“…Heat pipe that is a compact and effective heat exchanger includes microchannel heat pipe, mesh wick heat pipe, sintered core heat pipe, oscillating heat pipe and thermosyphon heat pipe, and other heat pipe forms [31]. The researchers conducted experimental studies on different types of nanofluids such as Al 2 O 3 [32,33], CuO [34,35], SiO 2 [36,37], Fe 2 O 3 [38,39], and graphene nanosheets [40][41][42] in heat pipes. The results indicated that nanofluids can enhance heat transfer of the heat pipes.…”