Thermodynamic analysis

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2020 The Authors. Energy Science & Engineering published by the Society of Chemical Industry and John Wiley & Sons Ltd. Department of Mechanical Engineering, University of Mazandaran, Babolsar, Iran

Exergy analysis of a combined cycle power generation plant using gas and steam turbines, through the use of Excel to demonstrate full set of calculations. Short discussion and comment provided. Results tabulated at end of analysis. Just over 900 lines with figures. Makes for a study guide for students and practising energy/renewable engineers.

Zoom in at a high level, PDF file if legible or good quality. You may request the Excel file. Source of study Power Plant Engineering 4th Ed Pk Nag.

In this paper, using the combination of the first and second laws of thermodynamics, the work bounds in thermodynamic cycles are investigated generally and, to show the application, the results are extracted for some physical systems. Also, a new concept on the available work limits is extracted. To provide information on the maximum or minimum amount of work to be done during a thermodynamic cycle, energy balance, as well as irreversibility, should be considered. Entropy production during a thermodynamic cycle as a limiting criterion for work to be done is expressed as Clausius inequality. Therefore an inequality extracted from the first and second laws of thermodynamic to obtain lower and upper bounds of available work. The obtained upper bound of the work to be done is in agreement with Carnot's rule. The lower bound is obtained at the maximum possible irreversibility during the respective cycle.

È possibile dedurre le proprietà degli oggetti macroscopici a partire dalle proprietà degli atomi o delle molecole che li costituiscono? La Termodinamica Statistica risponde affermativamente (almeno in linea di principio) e si pone l’ambizioso obiettivo di tracciare la strada per collegare micromondo e macromondo, introducendo appropriati metodi statistici per trattare gli elevatissimi numeri di particelle presenti.
Questo volume vuole offrire un’introduzione agile a tale materia, con uno stile discorsivo, evitando un apparato matematico troppo pesante, privilegiando i concetti e illustrandoli con semplici esempi.
Il testo, pensato per gli studenti di Chimica, può essere utilizzato come strumento introduttivo anche dagli studenti di Fisica, Ingegneria, Scienza dei Materiali o altri Corsi di Laurea.


Indice:

Prefazione
1. Dalle molecole al mondo macroscopico
2. Princìpi di Termodinamica Statistica
3. Entropia e Secondo Principio: significato statistico
4. Sistemi non-isolati
5. Gas ideale monoatomico
6. Gas ideale biatomico
7. Equilibri di reazione in gas diluiti
Conclusione
Bibliografia
Indice Analitico


Nota sull'Autore
Domenico Gazzillo, laureato in Fisica, è professore associato di Chimica Fisica presso il Dipartimento di Scienze Molecolari e Nanosistemi dell’Università Ca’ Foscari di Venezia.
La sua attività di ricerca si è svolta essenzialmente nel campo della Termodinamica Statistica dei Liquidi e attualmente concerne lo studio della Materia Condensata Soffice (in particolare sistemi colloidali, proteine in soluzione, biopolimeri e altri nanomateriali). E' autore di un testo universitario di Termodinamica Classica: Termodinamica e…, Lezioni e riflessioni didattiche (2a ed. 2012).

The study investigated the impact of the nanoparticle size which has been suggested to be an important factor the results were found to be in concord with the experimental observations. The values of the thermal conductivity for different nanofluid combinations were calculated using the expression developed in this study and they agreed with published experimental data. From the study, it was observed that Brownian motion is significant only when the volume fraction is less than 1 % in case of TiO2&ZnO and 4 % in case of Al2O3. The combination of the base fluid and nanoparticles to from nanoclusters is expected provide better heat transfer solution than the conventional fluids , Hence it is concluded that adding nanosized materials to base fluids enhances thermal properties and makes them more suitable to heat exchanger applications as well as for many industrial applications also .

