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Abstract: Equation of power consumption in the flow process of micro-fluid elements has been deduced in this paper by analyzing the mechanical energy equilibrium equation of microelement based on the stress relation of Newtonian fluid. By setting minimum power consumption as optimization objective and entransy consumption as constraint condition, optimization flow field equation for convective heat transfer on the basis of energy conservation equation and continuity equation are constructed. Numerical investigations of forced convective heat transfer in a circular tube based on the optimized controlling equations are conducted, and the results show that there are multi-longitude-vortexes existing in velocity field, which leads to an enhancement of heat transfer. The analysis for the heat transfer and flow resistance shows that this kind of flow field accommodates a far greater heat transfer increase than flow resistance increase, which proves that the proposed optimization theory is effective in designing high efficient heat transfer enhancement unit. [Copyright &y& Elsevier]

Abstract: In this paper, linear programming formulations, complemented by concept based pinch analysis results, are developed to target the minimum energy requirements in a heat integrated fixed flow rate water allocation networks. These formulations can be applied for the cases of heat integration through isothermal and non-isothermal mixing in water allocation networks involving single as well as multiple contaminants. The earlier reported approaches are based on linear programming formulation for the case of isothermal mixing and either mixed integer non-linear programming or discontinuous non-linear programming formulations for the case of non-isothermal mixing. It has been observed that the earlier reported methodologies produce sub-optimal results for the case of non-isothermal mixing. However, the proposed methodologies produce the optimum results because of the rigorously proved linear formulation. Utility requirements for isothermal as well as for non-isothermal mixing cases are compared over a range of minimum approach temperatures, to evaluate the energy performance using illustrative examples. [Copyright &y& Elsevier]