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Miller cycle is applied to improve performance and emission characteristics of a gas engine. There are different types of Miller cycle concept utilization through variation of valve timing either by early intake valve closure or late intake valve closure. In this study finite-volume method is used to analyse the performance and emission characteristics of a four-stroke 12-cylinder turbocharged Miller cycle gas engine. Therefore, experimental data are used to calibrate the results derived from 3D combustion simulation and 1D overall engine simulation. The Miller cycle application shows that about 30 CAD (crank angle degrees) advancement of IVC compared with standard cycle reduces emissions such as NO x to half its magnitude. However, a little reduction in power output seems inevitable. Also, compression ratio reduction contributes to almost 15% decrease in maximum in–cylinder pressure. Moreover, retardation of IVC simultaneously improves performance and emission characteristics. However, no significant change of in–cylinder peak pressure and temperature is seen. [ABSTRACT FROM AUTHOR]

The paper presents an innovative and advanced MCC (mixture controlled combustion). The MCC model is coupled to the innovative mechanistically based 0D spray model presented in a companion paper [1] that provides inputs on fuel mass distribution. Advanced MCC model is embedded into a 2-zone combustion modeling framework. Advanced MCC predicts ROHR (Rate-Of-Heat-Release) as the combination of the premixed and two diffusion parts, which correspond to rich and lean spray region. It also calculates the amount of fuel available for premixed combustion based on the duration of the ignition delay period. In addition, it reduces the reaction rate based on the oxygen availability using mechanistic basis, based on evaporation rate and based on mechanistically determined fuel amount that has reached the walls. High level of model predictability was confirmed by good agreement between the simulated and the measured ROHR traces over very broad operating range of the engine by using fixed parameters of the advanced MCC model and the spray model. Moreover, the applied modeling framework with embedded innovative spray and advanced MCC model features HiL (Hardware-in-the-Loop) compatible computational times. [ABSTRACT FROM AUTHOR]

The characteristics of the outwardly propagating premixed flames of stoichiometric mixtures of R134a/CH 4 /O 2 /N 2 have been experimentally investigated in a constant volume combustion chamber. Three regimes of the expanding flames were categorized based on the flame behavior. In the typical regime, a conventional outwardly propagating spherical flame was observed. The laminar burning velocity was correlated reasonably well as a function of the concentrations of oxygen and methane. When the concentration of R134a was relatively high, the buoyancy-induced regime, where the flame rises vertically while propagating outwardly, was observed. Phenomenological analysis in which the Richardson number and the Froude number were used to characterize the rising flames confirmed that the main cause of this phenomenon was buoyancy resulting from the difference between the densities of unburned and burned gases. The dimensionless velocity, which is based on the concept of the Damköhler number, explained the mechanism controlling the characteristic of the flame behavior. In addition, an intermediate transition regime existed between the two regimes. [ABSTRACT FROM AUTHOR]

In the present work, TS-TLBO (tutorial training and self learning inspired teaching-learning-based optimization) algorithm is proposed and investigated for the multi-objective optimization of a Stirling heat engine. The exploration and exploitation capacity of the basic MO-TLBO (multi objective teaching-learning-based optimization) is enhance by introducing the concept of tutorial training and self motivated learning. The multi-objective TS-TLBO algorithm uses a grid-based approach to adaptively assess the non-dominated solutions maintained in an external archive. Optimization of a Stirling heat engine is carried out by considering two and three objective functions simultaneously for the maximization of thermal efficiency, output power and minimization of total pressure drop of the engine. Application examples are presented to demonstrate the effectiveness and accuracy of the proposed algorithm. [ABSTRACT FROM AUTHOR]

The detailed axial temperature variations of the porous media burner during startup and switch-off processes were experimentally measured and analyzed for the premixed methane air combustion. A tubular burner filled by alumina pellets with diameters of 10 mm and 4.3 mm, respectively, was used as the porous media burner to study the effect of the burner inlet gas flow rate, equivalence ratio, and diameter of alumina pellets on the combustion temperature distribution along the burner axis and the combustion wave velocity. The results showed that the superadiabatic combustion could be achieved for the combustion wave velocity greater than zero, and the critical equivalence ratio corresponding to the superadiabatic combustion was bigger for the smaller pellet diameter or higher inlet air flow rate. This study can provide the useful information for the design and operation of the porous media burner, and is significant to understand the combustion phenomena in the porous media burner. [ABSTRACT FROM AUTHOR]

