Pinch Point Temperature Difference In Evaporator Research Articles

Performance analysis and multi-objective optimization of organic Rankine cycle for low-grade sinter waste heat recovery

In order to enhance the sinter waste heat recovery (WHR) rate efficiently, the organic Rankine cycle (ORC) for power production was applied to take the low-grade sinter cooling flue gas (SCFG) expelled from the waste heat boiler as the heat source. The system thermodynamic, thermo-economic and multi-objective optimization models were constructed firstly, and then R245fa was chosen as the ORC working fluid. Furthermore, the variations of system thermodynamic and thermo-economic performances with the ORC thermal parameters under different inlet temperatures of SCFG were analyzed in detail, and the ideal parameter combination was established through the multi-objective optimization approach. The results show that, the optimal inlet temperature of SCFG is determined to be 160 °C, and under the aforementioned condition of inlet temperature of SCFG, the optimal ORC thermal parameters are determined to be 95 °C for the working fluid evaporation temperature, 10 °C for the working fluid superheat degree, 28 °C for the working fluid condensation temperature and 9 °C for the pinch-point temperature difference in evaporator by considering the system thermodynamic and thermo-economic performances comprehensively. Meanwhile, the WHR rate of SCFG under the above ORC parameter combination could reach 64.86 %, showing remarkable energy-saving effect.

Multi-objective optimization of low temperature cooling water organic Rankine cycle using dual pinch point temperature difference technologies

The performances of organic Rankine cycle (ORC) systems are significantly varied by the heat source temperature and cold source temperature which are correlated and can be well indexed by dual pinch point temperature difference (PPTD). In this study, multi-objective optimization of net output power, total thermal conductance and expander size parameter of a low temperature cooling water ORC system using thirty-eight working fluids with different PPTDs was investigated and presented. The results show that the PPTD in evaporator is more sensitive to the net output power, total thermal conductance and expander size parameter than the PPTD in condenser. The alkane dry working fluid decane exhibits the best overall performance with net output power of 15.8 kW, total thermal conductance of 41 kW/K and expander size parameter of 0.101 mm, followed by nonane and carbon-11. For the low temperature cooling water ORC system with a heat source temperature of 100 °C, the optimal PPTD in evaporator is in the range of 5–7 °C (the optimal values for most working fluids are 5 °C), and the optimal PPTD in condenser is in the range of 6–9 °C (the optimal values for most working fluids are 6 °C).

4E analysis of a modified multigeneration system designed for power, heating/cooling, and water desalination

Multigeneration systems, owing to their efficient fuel utilization, are recognized as one of the best technical and economical methods of energy saving and climate control. In this paper, a multigeneration system is proposed for the production of power, heating/cooling, and desalinated water. The proposed system was first studied by means of an energy, exergy, exergoeconomic, and environmental analyses and the obtained results were compared with that of multigeneration systems described in the literature (the selected multigeneration systems are based on a gas turbine cycle as prime mover). In addition, a parametric study was used to investigate the effects of primary thermodynamic quantities such as air pre-heater outlet temperature, pinch-point temperature difference in evaporator, evaporator temperature of cooling cycle, and evaporator temperature of desalination system on cycle performance. Results indicated that the proposed cycle’s power, heating, cooling, and desalinated water production is 30.5 MW, 40.8 MW, 1 MW, and 0.364 kg/s, respectively. In addition, the cycle’s total cost and total CO2 emissions are 1943.5 $/h and 0.163 kg/kWh. The parametric survey showed that the air pre-heater outlet temperature and the gas turbine inlet temperature are the most influential parameters in changing the system’s CO2 emissions. In this way, an increase of the pre-heater outlet temperature causes a 26% reduction in the cycle’s CO2 emissions, whereas an increase of the gas turbine inlet temperature leads to a 53% increase in CO2 emissions.

Techno-economic analysis of closed OTEC cycles for power generation

Abstract This study aims at offering a techno-economic evaluation of closed OTEC cycles for on-shore installations. A flexible Matlab® suite has been developed to identify plant design parameters (temperature difference of cold and warm seawater, pinch-point temperature difference of evaporator and condenser etc.) that guarantee the maximum value of γ (ratio between electricity output and heat exchangers area). The optimization model is able to handle different working fluids through the addition of specific correlations that consider fluid influence on heat transfer coefficients and turbine performance. Each plant component is technically analyzed and, in particular, plate heat exchangers were considered for evaporator and condenser and sized accurately with Aspen EDR®, while expander was analyzed with the in-house code Axtur. For warm seawater temperature of 28 °C and cold seawater temperature of 4 °C (8500 kg/s taken from 1000 m depth), ammonia cycle is the best solution characterized by efficiency equal to 2.2% and net power output equal to 2.35 MWe. The obtained LCOE (269 €/MWhe) confirms how OTEC technology is not ready to compete in energy market. Nevertheless, remote zones (i.e. small islands archipelagos), which are often characterized by high electricity price, represent interesting scenarios where OTEC technology could be a promising alternative to conventional power production technologies.

Determining the optimal pinch point temperature difference of evaporator for waste heat recovery

From the perspective of exergy recovery, the pinch point temperature difference (PPTD) of evaporator for waste heat recovery has been optimized by exergo-economic principle using the annual net profit per transferred heat load as objective function. And for comparison, another criterion, the annual total cost per transferred heat load from the view of exergy destruction, is introduced. Taking organic fluid R600a as an example, the effects of thermodynamic and economic parameters on the optimal PPTD are examined. It is found that the optimal PPTD is closely related to the total investment costs of evaporator. Different trends on the optimal PPTD are provided with the variations of thermodynamic and economic parameters. And the flow exergy loss has little impact on the optimal PPTD of evaporator. The optimal PPTD from the perspective of exergy recovery is larger than that from the view of exergy destruction.

Economical evaluation and optimization of subcritical organic Rankine cycle based on temperature matching analysis

This paper presents an economical evaluation and parametric optimization on subcritical ORC (organic Rankine cycle) system for recovering the low-temperature waste heat of flue gas which is released from industrial boilers. First, the effects of the PPTD (pinch point temperature difference) in evaporator and condenser, and evaporating temperature on the system performance are examined with the EPC (electricity production cost) as the evaluation criterion. The optimal evaporating temperature, PPTDs in evaporator and condenser, as well as condensing temperature corresponding to the minimum EPC are provided simultaneously for the subcritical ORC system under different heat source temperatures. Then, the optimal parameter values are compared for nine potential organic working fluids with the critical point temperature from 124 °C to 235 °C. Results show that there exists a possible relationship between the critical temperature of working fluids and the economical performance of the system. Furthermore, it is suggested that the working fluids including R123, n-pentane, R11 and R141b, whose critical temperature range from 180 °C to 210 °C, are preferable for recovering the low-temperature waste heat of flue gas.