Performance improvement of thermosyphon heat exchangers by using two kindsof working fluids

In this study, the concept of introducing two-fluid thermosyphons is examin ed. Calculations were performed for both low and high temperature ranges wi th parallel and counter-flow arrangements. For lower-temperature applicatio n, 125 degreesC > T-hi > 75 degreesC, use of ammonia in some rows and water in the rest of the thermosyphon can slightly improve the associated heat t ransfer performance for balanced counter-flow arrangement. However, for bal anced parallel-flow arrangement in both low-and high-temperature applicatio ns, the concept of using two-fluid thermosyphons may not be feasible. The u se of two-fluid thermosyphons is especially advantageous for high-temperatu re applications. For instance, in range of 375 degreesC > T-hi > 350 degree sC the two-fluid thermosyphons (Dowtherm A-water) shows a 15-99% increase o f heat transfer performance relative to Dowtherm A alone.