Engineering Equation Solver Software Research Articles

Enhancing the performance of heat pumps by immersing the external unit in underground water storage tanks

Renewable energy sources have a considerable potential to contribute to sustainable development and have the potential to reduce the reliance on fossil fuels. Direct-Expansion Water Source Heat Pump (DX-WSHP) could be used in air conditioning applications as an energy-efficient environmental-friendly system. In this study, DX-WSHP potential for air conditioning of a multi-level residential building was numerically examined. A closed-loop of copper pipes filled with R134a, as a refrigerant, was immersed in an underground water tank that is used as a heat sink/source. Cooling/Heating loads of the residential unit under three different climate conditions were estimated at different floor levels. The proposed system takes advantage of a higher heat transfer rate in water and better thermal performance when compared with traditional Air Source Heat Pumps (ASHP). A mathematical model was built to examine the performance of the system using the Engineering Equations Solver (EES) software. Results have shown that the DX-WSHP has outperformed the ASHP at a lower (higher) condensing (evaporating) temperature in the cooling (heating) mode with higher values of COP varies from 30% to 118%. Furthermore, there was a significant reduction in economic and environmental impacts, CO2 emissions, and electrical energy consumption of the DX-WSHP system for the three different climate conditions. The reduction in CO2 emissions varied from 8% to 40%. Additional advantages of the proposed system were found: energy-saving and overcoming the problems concerning heat rejection to the surrounding air and the outdoor fan noise.

Assessment of thermal performance improvement of GT-MHR by waste heat utilization in power generation and hydrogen production

The Gas Turbine Modular Helium Reactor (GT-MHR) uses two compression stages to compress the helium and a pre-cooler and an intercooler to reduce the compressors inlet temperature, that dissipate around 308.36 MWth at the design operational conditions. This dissipated thermal energy can be used as an energy source to produce hydrogen. An energy analysis is conducted for a proposed system that includes GT-MHR combined with Organic Rankine Cycle (GT-MHR/ORC) and a Proton Exchange Membrane (PEM) electrolyzer (GT-MHR/ORC-PEM) for hydrogen production. The optimum operating parameters values of the new cycle are obtained using the Engineering Equation Solver (EES) software. Thermal efficiency has been improved from 48.6% for the simple GT-MHR cycle to 49.8% for the new combined (GT-MHR/ORC-PEM) cycle including hydrogen production at a rate of 0.0644 kg/s at the same operating conditions. However, the thermal efficiency for the combined GT-MHR/ORC was higher and reaches 50.68%. Moreover, a parametric study is carried out over a wide range of some operating conditions such as turbine inlet temperature, Compressor pressure ratio and compressor inlet temperature to investigate their effect on the new cycle performance. Results revealed that increasing the low-pressure compressor inlet temperature increases the amount of hydrogen produced while decreasing thermal efficiencies for the three cycles. Furthermore, increasing compressor pressure ratio reduces the mass flow rate of hydrogen produced util it reaches a minimum value then it starts to increase slightly, on the contrary, an opposite relationship is observed between thermal efficiencies and compressor pressure ratio. Moreover, at low compressor pressure ratio, the rate of hydrogen produced increases with increasing turbine inlet temperature; however, it decreases by increasing the turbine inlet temperature at high compressor pressure ratio. Nevertheless, a direct correlation is noticed between thermal efficiencies and turbine inlet temperature.

Thermodynamic Analysis of Hydrogen Production by a Thermochemical Cycle Based on Magnesium-Chlorine

Most thermochemical cycles require complex thermal processes at very high temperatures, which restrict the production and the use of hydrogen on a large scale. Recently, thermochemical cycles producing hydrogen at relatively low temperatures have been developed in order to be competitive with other kinds of energies, especially those of fossil origin. The low temperatures required by those cycles allow them to work with heats recovered by thermal, nuclear and solar power plants. In this work, a new thermochemical cycle is proposed. This cycle uses the chemical elements Magnesium-Chlorine (Mg-Cl) to dissociate the water molecule. The configuration consists of three chemical reactions or three physical steps and uses mainly thermal energy to achieve its objectives. The highest temperature of the process is that of the production of hydrochloric acid, HCl, estimated between 350-450℃. A thermodynamic analysis was performed according to the first and second laws by using Engineering Equation Solver (EES) software and the efficiency of the proposed cycle was found to be 12.7%. In order to improve the efficiency of this cycle and make it more competitive, an electro-thermochemical version should be studied.

