Engine Exhaust Heat Research Articles

Investigation of fouling mechanisms for diesel engine exhaust heat recovery

The effect of diesel engine exhaust fouling on heat and mass exchangers for waste heat recovery is investigated. Experiments are conducted for a range of operating conditions relevant to the use of the waste heat from a diesel engine for powering a 2.71 kW capacity absorption heat pump. Thermal resistances of fouling layers as well as their effects on pressure drop are determined, and the underlying mechanisms for deposition and removal are investigated. Fouling layer effects are most severe for the lowest coolant temperatures and 100% generator load. At these conditions, the fouling thermal resistance is approximately 70% of the total resistance, and the ratio of the steady-state pressure drop to the baseline pressure drop is 3.25. Flow induced shear is found to be the primary growth inhibiting mechanism at high exhaust velocities. Results from this study can guide heat exchanger design for a variety of waste heat recovery systems.

Thermodynamic analysis and parametric optimization of a novel S–CO2 power cycle for the waste heat recovery of internal combustion engines

With the aim to recover the exhaust heat of internal combustion engine efficiently, a novel supercritical CO2 (S–CO2) power cycle is proposed on the basis of recompression cycle configuration. The corresponding thermodynamic models are established to analyze the energetic and exergetic performances of the system. The effects of turbine inlet temperatures and system pressures are investigated. Thereafter, in order to output the maximum net work, genetic algorithm (GA) is employed to optimize these key parameters. Under design conditions, the calculated results indicate that the thermal efficiency and the exergy efficiency of the system can reach up to 35.86% and 67.90% respectively. Furthermore, as the inlet temperature of high pressure turbine increases, cycle efficiency increases while output work decreases. However, for the effect of inlet temperature of low pressure turbine, cycle efficiency and output work increase with the increase of temperature. As for the intermediate pressure of this system, there exist pressures to get the maximum net work and cycle efficiency. Based on GA optimization, an optimal combination of system parameters is obtained. The corresponding maximum cycle power is 39.49 kW, and the recovery efficiency of waste heat can reach up to 74.83%.

Closed-Loop PI Control of an Organic Rankine Cycle for Engine Exhaust Heat Recovery

The internal combustion engine (ICE) as a main power source for transportation needs to improve its efficiency and reduce emissions. The Organic Rankine Cycle (ORC) is a promising technique for exhaust heat recovery. However, vehicle engines normally operate under transient conditions with both the engine speed and torque varying in a large range, which creates obstacles to the application of ORC in vehicles. It is important to investigate the dynamic performance of an ORC when matching with an ICE. In this study, the dynamic performance of an ICE-ORC combined system is investigated based on a heavy-duty diesel engine and a 5 kW ORC with a single-screw expander. First, dynamic simulation models of the ICE and the ORC are built in the software GT-Power. Then, the working parameters of the ORC system are optimized over the entire operation scope of the ICE. A closed-loop proportional-integral (PI) control together with a feedforward control is designed to regulate the operation of the ORC during the transient driving conditions. The response time and overshoot of the PI control are estimated and compared with that of the feedforward control alone. The results based on the World Harmonized Transient Cycle (WHTC) indicate that the designed closed-loop PI control has a shorter response time and a better trace capacity during the dynamic processes. The average output power and thermal efficiency during the WHTC cycle are improved by 3.23% and 2.77%, respectively. Compared with the feedforward control alone, the designed PI control is more suitable for practical applications.

Optimal design of organic Rankine cycles for exhaust heat recovery from light-duty vehicles in view of various exhaust gas conditions and negative aspects of mobile vehicles

The organic Rankine cycle (ORC) is a promising method of recovering the exhaust heat of the internal combustion engine (ICE). However, the off-design exhaust conditions and the negative effects (such as increased backpressure and added weight) of the ORC installation onto vehicles greatly deterioratetheperformanceof ORC applied on mobile vehicles. In this paper, the ORC thermodynamic model with an integrated plate heat exchanger model is developed to evaluate the effects of sizing the heat exchanger and designing the ORC operating conditions on the thermodynamic performance of the ORC system. Considering various major exhaust conditions and the negative impacts of ORC system installation on vehicles, an optimal ORC system design strategy is proposed to maximize the net output power. The optimum geometric parameters of heat exchangers and ORC operating conditions are simultaneously designed through a mixed integer nonlinear programming problem. The proposed design strategy is compared with the design method without considering negative effects and the design method only based on one major engine operating point. The comparison results indicate that the proposed design strategy increases the weighted net output power and the proposed design strategy can ensure that the ORC works normally in various exhaust conditions. Among all the operating parameters, the size of the heat exchanger (two geometric parameters) is the major factor affecting the performance of ORC. These findings highlight the importance of considering various exhaust conditions and the negative impacts of vehicle-mounted ORC during the design procedure.

