Raj Calay - Academia.edu (original) (raw)

Papers by Raj Calay

Energy harvesting from suspension system using regenerative force actuators

2018 Advances in Science and Engineering Technology International Conferences (ASET), 2018

Heat engines, such as internal combustion engines, have significant adverse effects on the enviro... more Heat engines, such as internal combustion engines, have significant adverse effects on the environment due to their heat and harmful emissions. In addition, they are dependent on energy from fossil resources, which are depleting rapidly and they are not being properly utilized due to the relatively low efficiency of heat engines usually expressed by Carnot's efficiency. The low temperature direct conversion process, in which hydrogen is chemically oxidized, is one of the best alternatives to heat engines. In this process, the heat emitted to the surroundings, or in driving the reaction, is kept to a minimum. This method would meet the pressing need of humanity to find power generation and utilization techniques that are more efficient and less harmful to the environment than conventional power generation methods. This will also help to conserve energy resources, and at the same time, protect the environment by reducing the amount of harmful emissions, and thermal loading i.e. greenhouse effects. In fact, the fuel cell technology can overcome these difficulties and pave the way for utilizing different sources of energy. This paper investigates the possibility of utilizing fuel cell technologies in Dubai public transportation and in particular the rail systems. This matter is critical for Dubai since it is one of the fastest growing cities. Recently Dubai has launched the Clean Energy Strategy, which aims to make Dubai a global centre of clean energy and green economy. The utilization of fuel cell technology is very important for Dubai since it has the potential to increase energy efficiency of the transportation sector, increase energy security, improve environmental quality, and position Dubai as a leading city in advanced rail transportation.

Journal of Chemical Technology & Biotechnology, 2015

BACKGROUND: A continuous stirred tank bioreactor (CSTBR) represents an open dynamic system with h... more BACKGROUND: A continuous stirred tank bioreactor (CSTBR) represents an open dynamic system with high probability to show nonlinear behavior such as parametric sensitivity and multiplicity of steady state. A priori determination of this behavior is needed to decide on the strategy of reactor operation. RESULTS: The growth of a lactic acid bacterium, namely, Pediococcus acidilactici in a 2 L CSTBR is used to demonstrate the existence of parametric sensitivity of pH and the multiplicity of steady state in the system. A mathematical model has been developed and a dimensionless multiplicity criterion, , has been derived to indicate the set of values of input parameters corresponding to multiple steady states. Experiments have been conducted to study parametric sensitivity of pH with respect to input variables, namely, dilution rates and concentrations of nutrient and alkali stream for pH control in the regions of multiple and unique steady states. The CSTBR exhibited parametric sensitivity of pH over the entire region of operation under study. The experimental trends of parametric sensitivity of pH are also in agreement with those of theoretical parametric sensitivity of pH. CONCLUSION: The nonlinear behavior of a CSTBR has been thoroughly portrayed in this article. The present study will add to the knowledge of control and operational strategies of CSTBRs.

The International Journal of Multiphysics, 2007

Direct contact condensation of steam injected into water is a special mode of condensation where ... more Direct contact condensation of steam injected into water is a special mode of condensation where condensation occurs on the interface between steam and water. Crucial in the modelling of direct contact condensation is the behaviour of the injected steam, commonly termed as a regime. Depending on the environmental conditions, steam injected into water appears in different regimes. These are observed in different geometrical appearances of the injected steam and are ranging from steam being condensed in the injector to bubbles and jets of steam formed in water. The two dimensional regime maps and models presently available are able to predict different condensation behaviour for limited range of flow conditions. In this paper a new three-dimensional condensation regime diagram is presented. The diagram is capable of predicting regimes for a wide range of flow conditions as well as different sizes of steam injector. Furthermore, expected penetration distance of steam injected into water, which is also crucial in modelling of the process, is presented for different flow conditions in the form of a new two-dimensional steam plume length diagram.

Emerging Technology in Fluids, Structures, and Fluid Structure Interactions: Volume 1, Fluid Dynamics and Fluid Structure Interactions, 2004

An analytical study to investigate small fire in a ventilated room is presented. Most existing st... more An analytical study to investigate small fire in a ventilated room is presented. Most existing studies are either numerical or experimental and correlations for predicting characteristics of flame propagation such as temperature difference, flame (plume) length and terminal velocity are based on empirical data. A simple mathematical -from the first principles- is developed to predict these characteristics. The predictions are compared with the published experimental data and good agreement has been obtained. Such a simple model would be very useful to practicing engineers for fire control programs, designing fire detection mechanisms.