We study self-organization of collective motion as a thermodynamic phenomenon in the context of the first law of thermodynamics. It is expected that the coherent ordered motion typically self-organises in the presence of changes in the (generalized) internal energy and of (generalized) work done on, or extracted from, the system. We aim to explicitly quantify changes in these two quantities in a system of simulated self-propelled particles and contrast them with changes in the system's configuration entropy. In doing so, we adapt a thermodynamic formulation of the curvatures of the internal energy and the work, with respect to two parameters that control the particles' alignment. This allows us to systematically investigate the behavior of the system by varying the two control parameters to drive the system across a kinetic phase transition. Our results identify critical regimes and show that during the phase transition, where the configuration entropy of the system decreases, the rates of change of the work and of the internal energy also decrease, while their curvatures diverge. Importantly, the reduction of entropy achieved through expenditure of work is shown to peak at criticality. We relate this both to a thermodynamic efficiency and the significance of the increased order with respect to a computational path. Additionally, this study provides an information-geometric interpretation of the curvature of the internal energy as the difference between two curvatures: the curvature of the free entropy, captured by the Fisher information, and the curvature of the configuration entropy.

For over 50 years, high-pressure gas turbine blades have been cooled using air bled from the compressor. This cooling results in very high rates of heat transfer, both within the fluid and within the blade, shown in figure 1. The heat transfer often occurs across large temperature differences and is thus highly irreversible. It is therefore surprising that little is understood about the effect of this heat transfer on turbine performance.

This book shows how Microsoft Excel can be used as an effective educational platform for thermofluid analyses. Excel provides a rich library of built-in functions and powerful tools for data visualisation and analysis. The Solver add-in that comes with it enables the students to perform multi-variable optimisation analyses of thermofluid systems. Building on these capabilities, the Excel-based platform for thermofluid analyses presented in this book also utilises the Visual Basic for Applications (VBA) programming language that comes with Microsoft Office. The book shows how VBA can be used for developing additional user-defined functions (UDFs) for supplementing Excel’s built-in functions and introduces an Excel add-in, called Thermax, that provides UDFs for determining the thermodynamic fluid properties. The fluids covered by Thermax include twelve ideal gases, saturated water and superheated steam mixtures, six refrigerants, humid air for psychrometric analyses, and air at standard atmospheric pressure. Property add-ins developed by other academic and research institutions or individuals can be used to extend the range of thermofluid analyses that can be performed with the Excel-based platform.

Free energy changes and equilibrium constants 1. Calculate the standard free-energy changes of the following metabolically important enzyme-catalyzed reactions at 25°C and pH 7.0 from the equilibrium constants given. (a) Glutamate + oxaloacetate ↔ aspartate + α-ketoglutarate K' eq = 6.8 (b) Dihydroxyacetone phosphate ↔ glyceraldehyde-3-phosphate K' eq = 0.0475 (c) Fructose-6-phosphate + ATP ↔ F-1,6-bisphosphate + ADP K' eq = 254 2. Calculate the equilibrium constants K' eq for each of the following reactions at pH 7.0 and 25 o C, using the ∆G o ' values given: (a) Glucose-6-phosphate + H 2 O → glucose + P I ∆G o '=-13.8 kJ/mol (b) Lactose + H 2 O → glucose + galactose ∆G o '=-15.9 kJ/mol (c) Malate → fumarate + H 2 O ∆G o '= +3.1 kJ/mol 3. If a 0.1 M solution of glucose-1-phosphate is incubated with a catalytic amount of phosphoglucomutase, the glucose-1-phosphate is transformed to glucose-6-phosphate until equilibrium is established. The equilibrium concentrations are: Glucose-1-phosphate glucose-6-phosphate 4.5 X 10-3 M 9.6 X 10-2 M Calculate K' eq and ∆G o ' for this reaction at 25 o C. 4. A direct measurement of the standard free-energy change associated with the hydrolysis of ATP is technically demanding because the minute amount of ATP remaining at equilibrium is difficult to measure accurately. The value of ∆G o ' can be calculated indirectly, however, from the equilibrium constants of two other enzymatic reactions having less favorable equilibrium constants: Glucose-6-phosphate + H 2 O → glucose + Pi K' eq = 270 ATP + glucose → ADP + glucose-6-phosphate K' eq = 890 Using this information, calculate the standard free energy of hydrolysis of ATP. Assume a temperature of 25 o C.

