scholarly journals Analyzing the Thermodynamic Efficiency of Cooling Cycles Depending on the Determinant Thermal and Physical Properties of Operating Media

2021 ◽  
pp. 60-70
Author(s):  
Viktorija Tarasova ◽  
Mikhail Kuznetsov
Keyword(s):  
Physical Properties ◽  
Optimization Procedure ◽  
Single Stage ◽  
Thermodynamic Efficiency ◽  
Limited Information ◽  
Regenerative Heat ◽  
State Diagrams ◽  
Evaporation And Condensation ◽  
Cooling Agent ◽  
Multiparameter Optimization

The goal of this research was to develop the methods used for the analysis of the thermodynamic efficiency of the ordinary single-stage and regenerative cooling cycles depending on the determinant thermal-&-physical properties of cooling agents. The thermodynamic efficiency of the steam –compressive single-stage ordinary and regenerative cycles of cooling machines operating on different cooling agents has been investigated. The dependence was established between the effectiveness value of the use of the regeneration for the cooling cycle and the modified Clausius criterion of the cooling agent. Generalized regressive dependences were obtained for the evaluation of the efficiency of the ordinary and regenerative cycles based on the determinant modified Clausius criterion and these give us an opportunity to establish the fields for the preferential use of the promising cooling agents for regenerative cycles and establish requirements to the properties of cooling agents during their choice. These contribute to the selection of the rational flowchart for the specified thermal and physical characteristics of the cooling agent and for the thermal behavior of the unit operation and form appropriate rational geometric characteristics for the heat exchangers and interconnecting piping. The suggested methods enable the determination of the expected characteristics of the unit and the boundary attainable values of its efficiency in the conditions of the limited information on the thermal-&-physical properties of new (by-way) cooling agents without waiting for the appearance of accurate state diagrams. Analytical equations used for the estimation of the cooling factor depending on the modified Clausius criterion allow us to perform the front-end project computations making use of only absolute values of evaporation and condensation temperatures. The effect of the steam depression, the dryness value and the efficiency factor of the regenerative heat exchanger on the cooling factor of the cycle has been studied. A practical value of the obtained data consists in the opportunity of the objective and operative estimation of the efficiency of the use of the cooling agent for the regenerative and steam compressing cycles of the cooling machine using no multiparameter optimization procedure.

Bulk Effective Moduli: Their Calculation and Usage for Describing Physical Properties of Composite Media

1990 ◽  
Vol 195 ◽  
Author(s):  
David J. Bergman
Keyword(s):  
Physical Properties ◽  
Effective Properties ◽  
Weak Field ◽  
Elastic Stiffness ◽  
Effective Medium ◽  
Discrete Models ◽  
Theoretical Treatment ◽  
Limited Information ◽  
Property A ◽  
Nonlinear Properties

ABSTRACTWhile not telling the whole story, the representation of a composite medium by a homogeneous effective medium is often an excellent approximation for describing its macroscopic physical properties. Modern methods for calculating the effective medium properties are reviewed with special emphasis on understanding both successes and limitations. Outstanding problems that can and should be tackled are identified. The successes include calculations of the electrical conductivity, dielectric coefficient, and elastic stiffness moduli of composites with a periodic microstructure, and the simulation of those properties for disordered composites near a percolation threshold by means of discrete models such as a random-resistor-network. For composites where the microstructure is either unknown or very complicated, a whole class of exact bounds have been found for these properties based on various types of limited information. Recently, advances have been made in calculating the weak field magneto-transport and the thermoelectric behavior of two-component composites, and also some types of nonlinear properties. An important challenge remains the calculation of magneto-transport at high magnetic fields. Another is the theoretical treatment of multicomponent composites. A third is to find relations between different effective properties of a composite that can enable us to learn about property A by measuring a different property B. This is especially important when the measurement of A would destroy the sample, as when A is the yield stress, whereas the measurement of B is nondestructive, as when B is a small, nonlinear correction to the usual elastic stiffness moduli.

