Flow rate distribution in evaporating parallel pipes—modeling and experimental

Abstract The motivation for the present work is related to the use of parabolic trough solar power technology for direct steam generation (DSG). So far, commercial plants use liquid oil to absorb heat from the collectors, and steam is produced in heat exchangers. A more efficient process of direct steam generation in the collectors is not used due to possible uneven flow rate distribution and other instabilities, related to liquid–vapor flow in parallel pipes. In this work we present an analysis and experimental results for the flow rate distribution of water flowing and evaporating in two parallel pipes with common inlet and outlet manifolds. A new simplified model that yields the pressure drop versus the flow rate in a single pipe is developed. This model is the basis for the calculation of steady-state solutions, stability analysis and transient simulations in two parallel pipes. Multiple steady-state solutions may be obtained depending on the flow rate and the heating power. Linear stability analysis and transient simulation allow to differentiate between the stable steady states and the unstable ones. It is also shown that when few stable state solutions are possible the one that takes place depends on the history of the inlet flow rate. Experimental results compare well with the theoretical solutions.

[1]  Markus Eck,et al.  Direct Steam Generation in Parabolic Troughs: First Results of the DISS Project , 2001 .

[2]  Markus Eck,et al.  The DISS Project: Direct Steam Generation in Parabolic Trough Systems. Operation and Maintenance Experience and Update on Project Status , 2001 .

[3]  Eckhard Lüpfert,et al.  Advances in Parabolic Trough Solar Power Technology , 2002 .

[4]  E. K. May,et al.  Flow instability during direct steam generation in a line-focus solar-collector system , 1982 .

[5]  A. Lentz,et al.  DSG Under Two-Phase and Stratified Flow in a Steel Receiver of a Parabolic Trough Collector , 2002 .

[6]  G. Yadigaroglu,et al.  Two-phase flow instabilities and propagation phenomena , 1978 .

[7]  J. Thome,et al.  Convective Boiling and Condensation , 1972 .

[8]  T. N. Veziroglu,et al.  A multivariable linear investigation of two-phase flow instabilities in parallel boiling channels under high pressure , 1993 .

[9]  M. Eickhoff,et al.  Applied research concerning the direct steam generation in parabolic troughs , 2003 .

[10]  F. J. Moody,et al.  The thermal hydraulics of a boiling water nuclear reactor , 1977 .

[11]  M. Nishimura,et al.  Study on Distribution of Flow Rates and Flow Stabilities in Parallel Long Evaporators , 1971 .

[12]  S. Kakaç,et al.  Fundamentals of Two-Phase Flow Instabilities , 1988 .

[13]  R. Knapp.  An Introduction to Fundamentals , 2002 .

[14]  Alvaro Lentz,et al.  Electricity production at low powers by direct steam generation with parabolic troughs , 1998 .

[15]  S. Kakac,et al.  Advances in two-phase flow and heat transfer fundamentals and applications volumes I and II , 1983 .

[16]  P. B. Whalley,et al.  Thermohydraulics of two-phase systems for industrial design and nuclear engineering , 1981 .

[17]  Masud Behnia,et al.  Hydrodynamic Analysis of Direct Steam Generation Solar Collectors , 2000 .

[18]  Yehuda Taitel,et al.  Direct steam generation in parallel pipes , 2003 .

[19]  S. Kakaç,et al.  Transient boiling flow instabilities in a multi-channel upflow system , 1977 .

[20]  K. Fukuda,et al.  TWO-PHASE FLOW INSTABILITY IN PARALLEL CHANNELS , 1978 .

[21]  T. N. Veziroglu,et al.  A Review of Two-Phase Flow Instabilities , 1983 .

[22]  M. Aritomi,et al.  Instabilities in Parallel Channel of Forced-Convection Boiling Upflow System, (III): System with Different Flow Conditions between Two Channels , 1979 .

[23]  A. E. Bergles,et al.  Two-phase flow heat exchangers : thermal-hydraulic fundamentals and design , 1988 .

[24]  R. Lockhart.  Proposed Correlation of Data for Isothermal Two-Phase, Two-Component Flow in Pipes , 1949 .

[25]  Yehuda Taitel,et al.  Evaporation in parallel pipes––splitting characteristics ☆ , 2004 .

[26]  E. K. May,et al.  Performance Benefits of the Direct Generation of Steam in Line-Focus Solar Collectors , 1983 .

[27]  D. Chisholm.  A theoretical basis for the Lockhart-Martinelli correlation for two-phase flow , 1967 .

[28]  P. Richardson,et al.  Boiling heat transfer and two-phase flow , 1956 .