Exhaust Heat Research Articles

Cooling Cyclic Air of Marine Engine with Water-Fuel Emulsion Combustion by Exhaust Heat Recovery Chiller

The fuel efficiency of marine diesel engine as any combustion engine falls with raising the temperature of air at the suction of its turbocharger. Therefore, cooling the engine turbocharger intake air by recovering exhaust gas heat to refrigeration capacity is a very perspective trend in enhancing the fuel efficiency of marine diesel engines. The application of water-fuel emulsion (WFE) combustion enables the reduction of a low-temperature corrosion, and, as a result, provides deeper exhaust gas heat utilization in the exhaust gas boiler (EGB) to the much lower temperature of 90–110 °C during WFE instead of 150–170 °C when combusting conventional fuel oil. This leads to the increment of the heat extracted from exhaust gas that is converted to refrigeration capacity by exhaust heat recovery chiller for cooling engine turbocharger sucked air accordingly. We experimentally investigated the corrosion processes on the condensation surfaces of EGB during WFE combustion to approve their intensity suppression and the possibility of deeper exhaust gas heat utilization. The fuel efficiency of cooling intake air at the suction of engine turbocharger with WFE combustion by exhaust heat recovery chiller was estimated along the voyage line Mariupol–Amsterdam–Mariupol. The values of available refrigeration capacity of exhaust heat recovery chiller, engine turbocharger sacked air temperature drop, and corresponding reduction in specific fuel consumption of the main low-speed diesel engine at varying actual climatic conditions on the voyage line were evaluated.

Modeling and performance analysis of diesel engine considering the heating effect of blow-by on cylinder intake gas

Recently, the stringent international regulations on ship energy efficiency and NOx emissions from ocean-going ships make energy conservation and emission reduction be the theme of the shipping industry. Due to its fuel economy and reliability, most large commercial vessels are propelled by a low-speed two-stroke marine diesel engine, which consumes most of the fuel in the ship. In the present work, a zero-dimensional model is developed, which considers the blow-by, exhaust gas bypass, gas exchange, turbocharger, and heat transfer. Meanwhile, the model is improved by considering the heating effect of the blow-by gas on the intake gas. The proposed model is applied to a MAN B&W low-speed two-stroke marine diesel engine and validated with the engine shop test data. The simulation results are in good agreement with the experimental results. The accuracy of the model is greatly improved after considering the heating effect of blow-by gas. The model accuracy of most parameters has been improved from within 5% to within 2%, by considering the heating effect of blow-by gas. Finally, the influence of blow-by area change on engine performance is analyzed with considering and without considering the heating effect of blow-by.

Performance enhancement of methanol reforming reactor through finned surfaces and diffused entry for on-board hydrogen generation

Hydrogen-rich combustion in engines helps in reducing pollutants significantly. But hydrogen usage on a moving vehicle is not getting large-scale user acceptance mainly due to its poor energy storage density resulting in shorter driving ranges. This storage issue led to the hunt for mediums that can efficiently produce on-board hydrogen. Methanol proves to be an efficient alcohol fuel for producing hydrogen through steam reforming reaction. The heat energy required for such endothermic reaction is obtained through exhaust engine waste energy and this process is collectively known as thermochemical recuperation. However, the conventional reactor used for this process faces a lot of problems in terms of efficiency and methanol conversion. In this study, an attempt has been made to improve the design of the reactor for on-board hydrogen generation using engine exhaust heat for addressing the challenges related to performance and hydrogen yield. For enhancing the heat transfer, a finned surface (straight & wavy) was introduced in the reactor which resulted in an increment in methanol conversion significantly. It was found that wavy fin improved the methanol conversion up to 96.8% at an exhaust inlet temperature of 673 K. Also, a diffusing inlet section was introduced to increase the residence time of reactant gases while passing through the catalyst zone. Under given inlet conditions, the methanol conversion for 6° diffuse inlet reactor goes up to 87.9% as compared to 75.4% for the conventional reactor.

