Wall thinning and creep damage analysis in boiler tube and optimization of operating conditions

The boiler tubes are operated continuously at high temperature and pressure. During operation,scales are formed in boiler tube due to tube geometries, flue gas and steam temperature. The remaining wall thickness decreases due to the formation of scale which eventually causes failure of the boiler tubes. In this investigation an iterative technique was used to determine the temperature distribution across the tube with the operating time. The operating time was considered up to 160,000 hours. The remaining life of the steam generator tube was found by finding hoop stress and Larson Miller Parameter from the Larson Miller Parameter curve for SA213-T22 material. By utilizing finite element modelling software, ANSYS 9/ANSYS 11 the temperature distribution across the steam generator tube was evaluated. The increase of heat transfer rate across the wall caused the oxide scale thickness to grow more rapidly than normal condition. It was also observed that due to formation of scale the thermal conductivity in the boiler tubes was affected and the remaining life of boiler tubes was decreased and accelerated creep damage. The ANSYS result was analyzed by Minitab 16 to determine the main and interactive effects of operating conditions. Steam temperature was influencing most the wall thinning and creep damage in comparison to the flue gas temperature. The interactive effects of both the parameters were also prominent. Moreover, the optimum operating condition was identified in order to maximizing the remnant life of the tubes while minimizing the creep rupture damage

An Improved Optimization Model of Internet Charging Scheme in Multi Service Networks

This article will analyze new improved charging scheme with base price, quality premium and QoS networks involved. Sain and Herpers [5] already attempted to obtain revenue maximization by creating charging scheme of internet. The plan is attempted to solve multi service networks scheme as an optimization model to obtain revenue maximization using our improved model based on Byun and Chatterjee [2] and Sain and Herpers [5]. The results show that improved model can be solved optimally using optimization tool LINGO to achieve better revenue maximization. Better results are obtained in all cases rather than in [5]. The advantage of our new model is that ISP also can set up their base price and quality premium based on ISP preferences. For some cases for getting revenue maximization, we do not offer one service and just utilize some of the services

Spatial assessment on ambient air quality status: a case study in Klang, Selangor

Klang as the center of economic and industrial zone in Malaysia has been exposed to poor air quality condition over the years. This study was conducted to evaluate the spatial variation pattern of air quality status in Klang, Selangor by using a four years (2010-2013) secondary database from the Malaysian Department of Environment (DOE). The finding shows that carbon monoxide (CO) had a strong correlation with nitrogen dioxide (NO2) (r = 0.76, p < 0.001), while Air Pollutant Index (API) had moderate correlation with particulate matter (PM10) (r = 0.64, p < 0.001). Principal Component Analysis (PCA) indicates that the most significant air pollutants were NO2, CO and PM10. Statistical Process Control (SPC) reveals that several PM10 data beyond the limitations of SPC and the national guidelines. This study shows that active collaboration among all relevant environmental departments and agencies should be implemented for the effective management of air quality.Keywords: air quality; correlation; principal component analysis; statistical process control

Solar water distillation by using water in the inner glass evacuated tubes

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.Evacuated tubes are made from two layers of glasses. The inside glass is coated and the space between the glasses is evacuated. When sun radiations pass through the first layer and transfer heat to the inner side, since the space between them is evacuated it cannot cool down with convection or conduction. The common way of using an evacuated tube is to put an evacuated copper rod inside it to heat up and make contact with a water container to let the water boil. In the current study water is directly inside the inner evacuated tubes. Thus, the evaporation happens in these tubes and there is no need to use a water container or copper rods. Results show that when the amount of water is increased in the tubes the production raises significantly. Result for two values of volume of water in two days with acceptable similar solar radiation and ambient temperature are reported.dc201

Gastrografin in the management of adhesive small bowel obstruction in children: a pilot study

