10th Asian Regional Conference of IAEG (2015)

Heat Transfer Characteristic of Saturated Sand in Steady Flow around a Cooling Pipe
Rangga SUDISMAN(1), Masahiko OSADA(1) , Tadashi YAMABE(1), and Daijiro TOBITA(1)(1) Graduate School of Science and Engineering, Saitama University, Japan
E-mail: s13de057@mail.saitama-u.ac.jp
Abstract
Study presented throughout this paper introduces a laboratory experimental method
to observe heat transfer characteristics on the geological material that experiences a coolingprocess. The experiment combines flow test, cooling process, and observation oftemperature change by using infra-red thermograph on saturated Toyoura Sand as theobserved heat-transfer medium. Saturated sand is stored in a rectangular container that isconnected with water flow and coolant pipe systems while infra-red thermograph camera
observing the temperature change on the saturated sand mass. +5.0˚C brine solution is usedas the coolant fluid in this experiment so that cooling process could not lead into frozen
condition. Thermograph observation results show the obvious temperature change duringcooling process. The results also indicate the effect of water flow rate to the heat transfer
characteristic. Moreover, flow rate and initial temperature variations are resulted distinctive
heat transfer distribution in the sand mass.
Keywords: heat transfer, porous medium, infra-red thermograph, fluid flow
1.

Introduction

medium (Zhao et al., 2008) around GHE. However,both of those studies were conducted with anassumption of no initial flow occur in the observed ormodeled porous material.
Considering the initial flow in heat transfer
process is very important since groundwater flow
exists in the real field, and even it is very significant
in some cases such as Fukushima frozen wall project.
Furthermore, visualization of heat distribution that is
affected by the initial flow is also important to givecomprehensive understanding on coupled THM
phenomena. As the first step of continuous study, on
this paper, the authors focus on the visual observationof heat distribution of saturated sand in steady flow
around a cooling pipe. The experiment was conducted
on unfrozen condition so that the main coupledphysical phenomena are thermo-hydrological while
the mechanical process is not considered.

Natural and artificial cooling of geologicalmaterial involves thermal, hydrological, andmechanical (THM) processes that may cause
considerable change on the geological material itself.
Understanding and predicting the behavior ofgeological material and its groundwater flow undercooling condition is necessary to ensure success andeffectiveness of the geological engineering projectsuch as frozen ground wall isolation project,underground LNG storage, tunneling project,ground-coupled heat pump (GCHP) with ground heatexchanger (GHE) technology, etc.
A number of researchers have conducted thesubstantial study on coupled THM process ofgeological material by various methods. Many ofthem focused on the effect of freezing and thawing to
the deformation characteristic and deterioration ofgeological material (Altindag et al., 2004; Chen et al.,
2004; Hori & Morihiro, 1998; Yamabe & Neupane,2001). Besides, numerical analyses have beendeveloped to simulate the coupled THM phenomena(Konrad & Shen, 1996; Neupane & Yamabe, 2001).
Another important factor in coupled THM study isthe heat transfer itself. Numerical evaluation andlaboratory experiment on heat transfer have been
conducted to evaluate the variation of soil
temperature (Yang et al., 2015) or artificial porous

2.

Experimental Setup

Photo. 1 shows the whole experimental system inthe present work. It mainly consists of a porous
medium specimen that is connected with cooling andwater flow systems, circulation systems, alsomeasurement and data acquisition systems. Authors
prepare Toyoura sand with 39.5±0.7% average
porosity as the porous medium, which is contained
inside a rectangular transparent acrylic box (Photo. 2)

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10th Asian Regional Conference of IAEG (2015)

used for flow measurement discharged from thespecimen box while infra-red thermograph camera(Testo 876 Thermal Imager) is used for specimen’stemperature measurement. It can capture temperature
profile of a surface that is focused to sand-filled area
(8.50 x 10.80 cm2).
In this experiment, room temperature is notcontrolled. Therefore, initial temperature of eachexperiment might vary to depend on the airtemperature and initial temperature of flowing water.
There are three phases of experiments; (i)stabilization phase, (ii) cooling phase, and (iii)stop-cooling phase. For the stabilization phase, first,
prepared specimen is filled with water and left for
about 24 hours to reach saturated condition. In thenext day, we install the water flow and coolingsystem to the specimen. Water flows from upstream
storage (A, in Photo. 1) to the sand specimen (B),then it is discharged into outlet storage above theelectric balance (C). To produce significant
difference between initial temperature and coolingsystem (+5.0˚C), authors increase the initial
temperature of water before it is flowed into sandspecimen by using water temperature control
apparatus (D). At this phase, cooling system is not
circulated yet until the water discharge rate is stable,
and the initial temperature condition inside the sandspecimen is uniformly distributed. Water continues toflow along the entire experiment phases.
The cooling phase starts when the expected
approximate steady-state condition is achieved.
+5.0˚C brine fluid with 4.74x10-7 m3/s flow rate is
pumped (E) from cooling machine into copper pipe(F) and circulated back so that cooling temperature
can be maintained. This phase lasts for 60 minutes.
Infra-red thermograph (G) captures the surface
temperature profile of the sand specimen in every
1-minute period. The stop-cooling phase starts after
60 minutes of cooling. Brine fluid circulation is
stopped while water continues to flow and Infra-red
thermograph continues to capture the temperature
profile for the next 20 minutes.

