An approach for the optimum design of heat exchangers

Abstract

SUMMARYIn this paper, an approach for the optimum design of heat exchangers has been presented. Traditional design method of heat exchangers involves many trials in order to meet design specifications. This can be avoided through the present design method, which takes the minimization of annual total cost as a design objective. In alternative optimum design methods, such as Lagrange multiplier method, by changing one variable at a time and using a trial-error or a graphical method, optimum results are obtained in a long time. In the present design optimization problem, the total annual cost has been taken as the objective function and heat balance, and rate equation have been taken as equal constraint. The method using the penalty function transforms the constrained problem into a single unconstrained problem. To solve the optimal problem, the method of steepest descent has been used. Initial design variables include the tubeinside coefficient of heat transfer, tube-outside coefficient of heat transfer, temperature difference and outside tube area of heat transfer. The changes in variables are considered simultaneously to reach an optimum solution. The results show that the present approach is a powerful tool for optimum design of heat exchangers and is expected to be beneficial to energy industry.

Joint economic optimization of heat exchanger design and maintenance policy

“…According to Ludwig [52], in case of asymptotic fouling, the fouling resistance can be obtained integrating equation (2) Sand deposit from water at constant heat flux (6) In equation (3) parameter β, which is representative of the instantaneous fouling rate, is usually experimentally determined. In fact, it depends fom all the factors influencing the fouling process and is hard to estimate analytically.…”

“…In case of the optimal "joint optimization" exchanger a total of 5 cleaning operations are performed during the life cycle of 40000 h and the optimal maintenance interval is about 6956 hours, i.e about once per year. The resulting trend of the overall heat transfer coefficients and the corresponding maintenance schedules are shown in Figures 5,6,7 for the "Joint Optimization" exchanger as well as the TGA2, and the "hybrid TGA" designs for sake of comparison. Table 5 shows the influence of fouling rate obtained by changing the value of parameter k in Equation (7).…”

“…Recent examples of design optimization methods are the works of Khalifeh Soltan et al [5], Unuvar and Kargici [6], Selbas et al [7], Sena-Gonzalez et al [8], Ponce-Ortega et al [9], Costa and Queiroz [10], and the optimization techniques utilized nowadays in heat exchangers optimization are frequently of genetic nature [7,11,12,13]. Although some scholars are skeptical about the use of precise optimization methods when applied to heat exchanger design, owing to the inherent fuzziness of the problem given the uncertainty in operating conditions and in the adopted design correlations [14], computer based optimization of heat exchanger design is an established and widely accepted research subject.…”

Optimal Design of Tube Banks in Crossflow Using Entropy Generation Minimization Method

“…Entropy generation rate is generally used in a dimensionless form. Unuvarn and Kargici [14] and Peters and Timmerhaus [15] presented an approach for the optimum design of heat exchangers. They used the method of steepest descent for the minimization of annual total cost.…”

Computational Fluid Dynamics and Heat Transfer Analysis for a Novel Heat Exchanger

“…The question here is, can the tubes in shell be oriented such that the heat transfer between the two fluids is enhanced, while the pressure drop across the heat exchanger is still reasonable. Tube arrangement optimization in shell-tube heat exchangers has been studied extensively by employing various methods [7][8][9][10][11][12][13]. These investigators have shown that the spacing, orientation, and the arrangement of tubes in the shell have profound influence on the thermal performance.…”