An original model for thermodynamic analysis of a batch type fluidized bed dryer is proposed herein considering two separate systems comprised of drying air medium as a control volume and particles to be dried as a control mass. By means of the proposed model, energetic and exergetic analyses of a drying column of a batch type fluidized bed dryer are carried out as an original contribution to literature since there is no such like model in which the analyses are performed considering two separate systems. The energetic efficiencies evaluated by means of the proposed model using the data in literature are compared with those in literature and a good conformity is satisfied with an acceptable error margin of ±9%. A new correlation is also developed with a mean deviation of ±10% in order to evaluate the energetic efficiency for not only corn drying process but also drying processes of other particles at inlet air temperature of 50 °C. Effects of air mass flow rate, mass of particle and ambient temperature on energetic and exergetic efficiencies are analyzed and some concluding remarks are highlighted for further studies. [ABSTRACT FROM AUTHOR]

Abstract: A systematic procedure is introduced for optimal design and evaluation of cogeneration systems based on the accurate cogeneration targeting model and the development of the R-curve concept through advanced exergetic, exergoeconomic and exergoenvironmental analyses. An advanced exergetic analysis makes this information more accurate and useful and supplies additional information that cannot be provided by the conventional analysis. Moreover, the new graphical representations are proposed based on new concept. Finally, the optimal design of Iran LNG cogeneration plant is performed, in which the usefulness of this method is clearly demonstrated. [Copyright &y& Elsevier]

Abstract: The nano air-bubbles mixed into gas oil are used for the energy saving and environmental load reduction of diesel engine. The nano air-bubbles were mixed into the fuel line continually by a super miniature ejector-type mixer (outer diameter: 20 mm, length: 34 mm) which can make nano and micro sizes. After the micro air-bubbles were separated with the nano air-bubbles in a mixing tank, diesel engine performance test with a common-rail injection system was experimented. The results showed that 3% reduction in break means specific fuel consumption, 1% rise in charging efficiency and a slight reduction in the density of exhaust smoke etc. These were caused by mixing the nano air-bubbles into gas oil. It is confirmed that the nano air-bubbles had advanced and activated combustion by a physical and chemical action. [Copyright &y& Elsevier]

Abstract: The aim of the present paper is to describe a general methodology suitable for analysing any intermediate configuration considered in staged vapour compression refrigeration cycles. This general methodology only depends on two basic parameters related to the subcooling and desuperheating obtained in the inter-stage system. A COP expression based on the two basic parameters was obtained from the general configuration. By means of its particularization to seven common configurations, it was then possible to make an energy comparison of the various configurations working with two fluids appropriated for the low temperature domain such as ammonia and R-404A. [Copyright &y& Elsevier]

Abstract: Thermoelectric power generation due to solar heating is a current interest in green energy research. One of the applications of the thermoelectric power generator is involved with the topping cycle, in which the thermoelectric generators were placed on the heat collector elements of a conventional solar concentration power plant. Although the topping cycle is practical and easy to operate, the efficiency of the thermal system with and without thermoelectric generator needs to be examined. In the present study, thermal efficiency of the topping cycle is analyzed and compared with its counterpart without the presence of the thermoelectric elements. Thermodynamic analysis for the efficiency of both the systems with and without thermoelectric generator is presented. The fluid flow and heat transfer in a tube with presence of thermoelectric elements resembling the solar heating system incorporated in the topping cycle are simulated numerically. It is found that, for a certain combination of operating and thermoelectric device parameters, thermal efficiency of the topping cycle becomes slightly higher than that of the same system without the presence of the thermoelectric generators. [Copyright &y& Elsevier]

