Two-Phase Vessel Blowdown of an Initially Saturated Liquid—Part 1: Experimental

1983 ◽  
Vol 105 (4) ◽  
pp. 687-693 ◽  
Author(s):  
M. N. Hutcherson ◽  
R. E. Henry ◽  
D. E. Wollersheim
Keyword(s):  
Pressure Vessel ◽  
Large Diameter ◽  
Small Diameter ◽  
Nonuniform Distribution ◽  
Superheated Liquid ◽  
Critical Flow ◽  
Saturated Liquid ◽  
Two Phase ◽  
Saturated Water ◽  
Liquid Part

Experimental blowdown results for initially isothermal, saturated water from a small pressure vessel containing internal geometry are presented. This experiment simulated a break in a large duct of approximately three diameters in length which exited from the vessel. Choking only occurred at the exit of the discharge duct, and the instantaneous internal vessel pressure distribution was nearly uniform. Most of the fluid within the vessel immediately after the initiation of the blowdown became superheated liquid. This thermodynamic state together with the activated wall cavities inside the vessel maintained a nearly constant internal vessel pressure history early in the blowdown. However, in the latter stage of the depressurization, the remaining fluid within the vessel was essentially in thermodynamic equilibrium. A nonuniform distribution of fluid quality within the vessel was also detected in this experiment. In addition, this experiment illustrates that transient, two-phase, critical flow in large diameter ducts is similar to steady, two-phase, critical flow in small diameter ducts.

Two-Phase Critical Flow under Diabatic Conditions

1969 ◽  
Vol 184 (3) ◽  
pp. 127-133
Author(s):  
A. E. Bergles ◽  
J. T. Kelly
Keyword(s):  
Experimental Investigation ◽  
Equilibrium Model ◽  
Small Diameter ◽  
Critical Flow ◽  
Subcooled Boiling ◽  
Flow Conditions ◽  
Two Phase ◽  
Wide Range ◽  
Good Agreement ◽  
Non Equilibrium

This paper summarizes an experimental investigation of steam-water critical flow in heated tubes. A wide range of data was taken for water at pressures below 100 lbf/in2 (abs.) in tubes of small diameter. It is demonstrated that critical flow conditions can occur in subcooled boiling at low exit subcoolings. At equilibrium qualities below about 0·04, the data differ significantly from adiabatic data for a similar exit geometry. The deviations can be explained in terms of the additional non-equilibrium effects present in heated flows. For higher qualities, the diabatic data are in good agreement with adiabatic data, and can be approximately predicted by a slip equilibrium model.

Two-Phase Vessel Blowdown of an Initially Saturated Liquid—Part 2: Analytical

1983 ◽  
Vol 105 (4) ◽  
pp. 694-699 ◽  
Author(s):  
M. N. Hutcherson ◽  
R. E. Henry ◽  
D. E. Wollersheim
Keyword(s):  
Bubble Growth ◽  
Growth Analysis ◽  
Initial Period ◽  
Saturation Pressure ◽  
Equilibrium Analysis ◽  
Analytical Models ◽  
Superheated Liquid ◽  
Saturated Liquid ◽  
Two Phase ◽  
System Pressure

Analytical models are presented to predict the internal vessel conditions during the decompression regimes of an initially saturated liquid. A subcooled blowdown analysis considers the elasticity of both the liquid and vessel. A bubble growth analysis for the intermediate period of blowdown is based on thermally dominated bubble growth from a solid surface into a superheated liquid. A dispersed analysis for the latter decompression period assumes the vapor bubbles have grown sufficiently so the liquid is uniformly distributed within the vapor phase. The sub-cooled analysis predicts the initial period of blowdown reasonably well. The bubble growth analysis predicts the rise in system pressure above that value to which it initially falls after the end of subcooled blowdown. It considers an initially “slow” depressurization rate (less than 400 MPa/s) where nucleation and bubble growth is the dominate volume producing, and thus pressure recovery, mechanism. It provides insight into why the system pressure initially drops below the saturation pressure, and it also offers an explanation for the subsequent recovery of the system pressure toward the saturation pressure. The thermodynamic equilibrium analysis provides a reasonable prediction of the latter stage of decompression. The combination of these three models predicts the overall two-phase decompression phenomenon reasonably well.

