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Showing papers on "Thermal efficiency published in 2016"


Journal ArticleDOI
TL;DR: The use of heat pipes can potentially reduce the thermal resistance and pressure losses in the system as well as temperature regulation of the TEGs and increased design flexibility as discussed by the authors, but heat pipes do have limitations such as maximum rates of heat transfer and temperature limits.

360 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the thermal efficiency enhancement of the commercial parabolic collector by increasing the convective heat transfer coefficient between the working fluid and the absorber, and showed that the use of nanofluids increases the collector efficiency by 4.25% while the geometry improvement increases the efficiency by4.55%.

320 citations


Journal ArticleDOI
TL;DR: This work focuses on quantum Otto engines and shows that when the working substance is at the verge of a second order phase transition diverging energy fluctuations can enable approaching the Carnot point without sacrificing power.
Abstract: Since its inception about two centuries ago thermodynamics has sparkled continuous interest and fundamental questions. According to the second law no heat engine can have an efficiency larger than Carnot’s efficiency. The latter can be achieved by the Carnot engine, which however ideally operates in infinite time, hence delivers null power. A currently open question is whether the Carnot efficiency can be achieved at finite power. Most of the previous works addressed this question within the Onsager matrix formalism of linear response theory. Here we pursue a different route based on finite-size-scaling theory. We focus on quantum Otto engines and show that when the working substance is at the verge of a second order phase transition diverging energy fluctuations can enable approaching the Carnot point without sacrificing power. The rate of such approach is dictated by the critical indices, thus showing the universal character of our analysis. The second law of thermodynamics says that the efficiency of a heat engine is limited by the Carnot efficiency. Here, the authors use finite-size-scaling theory to investigate whether this ultimate limit can be achieved at finite power using quantum Otto engines.

246 citations


Journal ArticleDOI
TL;DR: In this article, the feasibility of biodiesel produced from palm oil was investigated and the properties of blended fuel properties with increasing palm biodiesel ratio was evaluated to evaluate engine performance test results.

197 citations


Journal ArticleDOI
TL;DR: In this article, a flat and v-corrugated plate solar air heaters with built-in PCM as thermal energy storage material were designed and tested under prevailing weather conditions of Tanta city (30° 43′N, 31°E).

190 citations


Journal ArticleDOI
TL;DR: In this paper, a dynamic model of a hybrid photovoltaic/thermal (PVT) collector with a sheet-and-tube thermal absorber is presented to evaluate the annual generation of electrical energy along with the provision of domestic hot-water (DHW) from the thermal energy output, by using real climate data at high temporal resolution.

187 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of bioethanol fuel blends on spark ignition engine combustion characteristics (i.e., cylinder pressure, cylinder temperature, flame speed, combustion efficiency, combustion duration, heat release rate, knocking and cold start) are studied.
Abstract: Bioethanol fuel obtained from biomass and bioenergy crops has been proclaimed as one of the feasible alternative to gasoline fuel, as it is considered to be clean, renewable and green. In this review, the bioethanol production techniques from different lignocellulosic biomass, and its potential ethanol yield are studied. Moreover, this paper has reviewed the effects of bioethanol fuel blends on spark ignition engine combustion characteristics (i.e. cylinder pressure, cylinder temperature, flame speed, combustion efficiency, combustion duration, heat release rate, knocking and cold start); engine performance parameters (i.e. torque, brake power, brake specific fuel consumption, brake mean effective pressure, brake thermal efficiency and volumetric efficiency); and emission characteristics (i.e. carbon monoxide, oxides of nitrogen, carbon dioxide, unburned hydrocarbon and other unregulated emissions). Recently, many researchers produced bioethanol from herbaceous, industrial and municipal solid wastes (MSW) instead of agriculture and woody biomass. Most of the engine test results showed a remarkable improvement in engine performance and enhanced combustion characteristics for bioethanol fuel. In addition, the carbon monoxide and unburned hydrocarbon emissions decreased. Conversely, carbon dioxide and oxides of nitrogen emissions were not significantly reduced. Furthermore, there was no significant reduction of unregulated emissions, such as aromatics, acetaldehyde, and carbonyls.

