An approach to entropy analysis of a latent heat storage module

Erek, Aytunç; Dinçer, İbrahim

doi:10.1016/j.ijthermalsci.2007.08.002

Cited by 63 publications

(34 citation statements)

References 19 publications

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“…Therefore the quantities related to the whole storage tank and total charging/discharging cycle can be calculated integrating in x and t the local values. The exergy flow balance for the storage system can be written as [36,37]: …”

Section: Storage Tank Wallsmentioning

confidence: 99%

Modelling and simulation of phase change material latent heat storages applied to a solar-powered Organic Rankine Cycle

2016

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Solar energy is one of the most promising renewable energy sources, but is intermittent by its nature. The study of efficient thermal heat storage technologies is of fundamental importance for the development of solar power systems. This work focuses on a robust mathematical model of a Latent Heat Storage (LHS) system constituted by a storage tank containing Phase Change Material spheres. The model, developed in EES environment, provides the time-dependent temperature profiles for the PCM and the heat transfer fluid flowing in the storage tank, and the energy and exergy stored as well. A case study on the application of the LHS technology is also presented. The operation of a solar power plant associated with a latent heat thermal storage and an ORC unit is simulated under dynamic (time-varying) solar radiation conditions with the software TRNSYS. The performance of the proposed plant is simulated over a one week period, and the results show that the system is able to provide power in 78.5% of the time, with weekly averaged efficiencies of 13.4% for the ORC unit, and of 3.9% for the whole plant (from solar radiation to net power delivered by the ORC expander).

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Section: Storage Tank Wallsmentioning

confidence: 99%

Modelling and simulation of phase change material latent heat storages applied to a solar-powered Organic Rankine Cycle

2016

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“…The lasted studies indicate that the entropy generation due to the heat gain by the system from the environment should also be taken into account [3,83,84]. Therefore, the general form of the expression for charging and discharging processes can be written as: …”

Section: Generation Of Entropymentioning

confidence: 99%

Waste Thermal Energy Harvesting (III): Storage with Phase Change Materials

Kong

Hng

et al. 2014

Waste Energy Harvesting

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In last two chapters, both methods to harvest waste thermal energy through the conversion to electricity. In this chapter, energy storage (ES) as an alternative method to harvest waste thermal energy, especially by using phase change materials (PCMs), will be presented.ES, as suggested by the name, is to store a certain form of energy, which thus be used later when necessary. A device that can be used to store any form of energy is generally called an accumulator. There are various forms of energy, commonly including kinetic energy, potential energy (e.g., gravitational or chemical), electrical energy, thermal energy, and so on. All these forms of energy could be stored by using an appropriate method [1,2]. For instance, mechanical energy can be stored by using hydrostorage, compressed air storage, and flywheels, while electrical energy is stored by using various batteries and supercapacitors. Thermal energy storage (TES) is the main content of this chapter.This chapter is arranged as follows. A brief description on various TES conceptions, together with a comparison, will be presented first. Among them, PCMs for TES will be emphasized. After that, PCMs with their classification according to their composition will be discussed. Design criteria, heat transfer phenomena, configuration of various PCM TES systems, which have been reported in open literature, will be summarized. Specific attention will be paid to the exergy analysis. The main applications of the PCM storage systems will be listed, analyzed, and compared. Strategies that have been used to improve the performance of such storage systems will be thoroughly evaluated. It will be ended with concluding remarks and perspectives of development of this technology.

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“…Furthermore, Bejan [4-6] related the optimal heat transfer to the minimum production of entropy generation and extended this idea into other systems. Researchers have done many investigations on heat transfer optimization based on the minimum principle of entropy generation [11,12]. As the objective of this kind of optimization method is to minimize the entropy generation, it is called thermodynamic optimization.…”

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confidence: 99%

Entransy analysis of open thermodynamic systems

2012

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The concept of entransy developed in recent years can describe the heat transport ability. This paper extends this concept to the open thermodynamic system and defines the concept of enthalpy entransy. The entransy balance equation of steady open thermodynamic systems, as well as the concept of entransy loss, is developed. The entransy balance equation is applied to analyzing and discussing the air standard cycle. It is found that the entransy loss rate can describe the change in net power output from the cycle but the entropy generation rate cannot when the heat absorbed by the working medium is from the combustion reaction of the gas fuel. When the working medium is heated by a high temperature stream, both the maximum entransy loss rate and the minimum entropy generation rate correspond to the maximum net power output from the cycle. Hence, the concept of entransy loss is an appropriate figure of merit that describes the cycle performance. As nearly 80% of the total energy consumption is related to heat [1], the optimization design of heat transfer and heatwork conversion has become one of important research topics under the increasing requirements on reducing energy consumption. For instance, the design optimization could improve the performance of heat exchangers and increase heat transfer rate [1]. Optimizing the thermal conductance distribution of the heat exchanger groups could also increase the work output in heat-work conversion [2]. Several theories have been developed for the optimal design of heat transfer and heat-work conversion in recent years [1][2][3][4][5][6][7]. Bejan [4-6] developed the constructal theory and thermodynamic optimizations for heat transfer processes. In heat conduction optimization of the Volume-to-Point problem, Bejan [4] developed the constructal theory, in which the basic, imagined structure of the high conductivity material is given, and the aspect ratio of the structure is optimized through theoretical derivation and numerical simulation to decrease the highest temperature of the heated domain. The sub-structure, third degree structure, etc. are evolved to cover the whole domain. The constructal theory was found to be effective for heat conduction optimization and was extended to heat convection optimizations [8][9][10]. Furthermore, Bejan [4-6] related the optimal heat transfer to the minimum production of entropy generation and extended this idea into other systems. Researchers have done many investigations on heat transfer optimization based on the minimum principle of entropy generation [11,12]. As the objective of this kind of optimization method is to minimize the entropy generation, it is called thermodynamic optimization.However, there are arguments on the constructal theory and thermodynamic optimization in heat transfer [6,[13][14][15][16][17]. Ghodoossi [13,14] applied the constructal theory to analyzing the effect of the complexity levels of the tree network of conducting paths and found that the heat flow performance does not essentially improve if the intern...

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An approach to entropy analysis of a latent heat storage module

Cited by 63 publications

References 19 publications

Modelling and simulation of phase change material latent heat storages applied to a solar-powered Organic Rankine Cycle

Modelling and simulation of phase change material latent heat storages applied to a solar-powered Organic Rankine Cycle

Waste Thermal Energy Harvesting (III): Storage with Phase Change Materials

Entransy analysis of open thermodynamic systems

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