Heat Exchange Area Research Articles

Evaporative and non-evaporative droplet impact on a heated phase change material pool: A comparison between ethanol, acetone, and distilled water

The interaction between liquid droplet and phase change material (PCM) underlies the direct contact approach, which is an efficient way for precipitating the melting and solidification processes of PCMs. In this experimental research, to comprehend the direct contact method more profoundly, the impingement of a single droplet on the heated paraffin pool, having a temperature of 70–95 °C, is scrutinized systematically for the first time. Droplet impact solidifies a portion of the pool and may lead to droplet evaporation. Acetone, ethanol, and distilled water are exploited as droplet liquids, whose diameter and impact velocity range from 2.32 to 3.36 mm and from 1.70 to 2.28 m/s, respectively. Through impact visualizations, six distinct regimes are observed, whose regime maps are constructed. Moreover, the effects of fluid properties, pool temperature, and the Weber number on the evolution of crater and jet, crater depth, crater shape, and solidified PCM area (A) generated after the impingement are investigated. It is ascertained that the low PCM temperature instigates the coalescence phenomenon regardless of the Weber number. Additionally, the crater depth is a function of the PCM temperature, Weber number, and Ohnesorge number; thus, a dimensionless correlation is proposed for the maximum crater depth. Furthermore, droplet evaporation augments the extracted heat from the paraffin, provoking a more sizeable solidified area. Interestingly, though absorbing the greatest amount of heat from the PCM, ethanol droplet generates a smaller solidified area than acetone since acetone favorably spreads on the pool surface, enhancing the effective heat exchange area.

Optimization of an integrated system including a photovoltaic/thermal system and a ground source heat pump system for building energy supply in cold areas

The photovoltaic (PV) collectors tend to overheat in summer, which reduces the efficiency of power generation. The unbalanced heating and cooling loads cause the ground source heat pump (GSHP) system to operate unstably in severe cold areas. To solve the above two problems simultaneously, an integrated system including a photovoltaic/thermal system and a ground source heat pump system (PVT-GSHP) was proposed, which had an extremely high energy utilization efficiency. However, the complex variation of cooling and heating loads was influenced by meteorological conditions over time. The demand of efficient operation and good economy of the system challenged the optimal configuration and control strategy among multiple energy sources, which was investigated in this study. A dynamic model of the PVT-GSHP system based on TRNSYS was developed and the corresponding control strategy was formulated. The genetic algorithm was used to optimize the matching of buried pipe lengths and PVT collector areas. The effects of different matching on the system parts and the whole performance were analyzed. The results show that increasing the PVT collector area can increase the ground temperature and shorten the buried pipe length, but it is not good for summer cooling, thus there is an optimal match. Compared with two independent systems of the traditional GSHP system and PV generation system, the PVT-GSHP system has excellent advantages and application prospects because it has 48.3% reduction in the total buried pipe length, 68.89% reduction in the footprint area of ground heat exchangers, 10% increase in the heating coefficient of performance (COP) and 72.3% reduction in life circle cost. This study provides theoretical support for the optimal design of the PVT-GSHP systems and similar complementary multi-energy systems.

CFD MODELLING OF THERMAL AERODYNAMIC CHARACTERISTICS OF COMPOSITE FLAT-OVAL TUBE WITH INCOMPLETE CORRUGATED FIN

In the article thermo-aerodynamic characteristics of the original design of a heat exchange surface - a flat-oval tube with incomplete corrugated fins, which can be used for the modernization of heat exchange equipment, are studied. The purpose of the work is a preliminary assessment of the efficiency of flat-oval tubes with incomplete corrugated fins and obtaining an empirical dependence for calculation using CFD modeling. The object of the study is forced convection during transverse washing of a composite flat-oval tube with incomplete corrugated fins. The subject of the study is heat transfer and aerodynamics during transverse washing of a composite flat-oval tube with incomplete corrugated fins. In the work, the values of the dimensionless coefficient of heat transfer and pressure loss are obtained, as well as the calculated dependence for determining the coefficient of heat transfer and aerodynamic resistance of the mentioned types of tubes is presented. Data verification was carried out with a smooth tube and a tube with spiral fins. The scientific novelty of the work is the establishment of the fact that flat-oval tubes with incomplete corrugated fins have a higher heat transfer coefficient compared to smooth tubes (by 45 – 50 % in average) and spiral-ribbed tubes (by 25 – 30 % in average) with simultaneous increasing of aerodynamic resistance by 25 – 30 % at the same flow rate of the heat carrier. Practical application of the obtained results allows designers to increase the surface area of heat exchange, which makes these tubes prospective for using in power engineering and industry, in particular, for dry cooling towers of nuclear power plants and thermal power plants, for boiler heat exchangers, for gas turbine installations, etc.

