A FIELD SYNERGY PRINCIPLE OF VELOCITY AND PRESSURE FOR FLOW RESISTANCE REDUCTION

Both the heat transfer and the flow resistance are important for the design of heat transfer enhance- ment techniques. The field synergy principle of velocity and temperature has been widely used in the optimization of convective heat transfer processes, but the field synergy principle for flow resistance is still lacking. In this work, a field synergy principle between velocity and pressure is derived for the flow resistance. The derivation of the principle is based on the divergence theorem. The differential equations are used to clarify the physical meaning of the principle. The analysis demonstrates that the negative of the integral of the product of velocity and total pressure gradient equals the pumping power of the flow. Therefore, the principle states that the better the synergy of velocity and total pres- sure fields, which means smaller intersection angle between velocity and total pressure gradient, the lower the pumping power consumed. The static pressure can also be used in the principle when the change of the flow rate of dynamic pressure is insignificant. Numerical examples are used to validate the principle. This study indicates that the synergy among velocity, temperature, and pressure fields is important for the design of high-efficiency heat transfer enhancement techniques.