Ground Source Heat Pump Modeling: Accounting of Ground Moisture Freezing-Melting in a Model of Heat Transfer outside Deep Borehole

Abstract:

This paper contains the results of research, carried out with financial support from the Ministry of Education and Science of the Russian Federation (contract ID RFMEFI57914X0026). For the ground source heat pump (GSHP) used as a heating system in regions with cold climate the thermal effects of ground moisture freezing-melting processes can make an essential long-term impact on GSHP performance. However, widely known models of heat transfer inside and outside GSHP borehole do not take into account such effects. In this paper we propose a method of engineering estimation of freezing-melting latent heat in the frame of modified cylindrical source model. The key feature of the method is the definition of effective thermal conductivity of ground to "convert" the latent heat of phase transition into equivalent heat flux from outer ground. The method is validated by laboratory measurements of ground thermal conductivity during the freezing-melting process.

• Periodical: Applied Mechanics and Materials (Volume 704)
• Pages: 102-112
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.704.102
• Online since: December 2014
• Authors: G.P. Vasilyev, N.V. Peskov, A.A. Burmistrov, N.A. Timofeev, P.E. Zakharov, I.A. Yurchenko
• Keywords: Ground Source Heat Pump (GSHP), Heat Pump Heating System, Phase Transitions in Ground Moisture

References

[1] Florides G., Kalogirou S. Ground heat exchangers - A review of systems, models and applications. Renewable Energy, 32 (2007) 2461–2478.

DOI: 10.1016/j.renene.2006.12.014

[2] Yang H., Cui P., Fang Z. Vertical-borehole ground-coupled heat pumps: A review of models and systems, Applied Energy, 87 (2010) 16-27.

DOI: 10.1016/j.apenergy.2009.04.038

[3] Lamarche L., Kajl S., Beauchamp B. A review of methods to evaluate borehole thermal resistances in geothermal heat-pump systems. Geothermics, 39 (2010) 187-200.

DOI: 10.1016/j.geothermics.2010.03.003

[4] Yuan Y., Cao X., Sun L., Lei B., Yu N. Ground source heat pump system: A review of simulation in China. Renewable and Sustainable Energy Reviews, 16 (2012) 6814–6822.

DOI: 10.1016/j.rser.2012.07.025

[5] Vasiliev G.P. Geothermal heat pump heating systems and its operating efficiency in climate conditions of Russia (Geotermalnyie teplonasosnyie sistemy i effektivnost' ih primeneniya v klimaticheskih usloviyah Rossii). AVOK - 2007. - n. 5. – pp.58-68.

[6] Guidice S.D., Comini G., Lewis R.W. Finite element simulation of freezing processes in soils. Int. J. Numer. Anal. Methods Geomech., 2 (1978) 223-235.

DOI: 10.1002/nag.1610020304

[7] Newman G.P., Wilson G.W. Heat and mass transfer in unsaturated soils during freezing. Can. Geotech. J., 34 (1997) 63-70.

DOI: 10.1139/t96-085

[8] Mikkola M., Hartikainen J. Mathematical model of soil freezing and its numerical implementation. Int. J. Numer. Methods Eng., 52 (2001) 543-557.

DOI: 10.1002/nme.300

[9] Yang W.B., Shi M.H., Chen Z.Q. Influence of soil freezing on the heat transfer characteristics of ground heat exchanger in ground coupled heat pump. Proceedings of the 7th International Symposium on Heat Transfer (ISHT7'08), Oct 26-29, 2008, USTB, Beijing, China.

DOI: 10.1615/ihtc15.hex.009412

[10] Parham Eslami-nejad P., Bernier M. Freezing of geothermal borehole surroundings: A numerical and experimental assessment with applications. Applied Energy 98 (2012) 333-345.

DOI: 10.1016/j.apenergy.2012.03.047

[11] Carslaw H.S., Jaeger J.C. Conduction of heat in solids. Oxford UK: Claremore Press; (1946).

[12] Ingersoll L.R., Zobel O.J., Ingersoll A.C. Heat conduction with engineering, geological, and other applications. New York: McGraw-Hill; (1954).

DOI: 10.1126/science.108.2816.694.a