Hydropower to Hydrogen Based Industry Prospects in Nepal

Biraj Singh Thapa,Bhola Thapa,Young-Ho Lee 한국신재생에너지학회 2021 AFORE Vol.2021 No.10

PROSPECTS OF NEW BUSINESS IN HYDROPOWER MARKET WITH INNOVATIVE TECHNOLOGY FOR REDUCING SEDIMENT EROSION IN TURBINES

Biraj Singh Thapa,Bhola Thapa,Ole Gunnar Dahlhaug 한국신재생에너지학회 2012 AFORE Vol.2012 No.-

EXPERIENCES OF R&D OF FRANCIS TURBINE AT KATHMANDU UNIVERSITY

Biraj Singh Thapa,Krishna Prasad Shrestha,Laxman Poudel,Bhola Thapa 한국신재생에너지학회 2011 AFORE Vol.2011 No.-

폴리스티렌-클레이 나노 복합재료의 합성 및 차단 특성에 관한 연구

비라즈둔가나(Biraj Dhungana),손영곤(Son Young-Gon) 한국산학기술학회 2013 한국산학기술학회논문지 Vol.14 No.5

고성능 고분자/클레이 나노 복합재료의 제조 과정에는 친수성을 보이는 클레이 원료 물질인 Na+-MMT (sodium monmorilonite)를 친유성을 갖도록 유기화된 계면활성제로처리하여 개질하는 과정이 필수적이다. 이를 위하여 이 연구에서는 VDAC (vinylbenzyldimethyl-dodecylammonium chloride)를 간단한 화합물로부터 합성하였고 이를 이용 하여 양이온 교환반응에 의하여 Na+-MMT를 개질한 후 VDA+-MMT를 제조하였다. 이를 스티렌과 혼합하여 in-situ 중합에 의하여 나노복합재료를 제조하였고 클레이의 분산성 및 차단특성을 연구하였다. 연구 결과 PS/VDA+-MMT 나 노 복합재료의 경우 클레이의 분산이 Na+-MMT와 비교할 때 현저히 증가함을 확인하였고 이로 인해 유기 용매에 대한 차단 특성이 매우 우수함을 확인하였다. In prepaparation of the high performance polymer/clay nanocomposite, it is essential to modify the hydrophillic Na+-MMT to hydrophobic alkyl ammonium-MMT via organic surfactant. The organic surfactant, VDAC (vinylbenzyldimethyl-dodecylammonium chloride) was synthesized from two primary chemicals and VDA+-MMT was prepared from Na+-MMT through a cation exchange reaction between Na+ and VDA+ (vinylbenzyldimethyl-dodecylammonium+) cation. VDA+-MMT was then dispersed in styrene and polystyrene/ VDA+-MMT nanocomposite was fabricated by in-situ polymerization reaction. The clay dispersion and barrier property of the nanocomposite were investigated. From the investigations, it was confirmed that dispersion of the VDA+-MMT was enhanced compared with that of Na+-MMT and as a consequency of better dispersion, barrier property of organic solvent was improved in a great extent.

Facile synthesis of 1D-architecture of silver-vanadates in carbon nest for enhanced visible light driven photo-oxidation process

Das, Biraj,Sharma, Mukesh,Deka, Biplab K.,Hazarika, Ankita,Park, Young-Bin,Hazarika, Anil,Bhargava, Suresh K.,Bania, Kusum K. Elsevier 2018 Journal of environmental chemical engineering Vol.6 No.2

