Heat Transfer to Ultralarge-scale Heat Pipes Placed in a Geothermal Reservoir (1st report)

Abstract

The concept of geothermal energy development using ultralarge-scale heat pipes is briefly described. A simple way to estimate the heat transfer rate to heat pipes placed in upwelling geothermal fluids within geothermal reservoir is presented. First, effective thermodynamic and hydrodynamic parameters for a reservoir are evaluated. Then, similar transformations are locally implemented in order to compute the rate of heat transfer to the heat pipes in the uniform porous medium. Two slightly different transformations were developed locally. Both of them were extensively tested against the complete two-dimensional numerical results: the validity was confirmed. According to the present analyses, the heat transfer rate to an evaporator with 0.1 m in radius and 1 km in length can be as large as 1600 kW, if a 200 K temperature difference between the evaporator and geothermal fluids is maintained over the entire length and the flow velocity is 1 mm/sec.