Background/purpose Adhesive small bowel obstruction (ASBO) is a common emergency problem in children with previous abdominal surgery. Management protocols usually start with a conservative approach that may be successful in some cases, whereas in others it will end eventually by laparotomy with its associated morbidity and mortality. Our aim was to assess the role of water-soluble contrast, gastrografin, in the conservative management of ASBO. Patients and methods During the period January 2009 to July 2010, 33 patients with ASBO were presented at the Pediatric Surgery Unit at the Ain Shams University Hospitals. Patients who failed to improve after 48 h of conservative management in the absence of signs of strangulation were subjected to gastrografin administration. Patients were evaluated clinically and radiologically to determine the resolution of the adhesive attack, with estimation of hospital stay time. Results An oral administration of gastrografin successfully completed the conservative management in eight of 12 patients (66.6%), thus avoiding surgery and subsequently reducing hospital stay. Conclusion Gastrografin may have a valuable role in the management of ASBO, whether diagnostic or therapeutic, but a randomized controlled trial is needed to prove its effectiveness in reducing surgical intervention rate and hospital stay time.Keywords: adhesive, bowel obstruction, gastrografi

MODELING SEASONAL WINE GRAPE DEVELOPMENT USING A MIXTURE TECHNIQUE

Biological growth data typically display an increasing sigmoidal pattern over time. Grape development is no exception and shows a similar general trend. A detailed examination of the growth process in grapes, however, reveals a few systematic deviations from this pattern. Specifically, grape development is often characterized by localized areas of growth plateaus leading to an overall growth pattern referred to as a double sigmoidal curve. Capturing and characterizing these local changes in growth is important as they represent important phases in grape development such as veraison. This paper utilizes a model adapted from the technique of mixture models to estimate the growth curve of grapes. The resulting model provides a more accurate description of the growth process and has parameter estimates directly related to the various phases of grape development. The model is demonstrated using data collected from an experimental trellis tension monitoring system in the Chardonnay grape varietie

Exergy Analysis of a Flat Plate Solar Collector in Combination with Heat Pipe

ABSTRACT: The use of solar collectors in combination with heat pipes is rapidly growing in recent years. Heat pipes, as heat transfer components, have undeniable advantages in comparison with other alternatives. The most important advantage is their high rate of heat transfer at minor temperature differences. Although there have been numerous studies on the heat analysis or first thermodynamic analysis of flat plate solar collectors in combination with heat pipes, the exergy analysis of these collectors is needed to be investigated. In this work, energy and exergy analysis of a flat plate solar collector with a heat pipe is conducted theoretically. Next, the exergy efficiency of pulsating heat pipe flat plate solar collectors (PHPFPSC) is compared with conventional collectors by using the experimental data. The results indicate that the use of heat pipes for heat transfer from the absorption plate to the water reservoir has significantly higher availability and exergy efficiency than the case with conventional collectors with intermediate fluid

Assessment of Service Quality in Teaching Hospitals of Yazd University of Medical Sciences: Using Multi-criteria Decision Making Techniques

Objectives Hospitals as integrated parts of the wide-ranging health care systems have dominant focus on health care provision to meet, maintain and promote people's health needs of a community. This study aimed to assess the service quality of teaching hospitals of Yazd University of Medical Sciences using Fuzzy Analytical Hierarchy Process (FAHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). Methods A literature review and a qualitative method were used to obtain experts� viewpoints about the quality dimensions of hospital services to design a questionnaire. Then, using a self-made questionnaire, perceptions of 300 patients about the quality of delivered services were gathered. Finally, FAHP was applied to weigh each quality dimension and TOPSIS method to rank hospital wards. Results Six dimensions including responsiveness, assurance, security, tangibles, health communication and Patient orientation were identified as affecting aspects of hospital services quality among which, security and tangibles got the highest and lowest importance respectively (0.25406, 0.06883). Findings also revealed that in hospital A, orthopedics and ophthalmology wards obtained the highest score in terms of quality while cardiology department got the lowest ranking (0.954, 0.323). In hospital B, the highest and the lowest ranking was belonged to cardiology and surgical wards (0.895, 0.00) while in hospital C, surgical units were rated higher than internal wards (0.959, 0.851). Conclusion Findings emphasized that the security dimension got the lowest ranking among SERVQUAL facets in studied hospitals. This requires hospital executives to pay special attention to the issue of patients� security and plan effectively for its promotion. © 201