Two-Phase Microchannel Heat Sinks: Theory, Applications, and Limitations

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Issam Mudawar
Keyword(s):  
Flow Boiling ◽  
Large Diameter ◽  
Turbine Blades ◽  
Small Diameter ◽  
Jet Impingement ◽  
Heat Sinks ◽  
Geometrical Parameters ◽  
Two Phase ◽  
Microchannel Heat Sinks ◽  
Small Channels

Boiling water in small channels that are formed along turbine blades has been examined since the 1970s as a means to dissipating large amounts of heat. Later, similar geometries could be found in cooling systems for computers, fusion reactors, rocket nozzles, avionics, hybrid vehicle power electronics, and space systems. This paper addresses (a) the implementation of two-phase microchannel heat sinks in these applications, (b) the fluid physics and limitations of boiling in small passages, and effective tools for predicting the thermal performance of heat sinks, and (c) means to enhance this performance. It is shown that despite many hundreds of publications attempting to predict the performance of two-phase microchannel heat sinks, there are only a handful of predictive tools that can tackle broad ranges of geometrical and operating parameters or different fluids. Development of these tools is complicated by a lack of reliable databases and the drastic differences in boiling behavior of different fluids in small passages. For example, flow boiling of certain fluids in very small diameter channels may be no different than in macrochannels. Conversely, other fluids may exhibit considerable “confinement” even in seemingly large diameter channels. It is shown that cutting-edge heat transfer enhancement techniques, such as the use of nanofluids and carbon nanotube coatings, with proven merits to single-phase macrosystems, may not offer similar advantages to microchannel heat sinks. Better performance may be achieved by careful optimization of the heat sink’s geometrical parameters and by adapting a new class of hybrid cooling schemes that combine the benefits of microchannel flow with those of jet impingement.

Two-Phase Micro-Channel Heat Sinks: Theory, Applications and Limitations

2011 ◽  
Author(s):  
Issam Mudawar
Keyword(s):  
Flow Boiling ◽  
Large Diameter ◽  
Turbine Blades ◽  
Small Diameter ◽  
Jet Impingement ◽  
Heat Sinks ◽  
Geometrical Parameters ◽  
Micro Channel ◽  
Two Phase ◽  
Small Channels

Boiling water in small channels that are formed along turbine blades has been examined since the 1970s as a means to dissipating large amounts of heat. Later, similar geometries could be found in cooling systems for computers, fusion reactors, rocket nozzles, avionics, hybrid vehicle power electronics, and space systems. This paper addresses (a) the implementation of two-phase micro-channel heat sinks in these applications, (b) the fluid physics and limitations of boiling in small passages, and effective tools for predicting the thermal performance of heat sinks, and (c) means to enhance this performance. It is shown that despite many hundreds of publications attempting to predict the performance of two-phase micro-channel heat sinks, there are only a handful of predictive tools that can tackle broad ranges of geometrical and operating parameters or different fluids. Development of these tools is complicated by a lack of reliable databases and the drastic differences in boiling behavior of different fluids in small passages. For example, flow boiling of certain fluids in very small diameter channels may be no different than in macro-channels. Conversely, other fluids may exhibit considerable ‘confinement’ even in seemingly large diameter channels. It is shown that cutting-edge heat transfer enhancement techniques, such as the use of nano-fluids and carbon nanotube coatings, with proven merits to single-phase macro systems, may not offer similar advantages to microchannel heat sinks. Better performance may be achieved by careful optimization of the heat sink’s geometrical parameters and by adapting a new class of hybrid cooling schemes that combine the benefits of micro-channel flow with those of jet impingement.

Analysis of Two-Phase Tests in Large-Diameter Flow Lines in Prudhoe Bay Field

1981 ◽  
Vol 21 (03) ◽  
pp. 363-378 ◽  
Author(s):  
James P. Brill ◽  
Zelimir Schmidt ◽  
William A. Coberly ◽  
John D. Herring ◽  
David W. Moore
Keyword(s):  
Flow Pattern ◽  
Slug Flow ◽  
Pressure Loss ◽  
Large Diameter ◽  
Small Diameter ◽  
Liquid Holdup ◽  
Flow Lines ◽  
Two Phase ◽  
Diameter Pipe ◽  
Prudhoe Bay

