Condenser Outlet Temperature Research Articles

High-fidelity model development of CO2 booster refrigeration systems in supermarkets using field measurements

Supermarket refrigeration systems adopting traditional refrigerants with high global warming potential (GWP) have impacts on global warming for indirect and direct greenhouse gases (GHG) emissions. CO2 is a popular low-GWP alternative. The transcritical operation of CO2 systems worsens their energy performance, but provides recoverable heat as a heat source to reduce gas consumption. To evaluate operation performance, data-driven models, trained by historical data, are weak in implementation with datasets outside the scope of training data; in contrast, theoretical models have better extrapolation ability to calculate all operation conditions of CO2 systems at supermarket. Existing theoretical modeling approaches often lack validation against the limited public-access data, which reduces model reliability for further applications, and adopt oversimplified inference methods for unmeasured variables, which increases the risks of breaking thermodynamic laws and lowering model accuracy. This study therefore develops a steady-state theoretical model for CO2 booster refrigeration systems validated against field measurements from three UK supermarkets. The available measurements are utilized to the best level to ensure model accuracy and physical interpretability. Proposed methods to infer missing variables in CO2 systems include condenser outlet temperature, evaporating temperature, compressor isentropic efficiency and compressor mass flow rate. Results show that proposed inference methods enhance the abilities of the proposed modeling approach to ensure data integrity, avoid breaking thermodynamic laws, and improve model accuracy by reflecting real-time actual values of unmeasured variables rather than rough assumptions. The proposed modeling approach provides satisfactory accuracy validated using high-resolution measurements across the whole year from three real supermarkets.

EXPERIMENTAL STUDY OF DOMESTIC REFRIGERATOR BY USING EVAPORATIVE CONDENSER

Refrigerator has become an essential commodity rather than luxury item. It is one of the home appliance ukkigg, vapour compression cycle in it process. Performance of this system becomes main issue and many researches are still ongoing to evaluate and improve efficiency of the system. This study presents effect of evaporative condenser on COP of domestic refrigerator. The purpose of this article is to compare the COP of refrigerator by using air cooled condenser and evaporative condenser of same length and same diameter. This experiment is carried out on domestic refrigerator (185 ikr4 test rig. In this study, an innovative, evaporative condenser for residential refrigerator was introduced. A yaw compression cycle incorporating the proposed evaporative condenser was tested to evaluate the cycle performance. To allow for evaporative cooling, sheets of cloth were wrapped around condenser to suck the water sprayed on it. The thermal properties at the different points of the refrigeration cycle were measured for typical operating conditions. Further to compare both the condensers some parameters like condenser outlet temperature, evaporator inlet temperature, power consumption have taken. After investigation it was found that evaporative condenser may replace the air cooled condenser from domestic refrigerator KEYWORDS: Refrigerator, Condenser, Evaporator, COP, Refrigerating Effect, Compressor.

Investigation of a novel scheme utilizing solar and geothermal energies, generating power and ammonia: Exergoeconomic and exergoenvironmental analyses and cuckoo search optimization

The integration of solar and geothermal energy sources presents a promising avenue for enhancing the efficiency and output of energy systems. This research introduces a novel hybrid system combining solar and geothermal energy for the co-generation of power, cooling, and ammonia. The proposed system integrates several cycles and technologies, including an organic Rankine cycle, an ejector refrigeration cycle, an organic flash cycle, a proton exchange membrane electrolyzer, and an ammonia synthesis reactor. Through a comprehensive 4E (energy, exergy, economic, and environmental) analysis, utilizing thermodynamic, exergoeconomic, and exergoenvironmental methodologies, this study evaluates the system's performance. The findings reveal that solar collectors are the primary contributors to system irreversibility, accounting for 78 % of the total. Notably, an increase in the condenser outlet temperature significantly decreases the cooling load, whereas elevating the turbine 1 exit pressure enhances overall power production. At optimal operating conditions, the system generates a net power of 104 kW, provides 26.07 kW of cooling capacity, and produces 3.55 kg/h of ammonia. This performance translates into a product cost of 1.193 USD/h and an exergoenvironmental impact rate of 25.31 mPts/h, alongside achieving an exergy efficiency of 9.34 %. Financially, the system promises a payback period of 2.34 years and a net present value of 1.259 million USD, highlighting its economic viability and environmental benefits.

