An experimental investigation of the heat transfer capability and thermal performance of dual layer pulsating heat pipes

An experimental investigation on pulsating heat pipes with dual-layer and single layer configurations was conducted in order to determine the effect of the heat transfer and over-all system performance given a constrained dimensional heat source with dual-layer arrangement. The dual layer configuration is an assembly of two pulsating heat pipes of equal measurement connected with a cross linking tube, allowing them to operate using the same working fluid. The dual-layer system was compared to the base single-layer system on several different accounts, including start-up time and temperature, the average/minimum/ and maximum evaporator temperature during steady state operation, the over-all heat transfer capability, as well as the over-all thermal resistance of the system. These requirements were reviewed at different fill ratios: 0%, 25%, 75%, and 90%. The dual layer system attained the lowest thermal resistance of 0.12 ºC/W at a fill ratio of 75%, while also maintaining an average evaporator temperature of 85 degrees Celsius at an input power of 120 Watts, versus 110 degrees Celsius for the Single Layer configuration at its most efficient fill ratio of 50% and a thermal resistance of 0.85 ºC/W and input power of 120 Watts. It was concluded that the dual-layer system exposed to the same watt-density and area achieved an over all increase in performance in respect to start-up time and temperature, showing start-up oscillation temperatures as low as 73 degrees Celsius, compared to the 88 degrees Celsius required to observe temperature oscillation in the SLPHP