Abstract A total of 29 two-phase flow tests was conducted in two 3-mile-long flow lines in the Prudhoe Bay field of Alaska. Of these, 11 were for a l2-in.-diameter line and 18 were for a 16-in. line. Nine of the tests were in slug flow, and 20 were in froth flow. Flow rates, inlet and outlet pressures, and temperatures were measured for each test. Gamma densitometers were used to monitor flow pattern and to determine mixture densities and slug characteristics. It was found that a modified Beggs-Brill1 pressure-loss correlation predicted culled data to within -1.5% on the average compared with +11.4% for a modified Dukler-Eaton2,3 correlation. Very little scatter was observed with either method. Analysis of flow-pattern observations showed that none of the slug-flow tests were in the Schmidt4 severe slug region characterized by extremely long slugs. It also was found that the slug/froth (dispersed) flow-pattern boundary existed at a much lower liquid flow rate than predicted by either Mandhane et al.5 or Taitel and Dukler.6 Four of the slug-flow tests in 16-in. lines lasted for a sufficient time to permit statistical analysis of slug-length distributions. Sixteen additional tests on 4- and 7-in.-diameter pipe reported by Brainerd and Hedquist* were analyzed statistically. It was found that slug lengths could be represented by a log-normal distribution. A regression analysis approach was successful for estimating the mean slug length for stabilized flow as a function of superficial mixture velocity and pipe diameter. The extreme percentiles of the slug-length distribution then can be computed using standard probability tables, making possible probability statements about expected maximum slug length. A mechanistic analysis of the slug-flow tests resulted in equations for predicting slug velocities, liquid holdup in both the liquid slug and the gas bubble, and the volumes of liquid that are produced and overrun. These parameters are important for predicting liquid-slug effects on separator performance. Introduction The simultaneous flow of gas and liquid in pipes is encountered frequently in the petroleum industry. production of oil with associated gas has led to numerous attempts to predict pressure loss in tubing and flow lines. An abundance of empirical correlations has been developed for predicting two-phase steady-state pressure losses and liquid holdup. All of these correlations were based on data in small-diameter pipe. The recent increase in exploration and production activity in hostile environments such as the North Slope of Alaska and several offshore areas has resulted in decisions to transport gas and liquid simultaneously in large-diameter flow lines over relatively long distances. Design of large-diameter flow lines has required use of empirical correlations based on small-diameter pipe. In general, pressure-loss predictions from this approach have been acceptable, but prediction of liquid volumes in the pipe has been poor.

Numerical Simulation of a Highly Compressed Saturated Water Flashing Flow

2017 ◽  
Author(s):  
Jong Chull Jo ◽  
Jae Jun Jeong ◽  
Byong Jo Yun ◽  
Frederick J. Moody
Keyword(s):  
High Pressure ◽  
Atmospheric Pressure ◽  
Saturated Vapor ◽  
Fluid Velocity ◽  
Saturated Liquid ◽  
Two Phase ◽  
Pressurized Water ◽  
Saturated Water ◽  
Outflow Boundary Condition ◽  
Inner Diameter

Transient fluid velocity and pressure fields in a pressurized water reactor (PWR) steam generator (SG) secondary side during the blowdown period of a feedwater line break (FWLB) accident were numerically simulated employing the saturated liquid flashing model. This model is based on the assumption that compressed water in the SG is saturated at the beginning and decompresses into the two-phase region where saturated vapor forms, creating a mixture of steam bubbles in liquid by bulk boiling. The numerical calculations were performed for two cases where the outflow boundary condition is different from each other; one is specified as the direct blowdown discharge to atmospheric pressure and the other is specified as the blowdown discharge to an extended calculation domain with atmospheric pressure on its boundary. To effectively simulate the saturated water flashing from the SG following the FWLB accident, the physical SG model was simplified as a vertical once-through SG to which a feedwater pipe is attached. However, the physical geometry of the analysis model was modeled as realistically as possible in terms of the SG tube bundle height, the SG inner diameter and porosity, the inner diameter and length of broken feedwater pipe part, etc. It was considered that the SG shell-side and the attached feedwater pipe were initially filled with high pressure saturated water. The pressure in the steam space was 7.5 MPa. For the calculation of the two-phase flow during high pressure saturated water flashing from the SG through the broken feedwater pipe, the inhomogeneous two-fluid model was used. The present simulation results were discussed through a comparison with the predictions using a simple non-flashing model neglecting the effects of phase change. Based on the comparative discussions, the applicability of each of the non-flashing liquid discharge and saturated liquid flashing discharge models to the confirmatory safety evaluations of new SG designs was examined.

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