Most geothermal fluids used for direct use purposes contain various chemical species which can be detrimental to conventional materials of construction. For this reason, the standard design practice is to isolate the geothermal fluid from the balance of the system through the use of a heat exchanger. In the majority of applications, the plate and frame heat exchanger has been the design of choice for this duty. Plate and frame heat exchangers offer many advantages for geothermal applications including their availability in corrosion resistant materials (stainless steel, titanium, etc.) at reasonable cost. In addition, their design permits disassembly for cleaning or the addition of plates to accommodate increased heating loads. The units are very compact and efficient with heat transfer rates 3 to 10 times those of shell and tube exchangers