Lifetime evaluation of ultra-thin polymer pulsating heat pipe

The influence of gas penetration on the lifetime of an ultra-thin polymer pulsating heat pipe (PPHP) was studied experimentally using two types of PPHPs. One type was made with bare polyethylene terephthalate (PET) films and was 0.4 mm thick. The other was covered by gas-barrier films and was 0.48 mm thick. First we compared the performance degradation of the PPHPs made with bare PET films exposed to environments with difference air pressures. The performance of the PPHP exposed to an atmospheric-pressure degraded within a few days, whereas that of the PPHP exposed to a low-pressure environment was maintained for about one month. Next we exposed a PPHP covered by gas-barrier films to an atmospheric-pressure and evaluated its performance change. As a result, the performance of the PPHP with gas-barrier films didn't degrade for more than two weeks. These results show that the gas penetration is a dominant factor in the performance degradation of PPHPs and their lifetime can be increased by using gas-barrier films for their casing materials.