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Concerns on the depletion of fossil fuel and emissions of harmful gases lead to the search for alternative aviation fuel. The present study demonstrates the production of biokerosene hydrocarbons from coconut oil via solvent-free catalytic deoxygenation under inert Nitrogen (N2) atmosphere. The deoxygenated product is examined through Gas Chromatography-Mass Spectrometry (GC-MS) analysis to determine its chemical composition and hydrocarbons distribution. CoO-NiO/Kaolin catalyst was used along with several other catalysts to study the reactivity of different catalysts in catalytic deoxygenation. Coconut oil is composed of middle-chain saturated fatty acids (capric acid, lauric acid, and myristic acid) which are favorable for the conversion into biokerosene hydrocarbons due to their carbon chain length. In terms of the types of catalyst, CoO-NiO/Kaolin proves to be the best catalyst with optimum selectivity of biokerosene hydrocarbons at 83.4%. A parametric study was executed on coconut oil using CoO-NiO/Kaolin, and the result indicated that the optimum reaction conditions are 330 oC, 2 hours of reaction time, and 5 wt.% of catalyst. The biokerosene hydrocarbons produced have the likelihood to be the drop-in substitutes for aviation fuel.

Temperature control is important in energy management of buildings. Air conditioning system contributes a high percentage of the total energy consumption, the compressor, which is a major component of the Air conditioning system, utilizes up to 90% of the energy. This can drastically be reduced by varying the frequency of the compressor with respect to the required indoor temperature, as such, reducing the overall energy usage of the air conditioning system. The combination of a well-tuned controller and variable frequency drive can be used to achieve this. It is important to develop a good model which can be used to design the controller. Although there are published research works in the development of models for the control of air conditioning systems, there seems to be a lack of study in the area of multi-circuit centralized air conditioning system. In this study, two models were developed using Long Short Term Memory Neural Network and Recurrent Neural Network, utilizing compressor speed and indoor air temperature of a multi-circuit water cooled packaged unit as input and output respectively. Comparing the two models, results shows that the Long Short-Term Memory Neural Network model performed better across evaluation metrics such as R-squared, Mean Squared Error and Mean Absolute Error, with the value of 0.9638, 0.0049, and 0.0190 respectively

Gasification technologies have the potential to produce clean and efficient energy sources. This technology is capable of producing synthesis gas from low or negative carbon -based raw materials such as coal, petroleum coke, high sulfur fuel oil, waste or waste materials and biomass. The gas produced from the process is used to replace natural gas to generate electrical power, or acts as basic raw material for producing chemicals and liquid fuels. Gasification is a process which utilizes heat, pressure, and steam to convert materials directly into gases, such as carbon monoxide and hydrogen gases. Despite differing in various aspects, gasification technologies have four common engineering factors such as atmospheric gasification reactors (oxygen or air content level), internal and external heating, reactor design and operating temperature. Raw materials, either in dry form or small granules, are fed into the reactor chamber called gasifier. Raw materials subjected to heat, pressure as well as an environment with rich or low oxygen content. Hydrocarbon gas (also known as Syngas), liquid hydrocarbon (oil) and coal (carbon black and ash) are the three main products of gasification. Syngas can be used as a fuel to produce electricity or steam, or acts as a basic block for various types of chemicals. When mixed with air, Syngas can be used in petrol or diesel engines with slight modifications to the engine.

The suitable application of innovative control strategies in Heating, Ventilation, and Air-conditioning systems is important to improving the energy efficiency and maintenance of temperature set point to improve thermal comfort in buildings. The increased focus on energy savings and appropriate thermal comfort has resulted in the necessity for more dynamic approach to the use of these controllers. However, the design of these controllers requires the use of an accurate dynamic modelling. Substantial progresses have been made in the past on model development to provide better control strategy to ensure energy savings without sacrificing thermal comfort and indoor air quality in the Heating, Ventilation, and Air-conditioning systems. However, there are scarce model using the data driven approach in the Multi-circuit air-conditioning system. This research, carried out a study on the choice of a dynamic model for an operating centralized multi-circuit water-cooled package unit air-conditioning system using a system identification procedure. Baseline data were collected and analyzed, the model development was achieved by processing, estimating and validating the data in system identification. Result shows that the Autoregressive-moving average with exogenous terms (ARMAX) of the third order model, established the best model structure with the highest Best Fit and Lowest Mean Square Error.

The present study has numerically investigated the Moderate or Intense Low oxygen Dilution (MILD) combustion regime, combustion processes and NO formation characteristics of the highly CO-rich syngas counterflow nonpremixed flames. To realistically predict the flame properties of the highly CO-rich syngas, the chemistry is represented by the modified GRI 3.0 mechanism. Computations are performed to precisely analyze the flame structure, NO formation rate, and EINO of each NO sub-mechanism. Numerical results reveal that the hydrogen enrichment and oxygen augmentation substantially influence the NO emission characteristics and the dominant NO production route in the CO-rich syngas nonpremixed flames under MILD and high temperature combustion regimes. It is found that the most dominant NO production routes are the NNH path for the lowest oxygen level (3%) and the thermal mechanism for the highest O2 condition (21%). For the intermediate oxygen level (9%), the most dominant NO production routes are the NNH route for the hydrogen fraction up to 5%, the CO2 path for the hydrogen fraction range from 5% to 10% and the thermal mechanism for the hydrogen fraction higher than 10%, respectively. To evaluate the contribution of the specific reaction on EINO the sensitivity coefficients are precisely analyzed for NO formation processes with the dominance of NNH/CO2/Thermal mechanism under the highly CO-rich syngas flames.

In this study, pure Jatropha oil (inedible plant oil) was converted into biodiesel (Jatropha Methyl-Ester or JME) through an esterification and trans-esterification process. It is then blended with commercial diesel in various ratios to produce four different blends. The ratio of Jatropha biodiesel to diesel (Jatropha:diesel) is 5:95% (B5), 10:90% (B10), 15:85% (B15) and 20:80% (B20). The letter B indicates the total volume of biodiesel in a mixture with diesel. Each batch of the fuel blend was then tested for their physical properties compared to diesel. Combustion performance tests were performed and temperature and emission (NOx and CO) profiles were measured at five different equivalence ratios. Experimental results are presented and they show that the temperature profile of each mixture does not exceed the value of diesel, and results in lower emissions (NOx and CO) than diesel.