Global optimization of the design of intensified shell and tube heat exchanger using tube inserts

AbstractThis paper investigates global optimization of the detailed design of intensified shell and tube heat exchangers using two tube inserts: twisted tape and coiled wire. Three objectives, including heat exchanger area, total annualized cost, and environmental impact, are respectively minimized. All the design variables are considered as the ones that have discrete values based on their physical nature or manufacturing standards. We present, for the first time, a tailored global optimization approach for the design of intensified shell and tube heat exchanger: Set trimming procedure. We compare the computational performance of our set trimming procedure, exhaustive enumeration, and commercial solvers. The proposed three objectives have certain competitive relationships and multi‐objective optimization is performed to analyze the conflicts among them. Two literature examples are tested for illustration purposes. The solution results indicate that the intensified heat exchanger designed using tube inserts compares well to the regular heat exchanger using plain tube. Compared with commercial solvers, set trimming procedure runs fast and can converge to global optimum without initial value. The pareto‐optimal solutions of multi‐objective optimization provide holistic trade‐offs between different objectives, hence helping the process designer make proper decisions for the design of intensified shell and tube heat exchangers.

Performance Analysis of Organic Rankine Cycle with Internal Heat Regeneration: Comparative Study of Binary Mixtures and Pure Constituents in Warm Regions

There are various organic compounds that can be utilized in the organic Rankine cycle as working fluids. The selection of a suitable working fluid is complicated due to the large number of options and factors affecting the choice, such as thermodynamic properties, environmental impact, cost, etc. This study evaluates seven different pure organic compounds and twenty-one of their binary zeotropic mixtures as potential working fluids for the organic Rankine cycle powered by a heat source at 200 °C. The pure organic fluids show higher exergy efficiency, higher specific net power output, and lower heat exchange area requirements compared to the binary mixtures. Among the pure fluids, RE347mcc performs the best in terms of exergy efficiency, followed by neopentane, isopentane, and pentane. Cyclopentane exhibits the highest power production capacity per unit mass flow rate of the working fluid. Two mixtures, pentane/Novec 649 and cyclopentane/Novec 649, showed significantly higher exergy efficiency than their individual components, but at significantly lower specific power production capacity. The study presents an interesting trade-off between exergy efficiency and heat exchange area, indicating that a small increase in exergy efficiency can lead to a large decrease in the required heat exchange area. The outcomes of this study can help in selecting suitable working fluids for ORC operation with a heat source at 200 °C.

Experimental Study on the Effect of Pitch Sloshing on the Heat Transfer and Pressure Drop of an LNG Spiral-Wound Heat Exchanger.

With the development and utilization of offshore liquefied natural gas, it is increasingly important to study the influence of the heat transfer performance of a spiral-wound heat exchanger under sloshing conditions. This study focused on the effects of different sloshing amplitudes and sloshing periods on the heat transfer and pressure drop performance of a heat exchanger. Through experimental research, the results showed that the fluctuation of the UA (U is the heat transfer coefficient; A is the heat exchange area) value first increased and then decreased with an increase in the sloshing amplitude. The UA value increased by 12.92% and decreased by 42.03% compared to the static value at 3 and 9°, respectively. The fluctuation in the UA value first decreased and then increased with an increase in the sloshing period. The UA value decreased by 36.66% and increased by 10.82% slowly compared to the static value when the sloshing period was 6 and 20 s, respectively. Based on this, a mathematical model of heat transfer under the condition of pitch sloshing was established.

