Towards an optimal design of Heat Pipe Equipped Heat Exchangers

Introduction
The working of a heat pipe (thermosyphon) is based on a continuous cycle of evaporation and condensation of a working uid,here R134a. The goal of this study is to gain knowledge about heat pipes in general and to develop an operational model for the optimization of heat pipe equipped heat exchangers.

Detailed research is carried out to nd the operating limits,optimum lling degree and limitations with regard to the inclination angle of a long heat pipe of 3 m length and diameter 16 mm. Renements of predictive models of a thermosyphon are assessed with lling ratios of 25%, 62% and 100% R-134a.
Saturation temperatures varied from 20 to 75℃and inclination angles with the vertical varied from 0 to 87o. Measurements and predictions of a small scale heat pipe-equipped heat exchanger with two lling ratios of R134a, 19% and 59%, are assessed. The airow rate varied from 0.4 to 2.0 kg=s. The temperatures at the evaporator side of the heat pipe varied from 40 to 70℃ and at the condenser part from 20 to 50℃.