Developing flow pattern maps for accelerated two-phase capillary flows
| Autor: | Daniele Mangini, Marco Marengo, Mauro Mameli, Luca Pietrasanta, Sauro Filippeschi, Anastasios Georgoulas, Nicholas Michè |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Capillary action
General Chemical Engineering Bubble Diabatic Aerospace Engineering 02 engineering and technology 01 natural sciences 010305 fluids & plasmas Physics::Fluid Dynamics symbols.namesake 020401 chemical engineering Pulsating slug flow 0103 physical sciences Froude number Mass flow rate Bubble length Visual investigation 0204 chemical engineering Fluid Flow and Transfer Processes Physics Coalescence (physics) Mechanical Engineering Flow pattern maps Mechanics Nuclear Energy and Engineering Heat transfer symbols Two-phase flow |
| Popis: | The prediction of flow pattern transitions is extremely important to understand the coupling of thermal and fluid dynamic phenomena in two phase systems and it contributes to the optimum design of heat exchangers. Two phase flow regimes have been extensively studied under controlled mass flow rate and velocity. On the other hand, less effort has been spent in the literature on the cases where the flow motion is purely thermally induced and consequently the mass flow rate or the velocity of the phases are not known a priori. In the present work, flow pattern transitions and bubble break-up and coalescence events have been investigated in a passive two phase wickless capillary loop, where the mass flow rate is intrinsically not controllable. Modified Froude, Weber and Bond numbers have been introduced, considering the actual acceleration of the fluid and the length of the bubble as merit parameters for the transitions. The proposed nondimensional investigation was developed by analysing experimental data obtained with ethanol and FC-72, as working fluids, different heat input levels (from 9 to 24 W) as well as three different gravity levels (through a parabolic flight campaign). A new empirical diabatic flow pattern map for accelerated two-phase capillary flows is presented, together with quantitative criteria for the calculation of the flow regime transitions, defining the physic limits for the bubble coalescence and break-up. This kind of new regime maps will be useful to the further development of comprehensive designing tools for passive two-phase wickless heat transfer devices. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|