Air-conditioning systems accounts for the highest portion of energy consumption in buildings, either commercial or residential. Thus, there is a need for energy savings while ensuring internal thermal comfort. The compressor utilizes about 90% of the energy being consumed by the air-conditioning system. Common practice in energy savings for air-conditioning systems includes the application of variable frequency drive of the compressor for capacity control. However, literature on capacity control for operational centralized multi-circuit systems are scarce. This paper presents a study on the application of a thermal control system known as the Advanced Thermal Control System or ATCS utilizing variable frequency drive technology on an installed and operational multi-circuit centralized water-cooled packaged unit air-conditioning system at an administration block in Universiti Teknologi Malaysia. The result shows energy savings of up to 33.0 % when compared to the baseline operation of the existing system.

Malaysia produces 0.5 tons of palm biodiesel per month, which has great potential to be transformed into valuable fuels for electricity generation by using a micro gas turbine (MGT). The MGT is an alternative power generation unit that is capable to generate the electricity in the range of 10 to above 50 Kilowatt. This unit comprises of automobile turbocharger with a combustion chamber connected in axial between its compressor and turbine. The MGT is able to achieve a maximum approximate temperature value, to 520 517.4°C by using diesel fuel. Next by using B20 Palm Methyl Ester (PME) a maximum approximate temperature is 500499.8°C, B15 Coconut Methyl Ester (CME) at 485.6°C and B30 Jatropha Methyl Ester (JME) at 439.7°C. The reduction percentage of biodiesel temperature at a maximum level compared to diesel was 11.4% for B30 JME, 6.1 % for B15 CME and 3.4 % for B20 PME. Significant aspect here, the knowledge about this reduction rate is established that can be help be help as a new technology in a future.

Depletion of fossil fuels, concerns on environment, and fuel price fluctuation have become the major drives in searching for sustainable alternative fuel. In that regard, a study was conducted to evaluate the combustion performance of Waste Cooking Oil (WCO) converted into biodiesel and blended with Conventional Diesel Fuel (CDF) as a mean of sustainable replacement for diesel fuel. In this study, the production of biodiesel fuel from waste cooking oil was done via transesterification process, using the single step approach. The properties of the WCO biodiesel was characterized. The combustion performance of the produced fuels has been studied for B10 and B30 biodiesel from WCO and CDF (as baseline) based on their wall temperature profiles and gaseous emissions generated such as nitrogen oxides (NOx), carbon monoxide (CO) and sulphur dioxide (SO2). It was found that the B30 WCO biodiesel emits lower emission compared to CDF but at the same time generates a lower temperature profile.

The increasing demand for clean and sustainable energy sources provides the impetus for the development of alternative fuels. Recent development of fuel-flexible gas turbine technologies enables the use of alternative non-fossil fuels that could play key roles in contributing to the global efforts in meeting emissions targets. This review highlights the current state-of-the-art production and properties of alternative fuels such as straight vegetable oil (SVO), biodiesel, bioethanol, bio-oil, hydrogenated vegetable oil (HVO) and Fischer-Tropsch (FT) fuel. This is followed by the evaluation of combustion performances in gas turbines. All of the alternative liquid biofuels have shown their potentials in reducing regulated emissions such as NOx, CO and soot under favourable operating conditions. Both HVO and FT fuels show comparable performance as that of jet fuel and can be used in aviation gas turbines, although the present day high production cost restricts the large-scale adoption, limiting its utility. They also have considerably higher cetane number than the rest, making it easier for the fuel to ignite. As for stationary power generation gas turbines that need not carry payloads, the other four alternative biofuels of biodiesel, bioethanol, bio-oil and SVO are possible candidates despite the physics-chemical properties variations when compared to fossil fuels. Amongst them, the use of SVO and bio-oil in gas turbines would require the parallel development of fuel supply systems and atomisation technologies to improve the combustion of the fuels. In all, the alternative liquid fuels reviewed provides realistic opportunities for cleaner and more sustainable operation of aviation and power generation gas turbines. Profound understanding on the fundamental combustion characteristics of the fuels are essential to expedite their mass adoption in gas turbine applications.

To have an optimum condition for the performance of a combined cycle power generation, using supplementary firing system after gas turbine was investigated by various researchers. Since the temperature of turbine exhaust is higher than auto-ignition temperature of the fuel in optimum condition, using flameless burner is modelled in this paper. Flameless burner is installed between gas turbine cycle and Rankine cycle of a combined cycle power plant which one end is connected to the outlet of gas turbine (as primary combustion oxidizer) and the other end opened to the heat recovery steam generator. Then, the exergoeconomic-environmental analysis of the proposed model is evaluated. Results demonstrate that efficiency of the combined cycle power plant increases about 6% and CO 2 emission reduces up to 5.63% in this proposed model. It is found that the variation in the cost is less than 1% due to the fact that a cost constraint is implemented to be equal or lower than the design point cost. Moreover, exergy of flow gases increases in all points except in heat recovery steam generator. Hence, available exergy for work production in both gas cycle and steam cycle will increase in new model.

Insufficient and various environmental issues of fossil fuels as the current world dominated energy is now becoming a serious global issue. The rapidly increasing demand for alternative energy sources has contributed to the steady growth of renewable energy. Owing to the fact of the abundant presence of palm kernel shell (PKS) as one of palm biomass wastes in South East Asia region, this paper investigates syngas produced from gasified PKS. The investigation is regarding its composition and combustion performance in a gas burner system. It covers emissions analysis, temperature profile and flame length. The produced syngas from downdraft gasifier was burned in the combustion chamber in air-rich and fuel-rich combustion conditions. From the experiment, the results showed that the oxidation zone temperature of above 750°C for the downdraft gasifier is suitable for producing syngas. Produced syngas can be classified as pure-carbon monoxide (CO) syngas due to 94.9% CO content with no hydrogen (H2) content and low heating value (LHV) of 10.7 MJ/kg. The wall temperature profiles for burnt syngas produced via downdraft gasification was higher with longer pattern at fuel-rich condition, which signified higher energy of syngas produced from downdraft gasifier compared to fluidised bed gasifier. The associated flame length was also longer at fuel-rich condition. Produced emission of 56 ppm NOX, 37 ppm CO and 1 ppm SO2 can still be considered as acceptable to human. It can be concluded that syngas produced from PKS shown a high potential to serve as an alternative source of energy due to its high energy content.