Selection of Organic Fluid Based on Exergetic Performance of Subcritical Organic Rankine Cycle (ORC) for Warm Regions

The organic Rankine cycle (ORC) exhibits considerable promise in efficiently utilizing low-to-medium-grade heat. Currently, there is a range of organic fluids available in the market, and selecting the appropriate one for a specific application involves considering factors such as the cycle’s thermodynamic performance, plant size, and compatibility with turbomachinery. The objective of our study is to examine the exergetic performance of the ORC with internal heat regeneration. We analyze 12 different organic fluids to evaluate their suitability based on parameters like exergy efficiency and heat exchange area requirements. Additionally, we investigate the need for internal heat regeneration by comparing the overall exergy performance with a simpler ORC configuration. To ensure broad applicability, we consider source temperatures ranging from 150 to 300 °C, which are relevant to industrial waste heat, geothermal sources, and solar energy. For each case, we calculate specific net power output and the UA value (heat exchanger conductance) to gain insights into selecting the appropriate organic fluid for specific source temperatures. Cyclohexane, benzene, isopropyl alcohol, and hexafluorobenzene show poor exergy efficiency due to their high boiling points. Pentane and cyclopentane provides the highest exergy efficiency of 62.2% at source temperature of 300 °C, whereas pentane is found to be the most suitable at source temperatures of 200 and 150 °C with exergy efficiency of 67.7% and 61.7%, respectively. At 200 °C source temperature, RE347mcc achieves 65.9% exergy efficiency. The choice of organic fluid for a given heat source is highly influenced by its critical properties. Moreover, the normal boiling temperature of the organic fluid significantly impacts exergy destruction during the condensation process within the cycle.

Research of geometrically distinct automobile radiators in terms of thermal-hydraulic characteristics

The fin-and-tube heat exchangers are traditionally used in the automobile cooling system to maintain a proper function and service life of an engine and its components. In the study, the effect of coolant and radiator mileage on thermal–hydraulic characteristics of radiators was investigated. Two types of automobile radiators with different heat exchange areas, mileage, number and size of fans, tube configurations, and coolant mileage were experimentally studied. The local and average Nusselt number of the tubes and fins, heat flux, pressure drop, and efficiency index JF were evaluated based on the numerical studies where the turbulent flow was solved by the k-ω SST model using the ANSYS Fluent software. The shortest cooling time was achieved at the new radiator II with the coolant mileage of 0 km (4 min), while the longest one was achieved at the old radiator II with the coolant mileage of 50,000 km (8.5 min). The radiator II with two fans achieved half the time of cooling when running both fans compared to the only one. The studied range of the coolant and radiator mileage do not have any significant effect on the fault-free operation of the engine cooling system. The efficiency index JF for the new radiator I with the coolant mileage of 0 km is 0.86 – 1.90% higher for the tubes and 0.42 – 1.22% higher for the fins compared with the other investigated radiator and coolant mileages.

Numerical and experimental study of natural convection heat transfer on flat and corrugated plates

PurposeThe purpose of this study is to numerically and experimentally investigate the natural convection heat transfer in flat plates and plates with square, trapezoidal and triangular corrugations.Design/methodology/approachThis work is an extension of the previous studies by Verderio et al. (2021a, 2021b, 2021c, 2021d, 2022a). An experimental apparatus was built to measure the plates’ temperatures during the natural convection cooling process. Several physical parameters were evaluated through the experimental methodology. Free and open-source computational tools were used to simulate the experimental conditions and to quantitatively and qualitatively evaluate the thermal plume characteristics over the plates.FindingsThe numerical results were experimentally validated with reasonable accuracy in the range of studied for the different plates. Empirical correlations of , and , with good accuracy and statistical representativeness, were obtained for the studied geometries. The convective thermal efficiency of corrugated plates (Δη), as a function of , was also experimentally studied quantitatively. In agreement with the findings of Oosthuizen and Garrett (2001), the experimental and numerical results proved that the increase in the heat exchange area of the corrugations has a greater influence on the convective exchange and the thermal efficiency than the disturbances caused in the flow (which reduce ). The plate with trapezoidal corrugations presented the highest convective thermal efficiency, followed by the plates with square and triangular corrugations. It was also proved that the thermal efficiency of corrugated plates increases with .Practical implicationsThe results demonstrate that corrugated surfaces have greater thermal efficiency than flat plates in heating and/or cooling systems by natural convection. This way, corrugated plates can reduce the dependence on auxiliary forced convection systems, with application in technological areas and Industry 4.0.Originality/valueThe empirical correlations obtained for the corrected Nusselt number and thermal efficiency for the corrugated plate geometries studied are original and unpublished, as well as the experimental validation of the developed three-dimensional numerical code.

