A common occurrence in many practical systems is that the desired result is known or given, but the conditions needed for achieving this result are not known. This situation leads to inverse problems , which are of particular interest in thermal processes. For instance, the temperature cycle to which a component must be subjected in order to obtain desired characteristics in a manufacturing system, such as heat treatment or plastic thermoforming, is prescribed. However, the necessary boundary and initial conditions are not known and must be determined by solving the inverse problem. Similarly, an inverse solution may be needed to complete a given physical problem by determining the unknown boundary conditions. Solutions thus obtained are not unique and optimization is generally needed to obtain results within a small region of uncertainty. This review paper discusses several inverse problems that arise in a variety of practical processes and presents some of the approaches that may be used to solve them and obtain acceptable and realistic results. Optimization methods that may be used for reducing the error are presented. A few examples are given to illustrate the applicability of these methods and the challenges that must be addressed in solving inverse problems. These examples include the heat treatment process, unknown wall temperature distribution in a furnace, and transport in a plume or jet involving the determination of the strength and location of the heat source by employing a few selected data points downstream. Optimization of the positioning of the data points is used to minimize the number of samples needed for accurate predictions.

A model for the quantum Brayton refrigerator that takes the harmonic oscillator system as the working substance is established. Expressions of cooling load, coefficient of performance (COP), and ecological function are derived. With numerical illustrations, the optimal ecological performance is investigated. At the same time, effects of heat leakage and quantum friction are also studied. For the case with the classical approximation, the optimal ecological performance, and effects of heat leakage and quantum friction are also investigated. For both general cases and the case with classical approximation, the results indicate that the ecological function has a maximum. The irreversible losses decrease the ecological performance, while having different effects on the optimal ecological performance. For the case with classical approximation, numerical calculation with friction coefficient μ = 0.02 and heat leakage coefficient C e = 0.01 shows that the cooling load (R E ) at the maximum ecological function is 6.23% smaller than the maximum cooling load (R max ). The COP is also increased by 12.1%, and the exergy loss rate is decreased by 27.6%. Compared with the maximum COP state, the COP (ɛ E ) at the maximum ecological function is 0.55% smaller than the maximum COP (ɛ max ) and that makes 7.63% increase in exergy loss rate, but also makes 6.17% increase in cooling load and 6.20% increase in exergy output rate.

Many solar technologies are developed to encourage the usage of solar energy throughout the world. The Solar chimney power plant (SCPP) is a newfangled technology that utilizes solar energy to generate more clean energy. This paper presents a new design of the SCPP turbine based on the aerodynamic optimization approach of a wind turbine with a diffuser. To calculate the required design parameters, a comprehensive mathematical model has been developed, which has an ability to describe the flow inside solar chimneys. An iteration algorithm is implemented for solving blade element theory with a diffuser to obtain the optimization of the turbine blade chord and twist angle distributions in the presence of a diffuser. The comparison of the mathematical model results and experimental data of Manzanares prototype reveal the good agreement, validating our mathematical model. The present design suggests that the power output could be increased by 15%. Our conclusion is that the Blade Element Theory with diffuser has an ability to design efficient turbine suitable for working within SCPP.

Liquefied Petroleum Gas (LPG) is commonly used in domestic kitchen due to its low health and environmental impacts and high heat content compared to other traditional fuels. Growing demand of LPG, notwithstanding its limited reserve, influences the need for performance improvement of the LPG cook stoves. In a LPG cook stove, the fuel-air mixture is prepared in a self-aspirated burner and burns as a rich premixed flame at the burner head. The fuel-air ratio of the reactant mixture influences the burning characteristics and thermal efficiency of the cook stove. This part of work deals with a numerical study of flow and mixing characteristics in the mixing tube and burner assembly of a domestic LPG cook stove. The fuel is injected axially through a narrow nozzle inside the mixing tube causing entrainment of ambient air through the side-ports and end-port. The effects of different side-port geometry, nozzle position, inlet fuel pressure and nozzle throat diameter on the air ingress have been systematically investigated and the optimum design has been identified. Results of the study provide important information on the design of the practical nozzle and mixing tube assembly of high-efficiency LPG stoves.

