Vapor/Droplet Coupling and the Mist Flow (OTEC) Cycle

1983 ◽  
Vol 105 (2) ◽  
pp. 181-186 ◽  
Author(s):  
C. K. B. Lee ◽  
S. L. Ridgway
Keyword(s):  
Interaction Parameter ◽  
Liquid Fraction ◽  
Energy Coupling ◽  
Vapor Flow ◽  
Two Phase ◽  
Slip Ratio ◽  
Mist Flow ◽  
High Vapor ◽  
Ocean Thermal Energy ◽  
Momentum Coupling

The present experiments have demonstrated that water droplets (∼200-μm dia) can be lifted to substantial heights (∼50 m) by their own vapor produced in flashing over temperature differences typical of the tropical seas. The coupling between the vapor and droplets is found to be excellent. The efficiency for momentum coupling is over 90 percent, and that for energy coupling is shown to vary inversely with the slip ratio. For the conditions in the present experiments, it varies from 50 to 80 percent. The momentum transfer is correlated with an interaction parameter which is the product of the liquid fraction, the slip, and the amount of flashing. For the high vapor flow cases, the pressure difference across the lift column is found to be proportional to the interaction parameter. The relevance of the two-phase flow to a class of open-cycle ocean thermal energy conversion (OTEC) schemes is considered, and the implications of the observed strong vapor/droplet coupling to the feasibility of the mist-flow OTEC cycle are discussed.

scholarly journals Maximum Flow Rate of a Single Component, Two-Phase Mixture

1965 ◽  
Vol 87 (1) ◽  
pp. 134-141 ◽  
Author(s):  
F. J. Moody
Keyword(s):  
Flow Rate ◽  
Static Pressure ◽  
Maximum Flow ◽  
Single Component ◽  
Maximum Flow Rate ◽  
Vapor Flow ◽  
Two Phase ◽  
Slip Ratio ◽  
Phase Mixture ◽  
Local Slip

A theoretical model is developed for predicting the maximum flow rate of a single component, two-phase mixture. It is based upon annular flow, uniform linear velocities of each phase, and equilibrium between liquid and vapor. Flow rate is maximized with respect to local slip ratio and static pressure for known stagnation conditions. Graphs are presented giving maximum steam/water flow rates for: local static pressures between 25 and 3,000 psia, with local qualities from 0.01 to 1.00; local stagnation pressures and enthalpies which cover the range of saturation states.

Two Phase Flow Patterns and Cooling Power of Mixed Refrigerant in Micro Cryogenic Coolers

2012 ◽  
Author(s):  
Ryan Lewis ◽  
Hayley Schneider ◽  
Yunda Wang ◽  
Ray Radebaugh ◽  
Y. C. Lee
Keyword(s):  
Liquid Flow ◽  
High Speed ◽  
Single Phase ◽  
Liquid Fraction ◽  
Cryogenic Cooling ◽  
Cooling Power ◽  
Vapor Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Power Draw

Micro cryogenic coolers (MCCs) operating in the Joule-Thomson cycle with mixed refrigerants offer an attractive way to decrease the size, cost, and power draw required for cryogenic cooling. Recent studies of MCCs with mixed refrigerants have, when employing pre-cooling, shown pulsating flow-rates and oscillating temperatures, which have been linked to the refrigerant flow regime in the MCC. In this study we investigate those flow regimes. Using a high-speed camera and optical microscopy, it is found that the pulsations in flow correspond to an abrupt switch from single-phase vapor flow to single-phase liquid flow, followed by 2-phase flow in the form of bubbles, liquid slugs, and liquid slug-annular rings. After this period of 2-phase flow, the refrigerant transitions back to single-phase vapor flow for the cycle to repeat. Under different pre-cooling temperatures, the mole fraction of the vapor-phase refrigerant, as measured by molar flow-rate, agrees reasonably well with the quality of the refrigerant at that temperature as calculated by an equation of state. The frequency of pulsation increases with liquid fraction in the refrigerant, and the volume of liquid in each pulse only weakly increases with increasing liquid fraction. The cooling power of the liquid-flow is up to a factor of 7 greater than that of the 2-phase flows and single-phase vapor flow.