Proceedings of the International Symposium on Innovative Materials for Processes in Energy Systems 2010, 2010

This paper critically examines the conventional design of the low temperature (up to 80°C) Proton... more This paper critically examines the conventional design of the low temperature (up to 80°C) Proton Exchange Membrane (PEM) fuel cell and a manufacturing design that does not depend on bi polar plates is presented. The fuel cell cost depends on the material and also on the complex manufacturing process. Materials that can be easily machined but still suitable in a fuel cell environment have been extensively researched and appropriately chosen. The design also incorporates greatly simplified manufacturing processes of the components. As a result the cost of the fuel cell can be driven down considerably. A series of tests were performed with a number of key operating parameters to provide vital performance data and to decide on the optimal operating conditions for the fuel cell. Comparisons were made with the published performance data of conventional PEM fuel cell to prove the design concept. It was observed that the proposed design performs comparatively better at higher current densities

Volume 4: Cycle Innovations; Electric Power; Industrial and Cogeneration; Manufacturing Materials and Metallurgy, 2006

Large scale electrical power generation faces two serious problems: (i) energy conservation; and ... more Large scale electrical power generation faces two serious problems: (i) energy conservation; and (ii) protection of the environment. High temperatures fuel cells have the potential to deal with both problems. The heat rejected by the fuel cell that would otherwise be wasted may be recovered to power a gas turbine in order to improve the energy conversion efficiency as well as power output of the combined fuel cell-gas turbine power plant. The added advantage of this approach would be to reduce thermal loading and the emission of greenhouse gases per MW electrical power generated. Serious research is being carried out worldwide to commercialise the fuel cell nevertheless there is still ample scope for studying the application of high temperature fuel cells in combination with the gas turbine for large scale electrical power generation. This paper presents the results of a parametric study of the fuel cell-gas turbine power plant to generate electricity. The paper should be of considerable interest to the designers and applications engineers working in power generation industry and other public utilities. The authors hope that the paper would lead to a stimulating discussion.Copyright © 2006 by ASME

Advanced Materials Research, 2014

Kazakhstan has intensive building construction program which offers an opportunity to construct e... more Kazakhstan has intensive building construction program which offers an opportunity to construct energy efficient buildings in the country and contribute towards global CO2 emissions targets. There are several energy efficient technologies and sustainable green design features available which construction industry can adopt. However, there are no proper guidelines on green or passive design features in the country. This paper outlines building design measures based on passive design principles specifically for cold climate and can be cost effectively used in Kazakhstan. It is shown that two basic and simple passive design strategies which include site selection, building orientation and proper insulation, can significantly reduce heating loads of a building and its overall energy consumption.

Wind Engineering, 2009

... Omar Badran1 Mamoun Janajrah2 Arne Holdo2 Andrew Lewis2 Raj Calay2 1 Professor, Department of... more ... Omar Badran1 Mamoun Janajrah2 Arne Holdo2 Andrew Lewis2 Raj Calay2 1 Professor, Department of Mechanical Engineering, Faculty of Engineering Technology, Al-Balqa` Applied University ... They noticed that the presence of wave groups was separated by calm regions. ...

Journal of Aircraft, 1997

ABSTRACT A series of wind-tunnel tests on a NACA 0012 airfoil was conducted to simulate the aerod... more ABSTRACT A series of wind-tunnel tests on a NACA 0012 airfoil was conducted to simulate the aerodynamic effects of runback ice. The drag and lift effects on the airfoil were assessed using wind-tunnel balance For three geometries of triangular section ice shapes at three different chordal positions, The results show a great degree of sensitivity of the aerodynamic flow characteristics to the shape and the chordal position of the ice accretion, and thereby highlight the need for realistic prediction models for runback ice.

International Journal of Vehicle Noise and Vibration, 2013

In this paper harvesting vibration energy from suspension is investigated. Theoretical values for... more In this paper harvesting vibration energy from suspension is investigated. Theoretical values for the harvested energy are calculated. Experimental evaluation of the energy is performed using vehicle road simulation facilities. An excitation signal in the frequency range of 0.5Hz to 20Hz is applied to the vehicle and the harvested power is calculated. Experimental results give a maximum harvested power of 984.4 W at the highest frequency, which is close to the theoretically computed value of 1106 W, for each suspension. Application of Regenerative Force Actuators (RFA) is explored for harvesting the vibration energy and controlling vibration. It is shown that the harvested power increases with the value of the actuator constant.

Energy Conversion and Management, 2008

The distribution of the stratified flow along and across the flow direction was investigated. The... more The distribution of the stratified flow along and across the flow direction was investigated. The effect of input airflow rates on the stratified flow was conducted. Also both effects of hot and cold airflow rate variations were studied. The flow rates studied were in the ranges of Q h = 1.0-5.0 m 3 /min for hot airflow, and Q c = 0.0-8.0 m 3 /min for cold airflow. These ranges could be useful for studying both stratified and mixed flow. It covers all ranges of Richardson number Ri (from 0.67 to 200). The higher of the input vertical location the higher of the interface level height, where different heights of input vertical locations will results in different levels of stratification. The using of warm jet is more effective, compared with the cold jet flow, because of the effect of bouncy variations on the stratified layer.

Applied Energy, 1993

Electromagnetic-heating processes are reviewed. Theoretical analyses of electromagnetic-heating p... more Electromagnetic-heating processes are reviewed. Theoretical analyses of electromagnetic-heating processes in isotropic materials of various regular geometries and with ranges of physical properties have been undertaken. The mathematical model so devised may be employed as a design tool in the development of a product/process and may thereby serve as a means for reducing the necessity for experimentation, which is usually expensive. In particular, the educational benefits of employing such a multi-purpose mathematical model, to improve the understanding of the thermal effects of electromagnetic-heating techniques, are emphasised.