In this paper, optimization of the location and the geometry of a vortex promoter located above in a finned surface in a channel with eight heat sources is investigated for a Reynolds number of 12,500 < Re < 27,700. Heat transfer rates and the corresponding Nusselt number distributions are studied both experimentally and numerically using different vortex promoter geometries (square, circular, and triangular) in different locations to illustrate the effect of vortex promoter on the fluid flow. Optimization study considered a range of following parameters: blockage ratio of 0.30 < (y/C) < 0.45 and interpromoter distance ratio of 0.2277 < (x/L) < 0.3416. Results show that fins over which rectangular and circular promoters are integrated perform better in enhancing the heat transfer. According to the numerical and experimental results, higher blockage ratios cause significantly higher heat transfer coefficients. According to the observations, as the interpromoter distances increase, shedding gains strength, and more turbulence is created. All vortex promoters enhance heat transfer resulting in lower temperature values on the finned surface for different (y/C) and (x/L) values and Reynolds numbers. The use of promoters enhances the heat transfer, and the decrease in the maximum temperature values is recorded on the finned surface changing between 15% and 27%. The biggest decrease in maximum surface temperature value is 500 K–364 K and observed in circular promoter case with (y/C) = 0.43, (x/L) = 0.3416, and Reynolds numbers of 22,200.

Genetic algorithms (GAs) are considered to be one of the main types of evolutionary algorithms (EAs) and are being increasingly used in various engineering design applications. To a large extent, plate-fin heatsinks are used in the thermal management of compact electronic equipment and data centers. The shape optimization of the heatsinks is not rigorously investigated during the design process of high power electronics. Any improvements in the effectiveness of the heatsinks impact the energy consumed by large-scale information communication technology (ICT) facilities including data centers and telecommunication systems and promote a more sustainable use of raw materials. This paper investigates the optimization of plate-fin heatsinks by modifying the fin layout in a forced crossflow using a multi-objective genetic algorithm (MOGA) combined with computational fluid dynamics (CFD) simulations. The main objective is to improve the heat dissipation rate by modifying geometric parameters, i.e., the number, arrangement, and orientation of fins. For a generic heatsink test case, the optimized performance is examined in terms of thermal resistance, turbulence intensity, pumping power, coefficient of performance, and Chilton–Colburn j-factors. Among all of the cases investigated, the input parameter optimization configurations which coupled and rotated fins in groups of ten proved to be the most successful. For one case, an 18% increase in the effectiveness of heat dissipation is reported. However, when weight reduction was considered by dividing by the unit mass, the designs in one of the investigated families which remove a number of fins from the heatsink outperformed the rest, achieving improvements of 65% over the baseline.

An experimental study presents a new innovative cyclone combustor, known as the Three-Way Swirling Combustion (TSC), utilizing non-pulverized wood biomass. The study shows that the combustor reached near complete combustion, as evident in the measurements of CO and NOx emissions, and the excess air ratio. It also demonstrates the unique features of the TSC combustor, which includes an air curtain insulation effect with a high ash removal rate that reduces clinker and slag formation, alongside a chamber that does not need a refractory brick. It compares against conventional combustion technology, such as the stoker and the fluidized bed in terms of the amount of emission gases, maximum temperature, and excessive air ratio. Six geometrical and operational design criteria of the TSC for wood biomass combustion are identified for future work of design optimization. Ultimately, the implementation of the TSC for non-pulverized wood biomass and possibly for other biomass holds great potential for economically and technically beneficial incineration and power generation.

The main goal of this work is to obtain semi-analytical solutions for the geometric optimization of fins considering the presence of a primary surface. Optimized fin dimensions devoted to finned surfaces are already available in the literature; however, these solutions have as assumption a known fin base temperature. In contrast, in many practical situations, employed fins are attached to a primary surface that has restricted dimensions due to design requirements. In these cases, the primary surface dimensions are kept fixed and the known condition is a temperature or convective condition prescribed on the primary surface boundary. For such scenarios, to the best of our knowledge, there are no simple analytical expressions derived in the literature. Thus, reasoning on this main problem, in the present work, analytical optimum expressions are derived in order to deal with this kind of applications. The obtained analytical equations are subsequently compared with optimum results acquired from numerical calculations. In summary, both analytical and numerical results show a good agreement. The main contribution of this work is to provide closed solutions for the mentioned optimization problem, thus allowing the construction of simple charts, facilitating the corresponding fin design process.

