Effect of Evaporator Lengths and Ratio of Check Valves to Number of Turns on Internal Flow Patterns of a Closed-Loop Oscillating Heat-Pipe With Check Valves

A visualization study of the internal flow patterns of a closed-loop oscillating heat-pipe with check valves (CLOHP/CV) at normal operating condition for several evaporator lengths (Le), and ratio of check valves to number of turns (Rcv) has been conducted. This article describes the effects of varying Le, and Rcv on flow patterns. The CLOHP/CV used a Pyrex glass tube with inside diameter of 2.4 mm. The evaporator length of 50 and 150 mm. (the lengths of evaporator, adiabatic and condenser were equal) were employed with 10 turns, with Rcv of 0.2 and 1. R123 was used as the working fluid with filling ratio of 50% of internal volume of tube. It was found that the internal flow patterns could be classified according to the Le and Rcv as follows: At the high heat source when the Le decreases the main flow changes from the bubble flow with slug flow to disperse bubble flow. The Rcv decreases the main flow changes from the disperse bubble flow with bubble flow to disperse bubble When the velocity of slug increases, the length of vapor bubbles rapidly decreases and the heat flux rapidly increases.