Investigation of a solar hydrogen generating system design for green applications

This study presents a unique dome photoanode design that can harvest the maximum delivered sun rays over the daytime due to its specific dome design to enhance the solar to hydrogen energy efficiency and improve the hydrogen mass generation rate. The photoanode and cathode domes are placed in a potassium hydroxide electrolyte inside two cylindrical vessels. The coupled electrochemical, exergy, energy, as well as fluid flow analyses, are conducted to examine the proposed photoelectrochemical cell designs using both COMSOL and Engineering Equation Solver software packages. The electrochemical process equations are simulated extensively to investigate the impacts of changing the illuminated electrode surface area, quantum efficiency, solar radiation intensity, and photocurrent density upon the corresponding energy efficiency as well as hydrogen generation rate. The thermodynamic balance equations are also developed to predict the exergy and energy for all inputs and outputs. The impact of electrolyte flow circulation on the oxygen bubble formation is formulated in a way to prevent the bubble coverage phenomenon. The numerical results showed that the hydrogen mass generation rate and solar to hydrogen efficiency are 26.16 μg/s and 4.38%, respectively, which happens at 600 W/m2 of solar irradiance, 10% quantum efficiency, and 569 cm2 illuminated electrode surface area. The maximum mass-based hydrogen generation rate and the overall energy efficiency, which are found to be 55.20 μg/s and 6.69%, are achieved at a 800 cm2 illuminated photoanode surface area, a 600 W/m2 solar radiation intensity, a 3.3 mA/cm2 current density, and a 10% quantum efficiency.

Sensitivity analysis of a novel geothermal multigeneration system with liquefied natural gas, proton exchange membrane, absorption refrigeration system, and water desalination

Renewable energy, such as geothermal, is very effective in reducing the effects of greenhouse gas emissions. Therefore, a geothermal-based multi-generation system can produce commodities for power, hydrogen, liquefied natural gas, cold energy recovery, cooling, and water desalination. Power the multigeneration, energy, and exergy analyses are conducted using Engineering Equation Solver (EES) software. Constraints used are a steam fraction, geothermal temperatures, and MER (mass extraction ratio). Sensitivity analysis is given to the parameters of exergy efficiency, net output power, a mass flow rate of natural gas, a mass flow rate of hydrogen, a mass flow rate of pure water, and the coefficient of performance of the absorption refrigeration system. Thermal efficiency is 27.2%. Exergy efficiency is 35.89%. The net power output from turbine 1 is 997.8 kW, from turbine 2 is 343.2 kW. The hydrogen mass flow rate is 0.0008 kg/s. The natural gas mass flow rate that can be used is 1.252 kg/s. The coefficient of performance (COP) of the absorption refrigeration system (ARS) is 0.8876, and the mass flow rate of pure water of the water desalination system is 0.3914 kg/s.

Development of a multigenerational energy system for clean hydrogen generation

The existing fueling options for many power plants are still dependent primarily on fossil fuel resources, which in return cause serious local and global environmental problems. Therefore, in order to reduce the detrimental effects of greenhouse gas emissions, the use of cleaner production methods has been accelerated to develop and implement environmentally- friendly energy systems. In this regard, the combination of renewable energy systems and hydrogen production methods will definitely play a crucial role in the energy sector’s transition to a carbon-free production. In order to make the use of geothermal energy cleaner and more sustainable, some obstacles need to be eliminated. Most importantly, the hydrogen sulfide emissions may cause serious concerns in public acceptance of geothermal power plants. In the current study, solar, wind and geothermal energy resources are integrated to develop an integrated renewable-based energy system with a key objective of higher environmental and system performance. The underlying motivation is to propose a model which consists of a hydrogen sulfide abatement unit and an electrolyzer to produce hydrogen from hydrogen sulfide and hence eliminites the hydrogen sulfide emissions. A detailed thermodynamic analysis is carried out using Engineering Equation solver (EES) software. In addition, the effects of key design parameters and operating conditions (such as wind inlet speed and average hourly solar radiation) are analyzed, and their effects on the system overall performance are investigated. When 60 kg/s of geothermal fluid is supplied to the designed system, assuming that the NCG composition is equal to 15%, 0.7388 kg hydrogen sulfide will be emitted and 0.0433 kg hydrogen will be produced per second. The first-law (energy) and second-law (exergy) efficiencies are found to be 52.97% and 55.69% respectively.