175 citations


Journal ArticleDOI
01 Jan 2016-Energy
TL;DR: In this article, the authors present an innovative method for modeling energy hubs based on energy flow between its constituent elements, and an appropriate mixed integer nonlinear programming model is presented for short term 24-hour scheduling an energy hub, in which, the objective is to fulfill daily cooling, heating and electric demands of a hypothetical building with the maximum profit.

162 citations


Journal ArticleDOI
TL;DR: In this paper, a concentrating PV/T collector with fluid-based spectral splitting filter is developed, where the oleylamine solution of Cu9S5 nanoparticle is adopted in the filter to harvest the moderate-temperature heat.

161 citations


Journal ArticleDOI
15 Sep 2016-Energy
TL;DR: In this article, a subcritical and supercritical organic Rankine cycle (ORC) is designed to recover exhaust gas waste heat of biogas fuelled combined heat and power (CHP) engine.

147 citations


Journal ArticleDOI
TL;DR: In this paper, an air type single pass photovoltaic thermal (PV/T) collector system was proposed where a number of thin rectangular fins were introduced for heat dissipation.

Journal ArticleDOI
01 Dec 2016-Energy
TL;DR: In this article, the performance, emission and combustion characteristics of direct injection (DI) diesel engine fuelled with EEFO and its blends were investigated. But, the results showed that diesel engine performance was not significantly worse than B20 compared to B20.

Journal ArticleDOI
TL;DR: In this article, two promising techniques are investigated by a 1D approach with the aim of improving the fuel economy of a turbocharged SI engine at full load knock-limited operation.

Journal ArticleDOI
TL;DR: In this paper, the experimental analysis of a new biofuel feedstock as an alternative fuel that has not drawn much attention among the researchers is discussed about the experimental analyses of Cymbopogon flexuosus feedstock.

Journal ArticleDOI
01 Mar 2016-Fuel
TL;DR: In this paper, the effect of WCOME blending ratio on viscosity and sooting propensity of the biodiesel-diesel fuel mixture was investigated, and the engine performance was expressed in terms of the in-cylinder pressure data as well as the engine mechanical and environmental aspects measured at engine rated speed (1500 rpm) and different engine loads.

Journal ArticleDOI
TL;DR: In this article, a novel cycle combining three technologies of solid oxide fuel cell, micro gas turbine, and organic Rankine cycle is proposed to produce power in micro scale, and the results show that in micro-scale power generation, fuel saving of about 45% is achievable and the overall efficiency can reach more than 65%.

Journal ArticleDOI
TL;DR: In this article, the integration of both medium with the conventional photovoltaic thermal (PV/T) solar collector is presented, and the performance of the system is calculated based on Hottel-Whillier-Bliss equation.

Journal ArticleDOI
TL;DR: In this article, the effects of blending n-butanol and n-pentanol with biodiesel at 10% and 20% by volume on engine performance and on the physico-chemical characteristics of particulate emissions from a single cylinder, direct injection diesel engine.

Journal ArticleDOI
15 Nov 2016-Fuel
TL;DR: In this paper, an experimental investigation on the performance, combustion and emission characteristics of a port fuel-injection SI engine fueled with IBE-gasoline blends was carried out, and the IBE30 was selected to be compared with G100 under various equivalence ratio (Φ ǫ = 0.83-1) and engine load (300 and 500 kPa BMEP).

Journal ArticleDOI
TL;DR: In this paper, the performance of an idealized two-reservoir CO2 energy storage system under supercritical and transcritical conditions using a steady-state mathematical model was analyzed.

Journal ArticleDOI
15 Sep 2016-Energy
TL;DR: In this paper, a comparison of nine supercritical carbon dioxide (S-CO2) bottoming power cycles in conjunction with a topping cycle of landfill gas (LFG) fired 5MWe gas turbine is presented.

