Cost Of Heat Exchanger Networks Research Articles

Pinch-Based General Targeting Method for Predicting the Optimal Capital Cost of Heat Exchanger Network

Pinch analysis is vital in optimizing heat exchanger networks (HENs). Targeting methods are used when determining cost effectiveness with pinch analysis. However, the existing targeting methods for the capital cost of HEN are not suitable for wide application scenarios. Therefore, we developed a high-accuracy general capital-cost-targeting method. It is built on a final structure that was evolved from the spaghetti structure of HEN through four loop elimination stages. This structure helps to reduce the prediction deviation of the method. To achieve high adaptability while establishing this method, we considered the different heat exchanger cost categories, different cost laws for one stream pair, and area limitations of heat exchangers that may be encountered in practice. In addition, allowing streams to use individual temperature difference contributions enhances the method’s predictive capacity. The potential defects of the method found in numerical experiments and case studies were corrected with improvement measures. As a result, the accuracy and stability of the targeting method were further enhanced, with absolute target deviations generally within 10% and often within 5%. This study provides a benchmark for the optimal capital cost of HEN, allowing for a better economic effect when applying pinch analysis.

Optimal design of heat exchanger network considering the fouling throughout the operating cycle

A model is established for minimizing the cost of heat exchanger network (HEN) throughout the operating cycle, with fouling, heat exchanger area margin, the location and opening of bypass considered. The Genetic Algorithm (GA) is applied to generate the economically potential structures; the neural network is used to predict the relationship of heat exchange area and cost. The flow velocity and bypass opening are optimized simultaneously by the Sequential Quadratic Programming (SQP) method. The optimization of HEN throughout the operating cycle is a mixed-integer nonlinear problem and is solved by the stage-wise solution procedure. The proposed method can efficiently optimize the design and operation of a HEN throughout the operating cycle. For the studied case, the total cost can be reduced by 62% after the optimization.

Stochastic optimization-based approach for simultaneous process design and HEN synthesis of tightly-coupled RO-ORC-HI systems under seasonal uncertainty

The use of waste heat powered wastewater desalination by coupling an organic Rankine cycle (ORC) with reverse osmosis (RO) has been recognized as a promising solution to desalination. Herein, a tightly-coupled system that allows for optimally customizing the RO-ORC to a background process via heat integration (HI) is developed to minimize the expected desalination cost, while accounting for the seasonal wastewater variability. Moreover, the developed RO-ORC-HI system can improve the membrane permeability by preheating the feed wastewater. To achieve these goals, a stochastic optimization-based solution strategy is proposed by sequentially considering (1) a Pinch-based Duran-Grossman model embedded with uncertainty realization for performing optimal HI during process optimization; (2) a flexible multi-scenario heat exchanger network (HEN) synthesis model that minimizes the total annualized cost of HEN based on a customized stage-wise superstructure. Finally, the behaviors of the proposed system and solution strategy are illustrated through its comparison with a deterministic solution.

Plate-fin heat exchanger network modeling, design and optimization – a novel and comprehensive algorithm

PurposeThe purpose of this paper is to present a novel and applied method for optimum designing of plate-finned heat exchanger network. Considering the total annual cost as the objective function, a network of plate-finned heat exchanger is designed and optimized.Design/methodology/approachAccurate evaluation of plate-finned heat exchanger networks depends on different fin types with 10 different geometrical parameters of heat exchangers. In this study, fin numbers are considered as the main decision variables and geometrical parameters of fins are considered as the secondary decision variables. The algorithm applies heat transfer and pressure drop coefficients correction method and differential evolution (DE) algorithm to obtain the optimum results. In this paper, optimization and minimization of the total annual cost of heat exchanger network is considered as the objective function.FindingsIn this study, a novel and applied method for optimum designing of plate-finned heat exchanger network is presented. The comprehensive algorithm is applied into a case study and the results are obtained for both counter-flow and cross-flow plate-finned heat exchangers. The total annual cost and total area of the network with counter-flow heat exchangers were 12.5% and 23.27%, respectively, smaller than the corresponding values of the network with cross-flow heat exchanger.Originality/valueIn this paper, a reliable method is used to design, optimize parameters and the economic optimization of heat exchanger network. Taking into account the importance of plate-finned heat exchangers in industrial applications and the complexity in their geometry, the DE methodology is adopted to obtain an optimal geometric configuration. The total annual cost is chosen as the objective function. Applying this technique to a case study illustrates its capability to accurate design plate-finned heat exchangers to improve the objective function of the heat exchanger network from the economic viewpoint with the design of details.