Optimization Design of an Intermediate Fluid Thermoelectric Generator for Exhaust Waste Heat Recovery

The intermediate fluid thermoelectric generator (IFTEG) represents a novel approach to power generation, predicated upon the principles of gravity heat pipe technology. Its key advantages include high-power output and a compact module area. The generator’s performance, however, is influenced by the variable exhaust parameters typical of automobile operation, which presents a significant challenge in the design process. The present study establishes a mathematical model to optimize the design of the IFTEG. Our findings suggest that the optimal module area sees substantial growth with an increase in both the exhaust heat exchanger area and the exhaust flow rate. Interestingly, the optimal module area appears to demonstrate a low sensitivity to changes in exhaust temperature. To address the challenge of determining the optimal module area, this study introduces the concept of peak power deviation. This method posits that any deviation from the optimal module area results in an equivalent power deviation. For instance, with an exhaust heat exchanger area of 1.6 m2, the minimum peak power deviation is 27.5%, corresponding to a design module area of 0.124 m2. As such, the actual output power’s deviation from the maximum achievable output power will not exceed 27.5% for any given set of exhaust parameters. This study extends its findings to delineate the relationship between the optimal design module area and the exhaust heat exchanger area. These insights could serve as a useful guide for the design of future power generators.

HENS Unchained: MILP Implementation of Multi-Stage Utilities with Stream Splits, Variable Temperatures and Flow Capacities

In this paper, we present an extended heat exchanger synthesis superstructure (HENS) formulation to consider streams with variable temperatures and flow capacities using mixed-integer linear programming (MILP). To keep the problem tractable and to leverage the potential of state-of-the-art MILP solvers, piecewise-linear models with logarithmic coding are used. Allowing for variable utility parameters within a feasible technical range, instead of a priori defined ones, removes limitations of the HENS. Increasing the utility’s degree of freedom offers advantages when sensible heat from, for example, flue gas, thermal oil, or water is used. Moreover, utilities are no longer limited to single-stage heat transfer without stream splits at the stream ends, generating opportunities for efficiency enhancement. We consider three representative case studies to evaluate the performance of the unchained HENS method. Our results show that representing utilities as streams in the HENS optimization problem leads to lower total annual costs (TAC). Significant cost savings arise due to more efficient utility placement, heat transfer, and smaller heat exchanger areas. The results indicate that this method can lead to cheaper and more resource-efficient HEN and thus positively contribute to the environment.

Thermo-economics evaluation of crude oil heating arranged with finned coil in floating roof tank

The crude oil in the floating roof tank is troubled by the problem of gelling at low temperature which eventuate the storage of crude oil needs to be assisted by coil heating technology. However, the low heating performance of the technology restricts the benefits of crude oil storage due to the limited heat exchange area between coil and crude oil. A finned coil heating technology is proposed to address the above issues. The influence of the fin number and the inclination angle on the heating effect of crude oil is analyzed by FLUENT software. The results indicate that increasing the number of fins has a more significant effect on improving crude oil temperature than adjusting the inclination angle. The increase in the number of fins shows a nonlinear relationship with the increase in crude oil temperature, and there is an optimal combination for coils with different fin numbers and different inclination angles. From the perspective of thermos-economics, the optimal arrangement is the coil with 2 fins inclined at 60°, which can increase the crude oil zone average temperature by 2.83% (1.021 °C), and reduce the temperature inhomogeneity by 6.31%, as well as increase the cost saving by 91.65%, compared with the bare coil inclined at 0° (i.e. existing engineering formation). This paper is of great significance for ensuring the safe storage of crude oil.

Improving control of Fully Heat-Integrated pressure Swing distillation through partially flooded Reboiler/Condenser

The binary mixture formed by acetonitrile (MeCN) and water (H2O) presents a minimum azeotrope highly sensitive to pressure variations, which can be separated through pressure-swing distillation (PSD), which is considered a very energy efficient process due to the possibilities of heat integration, in particular integration between the condenser and the reboiler of columns, known as Fully Heat-Integrated PSD (FHIPSD); in addition to being friendly from the environmental point of view. Despite promoting energy gains, integration reduces the freedom to control the process and, consequently, allows pressure fluctuation in the high-pressure column. This study evaluates the use of a partially flooded reboiler/condenser as a way to recover a degree of freedom of the process. The ability to maintain the purity specifications of products in two FHIPSD control configurations (conventional and with partially flooded reboiler/condenser) was evaluated for disturbances in the flow rate and feed composition. The use of a partially flooded reboiler/condenser allows controlling the heat exchange area by manipulating the level of liquid in the heat exchanger. The results showed that the partially flooded reboiler/condenser configuration promoted significant reductions in the steady state error values in the MeCN composition; and for positive flow disturbances, the steady state error value was reduced from 0.109 mol% to 0.004 mol%.

