CFD Heat and Mass Transfer Studies in a R134a-DMF Bubble Absorber with Swirl Flow Entry of R134a Vapour

Study of absorber for heat and mass transfer analysis is essential to improve the performance of Vapour absorption refrigeration system(VARS). Tangential injection of refrigerant gas to liquid solution  in a bubble absorber increase the heat and mass transfer characteristics by following rotary and translation path. In this study, a vertical absorber is considered for heat and mass transfer study with refrigerant, R134a (1,1,1,2 –Tetrafluoroethane) and absorbent, DMF(dimethyl formamide). R134a vapour will be injected into the absorber using two injectors of 4.8 mm inner diameter at an injection angle of 30° to the vertical axis and parallel to the azimuthal axis of the absorber which mix well with liquid to increase the heat and mass transfer.            Finite volume method is used for the steady state with 3D cylindrical co-ordinates. Simulation is carried out for studying the heat and mass transfer behavior in laminar flow, using CFD.  For the numerical study, Mixture multiphase model is considered. A user defined function (UDF) is written for creating liquid solution mixture and refrigerant vapour to define the working fluid and its various properties like density, thermal conductivity, viscosity, etc. Grid  independent studies were carried out for the absorber geometry. Mass inlet boundary condition for solution inlet, and  vapour inlet, pressure outlet at the absorber and no-slip at wall boundary condition are used. In the absorber interface, wall constant heat flux boundary condition is defined. Evaporation and condensation model is used as phase and mass transfer interface mechanism between liquid and vapour. SIMPLER(Semi-Implicit Method for Pressure-Linked Equations) scheme is used for pressure- velocity coupling, PRESTO(Pressure Staggered Option) scheme is used for pressure and first order implicit upwind scheme is used for solving momentum equations. Converging criteria are achieved for momentum, energy and species equation by varying under relaxation factors.        Effect of solution pressure, solution flow rate, gas mass flow rate on heat and mass transfer rate, heat and mass transfer coefficients are computed. Numerical results are compared and validated with the co-axial entry of R134a in the R134a-DMF bubble absorber which show good agreement. Heat and mass transfer characteristic will be presented in this paper in terms of operational parameters

Experimental Study On Bubble Absorber With Multiple Tangential Nozzles

Vapour absorption refrigeration (VAR) system is one of the better system compared to other high grade energy utilized refrigeration system from thermodynamics point of view. For the successful operation of this system, the components are required to be designed and developed effectively and efficiently. Absorber is one of the crucial component of such a refrigeration system and bubble absorber is one type of absorber among different types of absorber. Bubble characteristics are studied experimentally with tangential nozzles, which may enhance the heat and mass transfer characteristics by following a swirling motion. Based on the inference drawn from these studies, experiments are planned with R134a and DMF combination for performance improvement of the VAR system. Visualization study of bubble growth with multiple tangential nozzles is investigated in a bubble absorber. Bubble behavior is studied with different flowing condition like still, co-current and counter-current flow of water. Bubble diameter during detachment increases with increase in gas flow rate in the above flow conditions. Effect of air flow rate, water flow rate, nozzle diameters, number of nozzles and nozzle angle with reference to vertical plane on bubble diameter is also studied. Results are compared with the available correlation in the literature which is found to be in good agreement. Comparison of performance between single and double nozzle also presented in this paper. Based on this study correlations are proposed. References: [1] M. Suresh, A. Mani, Heat and mass transfer studies on R134a bubble absorber in 134a/DMF based on phenomenological theory, International Journal of Heat and Mass Transfer 53 (2010) 2813–2825. [2] S. Ramakrishnan, R. Kumar, R.Kuloor, Studies in bubble formation-I Bubble formation under constant flow conditions, Chemical Engineering Science, 24 (1969) 731-747. [3] M. Jamialahmadi, M. R. Zehtaban , H. Muller-Steinhagen, A. Sarrafi A, J. M. Smith, Study of bubble formation under constant flow conditions, Trans IChemE, 79 (2001) Part A 523. [4] E.S. Gaddis, A. Vogelpohl, Bubble formation in quiescent liquids under constant flow conditions, Chemical Engineering Science, 41 (1986) 97-105

Performance Evaluation Of Bubble Absorber Using R134a/DMF In Vapour Absorption Refrigeration System With Swirl Injector