This paper describes an Excel add-in called Thermax that determines the thermo-physical properties of various refrigerants used in vapour-compression refrigeration (VCR) systems. Thermax functions that determine the properties of saturated refrigerants do not use equations, but interpolate the data published by ASHRAE. Its functions for superheated refrigerants adopt modified ideal-gas relationships in which the specific heat of the refrigerant is taken from ASHRAE data for saturated vapour refrigerants, but at a reduced pressure. The paper initially verifies these functions by comparison with the values determined with the NIST REFPROP software for two synthetic refrigerants, R1234yf and R410A, and two natural refrigerants, R290 and R744. The add-in is then used to analyse the performance of cascade VCR system with different pairs of refrigerants. Comparisons of the add-in results with those obtained by the EES software confirm the accuracy of the present add-in functions.

Liquid kerosene flows through a Venturi meter, as shown in Fig. P1.36. The pressure of the kerosene in the pipe supports columns of kerosene that differ in height by 12 cm. Determine the difference in pressure between points a and b, in kPa. Does the pressure increase or decrease as the kerosene flows from point a to point b as the pipe diameter decreases? The atmospheric pressure is 101 kPa, the specific volume of kerosene is 0.00122 m3/kg, and the acceleration of gravity is g 5 9.81 m/s2. Answer Known : Kerosone flows throught a venturi meter. Find : The pressure difference between points a and b, in kPa and whether pressure increases or decreases as the kerosene flows from point A to point B as the pipe diamter decreases. Engineering Model : 1) The kerosene is incompressible 2) Atmospheric pressure is exerted at the open end of the fluid columns. Schematic and given data : Analysis : í µí±ƒ í µí±Ž = í µí±ƒ í µí±Ží µí±¡í µí±š + í µí¼Œí µí±”(ℎ í µí± + í µí°¿) = í µí±ƒ í µí±Ží µí±¡í µí±š + í µí¼Œí µí±”ℎ í µí± + í µí¼Œí µí±”í µí°¿ í µí±ƒ í µí± = í µí±ƒ í µí±Ží µí±¡í µí±š + í µí¼Œí µí±”ℎ í µí± Thus,the difference in pressure between point A and point B is : ∆í µí± = í µí±ƒ í µí± − í µí±ƒ í µí±Ž = (í µí±ƒ í µí±Ží µí±¡í µí±š + í µí¼Œí µí±”ℎ í µí± + í µí¼Œí µí±”í µí°¿) ∆í µí± = − í µí¼Œí µí±”í µí°¿

Fishing ports play an important role in the development of fishing activities in Algeria. For their economic, social and environmental development, port authorities actively seek to find ways of operating and managing their ports efficiently and effectively. In this respect, the 41 fishing ports and shelters require development. The investment program includes shipbuilding and repair units, lifting and hauling equipment, filling stations, halls and tides, ice-making factories, refrigerated depots and stores for fishing equipment and spare parts The present study aims to analyze the Algerian fishing ports and to explore factors that ensure their sustainable development in terms of economic efficiency and reduction of their impact on environment.

This paper investigates a source of energy generation which has not been well harnessed in Nigeria: trash (Municipal Solid Waste) to energy. Wastes from nine major cities in Nigeria were considered. First and Second Laws of Thermodynamics were used to determine the power developed from the combustion of the municipal solid wastes. The analysis and evaluation from the work has shown that about 2.26MW of electrical energy could be generated daily from wastes per city. This is quite significant in the quest for alternative/complimentary energy source in Nigeria.
Keywords: Energy generation, solid wastes, combustion.