On the suitable superstructure thermoeconomic optimization of a waste heat recovery system for a Brazilian diesel engine power plant

Brazilian thermal power plants were designed to operate as peaking plants. The diesel engine power plants in Brazil eliminate copious amounts of residual heat through cooling water and exhaust gases. The current scenario has led to an increase in the operational times of the plants. An attractive solution for increasing power and efficiency in this situation is waste heat recovery (WHR). A variety of technologies and configurations can be used for WHR. The selection of the best WHR system is not a simple task, and the solution should not be generalized for different applications. In this work, a superstructure method is used for structural and parametric thermoeconomic optimization, selecting the best WHR for a Brazilian diesel engine power plant operating scenario. Three technologies are considered: the conventional Rankine cycle (CRC), the organic Rankine cycle (ORC), and the Kalina cycle (KC). The thermoeconomic models were developed using Engineering Equation Solver software, and the optimizations were carried out using the genetic algorithm toolbox. Due to the specificity of the Brazilian scenario, the maximization of the gross profit rate function was the selected objective, allowing for the evaluation of 16 combinations of annual dispatch hours and variable unit cost of electricity. The results showed that, although different optimal structures and parameters can be obtained through optimizations, depending on the combinations of annual dispatch and unit cost of electricity, ORC has the highest gross profit rate and is always the best alternative. For an optimistic scenario of dispatch and variable unit cost of electricity, ORC produces up to 14.3 MW of net power, increasing the installed capacity of the 20 generator sets up to 8.2%.

Use of solar radiation to produce cold water for hospital air conditioning system using the combined organic Rankine-vapor compression cycle

In this paper, the optimal combined organic Rankine-vapor compression cycle is proposed to produce cold water for hospital air conditioning using solar energy. The hospital is located in Esfarayen city and the intensity of solar radiation in all months is calculated. The results show that in the five months of May, June, July, August and September, there is the highest solar radiation in Esfarayen city. The possibility of using daily solar radiation to produce cold water during these five months is examined. Simulation is performed using the Engineering Equation Solver (EES) software. Six refrigerants R22, R134a, R600, R143a, R500, and R11 are considered as working fluids for the cycle and based on energy and exergy analysis, suitable fluid is recommended for this system. The effects of solar radiation, refrigerant, and mass flow rate of the refrigerant on the cooling water temperature outlet from the evaporator, cycle performance, organic Rankin cycle efficiency, performance coefficient of the VCC cycle, and exergy efficiency of the ORC-VCC system are investigated. The results show that using the refrigerant R22 is more suitable than other refrigerants because the cycle with this refrigerant reduced the water temperature up to 8 o C in the evaporator, as well as the cycle performance are obtained 0.72 and organic Rankin cycle efficiency is 13.9%, which will be the highest. The results show that increasing boiler thermal energy (solar radiation) reduces water temperature in the evaporator and exergy efficiency of the system, and increases organic Rankin cycle efficiency and cycle performance.

Exergy analysis of heat assisted ejector refrigeration system using R1234yf

An ejector refrigeration system (ERS) is introduced which operates on low-grade energy like solar energy, industrial waste heat etc. In this paper, the performance parameters and the conventional exergy analysis of ejector refrigeration system is measure with reference to ambient conditions. Exergy analysis was applied independently to each component of the system. The refrigerant R1234yf which has low Ozone depletion potential (ODP) and Global depletion potential (GWP) has been used to analysed the exergy analysis with the help of Engineering Equation solver software. The results shows that maximum exergy destruction in generator followed by ejector and other components.

