HR: 0800h
AN: H41F-0472    [Abstracts]
TI: Verification of Heat-Pulse Flowmeter Measurement in the Laboratory
AU: * Lee, T
EM: gnt0926@so-net.net.tw
AF: National Taiwan University, No.1, Sec. 4, Roosevelt Road, Taipei, TWN
AU: Chen, J
EM: cjs@ntu.edu.tw
AF: National Taiwan University, No.1, Sec. 4, Roosevelt Road, Taipei, TWN
AU: Jan, T
EM: r89224206@ms89.ntu.edu.tw
AF: National Taiwan University, No.1, Sec. 4, Roosevelt Road, Taipei, TWN
AU: Chia, Y
EM: ypc@ntu.edu.tw
AF: National Taiwan University, No.1, Sec. 4, Roosevelt Road, Taipei, TWN
AB: Heat-pulse flowmeter is a developing tool for direct measurement of flow velocity and hydraulic conductivity in a borehole. The flowmeter measures the temperature change between two thermisters when a pulse of heat is generated and transported by water flow from the central heating grid. The elapsed time for temperature change is used to calculate the flow velocity. In order to evaluate the performance and the limitations of heat-pulse flowmeter, we established a circulation system for the water flow through a pipe under constant head in the laboratory to simulate field measurement conditions. The system was designed to minimize errors due to turbulent flow and frictional loss. Based on the results of tests under various flow rates, an empirical formula is developed for calibrating the measured flow rate. The measurement precision is about 4% based on the standard deviation of 8 duplicate tests for a specified pumping rate. The error increases exponentially from approximately 5% to 50% as the flow rate decreases from 1.0 cm/sec to less than 0.2 cm/sec. Of various factors that affect measured flow velocity, we found that free convection plays an important role in driving the upward flow during the measurement, especially at a low flow velocity. Combining the measured results from both upward and downward flow experiments, however, it is possible to calibrate the value of flow velocity influenced by free convection.
DE: 1829 Groundwater hydrology
DE: 1835 Hydrogeophysics
SC: Hydrology [H]
MN: Fall Meeting 2005