Use of Promoter Pipe with Downhole Heat Exchangers in Klamath Falls, Oregon

摘要

Downhole heat exchangers (DHE) consists of a system of pipes or tubes suspended in a well through which "clean" secondary water is pumped or allowed to circulate by natural convection to provide space heating of buildings. The DHE eliminates the problem of disposal of geothermal fluid, since only heat is taken from the well. DHEs are used extensive in approximately 600 wells in Klamath Falls, Oregon. Corrosion has been a problem for the DHE pipes, especially at the air-water interface, with the use of cross-linked polyethylene (PEX) pipes currently being investigated to solve this problem. In order to increase the heat output from a well using a DHE, a vertical convection cell is developed by perforating the casing at the bottom of "live water" flow and just below the lowest static water surface. Where these perforations have not been provided, typical of older wells, pumping and dumping water to the storm sewers in Klamath Falls has been utilized. This disposal of geothermal water had lowered well water throughout the City. A City ordinance in 1990 stopped the "pumpers and dumpers" to correct this water level decline thus, alternate solutions had to be found. Using experience from Rotorua, New Zealand with convection promoter pipes, an experimental project with initiated at the Klamath Medical Clinic where a pump had been utilized to increase the vertical temperature in the well and the pumped water wasted to the storm sewer. A 4-inch (10-cm) diameter promoter pipe was installed in the well that had cooled in the upper portion due to lack of vertical circulation after the pump had been shut down. The promoter pipe increased the water temperature in the upper portion of the well and thus the DHE provided adequate heat to the Clinic. This solution for the "pumpers and dumper" will be tried elsewhere in the Klamath Falls area.