Heat transfer by seepage in sand

influence of saturated hydraulic conductivity and porosity

Yaser Ghafoori (Author), Matej Maček (Author), Andrej Vidmar (Author), Jaromir Říha (Author), Andrej Kryžanowski (Author)

Abstract

Heat transfer within the soil is a complex process in the presence of seepage flow. In such conditions, the soil%s thermal behavior is influenced by the thermal and hydraulic properties of the medium as well as the initial conditions and boundary conditions to which the medium is subjected. This paper presents the experimental and numerical studies of heat transfer within the sand subjected to the seepage flow. It focuses on the influence of saturated hydraulic conductivity and the porosity of medium on the heat transfer process. The temperature distribution within the sand was monitored by the optical fiber Distributed Temperature Sensor (DTS). The experiment was performed on three types of silica-dominated sands with different saturated hydraulic conductivities and different Soil Water Characteristic Curve (SWCC). In addition to the experimental study, a coupled hydrothermal numerical model was designed in FEFLOW software and validated by comparing its results with the experimental measurements. To determine the influence of porosity and saturated hydraulic conductivity on heat transfer, we analyzed the numerical models for different values of porosity and saturated hydraulic conductivity. The numerical and experimental studies showed that the thermal velocity is higher in sand with higher saturated hydraulic conductivity and temperature declination occurs more quickly due to the heat convection process. Saturated sand with larger porosity has an overall higher heat capacity, wherefore the temperature declination started later in the measuring points but dropped down lower close to the temperature of the upstream water.

Keywords

heat transfer;porosity;saturated hydraulic conductivity;temperature, seepage;

Data

Language:	English
Year of publishing:	2021
Typology:	1.01 - Original Scientific Article
Organization:	UL FGG - Faculty of Civil and Geodetic Engineering
UDC:	532.5:676.017.6
COBISS:	70302979
ISSN:	0352-3551
Views:	1195
Downloads:	103
Average score:	0 (0 votes)
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Other data

Secondary language:	Slovenian
Secondary title:	Vpliv koeficienta prepustnostiin poroznosti zemljin na prenos toplote s precejanjem
Secondary abstract:	Prenos toplote s precejanjem v zemljinah predstavlja kompleksen problem. Na termično stanje zemljin vplivajo različni dejavniki, kot so toplotne in hidravlične lastnosti zemljin kot tudi njihova izpostavljenost obratovalnim pogojem ter omejitvam, ki jih narekujejo robni pogoji. V prispevku so predstavljeni rezultati raziskav prenosa toplote s precejanjem vode v zemljinah na podlagi primerjave laboratorijskih raziskav in računskega modela. Raziskavo smo usmerili v preučevanje vpliva koeficienta prepustnosti in poroznosti zemljine na proces prenosa toplote. Spremembe temperaturnega polja v eksperimentalni posodi smo merili z optičnimi kabli. Meritve temperaturnega polja v eksperimentalni posodi smo izvajali na treh različnih vzorcih kremenčevega peska s spreminjanjem stopnje poroznosti in koeficienta prepustnosti zemljine. Poleg eksperimentalnega dela smo zasnovali hidravlično-toplotni numerični model v programskem okolju FEFLOW za potrebe primerjalne analize merjenih in računskih vrednosti. Za ugotavljanje vpliva poroznosti in koeficienta prepustnosti v nasičeni zemljini na prenos toplote smo analizirali numerične modele za različne vrednosti teh dveh parametrov. Rezultati laboratorijskih preiskav in numeričnega modela so pokazali, da je hitrost prenosa toplote v materialih z večjim koeficientom prepustnosti večja, posledično je hitrejši upad temperature zaradi konvekcije. V bolj poroznih materialih je upad temperature zaznan kasneje, a je bolj izrazit in se približa vrednostim temperature okoliškega vodnega medija.
Secondary keywords:	prenos toplote;poroznost;koeficient prepustnosti;temperature;precejanje;
Type (COBISS):	Article
Pages:	str. 61-75
Volume:	34
Issue:	ǂ[št.] ǂ60
Chronology:	2021
DOI:	10.15292/acta.hydro.2021.05
ID:	13641408