Improvements in the Water Retention Characteristics and Thermophysical Parameters of Backfill Material in Ground Source Heat Pumps by a Molecular Sieve

Tingting Luo, Peng Pei, Yixia Chen, Dingyi Hao and Chen Wang
Additional contact information
Tingting Luo: Mining College, Guizhou University, Guiyang 550025, China
Peng Pei: Mining College, Guizhou University, Guiyang 550025, China
Yixia Chen: Mining College, Guizhou University, Guiyang 550025, China
Dingyi Hao: Key Laboratory of Deep Coal Resource Mining, Ministry of Education, China University of Mining and Technology, Xuzhou 221116, China
Chen Wang: Mining College, Guizhou University, Guiyang 550025, China

Energies, 2022, vol. 15, issue 5, 1-15

Abstract: The thermophysical properties of backfill material (BM) in a heat exchange borehole significantly influence the heat exchange effect of ground source heat pumps (GSHPs). Several treatments such as compaction and adding bentonite, cement, and fine sands are often used to improve the thermophysical properties. In this study, a 3A molecular sieve (3A-MS), a type of porous material, was added to the BM to enhance its water maintaining capacity. Three types of backfill materials with different additive contents, named as BM-0, BM-1, and BM-2, were examined. The variation of the BM properties such as the soil–water characteristic curve (SWCC), thermal conductivity, specific heat capacity, and thermal diffusivity with the groundwater content were investigated through a series of experiments and simulations. A scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and the BET method for specific surface area pore size analysis were used to characterize the material. The results indicated that the specific heat capacity improved with the water content whereas the thermal conductivity and thermal diffusivity decreased with the water content. The variation of the buried pipe outlet temperature with the change of the thermal physical parameters of the BM were researched by a numerical simulation and theoretical calculations; the results showed that BM-2 could raise the heat transfer rate per meter by 45.9% in summer and 118.4% in winter compared with the backfill materials without groundwater (NW). The research results provide theoretical support for the improvement of BM for ground source heat pump projects where abundant groundwater is available.

Keywords: heat exchange borehole; 3A molecular sieve; backfill material; thermophysical properties; soil–water characteristic curve (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

Downloads: (external link)
https://www.mdpi.com/1996-1073/15/5/1801/pdf (application/pdf)
https://www.mdpi.com/1996-1073/15/5/1801/ (text/html)

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:gam:jeners:v:15:y:2022:i:5:p:1801-:d:761145

Access Statistics for this article

Energies is currently edited by Ms. Agatha Cao

More articles in Energies from MDPI
Bibliographic data for series maintained by MDPI Indexing Manager ().