博士 / 國立臺灣大學 / 海洋研究所 / 101 / Heat flow at various regions of the Earth’s surface is affected by primordial heat, interior heat sources and heat transfer between different regions. The geothermal heat flow information can be used to understand the Earth’s interior heat source and the lithospheric structures. The thermal structure can also play an important clue for understanding geophysical, geochemical, and geological processes. For that, this thesis is mainly aimed to develop a reliable tool for marine heat flow measurement. The development, construction and data reduction of different types of the marine heat flow measurements will also be compared. Because of high loss and damage rate and the high cost of the marine instruments, the capability of building in-house instruments can significantly reduce the cost of scientific experiments.
In this thesis, three major invented parts of the marine geothermal instrument are presented: (1) the Lister-type heat probe, (2) the compact high-resolution temperature logger and (3) the needle probe. The development of the Lister-type heat probe includes the updating of the design of circuit boards, the improvement in performance, and the additionally new functional features. It makes the new design more reliable and efficient. Compact high- resolution temperature logger is used to attach to a piston or gravity corer in order to have a deeper penetration ability of the corer and to measure the temperature gradient beneath the seafloor. Finally, the needle probe is used to measure the thermal conductivity of a core sample. The completed design and production of the instruments was made, and utilized in many field operations at sea.
A conductive heat flow is the product of a temperature gradient and a thermal conductivity. In reality, the measurement of a conductive heat flow can only be made in few meters below the seafloor; whereas, a thermal gradient of the crust is only about 30 mK per meter. Thus, the heat flow measurement needs a high temperature resolution of the instrument. However, the existing marine heat probes had only about 1 mK of temperature resolution. In this study, taking into account the features of the three developed instruments and optimizing measurement schemes, we will develop the state-of-the-art temperature measurement instruments. Particularly for the long temperature probe of the Lister-type heat probe, using ratiometric measurement and Common-Ground, Multiplexed-Three-Wires measuring scheme (CGMTW), the HR-3 can have temperature resolution of 0.1 mK, which is the highest resolution amongst the Lister-type heat probes so far.
Taking into account different construction and operation of instrument, we develop three designs of heat flow instruments:
HR-3 Lister-type heat probe, emphasizing on the high temperature resolution measuring scheme of the multi-channel long temperature probe;
CHTL temperature logger, emphasizing on durability and convenience mechanic structure;
NP-1 needle probe, emphasizing on mobility, portability and measuring speed.
When the heat probe penetrates into the sediments, the friction heat will raise the temperature of the probe and its surrounding sediments and generate transient temperature interfere. It takes a considerable span of time for waiting the dissipation of friction heat and the return to the background temperature. In fact, this may not be realistic, especially when one considers the research ship’s operation time and cost. A more practical way is to use the high-resolution frictional heat data caused by the frictional penetration into the sediments, and to numerically simulate the friction heat dissipation by using cylindrical temperature decay function to predict the friction-raised temperatures to infinite time. Accordingly, both the background temperatures and temperature gradients of the sediments can be obtained. Such kind of data reduction can be used for the Lister-type heat probe and the autonomous outrigger probe. However, the small temperature loggers that are attached to an autonomous outrigger probe may be not suitable for such a reduction because the temperature probe is far from an ideally cylindrical body. In that case, the reduction directly from the original thermal gradient data and an empirical correction formula could be adopted to obtain better background thermal gradients.
| Identifer | oai:union.ndltd.org:TW/101NTU05279005 |
| Date | January 2013 |
| Creators | Hung-I Chang, 張宏毅 |
| Contributors | 徐春田 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 151 |
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