جستجوی مقالات مرتبط با کلیدواژه "waste heat recovery" در نشریات گروه "مکانیک"

The use of water electrolysis to produce hydrogen gas has received much attention in recent years, because in this method, water is decomposed into hydrogen and oxygen gas without any pollution. In this research, an organic Rankine cycle (ORC) is simulated and analyzed to utilize waste heat to run an electrolyzer. The power generated by ORC is used to produce hydrogen gas in proton exchange membrane electrolyzer (PEME). Model and codes for the electrolyzer is done by EES software, and thermodynamic analyzes are utilized in order to examine the performance of the proposed model. For the evaporator temperature of 67 ℃, the ORC power and thermal efficiency are obtained at 220 kW and 8.5 %, respectively. The production capacity of the electrolyzer considered in this research is 27 kg per hour of hydrogen gas with a temperature of 80 ℃ and a pressure of 101 kPa. Water electrolysis is performed using direct current between two electrodes, anode and cathode, which are separated by a membrane. To validate the simulated model, membrane potential at different values of current density is calculated.

In conventional vehicles, about 40% of fuel energy is converted into useful power, and the rest is directed to the environment by cooling and exhaust systems, which, in addition to energy loss, are also one of the main sources of air pollution. At present, all over the world, food suppliers use online orders for their customers to move ready-made food from the place of production, such as restaurants, to their destination while maintaining its quality. However, along this route, due to the long distances that cause heat loss from the food container, it creates problems for food to cool or heat drinks in online orders. Therefore, using a thermosyphon in the exhaust gas path to recover waste heat is one of the methods that can be used in addition to solving the problem of existing pollution with heating applications and also for cooling applications of vehicle electricity as chamber cooling. In this research, a mobile combined cycle (heating-cooling chamber) was used to keep the chamber warm with the best filling percentage of 75% in all inlet capacities for 25 minutes to about 48 °C using a thermosyphon and cool the other chamber for 8 minutes. It was designed and built up to a temperature of about 5 °C with the help of thermoelectric cooling.

The limitation of global fossil fuel resources has had a significant impact in recent years. Iran wastes 570 million barrels of oil out of the allocated 1463 million barrels for the residential, industrial, and transportation sectors. The cement industry, as one of the high-energy consumers, accounts for approximately 14% of the country's industrial energy consumption, with about 40% of this energy being lost during production processes. This study aims to recover the waste heat from the cement industry using the Rankine cycle and simulate it using the Engineering Equation Solver (EES) software. Additionally, a thermal oil loop has been employed to prevent corrosion of heat exchangers and control the organic fluid evaporation process. Ethanol has been selected as the suitable working fluid, with a net power production capacity of 6213 kW, a thermal efficiency of 91.22%, and an exergy efficiency of 18.24%, outperforming R123, R1233zd(E), R1234ze(Z), and R600a. Increasing the turbine's inlet pressure by 100 kPa increases thermal and exergy efficiencies by 2.7% and 2.67%, respectively, while decreasing the mass flow rate into the evaporator by 5.6%. Increasing the condenser temperature by one degree results in approximately a 5.6% reduction in thermal efficiency and a 5.5% reduction in exergy efficiency.

The flame fuel cell is a new type of solid oxide fuel cell in which the solid oxide fuel cell is integrated with a rich fuel flame to generate power. In this paper, a flame-assisted solid oxide fuel cell is employed to generate power, and the cell is simulated in EES. The model includes the equations of mass, energy, and chemical and electrochemical reactions. Parametric analysis of the fuel cell shows that by increasing the equivalence ratio from 1.2 to 2.8, the fuel cell efficiency changes from 4.21% to 18.23%. In this study, the supercritical Brayton carbon dioxide cycle is used to recover the waste heat of the cell. To optimize this thermal cycle, the compressor pressure ratio and flow split fraction have been considered. In the optimal pressure ratio, efficiencies for turbine inlet temperatures of 583.15 K, 823.15 K and 923.15 K have been obtained as 31.56%, 47.95% and 52.69% for the pressure ratio parameter, respectively. The results reveal that the efficiency of the integrated cycle is improved and reached from 18.23% to 26.95% for Φ = 2.8

In the last years, hydrogen production not only as a green fuel but also as an energy career has gained much attention. This is while, hydrogen can be considered as one of the main chains of alternative fuel production like green methanol and green ammonia. In this study, the waste heat of the offshore installed gas turbines is utilized to produce hydrogen via employing Alkaline electrolyzers. In most cases, gas turbines are installed to cover the electricity consumption of the offshore facilities and waste heat recovery from these turbines is not a matter of concern. In this paper, the energy content of the exhaust gasses of the gas turbines is utilized to run steam and organic Rankine cycle and then generated surplus power is fed to electrolyzers to produce hydrogen. Results revealed that under the base condition exhaust temperatures of 450, 525 and 600 ˚C lead to hydrogen production of 1308, 1769 and 2191 ton per year, respectively.