Experimental comparison and seasonal performance evaluation of different scroll compressor capacity modulation methods in an R410A water to water system

Rising cooling needs for the residential and commercial air conditioning sectors and the demand for higher SEER require HVAC&R to handle cooling loads below the design condition. Although several studies exist focusing on a particular capacity modulation strategy, there is no extensive study that explores all these available modulation strategies in the same experimental facility. This study experimentally compared a single speed, a two-stage compressor, tandem combinations of two single speed compressors, a single speed and two-stage compressor, and a variable speed compressor using the same R410A water ethylene glycol (WEG) system for cooling application. These modulation strategies were tested according to AHRI Standard 551/591 (2020), and their seasonal performance is given by Integrated Part Load Value (IPLV.SI). A two-stage compressor with lower LMTD at the heat exchangers and a single speed compressor with higher isentropic efficiency have the same performance at one of the part load conditions. Additionally, a single speed compressor with an improved compressor motor has a 3% higher IPLV.SI than a two-stage compressor with the baseline motor. Different methods of interpolation that are available when the capacity is in between two compressor stages of operation were discussed. The tandem combinations with different number of stages have the same seasonal performance, showing that not all the stages available might be useful. The variable speed compressor with the best IPLV.SI was selected to further study the performance under heating application using EU 14825 (2013) standard with constant and variable condenser outlet conditions. For heating application, variable speed compressor with a wider range of modulation is recommended when selecting the compressor for variable condenser outlet temperature conditions while it might not be the best option due to compressor operating envelope limitation when operating with constant condenser temperature outlet.

Energy, exergy, economic, and environmental analysis of a high-temperature heat pump steam system

Industrial steam is widely recognized as a valuable form of heat currency, possessing considerable social and economic significance. As the industry shifts to low carbon emissions, there is an urgent need to reduce CO2 emissions from industrial steam generation. The analysis of a high-temperature heat pump steam system (HTHPSS), which recovers industrial waste heat to produce high-temperature steam at 170 °C, includes evaluations of its energy, exergy, economic, and environmental (4E) to determine whether it can replace a coal-fired boiler. The economic analysis considered the recovery value of waste heat and the effect of CO2 trading prices. Optimization calculations were performed to investigate changes in the waste heat temperature and condenser outlet temperature. The study also offers recommendations for operational conditions and optimization strategies for the HTHPSS. The results indicate a positive correlation between the system coefficient of performance (COP) and the waste heat utilization rate with waste heat temperature and condenser outlet temperature. The maximum COP value is 2.73. The total exergy efficiency initially increases and then decreases as waste heat temperature increases. It also decreases as the condenser outlet temperature increases, reaching a peak value of 43.26 %. The waste heat temperature needs to be at least 59 °C to generate a net profit, with a corresponding payback period (PBP) of 4.40 years. The minimum PBP is 0.03 years, independent of waste heat temperature. The annual emission reduction increases as waste heat temperature increases and decreases as condenser outlet temperature increases. These results indicate that a HTHPSS could replace a coal-fired boiler and offer guidance for design optimization.

OTEC PERFORMANCE EVALUATION USING DIFFERENT WORKING FLUIDS AND VARIATIONS IN OPERATING ORC CONDITIONS

Ocean Thermal Energy Conversion (OTEC) is a system that produce energy of electricity by exploiting the temperature difference between surface part of seawater and deep region of seawater. The thermal energy at the surface seawater is used to convert working fluid into vapor which expands in the turbine to generate electricity and revert into liquid state by rejecting heat to cold seawater pumped from deep region of seawater. Basically, there are various types of working fluids that can be applied in an OTEC system depending on its contribution towards the performance of the system. In this study, the thermodynamics efficiency and net power output of basic OTEC system will be evaluated by varying three parameters which are the turbine inlet temperature, turbine inlet pressure and condenser outlet temperature using various working fluids through simulation using MATLAB. Simulation results indicate that R717 excels in producing the highest net power output but R600a has the best average value in thermodynamic efficiency. The findings of this work can contribute in giving an insight on which working fluid has the optimal characteristics in obtaining the best performance of the OTEC system.