The impact of the technical requirements of the renovation grant on the ventilation and indoor air quality in apartment buildings

In this study, the impact of ventilation requirements set in the conditions of a renovation grant was analysed with field measurements. Effects of renovation measures applied in two grant periods on the air change rate (ACR) and indoor air quality (IAQ) of apartments were examined. CO2 levels and airflow rates were measured in 21 buildings during the first renovation grant period and in 15 buildings in the second grant period. During the first grant period, the average ACR studied apartments was as low as 0.17 h−1, and in the second grant period ACR had improved to 0.57 h−1, complying with requirements. Room-based ventilation requirements as well as heat recovery and preheating of intake air, mandatory airflow rate and sound pressure level measurement protocols, and third party inspection of design documentation assured adequate ventilation and IAQ in the second grant period. Centralized mechanical supply and exhaust ventilation with heat recovery resulted in best performance but an alternative system with exhaust heat pump and ventilation radiators may also be recommended. We concluded, that the installation of proper ventilation system is a key issue in renovation. The results of the study are a valuable input in designing technical conditions of the renovation grant.

Electronic structure tuning of α-SrSi2 by isotropic strain and isoelectronic impurity incorporation: A first-principles study for enhancement of low-temperature thermoelectric performance

Interest in thermoelectric (TE) materials has revived in recent years because TE materials realize not only the utilization of distributed unused thermal energy, such as exhaust heat from automobiles and factories and solar heat, but also cold power generators and self-power supplies for wireless sensors. However, because the bandgap of low-temperature TE materials is relatively small, the precise calculation of its physical properties is difficult to achieve by first-principles calculations based on conventional density functional theory. The present study investigates the effects of isotropic strain and incorporation of isoelectronic impurities on the TE transport properties of extremely narrow-gap semiconducting α-SrSi2. By adopting the Gaussian–Perdew–Burke–Ernzerhof hybrid functional, the analysis clarifies the relationship between the lattice distortion and the electronic structure in α-Sr4–xAxBySi8–y (A = Mg, Ca, or Ba; B = C, Ge, Sn, or Pb) and elucidates the TE transport properties. In particular, an irregular bandgap expansion was observed in α-Sr4CSi7, suggesting that the TE performance can be maximized by appropriate tuning of the carrier concentration.

Experimental performance evaluation and comparison of an absorption refrigeration prototype driven by exhaust heat operating with NH3/LiNO3 and NH3/LiNO3+H2O

Ammonia/salt absorption refrigeration cycle has advantages of low grade heat recovery, excellent thermal performance and simple construction, which may play an important role in refrigeration and air-conditioning fields for energy saving and emission reduction. The present paper introduces a prototype of absorption refrigeration system driven by exhaust heat operating with NH3/LiNO3 and NH3/LiNO3+H2O, which is composed of commonly used devices with the advantages of low cost and simple manufacture. Comprehensive experiments on the prototype were carried out with varying operating conditions (exhaust-gas temperature, chilled-water temperature, cooling-water temperature) to evaluate their influences on performance parameters. The NH3/LiNO3 system was driven by gaseous exhaust heat in the range of 150.1 °C∼325.1 °C, the minimum evaporating temperature reached -25.29 °C, the cooling capacities varied between 0.60 kW and 3.00 W, the electrical coefficient of performance varied between 3.30 and 16.52, and the overall coefficient of performance varied between 0.263 and 0.584. The NH3/LiNO3+H2O system was driven in the range of 125.8 °C∼330.1 °C, the minimum evaporating temperature reached -22.56 °C, the cooling capacities varied between 0.92 kW and 3.91 kW, the electrical coefficient of performance varied between 4.65 and 20.30, and the overall coefficient of performance varied between 0.310 and 0.566. The experimental results were compared with that of NH3/NaSCN system by authors’ previous work, it is found that three ammonia/salt working fluids have respective advantages and optimal working condition ranges. The experimental evaluation and comparison provide significant references for the optimization and practical application of the ammonia/salt absorption refrigeration systems.

