scholarly journals АНАЛІЗ ЕФЕКТИВНОСТІ ТЕПЛОВИКОРИСТОВУЮЧОЇ ТЕРМОПРЕСОРНО-ЕЖЕКТОРНОЇ ХОЛОДИЛЬНОЇ МАШИНИ

2019 ◽  
pp. 59-67
Author(s):  
Дмитро Вікторович Коновалов
Keyword(s):  
Energy Efficiency ◽  
Temperature Difference ◽  
Steam Pressure ◽  
Pressure Increase ◽  
Relative Pressure ◽  
Thermal Coefficient ◽  
Boiling Points ◽  
Ejection Coefficient

One of the ways to increase the energy efficiency of ejector refrigerating machines is to use of thermopressor technologies, which are based on to use of the process of thermogasdynamic compression. This process consists in contact cooling and at the same time increasing the gas or steam pressure. The thermopressor application in the ejector refrigerating machines cycle installed at the outlet of the ejector, allows, by increasing the pressure during vapour contact cooling to a saturation tempera-ture, to increase the ejection coefficient U and, accordingly, the thermal coefficient z. A number of refrigerants were chosen for analysis of cycle of ejector refrigerating machines, among which those traditionally is used for ejector refrigerating ma-chines, and a number of other refrigerants that can be used in ejector refrigerating machines based on the possibility of using the thermopressor. It is possible to in-crease the ejector refrigerating machines efficiency by using the thermopressor while ensuring a greater temperature difference. With the temperature difference 60–100 oC, the relative pressure increase is mostly positive. The following refrigerants have the most significance: R717, R134a, R227ea, R1234ze(E), R1234yf. Analysis of the ejector refrigerating machines scheme by using the thermopressor shows that the greatest efficiency at the highest possible boiling points in the generator tg is the refrigerants: R142b, R600, R1233zd(Е), R245fa.

Postcombustion CO2 Capture for Combined Cycles Utilizing Hot-Water Absorbent Regeneration

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Klas Jonshagen ◽  
Majed Sammak ◽  
Magnus Genrup
Keyword(s):  
Power Plant ◽  
Temperature Difference ◽  
Co2 Capture ◽  
Steam Pressure ◽  
Low Pressure ◽  
Pressure Level ◽  
Combined Cycle ◽  
Hot Water ◽  
Combined Cycle Power Plant ◽  
Pressure Plant

The partly hot-water driven CO2 capture plant offers a significant potential for improvement in performance when implemented in a combined-cycle power plant (CCPP). It is possible to achieve the same performance with a dual-pressure steam cycle as in a triple-pressure unit. Even a single-pressure plant can attain an efficiency competitive with that achievable with a triple-pressure plant without the hot-water reboiler. The underlying reasons are better heat utilization in the heat recovery unit and less steam extraction to the absorbent regenerating unit(s). In this paper, the design criteria for a combined cycle power plant utilizing hot-water absorbent regeneration will be examined and presented. The results show that the most suitable plant is one with two steam pressure levels. The low-pressure level should be much higher than in a conventional combined cycle in order to increase the amount of heat available in the economizer. The external heat required in the CO2 capture plant is partly supplied by the economizer, allowing temperature optimization in the unit. The maximum value of the low-pressure level is determined by the reboiler, as too great a temperature difference is unfavorable. This work evaluates the benefits of coupling the economizer and the reboiler in a specially designed CCPP. In the CO2 separation plant both monoethanolamine (MEA) and ammonia are evaluated as absorbents. Higher regeneration temperatures can be tolerated in ammonia-based plants than in MEA-based plants. When using a liquid heat carrier the reboiler temperature is not constant on the hot side, which results in greater temperature differences. The temperature difference can be greatly reduced by dividing the regeneration process into two units operating at different pressures. The possibility of extracting more energy from the economizer to replace part of the extracted steam increases the plant efficiency. The results show that very high efficiencies can be achieved without using multiple pressure-levels.

scholarly journals NUMERICAL MODELING AND EXPERIMENTAL RESEARCH OF A LIQUID-LIQUID EJECTORS WITH A CURVED INITIAL MIXING CHAMBER AREA AND WITH DIRECT MIXING CAMERA