Energy and exergy analysis of a PV-T integrated ethanol PEM electrolyzer

A photovoltaic-thermal (PV-T) integrated ethanol proton exchange membrane electrolyzer (PEME) was proposed as a low-energy consuming energy storage option for renewable-sourced electricity as well as a way for simultaneous chemical production in this study. Energy and exergy analyses were applied to each component of the system (e.g., pumps, heat exchanger, PV-T, PEME, and separation unit (SPU)) and the whole system to assess the system performance. The mathematical modelling of the whole system along with its main components except for the SPU was done using the Engineering Equation Solver (EES) software package while the SPU was modelled through the ASPEN Plus. A detailed modelling of the PEME was also included. The effects of the PV-T and PEME parameters on energy and exergy efficiencies of the system were evaluated while the improvement potentials and scale up options were discussed. Energy and exergy efficiencies of the proposed system at the optimum operation of the PEME and under average climatic conditions in the city of Izmir, Turkey were determined to be 27.8% and 3.1%, respectively. Energy and exergy efficiencies of the system were mainly regulated by the PV-T and PEME, whose energy and exergy efficiencies were 40.6%, 56.6% and 13.8%, 14.1%, respectively. Effective PEME parameters for energy and exergy efficiencies of the system were membrane conductivity, membrane thickness, anode catalyst and the operation temperature of the PEME. By changing the PV-T and PEME parameters and by scale-up, energy and exergy efficiencies of the system could be improved.

Performance Investigation of Direct oupling Advanced Alkaline Electrolysis and PEMFC System

The proton exchange membrane fuel cell (PEMFC) is regarded as the most competitive candidate to replace the traditional forms of power conversion due to its prominent advantages. The hydrogen gas is used as a main fuel in the fuel cells. The hydrogen gas can be produced through the use of solar energy which is connected to alkaline electrolysis cell (AEC) by water splitting process known as electrolysis. In this paper,a thermodynamic model is presented to design and optimize a direct coupling system (DCS) that has two cells, an alkaline electrolysis cell (AEC) and a proton exchange membrane fuel cell (PEMFC). Moreover, the performances of the direct coupling system (DCS) are evaluated using numerical model that are built in Engineering Equations solver software. So several parameters concerning the direct coupling system (DCS) such as the voltage of system, the hydrogen rate production from electrolysis which injects to fuel cell and producing power of the full system. The simulations result show that, the voltage of alkaline electrolysis is higher than the fuel cell. The water management process in the whole system is considered satisfactory due to the low value of the losses in the amount of water. The water which is generated from the fuel cell is injected to electrolysis cell, so the electrolysis cell does not need to inject large quantities of water. The efficiency of the system is about 34.85% and this efficiency is satisfactory compared to other systems of power generation as this percentage is due to clean, renewable and environmentally friendly fuel.

Integrated performance analysis of a space heating system assisted by photovoltaic/thermal collectors and ground source heat pump for hotel and office building types

Utilizing the solar and geothermal energy in space heating systems can save fossil fuels and reduce emissions. In this study, compound parabolic concentrator (CPC) photovoltaic/thermal collectors (PV/T), absorption and ground source heat pumps are integrated to a novel space heating system for use in hotel and office buildings. A full simulation model of the system is constructed and validated by using the Engineering Equation Solver software. The heating system is analyzed against its energy, environmental, economic, and flexibility performance using multiple variables including the PV coverage ratio, ambient temperature, solar beam irradiance, and electricity price. The results show that integrating solar and geothermal energy can be effective to supplement the space heating demand. The best integrated performance point of the office building gives a 32% energy saving ratio, 9% annual cost savings ratio, 23% emission reduction ratio, and 67% excess adjustable ratio compared to a pure ground heat pump system. This research provides new directions of integrated performance evaluation of heating systems assisted by renewable energy resources.

Exergetic evaluation and optimisation of a novel integrated energy conversion system including thermoelectric generators

A comprehensive thermodynamic study of a solar integrated energy system consisted of a solar flat plate collector, an organic Rankine cycle, a thermoelectric generator, and a proton exchange membrane electrolyser is undertaken to generate power and hydrogen. The Matlab and Engineering Equation Solver software are linked, and various optimisation scenarios are investigated. The results of computational analysis indicate that with adding a thermoelectric generator unit in the system about 14 kW of energy in the form of electricity can be obtained from the waste heat of condenser. Various optimisation schemes with exergy efficiency, exergy destruction rate, as well as hourly hydrogen generation as optimisation targets are considered. The optimisation results comparison between base case and optimum design shows that exergetic efficiency improves by about 2.3% and rate of exergy destruction decrease by about 0.791 MW.