Using two novel integrated systems to cool the air toward the ISO condition at the gas turbine inlet

The gas turbine performance is heavily influenced by climate conditions. The more the temperature of the air coming into the compressor, the less the thermal efficiency of the gas turbine will be. The best performance of the gas turbines is achieved in ISO condition (15 °C RH 100%). In selecting a cooling system in this ground, features such as insensitivity to the ambient air and ability to use the heat recovered from the gas turbine give absorption chillers distinct advantages over Maisotsenko, evaporative and fogging systems. However, in hot and humid climates, in order for the air to be cooled toward the ISO condition, there is a need for significant cooling capacity of absorption chillers, which imposes additional expenses such as operational, maintenance and. etc. In this study, two new integrated cooling systems are presented as AMD and AED consisting of absorption chiller, desiccant wheel, Maisotsenko cooler (or evaporative cooler) simultaneously. In these integrated cooling systems, not only is the air cooled down to ISO condition, but also the required cooling capacity of the absorption chillers is significantly reduced. It is worth mentioning that in the novel systems, exhaust heat from the gas turbine is employed to both operate absorption chillers and regenerate desiccant wheel. In addition, the water condensed by absorption chillers supplies the portion of water consumed by the Maisotsenko or the evaporative cooler.

Diesel generator exhaust heat recovery fully-coupled with intake air heating for off-grid mining operations: An experimental, numerical, and analytical evaluation

The customarily discarded exhaust from the fossil fuel-based power plants of the off-grid mines holds the thermal potential to fulfill the heating requirement of the underground operation. This present research fills in an important research gap by investigating the coupling effect between a diesel exhaust heat recovery and an intake air heating system employed in a remote mine. An integrative approach comprising analytical, numerical, and experimental assessment has been adapted. The novel analytical model developed here establishes the reliability of the proposed mine heating system by providing comparative analysis between a coupled and a decoupled system. The effect of working fluid variation has been examined by the numerical analysis and the possible improvement has been identified. Experimental investigations present a demonstration of the successful lab-scale implementation of the concept and validate the numerical and analytical models developed. Successful deployment of the fully coupled mine heating system proposed here will assist the mining industry on its journey towards energy-efficient, and sustainable mining practices through nearly 70% reduction in fossil fuel consumption for heating intentions.

Neural Network Soft Sensors for Gasoline Engine Exhaust Emission Estimation

AbstractWorldwide research and development programs aim to reduce harmful emissions from transportation vehicles. Soft sensors have shown great potentials to reduce cost and improve onboard diagnosis for vehicle emission control. In this work, two sets of soft sensors are proposed to predict the emissions and exhaust heat flux of a gasoline engine. Extensive steady-state measurement points over the entire engine operating conditions are collected for model training and validation, and the locally linear model tree learning method is adopted. The CO, NOx, hydrocarbon, exhaust temperature, and exhaust heat flux are estimated by the soft sensors under steady-state conditions. Training of CO, exhaust temperature, and exhaust heat flux models has achieved high model accuracy over the entire engine map. Local models are developed for NOx and HC emissions to improve model performance at different engine operating speed/load conditions, especially in the low emission zone. Model validation has shown correlation coefficients ranging 0.983 ∼ 0.999

Comparison of Heat Transfer rates for Water and Ethylene Glycol mixtures for Diesel engine exhaust gas heat recovery using Shell and Tube Heat Exchanger.

Most of the researchers have claimed that high compression engines (diesel engines) are performing slightly above of 1/3rd of their potential and remaining heat energy is wasted in the form of exhaust gas. Efforts are going on to improve the design of these engines and investigations are being carried out to recover this waste energy from exhaust gases and utilize for different applications.In the present work, initially water is used as a heat exchange medium for three different loads on diesel engine viz., 50%, 60% and 70%, which extracts heat energy to evaluate the exhaust heat attainable from exhaust gases of the engine. The exhaust gas is passed through the tube side of the heat exchanger which is obtained from an exhaust manifold of a four stroke single cylinder diesel engine. Water is passed through the shell side of the shell and tube heat exchanger. Later this work is repeated for two different cooling medium i.e. water-ethylene glycol mixtures with 25% and 50%. The results are compared for 60% engine load conditions. The counter flow type heat exchanger arrangement is considered for the analysis. The temperatures were recorded for hot gases and cold medium at inlet and outlet points of the shell side and tube side flow. Heat calculations are carried out for each combination and detailed in the result–discussion and conclusion chapter. The objective of this work is to assess the exhaust gas heat recovery capacity using the ethylene glycol-water mixture and come out with a mixture for higher heat recovery capacity. This work is undertaken with segmental baffle heat exchanger of zero degree inclination. Also the work is repeated for inclined baffle heat exchangers of 10-degree and 20-degree baffle inclination to assess the effectiveness of liquid in recovering the heat from exhaust gases. It is observed that the water and Ethylene glycol mixtures have performed satisfactorily in all three baffle setups showing only 1.5% - 2.0% less heat recovery when compared with only water.