Genetic algorithm (GA) is widely accepted in energy systems optimization especially multi objective method. In multi objective method, a set of solutions called Pareto front is obtained. Due to random nature of GA, finding a unique and reproducible result is not an easy task for multi objective problems. Here we discuss the solution uniqueness, accuracy, Pareto convergence, dimension reduction topics and provide quantitative methodologies for the mentioned parameters. Firstly, Pareto frontier goodness and solution accuracy is introduced. Then the convergence of Pareto front is discussed and the related methodology is developed. By comparing two different best points (optimum points) selection method, it is shown that multi objective methods can be reduced to single objective or lower dimensions in objective functions by using ratio method. Our results establish that our proposed method can indeed provide unique solution of satisfactory accuracy and convergence for a multi-objective optimization problem in energy systems.

Synthesis gas, also known as syngas, produced from biomass materials has been identified as a potential source of renewable energy. Syngas is mainly consists of CO and H 2 , which can be used directly as fuel source for power generation and transport fuel, as well as feedstock for chemical production. Syngas is produced through biomass gasification process that converts solids to gas phase via thermochemical conversion reactions. This paper critically reviews the type of gasifiers that have been used for biomass gasification, including fixed bed, fluidized bed, entrained flow and transport reactor types. The advantages and limitations of these gasifiers are compared, followed by discussion on the key parameters that are critical for the optimum production of syngas. Depending on the biomass feedstock, the properties and characteristics of syngas produced can be varied. It is thus essential to thoroughly characterise the properties of biomass to understand the limitations in order to identify the suitable methods for gasification. This paper later focuses on a specific biomass – oil palm-based for syngas production in the context of Malaysia, where palm biomass is readily available in abundance. The properties and suitability for gasification of the major palm biomass, including empty fruit bunch, oil palm fronds and palm kernel shells are reviewed. Optimization of the gasification process can significantly improve the prospect of commercial syngas production.

This paper proposes a new methodology to provide a flexible optimum design tool for the multi-objective optimization of energy systems. There are many articles published on the optimization of energy systems, which use a multi-objective evolutionary algorithm for different cases. However a general method for optimization results utilization in design process is not presented to the authors’ knowledge and usually equilibrium point concept is used to select the optimal solution. Here a new method is proposed to improve the optimization results utilization in the design process. This method is applied on a simple energy system to consider the correlations between the design parameter and objective functions. The proposed method is flexible and easy to implement in any design problem. Results provide a neat process of optimum design includes cost limited maximum efficiency and components parameters selection like the condenser pressure and sub cool and superheat degrees. Results also show that compressor efficiency is the most powerful parameter in the case, which has the most significance effects on the optimization results.

Combustion characteristics of palm biodiesel/methyl esters (PME) and natural gas (NG) blend were examined using a model gas turbine swirl burner at vane angle (θ) 30°, 45° and 60°. A twin fluid air blast atomiser was utilised for atomising liquid fuel at air-to-liquid ratio (ALR) 2.50. Swirling flow was initiated by using an axial swirler as main air passed through it. Combustible mixture was formed as swirling air flow mixed up with liquid fuel spray at burner outlet. Flame colour for PME/NG was mainly bluish, resembling that of neat PME despite subtle liftoff was observed in PME/NG swirl flames. Flame spectroscopic analysis showed that PME/NG swirl flames were more intense than baseline PME. Furthermore, θ = 60° operation led to significantly lower reaction intensity. Meanwhile, PME/NG combustion with 20%-30% NG input power fraction was observed to lower nitric oxide (NO) emission by a factor of 2.7 when compared with diesel and neat PME in θ = 60° combustion. Novel empirical models for emissions were also proposed, enabling the estimation of NO emission from PME/NG combustion at different NG input power proportions and vane angle. This research shows that PME/NG combustion is a promising way of reducing NO emission against neat PME and diesel in gas turbine operation. Moreover, flame instability provoked by liftoff in dual fuel operation is not aggravated, mainly due to nullification by intensified global reaction when NG is added. Such attributes feature PME/NG as a viable alternative fuel for use in land-based power generation gas turbines.

The fossil fuels have been the most practical way to produce energy for industries, vehicles and homes due to their lower prices, good combustion properties and their availability compared to other types of fuels. However, in this era of modernization, one of the biggest challenges of humanity is depletion of fossil fuels may result the increasing of the price. Studies have found out that it is possible to improve physical and chemical characteristics of alternative fuel based biodiesel by using the transesterification process and hence act as an alternative to mineral diesel. Therefore, the study about the potentiality of the rice bran oil as biodiesel feedstock is explained in this paper. The aim of this study is determining the performance and emission characteristics of the rice bran oil biodiesel (RBOBD). In addition, the comparison is made for its combustion and emission characteristics to those of conventional diesel fuel (CDF). Results show that RBOBD is very good at minimizing emissions, especially CO and SO2 with the value 60 ppm and 10 ppm, respectively. The establish information may help Malaysia to recognize the potentiality of the rice bran oil in order to replace the conventional fuel in the future.

This paper presents an experimental investigation of the combustion characteristics of palm oil methyl ester (POME) or called as biodiesel (B), in an open-ended combustion chamber or called as open-ended liquid fuel burner. The performance of conventional diesel fuel (CDF) and various percentages of POME and CDF, which are B10 (10% biodiesel) and B30 (30% biodiesel) were studied to evaluate their performance. Combustion temperature profile in the combustion chamber and exhaust emission concentrations such as NOx, CO and SO2 have been carried out using five different equivalent ratios such as Φ = 0.6, 0.8, 1.0, 1.2 and 1.4. The results show that as the biodiesel content increased, the emission significantly increased except for the NOx emission. It was also found that higher biodiesel content resulting faster combustion rate at near burner region, especially for Φ = 1.0 due to higher Cetane Number (CN) although the lower overall temperature profile produced compared to CDF alone. This proved the suitability of biodiesel for an enhanced transportation engine performance in the near future.

