Investigation of Nucleate Pool Boiling Heat Transfer of Water on Platinum Wire Under Hypergravity and Earth’s Gravity

The saturated nucleate pool boiling heat transfer of water on two platinum wires with 30 μm and 50 μm in diameter was experimentally investigated under Earth’s gravity and hypergravity up to 3.0 g, with the numerical simulation of bubble morphology. In the experiments, the saturation pressure ranges from 0.1 to 0.6 MPa and the heat flux from 0.2 to 1.8 MW/m 2 . The experimental results show that the pool boiling heat transfer coefficient (HTC) decreases with increasing gravity at low system pressure within the experimental gravity range. However, at a pressure higher than 0.3 MPa, no further decrease of the HTC with increasing gravity was observed when the gravity greater than certain value. Increasing saturation pressure enhances pool boiling heat transfer primarily due to that it reduces the critical radius of cavities so that more cavities are activated, leading to more nucleation sites. The HTC on the 30-μm diameter platinum wire is greater than that on the 50-μm diameter one, indicating that reduction in heater size slightly enhances pool boiling heat transfer because it leads to the reduction in surface tension force. The results of the numerical study show that the total gravity effect on pool boiling heat transfer is negative under hypergravity, which is caused by the combined effects of the diameter and frequency of bubble departure and vapor generation. The effects of pressure, gravity, heat flux, and heater size on pool boiling HTC are interacted, which makes it harder to understand the mechanisms of pool boiling heat transfer under hypergravity than under Earth’s gravity. Therefore, much more experimental and numerical studies on pool boiling heat transfer under hypergravity should be performed.