A comprehensive proton exchange membrane fuel cell system model integrating various auxiliary subsystems

© 2019 Elsevier Ltd A comprehensive proton exchange membrane fuel cell (PEMFC) system model is developed, including a pseudo two-dimensional transient multiphase stack model, a one-dimensional transient multiphase membrane humidifier model, a one-dimensional electrochemical hydrogen pump model, an air compressor model with proportion-integral-derivative control and a ribbon-tubular fin radiator model. All sub-models have been rigorously validated against experimental data to guarantee the system model accuracy. The effects of stack operating temperature, gas flow pattern and humidifier structural design are investigated to cast insights into the interaction among stack and auxiliary subsystems. The results indicate that the stack is successfully maintained at required operating temperatures (60 °C, 70 °C, 80 °C) with help of the radiator when the whole system starts from ambient temperature (25 °C). However, the stack is likely to suffer from membrane dehydration when operated at 70 °C, and the problem becomes more severe at 80 °C, causing significant performance deterioration. The water and temperature distribution inside the system are further demonstrated. The co-current flow pattern contributes to better water utilization of the whole system which may lead to higher output performances. But the counter-current flow pattern has positive effects on parameter distribution uniformity inside fuel cell, which is beneficial for the stack durability. As regards the membrane dehydration, it is found that optimizing membrane humidifier area does not fundamentally solve the problem. Increasing humidifier area contributes to higher water vapor transfer rate, however, it results in much slower humidification responses

Comparison of T lymphocytes and activated T lymphocytes 7 days after surgery in all the experimental groups (single-factor ANOVA).

<p>ANOVA showed significant differences within groups (P<0.01). For pairwise comparison between each group, the Bonferroni method was used, Values represent mean (SD). <b>a:</b> FXN group compared with NC group (P<0.01), AG group (P<0.01), and CEXN group (P<0.01). <b>b:</b> FXN group compared with NC group (P<0.01), FXN group (P<0.01), and CEXN group (P<0.01). <b>c:</b> FXN group compared with AG group (P<0.05).</p

Comparison of intracellular cytokine expression in all experimental groups 7 days after surgery (single-factor ANOVA).

<p>ANOVA showed significant differences within groups (P<0.01). For pairwise comparison between each group, the Bonferroni method was used, Values represent mean (SD). <b>a:</b> FXN group compared with NC group (P<0.01), AG group (P<0.01), and CEXN group (P<0.01).</p

Counts of cells expressing IL-2 14 days after surgery; (A) CEXN group (B) FXN group.

<p>Counts of cells expressing IL-2 14 days after surgery; (A) CEXN group (B) FXN group.</p

Counts of cells expressing IFN-ã 14 days after surgery; (A) CEXN group (B) FXN group.

<p>Counts of cells expressing IFN-ã 14 days after surgery; (A) CEXN group (B) FXN group.</p

Counts of CD25+ T lymphocytes 14 days after surgery; (A) CEXN group (B) FXN group.

<p>Counts of CD25+ T lymphocytes 14 days after surgery; (A) CEXN group (B) FXN group.</p

Comparison of T lymphocytes and activated T lymphocytes 3 days after surgery in all the experimental groups (single-factor ANOVA).

<p>NC, negative control group; AG, fresh autograft group; FXN, fresh xenogeneic nerve group; CEXN, chemically extracted acellular xenogeneic nerve group. ANOVA showed no significant differences between each group. Values represent mean (SD).</p

Comparison of T lymphocytes and activated T lymphocytes 14 days after surgery in all the experimental groups (single-factor ANOVA).

<p>ANOVA showed significant differences within groups (P<0.01). For pairwise comparison between each group, the Bonferroni method was used, Values represent mean (SD). <b>a:</b> FXN group compared with NC group (P<0.01), AG group (P<0.01), and CEXN group (P<0.01).</p

Nerves were harvested and processed for each group.

<p>(<b>A</b>) The skin incision was closed after ulner nerves were bilaterally harvested from the rabbits for further use in the chemically extracted acellular xenogeneic nerve group (CEXN group); (<b>B</b>) Sciatic nerves were harvested from BALB/c mice for immediate use in the fresh autograft group (AG group); (<b>C</b>) Fresh xenogeneic ulner nerves (0.3 mm in diameter and 12 mm long ) were harvested from New Zealand rabbits for immediate use in fresh xenogeneic nerve group (FXN group); (<b>D</b>) Xenogeneic ulner nerves (0.3 mm in diameter and 12 mm long ) were treated by chemical extraction for further use in the CEXN group.</p

Comparison of intracellular cytokine expression in all experimental groups 28 days after surgery (single-factor ANOVA).

<p>ANOVA showed significant differences within groups (P<0.01). For pairwise comparison between each group, the Bonferroni method was used, Values represent mean (SD). <b>a:</b> FXN group compared with NC group (P<0.01), AG group (P<0.01), and CEXN group (P<0.01).</p