Flower Shape Oscillating Heat Pipe – A novel type of oscillating heat pipe in a rotary system of coordinates – An experimental investigation

Abstract

A special type of oscillating heat pipe in a rotary system of coordinates, called a Flower Shape Oscillating Heat Pipe (FSOHP) was experimentally investigated. The unique rotary experimental set-up consists of 8 horizontal bends located on the bottom (evaporator) and the top (condenser), respectively, which were connected by a 1.1m long vertical quasi-adiabatic section of capillaries with an internal diameter of 2.7mm and filled with de-ionized water. In the performed research various rotational speeds, from 0 to 300rpm and heat loads of between 1.5 and 2.0kW (from 73.8 to 98.4kW/m2) were studied with a different volumetric Filling Ratio (FR) of 50,70 and 80%. The experimental results have shown that a higher temperature amplitude in the rotary system is associated with obtaining the appropriate level of pressure required to cause the slug-plug internal displacement flow, in the direction of from the evaporator to the condenser. This phenomenon directly affects the increase in the flow rate of the Working Fluid (WF). By obtaining Start-Up (SU) conditions, the type of flow pattern changes from oscillatory to directional, always fixed in a clockwise direction. It was found that the heat transport capabilities of the FSOHP improve as the centrifugal acceleration increases up to 5g. In these conditions, the tested device reached a minimum thermal resistance of 0.012°C/W with a heat load of 2kW and FR=70%.