Vapour absorption refrigeration systems (VARS) importance has increased due to utilization of solar energy, waste heat, etc. To improve the efficiency of this system, it is necessary to increase the heat and mass transfer in the absorber with tangential injectors. Experiments were carried out to analyze a tubular heat exchanger used as an absorber with tangential injector. In this study, a vertical bubble absorber is considered for heat and mass transfer studies with refrigerant, R134a (1,1,1,2 –Tetrafluoroethane) and absorbent, DMF(dimethyl formamide). R134a vapour is injected into the absorber using two injectors of 4.8 mm inner diameter at an injection angle of 30° to the vertical axis and parallel to the azimuthal axis of the absorber, which enhances mixing of R134a with liquid R134a-DMF solution to increase the heat and mass transfer. Experiments were carried out by varying the operational parameters by varying refrigerant flow rate from 5 lph to 15 lph and liquid solution flow rate in the range of 20 lph to 50 lph. Chilled water is used to load the refrigeration system evaporator with flow rate 100 lph and temperature in the range of 5 to 20oC. Hot water is supplied to the generator in the range of 60 to 91oC with flow rate of 80 to 200 lph. Cold water is used as coolant to the condenser and absorber in the temperature range of 11 to 25 oC with the flow rate of 80 to 160 lph. Effects of operational parameters viz., gas flow rate, solution initial concentration, and solution pressure and solution temperature and number of injector on absorber performance are varied and analysed. Mass transfer effectiveness, heat transfer effectiveness, overall heat transfer coefficient, volumetric mass transfer coefficient, absorption rate and heat rejected from the absorber have been evaluated for the absorber. Heat and mass transfer coefficients evaluated from the experiments are compared with numerical model and it is found to be in good agreement. REFERENCE Suresh M., Mani A. (2012), Experimental studies on heat and mass transfer characteristics for R134a-DMF bubble absorber, International Journal of refrigeration 35 pp. 1104-1114. Santosh Kumar Panda, Mani A. (2014), Bubble dynamics study with tangential nozzles in a bubble absorber, International Sorption Heat Pump Conference at Maryland University, Maryland,USA

DETERMINANTS OF PRIORITY SECTOR LENDING OF INDIAN PUBLIC SECTOR BANKS: AN ECONOMETRIC ANALYSIS

Compulsory sanctioning credit or priority sector lending (PSL) is part of the regulatory framework for commercial banks/ financial institutions in many countries, both developing and developed. However, compliance and lending effectiveness of such programs may be determined by a number of factors. This may be particularly so in developing countries, where availability of finance for the vulnerable sectors likes agriculture, small businesses, weaker sections, are scarce. The present paper aims at examining the patterns of priority sector lending by banks, with a view to identifying the factors which determine this lending The paper is based on an analysis of secondary data relating to priority sector lending (2006-07-2015-16) for the Public sector banks in India. The results indicate gaps in patterns of the sect oral target compliance by different bank groups, along with the lending preferences and challenges faced by banks in such lending. It also identifies bank-specific characteristics like the nature of ownership, size, performance, etc., which have a significant impact on the priority sector lending patterns. Based on its findings, the paper offers policy suggestions for improving the effectiveness of priority sector lending program

Social software, social networks, and online distance learning

Technology has had—and will continue to have—a significant impact on higher education. Nearly two-thirds (63%) of survey respondents from both the public and private sectors say that technological innovation will have a major influence on teaching methodologies over the next five years. In fact, technology will become a core differentiator in attracting students and corporate partners. It was the white paper from Economist Intelligence Unit called The Future of Higher Education: How technology will shape learning produced in 2008 and from which I would like to share with you some of the points made in the Executive Summary.UnisaInstitute for Open and Distance Learning (IODL

Web Site Productivity Measurement Using Single Task Size Measure

We propose a web site productivity measure using the average time taken by the proficient user takes in carrying out a transaction on a website to the total usage time of a web site. The total usage time of a web site depends on the size of the web site and bandwidth, the total time needed to use the information and other time factors. If productivity measurement of a web site delivers an expected productivity value in-between zero to one, then it indicates poor quality and the website needs to be redesigned, otherwise, if the value is bigger than one, which indicates higher expected productivity, then no need of updating. In this paper, we propose a productivity measurement method for web services. Finally, we demonstrate an example of its role for business to consumer web services using the new productivity measurement method

ANTIULCER ACTIVITY OF AMARANTHUS SPINOSUS LEAF EXTRACT AND ITS COMPARISION WITH FAMOTIDINE IN SHAY RATS

Anti-ulcer activities of petroleum ether, chloroform, Ethanolic extract of Amaranthus spinosus leaf were tested for anti-gastric ulcer activity in Shay rat model. Oral dose of 400mg/kg of ethanolic extract reduced the ulceration and with 800mg/kg body weight ethanolic extract there is the complete absence of ulceration. The anti-gastric activity of ethanolic extract of A.spinosus 800mg/kg body weight was found to be equal to the effect produced by 2mg/kg of Famotidine orally. The reduction in gastric activity was more with Famotidine and the reduction in peptic activity is more with ethanolic extract of A.spinosus. All extracts are safe up to 4000mg/kg. The result of petroleum ether, chloroform and aqueous extract in respect of anti-ulcer activity are less prominent. Keywords: Amaranthus spinosus, Shay rat model, Famotidine, Peptic activityÂ

Living fetus without congenital malformation in a singleton partial hydatidiform molar pregnancy: a case report and review of the literature

