Numerical Simulation on the Organic Fluid Two-Phase Flow and Heat Transfer in the PEMFC Cooling Plate for Waste Heat Recovery

The proton exchange membrane fuel cell (PEMFC) system is becoming one of the most potential power systems for automotive applications in the future. Though the efficiency of PEMFC is high, almost half of the hydrogen energy is taken away by coolant without being utilized. Organic Rankine Cycle (ORC) could be used for the waste heat recovery of PEMFC. The working fluid of ORC flows directly into the fuel cell stack and cool the stack as the same time. In this paper, the feasibility of R245ca as the coolant of PEMFC and working fluid of ORC is studied. A simulation model of the fluid flow and heat transfer of R245ca in PEMFC cooling plates is set up with the CFD software package FLUENT. The Volume of Fluid (VOF) model is used to simulate the two-phase flow. Results show that R245ca can efficiently remove the waste heat and ensure uniform temperature distribution in PEMFC.

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Modeling and Validation of a Two-Phase Flow Valve for Expanders in Waste Heat Recovery

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4048675 ◽

2020 ◽

Vol 13 (3) ◽

Author(s):

Fabian Schweizer ◽

Marius Fürst ◽

Georg Wachtmeister

Keyword(s):

Heat Recovery ◽

Waste Heat Recovery ◽

Two Phase Flow ◽

Waste Heat ◽

Mechanical Energy ◽

Dynamical Behavior ◽

Measurement Data ◽

Working Fluid ◽

Phase Flow ◽

Two Phase

Abstract Waste heat recovery is a promising method to reduce fuel consumption and CO2 emissions in heavy-duty vehicles. An organic Rankine cycle (ORC) is used to convert the thermal energy of the exhaust gases into useable energy to support the power train. A key component of the ORC is the expansion machine where the conversion of thermal into mechanical energy takes place. In the case of volumetric expansion machines such as axial piston expanders, lubrication oil is mixed in with the working fluid to reduce friction and increase the component durability. However, the presence of oil also affects both the efficiency and the fluid dynamical behavior inside the expander. To implement a one-dimensional simulation model that considers the oil influence, a continuous flow approach is selected. Particular attention is dedicated to the inlet and outlet valve modeling, as these have to account for two-phase flow and multicomponent fluid mixtures. A valve model is built up in the simulation environment dymola based on the homogeneous nonequilibrium (HNE) approach. A virtual one-cylinder test bench is set up to calibrate and validate the model. The simulation results show good correspondence with the measurement data.

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Flow and heat transfer in a closed loop thermosyphon. Part I – theoretical simulation

Journal of Energy in Southern Africa ◽

10.17159/2413-3051/2007/v18i4a3389 ◽

2007 ◽

Vol 18 (4) ◽

pp. 32-40 ◽

Cited By ~ 8

Author(s):

R.T. Dobson ◽

J.C. Ruppersberg

Keyword(s):

Heat Transfer ◽

Heat Pipe ◽

Closed Loop ◽

Two Phase Flow ◽

Working Fluid ◽

Phase Flow ◽

Two Phase ◽

Operating Modes ◽

Flow And Heat Transfer ◽

Control Volumes

A natural circulation, closed loop thermosyphon can transfer heat over relatively large distances without any moving parts such as pumps and active controls. Such loops are thus considered suitable for nuclear reactor cooling applications where safety and high reliability are of paramount importance. A theoretical basis from which to predict the flow and heat transfer performance of such a loop is present-ed. A literature survey of the background theory is undertaken and the theoretical equations describing the single and two-phase flow as well as heat trans-fer behaviour are given. The major assumptions made in deriving these equations are that the work-ing fluid flow is quasi-static and that its single, two-phase flow and heat transfer behaviour may be cap-tured by dividing the working fluid in the loop into a number of one dimensional control volumes and then applying the equations of change to each of these control volumes. Theoretical simulations are conducted for single phase, single and two-phase and heat pipe operating modes, and a sensitivity analysis of the various variables is undertaken. It is seen that the theoretical results capture the single and two-phase flow operating modes well for a loop that includes an expansion tank, but not for the heat pipe operating mode. It is concluded that the theo-retical model may be used to study transient and dynamic non-linear effects for single and two-phase modes of operation. To more accurately predict the heat transfer rate of the loop however, loop specific heat transfer coefficients need to be determined experimentally and incorporated into the theoretical model.

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Two-Phase Flow and Heat Transfer in Pin-Fin Enhanced Micro-Gaps With Non-Uniform Heating

ASME 2013 4th International Conference on Micro/Nanoscale Heat and Mass Transfer ◽

10.1115/mnhmt2013-22124 ◽

2013 ◽

Cited By ~ 5

Author(s):

Steven A. Isaacs ◽

Yogendra Joshi ◽

Yue Zhang ◽

Muhannad S. Bakir ◽

Yoon Jo Kim

Keyword(s):

Heat Transfer ◽

Two Phase Flow ◽

Flow Boiling ◽

Heat Fluxes ◽

Working Fluid ◽

Phase Flow ◽

Two Phase ◽

Pin Fin ◽

Flow And Heat Transfer ◽

Imaging Results

In modern microprocessors, thermal management has become one of the main hurdles in continued performance enhancement. Cooling schemes utilizing single phase microfluidics have been investigated extensively for enhanced heat dissipation from microprocessors. However, two-phase fluidic cooling devices are becoming a promising approach, and are less understood. This study aims to examine two-phase flow and heat transfer within a pin-fin enhanced micro-gap. The pin-fin array covered an area of 1cm × 1cm and had a pin diameter, height and pitch of 150μm, 200μm and 225μm, respectively, (aspect ratio of 1.33). Heating from two upstream heaters was considered. The working fluid used was R245fa. The average heat transfer coefficient was evaluated for a range of heat fluxes and flow rates. Flow regime visualization was performed using high-speed imaging. Results indicate a sharp transition to convective flow boiling mechanism. Unique, conically-shaped two-phase wakes are recorded, demonstrating 2D spreading capability of the device. Surface roughness features are also discussed.

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