Transient solution for flow of evaporating fluid in parallel pipes using analysis based on flow patterns

Taitel, Yehuda; Barnea, Dvora

doi:10.1016/j.ijmultiphaseflow.2011.01.002

Cited by 29 publications

(9 citation statements)

References 19 publications

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“…In general, the fraction of flow to the heated channels in which boiling occurred was reduced below average. A similar study was performed [32] on two parallel channels using a model like in Ref.…”

Section: Literature Reviewmentioning

confidence: 99%

Predicting two-phase flow distribution and stability in systems with many parallel heated channels

Oevelen

Weibel

Garimella

2017

International Journal of Heat and Mass Transfer

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Two-phase heat exchangers are used in a variety of industrial processes in which the boiling fluid flows through a network of parallel channels. In some situations, the fluid may not be uniformly distributed through all the channels, causing a degradation in the thermal performance of the system. A methodology for modeling two-phase flow distributions in parallel-channel systems is developed. The methodology combines a pressure-drop model for individual parallel channels with a pump curve into a system flow network. Due to the non-monotonicity of the pressure drop as a function of flow rate for boiling channels, many steady-state solutions exist for the system flow equations. A new numerical approach is proposed to analyze the stability of these solutions, based on a generalized eigenvalue problem. The method is specifically designed for analyzing systems with hundreds of identical parallel channels.The method is first applied to analyze the flow distribution and stability behavior in two-channel and five-channel systems. The asymptotic behavior of the flow stability is then analyzed for increasing numbers of channels, and it is shown that the stability behavior of a system with a constant flow-rate pump curve simplifies to the stability behavior for a constant pressure-drop pump curve. A parametric study is conducted to assess the influence of inlet temperature, heat flux, and flow rate on the stability of the uniform flow distribution solution as well as on the severity of flow maldistribution. Below some critical inlet subcooling, uniform flow distribution is always stable and maldistribution does not occur, regardless of heat flux and flow rate. Above this critical inlet subcooling, there is a range of operating parameters for which uniform flow distribution is unstable. With increasing inlet subcooling, this range broadens and the severity of the associated maldistribution increases.

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Section: Literature Reviewmentioning

confidence: 99%

Predicting two-phase flow distribution and stability in systems with many parallel heated channels

Oevelen

Weibel

Garimella

2017

International Journal of Heat and Mass Transfer

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“…Various studies have used the theoretical foundations from Ref. [29] to model flow maldistribution in two-phase systems [30][31][32][33][34]. Their approaches combine semi-empirical channel models with system-level network equations to obtain the cumulative load curve and flow rate distributions as a function of total flow rate.…”

Section: Introductionmentioning

confidence: 99%

The effect of lateral thermal coupling between parallel microchannels on two-phase flow distribution

Oevelen

Weibel

Garimella

2018

International Journal of Heat and Mass Transfer

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Evaporating flows in parallel channels occurring in a variety of industrial heat exchange processes can encounter nonuniform flow distribution between channels as a result of two-phase flow instabilities.Such flow maldistribution can have a negative impact on the performance, robustness and predictability of these systems. Two-phase flow modeling can assist in understanding the mechanistic behavior of this flow maldistribution, as well as determine parametric trends and identify safe operating conditions. The work described in this paper expands on prior two-phase flow distribution modeling efforts by including and assessing the effect of thermal conduction in the walls surrounding the parallel channels.This thermal conduction has a critical dampening effect on wall temperature gradients. In particular when a channel is significantly starved of flow rate and risks dryout, channel-to-channel thermal coupling can redistribute the heat load from the flow-starved channel to neighboring channels. The model is used to simulate the two-phase flow distribution in a system of two parallel channels driven by a constant flow rate pump. A comparison between thermally isolated and coupled channels indicates that thermally coupled channels are significantly less susceptible to maldistribution. Furthermore, a parametric study reveals that flow maldistribution is only possible in thermally coupled systems beyond a certain critical heat flux threshold. This threshold heat flux increases as the lateral wall conductance is increased, converging to a constant value in the limit of very high lateral conductance.

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“…Zhang et al (2011) presented a stability analysis and active flow and temperature control of a parallel channel evaporator. Taitel and Barnea (2011) presented a transient model for flow rate distribution in evaporating two * Corresponding author.…”

Section: Introductionmentioning

confidence: 99%

Transient data for flow of evaporating fluid in parallel mini pipes and comparison with theoretical simulations

Barnea

Simkhis

Taitel

2015

International Journal of Multiphase Flow

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Transient solution for flow of evaporating fluid in parallel pipes using analysis based on flow patterns

Cited by 29 publications

References 19 publications

Predicting two-phase flow distribution and stability in systems with many parallel heated channels

Predicting two-phase flow distribution and stability in systems with many parallel heated channels

The effect of lateral thermal coupling between parallel microchannels on two-phase flow distribution

Transient data for flow of evaporating fluid in parallel mini pipes and comparison with theoretical simulations

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