Conservation of energy by WASTE HEAT RECOVERY is important not only for cost reasons, but also for reducing primary energy consumption as well as reducing carbon dioxide production. This paper explains and discusses the simulation, performance, and successful applications of thermosyphon HEAT exchangers (THE’s) for recovering WASTE HEAT from exhaust gases in industrial plants. The advantages of this system are compactness, flexibility of system size, ease of operation, and minimum maintenance requirements. The thermosyphon HEAT exchanger can satisfactorily act as a pre-HEATer of air in boilers and furnaces using the HEAT recovered from the exhaust. In this work, one successful industrial practice is explained using thermosyphon HEAT exchanger. The THE was simulated to recover WASTE HEAT from the exhaust of a nearly 7 ton boiler in the SAMEN company. The energy recovered from the flue gas is used to preHEAT the incoming air to the boiler. The average rate of WASTE HEAT RECOVERY and thermal effectiveness obtained from computer simulation are 100 kW and 40%, respectively. The payback period was less than two years. The evaluation of the thermal performance of the THE was based on the effectiveness-NTU and LMTD methods to obtain the HEAT transfer characteristics.

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 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.

In the current study, with the aim of power and hydrogen production, combination of Matiant cycle with an ORC unit and PEM electrolysis has been analyzed from the viewpoints of energy and exergy. WASTE HEAT of the Matiant cycle is used to run the ORC. Effect of some designing variables, i.e. evaporator temperature, minimum temperature difference in HEAT exchanger, degree of superHEATing in ORC turbine inlet and isentropic efficiency of ORC turbine on the rate of produced hydrogen, ORC produced power and exergy efficiency of the combined system has been investigated. It is observed that, increasing the minimum temperature difference leads to decrease in the rate of produced hydrogen, ORC produced power and consequently exergy efficiency of the combined system. Also, change in the evaporator temperature optimizes the rate of produced hydrogen, ORC produced power and therefore the exergy efficiency of the combined system. Also, results showed that increasing the degree of superHEATing in the ORC turbine inlet decreases the rate of produced hydrogen, ORC produced power and the exergy efficiency of the combined system. As expected, increasing the isentropic efficiency of ORC turbine leads to an increase in rate of produced hydrogen, ORC produced power and therefore the exergy efficiency of the combined system.

Increase of fuel price and limitation of carbon dioxide emission caused development of different techniques to enhance the thermal efficiency of internal combustion engines. One of these techniques is conversion of the WASTE thermal energy in the engine to mechanical or electrical energies. This investigation concentrated on simulation, examination and application of WASTE HEAT from exhaust gases of MTU-16V internal combustion engine in an organic Rankine cycle based on the efficiency of first and the second laws of thermodynamics. Using 862 kW power of exhaust gases WASTE HEAT, the net powers of working fluids including R600a, R600 and R245fa were evaluated and the highest net output power was calculated to be 37. 23 kW for R245fa working fluid. This working fluid increased the output power to approximately 2% and 6% in comparison with R600 and R600a fluids, respectively. Moreover, the mentioned working fluids were examined for volumetric flow rate and required volume contraction, where the lowest value was obtained for R600a. On the one hand, the effect of turbine inlet temperature on the volumetric flow rate, and effect of turbine inlet pressure on energy efficiency, exergy efficiency and irreversibility of the whole system were investigated. On the other hand, the influence of ambient temperature increase on irreversibility of each system component was studied. Based on the obtained results, R245fa fluid showed the best performance to be used in organic cycle from the viewpoint of the first and second laws of thermodynamics.

The WASTE HEAT management in heavy industry significantly increase productivity in this sector. Organic Rankine cycles (ORCs) are appropriate technology for the conversion of low quality thermal energy to electrical power. The Organic Rankine Cycle(ORC) applies the principle of the steam Rankine cycle, but uses organic working fluids with low boiling points can be used to recover HEAT from lower temperature HEAT sources. In this study the performances of three different organic Rankine cycles (ORCs) systems including the basic ORC (BORC) system, the single-stage regenerative ORC (SRORC) system and the double-stage regenerative ORC (DRORC) system using five different working fluids under the same WASTE HEAT condition are optimized by thermo-economic method using genetic algorithm. The results indicate that the R113 has the best performance between fluids. The optimized turbine inlet temperature and pressure in comparison with when exergy efficiency uses only, decreases. By changing basic Rankine cycle to the single-stage regenerative and the double-stage regenerative cycles, 12. 5% and 18. 75% change in specific power cost occurs respectively. Also results indicate that, as superHEAT degree in turbine inlet increases, the specific power cost increase and the exergy efficiency of system decreases.

This research proposes the combination of a dual-loop non-organic Rankine cycle (DNORC) with an internal combustion engine to increase the output power of the RECOVERY system by focusing on the increase in the energy input and system efficiency. In doing so, it investigates the strategy of increasing the mean effective temperature of HEAT addition in the high-temperature Rankine cycle (HTRC) (to improve the system efficiency and the strategy of increasing the WASTE HEAT entering the low-temperature Rankine cycle (LTRC) (to increase the energy input. In this RECOVERY system, by focusing on the RECOVERY of the WASTE HEAT from the engine cooling system and exhaust, the radiator can be removed from the engine cooling system, and by mounting fewer parts on the engine, not only can extra power be generated but also the engine can be cooled down faster and more efficiently. By using a thermodynamic analysis, the appropriate matching conditions between the DNORC with the engine are determined. The results showed that as the input energy increased, the RECOVERY rate and system efficiency also increased. The output power of the RECOVERY system exceeded 20kW and the efficiency of the whole engine and the RECOVERY system increased to 33%.

In this paper, the amount of HEAT WASTEd from different parts of a 12-liter compression ignition engine and the recoverable HEAT from these parts were investigated. Then, two-stage configuration of organic Rankine cycle was introduced for simultaneous HEAT RECOVERY from exhaust gases and coolant. Finally, parameters such as hybrid generated power, engine thermal efficiency, and brake specific fuel consumption were studied at different engine speeds under full engine load. By adopting this method, 35 kW hybrid power can be generated consequently, causing 9.5% reduction in brake specific fuel consumption.

In this research, a high-temperature Rankin cycle (HTRC) with two-stage pumping is presented and investigated. In this cycle, two different pressures and mass flow rates in the HTRC result in two advantages. First, the possibility of direct RECOVERY from the engine block by working fluid of water, which is a low quality WASTE HEAT source, is created in a HTRC. Secondly, by doing this, the mean effective temperature of HEAT addition increases, and hence the efficiency of the Rankin cycle also improves. The proposed cycle was examined with the thermodynamic model. The results showed that in a HTRC with a two-stage pumping with an increase of 8% in the mean effective temperature of HEAT addition, the cycle efficiency is slightly improved. Although the operational work obtained from the WASTE HEAT RECOVERY from the engine cooling system was insignificant, the effect of the innovation on the RECOVERY from the exhaust was significant. The innovation seems not economical for this low produced energy. However, it should be said that although the effect of the innovation on the increase of the RECOVERY cycle efficiency is low, the changes that must be implemented in the system are also low.