Heat extraction from the ground in a volcanic zone using copper water heat pipes—experiment and analysis Original Research Article

This test of the technical feasibility of extracting heat from the earth of a volcanic zone and delivering it to water-utilizing heat pipes was conducted at Tsukahara Hot Spring in Kyushu, Japan, in July 1992. The temperature distributions of the heat pipes and the surrounding earth were analyzed through an equivalent thermal network-a three-dimensional circuit of thermal resistances and capacitors taking account of the mass transfer—and did not show much agreement with the experimental data. The calculated values of the heat transport, taking account of the mass transfer, agreed well with the experimental ones in the steady state, assuming the thermal conductivity of the earth. But a discrepancy arose in the unsteady state during startup. There are many problems to be overcome in this area of natural phenomena. Earth more than 0.15 m away from the heat pipe was not affected during the test.