Various process parameters such as Die temperature, Billet temperature, Flash thickness and Flash width  affect the forging process differently, thus the optimization design of process parameters is necessary to obtain a good product. In this paper an optimization method for the connecting rod closed die forging is proposed based on the finite element method
(FEM) and Taguchi method with multi-objective design. Preform design in forging processes is an important aspect for improving the forging quality and decreasing the production cost. Utilization of designing & simulation tool can reduce iterative & time consuming approaches. The objective of this paper is to obtain an optimapreform shape in the consideration of the influence of the metaflow deformation in closed die forging process. The goal of the simulation and optimization process is to minimize the forging load and produce defect-free forgings. The optimal shape of the billet that gives minimum forging load with complete die filling was obtained after several optimization iterations. Optimization of die temperature, billet temperature, flash thickness & flash width will be performed by DEFORM-3D. Die filling & less wear in the dies will be the required achievements. MINITAB15 software is used for the calculation of S/N ratio & graphs for optimization.

Pressure is one of the most important parameters to be quantified in geological problems. However, in metamorphic systems the pressure is usually calculated with two different approaches. One pressure calculation is based on petrological phase equilibria and this pressure is often termed thermodynamic pressure. The other calculation is based on continuum mechanics, which provides a mean stress that is commonly used to estimate the thermodynamic pressure. Both thermodynamic pressure calculations can be justified by the accuracy and applicability of the results. Here, we consider systems with low differential stress (<1 kbar) and no irreversible volumetric deformation, and refer to them as conventional systems. We investigate the relationship between mean stress and thermodynamic pressure. We discuss the meaning of thermodynamic pressure and its calculation for irreversible processes such as viscous deformation and heat conduction, which exhibit entropy production. Moreover, it is demonstrated that the mean stress for incompressible viscous deformation is essentially equal to the mean stress for the corresponding viscous deformation with elastic compressibility, if the characteristic time of deformation is five times longer than the Maxwell viscoelastic relaxation time that is equal to the ratio of shear viscosity to bulk modulus. For typical lithospheric rocks, this Maxwell time is smaller than c. 10,000 years. Therefore, numerical simulations of long‐term (>10 kyr) geodynamic processes, employing incompressible deformation, provide mean stress values that are close to the mean‐stress value associated with elastic compressibility. Finally, we show that for conventional systems the mean stress is essentially equal to the thermodynamic pressure. However, mean stress and, hence, thermodynamic pressure can be significantly different from the lithostatic pressure.

This paper presents an exergy and environmental assessment of a 1000 metric t/day ammonia production plant based on the steam methane reforming (SMR) process, including the syngas production, purification (CO 2 capture) and compression units, as well as the ammonia synthesis and purge gas treatment. An integrated heat recovery system produces power and steam at three pressure levels, besides exporting hot water, CO 2 and fuel gas, with no additional heat or power consumption being required. Two configurations for ammonia refrigeration process (À20 C) are compared in terms of power consumption. Exergy cost data for upstream processing stages of natural gas is used to calculate the extended exergy cost of the products of the plant, namely ammonia, CO 2 and fuel gas. Moreover, an appropriated methodology is employed to properly allocate the renewable and non-renewable exergy costs, as well as the CO 2 emissions of the reforming, shift and furnace stack among the products of the plant. By considering that the cost reduction of the combustion gases is a linear function of the exergy flow rate reduction in each component of the heat recovery system, an improved allocation of the CO 2 emission cost along the convection train is performed. A breakdown of the total exergy destruction rate of the plant (136.5 MW) shows that about 59% corresponds to the reforming process followed far behind by the ammonia synthesis and condensation (18.3%) and the gas purification units (13.2%). The overall exergy efficiency of the ammonia plant is calculated as 66.36%, which is enhanced by recovering the hydrogen-rich and fuel gases in the purge gas treatment process. The total and non-renewable exergy costs and CO 2 emission cost of the ammonia produced are calculated as 1.7950 kJ/kJ and 0.0881 kg CO2 /MJ, respectively. In addition, a rational exergy cost of 1.6370 kJ/kJ and CO 2 emission cost of 0.0821 kg CO2 /MJ are allocated to the CO 2 gas, which can be supplied as feedstock to an associated chemical plant (urea, methanol, polymers, etc.).