Abstract: The direct-injection stratified charge (DISC) engine is a hybrid between spark ignition (SI) and compression-ignition engines, it combines many of the best features of both with some unique advantages of its own. This includes multi-fuel capability, high thermal efficiency, low NOx production, and low particulate emissions.This work shows how simple semi-global models can predict the performance of the SI and DISC engines with reasonable accuracy, without going to details of modeling for internal processes such as: swirl, mixing and detailed combustion kinetics.The operating variables studied were inlet manifold pressure pi, exhaust manifold pressure pe, engine speed N, equivalence ratio Φ, and volumetric efficiency ηv at different loads. The corresponding performance parameters were the brake mean effective pressure bmep, brake power Pb, and brake thermal efficiency ηb,th. The main contribution of this work is the production of friendly set of curve-fitting correlations for engine performance. The bmep and the Pb increase with the load for both engines. For spark ignition engines the bmep increases by about 70% when load increases from 50% to 100%. With the DISC engine, this ratio increases to 75%. The percent improvement in ηb,th for the DISC to the SI engine is around 50% which increases with part load, lower compression ratio rc and pi. [Copyright &y& Elsevier]

Abstract: In this paper the results from a in-depth life cycle analysis of production and use of a novel grid-connected photovoltaic micromorph system are presented and compared to other thin film and traditional crystalline silicon photovoltaic technologies. Among the new thin film technologies, the micromorph tandem junction appears to be one of the most promising devices from the industrial point of view. The analysis was based on actual production data given to the authors directly from the PRAMAC Swiss Company and it is consistent with the recommendations provided by the ISO norms and updates. The gross energy requirement, green house gas emissions and energy pay-back time have been calculated for the electric energy output virtually generated by the studied system in a lifetime period of 20 years. A comparative framework is also provided, wherein results obtained for the case study are compared with data from literature previously obtained for the best commercially available competing photovoltaic technologies. Results clearly show a significant decrease in gross energy requirement, in green house gas emissions and also a shorter energy pay-back time for the micromorph technology. [Copyright &y& Elsevier]

Abstract: In the present work, the generation of hydrogen rich synthetic gas from fluidized bed steam gasification of rice husk has been studied. An equilibrium model based on equilibrium constant and material balance has been developed to predict the gas compositions. The equilibrium gas compositions are compared with the experimental data of the present group as well as of available literature. The energy and exergy analysis of the process have been carried out by varying steam to biomass ratio (ψ) within the range between 0.1–1.5 and gasification temperature from 600 °C to 900 °C. It is observed that both the energy and exergy efficiencies are maximum at the CBP (carbon boundary point) though the hydrogen production increases beyond the CBP. The HHV (higher heating value) and the external energy input both continuously increase with ψ. However, the hydrogen production initially increases with increase in temperature up to 800 °C and then becomes nearly asymptotic. The HHV decreases rapidly with increase in temperature and energy input increases. Therefore, gasification in lower temperature region is observed to be economical in terms of a trade off between external energy input and HHV of the product gas. [Copyright &y& Elsevier]

Abstract: Steam injection technique is one of the most important methods for enhancing the heavy oil production. Evaluating the reliability of steam injection projects requires the investigation of the heat transfer in the wellbore and the surrounding formation. In this study, a new formation heat-transfer model taking into account the wellbore heat capacity was developed and a novel analytical transient heat-conduction time function was presented. Comparison of the formerly used transient heat-conduction time functions with the novel analytical transient heat-conduction time function was made. The result indicated that the wellbore heat capacity has a significant influence on the transient heat-conduction time function, especially for cases of short time injection. To investigate the effect of wellbore heat capacity on the heat transfer in steam injection wells, a comprehensive wellbore/formation model incorporating the novel analytical transient heat-conduction time function was also established. Based on this model, the wellbore/formation interface temperature and the wellbore heat losses were computed by using various transient heat-conduction time functions. The comparisons showed that the formerly used transient heat-conduction time functions would lead to inadequate estimation of the wellbore/formation interface temperature and the wellbore heat losses. High accuracy and excellent applicability of the wellbore/formation model were demonstrated when performances of the proposed model were compared with the measured field data from the steam injection well. [Copyright &y& Elsevier]