Performance evaluation of an auto-cascade refrigeration system using grey correlation theory and response surface methodology

This article focuses on evaluating and analyzing the performance of an autocascade refrigeration system with the zeotropic mixture of R600a/R1150/R14 refrigerants using grey correlation theory and response surface methodology (RSM). The correlation degree among various factors is analyzed using grey correlation theory. The interactive influences that have significant impacts on the six output parameters are illustrated, and a regression model is further validated by five confirmation parameters. The results show that the vapor quality of the evaporator outlet is the greatest factor that affecting the refrigerating capacity and coefficient of performance (COP). However, the evaporation temperature has the greatest effect on compressor’s discharge temperature, pressure ratio, exergy destruction rates, and exergy efficiency. Lower vapor quality of the condenser outlet and condensation temperature can improve the performances of refrigerating capacity, COP, compressor’s discharge temperature, compression ratio, total exergy destruction rate, and exergy efficiency based on the RSM results. The random five groups of validation parameters indicate that the errors between the predicted modeling and calculation results are all less than 5%, demonstrating that the RSM model has good predictability. The results achieved in this work will assist in the optimizing analysis and the application of cryogenic refrigerators.

Vehicle refrigeration modification using an ejector: Optimization and exergoeconomic analysis

BackgroundAdvances in technology in recent years have increased energy consumption which has led to global warming. In line with the Paris agreement, the optimal use of energy is a way to overcome the issue. Air conditioning and refrigeration systems are among the sectors that account for a large share of energy consumption. This has elicited the implementation of optimization of refrigeration systems. MethodIn this research, the aim is to utilize the radiator waste heat of an engine with a volume of 2000 cc in an ejector refrigeration cycle as an alternative to conventional refrigeration cycles in vehicles. For this purpose, the ejector refrigeration cycle is modeled with energy, exergy, and eco-exergy equations and the ejector is modeled with dynamic gas equation. After modeling, effective parameters, namely, condenser outlet temperature, inlet temperature and pressure to the secondary nozzle, and inlet temperature to the primary nozzle are optimized using TOPSIS multi-objective optimization method. The selected objectives were reducing system capital investment cost, and increasing, COP, and the ejector performance (ω) criterion. ResultsIt was found that the ejector refrigeration cycle reduces the electric power and capital investment cost by 0.743 kW and 0.0028 $/h, respectively, and also increases the COP by 0.917 compared to the conventional refrigeration systems in the vehicle.

Experimental study of electronic expansion valve opening on the performance of electric vehicle heat pump system at different compressor speeds

The good matching of the electronic expansion valve (EXV) opening and compressor speed in an electric vehicle heat pump air conditioning system is significant for improving the whole system performance. The matching of EXV opening and compressor speed and its effect on system performance was experimentally investigated and analyzed. The results showed that at various compressor speeds, the condensing pressure increased and the evaporating pressure decreased to a small extent with the decrease of EXV opening, thus increasing the pressure ratio. The condensing pressure had a jump phenomenon at a specific EXV opening, and the corresponding jump opening was different at each compressor speed. The COP reached the optimal values of 2.4, 2.6, and 2.1 at the EXV opening of 110, 100, 90 steps, respectively, due to the synergistic effect between compressor speed and EXV opening. Moreover, it was found that the changing trend of COP was consistent with that of condenser outlet temperature. The compressor speed and EXV opening had a more significant impact on condensing pressure than evaporating pressure. The influence of compressor speed on each performance parameter was greater than that of EXV opening, while the EXV opening significantly influenced the subcooling degree. Under different compressor speed conditions, changing the single adjustment step of EXV according to the influence of EXV on each parameter can realize the rapid and accurate control of the heat pump system performance, which can provide a reference for the formulation of relevant control strategies and the reduction of the system energy consumption.