2020 ◽  
pp. 88-95
Author(s):  
Salar Kartas ◽  
◽  
Vladimir Panchenko ◽  
Yury Aleksandrov ◽  
◽  
...  
Keyword(s):  
Pressure Drop ◽  
Experimental Studies ◽  
Design Parameters ◽  
Layer By Layer ◽  
Relative Pressure ◽  
Initial Portion ◽  
Ansys Fluent ◽  
Ejection Coefficient ◽  
Mixing Chamber ◽  
Calculation Results

The article presents the results of numerical simulations and experimental studies of a liquid-liquid ejector with a curved initial portion of the mixing chamber. The experiment was conducted on liquid-liquid ejectors, models of which are made on a 3D printer, by the method of layer-by-layer deposition. The influence of possible manufacturing errors of the ejector on its characteristics is estimated. The issues of the use of liquid ejectors designed to work in the field of various predetermined ejection coefficients are considered. The theoretical ejection coefficient and the reasons for reducing the ejection coefficient in real ejectors are determined. The obtained dependences make it possible to determine the optimal design parameters of a liquid ejector and thereby increase its ejection coefficient. The relative pressure drop is shown at a low coefficient and at a high ejection coefficient. The calculated and experimental results of determining the ejection coefficient for liquid ejectors, which are widely used in various fields of technology, are presented. The results of numerical simulation of internal processes in the ANSYS-Fluent hydro-gasdynamic application package flowing in a single-phase liquidliquid ejector based on the study of a small-sized model are presented. As a result of the simulation, a good agreement was obtained between the calculation results of the model corresponding to the real prototype and the experimental data and comparison with the results of other authors. Several conclusions can be drawn from the results of the study. For example, a region of values of the ejection coefficient was found in which the relative pressure drop created by the ejector increases with an increase in the ejection coefficient.

scholarly journals Modelling Surtseyan Ejecta

2021 ◽  
Author(s):  
◽  
Emma Greenbank
Keyword(s):  
Tensile Strength ◽  
Steady State ◽  
Temperature Difference ◽  
Numerical Solutions ◽  
Volcanic Eruptions ◽  
Steady State Solution ◽  
Pressure Increase ◽  
Large Temperature ◽  
Maximum Pressure ◽  
Temperature And Pressure

<p>Surtseyan ejecta are formed in shallow sub-aqueous volcanic eruptions. They occur when water, containing a slurry of previously erupted material, is washed into the volcanic vent. This slurry is incorporated into the magma and ejected from the volcano inside a ball of magma. These magma bombs containing entrained material are called, Surtseyan ejecta or Surtseyan bombs.  At the time of entrainment there is a large temperature difference between the magma (at approximately 1000°C) and the slurry (at approximately 20°C). As the inclusion temperature increases, the water contained in the slurry evaporates, causing an increase in the pressure at the boundary of the entrainment. This pressure increase is offset by the vapour diffusing through the pores of the magma. If the pressure exceeds the tensile strength of the surrounding magma the Surtseyan ejecta will rupture.  The volcanological question of interest is whether the magma ruptures. There is evidence of intact ejecta so it can be concluded that rupture does not always occur. We have developed a set of equations that transiently model the changes in temperature and pressure in Surtseyan ejecta. Numerical solutions show that the pressure rapidly increases to a stable value. Because the pressure reaches equilibrium a steady-state solution can be used to determine the maximum pressure and a criterion for rupture.</p>

Analysis on Heat Transfer Energy Efficiency of U-Tube Buried Pipe under Variable Entering Water Temperature Conditions

2014 ◽  
Vol 960-961 ◽  
pp. 603-608
Author(s):  
Yu Zhou Cui
Keyword(s):  
Heat Transfer ◽  
Energy Efficiency ◽  
Water Temperature ◽  
Heat Pump ◽  
Temperature Difference ◽  
Heat Extraction ◽  
Ground Source Heat Pump ◽  
Buried Pipe ◽  
Ground Source ◽  
Heat Transfer Capacity

Taken as the carrier of heat extraction between rock-soil body and ground source heat pump systems, U-tubed pipe heat transfer efficiency was the key for ensuring the long-term and high-performance operation of ground source heat pump systems by means of improving the heat transfer effect. The efficiency coefficient, E, is defined as the ratio of the actual heat transfer capacity to the theoretically maximal heat transfer capacity from the U-tube into rock-soil body, which illustrated the effect of heat transfer ability and the variable heating or cooling loads. Aim at Variation characteristics of heat transfer coefficient of energy efficiency under the variable temperature inflow condition, decomposed into the product of the ratio of biggest buried tube heat transfer temperature difference φ and heat pump outlet water temperature difference σ. Use of u-shaped buried pipe three-dimensional heat transfer model which based on the multipole theory, the influence law of its change which caused by the construction load, buried pipe flow and the unit performance were analyzed, it can provide technical support to optimize the design of ground source heat pump system.