Energetic and exergetic analyses of a solar powered combined compression-absorption refrigeration system

This study presents a theoretical framework for the thermodynamic analysis of a combined system which can simultaneously produce cooling for both refrigeration (−5°C) and air conditioning (10°C) for the hot climatic regions in an eco-friendly and carbon free manner. A tower solar collector unit was employed to drive the proposed combined cooling system which consists of a hydrocarbon operated vapour compression refrigeration system that is fed by power from steam turbine shaft, and a waste heat operated single-effect LiBr-H2O operated absorption chiller. A mathematical model using the balances of energy and exergy over the components of the system was developed, and solved using engineering equation solver software. A parametric analysis was conducted to estimate the influence of operating conditions on the system performance. The results show that at baseline operation of the system, for R600a operated VCR, the energetic efficiency of combined system was found to be 73.66% and the exergetic efficiency was 36.43%, while for R290 operated VCR, the energetic and exergetic efficiencies of the combined system were found to be 37.17% and 21.04%, respectively.

PERFORMANCE ANALYSIS OF A SOLAR-DRIVEN EJECTOR AIR CONDITIONING SYSTEM UNDER EL-OUED CLIMATIC CONDITIONS, ALGERIA

In order to understand the behavior and to determine the effective operational parameters of a solar-driven ejector air conditioning system at low or medium temperature, a dynamic model depends on the principles of conservation, the momentum mass and energy is developed. For this purpose, the thermodynamic characteristics of the liquid and vapor refrigerant were identified using the Engineering Equation Solver (EES) software. Linear Fresnel solar reflector has been used as a tool to convert solar energy into thermal energy. Water (R718) was used as a refrigerant. The operational conditions for the studied solar-driven ejector air conditioning system are as follows: evaporator temperature “Te =283.15 K”, condenser temperature “Tc =305.15 K”, and generator temperature “Tg = 373.15 K”. The performance of the ejector air conditioning system was compared as a function of the operating parameters of the subsystem. The average value of thermal efficiency of the Fresnel linear concentrator has reached 31.60 %, the drive ratio “ω” is 0.4934, the performance value of the ejector air conditioning subsystem “COPejc” is 60.664 % and the average value of the thermal performance of the machine “STR” has touched 19.17 %. The results obtained through this scientific subject are stimulating and encouraging, where this technique can be used for air conditioning in desert areas in southern Algeria, where fossil energy (petroleum, gas, etc.) is extracted and produced in various types.

ENERGY AND EXERGY INVESTIGATIONS OF R1234yf AND R1234ze AS R134a REPLACEMENTS IN MECHANICALLY SUBCOOLED VAPOUR COMPRESSION REFRIGERATION CYCLE

The aim of present work is the evaluation of mechanically subcooled simple vapour compression refrigeration system on the basis of energy and exergy analysis, and compatibility of alternative low GWP and zero ODP HFOs R1234yf and R1234ze to replace HFC 134a. A computer program has been developed in Engineering Equation solver software to compute the system performance parameters such as COP, exergetic efficiency, total exergy destruction and exergy destruction ratio. The effect of degree of subcooling (5 to 30℃), evaporator temperature (-30℃ to 15℃), effectiveness of liquid vapour heat exchanger (0.2 to 1.0) and compressor efficiency (0.4 to 1.0) has been investigted on the performance parameters viz. exergy desturction, exergy destruction ratio (EDR) and exergetic efficiency of the system components. The results of current analysis highlight that the R1234ze is the best alternate refrigerant considered in the analysis and can replace R134a as the COP and exergetic efficiency of R1234ze are 1.87% and 1.88% more than that of R134a for 30℃ of subcoooling. However, R1234yf offers lower performance than R134a. The components condenser and evaporator are the sites of highest and lowest exergy destruction respectively for the refrigerants considered.

