Syed Noman Danish

Performance Evaluation of Tandem Bladed Centrifugal Compressor

Abstract A tandem-bladed centrifugal compressor which may have better performance than the conventional designs has not yet been studied for its potential turbocharger application. In addition, no numerical study of the entire stage (including tandem impeller and volute) has been performed to fully exploit the benefits of such design with variation in axial clearance levels, circumferential clocking fractions, blade geometries/angles, number of inducer blades and the thickness of inducer blades. This paper presents a thorough experimental and numerical study on the performance of a moderate pressure ratio, unshrouded, tandem-bladed centrifugal compressor in comparison to a conventional compressor of commercial use in china for turbocharger application. The characteristics of a tandem compressor are investigated and compared for various parameters. Conventional impeller was first modified into tandem-bladed design but with no modifications in backsweep angle, meridional gas passage and camber distributions in order to have a true comparison. The tandem design was further modified and investigated by (1) narrowing down the meridional gas passage, (2) using straight or concave leading edge of exducer, (3) reducing the thickness and (4) the number of inducer blades. CFD and experimental results were found to be in good agreement. The study reveals a shift of surge point towards lower mass flow rate in all cases of tandem designs. A maximum of 25% increase in the range of operation is observed. All in all there is little influence of the different circumferential clocking fractions and axial spacings of the inducer. Computational investigations of a modified tandem compressor with 20% reduction in inducer thickness have shown better performance than the conventional design. Use of fourteen inducer blades with reduced blade thickness can further enhance the performance.

Modeling of Transient Energy Loss From a Cylindrical-Shaped Solid Particle Thermal Energy Storage Tank for Central Receiver Applications

The use of solid particles as a heat transfer and thermal energy storage (TES) medium in central receiver systems has received renewed attention in recent years due to the ability of achieving high temperatures and the potential reduction in receiver and TES costs. Performance of TES systems is primarily characterized by the percentage of heat loss they allow over a prescribed period of time. Accurate estimation of this parameter requires special attention to the transient nature of the process of charging the TES bin during solar field operation and discharging during nighttime or at periods where solar field operation is interrupted. In this study, a numerical model is built to simulate the charge-discharge cycle of a small cylindrical-shaped TES bin that is currently under construction. This bin is integrated into the tower of an experimental 300-kW (thermal) central receiver field being built in Riyadh, Saudi Arabia, for solid particle receiver research, most notably on-sun testing of the falling particle receiver concept within the context of a SunShot project. The model utilizes a type of wall construction that had been previously identified as showing favorable structural characteristics and being able to withstand high temperatures. The model takes into account the anticipated charge-discharge particle flow rates, and includes an insulating layer at the ceiling of the bin to minimize heat loss by convection and radiation to the receiver cavity located immediately over the TES bin. Results show that energy loss during the full charge-discharge cycle is 4.9% and 5.9% for a 5-hour and 17-hour discharge period, respectively. While large, these energy loss values are primarily due to the high surface-to-volume ratio of the small TES bin being investigated. Preliminary analysis shows that a utility-scale TES bin using the same concept will have an energy loss of less than 1%.Copyright

Nuclear Energy Powered Seawater Desalination

Abstract The shortage of drinkable water is a major problem encountered by a good number of countries around the globe. The production of potable water under new strategic cooperation frameworks becomes a visible state of the region that could facilitate the protection and preservation of water resources. This interactive framework may have the possibility to ensure the long-term security for many countries. One of the cost-effective methods of production potable water is the adoption of nuclear powered desalination technology. In this chapter, the state of the art and recent desalination technologies have been reported in-line with their application in renewable energy as comparative approach to nuclear energy. Most up-to date and available data of all operating and planned nuclear desalination units have been discussed. The option of small modular reactors (SMRs) as gaining imputes to desalination technology has been included along with the economic values. Theoretical and computational models needed for evaluating the performance of the coupled nuclear and desalination units have been put together. Computational and experimental facilities required for the desalination process have been included and discussed. Some countries of the Gulf Cooperation Council (GCC) have been selected as case studies for the implementation of nuclear power for the purpose of potable water production in the region. The possibilities and obstacles have been discussed based on scientific and policy-making issues. All these sections paved the way for feasibility studies and techno-economic assessment of nuclear powered desalination units.