Operational Scenarios of a Gas Turbine Using Exhaust Gas Recirculation for Carbon Capture

Abstract Finding viable economic solutions to significantly reduce or eliminate greenhouse gas emissions from energy and transportation products in the near future is paramount for the long-term survival of fossil fuel-burning systems. One of which, the industrial gas turbine, has proven for decades to be a versatile energy system providing high efficiencies in combined heat and power (CHP) applications melding well within existing infrastructure. Applying appropriate technology, the industrial gas turbine could be augmented to both sequester carbon and improve efficiency leveraging the full heating value of the fuel. The paper considers a more detailed operational assessment of a gas turbine using exhaust gas recirculation (EGR) to enable cost-effective postcombustion carbon sequestration and utilization. In this study, the effect of using EGR will be assessed at part load and throughout the operational envelope quantifying component and overall performance, detailed combustion characteristics, and maximizing the utilization of exhaust heat and sequestered carbon in various applications. This study will also attempt to quantify true carbon footprint of gas turbine installations and endeavor to understand the relative change of replacing the gas turbine with an all-electric alternative. Fundamentally, we are looking to see if there is a future to sustain and adapt this significant natural gas (NG) energy infrastructure to a net-zero carbon emissive future by 2050.

Multi-objective optimization of a novel combined cooling, dehumidification and power system using improved M-PSO algorithm

This study proposes a novel combined cooling, dehumidification and power system based on internal combustion engine (ICE) for high temperature and humidity regions. In the proposed system, the electricity demand is mainly provided by ICE while the cooling and dehumidification demands are totally satisfied by absorption chiller (AC) and liquid desiccant dehumidification (LDD) units driven by waste heat of engine exhaust and jacket water. In addition, the electricity demand can be supplemented by battery and Organic Rankine Cycle (ORC) units driven by abundant waste heat of ICE. The aim of this system is designed to succeed the highly efficient utilization of ICE waste heat among AC, LDD and ORC units, and satisfy the multi-energy demands of users by optimizing the operation strategy. Firstly, a case study based on the actual power, cooling and dehumidification demands of a hotel building in Singapore is conducted to assess the performance of the proposed system. The parametric study of prominent design parameters in this system is investigated first to explore their effects on the system performance. Next, considering annual total cost and CO2 emissions as evaluation objectives, augmented ε-constraint method combined with improved Mutation particle swarm optimization (M-PSO) algorithm is used to conduct the multi-objective optimization of equipment capacity and operation. Finally, a sensitivity analysis of significant uncertainty factors is researched. The optimal results show that, compared to the traditional energy supply system, the annual carbon dioxide emission reduction ratio and total cost saving ratio can reach 35.91% and 25.46%, respectively.

Optimization research on the off-design characteristics of partial heating supercritical carbon dioxide power cycle in the landfill gas exhaust heat utilization system

• Off-design characteristics of partial heating supercritical CO 2 cycle are studied. • A novel calculation flow chart for the system off-design performance is proposed. • Separation control and inventory control are adopted for the thermal system. • A best control scheme relied on the net power maximization can be determined. Landfill gas waste heat power generation is an effective way to promote the efficiency and economics of power plants. However, the operating performance of the power generation system needs to be improved further. In this paper, a systematic optimization research on the off-design characteristics of the partial heating supercritical carbon dioxide power system for exhaust heat utilization from gas turbine cycle are conducted. Optimal operating conditions in thermodynamics and economics obtained by genetic algorithm are determined as design conditions. Gradient descent method is used to obtain the best operating point under a certain off-design working condition. With the goal of maximizing net power output, separation control and inventory control are applied to the system. The results exhibit that the best thermoeconomic performance can be gained when the pressure ratio is 2.28 with separation ratio of 0.35 at design stage. In the off-design stage, the maximum net power shows an approximately linear growth trend from 1581 kW to 2924 kW with increasing heat source temperature and mass flow rate under the inventory control, while growth rate of net power output gradually decreases under the separation control. Finally, the best control scheme mixed with inventory control and separation control is proposed and determined quantitatively.