An entropy analysis and design optimization methodology is combined with airfoil shape optimization to demonstrate the impact of entropy generation on aerodynamics designs. In the work herein, the entropy generation rate is presented as an extra design objective along with lift-drag ratio, while the lift coefficient is the constraint. Model equation, which calculates the local entropy generation rate in turbulent flows, is derived by extending the Reynolds-averaging of entropy balance equation. The class-shape function transform (CST) parametric method is used to model the airfoil configuration and combine the radial basis functions (RBFs) based mesh deformation technique with flow solver to compute the quantities such as lift-drag ratio and entropy generation at the design condition. From the multi-objective solutions which represent the best trade-offs between the design objectives, one can select a set of airfoil shapes with a low relative energy cost and with improved aerodynamic performance. It can be concluded that the methodology of entropy generation analysis is an effective tool in the aerodynamic optimization design of airfoil shape with the capability of determining the amount of energy cost.

Design optimization of a three-dimensional (3D) heat flow structure for power electronics gate drive circuit thermal management is described. Optimization methods are described in the creation of several structural concepts targeted toward simultaneous temperature reduction of multiple gate drive integrated circuit (IC) devices. Each heat flow path concept is intended for seamless integration based on power electronics packaging space constraints, while maintaining required electrical isolation. The design synthesis and fabrication of a select concept prototype is presented along with the development of an experimental test bench for thermal performance characterization. Experimental results indicate a significant 45 ∘C maximum temperature reduction for the gate drive IC devices in a laboratory environment, which translates to an estimated 41 °C maximum temperature reduction under high temperature (∼100 °C) ambient conditions. The technical approach and design strategy are applicable to future wide band-gap (WBG) electronics packaging applications, where enhanced 3D thermal routing is expected to be critical to maximizing volumetric power density.

The vortex tube is a mechanical device with no moving parts that can separate a compressed gas into a hot and a cold stream. Pressurized gas is injected tangentially into a swirl chamber and accelerated to a high rate of rotation. This gas motion creates a cold core and a hot shell. In certain engineering applications such as gas drilling, the use of a high flow-rate air with high pressure and low temperature can improve process efficiency. In these applications, demand for the cold air stream as high as 40 kg/s is not uncommon. In this paper, the use of a vortex tube bundle for generating this large flow-rate of the cold air stream is proposed and evaluated, using numerical simulations. A single commercially available vortex tube can only produce a cold air stream up to 0.008 kg/s. Thus, it will take 5000 such vortex tubes to reach the required flow rate of 40 kg/s. Space limitation, as well as assembly difficulty, makes such an approach unrealistic. The objective of this work is to design a custom-made vortex tube so that a minimum number of such tubes can be used to meet the performance requirement posted by these applications. In this study, computational fluid dynamics (CFD) is used to analyze the flow field, temperature field, and pressure field, and to optimize the vortex tube parameters so that a specific set of desired output can be achieved to meet the application requirements.

Vortex generators (VG) are widely used in multifunctional heat exchangers/reactors for augmenting the heat transfer from fin plates to the working fluid. In this study, numerical simulations for longitudinal VGs are performed for both laminar and turbulent flow regimes. The shear-stress transport (SST) κ – ω model is used for modeling turbulence. Inclination angle for a new streamlined VG configuration called inclined projected winglet pair (IPWP) was varied to study the effect of this angle on the heat transfer enhancement and pressure drop. Response surface methodology (RSM) was used to deduce the inclination angle effects on heat transfer, pressure drop, and vorticity from both local and global points of view. Such study highlights the optimization for this VG configuration for better heat transfer intensification, based on thermal enhancement factor (TEF). Finally, it is found that the VG with inclination angle ranging from 30 deg to 35 deg exhibits the best global performance compared to other inclination angles. This type of studies is important for the enhancement of the thermal performance of heat exchangers and static mixers in various engineering applications.