It is well known that pregnancy is associated with frequent gastrointestinal (GI) disorders and symptoms. Moreover, previous reports have shown that estrogen, which changes in levels during pregnancy, participates in the regulation of GI motility and is involved in the pathogenesis of various functional disorders in the stomach. The aim of the current study was to explore the changes in the expression of estrogen receptors (ERs) and examine the effect of estrogen on nitric oxide- (NO-) cyclic guanosine monophosphate (cGMP) pathway and thus relaxation in gastric smooth muscle cells (GSMC) during pregnancy. Single GSMC from early-pregnant and late-pregnant Sprague-Dawley rats were used. Protein and mRNA expression levels of ERs were measured via specifically designed enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR), respectively. NO and cGMP levels were measured via specifically designed ELISA kits. Effect of estrogen on acetylcholine- (ACh-) induced contraction of single GSMC was measured via scanning micrometry in the presence or absence of the NO synthase inhibitor,N-nitro-L-arginine (L-NNA), or guanylyl cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ). Estrogen increased both NO and cGMP levels and their levels were greater in early compared to late pregnancy. Expression of ERs was greater in early compared to late pregnancy. ACh induced greater contraction of GSMC in late pregnancy compared to early pregnancy. Estrogen inhibited ACh-induced contraction in both periods of pregnancy. Importantly, pretreatment of GSMC with either L-NNA or ODQ abolished estrogen inhibitory action on muscle contraction. In conclusion, GSMC contractile behavior undergoes drastic changes in response to estrogen during pregnancy and this might explain some of the pregnancy-associated gastric disorders.

The spray combustion characteristics of coconut (CME), palm (PME) and soybean (SME) biodiesels/methyl esters were compared with diesel by using an axial swirl flame burner. Atomisation of the liquid fuels was achieved via an airblast-type nozzle with varied atomising air-to-liquid ratios (ALR) of 2–2.5. The fully developed sprays were mixed with strongly swirled air to form combustible mixtures prior to igniting at the burner outlet. Under fuel-lean condition, biodiesel spray flames exhibited bluish flame core without the yellowish sooty flame brush, indicating low sooting tendency as compared to baseline diesel. Increasing the atomising air led to the reduction of flame length but increase in flame intensity. Measurements of post-combustion emissions show that SME produced higher NO as compared to CME and PME due to higher degree of unsaturation, while the most saturated CME showed the lowest NO and CO emissions amongst the biodiesels tested across all equivalence ratios. By preheating the main swirl air to 250 °C, higher emissions of NO, CO and CO2 were observed for biodiesels. Higher ALR led to reduced NO and CO emissions regardless of the fuel used, making it a viable strategy to resolve the simultaneous NO CO reduction conundrum. This work shows that despite different emission characteristics exhibited by biodiesels produced from different feedstock, they are in principle potential supplemental fuels for practical combustion systems. The pollutants emitted can be mitigated by operating at higher ALR in a twin-fluid based swirl combustor.

Syngas from biomass residues is an alternative fuel to address the ever-increasing fossil fuel supply problem and the issue of releasing toxic gases from the fossil fuel burning process. Syngas is also a renewable fuel and features environmentally friendly fuel. This study was conducted to investigate the performance of the syngas produced from oil palm shells (PKS) using fluidized bed gasifier. In this study, the produced syngas was tested for its combustion performance from the aspect of gas combustion temperature and resulting emission concentrations such as nitrogen oxide (NOx), carbon monoxide (CO) and sulfur dioxide (SO2). The resulting syngas was studied at different ratio of air velocities to fuels. From the test, the ratio of velocity of air to fuel affects the gas combustion temperature and emission emission concentration. By increasing the air velocity to fuel ratio during the gasification process produces more positive effects primarily in improving the temperature of the gas burner combustion and reducing carbon monoxide (CO) emissions. However, the concentration of sulfur dioxide release (SO2) and nitrogen oxide (NOx) increase.

The concept of biodiesel as an alternative fuel is not an overnight thought, but the escalating prices, pungent emission gases and non-ecological behavior of fossil fuels has constrained the researchers to take the necessary steps. Biodiesels which are renewable in nature and having environmental friendly attribute have shown the potential to be the perfect replacement for the diesel fuels. Similarly, this study demonstrates the characteristics of Rice Bran Oil (RBO) which can be used as a latent substitute for diesel products. RBO is a vegetable oil, which is extracted from the rice bran (by-product of rice grain). Since rice is the staple diet for more than half of the world population, the quantity of RBO that can be extracted is enormous. In this study, the converted RBO into biodiesel (RBOBD) was blended with diesel to produce B5, B15 and B25 to determine physical properties and combustion performance. Owing to highly packed molecules of RBOBD, the properties such as density, kinematic viscosity and surface tension are higher in RBOBD and its blends than diesel. In contrast, the calorific value is lower. In the combustion test, the highest wall temperature is achieved at stoichiometric fuel mixture, while among the fuels, the wall temperature decreases as the biodiesel proportion increases in the blends. Moreover, in B25, emissions such as CO and SO2 are 68% and 50% lower than that of diesel respectively. However, due to the additional oxygen present in the biodiesel structure, NOx emission of B25 is 15.67% higher than diesel.

Emission from the combustion processes can cause adverse effect to the environment. The formation of pollutants such as oxides of nitrogen (NOx), carbon monoxide (CO), carbon dioxide (CO2) and oxides of sulphur (SOx) are hazardous and harmful to the ecosystem. Due to these pollutants and also depletion of fossil fuel, several steps should be taken in order to mitigate this problem. Biofuel is known as the potential replacement for fossil fuel. Envo Diesel is one form of biofuel that can be used on diesel engines and burner systems without any modification. It is produced by direct blending of palm oil with diesel fuel. This study was carried out to determine the performance of palm oil derived biofuel (Envo Diesel) on burner in terms of emission when applying staged air combustion. Emissions released from combustion chamber have been measured when applying the secondary staged air. The main purpose of this study was to determine the optimal blend for best performance compared to diesel when applying secondary air. Reductions of 67% and 54% can be achieved for NOx and SO2 respectively. Smaller reduction of around 21% was achieved for CO emission.