Photo. 1 Experimental system
Inner dimension of the box are 10.50 cm height,
10.80 cm length, and 1.46 cm width. 8.50 cm of theheight is filled with sand and the rest 2.00 cm is filledby oil clay as the impermeable layer. The thickness of
the acrylic is 1.0 mm with the outer surface directly
exposed to the ambient temperature. The box isequipped with an inlet for a water flow system withstatic-head pressure, and an outlet located at 8.50 cm
of box’s height. Head pressure is controlled byadjusting the elevation of upstream water storage.
The cooling system consists of RN-N30L coolingmachine, circulation pump, connecting pipe and acopper circulation pipe. Cooling machine controls thetemperature of Z1 type Nybrine fluid that circulates
through a copper pipe, which is inserted into the sandspecimen. The copper pipe consists of inner and outerpipe so that brine fluid can be circulated inside theouter pipe. Diameter of inner pipe and outer pipe is
1.0 cm and 0.3 cm, respectively. Three different
depths of copper pipe insertion to the sand specimen
are prepared in this experiment; (D1) maximum depth
down to the base of the box, (D2) 2.0 cm above thebase of the box, and (D3) 4.0 cm above the base of
the box.
For the measurement system, electric balance is

Photo. 2 Sand box specimens2

10th Asian Regional Conference of IAEG (2015)

Fig. 1 Heat distribution profile of D1V1, D1V2, and D1V3 (0-10 minutes)
spreads from the pipe (median of the box) to its
surrounding. Cold-affected area inside the specimen
is increasing over the time. The area that has arelative temperature of 75% is shown by yellow color.
Within 10 minutes, by focusing to the left side of thecooling pipe (upstream), it can be observed on Figure
2 that D1V3 specimen has less yellow color than
D1V1 and D1V2. It means that D1V3 specimen has
smaller cold affected area than D1V1 and D1V2. An
opposite result can be observed on the right side of
the cooling pipe (downstream), D1V3 shows wider
cold-affected area while D1V1 shows less. From
those series of figures, we can see that flow rate holds
an important role in heat distribution characteristic.
Water flow hampers heat distribution towards
upstream direction while it accelerates heat
distribution towards downstream.

Table 1 Initial condition of each experiment
No.
1

2a

2b

3

Exp.

Av. Initial T of sand

Av. Flow

Title

specimen (˚C)

Rate (m3/s)

D1V1

16.3

2.929E-08

D1V2

15.8

6.874E-08

D1V3

16.1

1.102E-07

Average

16.1

-

D1T1

14.7

7.381E-08

D1T2

15.9

7.339E-08

Average-

7.360E-08

D1T3

16.3

2.929E-08

D1T4

19.2

2.698E-08

Average-2.495E-08

D1

16.3

2.929E-08

D2

15.0

2.921E-08

D3

16.9

2.688E-08

Average

16.1-

In this study, heat transfer distribution isinvestigated under three experimental variations:(1) Experiments of D1 specimen with similar initial
temperature and different water flow rate(2) Experiments of D1 specimen with different
initial temperature and similar water flow rate(3) Experiments of D1, D2, & D3 specimens withsimilar initial temperature and water flow rate
Initial temperature and water flow rate of eachexperiment are listed on Table 1.
3.