Economic optimization of heat exchanger networks based on geometric parameters using hybrid genetic-particle swarm algorithm technique

PurposeThe purpose of this study is to provide a method for designing the shell and tube heat exchangers and examine the total annual cost of heat exchanger networks from the economic view based on the careful design of equipment.Design/methodology/approachAccurate evaluation of heat exchanger networks performance depends on detailed models of heat exchangers design. The simulations variables include nine design variables such as flow direction determination of each of the two fluids, number of tubes, number of tube passes, length of tubes, the arrangement of tubes, size and percentage of baffle cut, tube diameter and tube pitch. The optimal designing of the heat exchangers is based on geometrical and hydraulic modeling and using a hybrid genetic particle swarm optimization algorithm (PSO-GA) technique. In this paper, optimization and minimization of the total annual cost of heat exchanger networks are considered as the objective function.FindingsIn this study, a fast and reliable method is used to simulate, optimize design parameters and evaluate heat transfer enhancement. PSO-GA algorithms have been used to minimize the total annual cost, which includes investment costs of heat exchangers and pumps, operating costs (pumping) and energy costs for utilities. Three case studies of four, six and nine streams are selected to demonstrate the accuracy of the method. Reductions of 0.55%, 23.5% and 14.78% are obtained in total annual cost for the selected streams, respectively.Originality/valueIn the present study, a reliable method is used to simulate and optimize design parameters and the economic optimization of the heat exchanger networks. Taking into account the importance of shell and tube heat exchangers in industrial applications and the complexity in their geometry, the PSO-GA methodology is adopted to obtain an optimal geometric configuration. The total annual cost is chosen as the objective function. Applying this technique to case studies demonstrates its ability to accurately design heat exchangers to optimize the objective function of the heat exchanger networks by giving the detail of design.

Cost Reduction of Fluid Catalytic Cracking Unit in Kaduna Refining and Petrochemical Company using Pinch Technology

Pinch technology is one of the most powerful methodologies of process integration that allows industries to increase their profitability through reductions in energy, water and raw materials consumption. In this study, reduction in the total annual cost of heat exchanger network (HEN) of Fluid Catalytic Cracking (FCC) unit in Kaduna Refining and Petrochemical Company (KRPC), Kaduna was determined. With the help of pinch technology, the reduction was achieved by first determining optimum minimum temperature difference by trading off energy cost and capital cost targets as a function of minimum temperature difference. Thereafter, the total annual cost obtained at the optimum minimum temperature difference was compared with total annual cost of existing design. The results of the analysis showed that the optimum minimum temperature difference was 12℃, the total annual costs of the existing design and the optimum-minimum-temperature-difference based cost were $8.7 and $7.1 Million respectively. This amounted to percentage reduction in the total annual cost of 18.4% which means that about $1.6 Million would been saved annually using the optimum minimum temperature difference to design the HEN of the FCC unit.
 Keywords: Pinch technology, FCC unit, Cost targeting, Area targeting, Trade-off

Optimal heat exchanger network synthesis with detailed shell and tube heat exchanger design based on superstructure model

The shell and tube heat exchanger (SHE) is the most common type of heat transfer equipment used in heat exchanger networks (HENs) in the field of chemical process industries. Both counter-current flow and co- current flow may be involved in the shell and tube heat exchangers. To calculate the temperature difference, the correction factor FT is generally used for multi-pass heat exchanger optimization. For synthesis of heat exchanger networks, a lot of researchers use the correction factor FT as a constraint condition, and the HEN with minimum number of shells is optimized by iterative calculation based on a stage-wise superstructure model. However, in these studies the heat transfer temperature difference correction factor FT are used to avoid temperature crossing without considering the optimization of shell and tube number. In this paper, a method of HEN synthesis with the optimization of the number of shells and tubes for each SHE based on superstructure model is presented. Firstly, the heat transfer process of counter-current and co-current flow in SHE is studied. The correction factor of heat transfer temperature difference FT is calculated based on the mechanism of heat transfer process. Then, each tube of heat exchanger instead of a SHE is defined as a single unit and the energy balance function is established for each unit to minimize the total cost of HEN in the proposed superstructure model of HEN. By using the methodology of mixed integer nonlinear program (MINLP), the HEN synthesis and the correction factor of heat transfer temperature difference FT are optimized simultaneously. The proposed methodology allows for proper handling of the trade-offs involving energy consumption, number of units, number of shells and tubes, and network area to provide a network with the minimum total annual cost. Finally, the case study results demonstrate the effectiveness of this proposed method, and the total cost of HEN are lowered as well as the number of tubes and shells for each SHE is optimized simultaneously.

A novel Random Walk algorithm with Compulsive Evolution for heat exchanger network synthesis

The heat exchanger network (HEN) synthesis can be characterized as highly combinatorial, nonlinear and nonconvex, contributing to unmanageable computational time and a challenge in identifying the global optimal network design. Stochastic methods are robust and show a powerful global optimizing ability. Based on the common characteristic of different stochastic methods, namely randomness, a novel Random Walk algorithm with Compulsive Evolution (RWCE) is proposed to achieve the best possible total annual cost of heat exchanger network with the relatively simple and feasible evolution strategy. A population of heat exchanger networks is first randomly initialized. Next, the heat load of heat exchanger for each individual is randomly expanded or contracted in order to optimize both the integer and continuous variables simultaneously and to obtain the lowest total annual cost. Besides, when individuals approach to local optima, there is a certain probability for them to compulsively accept the imperfect networks in order to keep the population diversity and ability of global optimization. The presented method is then applied to heat exchanger network synthesis cases from the literature to compare the best results published. RWCE consistently has a lower computed total annual cost compared to previously published results.

