Experimental study on thermal performance of ethanol loop heat pipe with flat evaporator under gravity – assisted condition

Nowadays, extreme growing of telecommunication and information technology causes the significant changes in the electronics belonging to the high-performance computer, data centers that are miniaturizing in their size and increasing the heat power dissipation. As a result, it is important to study on new cooling methods rather than conventional air cooling to warrant electronic device operate durably and stably. Besides, saving electricity power consumed by cooling systems is another considerable concern. Loop heat pipe, a passive heat transfer device which functions based on phase change processes and natural forces like gravity or capillary force, has been being one of potential solutions for the above challenges. In this paper, a loop heat pipe with flat evaporator was fabricated to investigate its cooling characteristics during start-up, stable operating period at different heat loads under gravity–assisted condition. This loop heat pipe was charged with ethanol whereas sintered stainless steel wick was the capillary structure. Time for successful start-up shortened from 13 minutes to 4 minutes as heat load increased from 30 W to 225 W. When heating power supplied to loop heat pipe’s evaporator was adjusted from 30 W to 400 W (14.8 W/cm2), the heating block surface’s temperature increased from 33oC to 133oC. This temperature could be maintained below 85oC, electronics limitation temperature in industry, if heat power released from the heating block is smaller than 220 W (8.14 W/cm2). Besides, the change of different types of thermal resistance such as total thermal resistance, evaporator and condenser thermal resistances with heating power is discussed detail in this paper.