New Applications of Geothermal Heat Exchangers

Abstract

Over the last three years practical experience has been gained utilizing silica super-saturated geothermal waters in heat exchangers. Both shell - and- tube and plate heat exchangers have been used successfully in the seapplications, at Wairakei and Taupo, for space heating with a group heating system, and for a swimming pool complex. The performance of these heat exchangers is important, especially with regard to the low rate of silica deposition which has been seen , as use of such silica saturated waters could become more common in the future. Practical experience has a l s o been gained using plate heat exchangers for the condensation of geothermal steam and phase steam-water mixtures. A small plate heat exchanger condensing geothermal steam, at Broadlands, has operated without any problems on a corrosion pilot plant. High overall coefficients are reported for the condensation of geothermal steam in this plate heat exchanger. In Rotorua over the last few years , plate heat exchangers have been adopted for condensing the two- phase mixtures or the total flow from medium enthalpy wells. Initially one practical difficulty was preventing calcite deposition at the geothermal inlet ports. This can now be resolved by improved control of the geothermal flow.