Improving the thermal performance of coaxial borehole heat exchangers

Zanchini, Enzo; Lazzari, Stefano; Priarone, Antonella

doi:10.1016/j.energy.2009.10.038

Cited by 93 publications

(29 citation statements)

References 14 publications

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“…Insulating the inner pipe with materials of thermal conductivity lower than that of HDPE had a negligible effect on the borehole thermal resistance reported in this study. Thermal short-circuiting between the inner and outer flow channel was not a major concern for the studied GHEs with a large diameter, which can be different for GHEs of small diameter (Zanchini et al 2010). The volume of water in the proposed coaxial GHEs was up to 28 times greater than the volume for U-pipe GHEs, which is a second factor explaining the borehole length reduction.…”

Section: Discussionmentioning

confidence: 85%

“…Further work has recently been conducted on coaxial GHEs, where the exchanger consists of two pipes imbricated into each other. The impact of the flow rate and the pipe diameter and thermal conductivity on the heat transfer rate was investigated with numerical simulations (Zanchini et al 2010). Detailed experimental work was performed in the field to evaluate the borehole thermal resistance of different coaxial GHE configurations, where the external flow channel was made of several small pipes (Acuña et al 2011) or a flexible liner molding the borehole wall and avoiding the use of backfill material ).…”

Section: Introductionmentioning

confidence: 99%

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Designing coaxial ground heat exchangers with a thermally enhanced outer pipe

Raymond

Mercier²,

Nguyen³

2015

Geotherm Energy

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Background: Ground heat exchangers installed in boreholes are an expensive component of a ground-coupled heat pump system, where minimizing the borehole length with appropriate materials and configuration can reduce the overall cost of the system. Methods: Design calculations performed analytically indicate that the coaxial pipe configuration can be more advantageous than the single U-pipe configuration to reduce the total borehole length of a system. Results: A decrease of the borehole thermal resistance and an increase of the thermal mass of water contained in the coaxial exchanger helped to reduce borehole length by up to 23% for a synthetic building load profile dominated by cooling. The decrease of the borehole thermal resistance was achieved with an outer pipe made of thermally enhanced high-density polyethylene, where the thermal conductivity is 0.7 W m -1 K -1 .

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Section: Discussionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Designing coaxial ground heat exchangers with a thermally enhanced outer pipe

Raymond

Mercier²,

Nguyen³

2015

Geotherm Energy

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“…Previous studies on vertical closed systems focused mainly on (a) the comparison between these systems and other heat pump technologies such as air source heat pumps (e.g., Lohani and Schmit 2010;Urchueguía et al 2008;Petit and Meyer 1998;Said et al 2010;Liu and Hong 2010); (b) the energy, environmental, and techno-economic aspects of the conventional heating and cooling systems' substitution (e.g., Huchtemann and Müller 2012;Pardo and Thiel 2012;Boait et al 2011;Shonder and Hughes 2006;Rodríguez et al 2012); (c) the strategic design, controlling procedure, and the benefits of combined (e.g., Chen and Yang 2012;Xi et al 2011;Wang et al 2010;Pärisch et al 2014;Rad et al 2013) or hybrid systems (e.g., Pardo et al 2010;Man et al 2010;Yi et al 2008;Yu et al 2014;Alavy et al 2013), systems which combine GCHP and other RES (e.g., solar panels, PV panels) or conventional (e.g., oil-fired boiler) technology; and (d) the overall design procedure of vertical GCHP systems in order to improve the efficiency and minimize the installation and operation costs taking into account the GHEx configuration, the geophysical properties of the materials and soil, as well as the climate conditions of the installing area (e.g., Robert and Gosselin 2014;Alalaimi et al 2013;Chung and Choi 2012;Zanchini et al 2010;Sanaye and Niroomand 2009;Luo et al 2013). Urchueguía et al (2008), for example, compared a vertical GCHP system and an air to water heat pump system for heating and cooling in typical conditions of the European Mediterranean coast.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of ground source heat pump systems for residential buildings in warm Mediterranean regions: the example of Cyprus

et al. 2016

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This paper presents a feasibility analysis for the installation of ground source heat pump systems in Cyprus. Two reference buildings, a single-and a multifamily one, are designed and analyzed using the EnergyPlus software, in order to calculate their energy needs for heating and cooling for the climate conditions of Cyprus, one of the warmest areas in Southern Europe. These energy needs are assumed to be covered by the conventional heating and cooling systems that are most widely used in Cyprus or alternatively by a ground source heat pump system, which consists of a vertical ground heat exchanger and water-to-water heat pumps and is analyzed using an in-house developed and validated code. Primary energy consumption and the resulting CO 2 emissions for both the conventional and the alternative systems are calculated and compared. Results show that the installation of the ground source heat pump system achieves in most cases substantial reductions in primary energy use for both types of buildings. As regards carbon emissions, the findings are less clear:Emissions of the geothermal system are higher than those of the conventional system for the single-family building but considerably lower for the multi-family one. From an economic perspective, the geothermal system compares favorably with the conventional systems in many cases, particularly for the multi-family building.

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“…Otras investigaciones en transferencia de calor simuladas con COMSOL Multiphysics que han llegado a importantes resultados en la mejora de disipadores, son las del estudio de disipadores de pozo (Zanchini et al, 2009) y el modelaje de intercambiadores de tubos con aletas (Comini et al, 2008).…”

Section: Introductionunclassified

Modelación y simulación de disipadores de calor para procesadores de computadora en COMSOL Multiphysics

Garro-Acón¹,

Díaz-Espinoza²,

Jiang³

et al. 2012

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En este estudio se analizó la transferencia de calor en tres disipadores de calor utilizados para enfriar los procesadores de computadoras de escritorio. El objetivo de estos disipadores es evitar el sobrecalentamiento de la unidad de procesamiento y la consecuente reducción de la vida útil del computador. Los disipadores de calor se modelaron usando COMSOL Multiphysics con las dimensiones reales de los dispositivos y la generación de calor se modeló con una fuente puntual. Luego se modificaron los diseños de los disipadores para lograr una temperatura más baja en la zona más caliente del procesador. El resultado fue una reducción en la temperatura en el rango de 5-78 grados Kelvin, al rediseñarse el disipador de calor con variaciones feasibles como la reducción del grosor de las placas de intercambio de calor y el aumento de su número. Esto demuestra la posibilidad de desarrollar diseños optimizados para disipadores de calor que no requieran más materiales sino una mejor ingeniería. El trabajo se inició como parte del curso CM-4101 Modelización y Simulación.

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Improving the thermal performance of coaxial borehole heat exchangers

Cited by 93 publications

References 14 publications

Designing coaxial ground heat exchangers with a thermally enhanced outer pipe

Designing coaxial ground heat exchangers with a thermally enhanced outer pipe

Evaluation of ground source heat pump systems for residential buildings in warm Mediterranean regions: the example of Cyprus

Modelación y simulación de disipadores de calor para procesadores de computadora en COMSOL Multiphysics

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