Experimental investigation of loop heat pipe with flat evaporator using biporous wick

In order to solve heat dissipation of electronic equipment, an experimental investigation was carried out on the thermal performance of a miniature stainless-steel-ammonia loop heat pipe (LHP) with a flat disk-shaped evaporator. A biporous wick made from nickel powder was used for developing the capillary force. Tests demonstrated that the device could start up at heat load as low as 2.5 W. Meantime, the maximum heat load the LHP could transfer reaches 130 W (heat flux 12.8 W/cm2) at the allowable evaporator temperature of below 60 °C. The LHP showed a very fast response to variable heat load and operated stably without obvious temperature oscillation. The evaporator surface has very high isothermality while the monitored temperature difference between the maximum and minimum value on the evaporator surface does not exceed 3 °C for heat load below 130 W. The operation modes of variable conductance and constant conductance are found in the whole tested heat load range. The total thermal resistance varies between 1.42 and 0.33 °C/W at heat load ranging from 10 to 130 W.

► A loop heat pipe with flat evaporator using biporous wick has been investigated.
► The wick with bimodal pore size distribution is fabricated.
► The evaporator surface has very high isothermality.
► The maximum heat flux reaches 13 W/cm2 for the evaporator temperature below 60 °C.
► The LHP shows fast response to heat load without obvious temperature oscillation.