Second Law Analysis Optimal Design of a Mixer for Sanitary Water

In this work, entropy generation analysis is used in the search for the optimal design of a mixer for sanitary water. An innovative design of the device is considered: hot water and cold water enter a manifold from five orifices, which opening is controlled by actuators, depending on the requested mass flow rate and average temperature. The design variables are the position of the various orifices, which are modified in order to minimize the mixing length and response time of the device, as well as the global pressure losses. Analysis is conducted using a thermofluid dynamic model which includes continuity, momentum and energy equations, that are solved using a commercial code. Results are then used to calculate the entropy generation distribution, in order to properly consider the various sources of irreversibilities, some of which are necessary (thermal mixing) and some undesired (pressure losses).