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Modelling and experimental validation of unsteady mass flow distribution from header to parallel tubes in a microchannel evaporator.

Author(s) : LI G., ZHUANG D., DING G., XIAO K., LIU Z.

Type of article: IJR article

Summary

The unsteady refrigerant flow from a header to its connected parallel tubes in a microchannel evaporator, induced by vapor-liquid interface fluctuations within the header, may lead to non-uniform mass flow distribution among the parallel tubes, thereby severely degrading its heat transfer performance. This study aims to develop a predictive model for unsteady header-to-tube mass flow rate model to improve the flow uniformity of parallel evaporator tubes. In the structural description of headers, all types of headers with various baffle installation positions are unified into a combination of three standard blocks. To accurately quantify the impact of vaporliquid interface fluctuation on mass flow rates in parallel tubes, the chaotic fluctuation process at the interface is decomposed into three components: the continuous two-phase flow beneath the interface, the continuous vapor flow above the interface, and the discrete droplet flow caused by bubble bursting at the interface. The continuous phase flow is governed by mass and momentum conservation equations, whereas the discrete droplet flow is formulated by the droplet trajectories and the distance from the droplets to tubes. Model validation is conducted using 1872 groups of measured unsteady mass flow data acquired from a vertical header with 12 parallel tubes under various inlet operating conditions. The validation results reveal that the maximum and mean relative deviations between predicted and experimental results are 19.1% and 10.1%, respectively, demonstrating the acceptable accuracy of the proposed model for practical unsteady flow prediction.

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Pages: 20 p.

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Details

  • Original title: Modelling and experimental validation of unsteady mass flow distribution from header to parallel tubes in a microchannel evaporator.
  • Record ID : 30035312
  • Languages: English
  • Subject: Technology
  • Source: International Journal of Refrigeration - Revue Internationale du Froid - vol. 190
  • Publication date: 2026/10
  • DOI: http://dx.doi.org/https://doi.org/10.1016/j.ijrefrig.2026.107064

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