Momentum coupling effects in a two-phase swirling jet

1997 ◽  
Author(s):  
T. Park ◽  
S. Aggarwal ◽  
V. Katta ◽  
T. Park ◽  
S. Aggarwal ◽  
...  
Keyword(s):  
Coupling Effects ◽  
Two Phase ◽  
Swirling Jet ◽  
Momentum Coupling

Determination of specific interfacial areas in swirled two-phase flow

1983 ◽  
Vol 48 (3) ◽  
pp. 842-853
Author(s):  
Kurt Winkler ◽  
František Kaštánek ◽  
Jan Kratochvíl
Keyword(s):  
Interfacial Area ◽  
Liquid Volume ◽  
Upward Flow ◽  
Two Phase ◽  
Flow Rates ◽  
Mist Flow ◽  
Interfacial Areas ◽  
Correlation Parameters ◽  
Flow Components

Specific gas-liquid interfacial area in flow tubes 70 mm in diameter of the length 725 and 1 450 mm resp. containing various swirl bodies were measured for concurrent upward flow in the ranges of average gas (air) velocities 11 to 35 ms-1 and liquid flow rates 13 to 80 m3 m-2 h-1 using the method of CO2 absorption into NaOH solutions. Two different flow regimes were observed: slug flow swirled annular-mist flow. In the latter case the determination was carried out separately for the film and spray flow components, respectively. The obtained specific areas range between 500 to 20 000 m3 m-2. Correlation parameters are energy dissipation criteria, related to the geometrical reactor volume and to the static liquid volume in the reactor.

An Experimental Study of Mist/Air Film Cooling With Fan-Shaped Holes on an Extended Flat Plate—Part II: Two-Phase Flow Measurements and Droplet Dynamics

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Reda Ragab ◽  
Ting Wang
Keyword(s):  
Flow Behavior ◽  
Data Rate ◽  
Main Flow ◽  
Shear Stresses ◽  
Two Phase ◽  
Flow Measurements ◽  
Droplet Dynamics ◽  
Mist Flow ◽  
Film Layer ◽  
Upper Boundary

A phase Doppler particle analyzer (PDPA) system is employed to measure the two-phase mist flow behavior including flow velocity field, droplet size distribution, droplet dynamics, and turbulence characteristics. Based on the droplet measurements made through PDPA, a projected profile describing how the air–mist coolant jet flow spreads and eventually blends into the hot main flow is prescribed for both cylindrical and fan-shaped holes. The mist film layer consists of two layers: a typical coolant film layer (cooling air containing the majority of the droplets) and a wider droplet layer containing droplets outside the film layer. Thanks to the higher inertia possessed by larger droplets (>20 μm in diameter) at the injection hole, the larger droplets tend to shoot across the coolant film layer, resulting in a wider droplet layer than the coolant film layer. The wider droplet layer boundaries are detected by measuring the droplet data rate (droplet number per second) distribution, and it is identified by a wedge-shaped enclosure prescribed by the data rate distribution curve. The coolant film layer is prescribed by its core and its upper boundary. The apex of the data rate curve, depicted by the maximum data rate, roughly indicates the core region of the coolant film layer. The upper boundary of the coolant film layer, characterized by active mixing with the main flow, is found to be close to relatively high values of local Reynolds shear stresses. With the results of PDPA measurements and the prescribed coolant film and droplet layer profiles, the heat transfer results on the wall presented in Part I are re-examined, and the fundamental mist-flow physics are analyzed. The three-dimensional (3D) droplet measurements show that the droplets injected from the fan-shaped holes tend to spread wider in lateral direction than cylinder holes and accumulate at the location where the neighboring coolant film layers meet. This flow and droplet behavior explain the higher cooling performance as well as mist-enhancement occurs between the fan-shaped cooling holes, rather than along the hole's centerline as demonstrated in the case using the cylindrical holes.

Moisture Fraction Measurements for Two-Phase Mist Flow Using High-Sensitivity Capacitance Sensors

1997 ◽  
Vol 117 (3) ◽  
pp. 353-365 ◽  
Author(s):  
Michael F. Dowling ◽  
Jason D. Wartell ◽  
Sheldon M. Jeter ◽  
Said I. Abdel-Khalik
Keyword(s):  
High Sensitivity ◽  
Two Phase ◽  
Mist Flow