Proposal and performance study on a component-based double-stage compression auto-cascade refrigeration cycle

It is difficult for the conventional single-stage compression auto-cascade refrigeration cycle to achieve higher refrigeration efficiency and lower refrigeration temperature, because the stream rich in high boiling point component from the phase separator bottom undergoes a single-stage compression process of high pressure lift ratio. Based on the concept of the evaporating temperature of the high/low boiling point component matching the grade compression of two streams from the phase separator, a component-baseddouble-stagecompressionauto-cascaderefrigeration (CDACR)cycle using R170/R600a is proposed in this paper. In the novel cycle, one dedicated compressor with two suction ports is used as the substitute for a conventional compressor with the sole suction port to realize grade compression process of the component of the refrigerant mixtures, and the stream enriched with high boiling point component from the separator bottom is sucked into the high-pressure suction port and undergoes the low-pressure-lift-ratio compression process, while the stream rich in low boiling point component from the separator top is sucked into the low-pressure suction port and executes the high-pressure-lift-ratio compression process, so as to cut down the compressor power consumption and obtain a lower refrigeration temperature. The mathematical model of the proposed cycle is developed to evaluate the thermodynamic performance of the system and comparisons with the conventional single-stage compression auto-cascade refrigeration (SCACR) cycle are also discussed. The results indicate that application of the component-based grade compression to the conventional auto-cascade refrigeration cycle dramatically improves the performance of the CDACR cycle, and there is optimum composition ratio of refrigerant mixtures for the CDACR cycle to obtain the highest coefficient of performance (COP). It is also shown that the performance of the CDACR cycle is significantly better than that of the SCACR cycle. As compared with those of the SCACR cycle, the compressor power consumption of the CDACR cycle decreases by 44.83%-53.17%, and its COP increases by 0.34–0.43, as the evaporating temperature at the evaporator outlet ranges from −60°C to −40°C. In addition, at the condenser outlet temperature in the range of 26°C- 40°C, the compressor power consumption for the proposed cycle is 37.74%-47.03% lower than that for the SCACR cycle, while COP of the CDACR cycle is 0.29–0.42 higher than that of the SCACR cycle.

Thermodynamic investigation of a single flash geothermal power plant powered by carbon dioxide transcritical recovery cycle

The use of new energy sources, such as geothermal energy, is rapidly expanding worldwide, and it is a viable alternative to fossil fuels. This paper proposes a geothermal power generation system (combined single flash geothermal cycle with transcritical carbon dioxide recovery cycle). To improve system performance, a recuperator is used to recover some of the heat loss. The proposed system simulation is performed in EES software and then validated by previous research. The proposed system is analyzed from the perspective of energy and exergy. The effects of the proposed system separator pressure, carbon dioxide turbine inlet pressure and carbon dioxide condenser outlet temperature on energy efficiency, exergy efficiency and system net power output have been investigated. Findings show that the proposed system in recovery mode has a net power output of 401.40 kW, energy efficiency of 53.6 percent, and exergy efficiency of 46.32 percent, which are significantly higher than the basic mode’s values of 149.9 kW, 2.39 percent, and 12.12 percent, respectively.

Thermal design and analysis of an organic rankine cycle system utilizing the main engine and cargo oil pump turbine based waste heats in a large tanker ship