Results and Discussion

3.1 Effect of flow rate variation
Figure 1 shows the first 10-minute results oftemperature profile of D1V1, D1V2, and D1V3
relative to its initial temperature. Cold temperature

Fig. 2 Comparison of D1V1, D1V2, andD1V3 (at 10 minutes)

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10th Asian Regional Conference of IAEG (2015)

Fig. 3 Heat distribution profile of D1V1, D1V2, and D1V3 (20-70 minutes)
Figure 3 shows the later stage of heat distribution
profile up to 70 minutes in 10 minutes interval. By
focusing on the pipe location, it can be observed that
D1V1 shows more intense dark-blue color than theother two specimens. It indicates that the mostsignificant heat reduction occurs in the sample withlow flow rate. The comparison can be seen clearly in
Figure 4 where D1V1 is plotted below D1V2 andD1V3. Relative minimum temperature is a percentageof the lowest measured temperature through thespecimen’s surface proportional to its initial
temperature. We can observe that the temperaturereaches quasi-steady-state after 10-15 minutes ofcooling. Quasi-steady-state conditions of D1V1,
D1V2, and D1V3 are reached at 41%, 47%, and 52%
of initial temperature, respectively. Specimen withhigher flow rate reaches the minimum temperatureearlier that the lower flow rate specimen.
Besides, D1V2 specimen shows different
characteristics during the stop-cooling phase. Increasein temperature that occurs in D1V2 after the coolingwas stopped is slower than the others, which isindicated by lighter color (Fig. 3 D1V2-70) and lower
line (Fig.4). This distinction is most likely caused by
the temperature changes of water inside upstream
storage, which is controlled manually against room
temperature and water replenishment. Therefore,change is likely to occur during the experiment.
From these experiments, we can say that heattransfer in saturated porous media is mainly governedby the heat convection process, which is significantly
affected by the movement of the fluid. Water flow
prevents cold temperature to be accumulated at static
point and accelerates heat convection to the wider
area.

Relative Minimum Temperature (%)

discharged water flow rate with the average value of
7.360x10-8 m3/s than D1T3 and D1T4 with averagevalue of 2.495x10-8 m3/s. Despite the graph shows
two groups of flow rate, the effect of initial
temperature on each experiment is clearly
distinguished. It can be observed that specimen withhigherinitialtemperature experiences more significant temperature
100

80

60

40
D1V1
D1V2

20

D1V3

0

20

40
t (minutes)

60

80Fig. 4 Relative minimum temperature by time of D1
in different flow rate
Relative Minimum Temperature (%)

100

3.2 Effect of initial temperature variation
Figure 5 shows the relative minimum temperature
over time of D1 specimen in different initial
temperature condition. D1T1 and D1T2 have higher

D1T1
D1T2
D1T3
D1T4

80

60

40

20

0

20

40
t (minutes)

60

80Fig. 5 Relative minimum temperature by time of D1
in different initial temperature4

10th Asian Regional Conference of IAEG (2015)

reduction. D1T4 that has the highest initial
temperature experienced the largest decline. Its
minimum temperature reached 29% of the initial.
Otherwise, the lowest temperature of D1T1 only
reached 49% of the initial. For other two specimensthat have more similar initial temperature condition,
their relative minimum temperatures are also close;
41% for D1T2 and 40% for D1T3.
In case of flow rate variation, Figure 5 also
supports the previous discussion of Figure 4, whichfound that specimen with higher flow rate reaches theminimum temperature earlier that the lower flow rate
specimen. By the combination of high flow rate andlow initial temperature, D1T1 and D1T2 reachquasi-steady-state in 10 to 15 minutes after coolingstarted. In contrast, D1T3 and D1T4 which havelower flow rate and higher initial temperature reachquasi-steady-state after 20 to 25 minutes of cooling.
Results of this experiment are in accordance withthe basic principle of heat transfer. Higher initial
temperature means significant thermodynamic
potential, which resulting more energy requirements
to reach equilibrium condition.

3.3 Effect of pipe’s depth variation
Figure 6 shows the first 10-minute results ofrelative heat distribution of D1, D2, and D3,
respectively. We can clearly distinguish thedifference of pipe’s depth at the beginning of thecooling process. Since cooling pipe of D1 specimen
is buried down to the base of the box, significant heattransfer mainly occurs along the horizontal axis. In
contrast, D2 and D3 specimens show more radial
movement of heat changes. In both D2 and D3,
significant temperature changes on the early stage(first 2 minutes) can only be seen in the area as longas the depth of pipe. Subsequently, temperaturechanges within the area below the pipe are more
obvious after 4 minutes of cooling and tend to spreadin all directions during cooling. Besides, we can also
observe the effect of water flow; right side of the pipe
shows lighter color than the left side. Basically,heat distributes in all directions, but 2.844x10-5 m3/s
average flow of water from the right to left has
produced the heat distribution tendency towards
downstream.