A 36 years old  lady gravida 2 para 1, came to our emergency ward at 9:30 pm on 12th  June 2010  with complains of bleeding p/v for 2 hours with history of bleeding at 12 weeks. On examination she was anemic and uterus was 32 weeks size with good fetal heart sound. Bleeding was coming through os, on p/s examination. Ultrasonography showed a single live fetus of 1033 grams and thickened placenta (79 mm thickness) showing multiple cystic lesion with peripheral hypervascularity, giving an impression of partial hydatidiform mole. She was managed conservatively and delivered a live preterm male child of 960 grams on 13th June 2010 evening without any congenital malformation. Placental weight was 1800 grams with multiple small vesicles. Now the boy is 4 years old and going to school with normal developmental milestone

Promjene srčanih biomarkera i ublažavanje simptoma trovanja arsenom u bijelih pataka pasmine pekinška patka nakon upotrebe đumbira

Cardiotoxicity is an imperative issue in the assessment of heavy metal consumption and inorganic arsenic (As). These have a cardiotoxic effect which is evaluated by biochemical, and oxidative-antioxidant tests, and by the Nrf2- HO-1 pathway. Dried ginger powder is recognized for its efficient antioxidant activities and as a protector of the cardiovascular system from toxic damage caused by heavy metals. However, the possible function of ginger against As in heart via heme oxygenase-1 (HO-1) and nuclear factor erythroid 2-related factor (Nrf2) is unclear. A total of 120 White Pekin ducks were randomly distributed into groups comprising 24 birds in each. Each group comprised 3 replicates having 8 birds in each replicate. The time period of this study was 90 days. The groups were the control [Group I] whereas groups II to IV were fed a basal diet including arsenic at 28 mg/L. Dried ginger powder as an ameliorative agent was mixed with the basal diet and fed at 0.1, 0.3 and 1 g/kg feed to groups III, IV and V, respectively. In the current experiment, dried ginger powder decreased As-induced reactive oxygen species (ROSs) production, oxidative injury and pathological modifications. In addition, cardiac dysfunction factors, intracellular calcium (Ca2+), As accumulation and cAMP deficiency levels were noticed in ducks; these alternations were attenuated by ginger. Furthermore, ginger significantly altered the down regulation of both HO-1 and Nrf2 gene expressions caused by As. Thus, the proven protective role of ginger against As-induced cardiotoxicity may be a consequence of the maintenance of redox homeostasis, i.e. the Nrf2-HO-1 pathway and by enabling As efflux.Kardiotoksičnost je vrlo važna u procjeni problema koji nastaju konzumacijom teških metala. Anorganski arsen (As) ima kardiotoksičan učinak koji se procjenjuje na temelju biokemijskih, oksidacijsko-antioksidacijskih nalaza te na temelju puta Nrf2-HO-1. Sušeni đumbirov prah poznat je po svojoj učinkovitoj antioksidacijskoj aktivnosti i zaštitnom djelovanju u slučaju intoksikacije kardiovaskularnog sustava teškim metalima. Nejasna je međutim uloga đumbira u odnosu na arsen u srčanom mišiću putem hem-oksigenaze 1 (HO-1) i faktora 2 povezanog s nuklearnim eritroidnim faktorom. Ukupno je 120 bijelih pataka pasmine pekinška patka nasumično podijeljeno u skupine koje su sadržavale po 24 jedinke. U svakoj skupini provedena su 3 ponovljena postupka (replikacije) na po 8 jedinki. Ukupno je vrijeme istraživanja bilo 90 dana. Skupina I bila je kontrolna skupina koja nije primila ni arsen ni đumbir. Pokusnim skupinama od II do V je, uz osnovnu prehranu, u različitim kombinacijama dodavan arsen u dozi od 28mg/L i sušeni đumbirov prah u dozama od 0,1g/kg 0,3g/kg i 1 g/kg. Rezultati su pokazali da je sušeni đumbirov prah smanjio prisutnost reaktivnih vrsta kisika (ROS) uzrokovanu arsenom, oksidacijsko oštećenje i patološke promjene. Osim toga uočene promjene, kao što su su faktori srčane disfunkcije, unutarstanični kalcij (Ca2+), nakupljanje arsena i deficijencija razine cAMP-a, ublažene su đumbirovim prahom. Đumbir je, nadalje, znakovito utjecao na smanjenje genske ekspresije i HO-1 i Nrf2 uzrokovane arsenom. Zaključeno je da bi zaštitna uloga đumbira u slučaju kardiotoksičnosti uzrokovane arsenom mogla biti posljedica održavanja redoks homeostaze, odnosno puta Nrf2-HO-1 i omogućavanja eliminacije arsena

Cu and Fe oxides dispersed on SBA-15:a Fenton type bimetallic catalyst for N,N-diethyl-p-phenyl diamine degradation

A bimetallic oxidation catalyst has been synthesized via wet impregnation of copper and iron over a mesoporous SBA-15 silica support. Physicochemical properties of the resulting material were characterized by XRD, N2 physisorption, DRUVS, FTIR, Raman, SEM and HRTEM, revealing the structural integrity of the parent SBA-15, and presence of highly dispersed Cu and Fe species present as CuO and Fe2O3. The CuFe/SBA-15 bimetallic catalyst was subsequently utilized for the oxidative degradation of N,N-diethyl-p-phenyl diamine (DPD) employing a H2O2 oxidant in aqueous solution