The utilization of main engine-based waste heat sources using organic Rankine cycle (ORC) systems is only available during the navigation phases of marine vessels, which leads to reductions in the system uptake time and economic viability of the investment during cargo loading/discharging operations and waiting periods in ports. The novel perspective of this study is to propose the cargo oil pump turbine (COPT) based waste heat as a utilizable source, which has not been introduced in the literature yet, and show the economic viability of ORC systems for tanker ships. In this regard, a new waste heat recovery system specifically designed for a reference crude oil tanker ship was introduced that can utilize both main engine-based waste heat during navigation and COPT-based waste heat during cargo discharge operations. The optimal heat exchanger network of the main engine and COPT-based waste heats was designed using pinch point analysis method for achieving optimum waste heat recovery. Energy and exergy analyses were conducted for the proposed ORC integrated waste heat recovery system for both navigation and discharge operation modes of the ship. The economic performance of the ORC system was further assessed by calculating payback periods and levelized energy costs for eleven design points. The highest energy conversion efficiency (16.2%) was achieved when the ORC condenser outlet temperature was taken as 15 °C for R1233zd(E). COPT based waste heat reduced the levelized energy cost of the system by at least 8.9% and the minimum levelized energy cost value was obtained as 0.1307. The best economic performance was yielded with COPT utilization at design point 9 with a payback period of 6.2 years, which was reduced by at least 0.7 years with the utilization of COPT based waste heat.

Performance modelling and optimization of three vacuum-enhanced membrane distillation modules for upscaled solar seawater desalination

Membrane distillation using multi-envelope modules in vacuum enhanced air gap (V-AGMD) operation has been demonstrated as the best alternative to the current thermal desalination technologies. This work presents for the first time the use of response surface methodology (RSM) to model and validate the performance of V–AGMD operation for seawater desalination in three multi-envelope modules with different internal designs. Permeate productivity (PFlux) and condenser outlet temperature (TCO) were modelled and validated from results obtained in steady-state experiments, considering the evaporator inlet temperature, the condenser inlet temperature, and the feed flow rate as inputs. To gain accuracy in the estimations of thermal efficiency regarding previous works, a novel strategy was applied, consisting in calculating the specific thermal energy consumption (STEC) using the models of PFlux and TCO, developed from direct measurements. The models of the three modules were used to search the optimal operating conditions that minimize the levelized cost of water (LCOW) in a large-scale MD plant under different scenarios. Different costs of thermal and electrical energy were considered and their influence on the number of modules required in the facility was also discussed.

Investigation and optimization of a two-stage cascade ORC system for medium and low-grade waste heat recovery using liquefied natural gas cold energy

This study proposed a two-stage cascade organic Rankine cycle (ORC) to harvest the medium and low-temperature discharged heat from internal combustion engine (ICE), and a liquefied natural gas (LNG) cold energy system is integrated into the proposed cycle in order to realize the cascade utilization of ICE multi-grade waste heat more efficiently. The thermodynamic and economic models are developed to investigate the proposed system performance under steady-state conditions. The influence of the important thermodynamic parameters, e.g. the ORC turbine inlet temperature, the high pressure of first-stage ORC and the outlet temperature of condenser are investigated. The calculated results indicated that the thermal efficiency and the exergy efficiency achieved 27.31% and 33.73%, respectively. In addition, it was found that the total sum unit cost of system product was decreased by increasing turbine Ⅰ inlet pressure. Furthermore, to reach the conflicting compromise between the two aspects of thermodynamic and economic, the Non-dominated Sorting Genetic Algorithm (NSGA-II) is employed to carry out the multi-objective optimization study by which the external investment cost and the thermal efficiency are selected as the objective function. At the same time, the influence region of decision variables related to the optimization is determined according to the scatter distribution of decision variables. Moreover, the exergy destruction and the investment cost ratio of each component under the optimization conditions are analyzed to obtain the preferred performance of the key components. The findings could provide references for the ORC system design and operation driven by multi-grade waste heat.

Assessment and working fluid comparison of steam Rankine cycle -Organic Rankine cycle combined system for severe cold territories

In this work, organic Rankine cycle (ORC) is employed to expand the available temperature region of the conventional steam Rankine cycle (SRC) in severe cold territories. The feasibility of the proposed steam Rankine cycle -Organic Rankine cycle combined system is investigated and verified. Working fluids are compared and screened, the matching scheme of different working fluids suitable for different working conditions and objects (thermodynamic or economic performance) are obtained. The results show that the net power increment (NPI) of the combined system increases with the decrease of the condenser outlet temperature (CT). The NPI of ORC system can be effectively improved by adding a regenerator. For wet working fluids, when the evaporating pressure of ORC system is close to the critical pressure of working fluid, there exists an optimal superheat degree with maximum NPI of the system. The combined system using ammonia and R600 as working fluid has the largest NPI values. When the CT of SRC is higher than 90 °C, the Rankine cycle using ammonia as working fluid has better performance. When the CT of SRC is less than 90 °C, the regenerative ORC system using R600 as working fluid has a better performance.

