| For a heat exchanger design it is always essential to consider the thermodynamic irreversibility or entropy generation rate that takes place inside it. In the following study, the entropy generation rate which has been produced as a result of heat transfer across the fluid-to-fluid temperature difference, including those from frictional pressure drop, are considered. A method is presented based on second law efficiency for the optimization of heat exchangers that would lead to the minimum entropy generation.;The entropy generation minimization was performed numerically with the help of an optimization technique. In the optimization process a constrained optimization technique was utilized. A code was developed in C programming language, so that optimum parameters could be obtained.;The optimum geometry that leads to the minimum entropy generation rate can be found with the help of an optimization procedure. It is the optimum combination of condensing length, inner diameter, as well as, outer diameter for all possible sets of combinations.;As a perfectly adiabatic system was considered and the heat transfer duty was fixed, the entropy generation from heat transfer across the fluid-to-fluid temperature difference remained constant. It is shown that the minimization of entropy generation rate is possible, not only because there exist a trade-off between the heat transfer across the fluid-to-fluid temperature difference, and the pressure drop in both sides of heat exchanger, but also because there is a minimum in the entropy generation rate because of fluid frictional pressure drops.;The following analysis makes up for a specific case of a two phase tube-in-tube heat exchanger used as a condenser with water flowing in the outer tube and refrigerant flowing through the inner tube. The following analysis begins with identification of all individual competing irreversibilities in the heat exchanger. An application of heat and momentum transfer correlations is made for the hot and cold sides; a total entropy generation rate equation in terms of relevant parameters is obtained.;The following method will help the engineer obtain the optimal thermodynamic design with a minimum entropy generation rate. |