scholarly journals The Comparison of Different Types of Heat Accumulators and Benefits of Their Use in Horticulture

Sensors ◽  
2020 ◽  
Vol 20 (5) ◽  
pp. 1417
Author(s):  
Sławomir Kurpaska ◽  
Jarosław Knaga ◽  
Hubert Latała ◽  
Michał Cupiał ◽  
Paweł Konopacki ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Solar Radiation ◽  
Phase Change ◽  
Temperature Difference ◽  
Radiation Intensity ◽  
Fossil Fuels ◽  
Ground Level ◽  
Solar Radiation Intensity ◽  
Below Ground ◽  
Energy Storage Efficiency

This paper presents the results of the analysis of thermal issues and energy efficiency of three types of accumulators; namely stone-bed; water and phase change. Research experiments were carried out during April–October 2013 in a standard commercial semi-cylindrical high plastic tunnel with tomato cultivation of 150 m2. A stone-bed accumulator; with an area of almost 75 m2 was installed in the tunnel below ground level; while a water accumulator with a volume of 4 m3 was installed outside the tunnel. A phase change material (PCM) accumulator, with a volume of 1 m3 containing paraffin, was located inside the tunnel. The heat storage capacity of the tested accumulators and the energy efficiency of the process were determined based on the analyses of the 392 stone-bed charging and discharging cycles, the 62 water accumulator charging cycles and close to 40 PCM accumulator charging and discharging cycles. Dependencies in the form of easily measurable parameters; have been established to determine the amount of stored heat; as well as the conditions for which the effectiveness of these processes reaches the highest value. The presented analysis falls under the pro-ecological scope of replacing fossil fuels with renewable energy. As a result of the analysis; it was found that; in the case of a stone-bed; such an accumulator shows higher efficiency at lower parameters; that is, temperature difference and solar radiation intensity. In turn; a higher temperature difference and a higher value of solar radiation intensity are required for the water accumulator. The energy storage efficiency of the PCM accumulator is emphatically smaller and not comparable with either the stone-bed or the water accumulator.

scholarly journals Modelling Surtseyan Ejecta

2021 ◽  
Author(s):  
◽  
Emma Greenbank
Keyword(s):  
Tensile Strength ◽  
Steady State ◽  
Temperature Difference ◽  
Numerical Solutions ◽  
Volcanic Eruptions ◽  
Steady State Solution ◽  
Pressure Increase ◽  
Large Temperature ◽  
Maximum Pressure ◽  
Temperature And Pressure

<p>Surtseyan ejecta are formed in shallow sub-aqueous volcanic eruptions. They occur when water, containing a slurry of previously erupted material, is washed into the volcanic vent. This slurry is incorporated into the magma and ejected from the volcano inside a ball of magma. These magma bombs containing entrained material are called, Surtseyan ejecta or Surtseyan bombs.  At the time of entrainment there is a large temperature difference between the magma (at approximately 1000°C) and the slurry (at approximately 20°C). As the inclusion temperature increases, the water contained in the slurry evaporates, causing an increase in the pressure at the boundary of the entrainment. This pressure increase is offset by the vapour diffusing through the pores of the magma. If the pressure exceeds the tensile strength of the surrounding magma the Surtseyan ejecta will rupture.  The volcanological question of interest is whether the magma ruptures. There is evidence of intact ejecta so it can be concluded that rupture does not always occur. We have developed a set of equations that transiently model the changes in temperature and pressure in Surtseyan ejecta. Numerical solutions show that the pressure rapidly increases to a stable value. Because the pressure reaches equilibrium a steady-state solution can be used to determine the maximum pressure and a criterion for rupture.</p>

scholarly journals Аналіз ефективності ежекторних холодильних машин на різних холодоагентах