Low grade waste heat recovery presents an opportunity to utilize typically wasted energy to reduce overall energy consumption and improve system efficiencies. In this work, the technoeconomic performance of a turbocompression cooling system (TCCS) driven by low grade waste heat in the engine coolant of a large marine diesel generator set is investigated. Five different working fluids were examined to better understand the effects of fluid characteristics on system performance: R134a, R245fa, R1234ze(E), R152a, and R600a. A coupled thermodynamic, heat exchanger, and economic simulation was developed to calculate the simple payback period of the waste heat recovery system, which was minimized using a search and find optimization routine with heat exchanger effectiveness as the optimization parameter. A sensitivity study was performed to understand which heat exchanger effectiveness had the largest impact on payback period. Of the five working fluids examined, a TCCS with R152a as the working fluid had the lowest payback period of 1.46 years with an initial investment of $181,846. The R152a system was most sensitive to the two-phase region of the power cycle condenser. The R1234ze(E) system provided the largest return on investment over a ten year lifetime of $1,399,666.

In the present study, the numerical investigation has been performed for a phase change material (PCM)-based longitudinal fin heat sink. The fins are taken as an integral part of the heat sink and are made up of aluminum. The PCM considered in the study is RT44HC. Heat is transferred to the heat sink through its horizontal base. In order to simulate the melting behavior of the PCM, volume of fluid model has been used. To attain the best configuration with optimum operational time, Taguchi method has been used followed by analysis of melt fraction and maximum base temperature. The optimized heat sink configuration with maximum operational time has been obtained at the critical temperatures of 54.8 °C, 63 °C, and 72.6 °C.

A design method for the thermoelectric cooling system is improved in this work based on a graphical approach. It is used to select an appropriate thermoelectric cooler (TEC) and determine the value of optimum input current. Theoretical analysis has been conducted to investigate the cooling performance of the system using the design method. Numerical simulation and experimental tests for the entire cooling system validate the calculation result, which indicates the high reliability of the theoretical design method. The temperature dependence of the heat sink resistance and the contact resistance are the major reasons for the small discrepancy. Research is then conducted based on the design method to investigate how a thermoelectric cooling system under natural convection performs, where the optimization of heat sinks at hot side of TEC is done by using the generalized correlations in the previous studies. Comparison is made between the thermoelectric cooling system and the bare-heat-sink system under natural convection. Results show that the thermal resistance of the heat sink attached to TEC is critical to the cooling performance of the whole system. Besides, TEC under natural convection can perform better than the passive cooling if the heat load is not very high ( q c ″ ≤ 20 , 000 W / m 2 ). The design process and results can provide a useful guidance for other thermal engineers.

This paper explores the use of a self-adaptive multipopulation elitist (SAMPE) Jaya algorithm for the economic optimization of shell-and-tube heat exchanger (STHE) design. Three different optimization problems of STHE are considered in this work. The same problems were earlier attempted by other researchers using genetic algorithm (GA), particle swarm optimization (PSO) algorithm, biogeography-based optimization (BBO), imperialist competitive algorithm (ICA), artificial bee colony (ABC), cuckoo-search algorithm (CSA), intelligence-tuned harmony search (ITHS), and cohort intelligence (CI) algorithm. The Jaya algorithm is a newly developed algorithm and it does not have any algorithmic-specific parameters to be tuned except the common control parameters of number of iterations and population size. The search mechanism of the Jaya algorithm is upgraded in this paper by using the multipopulation search scheme with the elitism. The SAMPE-Jaya algorithm is proposed in this paper to optimize the setup cost and operational cost of STHEs simultaneously. The performance of the proposed SAPME-Jaya algorithm is tested on four well-known constrained, ten unconstrained standard benchmark problems, and three STHE design optimization problems. The results of computational experiments proved the superiority of the proposed method over the latest reported methods used for the optimization of the same problems.

