built Environment 23(5): 826-842. https://doi.org/10.1080/23744731.2016.1253978
Xiong, Z., D.E. Fisher, J.D. Spitler. 2015. Development and Validation of a SlinkyTM Ground Heat Exchanger Model. Applied Energy. 141:57-69. https://doi.org/10.1016/j.apenergy.2014.11.058
Yavuzturk, C., J.D. Spitler. 1999. A Short Time Step Response Factor Model for Vertical Ground Loop Heat Exchangers. ASHRAE Transactions. 105(2):475-485.