AN EVALUATION OF CONSTITUENT CORRELATIONS FOR PREDICTING REFRIGERANT CHARACTERISTICS IN ADIABATIC CAPILLARY TUBES

DEBASISH SARKER,LYUN-SU KIM,KI-DONG SON,정지환,장근선 대한설비공학회 2010 International Journal Of Air-Conditioning and Refr Vol.18 No.2

Capillary tubes are widely used as a refrigerant flow control device in small refrigeration systems. Since the flow behavior inside the capillary tube is complex, many physical models are necessary to predict the characteristics of the refrigerant flow in a capillary tube. In the present paper, refrigerant flow characteristics inside the capillary tube have been studied to find out recommended empirical correlations of influential parameters. A numerical capillary model is developed to predict the refrigerant characteristics. Various empirical correlations regarding single-phase friction factor, two-phase viscosity, two-phase frictional multiplier and metastable flow are examined using this numerical capillary model. Calculated results are compared with experimental data to examine the accuracy in terms of required capillary tube length and mass flow rate. Based on the comparison, recommended correlations are selected to be used for capillary flow analysis.

Performance of heated pin fin arrangement in a rectangular cavity-An experimental approach

Debasish Das,Ankur Dwivedi,Satya Prakash Verma 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.4

For the last few decades there has been very remarkable growth in electronics and computing technologies and it is still continuing unceasingly. The performance of various engineering devices is limited by thermal management problems. The present investigation deals with heat transfer augmentation through pin fins in gamma of an air-filled rectangular cavity as function of corresponding pertinent factors- fin height, fin spacing as well as Rayleigh number and suggests a direction of future advancements. The experiments are carried out for wide domains of numerous persuading parameters- fin height (12.5 mm ≤ L ≤ 37.5 mm), fin spacing (25 mm ≤ S ≤ 100 mm) and Rayleigh number (360000 ≤ Ra ≤ 680000). Fin spacing is determined as most critical parameter affecting system performance.

The consolidation of deep tube well technology in safe drinking water provision: the case of arsenic mitigation in rural Bangladesh

Debasish Kumar Kundu,Bas J.M. van Vliet,Aarti Gupta 기술경영경제학회 2016 ASIAN JOURNAL OF TECHNOLOGY INNOVATION Vol.24 No.2

This paper explains why and how deep tube well as a safe drinking water technology hasbecome dominant in mitigating the arsenic crisis in rural Bangladesh. We do so by applyinginsights from the Multi-Level Perspective on transitions in explaining changes in the safesocio-technical drinking water regime in rural Bangladesh. Data about seven dimensions ofregime change were gathered from key actors through in-depth interviews, focus groupssessions, a survey, and a workshop. The findings reveal that with the introduction of deeptube well as an arsenic mitigation technology, the observed changes in the seven dimensionshelp to transform the existing safe drinking water regime in order to re-stabilise it. Technological attributes, symbolic meaning, industry structures, and techno-scientificknowledge have supported an evolving dominance of the deep tube well. Besides, userpractices as well as related infrastructures have adapted to the use of deep tube wells, andnew policies stimulated its application. We argue that the dimensions of the technologychange in the existing regime are consistent with the features of incremental innovation. Byoffering such insights, we show the relevance of the Multi-Level Perspective on transitionsto analyse socio-technical innovation in a developing world context.

Effect of internal angles between limbs of cross plan shaped tall building under wind load

Debasish Kumar,Sujit Kumar Dalui 한국풍공학회 2017 Wind and Structures, An International Journal (WAS Vol.24 No.2

The present study revealed comparison the pressure distribution on the surfaces of regular cross plan shaped building with angular cross plan shaped building which is being transformed from basic cross plan shaped building through the variation of internal angles between limbs by 15 for various wind incidence angle from 0 to 180 at an interval of 30. In order to maintain the area same the limbs sizes are slightly increased accordingly. Numerical analysis has been carried out to generate similar nature of flow condition as per IS: 875 (Part –III):1987 (a mean wind velocity of 10 m/s) by using computational fluid dynamics (CFD) with help of ANSYS CFX (k-e model). The variation of mean pressure coefficients, pressure distribution over the surface, flow pattern and force coefficient are evaluated for each cases and represented graphically to understand extent of nonconformities due to such angular modifications in plan. Finally regular cross shaped building results are compared with wind tunnel results obtained from similar \'+\' shaped building study with similar flow condition. Reduction in along wind force coefficients for angular crossed shaped building, observed for various skew angles leads to develop lesser along wind force on building compared to regular crossed shaped building and square plan shaped building. Interference effect within the internal faces are observed in particular faces of building for both cases, considerably. Significant deviation is noticed in wind induced responses for angular cross building compared to regular cross shaped building for different direction wind flow.

GLOBAL FINANCIAL CRISIS AND FOREIGN DEVELOPMENT ASSISTANCE SHOCKS IN LEAST DEVELOPING COUNTRIES

DEBASISH KUMAR DAS,CHAMPA BATI DUTTA 중앙대학교 경제연구소 2013 Journal of Economic Development Vol.38 No.2

This paper evaluates whether the exogenous component of the global financial crisis affects OECD-DAC EU donor countries ODA disbursements to the LDCs and how it impacts on LDCs economic prosperity. Using both static and dynamic panel techniques, we find that global financial crisis in OECD-EU donor countries are causes for the significant downside of ODA flows to the LDCs. Consequently it adversely affects through the various transmission channels (e.g., ODA disbursements, remittances, bilateral financial flows, export growth) to the LDCs economic growth. Our results also explore that due to countercyclical role of ODA flows from the donors’ largely affect to the LDCs economic development process negatively. The robustness checks using alternative estimation technique supports our original estimation results in every context.