Advanced Liquefaction Cycle for Natural Gas

2018 ◽  
Author(s):  
Mungyu Kim ◽  
Youngrae Kim ◽  
Minseok Kim ◽  
Minki Kim ◽  
Kihwan Lee ◽  
...  
Keyword(s):  
Natural Gas ◽  
Life Cycle Cost ◽  
Production Efficiency ◽  
Single Stage ◽  
Cooling Curve ◽  
Thermodynamic Efficiency ◽  
Cooling Zone ◽  
Associated Gas ◽  
Two Stages ◽  
Straight Lines

This paper presents a LNG Liquefaction cycle configuration using two stages of methane expansion and a single stage of nitrogen expansion (Dual Refrigerant) to improve the efficiency of the conventional methane and nitrogen refrigerant expansion cycle (Niche Cycle). The chosen configuration further optimizes the composite cooling and heating curve of the liquefaction cycle, resulting in a higher thermodynamic efficiency. The production efficiency of the liquefaction cycle can be improved by reducing the interval between the cooling curve of the natural gas and the warming curve of the refrigerant: the closer both curves are, the better the efficiency of the cycle. This optimization is achieved by adjusting the refrigerant operating temperatures and pressures. The advanced dual refrigerant expansion cycle includes three levels of expansion, each having different temperature and pressure levels. In the methane expansion loop there are two stages, which are classified warm and cold. The warm loop is applied in the pre-cooling zone and the cold loop is responsible for the main liquefaction. The nitrogen loop is a single stage and is used for sub-cooling. This configuration allows the methane and nitrogen warming curve to closely match the cooling curve of the natural gas cooling curve by changing the methane and nitrogen warming curve from two straight lines into multiple intersecting straight lines of different gradient. That is to say, the additional new methane expander generates an added inflection point within the cold composite curve. As a result, thermodynamic inefficiencies are minimized and the power requirements are reduced when compared to Niche Cycle. In comparison with other previous expansion cycles, the cycle efficiency has increased approximately from 13.13 to 12.08 kW/ton/day (8% efficiency increase) assuming similar feed gas (methane: 80%, MW: 21.38). The composition of this feed gas is representative for associated gas or pipe line gas which is preliminary treated to remove bulk water and hydrocarbon condensate. A case study is presented for an open sea associated gas FLNG concept, comparing three kinds of liquefaction processes (Double Nitrogen Expansion Cycle, Methane & Nitrogen Expansion Cycle and Developed Dual Refrigerant Expansion Cycle). A Life Cycle Cost (LCC) analysis based on Net Positive Value (NPV) also shows an improvement in terms of project NPV, against a minor increment of the CAPEX of these cycles.

Energy saving in batch distillation for separation of ternary zeotropic mixture integrated with vapor recompression scheme: dynamics and control

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Gandu Radhika ◽  
Akash Kumar Burolia ◽  
Pandiyan Kuppusamy Raghu Raja ◽  
Seshagiri Rao Ambati ◽  
Dipesh S. Patle ◽  
...  
Keyword(s):  
Closed Loop ◽  
Energy Savings ◽  
Open Loop ◽  
Single Stage ◽  
Large Temperature ◽  
Thermodynamic Efficiency ◽  
Batch Distillation ◽  
Proportional Integral ◽  
Zeotropic Mixture ◽  
Vapor Recompression

Abstract In this work, tight composition control and in parallel the operation is integrated with vapor recompression scheme (VRC) is proposed to achieve energy savings and maximum product at a specified high purity for the separation of ternary zeotropic mixture in batch distillation. Firstly, the model representing a ternary system of hexanol/octanol/decanol has been simulated to analyze the open-loop and close-loop dynamics of the process. Secondly, the open-loop and closed-loop operations are integrated with single stage VRC scheme to achieve energy savings. Single stage VRC is operated at very high compression ratio (CR) due to the large temperature difference of the top and bottom streams in batch distillation column. To further improve the thermodynamic efficiency of single stage VRC, double stage compression without intercoolers between the stages of VRC is proposed. Two control schemes have been implemented for constant composition, namely proportional integral (PI) controller and nonlinear gain scheduling proportional integral (GSPI) with and without VRC in closed-loop. The results shows that double stage VRC with GSPI algorithm provides better performance than conventional in terms of energy, product amount and Integral Square Error (ISE).

