Performance Evaluation of Vortex Generator of Finite Thickness to Augment Heat Transfer in a Compact Heat Exchanger

The effect of non dimensional thickness of a winglet type vortex generator is investigated in terms of heat transfer rate, stream-wise vortices and flow losses in a plate fin heat exchanger with triangular inserts as secondary fins. The winglet type vortex generators are mounted alternatively on the upper and lower plates of the heat exchanger to disrupt the flow in the triangular domain formed by the inserts. The fluid flow within the duct is considered to be confined and laminar. While the hydrodynamic flow is fully developed, the thermal characteristics are assumed to be in developing stage under isothermal boundary conditions. The winglet is located in the duct where the flow is fully developed (Xi = 2.765 w.r.t. leading edge) at an angle of 27o with respect to the bulk flow direction. The aforesaid performance characteristics are computed numerically by solving the mass continuity, momentum and energy equations. Computational results clearly show an enhancement of 12.91% in the heat transfer rate (quantified as Num/ Nuo) for an increase in non dimensional thickness c/2H from 0.00 to 0.05. Besides, the pressure drop penalty is found to be only 3.8% at Re = 150. The results have also been substantiated by carrying out experiments on a scaled model configuration. Three dimensional velocity components are verified behind the winglet to ensure the stable flow field for non dimensional thickness of winglet c/2H=0.05 and Reynolds number of 350

Performance analysis of a vapour compression-absorption cascaded refrigeration system with undersized evaporator and condenser

In a present study, the performance of a vapour compression–absorption cascaded refrigeration system (CRS) under fouled conditions was analysed. The main effect of fouling is to decrease the effectiveness of the heat exchanger. Thus, the overall conductance (UA) of the heat exchanger is decreased. Hence, another interpretation of fouling is to reduce the effective size of the heat exchanger. In the present work, the percentage decrease in the overall conductance value (UA) of evaporator and condenser due to their fouling is varied from 0 to 50% and its consequences on various aspects of CRS are generated to ascertain any possible patterns. The detailed first law analysis reveals that for a clean evaporator and condenser, the electricity consumption is 67.5% less than vapour compression system (VCS) for the same cooling capacity. CRS is able to save only 61.3% of electrical energy when evaporator and condenser conductance is reduced by 50% due to fouling. Evaporator and condenser fouling decreased the COP and rational efficiency of the system by 4.7% and 10.5% respectively. It is also important to note that irreversibility in the evaporator and condenser is increased by 42.4% and 62.1% respectively, when their individual performance is degraded by 50% due to fouling

Growth Based Strategy Formulation for Selection of Murrah Buffalo at Early Ages

Buffaloes form the backbone of farmers in Indian dairy industry. The birth weight and weight at different age of an animal characterizes expression of animals’ genotype and serves as reliable aid to selection for efficient performance of livestock. The data on body weight were collected on 726 new born female calves and 642 male calves of livestock farm, NDRI, Karnal. Growth curves for both male and female buffalo calves were prepared by plotting mean of the body weight against age in weeks and Growth band were prepared by computing upper and lower limits of average body weights (95% confidence limit), from birth to 6 month of age, at weekly interval. The growth curves were found to be linear for both male and female buffalo calves. Growth band was narrow at the birth, but it goes on widening with age at successive weeks. The presentation of growth band is expected to be useful in making an efficient decision for proper management of animals at various ages

Piloting Upfront Xpert MTB/RIF Testing on Various Specimens under Programmatic Conditions for Diagnosis of TB & DR-TB in Paediatric Population

India accounts for one-fifth of the global TB incidence. While the exact burden of childhood TB is not known, TB remains one of the leading causes of childhood mortality in India. Bacteriological confirmation of TB in children is challenging due to difficulty in obtaining quality specimens, in the absence of which diagnosis is largely based on clinical judgement. While testing multiple specimens can potentially contribute to higher proportion of laboratory confirmed paediatric TB cases, lack of high sensitivity tests adds to the diagnostic challenge. We describe here our experiences in piloting upfront Xpert MTB/RIF testing, for diagnosis of TB in paediatric population in respiratory and extra pulmonary specimens, as recently recommended by WHO.Xpert MTB/RIF testing was offered to all paediatric (0-14 years) presumptive TB cases (both pulmonary and extra-pulmonary) seeking care at public and private health facilities in the project areas covering 4 cities of India.Under this pilot project, 8,370 paediatric presumptive TB & presumptive DR-TB cases were tested between April and-November 2014. Overall, 9,149 specimens were tested, of which 4,445 (48.6%) were non-sputum specimens. Xpert MTB/RIF gave 9,083 (99.2%, CI 99.0-99.4) valid results. Of the 8,143 presumptive TB cases enrolled, 517 (6.3%, CI 5.8-6.9) were bacteriologically confirmed. TB detection rates were two fold higher with Xpert MTB/RIF as compared to smear microscopy. Further, a total of 60 rifampicin resistant TB cases were detected, of which 38 were detected among 512 presumptive TB cases while 22 were detected amongst 227 presumptive DR-TB cases tested under the project.Xpert MTB/RIF with advantages of quick turnaround testing-time, high proportion of interpretable results and feasibility of rapid rollout, substantially improved the diagnosis of bacteriologically confirmed TB in children, while simultaneously detecting rifampicin resistance