Characterization and modelling of air humidification in Fuel Cell System for transport sector

A model for the physical description of water transport through steady-state permeation and dynamic sorption within perfluoro-sulfonic acid (PFSA) membranes has been developed. A broad experimental campaign is conducted on several membranes, belonging to Aquivion class, varying both in thickness and equivalent weight (EW). The experimental data have been used to calibrate and validate water transport model and to find correlations for mass-transfer properties in low-EW PFSA membranes that describe consistently both water vapor permeation and sorption. It has been possible to identify individual contributions to mass transport resistance and to determine the optimal configuration and materials of a full-scale counter-flow membrane humidifier under a set of specific operating conditions.

COMPARATIVE PARAMETRIC ANALYSIS OF GAS FLOW IN THREE DIFFERENT DESIGNS OF IN-LINE SCRUBBER BOTTOM INLET

In this study, gas flow fields were simulated using ANSYS 2020R2, Fluid Flow Fluent computational fluids dynamic (CFD) software based on the continuity, velocity, temperature, energy and k - e turbulence. The overall objective of the study is to compare the velocity maps inside the wet scrubber system for three different In-Line scrubber bottom inlet designs. Also, the behavior of the temperature of the mixture inside the scrubber is studied according to the number of nozzles provided by each system from those proposed for study. The numerical simulation using CFD is an effective method to study the flow characteristics of a counter-flow wet scrubber system and the most efficient wet scrubber model is the one with several. The results show that the residuals have a very good job of converging at minimum flow contours and vectors at the inlet across the scrubbing chamber and outlet shows a distributed flow. The speed of water droplets sprayed by the nozzles during mixing with waste gas in the scrubber chamber is double at model with 52 nozzles compared to the first model, equipped with only 13 nozzles. The velocity of clean gases discharged to the ship’s hull shows increases of over 100% of the values, with the increase of the number of nozzles. Spray nozzles improve mixing between the scrubbing liquid and waste gas, by injecting liquid through nozzles to create a fine droplet spray pattern. In this study it can be seen how the number of nozzles influences the quality of the mixture between the scrubbing liquid and waste gas.

Header Shape Effect on the Inlet Velocity Distribution in Cross-Flow Double-Layered Microchannel Heat Sinks

Counter-flow double-layered microchannel heat sinks are very effective for thermal control of electronic components; however, they require rather complicated headers and flow maldistribution can also play a negative role. The cross-flow configuration allows a much simpler header design and the thermal performance becomes similar to that provided by the counter-flow arrangement if the velocity distribution in the microchannels is not uniform. The aim of this work is to show the possibility of achieving a favorable flow distribution in the microchannels of a cross-flow double-layered heat sink with an adequate header design and the aid of additional elements such as full or partial height baffles made of solid or porous materials. Turbulent RANS numerical simulations of the flow field in headers are carried out with the commercial code ANSYS Fluent. The flow in the microchannel layers is modeled as that in a porous material, whose properties are derived from pressure drop data obtained using an in-house FEM code. It is demonstrated that, with an appropriate baffle selection, inlet headers of cross-flow microchannel heat sinks yield velocity distributions very close to those that would allow optimal hotspot management in electronic devices.

Comparison of the Efficiency of Two Types of Heat Exchangers with Parallel Plates Made of Varied Materials

The paper discusses two mathematical models for the air flow through a plate heat exchanger with parallel plates. The first exhausts the used air and then supplies the fresh air. The second exhausts the used air above the plate and simultaneously supplies fresh air under it (counter-flow exchanger). In both cases, the exhaust air heat is used to heat the supply air. The purpose of the research is to verify which exchanger uses the exhaust air heat more efficiently. The method of the Trefftz function was used to determine approximate solutions of the analysed problems. The results obtained for 1.2 mm thick steel, aluminium, and copper plates and for external winter, summer, and spring–autumn temperatures are discussed. The results indicate that steel is the best material for a plate heat exchanger, and the counter-flow exchanger is more efficient of the two. Thanks to the use of thin steel plates and the reduction of the air exchange time to a few minutes, cheap and efficient counter-flow exchangers can be obtained.