Reporter :Ming-Che Chung Date : 2014/04/08 Experimental study of heat transfer for supercritical carbon dioxide with upward flow in vertical tube Reporter :Ming-Che Chung

Experimental apparatus and procedure Outline Background Purpose Experimental apparatus and procedure Results Conclusions This is my outline. It includes five sections. First one is the introduction, second is purpose, third Experimental architecture , and next one is Experimental process planning , last is Future Works

Background A novel renewable energy concept is geothermal power. Geothermal energy is the process of extracting the heat generation by earth and harnessing it to drive a power plant. 1

Traditional geothermal system Non-traditional geothermal system Geothermal type The geothermal system is divided into traditional geothermal system and non-traditional geothermal system. Table.1. Geothermal system of classification Geothermal system System name Temperature Depth Traditional geothermal system Low temperature system <100℃ 1,000~2,000m Middle temperature system 100~200℃ High temperature system 200~350℃ Non-traditional geothermal system Enhanced geothermal system 100~300℃ 3,000~5,000m 2

What is EGS ? Pump Seismometers Production well Injection well CO2 Production well Injection well What is EGS ? Artificial Fracture CO2 CO2 Fig.1. Schematic diagram of EGS 3

Why use CO2 as working fluid? Table.2. Comparison between Water and CO2 Brown propose that supercritical CO2 is use as working fluid in enhanced geothermal system. Fluid property Chemical Water: Powerful solvent for rock minerals: lots of potential for dissolution and precipitation. CO2: Not an ionic solvent; poor solvent for rock minerals. Fluid circulation in wellbores Small compressibility, moderate expansivity Large compressibility and expansivity. Ease of flow in reservoir Higher viscosity, higher density Lower viscosity, lower density Heat transmission Larger specific heat Smaller specific heat Why use CO2 as working fluid? Solve the deep geothermal limit of water shortage Special chemical properties Thermosiphon can enhance efficiency Sequestration for CO2 4

Purpose For the reason of all of previous studies are limited by the absence of an experimental system to investigate the performance of supercritical CO2 in the reservoir. This study determines the efficiency of heat extraction of supercritical CO2 in test section. 5

Experimental apparatus and procedure Pressure set up Test section heated The operating condition achieved Yes Yes Data collection Steady state CO2 injected 文獻蒐集>>由於澳洲對於EGS較早研究所以將澳洲的模擬與實驗做參考   物理模型建構>>建立一個尺度現地的模型 試驗系統設計>>試驗系統需要準備甚麼東西 實驗室取熱系統設置 Analysis Fig.2. flow chart of experimental 6

Test section  High pressure pump Data logger Heater CO2 cylinder Water bath Fig.3. Schematic diagram of experimental system 7

Experimental conditions Table.3. Operating conditions Experimental conditions Flow rate 10 mL/min、30 mL/min、40 mL/min、50 mL/min Pressure 2000psi、1500psi、1100psi Initial wall temperature 150℃、200℃ 8

1. where 𝑞 indicates the heat transfer rate of supercritical carbon dioxide, Qloss is heat loss. 2. where 𝑚 indicates the mass flow rate, hin is the inlet enthalpy, hout is the outlet enthalpy. 3. where ΔT1 indicates the temperature difference between inlet temperature and tube wall, ΔT2 is the temperature difference between outlet temperature and tube wall. 4. where A is inner surface of test section. 9

Results

(a) (b) Fig.4. Effects of Reynolds number on the heat transfer coefficient(a) and heat transfer rate(b) at pressure=2000 psi and temperature=150℃. 10

non (a) (b) Fig.5. Effects of pressure on the heat transfer coefficient(a) and heat transfer rate(b) at Re=7.6 and temperature=150℃. 11

(a) (b) Fig.6. Effects of temperature on the heat transfer coefficient(a) and heat transfer rate(b) at Re=6.3 and pressure=1100 psi.. 12

Conclusions In this study, the heat extraction of supercritical CO2 is investigated by various experimental conditions. The results show that the heat transfer coefficient increases as the flow rate increases. Moreover, the excellent heat extraction is shown in 1500 psi. 13

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