Critical heat flux and heat transfer in a thermosiphon with enhanced surfaces for boiling and condensation

The technology of solid-state light source is associated with the future of a number of sectors of economy. Duration of failure-free operation, optical radiation power and other output characteristics of the LEDs are closely linked with p-n junction temperature, which makes the development of the cooling systems an important step in creating LED systems. In this work, we have created a new type of thermosiphon for studying heat transfer from a local heat source. Boiling heat transfer on the local heaters with the diameter of 1 and 5 mm has been investigated. It is shown that on the finned surfaces overheating relative to the saturation temperature in comparison with a smooth surface decreases up to three times for the heater with the diameter of 5 mm. For finned surfaces on the heater with a diameter of 1 mm, surface overheating relative to the saturation temperature decreases four times. More than three times increase is observed for the heat transfer coefficient on finned surfaces as compared to the smooth ones. It is shown that the value of the critical heat flux (CHF) under the conditions of a large volume of liquid for the heaters with D = 1.6 and 5 mm is in good agreement with the known dependences. Radial finning of the heater has no effect on CHF. The value of CHF for D = 1 mm turns out to be higher than the calculated one. The greatest increase is achieved by using a head with finning.