In this study, the hybrid of organic Rankine cycle with heat recovery system of low temperature gases in Electric Arc furnace has been investigated. Moreover, the effect of the steam accumulator on stabilizing the mass and heat of exhaust gases of the heat recovery boiler is shown. Hence, constant thermal power has been achieved for a longer period of time for the organic Ranking cycle. The steam accumulator thermodynamic model is simulated based on the non - equilibrium thermal model for the liquid and vapor phases. Furthermore, the steam accumulator pressure variations with different mass outflow rates have been investigated. Constant and continuous thermal power has been reached with an output mass flow rate of 2.84 kg/s during four processes of the electric arc furnace. The transient state of the aforementioned hybrid system has been studied from the energy and exergy points of view. The energy and exergy efficiencies of the whole system are calculated with three working fluids Hexamethyldisiloxane, Toluene, and R245fa of the organic Ranking cycle. Toluene with thermal and exergy efficiencies of 16.4% and 27.1%, respectively, is suitable for use in the organic Ranking cycle compared with the other two fluids.

In conventional passenger cars, two-third of the energy is wasted from the exhaust gas and engine cooling system. The present study has investigated the performance of a waste heat recovery (WHR) system based on the Organic Rankine Cycle (ORC) for the turbocharged gasoline direct injection engine. The optimal working conditions along with the best working fluid of the organic Rankin cycle to obtain the maximum net output power (NOP) from the recovery cycle are investigated. The steady-state zero-dimensional thermodynamic model of basic ORC at a series of engine operating conditions is designed in Thermoflex software. The working point of the engine has obtained by simulation of vehicle performance based on the standard urban driving cycle. Considering numerous and varied working fluids, 23 working fluids including pure and mixture fluids are evaluated. The mass flow rate of working fluid, condenser pinch, turbine inlet pressure, and condenser working pressure are considered as the optimization design variables and the optimum operating conditions of the basic ORC extracted for each working fluid using the Downhill Simplex method. Finally, by having experimental data for 320 points of the engines map, the efficiency of the optimized basic cycle was analyzed in combination with engine’s entire operating region. The results showed that R-507a, R-410a and R-125 present highest NOP respectively which indicate better performance of zeotropic and Azeotropic mixtures in engine WHR by ORC and for the best case, NOP reached to 2.6 kw in small load region and 6.6 kw in the peak thermal efficiency region.

A significant percentage of the heating value of the fuel is lost in the form of hot exhaust gases from the vehicle exhaust system. In recent developments, thermoelectric materials have been developed with high efficiency, simplicity, and good strength, and the tendency to use this technology to directly convert wasted heat into electricity has increased. Vehicle heat generators are one of the applications of this technology. In the present paper, a vehicle thermoelectric generator model was first confirmed with experimental data, and then changes were made to the parameters that affect the fuel economy and output power of the vehicle thermoelectric generator. The design that produces the maximum output power is different from the design that produces the most fuel economy. Backpressure was identified as the most important factor in fuel consumption. Different parameters were examined, each of which had different effects on fuel consumption and power output, and finally, a model was obtained that could reduce the overall fuel consumption by 0.07 in the vehicle at rest.

Rising fuel prices and limited fossil fuels have motivated scientists to find some new methods to recover the heat dissipation from the internal combustion engines exhaust gases in recent decades. Only 30 percent of the fuel energy is converted to the useful work and the rest of it is lost through the exhaust gases of the engine and the engine coolant system. In this paper this issue has been considered and hence two different configurations of organic Rankine cycle with two operating fluids R113 and R123 have been designed and energy and exergy analysis have been applied in order to recovering the heat dissipation from the six cylinder internal combustion engine exhaust gases (in full load operating mode). Next, the performance of these cycles has been optimized by sensitivity analysis to find the optimum working temperature and pressure of these two cycles. the results shows the optimum points of the system which is calculated by the mention technique.

The main part of the input energy to the cylinder of an internal combustion engine is lost by various factors, and only about one third of this energy becomes useful. Therefore, providing solutions that can recover waate heat from engine exhaust gases and coolant is remarkable and useful. In current study the effect of start of injection timing on the RCCI engine on the waste heat recovery capacity has been investigated. A CFD model is used to simulate the engine. At first, the model was verified using experimental data and then the diesel fuel start of injection timing has been changed and their effects on exergy destruction, waste heat recovery capacity, power output and emissions have been investigated. The results showed that advanced start of injection timing, increases engine efficiency and decrwases exhaust CO and HC emissions. In addition to, heat transfer exergy has increased due to the the higher in cylinder temperature, and the higher temperature has led to an increase in irreversibility due to the increased number of reactions. Advanced fuel injection timing has improved the utilization factor and higher value of utilization factor is obsereved when fuel is injected at 20 CAD before TDC

In this study, in order to waste heat recovery from a marine diesel engine, a humidification – dehumidification desalination unit type of open – water and closed – air cycles with water heated is proposed for producing the consumed fresh water the crew of the ships. The energy required to produce freshwater is provided by recovered heat from exhaust gases from marine diesel engine. For this proposed system, first simulated thermodynamically and detailed energy and exergy analysis, in order to determine the main sources of irreversibility and performance characteristics of the system is conducted. Moreover, a comprehensive parametric study to find key parameters trend with system performance parameters is carried out. The study found that the system has the ability to produce 0.2746 kg.s-1 fresh water, using 432 kW of primary energy. As well as desalination efficiency and exergy efficiency were calculated to be 1.516 and 23.9%, respectively. And from an exergy analysis it can be seen that among all the components of the system, the heater has the highest exergy destruction rate, which accounts for about 73.2% of the total exergy destruction rate.