The paper deals with the development and verification of an educational add-in for Microsoft Excel that determines the thermo-physical properties of various synthetic and natural refrigerants used in vapour-compression refrigeration (VCR) systems. To determine the properties of saturated and compressed liquid refrigerants, the add-in uses a linear interpolation function to interpolate the data published by ASHRAE. For superheated refrigerants, the add-in determines the enthalpy and entropy by adopting ideal-gas relationships in which the specific heat is also taken from ASHRAE data, but at a reduced pressure. The paper tests the accuracy of these relationships with different options for evaluating the reduced pressure by comparing their estimates against ASHRAE data for refrigerant R134a. The paper then shows how the add-in can be used to analyse a two-stage compression VCR system and compares the results with those obtained by using another Excel add-in for R134a developed at the University of Alabama. Finally, the paper shows how the add-in can be used with Solver to perform optimisation analyses of a three-stage compression VCR system also using R134a.

With the rapid advancement in the application of innovative computational tools, in particular, parametric design, algorithmically-driven built forms have shown promise in the building industry as evidenced by the exponential growth of three-dimensional printing of building components over the past several years. With the promise to simplify construction, lower cost, increase speed and responsible use of natural resources by incorporating recycled material, parametrized 3D printing represents a credible alternative to current construction practices. To date, the focus of research has been on printing techniques, materials, and structural performance, but many of the promised benefits and opportunities have remained largely unrealized. One of the topics that have received little attention is the study of the thermal performance of the 3D printed walls and envelope components. Unlike traditional construction materials, 3D printed building blocks can be quite complicated. Either by encapsulating variable size and configuration air gaps or embedding circulating fluids, these components tend to be small and require special handling. Conventional apparatuses used to measure the performance of conventional materials may not be suitable for these units because they are large, require large samples or building components. Due to the high cost of testing materials in commercial facilities as well as the delays in testing, small Hot boxes were introduced and studied (Seitz and Macdougall, 2015; Buratti et al., 2016). This paper describes the design and application of a small Hot Box Apparatus developed specifically to test the thermal performance of small and highly detailed samples produced in our labs. Based on several initial experiments, authors discuss in detail the testing procedures, the instrumentation, and the conditions of the tests. The discussion includes errors encountered and elaborates on their sources and how we addressed them in the two experiments that are the basis of this paper. The results revealed that the obtained values from the hotbox were within the acceptable margin of error found in similar laboratory tests. Data collected from testing a rigid polystyrene board of known thermal characteristics were used to estimate parameters used in the determination of the thermal resistivity (R-value) of the ceramic wall. Initial results the R-value of ceramic assembly were promising because of the ability to embed different shapes and sizes of air pockets in the wall. Recommendations include improving the performance of the Hotbox and instrumentation to increase the accuracy of the measurements.

The heat transfer processes in an internal combustion engine can be modeled with a variety of methods. These methods range from simple thermal networks to multidimensional differential equation modeling. Fins are placed on the surface of the cylinder to enhance the amount of heat transfer by convection. For thermal analysis of the engine cylinder fins, it is more beneficial to know the heat dissipation inside the cylinder. Literature survey shows that heat transfer is enhanced through extended surfaces and the heat transfer coefficient is affected by changing cross section of the fins. This study is useful to recognize the better geometry and material for the fins for higher heat dissipation rate and engine cooling. In this project we are taking general material like gray cast iron for engine block. The components are designed by using SOLIDWORKS and analysis is done by ANSYS.

