Effect of inlet ducts on the performance of a vaneless diffuser of a centrifugal compressor

Dr. Basharat Salim Associate Professor ([email protected] ) Department of Mechanical Engineering College of Engineering, King Saud UniversityCentrifugal compressor is being used for in wide variety of industries. The impeller and diffuser form the basic components of a centrifugal compressor. The vaneless diffuser is primarily used for low or moderate pressure ratios and it provides wide operating range. Centrifugal compressor usually discharges non-uniform flow into the diffuser. This nature of exit flow from the impeller deteriorates the performance of the down stream vaneless diffuser. The development of the flow in a wide vaneless diffuser with a radial- bladed impeller upstream of it is the subject matter of this paper. The results are being reported in terms of variation of radial velocity, total pressure and flow angle along the radial path of the vaneless diffuser. The results are presented for the flow rate corresponding to maximum point of the characteristics of the compressor for three inlet duct shapes. Besides the performance parameters like static pressure rise coefficient, total pressure loss coefficient and pressure recovery coefficient for all these cases have also been presented. The results depict a strong dependence of vaneless performance and flow behavior on the inlet duct shapes and flow rate.Corresponding Author: Dr. Basharat Salim Associate Professor Department of Mechanical Engineering College of Engineering, King Saud University Riyadh, Saudi Arabia. Email: [email protected]

Selection of an Appropriate Solar Thermal Technology for Solar Vapor Absorption Cooling—An MADM Approach

Different solar thermal collectors have been used recently to meet the thermal requirements of single effect and double effect vapor absorption cooling systems, making selection of the correct method a challenge. Different attributes of each vapor absorption cooling and solar collector combination are taken into account, and a Multi-Attribute Decision-Making model is used to select the best option. The model requires variables indicating the performance of the system, which are called attributes that are organized into a hierarchical structure called a tree of attributes. The dependent attributes finally end up in the basic attributes representing the input to the model. The technology options considered are flat plate water heating collectors with forced circulation, flat plate air heating collectors with forced circulation, evacuated tube collectors, parabolic trough collectors, and collectors with compound parabolic concentrator. Two types of cooling, namely single effect and double effect, are compared. Three climatic zones with three different cooling loads, ambient temperatures and solar radiation intensity have been considered. Comparison of the solar vapor absorption technologies with vapor compression technology is made considering the major performance factors. The major attributes, namely cost and emissions produced, are compared with conventional vapor compression methods

Improved Prediction Model and Utilization of Pump as Turbine for Excess Power Saving from Large Pumping System in Saudi Arabia

The throttling process is frequently encountered in many industrial practices utilizing Pressure Reducing Valves (PRVs). This process is typically used to control pressure and flow in pipeline networks. The practice of utilizing PRVs is considered simple and cheap in terms of installation cost and control. It dissipates the excess fluid energy that can be used for other purposes. This paper studies the feasibility of utilizing the Pump as Turbine (PAT) concept to partially recover the excess power dissipated from PRVs located at the discharge lines of refined product shipping pumps at one of the hydrocarbon distribution facilities in Saudi Arabia. Multiple PAT installation layouts have been studied to achieve this goal, selecting the optimum option to maximize the power recovery. The final selection of PAT was conducted to achieve a reasonable payback period. A new method for predicting the pump performance in reverse mode was developed depending on the manufacturer’s pump performance curves. The comparison of the proposed model with experimental data and previous models for three modes of operation reveals that the proposed model in this paper’s results either have the minimum deviation or the second minimum deviation out of all models. In the case of flow ratio prediction, the predicted deviation is merely 3.83%, −1.14%, and 1.35% in three modes of operation. For power prediction, the proposed model is the best and the only reliable model out of all with the least deviation of −7.48%, 0.07%, and −3.16% in three modes of operation. The economic analysis reveals the Capital Payback Time (CPP) for five optimum PATs is around 5 years. The new method was also validated against previous models showing more precise performance prediction of multistage centrifugal pumps running in turbine mode

Comparative transcriptome analysis reveals the genetic basis of coat color variation in Pashmina goat

Abstract The genetics of coat color variation remains a classic area. Earlier studies have focused on a limited number of genes involved in color determination; however, the complete set of trait determinants are still not well known. In this study, we used high-throughput sequencing technology to identify and characterize intricate interactions between genes that cause complex coat color variation in Changthangi Pashmina goats, producer of finest and costly commercial animal fiber. We systematically identified differentially expressed mRNAs and lncRNAs from black, brown and white Pashmina goat skin samples by using RNA-sequencing technique. A pairwise comparison of black, white and brown skin samples yielded 2479 significantly dysregulated genes (2422 mRNA and 57 lncRNAs). Differentially expressed genes were enriched in melanin biosynthesis, melanocyte differentiation, developmental pigmentation, melanosome transport activities GO terms. Our analysis suggested the potential role of lncRNAs on color coding mRNAs in cis and trans configuration. We have also developed online data repository as a component of the study to provide a central location for data access, visualization and interpretation accessible through http://pcd.skuastk.org/