Heat transfer is a naturally occurring phenomenon and its augmentation is a vital research topic for many years. Although, vortex generators (VGs) are widely used to enhance the heat transfer of plate-fin type heat exchangers, few researches deal with its thermal optimization. This work is dedicated to the numerical investigation and optimization of VGs configuration in a plate-fin channel. Three-dimensional (3D) numerical simulations are performed to study the effect of angle of attack and attach angle (angle between VG and wall) and shape of VG on the fluid flow and heat transfer characteristics. The flow is assumed as steady-state, incompressible, and laminar within the range of studied Reynolds numbers (Re = 380–1140). Results are presented in the form average and local Nusselt number and friction factor. The effect of attach angle is highlighted and the results show that the attach angle of 90 deg may not be necessary for enhancing the heat transfer. The flow structure and heat transfer characteristics of certain cases are examined in detail. The parameters of VG are then optimized for maximum heat transfer and minimum pressure drop. The three independent design parameters are considered for the two objective functions. For this purpose, computation fluid dynamics (CFD) data, response surface methodology (RSM) and a multi-objective optimization algorithm (MOA) are combined. The data obtained from numerical simulations are used to train a Bayesian-regularized artificial neural network (BRANN). This in turn is used to drive a MOA to find the optimal parameters of VGs in the form of Pareto front. The optimal values of these parameters are finally presented.

This paper discusses the approach of cooling design optimization of a high-pressure turbine (HPT) endwall with applied 3D conjugate heat transfer (CHT) computational fluid dynamics (CFD). This study involved the optimization of the spacing of impingement jet array and the exit width of shaped holes, which are different for each cooling cavity. The optimization objectives were to reduce the wall-temperature level and to increase the aerodynamic performance. The optimization methodology consisted of an in-house parametric design and CFD mesh generation tool, a CHT CFD solver, a database of CFD results, a metamodel, and an algorithm for multi-objective optimization. The CFD tool was validated against experimental data of an endwall at CHT conditions. The metamodel, which could efficiently estimate the optimization objectives of new individuals without CFD runs, was developed and coupled with nondominated sorting genetic algorithm II (NSGA II) to accelerate the optimization process. Through the optimization search, the Pareto front of the problem was found in each iteration. The accuracy of metamodel with more iterations was improved by enriching database. But optimal designs found by the last iteration are almost identical with those of the first iteration. Through analyzing extra CFD results, it was demonstrated that the design variables in the Pareto front successfully reached the optimal values. The optimal pitches of impingement arrays could be decided accommodating the local thermal load while avoiding jet lift-off of film coolant. It was also suggested that cylindrical film holes near throat should be beneficial to both aerodynamic and cooling performances.

One important safety issue in automotive industry is the efficient cooling of brake system. This research work aims to introduce an optimized cooling vane geometry to enhance heat removal performance of ventilated brake disks. The novel idea of using airfoil vanes is followed as the basis of this investigation (Nejat et al., 2011, “Heat Transfer Enhancement in Ventilated Brake Disk Using Double Airfoil Vanes,” ASME J. Therm. Sci. Eng. Appl., 3(4), p. 045001). In order to perform the optimization technique efficiently, an integrated shape optimization process is designed. According to the aerodynamic and heat transfer considerations, first an appropriate airfoil is selected as the base profile to be optimized. For the shape modification purpose, a curve parameterization method named class shape transformation (CST) is utilized. The control parameters defined in CST method are then established as the geometrical design variables of an improved territorial particle swarm optimization (TPSO) algorithm. In order to overcome the potential bottleneck of high computational cost associated with the required computational fluid dynamics (CFD)-based function evaluations, TPSO algorithm is coupled with a predictive artificial neural networks (ANN), well trained with an input dataset designed based on the Taguchi method. The obtained profile shows an evident convective heat dissipation improvement accomplished mainly via airflow acceleration over the vanes, avoiding early flow detachment and adjusting the flow separation region at the rear part of the suction sides. The results also reveal the approaches by which such a superior performance is achieved by means of the modified surface curvatures.