A modified 3D-EDFM method considering fracture width variation due to thermal stress and its application in enhanced geothermal system

The successful utilization of hot dry rock is contingent upon the implementation of the development of the enhanced geothermal system (EGS) to create a complex fracture network.However, the fracture is affected by thermal stress, which results from the temperature difference between low-temperature fluid and high-temperature rock. To address this issue, a dynamic model of fracture width that takes thermal stress into account has been proposed. This model is based on the modified three-dimensional embedded discrete fracture model (EDFM) method and is solved by finite volume method coupling local boundary element.This model is based on the modified three-dimensional EDFM method and is solved by finite volume method coupling local boundary element. The proposed method has been validated through comparing with results obtained from commercial finite element software. Furthermore, the method is applied to the simulation of EGS to analyze the parameter sensitivity of the mass and heat transfer process. The results indicate that neglecting the impact of thermal stress on fracture width leads to an underestimation of produced energy. The shape and inclination angle of fractures significantly affect the mass and heat transfer in the reservoir.Moreover, the shape and inclination angle of fractures significantly affect the mass and heat transfer in the reservoir. A larger heat exchange area results in faster temperature decreases and increased heat energy production. High thermal diffusion coefficients improve the performance of EGS, while an increase in the thermal expansion coefficient of rock accelerates thermal breakthrough and enhances heat energy production. It has been found that maintaining a small pressure difference between injection and production and using low-temperature injection water can prolong the system lifetime and increase the final heat energy produced. This study presents an efficient numerical simulation method for mass and heat transfer in fractured reservoirs, expands the original EDFM method's application range and enhances calculation accuracy..

Fundamental optimization of steam Rankine cycle power plants

This paper introduces a mathematical model for the design and fundamental optimization of steam Rankine cycle (SRC) power plants. The model assumes that the plant irreversibilities are predominant in the heat exchangers, thus exergy destruction in the turbine, pump, fittings, tubes and other internal components are neglected. The NTU-effectiveness method was utilized to model the heat exchangers, and water was considered as the working fluid, which changes phase in both heat exchangers. Acknowledging that entropy is generated in any physical system, the fundamental optimization problem selected the dimensionless net power output, and second law efficiency as the objective functions to be maximized, after the identification of plant geometric and operating parameters to be optimized based on the intersection of asymptotes method, subject to a fixed total heat exchangers area realistic physical constraint, i.e., for a finite size plant. As a result, two levels of optimization were identified: i) the working fluid to hot stream mass flow rate ratio, M, and ii) the steam generator, xH, and condenser, xL, area fractions of the plant fixed total heat exchangers area. The model was experimentally validated for a heat recovery driven power plant. Sharp maxima were obtained in both levels, which is illustrated with a base case by ∼ 60 % second law efficiency variation in comparison to the obtained maximum for 0.05 < M < 0.25 in the first optimization level, and ∼ 30 % for 0.2 < xH < 0.7 in the second optimization level, so that (xf,H,xfg,H,xg,H)2wo=(0.14,0.13, 0.23), with (M,xH)2wo=(0.16,0.5), in the base case considered in this study. The two-way optima results sensitivity to several plant geometric and operating parameters were thoroughly investigated. The optimized parameters are shown to be robust with respect to several system’s design and operating conditions. Therefore, the herein reported fundamental optimization results are important for whatever actual SRC power plant.

Development of selection criteria of zeotropic mixtures as working fluids for the trans-critical organic Rankine cycle

The trans-critical organic Rankine cycle (TCORC) can achieve a better thermal match in the heating process of the working fluid compared to the subcritical cycle. By using zeotropic mixtures as working fluids, the thermal match in the cooling process can be further optimized, reducing the system's irreversibility. As the selection criteria are not systematically formulated, screening zeotropic mixtures for the TCORC is challenging. In this work, the thermodynamic and thermo-economic analysis was carried out to investigate how the thermal match in the heating/cooling processes affects the system performance, which is represented by the overall exergy efficiency and the levelized energy cost. Results show that the mixture's critical temperature is a key factor influencing the system performance. Then, the mixtures having a proper condensation temperature glide can further improve the system performance. The thermo-economic analysis shows that the mixtures selected according to these criteria can also provide better thermo-economic performance, although the heat exchanger area has been enlarged during the improvement of the thermal match in heat exchangers.