Enhanced lipid content in Chlorella sp. FC2 IITG via high energy irradiation mutagenesis

Debasish Das,Baskar Selvaraj,Basavaraj Palabhanvi,Vikram Kumar,Muthusivaramapandian Muthuraj 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.1

High energy ultra-violet radiation was used to induce mutations in the wild type strain Chlorella sp. FC2 IITG and the mutants obtained were screened for enhanced lipid content targeted towards biodiesel production. Screening of mutants under nitrogen starved photoautotrophic condition showed five mutant strains with higher lipid content as compared to the wild type strain. Maximum neutral lipid content of 22.26% (w/w, DCW) was found for FC2-25UV mutant strain, which was 48.4% higher than that of wild type culture. Further characterization under photoautotrophic two stage high cell density cultivation of lipid rich FC2-25UV resulted in total lipid content of 68% (w/w, DCW), which was 21.43% higher than the wild type strain with a marginal improvement of 11% in the total lipid productivity. Comparison of enzyme activity assays under nitrogen starved conditions in both the strains revealed an 18.2% and 31.25% increase in acetyl CoA carboxylase and di-acyl-glycerol transferase activity of mutant. The FAME composition analysis showed 41.5% and 24% increase in the fractions of C18:2 and C18:1 in the mutant strain when compared to the wild type strain with no significant difference in the other FAME fractions. Thus, the mutant strain could be a potential candidate for biodiesel production.

Ceramic - Polymer Nanocomposite: Alternate Choice of Bone

Debasish Sarkar,Min Cheol Chu,Seong Jai Cho 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.6

This study evaluates a range of materials that may be used to design prostheses for bone. It is found that nanocrystallineceramic-polymer composite could be the best material for prosthetic bone with respect to biocompatibility, morphology, chemis-try, and compatibility with the piezoelectric and mechanical behavior of long human bones, such as the femur.

Context Aware Communication in Ubiquitous Computing Environment

Debasish Chakraborty,Hideyuki Takahashi,Takuo Suganuma,Norio Shiratori 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7

Healthcare is increasingly becoming a distributed service involving stakeholders and resources who may be physically far from each other. But privacy and security are potential problems. Patient’s data should be available irrespective of their location, but only to authorized person. Not only that, the relationship between the person under observation and other related people, are different and the security and other characteristics concerning the data may also differ accordingly. In this paper we propose a system where an overlay network can be built in an ad hoc basis and links between different entities will be established according to the social relationship between the object person and the person at the other end and the situation of the observed person. Unlike traditional 24-hrs monitoring system, we argued that an ondemand, requirement oriented system will be beneficial for efficient resource utilization, specially in wireless communication.

Aerodynamic modifications for reduction of wind loads on cross plan shaped tall building

Debasish Kumar,Sujit Kumar Dalui 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.33 No.2

Corner modification plays an essential role in the reduction of the wind load and responses on tall buildings. The present study investigates the effectiveness of different corner modifications (chamfered, rounded, and recessed corners) to reduce the wind load on regular cross plan shaped tall buildings using the computation fluid dynamics technique. Here, ANSYS CFX is used to simulate the boundary layer wind environment around the building and compared with experimental results. The numerically simulated data are compared with some previous wind tunnel test data on the ‘+’ plan building. Based on the numerical study, flow pattern near the corner regions, pressure contour, the variation of pressure coefficient along the periphery of the building, force and moment coefficients for three corner modified models are analyzed and compared with sharp edged cross plan shaped model to comprehend the extent of nonconformities due to corner modifications. The rounded corner modification is most effective in suppressing the wind load compared to chamfered and recessed corners. For rounded corners with 50% corner cut, the reduction in force and moment coefficients is substantial, with up to 26.26% and 28.58%, respectively, compared to sharp edged corners. A sudden shoot up in the negative Cp values near edges of the corner modified model, should require special attention in the design of cladding components. This paper led to comprehend the wind-induced responses of cross plan shaped building with various corner configurations.

Level of Service for On-street Parking

Debasish Das,Mokaddes Ali Ahmed 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.1

Parking of vehicle is one of the most important issues of the urban transportation system in any Central Business District (CBD). A sharp rise in vehicular ownership and insufficient transit system give rise to the huge on-street parking demand leading to a reduction in effective carriageway width, flow speed, creating unnecessary congestion, etc. The problems can be controlled by providing an efficient parking system. The present study aims to estimate the Level of Service (LOS) of on-street parking. LOS is calculated based on three parking selection criteria, viz. Parking Characteristic (PC), Safety Characteristic (SC) and Design Characteristic (DC). Four CBDs of Kolkata Metropolitan Area (KMA) are selected as a case study area. The overall LOS equation is formulated by Analytic Hierarchy Process (AHP). Cluster analysis and Zero dimension process are used to standardize the variables to designated LOS. Various surveys are carried out for data collection. The data are analyzed using SPSS. Finally, the overall LOS for on-street parking is estimated for all the selected CBDs.