Journal ArticleDOI
15 May 2016-Energy
TL;DR: In this article, the applicability of the new fluid as drop-in replacement for R245fa in existing ORC systems and compares system parameters such as cycle efficiency and power output was analyzed.

Journal ArticleDOI
Gequn Shu1, Guopeng Yu1, Hua Tian1, Haiqiao Wei1, Xingyu Liang1, Huang Zhiyong1 
TL;DR: In this paper, a transcritical cascade-Organic Rankine Cycle (C-ORC) was proposed for recovering multi-grade waste heat from a typical heavy-duty diesel engine.

Journal ArticleDOI
TL;DR: In this paper, a multi-objective optimization on the solar-powered Stirling engine with high temperature differential was proposed based on the finite-time thermodynamic model and three well known decision making methods have been employed to specify the optimum values of the above mentioned parameters.

Journal ArticleDOI
TL;DR: In this paper, an experimental test was conducted on a single cylinder direct injection diesel engine to study the impact of oxygen enrichment on pollution and performance parameters by increasing the oxygen concentration of intake air from 21 to 27% by volume.

Journal ArticleDOI
TL;DR: In this article, the performance analysis of finned absorber solar air heater has been investigated analytically and the expression for collector efficiency factor of such collector has been developed and the effects of mass flow rates and fin spacings on the thermal performance have been presented and the results are compared with plain solar air heaters.

Journal ArticleDOI
01 Feb 2016-Energy
TL;DR: In this article, the authors focus on in-depth mathematical optimization analyses of ternary blends of diesel-butanol-vegetable oil (cotton oil), based on engine operating parameters using RSM (response surface methodology).

Journal ArticleDOI
01 Nov 2016-Energy
TL;DR: A hybrid photovoltaic-thermal (PVT) greenhouse solar dryer under forced mode has been proposed and different parameters have been evaluated for different climatic condition of Indian Institute of Technology, New Delhi (28_350 N, 77_120 E, 216 m above MSL), India as discussed by the authors.

Journal ArticleDOI
Gequn Shu1, Lingfeng Shi1, Hua Tian1, Xiaoya Li1, Guangdai Huang1, Liwen Chang1 
TL;DR: In this paper, an improved CTRC system containing both a preheater and regenerator (PR-CTRC) was introduced for recovering waste heat in exhaust gas and engine coolant of an engine, and compared its performance with that of the BCTRC system and also with the traditional excellent organic Rankine Cycle (ORC) systems using R123 as a working fluid.

Journal ArticleDOI
Gang Li1
TL;DR: In this article, the authors investigated the thermal efficiency, exegry destruction rate and mass flow rate under different ORC configurations and found that the ORC with internal heat exchanger (IHX) has a higher thermal efficiency than the baseline ORC.
Abstract: The utilization of low grade energy and renewable energy heat sources for power generation in organic Rankine cycle (ORC) system has received more attention in recent decades. In this study, working fluid candidates for various ORC applications based on the heat source temperature domains have been investigated for the thermal efficiency, exegry destruction rate and mass flow rate under different ORC configurations. The net power output from the ORC remains constant. The thermal efficiency increases as the condensing temperature diminishes, and decreases as the evaporating pressure recedes. As the condensing temperature and evaporating pressure are fixed, it can be found that as the critical temperature of the working fluid is increased, the thermal efficiency can be increased. As the heat source temperature scale increases, the operating evaporating pressure of the working fluids can be extended. The ORC with internal heat exchanger (IHX) has a higher thermal efficiency than the baseline ORC. The reheat ORC thermal efficiency is close to the baseline ORC. The regenerative ORC can achieve higher thermal efficiency than the baseline by reducing the addition of heat from the evaporator heat source. The performance of working fluid mass flow rate can reach their maximum in the low thermal efficiency region. The ORC with IHX and regenerative ORC have a lower value for exergy destruction as compared to baseline. Reheat ORC has a slightly higher exergy destruction rate. The evaporator is the largest contributor for the exergy destruction rate. In addition, the effect of IHX effectiveness, reheat pressure and regenerative intermediate pressure on system performance has been revealed and identified.