Dealing with uncertainty in automated operational planning for residential fuel cell system: A comparative study of state-of-the-art approaches

Polymer electrolyte fuel cell cogeneration systems (PEFC-CGSs) provide hot water by utilizing exhaust heat produced in electricity generation process. The energy saving potential of PEFC-CGSs can be maximized by optimal operational plans, and most state-of-the-art approaches implement operational planning function (OPF) based on energy demand time-series prediction by using machine learning techniques. In general, prediction of demand time-series with small expected average errors is regarded as the most important point in obtaining appropriate operational plans; however, several recent studies have revealed that other complex factors such as the direction and timing of forecast errors greatly affect the quality of operational plans in some cases. Core ideas proposed in these previous studies are broadly classified into seven types. The purpose of this study is to characterize these OPFs from the two aspects: the output form of prediction model and prediction target variable, and to clarify “what kind of uncertainty should be focused on” and “how this uncertainty should be handled” in designing OPF. The seven kinds of OPFs were comprehensively evaluated via numerical simulations using real-world data. The results show the significance of OPF based on prediction of expected operational cost surface using multiple output prediction model.

Electric vehicle charging station using fuel cell technology: Two different scenarios and thermodynamic analysis

This study evaluates two different scenarios of an integrated system to generate electricity for a charging station using proton exchange membrane fuel cell (PEMFC) and solid oxide fuel cell (SOFC). To improve the efficiency, the exhaust heat of these two fuel cells are recovered by two different bottoming power cycles of Kalina Cycle (KC) and Organic Rankine Cycle (ORC). The system is designed for a 100 kW charging station capable to charge five cars simultaneously, assuming a standard car used in daily life with a battery capacity of 36 kWh and a range of 220 km. Thermodynamic analysis of the system is performed in different current densities from 0.5 A/cm2 to 0.8 A/cm2. In the first scenario, results indicated that the overall energy efficiency of the system is 58.47% at 0.5 A/cm2 and 49% at 0.8 A/cm2, while that of the second scenario is 43.21% at 0.5 A/cm2 and 35% at 0.8 A/cm2. To improve the dynamic response of the system, a high capacity battery and a supercapacitor were integrated to the fuel cell system. It was found that a hybrid combination of the battery and supercapacitor improve the performance of the system.

Performance analysis of a concentrated photovoltaic cell-elastocaloric cooler hybrid system for power and cooling cogeneration

A new hybrid system model comprised of a concentrated photovoltaic cell (CPC) and an elastocaloric cooler (ECC) is proposed, where the ECC is driven by the thermal energy from CPC that cannot be converted into electrical energy. Mathematical expression between the exhaust heat of CPC and the operating electric current as well as the time required for one cycle are derived. Mathematical formulas for the power output and efficiency of CPC and proposed system and the cooling rate and efficiency of ECC are specified. Calculations show that maximum energy efficiency (MEE) and maximum power density (MPD) of hybrid system are, respectively, 20.20 % and 767.47 W m−2 larger than that of the CPC alone. A variety of design parameters and operating conditions affecting the hybrid system performance are studied. Numerical calculation results show that the environmental temperature, solar irradiation, concentration ratio and cross-sectional area ratio of CPC as well as length ratio are helpful to improve the hybrid system performance. The results obtained are helpful to optimally design and run such a real CPC/ECC hybrid system.