Heat transfer rate prediction and performance optimization of CO2 air cooler in refrigeration system

In order to determine the heat transfer rate of CO2, heat transfer criterion equations were selected and validated using experiment data. The impacts of various operating conditions and structural parameters on CO2 air coolers were numerical simulation investigated. The results show that the inlet dryness and mass flow rate are proportional to heat transfer coefficient (HTC) and pressure drop (PD). When the mass flow reaches 240 kg/h, CO2 reaches the critical state, and further increasing the mass flow rate has little effect on the HTC. The HTC reaches its maximum value at a dryness of 0.2, after which, it decreases due to the flow pattern changing from wavy/intermittent flow to annular flow. Moreover, the tube spacing, tube diameter, and fin spacing affect the HTC, heat exchange area, and heat exchange capacity differently. Hence, a thoroughly consideration of the structural parameter design is crucial during the actual design process.

Entropy generation analysis of electroosmotic mixed convection flow in vertical microannulus with asymmetric heat fluxes

Flow formations and heat transfer of electroosmotic flow have significant applications in area of heat exchanger and recently for chemical separation at microlevel. Therefore in this article, exact solutions for entropy generation rate of electroosmotic mixed convection flow in a vertical microannulus subject to asymmetric heat fluxes are presented. Closed form solutions in terms of Bessel's functions are obtained for electric potential, fluid velocity, temperature, skin-friction, Nusselt number and entropy generation after transforming the governing equations into their corresponding dimensionless forms. The obtained solutions are graphically represented using MATLAB software in order to ascertain the role of various pertinent parameters entering flow formation and heat transfer. Results obtained showed that entropy generation rises with increase in radius ratio and electroosmotic force but decreases with increase in slip and buoyancy parameters. Also, irreversibility due to fluid friction or applied electric field is sufficient to dominant the overall entropy generation rate in the presence of strong buoyancy force. On application point of view, fluid velocity, temperature distributions, skin-friction, volumetric flow rate, Nusselt number and entropy generation rate can be optimized by careful selection of governing parameters.

Solidification of nanoparticle-based PCM in a fin-aided triplex-tube energy storage system for cooling applications

Accomplishing a better solidification rate to enhance the Thermal Energy Storage (TES) systems' performance is crucial. One such storage system is the Triplex-tube heat exchanger (TTHX), which is preferable due to its larger heat exchanger area that makes the phase change rate faster. The present study demonstrates a combination of different heat transfer enhancement techniques to improve the performance of the TTHX system. The heat transfer performance of the entire solidification process in the heat exchanger is numerically studied. The system is designed for low-temperature cooling applications with water as PCM placed in between the annulus region of the TTHX. Fins have been employed to enhance the low heat transfer rate due to the poor thermal conductivity of the water as PCM. The effect of incorporating maximum fin length between the annulus region on the discharging performance is evaluated. In this regard, two fin arrangements – attached and detached are investigated. The influence of different cooling methods, namely both-side, inside and outside, are evaluated for mentioned fin arrangements in terms of the required solidification time, liquid–solid interfaces, and heat transfer rate. The impact of including CuO nanoparticles on the thermal and flow structure under different volume fractions is investigated. The results demonstrate that detached fins perform superior under a given heat transfer fluid temperature among other fin cases. In comparison, both-side cooling expedites the process better than other cooling methods. Inclusion of 7% nanoparticles along with fins results in an even faster freezing process, which helps to reduce full solidification time in all cases by nearly 29% and 25% in attached and detached fins, respectively.

Design improvements for ammonia-fed SOFC systems through power rating, cascade design and fuel recirculation

In this paper, design strategies for improving electrical efficiency, thermal design and fuel utilization of an ammonia-fed SOFC are investigated. Three strategies are presented to improve system performances: (i) the introduction of an additional stack to distribute the power i.e. power rating, (ii) the evaluation of the anode off gasses recirculation and (iii) the use of the off gasses to operate a cascade stack (re-powering), where the anode flue gas is recuperated. A system design that integrates these new features is modelled with zero-dimension thermodynamic equations. The three strategies were evaluated for net system efficiency and the heat exchanger area as main design parameters. The power rating allows to reduce the heat exchanger surface while the recirculation and repowering are suitable to increase system efficiency. With an integration of the three solutions, it is possible to achieve an increase in net efficiency from 52.1% to 66% and a reduction in heat exchanger surface area of 67% compared to the reference design that does not consider any of the proposed design strategies.