Heat Transfer Consideration in Utilizing Geothermal Energy

Abstract

Although some forms of geothermal energy will require the application of high temperature technology, most involve only low temperatures. This paper emphasized the importance of efficient, low cost heat exchangers in the use of low temperature sources and in the waster heat rejection systems of power generation cycles. Results of recent heat transfer development work at ORNL show that for working fluids which are attractive for use in these cycles the condensation heat transfer effectiveness can be improved by a factor of from 3 to 7 by the use of fluted tubes an condensate drain off skirts. Data are presented for condensation of six fluorocarbons, isobutane, and ammonia on a variety of tube surfaces. These result are being applied to the design of a 40 tube heat exchanger to be tested in a geothermal energy test facility.