<P><B>Abstract</B></P> <P>Ag/AgCl/V<SUB>2</SUB>O<SUB>5</SUB> nanocatalysts with one dimensional (1D) architecture was synthesized in carboxylic acid functionalized multi-walled carbon nanotubes for methylene blue dye degradation. The growth of uniformly distributed nanoparticles along the carbon-nanotubes was revealed from high resolution transmission electron microscopy and atomic force microscopy analyses. Raman spectroscopy and transmission electron microscopy analyses also confirmed for the creation of defects in the multi-walled carbon nanotube. The hybrid nanocomposite appeared as a suitable photocatalyst for degradation of methylene blue dye absorbing the light in the visible range of solar spectrum. The presence of interactions within the nanoparticles and with the nanotubes was believed to enhance the photo-oxidation process. The creation of defects in the carbon nanotube on modification with Ag/AgCl/V<SUB>2</SUB>O<SUB>5</SUB> improved the photocatalytic activity by enhancing the photoelectron transfer process. About ∼90% of the total organic carbon of the dye molecule was found to decompose into CO<SUB>2</SUB>, H<SUB>2</SUB>O and inorganic ions within 25 min under sunlight.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ag/AgCl/V<SUB>2</SUB>O<SUB>5</SUB> with 1D architecture is synthesized in Multiwalled Carbon Nanotube. </LI> <LI> Ag/AgCl/V<SUB>2</SUB>O<SUB>5</SUB>-MWCNT appeared as suitable photocatalyst absorbing visible light of solar spectrum. </LI> <LI> Creation of defects in MWCNT enhanced the photocatalytic ability of the nanomaterial. </LI> <LI> The hybrid nanocomposite decompose methylene blue dye with high efficiency within 25 min under sunlight. </LI> <LI> The photocatalyst was recyclable for three consecutive cycles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P> <P>Complete mineralization of MB dye with Ag/AgCl/V<SUB>2</SUB>O<SUB>5</SUB>-MWCNT nanocomposite under sun light.</P>

연료전지 양극판용 PC/흑연 삽입 화합물 복합재료의 유동성, 물리적 성질 및 전기전도도에 관한 연구

비라즈 둔가나(Biraj Dhungana),손영곤(Younggon Son) 한국고분자학회 2019 폴리머 Vol.43 No.2

고분자 전해질 연료전지의 양극판에 적용될 폴리카보네이트(polycarbonate, PC)/흑연 삽입 화합물 복합재료의 유동성, 물성 및 전기전도도에 관하여 연구하였다. 기존 연구와의 차이점은 팽창된 흑연을 사용하는 대신 bisulfate가 삽입된 흑연 삽입 화합물(graphite intercalated compound, GIC)을 고분자와 압출기에서 혼합하면서 동시에 GIC를 열 팽창시켜 복합재료를 제조한 점이다. 기존의 고분자/팽창 흑연과 비교하여 이 연구에서 처음으로 시도한 고분자/GIC의 장점은 유동성에 있다. GIC가 사출과정에서 팽창에 의해 금형에 밀려들어가는 형태의 유동 패턴을 보이고 이로 인해 더 높은 유동성을 보이는 것으로 관찰되었다. The fluidity, physical properties and electrical conductivity of polycarbonate (PC)/ graphite intercalated compound composites were investigated for the application of bipolar plate of electrolyte fuel cells. The intrinsic difference of this study from the previous studies on the polymer/expanded graphite is that the graphite intercalated compound (GIC) with bisulfate was used instead of expanded graphite. GIC was compounded with the PC in the twin screw extruder and injection molded. During the compounding and molding procedure, GIC was expanded and transformed to expanded graphite. The advantage of the polymer/GIC compared to conventional polymer/expanded graphite lies in its higher fluidity. As a precursor of expanded graphite, GIC is finally converted to expanded graphite during extrusion and injection molding. During the filling stage of injection molding process, the PC/GIC was pushed into the mold cavity by the thermal expansion of GIC, resulting in higher fluidity.

