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Indexed by:
Article
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First Author:
Fei Lei
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Co-author:
Pingfang Hu,Na Zhu,Tianhua Wu
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Journal:
Applied Energy
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Included Journals:
SCI
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Affiliation of Author(s):
Huazhong University of Science and Technology
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Place of Publication:
United Kingdom
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Discipline:
Engineering
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First-Level Discipline:
Civil Engineering
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Document Type:
J
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Volume:
151
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Page Number:
132-142
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ISSN No.:
0306-2619
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Key Words:
Ground source heat pump;Borehole heat exchanger;Frequency response;Harmonic method;Frequency decomposition
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DOI number:
10.1016/j.apenergy.2015.04.035
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Date of Publication:
2015-07-08
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Impact Factor:
11.446
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Abstract:
Most existing borehole heat exchanger models are based on constant heat flux solutions. This paper first proposes a periodic heat flux composite model for a borehole heat exchanger to reproduce the periodic nature of real loads. An explicit analytical solution of a periodic cylinder-source in composite media is derived using a harmonic method. The periodic thermal response factor is defined to characterize the thermal behaviour of a borehole subjected to a periodic heat flux. The periodic thermal responses factors for high- and low-frequency periodic heat flux are dominantly determined by the thermal properties of the content inside the borehole and the ground outside the borehole, respectively. A frequency decomposition hybrid algorithm is specially designed according to the frequency response characteristic of borehole. The proposed periodic heat flux model is verified through an inter-model comparison with existing constant heat flux models and the comparison indicates an equivalent relationship between the two types of models. An annual simulation is performed using the hybrid algorithm and the accuracy of the algorithm is verified. The paper also presents a new method to analyse the data of an oscillatory thermal response test by using the periodic composite model. The effective heat capacities of the ground and grout are estimated. The simulation results of the periodic composite model are in good agreement with the experimental data. (C) 2015 Elsevier Ltd. All rights reserved.