Theoretical study on geothermal power generation using thermoelectric technology: a potential way to develop geothermal energy

ABSTRACT Thermoelectric power generation is an outstanding technology for high- and low-temperature heat recovery. Their packaging, lack of moving parts, direct heat to electrical conversion, and zero-emission are the main benefits for geothermal power generation. The design of a large-scale, ground-based, and segmented annular concentric cylindrical thermoelectric generators (CCTEGs) with produced geothermal fluid are proposed. A mathematical model for thermoelectric power generation is presented, which considers the heat transfer in the interior of a thermoelectric module and the electric current effect, and is solved with Engineering Equation Solver (EES) software. Numerical results show that about 136 kW of power output could be obtained with 500 m length of segmented annular CCTEG under the inlet fluid temperature difference of 130°C. For the same total flow rates and the same total CCTEG length, the in-series layout of segmented annular CCTEG is better than the in-parallel layout in power generation capacity. Flow rate and fluid temperature have a significant effect on the generated power. A higher flow rate ratio of cold fluid to hot fluid will result in higher power capacity. A desirable flow rate ratio of cold fluid to hot fluid is recommended to take as the flow area ratio of cold fluid flow conduit to hot fluid flow conduit when the critical potential increased power generation capacity is taken as 1.0 kW/kg.

Exergy and performance analyses of impact subcooling for vapor compression refrigeration system utilizing eco-friendly refrigerants

In the present paper, performance and exergy analysis for a vapor compression refrigeration system (VCRS) operating with eco-friendly refrigerants such as R1234ze and R1234fyare tested under different operation conditions to change the recently worked refrigerants R-134a. An analysis through performance and exergy is performed to guide the thermodynamic improvement for the VCRS. Additionally, a comprehensive study is conducted to examine the effects of subcooling temperature on performance and exergy destruction in all components of the VCRS. The exergy destruction of the compressors, condenser, evaporator and expansion device were calculated to obtain the exergy efficiencies. For simulation and analysis the VCRS, Engineering Equation Solver (EES) software program was utilized to obtain the thermodynamics refrigerant properties in which the system operates with the highest eco-friendly, energy and exergy performance is developed the VCRS to determine the most suitable alternative refrigerant to replace the R134a. The results indicate that the refrigerant R1234yf showed the greatest COP enhancement 16.7% due to subcooling, followed by R1234ze 14% and R134a 12.8% under the same operating conditions.

Development and performance assessment power generating systems using clean hydrogen

In this study, three possible reactions of aluminum - water are considered for clean hydrogen production. The utilization of this clean hydrogen through the two concepts of power generation is investigated thermodynamically. The evaluated first power generation facility based on Al - water reaction has an open cycle gas turbine, steam turbine, boiler, reactor and grinder. The second power generation facility has a fuel cell, a reactor and a grinder. The hydrogen generation resulting from the reactions then the conversion of this hydrogen into energy using turbines or fuel cell and the total exergy destruction are examined comparatively. A thermodynamic analysis is performed with the help of EES (Engineering Equation Solver) software based on the equilibrium reactions in steady state regime. The amount of water required for the hydrogen production is investigated and it is found that the energy efficiencies for the three methods are directly proportional to the amount of water. The energy efficiency for the method 1 based on Bayerite reaction is 38%, the energy efficiency for the method 2 based on boehmite reaction is 56% and the method 3 based on aluminum oxide reaction is 73%. The exergy efficiencies for all methods are calculated at around 41%. When two different power generation concepts are examined, it is observed that combustion-based energy production is more efficient in terms of both energy efficiency and exergy efficiencies.

Performance optimization of a heat pump for high temperature application

Environmental and climate protection is one of the most important global challenges of the current century. Energy efficiency and clean energy is a viable solution to this challenge. Heat pumps are age-old technology that is currently widely employed in the residential sector. Heat pumps are an energy-efficient solution to meet hot water requirement in industries as well. High temperature above 80 °C is required for industrial applications. This paper explores the possibility of application of heat pump in industries to cater to high-temperature processes above 100 °C. Refrigerants suitable for high-temperature application are subjected to analysis and comparisons based on their properties using Engineering Equation Solver (EES) software. R1233zd (E) and R1336mzz (Z) is analysed further based on maximum temperature and COP. A case study is carried out on a dairy plant to explore the possibility and extent of energy savings using heat pumps resulting in energy cost reduction of 46%.