Phi Drive had to perform some flow analysis on a heat exchanger.

The heat exchanger is made of the following items:

• a fan on the top;
• three finned bodies;
• the main fluid.

Air rises from the bottom and passes through two finned bodies in which water is sprayed to increase humidity. Then, water passes through the latter finned body, which is crossed by various pipes in which flow the water that has to be cooled down.

Thanks to the Computational Fluid Dynamics (CFD) analysis we were able to appreciate some important fluid characteristics. It is possible to see the pressure drop of air passing through the three finned bodies and the pressure recovery due to the suction blower. It is possible also to notice how air passes preferentially on the upper side of the intake finned surface and that the intake duct of the fan has a restriction too excessive as pressure is lost on the edge.

For solve this problem, a convergent duct should be implemented.

### HOW TO SOLVE A THERMO-FLUID DYNAMIC PROBLEM

For the solution of this problem correlation are not sufficient as the flow pattern is too complex. For this reason, Phi Drive has face the problem using CFD. As a matter of facts, Navier-Stokes equations that govern fluids are very complex equation that cannot be solved analytically. In fact, they only are suitable for a restricted spectrum of flows and geometries. As a consequence, in the last decades, together with processors development, CFD has spread out.

The partnership with Comestero Sistemi, leader in ventilation systems, allowed Phi Drive to refine its methodology about fluid dynamic calculus and to decline it in other areas such as refrigeration, valves and turbo machines.

Computational Fluid Dynamics is based on Finite Volume method. The domain is divided in small volumes connected one with each other. In each of these volumes the numerical equation are solved  by means of iterative numerical methods. Once the solution is attained, the user can check any parameter of interest on the domain.

CFD is a powerful tool that allows to reach good results in a relative little amount of time. It is complementary to experimental method and therefore it reduces costs to create prototypes. However, in order to get reasonable results, CFD simulations have always to be run by an expert analyst.

The human factor, to a greater extent than software, can make the difference between great quality and non-quality CFD.

### CFD APPLICATION FIELDS

CFD is widely used in specific solutions:

• Fan and ventilation systems;
• Heat exchanger;
• Valves design;
• Support to fluid dynamics laboratory activities;
• Optimization of thermo-fluid dynamics systems;
• Turbo machines design;
• Two-phase fluid systems.

However, each of these activities requires knowledge and competence. If used correctly and by competent people, the CFD can be an excellent tool for the innovation of fluid dynamics systems.

The high success rate of Phi Drive is to be found in the first place in the ability to physically model the problem together with the use of cutting-edge calculation software.

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