Abstract: Thermally activated systems based on sorption cycles, as well as mechanical systems based on vapor compression/expansion are assessed in this study for waste heat recovery applications. In particular, ammonia-water sorption cycles for cooling and mechanical work recovery, a heat transformer using lithium bromide-water as the working fluid pair to yield high temperature heat, and organic Rankine cycles using refrigerant R245fa for work recovery as well as versions directly coupled to a vapor compression cycle to yield cooling are analyzed with overall heat transfer conductances for heat exchangers that use similar approach temperature differences for each cycle. Two representative cases are considered, one for smaller-scale and lower temperature applications using waste heat at 60 °C, and the other for larger-scale and higher temperature waste heat at 120 °C. Comparative assessments of these cycles on the basis of efficiencies and system footprints guide the selection of waste heat recovery and upgrade systems for different applications and waste heat availabilities. Furthermore, these considerations are used to investigate four case studies for waste heat recovery for data centers, vehicles, and process plants, illustrating the utility and limitations of such solutions. The increased implementation of such waste heat recovery systems in a variety of applications will lead to decreased primary source inputs and sustainable energy utilization. [Copyright &y& Elsevier]

Abstract: In the present work, the entransy and entransy dissipation are defined from the thermodynamic point of view. It is shown that the entransy is a state variable and can be employed to describe the second law of thermodynamics. For heat conduction, a principle of minimum entransy dissipation is established based on the second law of thermodynamics in terms of entransy dissipation, which leads to the governing equation of the steady Fourier heat conduction without heat source. Furthermore, we derive the expressions of the entransy dissipation in duct flows and heat exchangers from the second law of thermodynamics, which paves the way for applications of the entransy dissipation theory in heat exchanger design. [Copyright &y& Elsevier]

Abstract: Within a gas/particle two-phase testing facility, multi-level concentrators were investigated by obtaining gas/particle two-phase characteristics of each concentrator within a centrally fuel-rich swirl burner. Measurements of velocities, particle volume flux profiles and relative particle number concentrations were obtained and analyzed to assess the performance of these concentrators. For concentrators with fewer levels, peak values of the axial particle volume flux were observed to move away from the central axis of the primary air duct. The rich/lean air ratios near the exit of the last ring were much larger for the single-level concentrator than for the 2- and 3-level concentrators. Conversely, the concentration ratio is always smaller for the single-level concentrator than for the others. In addition, the performance ratio RCR near the exit is always larger than 2, indicating that the 2- and 3-level concentrators can achieve a stable flame. The resistance coefficient increased with fewer rings making up the concentrator. [Copyright &y& Elsevier]

Abstract: This study proposes a model to investigate the behaviors of natural convective cooling of photovoltaic cells mounted discretely on the bottom wall of a horizontal cabinet. The effects of Rayleigh number (Ra), dimensionless length of cabinet (C x), ratio of cabinet wall to air thermal conductivities (Kef), number of photovoltaic cells (N), emissivity of metal wall (ε e), and emissivity of glass lens (ε g) are explored. Furthermore, the importance of thermal interaction between air streams inside and outside the cabinet through conducting wall are examined. The numerical computation domain covers the cabinet and surrounding area, so that the temperature and velocity fields of the combined regions are solved simultaneously. Results show that temperature differences among the photovoltaic cells can be up to 28% for all the investigated cases when 106 ≦ Ra ≦ 108, 5 ≦ C x ≦ 12.5, 4 ≦ N ≦ 10, 1000 ≦ K ef ≦ 6300, 0 ≦ ε e ≦ 0.5 and 0 ≦ ε g ≦ 0.94. The maximum difference in hot spot temperatures of photovoltaic cells is about 26% among the cases with various K ef. In addition, the temperatures are rather low for the situation without consideration of thermal interaction between the air streams inside and outside the cabinet. Therefore, without the consideration of the thermal interaction would cause serious under-prediction for the hot spot temperatures of photovoltaic cells in engineering applications. [Copyright &y& Elsevier]