Fig. 6 Heat distribution profile of D1, D2, and D3 (0-10 minutes)

Fig. 7 Heat distribution profile of D1, D2, and D3 (20-70 minutes)

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10th Asian Regional Conference of IAEG (2015)

Figure 7 shows the later stage of heat distribution
profile up to 70 minutes in 10 minutes interval.
Change of temperature occurred in D2 is greater thanD1 and D3. A possible reason for this difference iscaused by the heterogeneity of room and flowing
water temperature. In addition to the initial
temperature difference of the specimens, room
temperature is also varied over the time. During theexperiment, room temperature of D2 specimen was
6˚C, while D1 and D3 were 10˚C and 8˚Crespectively. That low room temperature may affecttemperature of flowing water and accelerate thecooling process of D2 specimen. However, it is still
unclear and has to be proven by further investigation.
As previously discussed, direction of heat
convection depends on the fluid flow. Change oftemperature on vertical axis to the bottom part of D2
and D3 pipes occurs even though the main flow
direction is horizontal. It may be caused by thedifferences in water density. Water with lower
temperature but not less than 4˚C has higher density
so that it tends to move downward due to gravity.
Moreover, heat convection is not the only mechanism
governing the heat transfer in saturated porous media.
Heat conduction process may also occur due tocontact of each sand and water molecules.
4.

is necessary to be investigated. However, as the
beginning of continuous study, these results provide
clear evidence on the heat transfer behavior around acooling pipe. Therefore, further experiment isrequired to observe the heat transfer characteristic ofsaturated sand in steady flow at around a freezing
pipe.
Acknowledgement
This work was supported by JSPS KAKENHI
Grant Number 26249068. Authors are grateful to Dr.
Takato Takemura at Nihon University Japan forgiving permission to use the infra-red thermograph.
References
Altindag, R., Alyildiz, I. S., and Onargan, T. (2004):
Mechanical property degradation of ignimbrite
subjected to recurrent freeze-thaw cycles,
International Journal of Rock Mechanic and Mining
Sciences, Vol. 41, pp. 1023-1028
Chen, T. C., Yeung, M. R., and Mori, N. (2004):
Effect of water saturation on deterioration of weldedtuff due to freeze-thaw action, Cold Regions
Science and Technology, Vol. 38, pp. 127-136
Hori, M. and Morihiro, H. (1998): Micromechanicalanalysis on deterioration due to freezing andthawing in porous brittle materials, International
Journal of Engineering Science, Vol. 36, No. 4, pp.
511-522
Konrad, J. M., and Shen, M. (1996): 2-D frost action
modeling using the segregation potential of soils,
Cold Regions Science and Technology, Vol. 24, pp.
263-278
Neupane, K. and Yamabe, T. (2001): A fully coupled
thermo-hydro-mechanical nonlinear model forfrozen medium, Computers and Geotechnics, Vol.
28, pp. 613-637
Yamabe, T. and Neupane, K. (2001): Determinationof some thermo-mechanical properties of Shirahama
sandstone under subzero temperature condition,
International Journal of Rock Mechanic and Mining
Sciences, Vol. 38, pp. 1029-1034
Yang, W., Kong, L., and Chen, Y. (2015): Numericalevaluation on the effects of soil freezing onunderground temperature variations of soil aroundground heat exchangers, Applied ThermalEngineering, Vol. 75, pp. 259-269
Zhao, J., Wang, H., Li, X., and Dai, C. (2008):
Experimental investigation and theoretical model ofheat transfer of saturated soil around coaxial groundcoupled heat exchanger, Applied ThermalEngineering, Vol. 28, pp. 116-125

Conclusion

In this study, we introduced a laboratory
experimental method on the saturated sand in steadyflow at around a cooling pipe. This method iseffective to observe the heat transfer and able todistinguish the heat transfer characteristic based oneach determining factor; flow rate variation, average
initial temperature variation and pipe’s depth
variation. From the experimental results, thefollowing conclusions can be obtained: Heat transfer through the sand mass is mainly
governed by thermal convection of flowing water.
 Both maximum temperature reduction andrequired cooling duration before quasisteady-state condition are decreasing with theincreasing flow rate.
 Initial temperature affects the required cooling
duration to reach quasi-steady-state condition;higher initial temperature requires longer cooling
duration.
 Depth of pipe plays the important role in the heat
distribution and effectiveness of cooling process.
The results obtained in this experiment are notsufficient to explain a frozen ground case since it may
have different behavior, especially on how the ice
formation affects water flow. Besides, the effect offlow velocity through the formation of a frozen body6