2021 ◽  
pp. 40-47
Author(s):  
Андрій Миколайович Радченко ◽  
Дмитро Вікторович Коновалов ◽  
Сергій Георгійович Фордуй ◽  
Роман Миколайович Радченко ◽  
Сергій Анатолійович Кантор ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Heat Recovery ◽  
Power Plants ◽  
Internal Combustion Engines ◽  
Maximum Efficiency ◽  
Working Fluid ◽  
Condensation Temperature ◽  
Thermal Coefficient ◽  
Environmental Friendliness ◽  
Maximum Heat

Modern heat-using ejector refrigeration machines used in heat recovery systems for power plants based on gas turbine engines and internal combustion engines have many advantages over absorption refrigeration machines: smaller dimensions and weight; the ability to obtain lower temperatures. However, they are inferior in energy efficiency, and the thermal coefficient is much lower and can be 0.2…0.4. The efficiency of such refrigeration machines largely depends on the choice of the working fluid (refrigerant). Hence the need to choose a refrigerant that would provide the maximum heat factor, and hence the maximum efficiency of heat recovery. Given the relatively low efficiency of the ejector refrigeration machine, the search for a working fluid that will provide, on the one hand, higher thermal coefficients, and on the other hand high environmental friendliness, is one of the promising areas of development of heat recovery technologies in power plants. The study used the software complex developed by the authors to calculate the refrigeration cycles of heat-using refrigeration machines, taking into account the properties of many modern refrigerants, ejector characteristics, as well as basic heat exchangers (condenser, evaporator, generator). The efficiency of ejector refrigeration machines when working on the following working bodies was analyzed: R142b, R134a, R600, R600a, R1234ze(E), R1233zd(E), R1234yf, R227ea, R236fa, R245fa. R142b, R600, R600a, R245fa have the largest values of thermal coefficients. It is established that the most profitable in terms of environmental friendliness (ODP, GWP) and energy efficiency is the use of refrigerant R245fa, which has a condensation temperature range is 25…35 oC and boiling in the evaporator is 0…15 oC thermal coefficient is 0.40…1.03.

scholarly journals A Novel Integration of PCM with Wind-Catcher Skin Material in Order to Increase Heat Transfer Rate

2019 ◽  
Vol 8 (1) ◽  
pp. 1 ◽  
Author(s):  
Leila Seidabadi ◽  
Hossein Ghadamian ◽  
Mohammad Aminy
Keyword(s):  
Heat Transfer ◽  
Energy Efficiency ◽  
Energy Consumption ◽  
Energy Storage ◽  
Heat Transfer Rate ◽  
Temperature Difference ◽  
Transfer Rate ◽  
Time Dependent ◽  
Passive Cooling ◽  
Dynamic Time

In this research, a comprehensive simulation study including 3-D Dynamic time-dependent has been performed for Phase Change Materials (PCMs) applicant as a thermal storage integrated with the wind-catcher-wall in order to reduce the temperature difference (As a sustainable cooling method) in the MATLAB open-source–code software. By means of 3-D Dynamic time-dependent, as a final finding, the temperature drop (Cooling purpose) was obtained 25 degrees at about 7 working hours. Passive cooling can be considered as a viable and attractive strategy for the sustainable concept, opposed to mitigation of energy consumption and Green House Gas (GHG) simultaneously. One of the traditional-old-age famous passive cooling systems that are still being applied nowadays is wind-catcher as an energy system. The wind catcher sustain natural ventilation and cooling in buildings through wind-driven airflow as well as temperature difference. Windcatchers can save the electrical energy used to provide thermal comfort during the hot climate in summer case of the year, especially during the peak hours contributed to energy carriers’ consumptions. In this study, by proposing a new design of the windcatchers, attempts have been made to improve the energy efficiency of passive cooling methods. Besides, the application of new efficient methods for the purpose of thermal energy storage (PCM) as a sub-system is a chosen method to increase energy efficiency. By applying energy storage systems in addition to increase system energy performance and reliability, the target of reducing energy consumption is achieved.© 2019. CBIORE-IJRED. All rights reservedArticle History: Received May 18th 2018; Received in revised form October 5th  2018; Accepted January 5th 2019; Available onlineHow to Cite This Article: Seidabadi, L., Ghadamian, H, and Aminy, M. (2019) A Novel Integration of PCM with Wind-Catcher Skin Material in Order to Increase Heat Transfer Rate. Int. Journal of Renewable Energy Development, 8(1), 1-6.https://doi.org/10.14710/ijred.8.1.1-6

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