Abstract: This study experimentally examined a cylindrical multi-hole premixed burner for its potential use for a condensing gas boiler, which produces less NOx emissions and performs better. In this study, the hole diameters and the arrangement of a multi-hole burner were investigated using a flat burner model. The combustion characteristics for the flame stability as well as the NOx and CO emissions were examined using a cylindrical burner. For an optimal operating condition, the equivalence ratio for the cylindrical burner was between 0.70 and 0.75. For this condition, the turn-down ratio was 3:1 or higher, which was suitable for appropriate control of the boiler operation. The NOx and CO emissions were less than 40 ppm and less than 30 ppm, respectively, for a 0% O2 basis. The LPG and LNG were able to be used in this type of burner because there was no phenomenal difference in the stable combustion region between them. [Copyright &y& Elsevier]

Abstract: Exergoeconomic formulations and procedure including exergy flows and cost formation and allocation within a high temperature steam electrolysis (HTSE) system are developed, and applied at three environmental temperatures. The cost accounting procedure is based on the specific exergy costing (SPECO) methodology. Exergy based cost-balance equations are obtained by fuel and product approach. Cost allocations in the system are obtained and effect of the second-law efficiency on exergetic cost parameters is investigated. The capital investment cost, the operating and maintenance costs and the total cost of the system are determined to be 422.2, 2.04, and 424.3 €/kWh, respectively. The specific unit exergetic costs of the power input to the system are 0.0895, 0.0702, and 0.0645 €/kWh at the environmental temperatures of 25°C, 11°C, and −1°C, respectively. The exergetic costs of steam are 0.000509, 0.000544, and 0.000574 €/kWh at the same environmental temperatures, respectively. The amount of energy consumption for the production of one kg hydrogen is obtained as 133kWh (112.5kWh power+20.5kWh steam), and this corresponds to a hydrogen cost of 1.6€/kgH2. [Copyright &y& Elsevier]

Abstract: Significant energy efficiency gains in zones with concentrated activity from energy intensive industries can often be achieved by recovering and reusing waste heat between processing plants. We present a systematic approach to target waste heat recovery potentials and design optimal reuse options across plants in industrial zones. The approach first establishes available waste heat qualities and reuse feasibilities considering distances between individual plants. A targeting optimization problem is solved to establish the maximum possible waste heat recovery for the industrial zone. Then, a design optimization problem is solved to identify concrete waste heat recovery options considering economic objectives. The paper describes the approach and illustrates its application with a case study. [Copyright &y& Elsevier]

Abstract: This paper is concerned with heat transfer analysis and life prediction in the after shell section of a gas turbine combustion liner with internal cooling passage. The method in the present study is the process to design cooling systems which enhance the material lifetime as well as the cooling performance. Using this method, we found the major causes of lifetime-affecting thermal damage induced by heat transfer distributions in the internal cooling system of the after shell section. From startup to shutdown, high thermal deformation occurred between the hot and coolant side walls in the welding region, the nearby cooling hole, and above the divider of the C-channel. Three regions were therefore very weak in relation to the thermal cycle. Moreover, these locations were in close agreement with the locations of thermal cracks in an actual gas turbine combustor currently in service. [Copyright &y& Elsevier]

Abstract: In any energy system that produces work, heat and so on, disposal remaining flows of matter or energy, which are called residues, will appear. In the exergoeconomic analysis of these systems, one of the complex problems is residues cost allocation in a rational way. Two more important criteria of the residues cost allocation are distribution of the cost of the residues proportional to the exergy as well as proportional to the entropy generation or negentropy. In this paper, a new criterion for the residues cost allocation is proposed that it is based on the entropy distributed in the components, and not on the entropy generated along the process. This new criterion uses the fuel–product (FP) table, a mathematical representation of the thermoeconomic model, as input data. The important characteristic of this new criterion is the use of a new FP table ( table) which is constructed using energy and exergy of flows. The proposed criterion is applied to a combined cycle and results are compared with the two other criteria. Results show that this criterion is more suitable and rational than the two other criteria. [Copyright &y& Elsevier]

