Development and investigation of a loop heat pipe at a high concentration of heat load

•A copper-water LHP with a flat evaporator was developed and investigated.•The study was conducted with heat sources with sizes of 0.25, 0.9, and 9 cm2.•Copper spreaders 1, 2 and 3 mm thick were used to reduce the heat source temperature.•It is shown that the maximum temperature drop is reached with a spreader 3 mm thick.•Numerical simulation of heat transfer in the evaporator active zone was performed. The problem of cooling small objects with extremely high heat fluxes, such as components of modern electronics and computer equipment, is solved. A copper-water loop heat pipe (LHP) is considered as an effective device for removing the heat they produce to a remote heat sink. The LHP with an effective heat transfer length of 360 mm was equipped with a flat-oval evaporator measuring 7 mm × 42 mm × 80 mm with an active zone of 32 mm × 40 mm. Experimental studies were conducted with three different-sized heat sources. Their thermal contact surface areas were 0.25 cm2, 0.9 cm2, and 9.0 cm2, respectively. In experiments, the highest value of the heat flux related to the area of 0.25 cm2 was 960 W/cm2. To intensify heat exchange processes in the evaporator, copper heat spreaders with a thermal contact surface of 30 mm × 30 mm and various thicknesses of 1, 2 and 3 mm were used. It has been demonstrated that heat spreaders can reduce the temperature of a heat source. The greatest decrease in temperature was observed at a heat source with a heating surface of 0.25 cm2. Numerical simulation of the temperature field of the evaporator with spreaders of different thicknesses was performed, which showed that the temperature decrease is achieved by a more efficient distribution of heat flows in the active zone of the evaporator.