An extensive thermo-economic evaluation and optimization of an integrated system empowered by solar-wind-ocean energy converter for electricity generation – Case study: Bandar Abas, Iran

In parallel with efforts to shift human societies' reliance from fossil fuel to renewable resources, in this paper, three green-based energy generation configurations were proposed and examined thermoeconomically. Afterwards, the one with the highest performance was selected for further investigation. The chosen system was empowered by an ocean thermal energy convertor (OTEC), a wind turbine, and a solar flat plate panel. The system was modeled by Engineering Equation Solver (EES) software to conduct sensitivity analysis by assessing the impact of changes in objective parameters on the net power output, thermoelectric generator (TEG) power output, exergy efficiency, and cost ratio. In the following steps, EES was coupled with MATLAB through Dynamic Data Exchange (DDE), and a non-dominated sorting genetic algorithm (NSGA-II) was employed for optimizing design parameters including solar panels' area, organic Rankine cycle (ORC) turbine inlet temperature, condenser outlet temperature, ORC pump and turbine efficiency, TEG figure of merit, and evaporator pinch point to reach the highest possible exergy efficiency and the least amount for cost ratio. The system performed with 13.88% exergy efficiency. The exergy destruction analysis showed wind turbine was the most exergy destructor in the system. The configuration is able to generate 448 kW power at its optimal point. Eventually, a case study for Bandar Abbas city, a coastal town in the south of Iran, is carried out to investigate the system's performance concerning the region's potential throughout a year. The results indicate that the system can potentially supply 38 Iranian households with electricity all year-round.

Experimental evaluation on a centralized air conditioning system embedded with a split-type air conditioner as a dedicated subcooler

Dedicated subcooling (DS) is one of the alternative methods to gain significant performance improvement in the air conditioning (A/C) system. However, DS increases the investment cost and the performance improvement depends on the capacity ratio between the subcooler and the main A/C system (RSM). As compared to previous studies, the present study investigates experimentally the performance of the A/C system equipped with DS at smaller RSM, and justify the economic advantage of the proposed system. The experimental study was conducted at constant outdoor, evaporation, and condensation temperatures of 30, 5, and 40°C, respectively. The experimental facility consists of a main A/C system with a compressor capacity of 11.25 kW and R22 as a working fluid. The sub-system is a split-type A/C system with compressor capacity of 0.75 kW and R290 as a working fluid. Four parameters; the degree of subcooling, cooling capacity, input power, and coefficient of performance (COP) were investigated. The results showed that the DS decreased the condenser outlet temperature , thus led to an average increase in degree of subcooling by 3.4°C. Consequently, cooling capacity of the main system increased by 1.4 kW, and the input power of the entire system (power consumed by the main and subcooler systems) decreased by 0.4 kW. As a result, the COP raised by 7.8%, as compared to system without DS. In the economic point of view, the analysis showed that the system with DS is economically viable and has a huge potential due to short payback period of just 11.81 months. • Residential air conditioner as a sub-system in producing dedicated subcooling. • The ratio on capacities of subcooler to main system determine the degree of subcooling of the main system. • The dedicated subcooling increases the cooling capacity and decreases the input power of the main system. • The COP increases when the power used by both the main and subcooler systems are considered. • Simple payback period of 11.81 months is expected for system with DS as compared to system without DS.