Simultaneous design of heat exchanger network for heat integration using hot direct discharges/feeds between process plants

A chemical or petrochemical site is generally made up of several plants that are linked together through process streams. The linking process streams are often cooled down in their source plants, then transferred into storage tanks, and reheated in destination plants. This repeatedly cooling and heating results in low energy-use efficiency and more area installed in heat exchanger network. In this study, we introduce a heat exchanger network superstructure based on stage-wise model for heat integration using hot direct discharges/feeds between plants, and develop a new mixed-integer nonlinear optimization model to simultaneously design heat exchanger network. Unlike conventional HEN design, the model can simultaneously synthesize heat exchanger networks for multiple plants, and be able to address variable supply or target temperatures of process streams. The objective is to minimize total annual cost of heat exchanger networks in source and destination plants. Three examples are used to demonstrate the performance of the proposed model and solution approach. The computational results indicate that the simultaneous design of heat exchanger network for heat integration using hot direct discharges/feeds between plants achieves a significant decrease in total annual cost when compared to the separate design of heat exchanger networks for source and destination plants.

An efficient optimization algorithm for waste Heat Integration using a heat recovery loop between two plants

Heat recovery loop (HRL) is an indirect approach for waste Heat Integration between plants. The mathematical model for HRL design is a complex and nonlinear problem, which results in a non-convex Mixed Integer Nonlinear Programming (MINLP) model. Solving the problem without any strategy is difficult since computational results can easily be trapped in the local optimum solutions. This is mainly due to the reasons that operation cost, capital cost of heat exchanger networks, piping and pumping cost are considered simultaneously. To overcome this limitation, an efficient optimization algorithm is proposed for the complex problem. With application of convex reformulation and piecewise wise relaxation, the problem can be reformulated as a convex MINLP model, in which the objective function is convex and all constraints are linear. The computational efforts are reduced largely and better solutions can be obtained for the HRL design. As this work concentrates on low grade heat recovery, hot water is selected as the intermediate fluid to achieve waste Heat Integration between plants. An industrial case is demonstrated to illustrate the effectiveness of the proposed algorithm.

Two-Level Optimization Algorithm for Heat Exchanger Networks Including Pressure Drop Considerations

A mixed-integer nonlinear programming (MINLP) algorithm to account for the effects of the allowable pressure drops for process streams on the structure and cost of heat exchanger networks is presented. Because MINLP models for large problems typically show significant convergence problems, the synthesis model is decomposed into two levels. For a given energy recovery level, an MINLP model is formulated in an inner loop using assumed values for the film heat-transfer coefficients for each stream. In the outer loop, with the use of the areas provided by the MINLP model and thermal-hydraulic models that relate the exchanger area, pressure drops, and film coefficients, updated values of the film coefficients are calculated for each stream according to the specified values for allowable pressure drops. The algorithm provides a network that makes use of the allowable pressure drops specified for the process streams at the total minimum yearly cost. The algorithm shows excellent convergence properties, can incor...

Pinch locations at heat capacity flow-rate disturbances of streams for minimum utility cost heat exchanger networks

The work deals with heat exchanger network (HEN) targeting under heat capacity flow-rates of streams disturbances. In particular, the aim is to calculate all pinches that can exist in a HEN with utilities of minimum cost when stream heat capacity flow-rates ( CPs) are allowed to change within given ranges. It is assumed that the disturbances are stochastic. The knowledge of pinches at certain as well uncertain data is of great importance in designing HENs. For instance, Pinch Technology is based on pinch phenomenon and its influence on HEN operation and design. In case of parameter disturbances, this is even more important since additional application in HEN’s control (see e.g. [1,2]). It is worthnoting that in case of disturbances, pinches behave in very complex manner as it was shown in [1–5]. A rigorous approach has been developed for calculating all feasible locations of pinches that can occur in minimum utility cost of HENs operating at varying heat capacity flow-rates of process streams. The method is based on recursive solution of mixed-integer linear programming (MILP) optimisation model that requires quite moderate number of binary variables. Examples of method application and analysis of results are presented in the work.

Estimation of the installed cost of heat exchanger networks

Much progress has been made in the development of synthesis methods for heat exchanger networks through the use of targeting procedures. Such advances include the development of pinch technology, the application of mathematical programming techniques and the use of the A ∗ heuristic search procedure based on artificial intelligence by the present authors. Networks of substantially different topologies can be produced by the alternative synthesis procedures, but the methods used for cost estimation typically rely heavily on a simple area exponent calculation. As substantial capital costs are incurred for piping a simplified method is proposed which does allow for piping costs and so may be used to discriminate more accurately between alternative networks. The use of this procedure is illustrated by using some networks from published problems.