scholarly journals Analysis of factors affecting the efficiency of thermosyphones

2021 ◽  
Vol 1 (1) ◽  
pp. 77-88
Author(s):  
Tyurin M. P. ◽  
◽  
Borodina E. S. ◽  
Keyword(s):  
Mass Transfer ◽  
Physical Properties ◽  
Heat And Mass Transfer ◽  
Two Phase ◽  
Factors Affecting ◽  
Geometric Characteristics ◽  
Evaporation And Condensation ◽  
Working Bodies ◽  
Efficiency And Reliability ◽  
Degree Of Filling

The paper provides a review and analysis of research works aimed at studying the factors that affect the efficiency and reliability of closed two-phase thermosyphons as heat utilizers of heat technological emissions. Factors such as the geometric characteristics of thermosyphons and their ratio, the angles of inclination of the evaporation and condensation surfaces, the degree of filling of the thermosyphon pipe, the state and physical properties of the evaporation and condensation surfaces, the influence of acoustic and vibration influences on the efficiency of heat and mass transfer, as well as their use in as working bodies of nanofluids.

scholarly journals Analysis of factors affecting the efficiency of thermosyphones

2021 ◽  
Vol 1 (1) ◽  
pp. 77-88
Author(s):  
M. P. Tyurin ◽  
◽  
E. S. Borodina ◽  
Keyword(s):  
Mass Transfer ◽  
Physical Properties ◽  
Heat And Mass Transfer ◽  
Two Phase ◽  
Factors Affecting ◽  
Geometric Characteristics ◽  
Evaporation And Condensation ◽  
Working Bodies ◽  
Efficiency And Reliability ◽  
Degree Of Filling

The paper provides a review and analysis of research works aimed at studying the factors that affect the efficiency and reliability of closed two-phase thermosyphons as heat utilizers of heat technological emissions. Factors such as the geometric characteristics of thermosyphons and their ratio, the angles of inclination of the evaporation and condensation surfaces, the degree of filling of the thermosyphon pipe, the state and physical properties of the evaporation and condensation surfaces, the influence of acoustic and vibration influences on the efficiency of heat and mass transfer, as well as their use in as working bodies of nanofluids.

scholarly journals Experimental analysis of the stability of ferrofluids based on Iron Oxide powder

2021 ◽  
pp. 1-6
Author(s):  
Daniel ZĄBEK ◽  
Andrzej GRZEBIELEC ◽  
Luca CMOK ◽  
Patricija HRIBAR BOŠTJANČIČ ◽  
Alenka MERTELJ
Keyword(s):  
Fatty Acid ◽  
Iron Oxide ◽  
Physical Properties ◽  
Experimental Analysis ◽  
Solid Phase ◽  
Oxide Powder ◽  
Solid Particles ◽  
Evaporation And Condensation ◽  
Natural Tendency ◽  
The Stability

Ferrofluids most often consist of three components, they are: solid particles, the liquid in which they are dissolved and a substance that is supposed to prevent sedimentation - called surfacant. The biggest problem with ferrofluids is their stability. Mixtures in which one of the phases is a solid phase have a natural tendency to sedimentation. As a result, physical properties change during the use of such materials. As part of the research, it was decided to check which ferrofluid composition would be most resistant to continuous evaporation and condensation processes. Three different mixtures were analyzed. As a result of the experiment it was found that the best behavior was mixture of: iron-oxide with n-heptane and fatty acid as surfacant.

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