 Pl ea s e r ea d t h e i n s t r u c t i o n s c a r ef u l l y. Yo u a r e a l l o t t ed 5 m i n ut es s p ec i f i c a ll y f o r t h i s p u r p o s e.  Yo u a r e n o t a ll o wed t o l ea v e t h e E xa m i n at i o n Ha ll b ef o r e t h e en d o f t h e t es t .

The cement industry is the most energy-intensive industrial sector in Morocco (69 kep for each ton of production in 2015). To cope with this increase, industrialists have every interest in reducing their energy consumption for significant financial savings and avoidance of significant quantities of greenhouse gases, thus meeting the requirements of the national strategy of energy efficiency.
The present thesis aims to contribute to improving the energy performance of a Moroccan cement plant as a whole. In the first part, a detailed analysis of the material balance with respect to substances and atoms was carried out. An analysis of the measurements collected for this purpose was conducted. Redundant measurements were validated by the Lagrange multiplier technique before being used for the calculation of unmeasured variables. Then, a detailed analysis of energy balances was developed. This made it possible to evaluate the enthalpies of the input and output currents, as well as those related to the fragmentation of the material, in the mills, and to the chemical reactions (combustion, calcination, clinkerisation), in the precalciner and the rotary kiln, as well as heat losses. The energy efficiency of the cement plant studied was thus evaluated at 55%.
In the second part, an exergy analysis across the studied cement plant was performed. It has identified sources of irreversibility occurring within each subsystem and set targets for improving the energy efficiency of the analyzed cement plant. The exergy efficiency of the process was evaluated at 41%. The results of the exergy balances are graphically represented in the exergetic ternary diagram. This one allows visualizing all the aspects of the exergy analysis, namely the irreversibility, the external losses and the exergetic efficiencies of the units composing the process. It has thus revealed two main sources of inefficiency: the preheater / calciner and the two raw mills. This is mainly due to the irreversibilities of the chemical reactions and the large temperature differences between the input and output currents. An advanced exergy analysis was conducted to obtain information on the avoidability or otherwise of irreversibilities. This analysis showed in particular that 81%, 13% and 6% of the irreversibilities of the preheating / calcination and raw milling systems, respectively, are unavoidable. On the other hand, improvements can be made to reduce the avoidable share of these irreversibilities.
Energy efficiency potential improvements were then examined in the light of the scientific literature. The implantation of a waste heat recovery unit connected to the kiln exhaust gas treatment system has been proposed in this sense on the basis of a technical-economic feasibility study.

The traditional approach of using hand-calculations with property tables and charts is an effective method for introducing the principles of thermodynamics, fluid mechanics, and heat-transfer to engineering students. However, the application of these principles in design analyses of fluid-thermal systems requires computer-aided methods for various reasons. A common reason is the need for iterative solutions because of the nonlinear equations involved or because of the inter-dependence between fluid properties and the imposed system forces, pressures, and temperatures. The analyses that deal with complex fluid-thermal systems, such as pipe-networks and heatexchanger networks, are best performed with the aid of computers which are also needed for design optimisation analyses of even the simple fluid-thermal systems like thermal insulation. Although the use of computer-software for fluid-thermal analyses nowadays has become common place in the industry, the disadvantage of these dedicated applications for educational purposes is that they do not allow the student to develop their own analytical models from the basic principles apart from being expensive to acquire and require proper training to use. The aim of this book is to illustrate the use of Microsoft Excel as a modelling platform for design analyses of fluid-thermal systems.

