ELEMENTARY ASSESSMENTS AND SIMULATIONS BASED PROPOSALS FOR NEW HEAT TRANSFER CORRELATIONS AND FLOW REGIME MAPS FOR ANNULAR/STRATIFIED REGIME OF SHEAR DRIVEN INTERNAL CONDENSING FLOWS

Contemporary cooling applications necessitate the use of mm-scale shear driven flow condenser designs which also need to ensure substantial heat transfer rates for a wide range of flow conditions. Some modern shear driven flow condensers must meet the requirements of small size and large heat flux removal capability for variety of flow conditions. For this, effective estimates of heat transfer rate correlations and correlations for estimating the length of the annular regime are essential. Existing heat transfer correlations are built based on semi-empirical approaches which are primarily supported by large data sets, which are often mixed with insufficient explanation and also do not exhibit a direct relation to flow physics based modelling of condensing flows. Typical heat transfer correlations primarily eliminate the dependency of heat transfer coefficient on the method of cooling imposed on the cooling surface of the condenser. These correlations are typically reported in terms of vapor quality, on which the heat transfer coefficient depends. Correlations based on quality instead of physical distance are preferred because the rest depends on the method of cooling . The energy balance equation is then used to obtain a spatial variation of vapor quality along the length of the condenser. However, in fundamental physics based approaches, heat transfer coefficients are significantly dependent on thermal boundary conditions. This study focuses on bridging the knowledge gap between the semi-empirical approaches of typical correlations in literature and the direct flow physics based fundamental results from theory, computation and experiments. This study further explains the equivalency of physics based modelling to typical approach under certain conditions. An important factor that needs vigilant observation on typical heat transfer correlations is the obscurity associated with the application of flow regime maps for internal condensing flows. Heat transfer rate is strongly influenced by the type of flow, but several heat transfer correlations are presented that cover several different flow regimes. This means correlations approach and data have to be good enough to accommodate significant variations in the correlated values of the heat transfer rates among different flow regimes. Flow regime maps in literature are also inaccurate because the assembled data from different experiments are examples of data on thermal boundary conditions and the downstream physical distances and quality where transitions are observed. This is believed to be true as these flow regime map data are not properly non-dimensionalized or have not been differentiated by suitable flow physics, further exacerbating their use for different flow applications. The key objective of this study (primarily restricted to shear driven annular flow regimes) is to establish the need for heat transfer correlations which are fundamentally (based on flow physics) constructed and compare their predictions with these obtained from correlations and flow regime maps existing in literature. This study also provides a basic structure for creating similar new correlations for various other flow types and regimes. For annular flows this is done by using two numerical tools, one which is highly efficient but in an approximate flow simulation tool (A Quasi 1-D Simulation tool [2]) and a nearly exact 2-D steady/unsteady simulation tool [3]

Fundamental assessments and new enabling proposals for heat transfer correlations and flow regime maps for shear driven condensers in the annular/stratified regime

Modern-day applications need mm-scale shear-driven flow condensers. Condenser designs need to ensure large heat transfer rates for a variety of flow conditions. For this, good estimates for heat-transfer rate correlations and correlations for the length of the annular regime (beyond which plug-slug flows typically occur) are needed. For confident use of existing correlations (particularly the more recent ones supported by large data sets) for shear-pressure driven internal condensing flows, there is a great need to relate the existing correlation development approaches to direct flow-physics based fundamental results from theory, computations, and experiments. This paper addresses this need for millimeter scale shear driven and annular condensing flows. In doing so, the paper proposes/compares a few new and reliable non-dimensional heat-transfer coefficient correlations as well as a key flow regime transition criteria/correlation

Syndrome Evaluation System for Simultaneous Detection Pathogens Causing Acute Encephalitic Syndrome in India, Part-1: Development and Standardization of the Assay

A large number of organisms are known to cause acute encephalitic syndrome (AES). A number of diagnostic tests have to be performed in order to arrive at a probable pathogen causing AES thus making it a very time consuming, laborious and expensive. The problem is further compounded by the lack of availability of sufficient volume of Cerebrospinal fluid (CSF). Thus, there is an urgent need of a diagnostic tool for the simultaneous detection of all probable pathogens responsible for causing AES. Here we report the development of a novel diagnostic method, Syndrome Evaluation System (SES) for the simultaneous detection of 22 pathogens including RNA and DNA Viruses, bacteria, fungi, and parasite all endemic to India and Southeast Asia in a single sample using a novel multiplexing strategy. Syndrome Evaluation System (SES) involves isolation of nucleic acid, multiplex amplification of the DNA, and cDNA followed by identification of the amplified product by sequence specific hybridization on SES platform with the final read out being a visually recordable colored signal. The total time required to carry out this diagnostic procedure is 7 h. The SES was standardized using the commercially available vaccines, panels and cell culture grown quantified viruses/bacteria/fungi. The limit of detection (LOD) of SES ranged between 0.1 and 50 viral particles per ml of CSF and 100 to 200 bacterial cells or 5 parasites per ml of CSF, along with 100% specificity. Precision studies carried out as per the Clinical Laboratory Improvement Amendments (CLIA) guidelines, using two concentrations of each pathogen one the LOD and the other double the LOD, clearly demonstrated, that inter/intra assay variability was within the limits prescribed by the guidelines. SES is a rapid molecular diagnostic tool for simultaneous identification of 22 etiological agents of AES encountered both in sporadic and outbreak settings