The heat transfer is a very interesting field for economical, functional and environmental reasons; it is almost related to each aspect of human lives. Therefor, the enhancement of such field is quite essential. Passive heat transfer represents is the soul of heat transfer enhancement due to the merits of simplicity, cheap and good enhancement with acceptable pressure drop. Corrugation is a method involved within the passive techniques of enhancement, it is important and being adopted in a wide range of applications like a nuclear reactor cooling, refrigeration, heat exchangers, and other industrial applications. The current article presents an extensive review of numerical and experimental studies on heat transfer enhancement, which covers the laminar and turbulent flow regions in the corrugations, especially in corrugated tubes. This paper dealt with 95.74% of papers published in corrugated tubes for different applications to offer one article representing a database stop for the designers and authors whom concerning and dealing with heat transfer enhancement in corrugated tubes.

This paper is presents numerical simulation of isothermal swirling turbulent flows in a combustion chamber of an unconfined burner. Isothermal flows of with three different swirl numbers, SN of axial swirler are considered to demonstrate the effect of flow axial velocity and tangential velocity to define the center recirculation zone. The swirler is used in the burner that significantly influences the flow pattern inside the combustion chamber. The inlet velocity, U0 is 30 m/s entering into the burner through the axial swirler that represents a high Reynolds number, Re to evaluate the differences of SN. The significance of center recirculation zone investigation affected by differences Re also has been carried out in order to define a good mixing of air and fuel. A numerical study of non-reacting flow into the burner region is performed using ANSYS Fluent. The Reynolds–Averaged Navier–Stokes (RANS) realizable k-ε turbulence approach method was applied with the eddy dissipation model. An attention is focused in the flow field behind the axial swirler downstream that determined by transverse flow field at different radial distance. The results of axial and tangential velocity were normalized with the U0. The velocity profiles’ behaviour are obviously changes after existing the swirler up to x/D = 0.3 plane. However, their flow patterns are similar for all SN after x/D = 0.3 plane towards the outlet of a burner.

Recently, the employing of corrugation for the enhancement of heat transfer has become interesting because it has the combined merits of extended surfaces, turbulators and roughness. Studies employing the use of both experimental and numerical techniques for the determination of thermal performance of spirally corrugated tubes for the flow of water at low Reynolds number are limited. Therefore, an experimental and numerical study for the flow of water at low Reynolds number in a spirally corrugated tubes was performed to determine the thermal performance of a new style of corrugation profile. The overall thermal performance was calculated for corrugated tubes, the numerical data of both Nusselt number and friction factor have been compared with the experimental data for standard smooth and corrugated tube. The results showed heat transfer enhancement range of 2.4–3.7 times of smooth tube with appreciable increase in the friction factor of 1.7–2.4 times of smooth tube. It observed and concluded that for long term and wide usage range, the tube of severity index value of 36.364×10 −3 has the best thermal performance of 1.8–3.4 at Reynolds number of 100–1300. This indicated that this geometry with a creative spiral corrugation profile can improve the heat transfer significantly with reasonable increase in friction factor.

Various techniques have been tested on heat transfer enhancement to upgrade the involving equipment, mainly in thermal transport devices. These techniques unveiled significant effects when utilized in heat exchangers. One of the most essential techniques used is the passive heat transfer technique. Corrugations represent a passive technique. In addition, it provides effective heat transfer enhancement because it combined the features of extended surfaces, turbulators and artificial roughness. Therefore, A Computational Fluid Dynamics was employed for water flowing at low Reynolds number in spiral corrugated tubes. This article aimed for the determination of the thermal performance of unique smooth corrugation profile. The Performance Evaluation Criteria were calculated for corrugated tubes, and the simulation results of both Nusselt number and friction factor were compared with those of standard plain and corrugated tubes for validation purposes. Results showed the best thermal performance range of 1.8–2.3 for the tube which has the severity of 45.455 × 10 −3 for Reynolds number range of 100–700. The heat transfer enhancement range was 21.684%–60.5402% with friction factor increase of 19.2–36.4%. This indicated that this creative corrugation can improve the heat transfer significantly with appreciably increasing friction factor.

In this paper, a RSORC (regenerative solar organic rankine cycle) is optimized. For this purpose, hourly analysis is considered and evaporator pressure, condenser pressure, refrigerant mass flow rate, number of solar panel (solar collector), storage capacity and regenerator effectiveness are selected as design parameters. Then RPGA (Real Parameter Genetic Algorithm) is used to find the maximum value of a new objective function named the RAB (relative annual benefit). The optimization is separately performed for three working fluids including R123, R245fa and isobutane. The optimization results reveal that the best studied working fluid is isobutane with 258810 $/year as relative annual benefit and follow by R245fa and R123 with 68173 and 64028 $/year as the RAB. The hourly analysis shows that in the optimum situation, a plant with isobutane as a working fluid produces higher electricity in the day hours while no electricity is produced in the night hours. Furthermore, a plant with isobutane needs the higher evaporator pressure, mass flow rate and number of solar panels with the lower condenser pressure, storage tank capacity and regenerator effectiveness compared with R245fa and R123. Finally the sensitivity analysis on simulation time step is performed and results are reported.

We demonstrate the use of laser induced incandescence (LII) of submicron tungsten carbide (WC) particles as a method for particle image velocimetry (PIV). The technique allows a single laser to be used for separate measurements of velocity of two phases in a droplet-laden flow. Submicron tungsten carbide (WC) particles are intentionally seeded into a two-phase flow, and heated by a light sheet generated by a double-pulsed PIV laser operating at sufficiently high pulse energy. The small size and large absorption cross-section allows particles to be heated up to several thousand degrees Kelvin to emit strong incandescence signals, whilst the laser-induced temperature increase in liquid droplets/large particles is negligible. The incandescence signal from WC and Mie scattering from droplets/large particles are separately captured by deploying different filters to a PIV camera. The consecutive images of the laser-induced incandescence (LII) are used to determine the velocity field of the gas-phase flow, and those of Mie scatter are used to extract the velocity of droplets/large particles. The proposed technique is demonstrated in an air jet first and compared with the result given by a normal PIV test, which shows that submicron WC particles can accurately follow the gas flow, and that the LII images can be used to perform cross-correlations. We then apply this technique on an ethanol droplet/air jet (non-reacting), demonstrating the resulting slip velocity between two phases. The proposed technique combining PIV and LII with a single laser requires little additional equipment, and is applicable to a much higher droplet/particle density than previously feasible. Finally the possibility of applying this technique to a flame is demonstrated and discussed.