A Compact Thermally Driven Cooling System Based on Metal Hydrides

Independent of the actual power train, efficiency and a high driving range in any weather conditions are two key requirements for future vehicles. Especially during summertime, thermally driven air conditioning systems can contribute to this goal as they can turn the exhaust heat of internal combustion engines, fuel cells or of any additional fuel-based heating system into a cooling effect. Amongst these, metal hydride cooling systems (MHCSs) promise very high specific power densities due to the short reaction times as well as high reaction enthalpies. Additionally, the working fluid hydrogen has a very low global warming potential. In this study, the experimental results of a compact and modular MHCS with a specific cooling power of up to 585 W kg MH − 1 referred to one cold generating MH are presented, while reactor and MH weight in total is less than 30 kg and require a volume < 20 dm3. The system is driven by an auxiliary fuel heating system and its performance is evaluated for different operating conditions, e.g., temperature levels and half-cycle times. Additionally, a novel operation optimization of time-shifted valve switching to increase the cooling power is implemented and investigated in detail.

Experimental investigation on innovatory waste heat recovery system impacts on DIESEL engine exhaust emissions

ABSTRACT Globally compression ignition engines are one of the major pollutants that fuel the environmental imbalance through exhaust emissions. So, this article explores the impact of innovative waste heat recovery from diesel engine harmful exhaust emissions. A double pipe, externally internally protracted finned counter flow heat exchanger (PFCHE) was innovatively planned, partially coated and tested with binary mixtures as working fluids to harvest the engine exhaust heat. The PFCHE employed, resulted in considerable amount of reduction in the emissions from engine which can be attributed to partial coating of γ-alumina diesel oxidation catalyst. The experimental result showed that there is a decline in the emissions of nitrogen oxides, carbon monoxide and hydrocarbons with partially coated PFCHE. The investigation confirmed the reduction of hydrocarbons and NOx emissions up to16% and 7% respectively at full load conditions, when compared with standard engine operations, excluding heat exchanger. There was a decrement in smoke from 60HSU to 40HSU at the time of full load engine operation. According to the results achieved from the current study, it can be inferred that the partially coated PFCHE could be an optimum heat exchanger for exhaust heat energy recovery as well as it can reduce the emissions from engine exhaust.

Experimental Analysis of a Laboratory-Scale Diesel Engine Exhaust Heat-Driven Absorption Refrigeration System as a Model for Naval Surface Ship Applications

Decreasing industrial energy sources and major environmental problems caused by uncontrolled energy consumption have led to studies on alternative energy sources. This study presents a design and experimental analysis of an exhaust gas-driven absorption refrigeration system for the purpose of air conditioning by using the exhaust heat of a diesel engine, which is installed in the Naval Academy Mechanics Laboratory. The diesel engine is loaded with a dynamometer, and water and ammonia are used as an absorbent and refrigerant, respectively. At various diesel engine loads, cooling capacity and coefficient of performance (COP) of the absorption refrigeration system are calculated. Experimental results have indicated the cooling capacity as 1.098 kW at a maximum engine power of 4.9 HP. The highest COP value in the designed system has been calculated to be .3022 for the generator temperature of 160 C. Although the COP of refrigeration is low, the absorption refrigeration system can be provided a great cooling load from the exhaust heat of diesel engines and can be used in naval surface ships. In addition to energy efficiency of naval surface ships, infrared and acoustic signature can be minimized and a ships susceptibility can be dramatically reduced.

The performance of thermoelectric exhaust heat recovery system considering different heat source’s fin arrangements