Energy and exergy analysis of a Linde-Hampson refrigeration system using R170, R41 and R1132a as low-GWP refrigerant blend components to replace R23

This study presents a comprehensive comparative analysis of the thermodynamic performance of a single-stage Linde-Hampson refrigerator (LHR) for refrigerant couples, namely R1234yf + R170, R1234yf + R23, R1234yf + R41 and R1234yf + R1132a, to seek the most suitable substitute for R23 at the temperatures down to −60 °C. The compressor input power, cooling capacity, coefficient of performance, exergy loss and exergy efficiency are selected as the objective functions. The operating parameters include the evaporation temperature, suction pressure, and condenser outlet temperature. The compositions of each binary mixture were obtained from the vapor-liquid equilibrium behavior according to the suction pressure and target evaporation temperature. Simulation and comparative study show that better energy and exergy performance are obtained with all the replacements under all studied conditions compared to R23. Further results show that the R1234yf + R41 mixture performs better, and hence is suggested as the most promising alternative couple for the single-stage LHR at −60 °C. By properly increasing the suction pressure and decreasing the condensation temperature, the system performance can be enhanced. This indicates that a multi-objective scheme has the potential to significantly improve the performance of low-temperature applications.

Comparative environmental impacts and emission reductions of introducing the novel organic Rankine & Kalina cycles to recover waste heat for a roller kiln

Abstract In order to simultaneously utilize the flue gas and cooling gas of a roller kiln, the novel organic Rankine (ORC) & Kalina cycles (KC) with parallel double-evaporator (PD) including PD-BORC, PD-RORC, PD-KC11 and PD-KC34 are introduced for the waste heat recovery. To evaluate the environmental influences performance for the recommended thermodynamic cycles, environment impact loads and emission reductions analysis are employed from the life-cycle perspective. Also, to select a more environmentally friendly model, the system environmental influences based on thermodynamic, economic, environmental and watery criteria are investigated. Results show that under the four criteria, the pump contribute mostly to GWP (global warming potential), AP (acidification potential), EP (eutrophication potential) and HTP (human toxicity potential), evaporation unit is dominant in POCP (photochemical ozone creation potential) and SWP (solid waste potential), and both evaporation unit and pump have the main influence on SAP (soot and dust potential). Meanwhile, operation phase makes the greatest contribution to GWP, AP and HTP, construction phase has the greatest influence on POCP and SWP, and construction and operation phases account for the largest proportion of EP and SAP. It can also be concluded that SAP has the most serious impact on the environment while POCP is the least significant factor. Besides, from the perspective of environment impact load, PD-BORC is the best selection, and the system design based on environmental criterion has the minimum value. Also, in terms of the emission reduction, PD-KC34 is the priority selection, and the maximum emission reduction can be achieved under thermodynamic criterion. Furthermore, the reduction ratio of environment impact load can be increased with increasing the evaporator inlet temperature, decreasing the condenser outlet temperature, increasing the superheat degree (PD-ORCs) and decreasing the superheat degree (PD-KCs), and decreasing the ammonia concentration (PD-KCs).

Analysis on full CO2 capture schemes in NG/O2 combustion gas and steam mixture cycle (GSMC)

The nature gas and pure oxygen (NG/O2) combustion gas and steam mixture cycle (GSMC) is a novel power generation cycle using NG/O2 combustion product and circulation H2O as the turbine working medium, which can implement efficient power generation, CO2 capture and energy shifting. In GSMC, cold energy of liquefied natural gas (LNG) and liquefied oxygen (LO2) is used for CO2 capture. The CO2 capture schemes are analyzed to improve the CO2 capture as well as the system efficiency. The main means to increase the CO2 capture and extend CO2 full capture range include the reduction of CO2 liquefaction enthalpy drop and the conservation of cooling energy consumption in CO2/moisture separation. Lower efficiency is always a penalty of the full CO2 capture especially with higher condenser outlet temperature. The optimal scheme is different under different conditions such as parameters of turbine inlet, cooling water, and CO2 liquefaction. At turbine inlet of 30MPa/1000 °C and condenser outlet of 18kPa/38 °C, the efficiency drop is 1.18% for the full CO2 capture of the improved scheme, while the CO2 capture ratio of the original GSMC scheme is less than 60%. The distinctive CO2 capture of GSMC is summarized as system indispensable, scheme optional and method promotable.