The Effect of Droplet Solidification Upon Two-Phase Nozzle Flow

1971 ◽  
Vol 93 (4) ◽  
pp. 594-602
Author(s):  
P. N. Shankar
Keyword(s):  
Singular Perturbation ◽  
Phase Change ◽  
Liquid Fraction ◽  
Feedback Effect ◽  
Nozzle Flow ◽  
Phase Flow ◽  
Droplet Temperature ◽  
Two Phase ◽  
First Order ◽  
Perturbation Procedure

The handling of changes of phase in perturbation treatments of two-phase nozzle flow requires particular care. Droplet solidification, the phase change considered here, introduces two novel complications in a perturbation treatment of the problem. First, the boundaries of the zone of solidification are shifted by first-order corrections to the droplet temperature and liquid fraction, and these shifts introduce, in turn, further first-order corrections. This feedback effect is of particular interest and the magnitudes of the corrections are very significant. Second, a singular perturbation procedure is required to handle the problem at points where solidification first starts and where it is completed. The techniques presented here should be applicable to other problems involving phase change in two-phase flow.

Condensation of Steam on Finned Surfaces With Addition of a Surfactant

2005 ◽  
Author(s):  
Andrew T. Morrison ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Surface Energy ◽  
Reynolds Numbers ◽  
Film Condensation ◽  
Vapor Flow ◽  
Flow Conditions ◽  
Two Phase ◽  
Enhancement Of Heat Transfer ◽  
Flat Surfaces ◽  
Extended Surfaces

A fundamental knowledge of the parameters affecting film condensation is essential for the design of two phase heat exchangers. The current study examines the effect of extended surfaces and surface energy modifications and their interaction for condensation of steam in quiescent and vapor flow conditions. The enhancement of heat transfer for vertical, flat surfaces and two finned surfaces were compared for Reynolds numbers ranging from approximately 10 to 50. The addition of a nonionic surfactant, alcohol alkoxylate, to the system was evaluated for the same surfaces and vapor field conditions. Vapor flow of 0.25 m/s enhanced the heat transfer approximately 40%, while 0.5 m/s vapor velocity produced almost 100% increase in heat transfer. The addition of surfactant to the system produced small enhancement in heat transfer except in the case of condensate hold-up between the fins. In this case, the addition of surfactant increase the heat transfer an additional 25%, likely because the vapor flow and change of surface energy were sufficient to largely eliminate the hold-up of condensate between the fins.

scholarly journals Level-set simulations of a 2D topological rearrangement in a bubble assembly: effects of surfactant properties

2018 ◽  
Vol 838 ◽  
pp. 222-247 ◽  
Author(s):  
A. Titta ◽  
M. Le Merrer ◽  
F. Detcheverry ◽  
P. D. M. Spelt ◽  
A.-L. Biance
Keyword(s):  
Level Set ◽  
Liquid Fraction ◽  
Two Phase ◽  
Order Unity ◽  
Surfactant Properties ◽  
Surface Active Agents ◽  
Adsorption Desorption ◽  
Work Done ◽  
Foam Rheology

A liquid foam is a dispersion of gas bubbles in a liquid matrix containing surface-active agents. Its flow involves the relative motion of bubbles, which switch neighbours during a so-called topological rearrangement of type 1 (T1). The dynamics of T1 events, as well as foam rheology, have been extensively studied, and experimental results point to the key role played by surfactants in these processes. However, the complex and multiscale nature of the system has so far impeded a complete understanding of the mechanisms involved. In this work, we investigate numerically the effect of surfactants on the rheological response of a 2D sheared bubble cluster. To do so, a level-set method previously employed for simulation of two-phase flow has been extended to include the effects of surfactants. The dynamical processes of the surfactants – diffusion in the liquid and along the interface, adsorption/desorption at the interface – and their coupling with the flow – surfactant advection and Laplace and Marangoni stresses at the interface – are all taken into account explicitly. Through a systematic study of the Biot, capillary and Péclet numbers that characterise the surfactant properties in the simulation, we find that the presence of surfactants can affect the liquid/gas hydrodynamic boundary condition (from a rigid-like situation to a mobile one), which modifies the nature of the flow in the volume from a purely extensional situation to a shear. Furthermore, the work done by surface tension (the 2D analogue of the work by pressure forces), resulting from surfactant and interface dynamics, can be interpreted as an effective dissipation, which reaches a maximum for a Péclet number of order unity. Our results, obtained at high liquid fraction, should provide a reference point, with which experiments and models of T1 dynamics and foam rheology can be compared.

Sign in / Sign up

Export Citation Format

Share Document