Study on thermal-hydraulic characteristics of hybrid heat exchangers with interpolated etched plates

The Supercritical carbon dioxide (S-CO2) Brayton cycle can be used to recover the exhaust heat energy of marine diesel engines. The hybrid heat exchanger is one of the potential solutions for heat exchange between flue gas and S-CO2, but there is no good design theory and design method at present. The traditional hybrid heat exchanger has an one-to-one correspondence between the fin and the etched plate. However, under special requirements, it is necessary to insert etched plates in the hybrid heat exchanger to improve the thermalhydraulic characteristics. In this study, four CFD models of the hybrid heat exchangers with interpolated etched plates were established. When the total mass flow rate and the total mass velocity are constant, the thermalhydraulic characteristics of the hybrid heat exchanger are analyzed by Fluent. The results show that regardless of the constant mass flow rate or the constant mass velocity, inserting etched channels into the hybrid heat exchanger will increase the total heat transfer coefficient. When the total mass flow rate of the cold and hot fluids is unchanged, the heat transfer coefficient and pressure drop of the etched channel decrease with the increase of the inserted etched channel. When the total mass velocity of the hybrid heat exchanger is unchanged, the insertion of the etched channel causes the pressure drop and the convective heat transfer coefficient of the fin channel to increase. Meanwhile, the pressure drop and convective heat transfer coefficient of the etched channels are reduced, but the total heat transfer coefficient is increased. The study can provide guidance for the design of the hybrid heat exchangers.

The Application of Liquid Circulation Heat Recovery System

This paper analyzes the characteristics of the exhaust heat recovery devices and the air conditioning system of the pharmaceutical factory, and points out that the pharmaceutical factory is more suitable for the liquid circulation heat recovery system. The principle and composition of the liquid circulation heat recovery system are also introduced. The actual engineering case proves that the use of liquid circulation heat recovery system can effectively reduce the fresh air load. Compared with the traditional fresh air pretreatment method, liquid circulation heat recovery system has a short payback period.

Design and simulation of heat sink for exhaust heat recovery system using thermoelectric generator

Heat sinks are a classification of heat exchangers ideally utilised in electronics to cool them. They can be simply fabricated, have low cost and are reliable for heat dissipation purpose. The protruding surfaces from them are called fins. They can be flat-plate or pin shaped. The aim of the present study is to investigate the performance characteristics of a heat sink. The materials and the fin design will be used as two major factors to increase the heat dissipation from the test apparatus. The project will show a three-dimensional analysis, using COMSOL 5.3a, which will verify with accessible exploratory information in the existing data for a continued finned heat sink. It will also identify the heat dissipation and mean temperature distribution of the heat sink for natural convection. Before moving on to design and simulation of heat sink, the first aim was to construct and simulate a leg of a thermoelectric generator model for obtaining the optimum working region of the thermoelectric generator taking into consideration the properties such as temperature difference and heat transfer coefficient. Therefore, available research techniques are briefed upon which enhance the heat removal from heat sinks.

Characteristics analysis of an exhaust thermoelectric generator system with heat transfer fluid circulation

Low heat transfer performance in the exhaust channel limits the thermoelectric conversion efficiency of the internal combustion engine exhaust thermoelectric generator. Enhanced heat transfer of exhaust channel improves the thermoelectric performance of the generator, though with an increase in exhaust back pressure. A new type of thermoelectric generator with heat transfer fluid circulation is proposed. A heat transfer fluid replaces the exhaust after heat exchange with the exhaust into the generator. It is possible to improve the thermoelectric performance of the system, counting on the high heat transfer coefficient of the heat transfer fluid in the generator without changing the exhaust channel. A mathematical model of the novel system is constructed, considering the system structure, resistance power consumption, temperature dependence of the physical properties of the module. The influence of structural parameters and heat transfer fluid parameters on thermoelectric performance are analyzed using this model. It is found that the peak net output power of the new generator can be increased by 77.5 % compared with the traditional generator, while the number of modules can be reduced by 83.2%. Therefore, an optimal exhaust heat exchanger configuration is obtained to maximize the net output of the system. In addition, as the heat transfer fluid flow rate increases, the net output power goes up and then down, an optimal heat transfer fluid flow rate can be obtained. The results also give technical guidance on the design and operation criteria of the thermoelectric generator.