Despite recent improvement in energy efficiency of diesel engines, more than 50% of the energy input is lost as waste heat in the form of hot exhaust gases, cooling water, and heat lost from hot equipment surfaces. Exhaust pollution from internal combustion engines can potentially result in severe damages on earth atmosphere, including ozone depletion, global warming, and significant health problems. Waste heat recovery based on Rankine cycle has been identified as a potential solution to increase the energy efficiency and consequently to reduce the engine emissions. In this rather low cost technology, waste heat is recovered in a Rankine cycle, aiming to convert mechanical power into electrical power. Output electrical energy is stored in a battery and can be used in electric usages. In this paper, the possibility of using the exhaust heat recovery system without utilizing the heat of other recyclable materials has been investigated, using the organic Rankine cycle (ORC), in order to increase the efficiency of the diesel engine of the bus. Depending on amount of achievable heat of exhaust, in some performance point of diesel engine, the amount of fluid flow rate and output power of Rankine cycle was calculated. Our results exhibit 5.1 KW increase in the diesel engine power resulting in 1.12% increase in energy efficiency in engine part load condition. The output mechanical power from the micro-generator is converted to electrical power and is stored in an energy storage system. The storage energy can be utilized to supply power for electrical equipment such as fans, bulbs, and also phone chargers of passengers.

In this paper, using a hybrid compression-absorption refrigeration system for providing cooling demand of air condition and fridges for meat, fish vegetable and dairy preservation, simultaneously on a ship is proposed. Cooling demands for air condition and fridges are in each ship. So, the use of proposed system can be considered in all ships and is not limited to a special one. Exhaust gases of auxiliary engine are applied as a heat source for absorption section. The results show that exhaust gases heat recovered is higher than the demand of generator on all ranges of engine loads. Unlike main engine, auxiliary engines are always on and don’t depend on the movement of ship. So, exhaust gases of auxiliary engine as a heat source is an appropriate and permanent heat source for generator of absorption section. Based on energy, exergy and environmental analysis, a comparative performance analysis of proposed system and conventional system (vapor compression refrigeration system) has been carried out. The results show that based on tropical condition, fuel consumption and total irreversibility of proposed system are respectively 91.6% and 26.6% less than conventional system. Using a hybrid compression-absoption refrigeration system in comparison to vapor compression refrigeration system causes 64834 $ annual saving due to reduction in CO2 emission penalty(cost).

In this article the effect of using ejector on the thermodynamic performance of the hybrid heat pump is evaluated. With simulation of the new hybrid-ejector heat pump in the EES software, first the effect of the ejector mixing section diameter on the results is analyzed and it is concluded that a diameter of about 15mm makes the primary energy ratio (PER, the ratio of useful thermal energy output to the total initial heat energy input) and second law efficiency of the heat pump to be maximum and the exit temperature of the compressor to be minimum. Next, PER, second law efficiency and the compressor exit temperature of new heat pump are compared with those of the conventional hybrid heat pump at the same amount and temperature of the input heat. The results showed that the PER and second law efficiency of the new layout is maximum 10 percent and about 18 percent higher than those of the hybrid cycle respectively. It is also observed that with considering the restriction in compressor exit temperature, in new system, it is possible to increase the temperature of input heat 35C more compared to the increase that can be occurred in the hybrid system. Finally, the analysis of the relative exergy losses in the components of the systems revealed that in the new layout, the relative exergy losses of throttling valve, desorber, compressor and absorber were reduced and improved the performance of this cycle.

Large amount of diesel engine waste heats make researchers design systems that utilize the engine waste heat to provide the cooling demand of the heavy-duty vehicles and improve the engine efficiency. Considerable advantages of adsorption cooling system lead to be nominated for this purpose. Coolant and exhaust gases are the main sources of waste heats of diesel engines and using each of them to drive the adsorption cooling system requires its own equipment and working pair. In this paper, a detailed numerical model has been developed and to examine the performance of the cooling system driven by the coolant waste heat with working pair of silica gel-water and also driven by exhaust waste heat with zeolite13x-water working pair. An identical absorbent bed and ambient conditions have been employed to compare the performance of both systems to identify the more appropriate system. The results show that exhaust driven adsorption cooling system has more capability to meet the vehicle cooling demand. Moreover, the performance of the both adsorption cooling systems were examined under variable ambient condition. Results indicate that increase in ambient temperature leads to almost a linear performance drop in both systems that is more considerable in the coolant- driven adsorption system.