A narrow path exists to a sustainable solution which passes through careful steps of efficiency improvement (resource management) and provides environmental friendly energies. Thermal power plants are more common in many power production sites around the world. Therefore, in this current research study a comprehensive thermodynamic modeling of a combined cycle power plant with dual pressure heat recovery steam generator is presented. Since the steam turbine outlet quality is a restrictive parameter, optimization of three cases with different steam quality are conducted and discussed. In other hand, energy and exergy analysis of each components for these three different cases estimated and compared. Obtained results show that it is really important to keep the quality of the vapor at turbine outlet constant in 88% for the results to be more realistic and also optimization and data are more technically feasible and applicable.

Optimal design of combined cooling, heating and power (CCHP) generation systems is presented in this paper. The goal of this study is comparison of a new operational strategy named variable electric cooling ratio (VER) with constant electric cooling ratio (CER) for different climates including hot, cold and moderate. In VER strategy, the share of absorption and electrical chillers supply load could vary during a year while in CER strategy it is constant. The gas engine is selected as prime mover and Particle Swarm Optimization (PSO) method is used to select the optimum CCHP equipments by maximizing the Relative Annual Benefit (RAB) as a new objective function. Optimization Results show that VER strategy, provides more benefit in comparison with CER strategy in all the studied climates. VER strategy shows 12.71%, 5.84% and 10.92% growth in optimum value of RAB in comparison with CER in the case of hot, cold and moderate climates, respectively. Furthermore, the optimum results demonstrate that a gas engine with higher nominal capacity is needed in VER compared with CER strategy. Results show that the VER strategy is a good alternative for following the cooling load in the CCHP operational strategy since it gives a good increment in RAB. Finally the optimum results of PSO algorithm is compared with Genetic Algorithm and differences are reported.

The main purpose of this article is to present the fluid dynamic and combustion performances of a can combustor applying double radial flow swirler. Analysis was conducted using Computational Fluid Dynamics simulation (CFD) and compared with experimental works conducted by previous researchers. Air pollution, in the form of gaseous emissions from gas turbine generator reportedly increasing every year. Design modifications was identified and used in this study where air swirler been proven able to reduce the formation rate of gaseous emission such as NOx and CO during combustion. Swirler in a burner is a device that serves to improve the air and fuel mixture in the main combustion zone. Swirlers, presently studied are from a combination of two radial swirlers with different vane angle (primary and secondary) such as 30o/40o, 30o/50o and 30o/60o. Application of Ansys Fluent 14 CFD solvers was used in this study. Turbulent flow model used was from Reynolds Average Navier-Stokes (RANS) type involving k-ϵ. The fuel used is diesel. The parameters studied were wall temperature distribution along the combustor, the volume of NOx and volume of CO in the main combustion zone. Results from this study showed that the combination of 30o/60o generates the lowest gaseous emissions production rate. The highest average percentage error obtained by simulation studies compared to the actual experimental values for NOx was 22% and CO was 17.8%. Comparison between simulation and actual study proves that the simulation method can be used for preliminary decision and able to be used as benchmark to determine which is the best swirler configuration.

In this study, thermodynamic modeling and exergoeconomic assessment of a Combined Cycle Power Plant (CCPP) with a Duct Burner (DB) was performed. Obtaining an optimum condition for the performance of a CCPP, using a DB after gas turbine was investigated by various researchers. DB is installed between gas turbine cycle and Rankine cycle of a CCPP to connect the gas turbine outlet to the Heat Recovery Steam Generator (HRSG) in order to produce steam for bottoming cycle. To find the irreversibility effect in each component of the bottoming cycle, a comprehensive parametric study is performed. In this regard, the effect of DB fuel flow rate on cost efficiency and economic of the bottoming cycle are investigated. To obtain a reasonable result, all the design parameters are kept constant while the DB fuel flow rate is varied. The results indicate that by increasing DB fuel flow rate, the investment cost and the efficiency of CCPP are increased. T-S diagram reveals that by using a DB, higher pressures steam in heat recovery steam generator has higher temperature while the low pressure is decreased. In addition, the exergy of flow gases in heat recovery steam generator increases. So, the exergy efficiency of the whole cycle was increased to around 6 percent, while the cost of the plant reduced by one percent.

Biodiesel as an alternative fuel is one of the best choices among other sources due to its immense potential to reduce pollutant emissions when used in compression ignition engines. Malaysia is considered one of the top biodiesel-producing countries. The main crop for biodiesel production is currently palm oil. However, Jatropha curcas has recently drawn the attention of the Malaysian government as an alternate species for producing high yields of oil. While an evaluation of biodiesel production, blending, engine performance and emissions characteristics of Malaysian-produced jatropha methyl ester has been made recently, few studies have optimized the esterification of the crude oil. This paper is the study of an optimization process for Malaysian CJO using an acid-catalyst pretreatment process to reduce the relatively high free fatty acid (FFA) percentages of crude jatropha oil to below 1% using design of experiments and response surface methodology, with the help of Minitab software. The main findings of the current investigation are that using the acid catalyst H2SO4 at 0.225% (v/v), an MeOH-to-oil ratio of 12.29% (w/w) and a reaction time of 149.76 min are the optimum process parameters for the esterification reaction.

