Phase-change heat transfer involves the exchange of thermal energy when a substance transitions between different phases, such as solid to liquid (melting), liquid to vapor (boiling), or vice versa. During phase-change, energy is absorbed or released without a change in temperature. In particular, boiling is highly efficient due to the large latent heat of vaporization, allowing for dissipative heat fluxes on the order of q′′ ∼ 10–100 W/cm². However, during boiling, once the temperature exceeds a critical threshold, a vapor film forms between the heated surface and the liquid, suppressing effective nucleate boiling which reduces heat transfer efficiency so that q′′ ∼ 1 W/cm². This critical temperature limitation prompted our exploration of three-phase heat transfer. In three-phase heat transfer, energy is transferred between the solid, liquid, and vapor phases; all of which coexist simultaneously. In this study, we define and investigate three-phase heat transfer by examining ice on a superheated substrate. We explore the use of ice as a quenchant and our findings indicate that dissipative heat fluxes for our three-phase system are an order of magnitude larger than for classical boiling (q′′ ∼ 1,000 W/cm²). This is due to the inherent 100 °C temperature differential across the meltwater film, which dissipates q′′ ∼ 100 W/cm² via conduction (and subsequent ice melting) and an additional q′′ ∼ 100 W/cm² for sensible heating of the meltwater. We propose experiments to measure the dissipative heat flux of a tall and pressurized ice column during three-phase heat transfer. Furthermore, we discuss potential avenues for future research of three-phase heat transfer at high superheats. / Master of Science / Phase-change heat transfer involves the exchange of heat when a substance transitions between different phases, such as solid to liquid (melting), liquid to vapor (boiling), or vice versa. During phase-change, energy is absorbed or released without a change in temperature. For example, in boiling, water molecules act like tiny magnets. When water changes from one phase to another, the distance between these tiny magnets changes. When they are pulled apart, like when water turns into steam, they need some extra energy to do that. This energy, termed latent heat, is the reason lots of heat can be transferred during phase-change. However, during boiling, once the temperature of the heated surface exceeds a critical threshold, a vapor film forms between the heated surface and the liquid, which suppresses effective boiling and reduces the efficiency. This critical temperature limitation prompted our exploration of three-phase heat transfer. In three-phase heat transfer, energy is transferred between the solid, liquid, and vapor phases; all of which coexist simultaneously. In this study, we define and investigate three-phase heat transfer by observing ice on a heated surface. The vapor film is avoided for a while because a majority of the heat is used to melt the ice and warm the meltwater, leaving only a little left for vaporization. We propose experiments to measure the heat transfer capabilities of a tall ice column pressed into a heated surface. Furthermore, we discuss potential avenues for future research of three-phase heat transfer at high superheats.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/119008 |
| Date | 16 May 2024 |
| Creators | Colon, Camryn Luz |
| Contributors | Mechanical Engineering, Boreyko, Jonathan Barton, Lattimer, Brian Y., Paul, Mark R. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf, application/pdf, application/pdf, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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