Although the use of computer-software for design analyses of fluid-thermal systems has become common place in the industry, most dedicated industrial applications are not suitable for educational purposes because they do not allow the students to develop their own analytical models from the basic principles apart from being expensive to acquire and require proper training to use. In this respect, general-purpose applications such as Microsoft Excel can be more useful than the dedicated industrial applications. This book illustrates the use of an Excel-based modelling platform for optimisation analyses of fluid-thermal systems. While Excel with its user-interface, built-in functions, and graphical tools is the backbone of the modelling platform, what makes the platform adequate for optimisation analyses of fluid-thermal systems are (i) the Solver add-in that comes with Excel, (ii) an add-in called Thermax developed by the author for determining fluid properties, and (iii) Visual Basic for Applications (VBA) programming language that also comes with Excel. While the functions provided by Thermax are adequate for all the analyses presented in this book, VBA is useful for the development of additional custom functions if required. The developers of the MIDACO solver have made available a free-to-download version for Excel users that is used for the multi-objective optimisation analyses presented in the last three chapters of the book.

A new exergy-based formulation is derived for the  assessment of the aerothermopropulsive performance of civil aircraft. The choice of exergy is motivated by its ability to provide a well-established and consistent framework for the design of aerospace vehicles. The output of the  derivation process is an exergy balance between the exergy supplied by a propulsion system or by heat transfer, the mechanical equilibrium of the aircraft, and the exergy outflow and destruction within the control volume. The theoretical formulation is subsequently numerically implemented in a Fortran code named ffx for the post-processing of CFD-RANS flow solutions.
Unpowered airframe configurations are examined with grid refinement studies and a turbulence model sensitivity analysis is performed. A numerical correction is introduced and calibrated to obtain an accuracy similar to the near-field drag method. The code is thereby validated against well-tried methods of drag prediction and wind-tunnel tests, when available.
The investigation of powered configurations demonstrates the ability of the approach for assessing the performance of configurations with aerothermopropulsive interactions. First, the formulation is validated for the simple case of a turbojet engine for which consistent figures of merit are exhibited. The method is also proved robust for assessing the overall performance of a boundary layer ingesting propulsion system placed on the upper surface of a simplified blended wing-body architecture. Moreover, this configuration enables the investigation of thermopropulsive interactions by the transfer of heat upstream of the propulsion system.
Subsequently, the integration of a heat exchanger on a commercial aircraft is examined for which the exergy point of view provides guidelines for an efficient design. The ability of the formulation to consistently assess all these types of subsystems is a clear benefit of this method.

Phase change material (PCM) is promising media for thermal energy storage owing to its extensive value of latent heat (140-970 KJ/Kg). However, thermal conductivity of PCMs is too low which obstructs energy storage and retrieval rate. In recent days, thermally enhanced PCMs are considered promising materials for efficient heat transfer in many applications. This article designates the review on improved thermal properties and heat transfer of PCMs by using porous materials. Enhanced heat transfer of PCMs can be achieved using extended surfaces (triangular, conical, square, and rectangular fins), heat pipes, and addition of highly conductive nanoparticles (e.g. Cu, Al 2 O 3 , Au, SiC, SiO 2 and TiO 2). Major focus of this article is to study the enhanced heat transfer of PCMs through metallic (copper, nickel, and aluminum) and carbon based (carbon, graphite and expanded graphite) porous materials/foams. Effects of porosity and pore density on heat transfer, thermal conductivity, specific heat, latent heat and charging/discharging time are critically reviewed. Porous materials/foams are reported to be efficient for heat transfer/thermal conductivity enhancement by 3-500 times. Furthermore, correlations to find the effective thermal conductivity of PCM/foam are reported. Important applications of PCM/foam reported by different researchers are also discussed in this paper. Finally, conclusions and recommendations are presented to highlight the research gap in this area.

"Generally, in steel processing systems, steels are heated via induction or combustion furnaces. Natural gas fired furnaces have installation costs advantage
while the induction furnaces have the advantages of less scale formation on the surface of the workpiece as well as less environmental pollutions. The
operation cost of both systems is a vital argument to be solved. In this paper, a natural gas fired and induction heating furnaces of a forging process were
studied. Thermodynamic analysis was performed for the furnaces which heat the steel workpiece up to 1,300 °C. The energy performances of both
systems were analyzed and compared. It is concluded that, instead of a natural gas fired or an induction furnace, a hybrid furnace may save more energy
and cost."