PERFORMANCE ASSESSMENT OF ALTERNATE REFRIGERANTS FOR RETROFITTING R22 BASED AIR CONDITIONING SYSTEM

The performance of zero Ozone Depletion Potential (ODP) refrigerants is investigated when retrofitted in R22 based air conditioning system. The options evaluated are R407C, R417A, R422D, R427A and R438A. In order to arrive at most suitable alternative/s to R22, energy and exergy performance of candidate refrigerants is carried out and compared against that of R22. The COPs and exergy efficiencies showed that none of selected refrigerant is as efficient as R22 however their values suggests that each may be considered as potential substitute for retrofitting. Having comparable COP to others but low cooling capacity of R417A makes it less attractive. With comparatively reduced COP, lowest exergy efficiency and highest mass flow rate, makes R422D the least desirable option. R407C, R427A and R438A emerged as most attractive substitutes. The lower discharge temperatures of substitutes will enhance the compressor life. Further, for substitutes there may be a possible change out of expansion valve.

Experimental measurements of thermal properties of high-temperature refractory materials used for thermal energy storage

This paper builds on studies conducted on thermal energy storage (TES) systems that were built as a part of the work performed for a DOE-funded SunShot project titled “High Temperature Falling Particle Receiver”. In previous studies, two small-scale TES systems were constructed for measuring heat loss at high temperatures that are compatible with the falling particle receiver concept, both of which had shown very limited heat loss. Through the course of those studies, it became evident that there was a lack of information about the thermal performance of some of the insulating refractory materials used in the experiments at high temperatures, especially insulating firebrick and perlite concrete. This work focuses on determining the thermal conductivities of those materials at high temperatures. The apparatus consists of a prototype cylindrical TES bin built with the same wall construction used in previous studies. An electric heater is placed along the centerline of the bin, and thermocouples are used to ...

Experimental study of compatibility of reduced metal oxides with thermal energy storage lining materials

Solid particles have been shown to be able to operate at temperatures higher than 1000 °C in concentrated solar power (CSP) systems with thermal energy storage (TES). Thermochemical energy storage (TCES) using metal oxides have also found to be advantageous over sensible and latent heat storage concepts. This paper investigates the compatibility of the inner lining material of a TES tank with the reduced metal oxide. Two candidate metal oxides are investigated against six candidate lining materials. XRD results for both the materials are investigated and compared before and after the reduction of metal oxide at 1000°C in the presence of lining material. It is found that the lining material rich in zirconia is suitable for such application. Silicon Carbide is also found non-reacting with one of the metal oxides so it needs to be further investigated with other candidate metal oxides.

SIMULATION OF NORMAL/ABNORMAL OPERATIONAL CONDITIONS OF INTEGRAL PRESSURIZED WATER REACTOR BY USING RELAP5/MOD3.4

Abstract This paper is focused on the normal and abnormal operational states of small nuclear reactor (integral pressurized water reactor) by analysing with thermal hydraulic system code RELAP5/MOD3.4. For this purpose, the reactor considered is INSURE-100 with the power output of 100 MW. Concerning with the normal operational conditions, the steady-state results as well as load variation characteristics have been carried out and for the abnormal conditions, preliminary assessment of the reactor under two accident conditions i.e., loss of feed water and main steam line break have been researched and are well explained with the help of graphical analysis by using RELAP5 code. The research is also focused on the safety of the considered reactor, and for this purpose the reactor was design to be of pool-type reactor. The graphical results and the parameters that have been extracted from the RELAP5/MOD3.4 code show good agreement for the safe evaluation of the reactor.

Experimental and FEM Study of Serrated Chip Formation in High Speed Turning Processes

The finite element method (FEM) has been used to model high speed turning processes with orthogonal cutting conditions. In most of the situations, continuous chip formation is used to analyze the turning process due to its stability and allowing many conditions to simplify the process. However with the increasing applications of high speed turning, serrated chip formation is becoming a more common phenomenon in metal cutting. Serrated chips usually occur in machining of difficult to cut materials at or above a threshold speed. An updated Lagrangian formulation has been used in this study which works with element deletion technique based on a failure criterion. The Johnson Cook strain-hardening thermal-softening material model is used to model serrated chip formation. In addition high speed turning experiments were conducted on AISI H13 tubes using PCBN to analyze serrated chip phenomenon. The chips were analyzed after surface treatment using scanning electron microscope. It has been found that the length of cuts in the chip increases with the cutting speed and the chip changes from serrated to discontinuous. Different process variables like cutting forces, chip morphology, stress, strain and temperature distributions are predicted at different process parameters using FEM. The results show cyclic variation in the cutting forces at high cutting speeds due to varying chip load.