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Mulyazmi,National University of Malaysia | Mulyazmi,Bung Hatta University | Daud W.R.W.,National University of Malaysia | Majlan E.H.,National University of Malaysia | Rosli M.I.,National University of Malaysia
International Journal of Hydrogen Energy | Year: 2013

The design of a proton exchange membrane (PEM) fuel cell system is important for the optimization of the function of supporting parameters in the fuel cell. The water balance in a PEM fuel cell is investigated based on the water transport phenomena. In this investigation, the diffusion of water from the cathode side to the anode side of the cell is observed to not occur at 20% relative humidity at the cathode (RHC) and 58% relative humidity at the anode (RHA). The minimum concentration of condensed water at the cathode side is observed at a cathode gas inlet relative humidity of 40% RHC-92% RHC and at temperatures between 343 K and 363 K. RHC operating conditions that are greater than 90% and at a temperature of 363 K increased the concentration of condensed water and occurred quickly, which result in a water balance that became difficult to control. On the anode side, the condensation of water is observed at operating temperatures of 353 K and 363 K. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Sulaimon S.,University of Technology Malaysia | Aziz A.A.,University Of Maiduguri | Nasution H.,Bung Hatta University
Applied Mechanics and Materials | Year: 2013

According to Montreal Protocol, HCFC22 (hydro chlorofluorocarbon), a commonly used refrigerant in domestic refrigeration and air-conditioner, must be phased out owing to its environmental problem. Several natural substances including ammonia, carbon dioxide, water and hydrocarbon (HC) such as propane (HC290) and butane (HC600) and their mixtures have immerged as close substitute. Literature showed that pure HC refrigerant may not be suitable enough because of the difference in operating pressure and volumetric cooling capacity when compared with HCFC22. The main objective of this study is to theoretically investigate different ratios of HC refrigerants HC290/HC600 mixtures flowing through adiabatic capillary tube using homogenous model. In this study, the percentage by volume of HC290 was varied from 30 to 40 % in a step of 5%. The pressure at the two extreme ends and temperature along the capillary tube, using HCFC22 refrigerant, which was used as benchmark, was experimentally determined in the air-conditioning (AC) system. Comparing the model results with the experimental data showed that HC refrigerants HC290/HC600 in ratio 35%/65% gave 2.95% minimum error and thus it can be used as a substitute to HCFC22 in the split-type AC system. © (2013) Trans Tech Publications, Switzerland.

Suherman H.,National University of Malaysia | Suherman H.,Bung Hatta University | Sulong A.B.,National University of Malaysia | Sahari J.,National University of Malaysia
Ceramics International | Year: 2013

The main challenges for commercialization of a single-filler graphite (G) polymer-matrix composite as bipolar plates are its low electrical conductivity and flexural strength. The minimum requirements set by the US Department of Energy (DOE) are the electrical conductivity and flexural strength to be greater than 100 S/cm and 25 MPa, respectively. In this study, the electrical conductivity of a G/epoxy (EP) composite (single filler) is only 50 S/cm (in-plane conductivity) at 80 wt% G. However, flexural strength is greater than 25 MPa. Using carbon nanotubes (CNTs) as the second filler at a concentration of 5 wt% in a CNTs/G/EP nanocomposite resulted in the in-plane and through-plane electrical conductivity and flexural strength being 180 S/cm, 75 S/cm, and 45 MPa, respectively. The density of the CNTs/G/EP nanocomposite is also less than that of G/EP composite, which demonstrates that a total weight reduction is achievable. © 2012 Elsevier Ltd and Techna Group S.r.l.

Suherman H.,National University of Malaysia | Suherman H.,Bung Hatta University | Sahari J.,National University of Malaysia | Sulong A.B.,National University of Malaysia
Ceramics International | Year: 2013

This paper focused on using a conductive polymer composite (CPC) as a potential replacement for the conventional graphite bipolar plate used in polymer electrolyte membrane fuel cells (PEMFC). Based on the requirements established by the US Department of Energy (DOE), the in-plane electrical conductivity and flexural strength are required to be greater than 100 S/cm and 25 MPa, respectively. The high filler loading is needed to satisfy the high in-plane electrical conductivity. However, the high filler loading reduces the flexural strength and manufacturability of the composite. In this study, the composites were prepared by compounding using an internal mixer followed by compression moulding. The combination of 10 vol% carbon black (CB) as the second filler with synthetic graphite/epoxy (SG/EP) resulted in the following composite properties: 150 S/cm (in-plane conductivity), 55 S/cm (through-plane conductivity), and 38.8 MPa (flexural strength). Used as the second filler, the CB, which had a small-sized diameter, formed conductive networks that filled the voids between the SG and polymer matrix. The in-plane electrical conductivity and flexural strength of the CB/SG/EP composites at the optimum composition exceeded the requirement for bipolar plate applications. © 2013 Elsevier Ltd and Techna Group S.r.l.

Desmiarti R.,Bung Hatta University | Li F.-S.,Gifu University
ITB Journal of Engineering Science | Year: 2011

The sorption and the degradation capacity of natural estrogens in freshwater environmental system in Japan were performed. Batch experiments were examined in water-sediment suspensions using six layers of sediment under aerobic and anaerobic conditions. The results indicated that the water-sediment partition coefficient of E1 (K d E1) was higher than E2 (K d E2). The degradation rate of E1 (k E1) was smaller than E2 (k E2). Under aerobic and anaerobic conditions, E1 was formed from E2. The degradation rate of E2 (k E2) from the surface to bottom of sediment layers was estimated fell in the range from 0.114 to 0.026 h -1 and 0.05 to 0.014 h -1 under aerobic and anaerobic conditions, respectively.

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