School of Mechanical Engineering Seminar
Wednesday, November 14, 2022 at 14:00
Wolfson Building of Mechanical Engineering, Room 206

Stability and transient phenomena of evaporating flow in parallel pipes

 By Ron Rene Hayat

Ph.D. student of Prof. Dvora Barnea, Prof. Yehuda Taitel

Evaporating flow in parallel pipes with common inlet and outlet manifolds is a frequent occurrence in power plants and cooling systems. Parallel pipes systems enhance considerably heat transfer by increasing the total surface area in heat exchangers. However, this process may encounter non-uniform flow rate distribution among the pipes as a result of two phase flow (liquid-vapor) instability causing degradation in the thermal performance of the system. The issue of evaporating flow in parallel pipes is quite broad. It includes various systems depending on the dimensions of the pipes, their orientation (upwards, downwards, inclined), boundary conditions and the way they are integrated into the specific power plant or cooling facilities. The present study aims to shed light on flow rate distribution, stability phenomena and transient behavior of three systems of evaporating flow that have not been fully explored so far.

For each system, phenomenological models based on the main physical mechanisms are presented. These models are capable of predicting the steady state solutions (stable or unstable) and the time dependent behavior of the systems. New experimental results for the steady state flow rate distributions and the transient response of the system to changes in the operational conditions were obtained and compared to the calculations of the models. The main advantage of these models is their ability to predict the system behavior for various flow rates, heating power and physical properties.

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