The world is passing through a phase of sustainable modernization and industrial development day by day. As a result, there is an increasing number of vehicles used and heat engines demands in the market. However, energy sources used in these engines are limited and decreasing gradually. This situation leads to evolution of alternative sources to viable fuel for diesel engine. Biodiesel is seen as an alternative fuel for diesel engine combustion. The esters of vegetable or plant oil and animal fats are known as biodiesel. This article investigates the prospect of producing biodiesel from Jatropha oil. Jatropha curcas oil is a renewable non-edible plant. The seeds of Jatropha contain 50-60% oil. In this study, the oil has been converted to biodiesel by a well-known two-step, acid-base catalytic transesterification and used in diesel burner for performance evaluation. Biodiesel used in this study is a blend of diesel and Jatropha biodiesel. The performance of burner system using Jatropha biodiesel is based on its temperature profile and emissions generated such as nitrous oxide (NOx), sulphur dioxide (SO2) and carbon monoxide (CO). A reduction of 50% was achieved for both CO dan SO2 when burning Jatropha biodiesel compared to burning diesel.

Downdraft gasification is a potential method to produce biomass-based power suited for small-scaled power generation application. In the present study, a downdraft gasifier is used to gasify both raw and torrefied palm kernel shell (PKS). The properties of the palm kernel shells were characterised prior to gasification. Torrefaction of PKS was performed at the maximum temperature of 400 oC. Torrefied PKS shows lower moisture content by 4.8% as compared to raw kernel shell. Gasification of the feedstock showed that torrefied PKS produced higher amount of reactive syngas components, notably 16.4% CO and 9.25% H2 (by volume) than its raw counterpart. The total lower heating value of the syngas produced by torrefied PKS is 7.2 MJ/kg higher than that of raw PKS. Comparison of the temperature profiles within the gasifier for torrefied and raw PKS show distinct differences, with the temperature of the oxidation zone for raw and torrefied PKS being 1115oC and 1138oC at the equivalence ratio of 0.41 and 0.30, respectively. Although both feedstock show high potential for synthesis gas production, torrefied PKS produces syngas of higher LHV.

Synthesis gas (syngas) is a potential clean fuel for gas turbine. Experiments and numerical simulations were conducted to study the combustion characteristics of syngases in premixed swirl mode using a model gas turbine swirl burner. Four different types of syngases, covering low to high H 2 -content were tested. Experimental work was conducted to study the emission performance of lean swirl flame. Obtained results were used as validation targets for numerical simulation using flamelet generated manifold (FGM) and chemical equilibrium (CE) approaches. The former method shows better agreement with experimental result, hence FGM method was adopted to model flame structure and predict emission species in the reaction zones for different syngas types. Result shows that syngas with high concentration of H 2 produces lower peak flame temperature and height. Furthermore, high H 2 -rich syngas also produces low level of NO species in the reaction zone.

This paper presents an investigation on the combustion performance of different Coconut Methyl Ester (CME) biodiesel blends with Conventional Diesel Fuel (CDF) under B5 (5% CME, 95% CDF), B15 (15% CME, 85% CDF), and B25 (25% CME, 75% CDF) conditions. The performances of these fuels were evaluated based on the temperature profiles of the combustor wall and emission concentration of Oxides of Nitrogen (NOx), Sulphur Dioxide (SO2), and Carbon Monoxide (CO). The fuel properties of the CME biodiesel blends were measured and compared with CDF. All tested fuels were combusted using an open-ended combustion chamber at three different equivalence ratios, i.e., lean fuel to air mixture (Ф = 0.8), stoichiometry (Ф = 1.0), and rich fuel to air mixture (Ф =1.2), using a standard solid spray fuel nozzle. The results indicated that CME biodiesel blends combust at a lower temperature and produce less emission in comparison with CDF for all equivalence ratios. Moreover, the increase of CME content in biodiesel blends reduced the temperature of the combustor wall and the emission concentration. Results also proved that the utilization of biodiesel is beneficial to various industrial applications, especially in the transportation sector due to it being environmentally friendly, and serves as an alternative to petroleum diesel fuel.

This paper presents the effect of inserting swirler outlet orifice plate of different sizes at the exit plane of the radial air swirler in liquid fuel burner system. Tests were carried out with three different orifice plates with area ratios (orifice area to swirler exit area ratio) between 0.7 and 1.0 using 280 mm inside diameter combustor of 1000 mm length. Several tests were conducted using the commercial diesel as fuel. The fuel was injected at the back plate of the 45o vane angle swirler outlet using a central fuel injector with a single fuel nozzle pointing axially outwards. The aim of the insertion of orifice plates is to create the swirler pressure loss at the swirler outlet phase in order to maximise the swirler outlet shear layer turbulence to assist the fuel/air mixing. In the present work, the orifice plate with smaller area ratios exhibited very low NOX emissions for the whole operating equivalence ratios. The NOX reduction of more than 20 percent is achieved for orifice with 0.7 area ratio compared to 1.0 area ratio. Other emission such as carbon monoxide is increased with the decrease in the orifice area ratios. The results from this experiment show that good combustion is achieved by using smallest area ratios of orifice plate.

This research paper presents a study on a comprehensive thermodynamic modelling of a combined cycle power plant (CCPP). The effects of economic strategies and design parameters on the plant optimization are also studied. Exergoeconomic analysis is conducted in order to determine the cost of electricity and cost of exergy destruction. In addition, a comprehensive optimization study is performed to determine the optimal design parameters of the power plant. Next, the effects of economic parameters variations on the sustainability, carbon dioxide emission and fuel consumption of the plant are investigated and are presented for a typical combined cycle power plant. Therefore, the changes in economic parameters caused the balance between cash flows and fix costs of the plant changes at optimum point. Moreover, economic strategies greatly limited the maximum reasonable carbon emission and fuel consumption reduction. The results showed that by using the optimum values, the exergy efficiency increases for about 6%, while CO2 emission decreases by 5.63%. However, the variation in the cost was less than 1% due to the fact that a cost constraint was implemented. In addition, the sensitivity analysis for the optimization study was curtailed to be carried out; therefore, the optimization process and results to two important parameters are presented and discussed.

