Avian Influenza Outbreaks in Chickens, Bangladesh

To determine the epidemiology of outbreaks of avian influenza A virus (subtypes H5N1, H9N2) in chickens in Bangladesh, we conducted surveys and examined virus isolates. The outbreak began in backyard chickens. Probable sources of infection included egg trays and vehicles from local live bird markets and larger live bird markets

Risk for Infection with Highly Pathogenic Avian Influenza Virus (H5N1) in Backyard Chickens, Bangladesh

Risk factors were feeding slaughter remnants of purchased chickens, having a body of water nearby, and contact with pigeons

Prevalence and Characterization of Motile Salmonella in Commercial Layer Poultry Farms in Bangladesh

Salmonella is a globally widespread food-borne pathogen having major impact on public health. All motile serovars of Salmonella enterica of poultry origin are zoonotic, and contaminated meat and raw eggs are an important source to human infections. Information on the prevalence of Salmonella at farm/holding level, and the zoonotic serovars circulating in layer poultry in the South and South-East Asian countries including Bangladesh, where small-scale commercial farms are predominant, is limited. To investigate the prevalence of Salmonella at layer farm level, and to identify the prevalent serovars we conducted a cross-sectional survey by randomly selecting 500 commercial layer poultry farms in Bangladesh. Faecal samples from the selected farms were collected following standard procedure, and examined for the presence of Salmonella using conventional bacteriological procedures. Thirty isolates were randomly selected, from the ninety obtained from the survey, for serotyping and characterized further by plasmid profiling and pulsed-field gel electrophoresis (PFGE). Results of the survey showed that the prevalence of motile Salmonella at layer farm level was 18% (95% confidence interval 15–21%), and Salmonella Kentucky was identified to be the only serovar circulating in the study population. Plasmid analysis of the S. Kentucky and non-serotyped isolates revealed two distinct profiles with a variation of two different sizes (2.7 and 4.8 kb). PFGE of the 30 S. Kentucky and 30 non-serotyped isolates showed that all of them were clonally related because only one genotype and three subtypes were determined based on the variation in two or three bands. This is also the first report on the presence of any specific serovar of Salmonella enterica in poultry in Bangladesh

Study on Geothermal Heat Exchangers With Nanofluids Containing Ceramic Nanoparticles

A geothermal heat exchanger (GHE) uses geothermal energy for heating or cooling residential places during winter or summer. Two different designs of GHEs, the straight pipe and coiled pipe designs, are evaluated in this study, and the effect of nanofluids as the working fluid is investigated. For this purpose, a mathematical model is developed, validated, and used to predict the temperature gain, heat gain, exergy gain, and pressure loss of the working fluid for different concentrations of additive ceramic nanoparticles of aluminum oxide (Al2O3) and magnesium oxide (MgO) in the working fluid. It is shown that the coiled pipe design has a better performance compared to the straight pipe design for GHEs. It is also shown how the temperature, heat gain, and exergy gain change with increasing the additive nanoparticles into the base fluid, which is water, while the pressure loss does not change significantly. The temperature gain increases about 60% when the volume fraction of nanoparticles in the base fluid reaches 2%. This also helps to improve the natural circulation of working fluid and the GHE may not need a circulating pump to run at low flowrates. It is also shown that the additive MgO nanoparticles are more effective than Al2O3 nanoparticles to improve the GHE performance

A Multiple-Grid Lattice Boltzmann Method for Natural Convection under Low and High Prandtl Numbers

A multi-distribution lattice Boltzmann Bhatnagar–Gross–Krook (BGK) model with a multiple-grid lattice Boltzmann (MGLB) model is proposed to efficiently simulate natural convection over a wide range of Prandtl numbers. In this method, different grid sizes and time steps for heat transfer and fluid flow equations are chosen. The model is validated against natural convection in a square cavity, since extensive benchmark solutions are available for that problem. The proposed method can resolve the computational difficulty in simulating problems with very different time scales, in particular, when using extremely low or high Prandtl numbers. The technique can also enhance computational speed and stability while keeping the simplicity of the BGK method. Compared with the conventional lattice Boltzmann method, the simulation time can be reduced up to one-tenth of the time while maintaining the accuracy in an acceptable range. The proposed model can be extended to other lattice Boltzmann collision models and three-dimensional cases, making it a great candidate for large-scale simulations

Effect of Filling Ratio on Heat Transfer Characteristics and Performance of a Closed Loop Pulsating Heat Pipe

AbstractThermal control is a generic need for any heat dissipation system. Heat pipes emerge as the most appropriate technology and most thermal effective solution due to their excellent heat transfer capability, heat transfer efficiency and structural simplicity. In many engineering applications higher heat flux is important. Two phase passive devices are proven solutions for modern microelectronics thermal management. This paper attempts to describe the heat transfer characteristics of closed loop pulsating heat pipe (CLPHP) which are new entrants in the family of closed passive two phase heat transfer system. It also shows the comparison of thermal efficiency of CLPHP for different filling ratios with two different working fluids, water and ethanol. This device is a combination of lot of events and mechanisms like bubble nucleation, collapse and agglomeration, bubble pumping action, pressure and temperature perturbations, flow regime changes, dynamic instabilities, meta-stable non equilibrium conditions, flooding, bridging etc. All contribute towards the thermal performance of a device. But, such a complex operating mechanism is not understood well yet and the present state of the art cannot predict the required design parameters for a given task. The aim of research work presented in this paper is to better understand the heat transfer characteristics of these mechanisms through experimental investigations. Experiments are conducted on a CLPHP made of capillary tube of 2.2mm inner diameter. The heat transfer characteristics and the performance of the CLPHP are investigated for filling ratios of 100%, 82.5%, 63%, 41.3% and 28%. The results indicate that the performance of this device changes with the changing of working fluid, filling ratios and heat input