고분자 전해질막 수소 연료 전지 분리판 용 흑연/폴리프로필렌/액정고분자 복합 재료의 특성에 관한 연구

비라즈 둔가나(Dhungana, Biraj),손영곤(Son Young-Gon) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.5

고분자 전해질 막 연료전지의 분리판 용 흑연/폴리프로필렌(PP)/액정고분자 (LCP) 복합소재의 기계적, 유변학 특성 및 전기전도도에 관하여 연구하였다. 저분자량 PP를 바인더로 사용하는 경우 다른 열가소성 고분자와 비교하여 상당히 높은 전기 전도도를 보임을 확인하였는데 이는 점도가 낮은 PP에 의해 흑연 입자의 분산이 향상되어 나타난 결과임을 확인할 수 있었다. 또한 탄소나노튜브를 소량 첨가하면 복합재료의 전기전도도가 크게 증가하였고 산처리를 하여 산소 관능기를 포함한 탄소나노튜브를 첨가했을 때에는 전기전도도의 증가가 거의 없었다. 이로부터 탄소나노튜브는 비극성 고분자와 친화 도가 높음을 알 수 있었다. 저분자량 PP를 바인더로 사용하였을 때는 복합재료의 점도가 사출성형이 가능할 정도로 낮은 것을 관찰할 수 있었다. 그러나 기계적인 강도는 다른 고분자에 비해 현저히 낮았다. 이를 보강하기 위하여 LCP를 혼합하여 복합재료를 제조한 결과 전반적인 물성 밸런스가 잘 맞는 복합재료를 얻을 수 있었다. We investigated mechanical, rheological and electrical properties of graphite/PP/LCP composites for a bipolar plate of the polymer electrolyte membrane fuel cell. The composites containing very low molecular weighted PP showed much higher electrical conductivity compared with other thermoplastics. This was attributed to the enhanced dispersion of graphite particles due to the low viscosity of the PP. The conductivity of the composites was increased in a great extent by incorporation of small amount of carbon nano tube (CNT). However, the acid treated CNT which contains oxygen atoms did not increase the conductivity of the composite. From this result, it is concluded that the CNT has higher affinity with non polar polymer. The composite with low molecular weighted PP provided good processability so that the composites can be processed by an injection molding while the mechanical strength is deficient compared to other polymers. In order to reinforce the low mechanical property, LCP/PP was used as a binder and the graphite/PP/LCP composite showed the higher conductivity and moderate mechanical strength maintaining suitable processability.

CFD AND FSI ANALYSIS OF 92 KW MODEL FRANCIS RUNNERS WITH ALTERNATIVE DESIGN FOR SEDIMENT HANDLING

Atmaram Kayastha,Biraj Singh Thapa,Hari Prasad Neopane,Bhola Thapa,Young Ho LEE 한국신재생에너지학회 2013 AFORE Vol.2013 No.-

Numerical and experimental study of the leakage flow in guide vanes with different hydrofoils

Sailesh Chitrakar,Biraj Singh Thapa,Ole Gunnar Dahlhaug,Hari Prasad Neopane 한국CDE학회 2017 Journal of computational design and engineering Vol.4 No.3

Clearance gaps between guide vanes and cover plates of Francis turbines tend to increase in size due to simultaneous effect of secondary flow and erosion in sediment affected hydropower plants. The pressure difference between the two sides of the guide vane induces leakage flow through the gap. This flow enters into the suction side with high acceleration, disturbing the primary flow and causing more erosion and losses in downstream turbine components. A cascade rig containing a single guide vane passage has been built to study the effect of the clearance gap using pressure sensors and PIV (Particle Image Velocimetry) technique. This study focuses on developing a numerical model of the test rig, validating the results with experiments and investigating the behavior of leakage flow numerically. It was observed from both CFD and experiment that the leakage flow forms a passage vortex, which shifts away from the wall while travelling downstream. The streamlines contributing to the formation of this vortex have been discussed. Furthermore, the reference guide vane with symmetrical hydrofoil has been compared with four cambered profiles, in terms of the guide vane loading and the consequent effect on the leakage flow. A dimensionless term called Leakage Flow Factor (Lff) has been introduced to compare the performances of hydrofoils. It is shown that the leakage flow and its effect on increasing losses and erosion can be minimized by changing the pressure distribution over the guide vane.

FUEL CELL RECOVERY AFTER EXPOSURE TO POISONS

Anthony Kucerna,Biraj Kakati 한국신재생에너지학회 2015 AFORE Vol.2015 No.11