The IC engine converts the chemical energy of the fuels into the mechanic energy with the efficiency is around 35-40% depends on the type and operation condition of the engines. It means around 60-65% of the energy is wasted mostly in the form of heat (dissipated through the cooling process and exhaust gas) and friction. A thermoelectric exhaust heat recovery system can be used to harvest the waste heat which potentially could increase the efficiency of the IC engine indirectly. In this experimental study, the heat recovery system consists of a rectangular duct in which sixteen thermoelectric modules are attached to its sides (each side consist of four thermoelectric modules). The aluminium fins are mounted at the cold sides of thermoelectric modules (at the outer sides of the rectangular duct) and cooled by air supplied by computer fan coolers. To harvest the exhaust heat of the IC engine, the heat recovery system is connected to the exhaust pipe. The effect of aluminium fin arrangements, mounted on the inner surfaces of the rectangular duct of the heat recovery device, is investigated. The arrangements include mounting of the fins at the lateral sides, top and down sides, and the whole sides of the heat recovery device. Besides, the effect of the absence of the fins at the exhaust gas passage of the heat recovery device is examined. The performance of the heat recovery system is studied when the engine operates under the no-load condition at rotational speeds of 1300, 1600, 1900 and 2200 RPM. The experimental result reveals that the voltage and current generated by the thermoelectric exhaust gas recovery system increase in line with the increase of engine speed. In addition, it is found that the highest voltage and current are generated by the whole side fin arrangement, namely 12,52V and 122 mA respectively, at an engine speed of 2200 RPM. It is observed that the finless arrangement generates the lowest voltage and current among others, namely 5.36 V and 20.43 mA.

Numerical investigation on flow and heat transfer processes of novel methanol cracking device for internal combustion engine exhaust heat recovery

In this research, a novel structure of methanol cracking device was designed for methanol decomposition by using internal combustion (IC) engine exhaust heat. To evaluate and optimize its performance, the flow and heat transfer processes in methanol cracking device were investigated by computational fluid dynamics (CFD) simulation. The results show that methanol flow rate has important effects on the pressure loss, temperature distribution and heat flux. In general, the flow velocity and pressure in methanol cracking device are not well-proportioned and it results in the asymmetrical distributions of temperature and heat transfer coefficient. The maximum heat transfer coefficient is close to 100 W/(m2·K) while the minimum almost equals to zero because of flow stagnant zone. The average heat transfer coefficient increases as methanol flow rate rises, and it reaches to 51.63 W/(m2·K) at the methanol flow rate of 0.06 kg/s. When methanol flow rate increases from 0.03 kg/s to 0.06 kg/s, the average outlet temperature decreases from 615 K to 560 K and meets the requirements for methanol cracking reaction. All these indicate that the designed methanol cracking device can be used for IC engine exhaust heat cracking methanol, and also provide theoretical guidance for further optimizing the geometry structure.

Modeling and Analysis of Thermoelectric Generators for Diesel Engine Exhaust Heat Recovery System

AbstractThe paper focuses on the performance of thermoelectric generators (TEGs) in different positions and under different running conditions. Three-dimensional numerical models of two designs of ...

Experimental and numerical analysis of diesel engine exhaust heat recovery using triple tube heat exchanger

In this study, a 2000 mm long triple tube heat exchanger was designed and manufactured in this work with three intermediate tubes having annulus space of 26, 32, and 36 mm, respectively. Experimental investigations were carried out in the system to assess the percentage of energy savings. On the Diesel engine experiments were conducted by varying the load conditions at 25%, 50%, 75%, and 100%, respectively. Motor speed was varied at 900, 1200, and 1500 rpm, respectively, for each load condition. Also incorporated during the study were counter current, co-current with counter current, counter current with co-current, and co-current fluid flow patterns. It is found that, while increasing the load and speed, the heat transfer rate of the heat exchanger increased. It is also observed that, the fluid counter current flow pattern gave better performance compared to other flow pattern types. The effects of the operating parameters on the heat ex-changer's performance are represented by the Nusselt number and effectiveness. The results of the experiments were also compared with the thermal energy storage performance of the double tube heat exchanger. It is found that, compared to double tube heat exchanger, 20% of fuel energy was saved by using triple tube heat exchanger as waste heat recovery system.

Fabrication, characterization, and application-matched design of thermoelectric modules based on Half-Heusler FeNbSb and TiNiSn

We describe the fabrication of thermoelectric modules based on Half-Heusler TiNiSn and FeNbSb and their performance assessment under different boundary conditions. Module design is guided by a multiphysics model implementing experimentally determined thermoelectric materials properties. We consider two types of boundary conditions: first, imposing fixed cold- and hot-side temperatures onto the module, and second, imposing fixed values for the heat transfer coefficients between module and heat sink and source, representative for a waste-heat-recovery system using the exhaust heat of an internal combustion engine. We compare the modeling results with experimental data obtained from Half-Heusler modules integrated into a heat exchanger mounted to the exhaust of a compact van.