This research paper mainly deals with exergy, economic, and environmental investigation of a 250 MW steam power plant located in Iran. In order to model this power plant, energy balance equations are used and each part of the power plant is modeled accordingly. Further by introducing the boiler as the main source of irreversibility, two approaches are presented to improve the boiler performance, reduction of excess air, and temperature reduction of gasses leaving the stacks. To study the effect of these two approaches, an objective function including the cost rate of exergy destruction of boiler, fuel cost, and cost rate of environmental impact is presented. The optimization process is done using a genetic algorithm. It is concluded that by optimizing, 20% reduction in the overall cost rate and 88% reduction in the cost rate of environmental impact can be achieved.

In this research study, a combined cycle based on the Brayton power cycle and the ejector expansion refrigeration cycle is proposed. The proposed cycle can provide heating, cooling and power simultaneously. One of the benefits of such a system is to be driven by low temperature heat sources and using CO2 as working fluid. In order to enhance the understanding of the current work, a comprehensive parametric study and exergy analysis are conducted to determine the effects of the thermodynamic parameters on the system performance and the exergy destruction rate in the components. The suggested cycle can save the energy around 46% in comparison with a system producing cooling, power and hot water separately. On the other hand, to optimize a system to meet the load requirement, the surface area of the heat exchangers is determined and optimized. The results of this section can be used when a compact system is also an objective function. Along with a comprehensive parametric study and exergy analysis, a complete optimization study is carried out using a multi-objective evolutionary based genetic algorithm considering two different objective functions, heat exchangers size (to be minimized) and exergy efficiency (to be maximized). The Pareto front of the optimization problem and a correlation between exergy efficiency and total heat exchangers length is presented in order to predict the trend of optimized points. The suggested system can be a promising combined system for buildings and outland regions.

Combined cycle power plants (CCPPs) are preferred technology for electricity generation due to less emission and high efficiency. These cycles are made of a gas turbine, a steam turbine and Heat Recovery Steam Generator (HRSG). In the present research study, a combined cycle power plant with dual pressure and supplementary firing is selected. The optimum design procedure included designing objective function, exergy destruction per unit of inlet gas to the HRSG subject to a list of constraints. The design parameters (design variables) were drum pressure and pinch temperature difference as well as steam mass flow of HRSG high and low pressure levels. The influence of HRSG inlet gas temperature on the steam cycle efficiency is discussed. The result show increasing HRSG inlet gas temperature until 650 °C leads to increase the thermal efficiency and exergy efficiency of the cycle and after that has less improvement and start to decrease them. And also from the exergy analysis of each part of HRSG, it is cleared that the HP-EV and 2st HP-SH have the most exergy destruction respectively. In other hand, effects of HRSG inlet gas temperature on SI (sustainability index) and CO 2 emission are considered.

This paper presents an investigation on the combustion performance of an oil burner system utilising various Envo-diesel blends. Fuel used in this study is the blend of diesel with palm oil called Envo-Diesel. The experiment was conducted using E5, E10, E15, E20 and E25 as fuel. All fuel blends were investigated using two different types of nozzle with different fuel mass flow rates. The combustion performance of burner system using Envo-Diesel was based on its wall temperature profiles and emissions generated such as nitric oxide (NOx) and carbon monoxide (CO). The result for NOx at equivalent ratio 0.9 indicates that when the volume of palm oil increases in the blend compared to diesel, the emission decreased around 13% for E5. For CO emission at equivalent ratio 1.4, the percentage increment of palm oil volume in the blends compared to diesel caused decrease in CO emission of around 3% for E5. Results also show that the high content of palm oil in the blends increase the viscosity, surface tension and density, hence lower concentrations of emission.

Formation of nitrogen oxide (NOx), carbon monoxide (CO) and other emissions is increasing dramatically in the atmosphere. Due to this pressing issue, a study on combustion performance was conducted using a double radial swirler. In this study, a weak swirler with an angle of 30º is set as a primary swirler and strong swirlers each with an angle of 40º, 50º and 60º are set as secondary swirler. Combinations of these swirlers have increased internal recirculation of hot air and help to complete the mixing of fuel and air during combustion. Results show that the combination of 30º/60º swirler produced the best, more stable and shorter flame than the other combinations. Formation of NOX from the 30º/60º swirlers at equivalence ratio of 0.8333 is 27.3% lower than that from the combined 30º/40º swirlers. Other emissions such as CO, CO2 and UHC (Unburned Hydrocarbons) also show a reduction of 12.71%, 10.6% and 5.3%, respectively in the 30º/60º swirlers compared to those from the 30º/40º swirlers.

Combustion of liquid fuel sprays produces NOX, CO and other emissions that have an adverse impact on the environment and humans. This study is conducted to produce low-emission combustion with the use of double radial swirler. Swirling flow burning will enhance the mixing of fuel and air to produce a flame that is more stable and efficient. In this study, weak swirler with an angle of 30º is set as a primary swirler and strong swirlers each with an angle of 40º, 50º and 60º are set as the secondary swirler. Combinations of these swirlers helped the mixing of fuel and air during combustion. The results show, the combination of swirlers 30º/60º produced the highest temperature profile, the best flames, more stable and shorter than other combinations. NOX emissions for the combination of swirlers 30º/60º at stoichiometric are 15.6% lower than the combinations of swirlers 30º/40º. Other emissions such as CO, also shows 8.4% of reduction in the combination of swirlers 30º/60º. These results indicated that double swirlers helped in reducing emissions during combustion and also producing an environmentally friendly combustion system.

Jatropha oil derived from the Jatropha Curcas Linnaeus is one of the high potential plants to be use as bio-diesel. The purpose of this research is to carry out a feasibility study of using jatropha oil as bio-diesel on oil firing burner system. Like other bio-diesels, jatropha oil can also be used in any combustion engine and the performance and emissions such as NOx, SO2, CO and CO2 as well as unburned hydocarbon (UHC) from the engine will vary depending on the bio-diesel blends. The properties of Conventional Diesel Fuel (CDF) obtained will be used as baseline and the jatropha oil properties will be compared as well as other bio-diesels. From several researches, the properties of jatropha oil was found to be quite similar with other bio-diesel such as palm oil, neem, keranja and pongamia bio-diesel and complying with the ASTM standard for bio-diesel. Still, there are factors and issues concerning the use of jatropha oil such as technology, economy, legislation and resource. Plus, there several challeng...