Salsuwanda Bin Selamat (Malaysia)

No.1
別紙第１号様式
portion. In contrast, the effective heat exchange rate is
14% longer when the return pipe is placed at the
博士論文の要旨
bottom compared to its horizontal orientation.
専攻名 Department of Science and Advanced
It is a common understanding that better thermal
Technology （システム創成科学）
performance comes with greater GHE length. This
氏
would allow more heat to be rejected to or extracted
名（本籍）
Salsuwanda Bin Selamat (Malaysia)
印
from more ground volume. Thus, thermal performance
博士論文題名
at optimum range is extended. GHE in slinky
Numerical modelling for horizontal ground
configuration can meet this objective while keeping
heat exchangers optimization
the trench length to be minimal. Within optimum
（水平型地中熱交換器の最適化を目的とした数
thermal performance range, all cases studied show
値モデルに関する研究）
comparable heat exchange rate. Nonetheless, for how
long they can operate effectively or simply effective
要旨（２，０００字程度にまとめること。
）
period differs from one another.
The effective period is a crucial parameter
In this work, horizontal ground heat exchangers
especially in shallow GHE installations where
(GHE) models for ground source heat pump (GSHP)
near-surface
systems in several configurations and pipe materials
temperature variation exist. GHE operation strategies
were simulated for thermal performance investigation.
are beneficial when dealing with thermal saturation in
The investigation can be divided into two stages: (1)
the ground. The ground should be allowed to
preliminary modelling involving a slice of ground
recuperate its thermal balance or some of it before the
profile cross-section containing only a unit of GHE
next cycle. Hence, it is sensible to operate GHE in
and (2) real-scale modelling of moderate-size
cycles
installations suited for residential or small commercial
domestic hot water supply. Alternating operation
buildings installation.
between
Based on the preliminary analysis, it was observed
that the effect of different GHE orientations is
or
interaction
alternate
(among)
and
higher
cooling-heating
multiple
trenches
ground
modes
that
for
are
well-spaced could be another option where the
resources permit.
negligible on thermal performance. The thermal
The proposed optimizations using different GHE
performance for vertical orientation provides a slight
configurations, orientations and pipe materials or in
improvement of 0.8% in mean heat exchange rate
combination could be used a guide in designing such
compared to horizontal orientation. However, the
installations. However, it is worth noting that any heat
preliminary analysis does not account for heat transfer
transfer enhancement would also cause thermal
contribution from the return pipe. The real-scale
interference especially in slinky configuration during
analysis reveals that the positioning or the return pipe
initial operation. In the end, factors such as heat pump
has significant effect on thermal
performance
loading, time of use and available resources should be
especially in vertical orientation. Adverse effect is
weigh in for a fine balance between systems efficiency
reported when the return pipe is positioned at the top
and cost-effectiveness.
No.2
別紙第１号様式
博士論文の要旨
専攻名 Department of Science and Advanced
Technology
氏
名 Salsuwanda Bin Selamat
Based on the preliminary analysis for 24 h
operation under several operation modes, it was found
that horizontal ground heat exchangers (GHE)
orientation is not so important. While the mean heat
exchange rate of copper loop increases 48% compared
to HDPE loop, the analysis supports the common
claim that heat exchange rate is predominantly limited
by the thermal conductivity of the ground. With the
same amount of circulation work, the mean heat
exchange rate increases by 83–162% when operated in
parallel loops operations. The performance in these
operations can be further optimized to 10–14%
increase when spacing between adjacent loops was
provided.
Comparative analysis was extended on real-scale
GHE models. All cases tested are able to yield
comparable heat exchange rate for an equal trench
length. However, the effective period differs one from
the other. Additional initial and overhead costs are
worthy as slinky GHE prolongs heat transfer process
when compared against straight configuration. An
improvement of 16% is reported when copper pipe is
used instead of the conventional HDPE pipes.
Effective period can be extended by 14% when GHEs
are installed in vertical orientation.
Keywords:
Ground source heat pump; ground heat exchangers;
thermal
performance;
simulation.
numerical
model;
CFD

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