Abstract: In order to clarify variability in wind energy over a long-term period of 30 years, an investigation was carried out on Jeju Island in South Korea, which has complex terrain. The selected areas for this study were Jeju, Seogwipo and Seongsan, which have wind data for 30 years from 1978 to 2007. The long-term wind data measured from automated synoptic observation system (ASOS) of meteorological observatories was analyzed in accordance with inter-annual, annual and diurnal time scales. Wind variations in various time scales were quantified by both the coefficient of variation and the range of variation. As a result, the yearly average wind speed tended to slightly decrease at the Jeju site, while the other two sites have random trends. The regional deviation for wind variations was significant on Jeju Island, which may result from its complex terrain. It was found that when wind data is measured and analyzed over a longer-term period, more reliable results can be obtained. Besides these, a statistically meaningful result will be presented in this paper. [Copyright &y& Elsevier]

Abstract: Thermal insulation is one of the most effective energy-conservation measures in buildings. For this reason, the energy savings can be obtained by using proper thickness of insulation in buildings. In this study, the optimum thickness of insulation considering condensed vapor in external walls are found by using exergoeconomic analysis. The four various cities from four climate zones of Turkey, namely, Antalya, İstanbul, Elazığ and Erzurum are selected for the analysis. The optimum insulation thickness for Antalya, İstanbul, Elazığ and Erzurum are obtained as 0.038, 0.046, 0.057 and 0.0739m at indoor temperature of 20°C, respectively. The results show that the optimum insulation thickness at the indoor temperature of 18 and 22°C are determined as 0.0663 and 0.0816m for the city of Erzurum, respectively. The energy saving for the city of Erzurum is found as 77.2% for the indoor temperature of 18°C, 79.0% for the indoor temperature of 20°C and 80.6% for the indoor temperature of 22°C, when the optimum insulation is applied. [Copyright &y& Elsevier]

Abstract: This paper is concerned with the energy and exergy analyses of the thin layer drying process of mulberry via forced solar dryer. Using the first law of thermodynamics, energy analysis was carried out to estimate the ratios of energy utilization and the amounts of energy gain from the solar air collector. However, exergy analysis was accomplished to determine exergy losses during the drying process by applying the second law of thermodynamics. The drying experiments were conducted at different five drying mass flow rate varied between 0.014 kg/s and 0.036 kg/s. The effects of inlet air velocity and drying time on both energy and exergy were studied. The main values of energy utilization ratio were found to be as 55.2%, 32.19%, 29.2%, 21.5% and 20.5% for the five different drying mass flow rate ranged between 0.014 kg/s and 0.036 kg/s. The main values of exergy loss were found to be as 10.82 W, 6.41 W, 4.92 W, 4.06 W and 2.65 W with the drying mass flow rate varied between 0.014 kg/s and 0.036 kg/s. It was concluded that both energy utilization ratio and exergy loss decreased with increasing drying mass flow rate while the exergetic efficiency increased. [Copyright &y& Elsevier]

Abstract: Our physical environment is endowed with unlimited amount of natural and artificial sources of energy at various low exergetic levels which leaves them almost impossible to be thermally utilized at such source states. The thermal upgrading of these low exergetic energy sources could render them amenable to various practical thermal usages. This paper provides a comparative study through simulations, of the effectiveness, robustness and reliability of the often two most promising heat upgrading technologies (the chemical and mechanical heat pumps) systems for the sustainable heat upgrading of low-temperature heat sources for district heating. The simulation results reveal that for a low to medium energy demand, low-temperature heat source upgrading using the chemical heat pumps seems more promising than the mechanical heat pumps, while the mechanical heat pump is best suited for high energy demand space heating. In the simulation, use was made of an artificial low-temperature heat source (a nearby pharmaceutical industry waste heat) with source temperature state of between 25 and 35°C as the feed to the upgrading units. The high energy demand (assumed to be able to serve the space heating energy requirements of a given locality) was estimated to be 923TJ/annum at a consumer-side temperature level of about 95°C. The selected most robust system (the mechanical heat pump-based process) for upgrading the low-temperature heat source at such given high energy demand has been conceptually designed. [Copyright &y& Elsevier]