Experimental Study of Evaporator Surface Area Influence on a Closed Loop Pulsating Heat Pipe Performance

Pulsating Heat Pipes are an effective mean for heat removal with the potential for a widespread application in electronic packaging. An experimental study a Closed Loop Pulsating Heat Pipe (CLPHP) constructed of copper tubes formed into four meandering turns is presented. Once configured in a vertical orientation the lower portion of the CLPHP comes in contact with a heat source (called the evaporator) from which it will remove heat through the pulsating action of the two-phase mixture contained within the initially evacuated copper tubes eventually transfer the heat to a heat sink (known as the condenser). Heat fluxes can be measured using temperature data gathered from experiments. Thermocouples connected to the copper tubes at several locations provide this data. Experiments were conducted using deionized water as the working fluid. The surface area of the tubing which comes in contact with the heat source at the evaporator affects the heat removal rates. This effect was studied by varying the surface area in contact with the heat source while providing the same power input. Experiments were conducted using different filling ratios of working fluid (20–70%) for each case. The heat source (heating elements wound around the tubes) was supplied with different power inputs ranging from 10 to 40 W. Results indicate the surface area affects the pulsating action differently for each configuration because of its dependency on the flow regime. These results are presented for each flow regime. The results can be used to optimize the CLPHP according to the flow regime which it will be working in.