Effect of waste exhaust heat on hydrogen production and its utilization in CI engine

The present study aims to utilize waste engine exhaust heat to produce hydrogen and utilize the same in the single cylinder CI engine as a closed system. A thermoelectric generator was used to convert the waste exhaust heat to hydrogen gas through PEM type fuel cell. The generator was placed in the engine exhaust and connected to the fuel cell and the output of the fuel cell was connected to the inlet manifold through a flow meter and safety devices. All the tests were conducted in a single cylinder CI engine with diesel as the base fuel and the produced hydrogen as the inducted fuel. Experiments were conducted at different load conditions with a constant speed of 1500 rpm. It is observed that the heat wasted from the exhaust increases with increase in load which improves the thermoelectric generator conversion efficiency and in turn increases the hydrogen flow rate. At maximum load, 351 ml/min of hydrogen was produced and sent to the inlet manifold of the engine. The conversion efficiency of the generator varies from 13.8% at low load to 51% at full engine load. The experimental results showed that with hydrogen induction brake thermal efficiency (BTE) was improved. At full load, BTE with hydrogen induction improves by 10% in comparison to only diesel engine operation. With hydrogen induction HC, CO and smoke emissions at full load reduced by 13.46, 31.57, and 24.7%, respectively, as compared to diesel. The decrease in emissions is attributed to decrease in diesel consumption as hydrogen replaces the diesel. However, there is a slight penalty in NOx emissions and it increases by 20% with hydrogen induction due to increase in in-cylinder temperature.

Performance assessment of engine exhaust-based segmented thermoelectric generators by length ratio optimization

Thermoelectric generators have been regarded as a prospective technique used for recovering engine exhaust heat. Segmented structure is more appropriate for large temperature gradient between the heat and cold source. This work establishes a numerical model of segmented thermoelectric generator for engine waste heat recovery based on the component level and system level simultaneously. Two patterns of p-n ratios are conducted to compare the properties between segmented and traditional models as well as optimize the segmented ratios under various conditions to get better performance. In the pattern of same p-n segmented ratios, the effects of structural parameters and thermodynamic boundary conditions on the output performance are analyzed. The optimal proportion of medium temperature material (CoSb3) increases with longer thermoelectric elements and higher heat transfer coefficient, whereas the cross section area shows hardly any influence on it. And then the power improvement capacity in view of the property difference between p-type and n-type material is investigated in the second pattern. The maximum output power is improved by approximately 13.8% compared with that of original segmented model. Finally, the application of optimal segmented ratio design in a thermoelectric generator system demonstrates better performance and further increases the output power by 6.8%.

Performance analysis of a biomass gasification-based CCHP system integrated with variable-effect LiBr-H2O absorption cooling and desiccant dehumidification

A novel biomass gasification-based combined cooling, heat and power (CCHP) system, which is composed of a gas-fueled internal combustion engine, variable-effect LiBr-H2O absorption cooling, and dehumidification air-conditioning with desiccant coated heat exchangers, was introduced. The temperature and humidity independent strategy was applied in the gasification-based CCHP system to enhance cooling production, in which the variable-effect absorption chiller and desiccant dehumidification air-conditioning were driven by the exhaust heat and jacket heat of the gas engine based on energy cascade, respectively. The operation strategy of the system followed the electric load. Validated by experimental data, a zero-dimensional code of the gasifier with Gibbs free energy minimization, an artificial neural network model of the variable-effect absorption chiller, and a 1-D dynamic model of the dehumidification air-conditioning, were built with reasonable deviations. The results of energetic, economic, and environmental (3E) analyses for the proposed gasification-based CCHP systems that were applied in two different buildings indicate that woody chips are the most favorable feedstock under the climate of Singapore. The total performance is more sensitive to the feedstock cost than to the natural gas cost. This work enables to contribute valuable data to the practical application of the biomass gasification-based CCHP system in Singapore's building sector.

Comparative Analysis of Ejector Refrigeration System Powered with Engine Exhaust Heat using R134a and R245fa

An ejector refrigeration (ER) system using exhaust waste heat of a heavy vehicle engine is investigated. A program is developed using engineering equation solver software and it is used to make the calculations of the system. The system is taking all the efficiencies of system’s components into account. Refrigerants R134a and R245fa are used for the comparative simulation of the system. The pressure at the exit of the pump is varied from 6 to 14 MPa and 3 to 10 MPa for R134a and R245fa, respectively. It can be concluded that COP (coefficient of performance) of the system gradually increases with the increase in pump exit pressure. Results show that, the performance of the system would be higher if R245fa is preferred rather than R134a with the given operating conditions.

