Development of Groundwater Flowmeter: A Way to Estimate an Amount of Heat Collected by Geothermal Heat Pumps

Abstract

The paper describes development of groundwater flowmeter, which measures both velocity and flowing direction with a single borehole. The information about groundwater velocity is important in order to estimate heat transfer rates from the flowing groundwater to heat exchangers buried in the ground. In fact it can be shown that the heat transfer rate is proportional to a square root of groundwater velocity. The developed probe makes use of steady state temperature patterns around a small cylindrical heat source, which makes the present technique unique comparing with other proposed or existing methods. Calibration tests prove that the probe can detect the horizontal water velocity as low as 0.001mm/s, and as high as 1mm/s. The field tests also show a good capability of the present measurement system for detecting groundwater velocity and flowing direction with a single borehole.