The International Journal of Multiphysics, 2008

ABSTRACT Degradation in a homogeneous alluvial channel due to complete stoppage of sediment downs... more ABSTRACT Degradation in a homogeneous alluvial channel due to complete stoppage of sediment downstream of a high capacity reservoir has been studied empirically. Abased on dimensional analysis, a method has been established for predicting transient bed profiles in degrading alluvial stream. In addition, prediction procedures for other degradation elements like maximum degradation at any time at upstream section and degradation extent has also been evolved. The prediction procedures when tested against known data gave satisfactory results.

Applied Energy, 1996

two-phase flows in horizontal pipelines.

Journal of Hazardous Materials, 2008

Risk assessments related to industrial environments where gas is kept in liquid form under high p... more Risk assessments related to industrial environments where gas is kept in liquid form under high pressure rely on the results from predictive tools. Computational Fluid Dynamics (CFD) is one such predictive tool and it is currently used for a range of applications. One of the most challenging application areas is the simulation of multiphase flows resulting from a breach or leakage in a pressurised pipeline or a vessel containing liquefied gas. The present paper deals with the modelling of the post-flashing scenario of a jet emanating from a circular orifice. In addition to being based on the equations governing fluid flow, the models used are those related to turbulence, droplet transport, evaporation, break-up and coalescence. Some of these models are semi-empirical and based on the data from applications other than flashing. However, these are the only models that are currently available in commercial codes and that would be used by consulting engineers for the type of modelling discussed above, namely the dispersion of a flashing release. A method for calculating inlet boundary conditions after flashing is also presented and issues related to such calculations are discussed. The results from a number of CFD based studies are compared with available experimental results. The results show that whilst a number of features of the experimental results can be reproduced by the CFD model, there are also a number of important shortcomings. The shortcomings are highlighted and discussed. Finally, an optimum approach to modelling of this type is suggested and methods to overcome modelling difficulties are proposed.

Applied Thermal Engineering, 2008

This paper presents an experimental investigation of flow scenarios that lead to stratification w... more This paper presents an experimental investigation of flow scenarios that lead to stratification within the ventilated enclosures. The effect of supply terminal and extract terminal at various airflow rates on the flow characteristics is experimentally investigated. It has been found that relative influence of inertia and buoyancy forces resolves the stratified flow characteristics. The stratification interface level height and the ventilation flow rates are two main factors in the design of natural ventilation system. The results can be used to obtain a good estimation of the effectiveness of a ventilation system at design stage.

Applied Thermal Engineering

Rapid surface drying is an important and energy intensive process in food and beverage packaging ... more Rapid surface drying is an important and energy intensive process in food and beverage packaging industry. Usually these products are dried at low dew-point temperatures (DPT) À10 to À20 C and low dry ball temperatures (DBT) 20e30 C for product quality optimization. The conveyor moves at very high speeds and it is necessary to expose as much of the drying surface to the drying effect in a shortest time possible. Re-condensation is a big problem in these systems and a good drying system is that preserves the quality of the product and is energy efficient. This paper presents a feasibility study to obtain the design parameters of a hybrid dryer suited for rapid drying applications. Drying process of a re-circulation heat pump is integrated with rotary dehumidifier (desiccant wheel) system. The system employed a refrigerant circuit in conjunction with a heat reactivated desiccant wheel to provide efficient drying capability and supply low DPT conditions. To increase the economic practicality of such a hybrid system, the combined system utilises the heat dissipated by the condenser in regenerating the desiccant wheel. The study shows that the proposed hybrid system can deliver supply air at much lower DPT compared to the single refrigerant circuit and a desiccant wheel. By operating the combined system in tandem, greater amount of dehumidification could be realised due to the improved ratio of latent to total load at the hybrid. Up to 60% heat energy can be saved in rapid surface drying applications by using the proposed hybrid system.

The polymer electrolyte membrane (PEM) fuel cell is an ideal prime mover to replace the internal ... more The polymer electrolyte membrane (PEM) fuel cell is an ideal prime mover to replace the internal combustion engine, but there are two interrelated control problems that must be resolved before it can be accepted widely for automotive power trains. One is the matching of the fuel cell output power to the power required by the application; this involves control over the fuel cell. The second is the matching of the voltage and/or the current to the application requirements which involves the control of a power conditioning unit (PCU). Rapid variations of load that a fuel cell cannot meet because of its inherently low transient response are dealt with by means of an energy storage device (ESD). The response of fuel cells to transient variations in demand tends to be poor because it depends on the regulation of pressure and flow rates of air and hydrogen. In addition, it is necessary also to manage heat and water produced as a result of the electrochemical reaction. This paper deals with the complex problems of controlling a fuel cell system to deal with the steady state as well as transient variations of load and/or speed and describes a control strategy to deal with these issues.