Engine Exhaust Heat Device for Terminating Cover Crops in No-Till Vegetable Systems

Abstract. Sustainable no-till practices utilize cover crops to protect the soil surface and to improve soil properties. Proper cover crop management is the key for successful planting of the main crop directly into cover crop residue without interfering with planting operations. In the Southern United States, the recommended time to plant cash crops into desiccated residue cover is typically three weeks after cover crop termination when the termination rate exceeds 90%; this minimizes nutrient competition between cover and cash crops. The standard method to manage cover crops is mechanical termination utilizing rollers/crimpers. This technique flattens and crimp plants to expedite termination. Another method that has been used in agriculture is to injure (desiccate) plants utilizing an external heat source. An example of utilizing an external heat source has been used in vegetable production for weed control. However, there is a need to evaluate another heat source such as exhaust heat generated by internal combustion engines (which otherwise is completely wasted) for cover crop termination effectiveness. To achieve cover crop termination with exhaust heat, a prototype was invented on board a walk-behind tractor powered by a single cylinder gasoline engine from which exhaust heat was funneled from the exhaust manifold to a perforated steel rectangular tube maintaining 204°C against a flattened cover crop to damage plant tissue. The heat pusher was equipped with electric heater strips to provide supplemental heating. Three electric heater strips (front, middle, back relative to the direction of travel) were supplied with electrical energy by a generator powered by the tractor’s PTO and generated temperatures of 379°C to 421°C with a temperature transfer efficiency of 83% to 91%. The performance of the unit with and without supplemental heating was compared with standard mechanical roller/crimper. Results demonstrated that using the exhaust heat concept can be a viable option to terminate cover crops. The exhaust heat transferring channel could be better insulated to exceed the lower 23% temperature transfer efficiency achieved by the device. Cover crop termination data during three weeks of evaluation indicated that the heat-based system was as effective as a mechanical roller/crimper. Keywords: Cereal rye, Cover crop termination, Crimson clover, Exhaust heat, Flattening cover crops, Heat transfer, Heater, Plant termination.

Experimental Analysis of a Laboratory-Scale Diesel Engine Exhaust Heat–Driven Absorption Refrigeration System as a Model for Naval Surface Ship Applications

Experimental Analysis of a Laboratory-Scale Diesel Engine Exhaust Heat–Driven Absorption Refrigeration System as a Model for Naval Surface Ship Applications

Innovative method for cover crop termination using engine exhaust heat

Proper management of cover crops in conservation system is the key to achieving effective no-till planting of cash crops into desiccated residue cover without interfering with planting operations. One method of cover crop management is mechanical termination utilizing a rolling/crimping technique to injure the plant with the crimping bars without cutting stems. Another method is to injure plants using a heat source. To evaluate this concept at a small farm scale, a mechanical pusher using exhaust heat from the internal combustion gasoline engine with supplemental heat from heater strips was developed to terminate cover crops. The prototype was developed for a walk-behind tractor powered by a single cylinder gasoline engine. Heat to damage plant tissue was directed from the exhaust manifold to a rectangular perforated delivery steel tube that was in continuous contact with the cover crop that had been flattened by the pusher. In addition, a generator powered by the tractor’s PTO provided electrical energy for three parallel supplemental heater strips. Results demonstrated that using exhaust heat (otherwise lost to the environment) is a viable option to manage cover crops.

Investigation of organic Rankine cycle integrated with double latent thermal energy storage for engine waste heat recovery

In this work, organic Rankine cycle (ORC) integrated with Latent Thermal Energy Storage (LTES) system for engine waste heat recovery has been proposed and investigated to potentially overcome the intermittent and fluctuating operational conditions for vehicle applications. A melting-solidification model has been established to investigate and compare the performance of twelve Phase Change Materials (PCMs) under different heat source conditions. Among the twelve PCMs, LiNO3-KCl-NaNO3 is identified as the optimal PCM for engine exhaust heat recovery. The performance of the ORC system integrating with different volume of LTES using LiNO3-KCl-NaNO3 under dynamic heat source simulating vehicle conditions is studied. Results illustrate the fluctuation of engine exhaust heat can be potentially overcome by using the proposed solution. The condition of 100 L LTES provides 30.4% larger total output work than that of 50 L LTES, while it is merely 1.5% larger than that of 90 L LTES. The performance of three different LTES-ORC scenarios are compared and results show ORC combining with double LTES delivers 17.2% larger total power output than that of single LTES (100 L) under the same operational conditions.