Novel Test Facility for Investigation of Two-Phase Heat Transfer in Bipolar-Shaped Channels Within Mobile PEM Fuel Cell Applications

This paper deals with the design and description of a test rig for investigating 2-phase flows of alternative refrigerants such as methanol and ethanol in near-operational conditions in low-temperature polymer electrolyte membrane fuel cells (LT-PEMFC). The objective of the work is to investigate the two-phase cooling of different refrigerants in LT-PEMFCs and to establish heat transfer and pressure drop correlations under realistic boundary conditions. The parameter range for the investigation includes a mass flux 5 <= G <= 45 kg/m(2)s, a heat flux of 0 <= (q) over dot <= 1.5W/m(2) and a vapor mass fraction of 0 <= x <= 1. The object of investigation is a single-channel system with a channel length of about 390 mm. Various channel cross sections are considered including rectangular cross sections with hydraulic diameters dh of 0.3 - 1.0 mm as well as approximated fuel cell channel geometries with hexagonal cross-sections and hydraulic diameters dh of 0.64 mm. Due to the modular structure of the test section it is possible to investigate different channel cross sections. In perspective also parallel channels can be investigated. A unique feature of the test setup is the use of a special glass that allows both the observation of the flow pattern and the discrete thermographic temperature resolution of the fluid in all phases. By performing the investigation at different steady-state operating points and setting dynamic operating characteristics, the operation of an LT-PEMFC can be simulated for mobile applications and thus forms a fundamental scientific contribution to the thermodynamic behavior of a two-phase cooled LT-PEMFC as well as an extended understanding of thermal management especially with respect to FC systems with electric power outputs > 100 kW.