Evaluation of thermal efficiency in different types of horizontal ground heat exchangers

Yoon, Seok; Lee, Seung-Rae; Go, Gyu-Hyun

doi:10.1016/j.enbuild.2015.07.054

Cited by 94 publications

(30 citation statements)

References 29 publications

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“…Thus, the higher the difference of temperature between the hot and the cold tube of the heat exchanger, the greater the amount of heat collected by the circulating fluid. This fact constitutes an indicator of the heat exchanger and grouting material quality [21,22].…”

Section: Methodsmentioning

confidence: 99%

Efficiency Analysis of the Main Components of a Vertical Closed-Loop System in a Borehole Heat Exchanger

et al. 2017

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Abstract:In vertical closed-loop systems, it is common to use single or double U-tube heat exchangers separated by longitudinal spacers. In addition, the helical-shaped pipe is another configuration that requires lower drilling lengths but it is less used. The aim of the present research is to study the influence of these components on the total efficiency of a borehole heat exchanger (BHE). Thus, the differences between using single/double U-tubes (with or without spacers) and helical pipes are analysed in terms of efficiency. Through different laboratory tests, a small vertical closed-loop system was simulated in order to analyse all these possible configurations. The grouting materials and the temperatures of the ground were modified at the same time in these tests. Regarding the heat exchange process between the ground and the heat carrier fluid, it must be highlighted that the best results were obtained for the helical-shaped pipe configuration. Some of the improvements offered by this heat exchanger typology with respect to the vertical configuration is that a lower drilling depth is required even it requires a larger diameter. This leads to significant economic savings in the performing drilling process. Finally, it is also worth noting the importance of using spacers in vertical U-tubes and that no improvements have been found regarding the use of single or double configuration of U-tubes. Thanks to the laboratory results derived from this study it is possible to establish the optimum behaviour pattern for the entire vertical closed-loop systems.

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Section: Methodsmentioning

confidence: 99%

Efficiency Analysis of the Main Components of a Vertical Closed-Loop System in a Borehole Heat Exchanger

et al. 2017

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“…Table 1 show the TRT equipment and specification of the TRT equipment that was used in the test [3]. Besides, in the experiment, a 5m x 1m x 1m steel box filled with dry Joomunjin standard sand ( Table 2) was also used to reflect the surrounding ground, while the TRT equipment was installed to supply the circulating water and constant power to the inside of the heat exchanger buried in the ground.…”

Section: Test Prodedurementioning

confidence: 99%

Thermal performance evaluation of horizontal spiral coil-type ground heat exchangers

Kim¹,

Lee²,

Lim³

et al. 2018

Proceedings of the IGSHPA Research Track 2018

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“…On the other hand, although horizontal heat exchangers are reported by many studies [9,[24][25][26][27][28][29], few of them are related to a coiled heat exchanger. Most of them are horizontal ground heat exchangers [25,26], tube heat exchangers [27,28], or flat-panel heat exchangers [9,29].…”

Section: Introductionmentioning

confidence: 99%

“…Most of them are horizontal ground heat exchangers [25,26], tube heat exchangers [27,28], or flat-panel heat exchangers [9,29]. Notably, Abdel-Wahed RM et al experimentally studied a horizontal flat plated cooling surface.…”

Section: Introductionmentioning

confidence: 99%

An experimental study on defrosting performance for an air source heat pump unit with a horizontally installed multi-circuit outdoor coil

et al. 2016

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Highlights• Negative effects due to gravity eliminated when outdoor coil horizontally installed.• Defrosting efficiency increased 9.8% after outdoor coil horizontally installed.• Defrosting efficiency decreased 6.6% when air fan reversed to blow the melted frost.• Total mass of the retained water collected decreased 222 g less after wind blowing.• Higher DEV respected better defrosting performance for multi-circuit outdoor coils. 2 AbstractWhen frost forms and accumulates over the outdoor coil's surface in an air source heat pump (ASHP) unit, system operating performance will be dramatically deteriorated.Reverse cycle defrosting is the most widely used standard defrosting method. A previous related study reported that downwards flowing of melted frost due to gravity over a vertical multi-circuit outdoor coil would decrease the reverse cycle defrosting performance. If the outdoor coil can be changed to horizontally installed, the flow path of melted frost over coil surface can be shortened, and the flow directions of refrigerant and melted frost changed from opposite to orthogonal. Consequently, a better defrosting performance is expected. In this paper, therefore, an experimental study on defrosting performance for an ASHP unit with a horizontally installed multi-circuit outdoor coil was conducted. Experimental results show that, when a vertical outdoor coil was changed to horizontally installed, the defrosting efficiency increased 9.8%, however, with the same defrosting duration at 186 s. Furthermore, when the outdoor air fan was reversed to blowing the melted frost during defrosting, the total mass of the retained water collected decreased 222 g. However, the defrosting efficiency was not increased, but decreased 6.6% because of the heat transfer enhanced between hot coil and cold ambient air.

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Evaluation of thermal efficiency in different types of horizontal ground heat exchangers

Cited by 94 publications

References 29 publications

Efficiency Analysis of the Main Components of a Vertical Closed-Loop System in a Borehole Heat Exchanger

Efficiency Analysis of the Main Components of a Vertical Closed-Loop System in a Borehole Heat Exchanger

Thermal performance evaluation of horizontal spiral coil-type ground heat exchangers

An experimental study on defrosting performance for an air source heat pump unit with a horizontally installed multi-circuit outdoor coil

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