The steady-state, viscous flow and heat transfer of nanofluid in the vicinity of an axisymmetric stagnation point of a stationary cylinder with constant wall heat flux is investigated. The impinging free-stream is steady and with a constant strain rate, k ¯. Exact solution of the Navier-Stokes equations and energy equation are derived in this problem. A reduction of these equations is obtained by use of appropriate transformations introduced in this research. The general self-similar solution is obtained when the wall heat flux of the cylinder is constant. All the previous solutions are presented for Reynolds number Re = k ¯a 2 /2n f ranging from 0.1 to 1000, selected values of heat flux and selected values of particle fractions where a is cylinder radius and n f is kinematic viscosity of the base fluid. For all Reynolds numbers, as the particle fraction increases, the depth of diffusion of the fluid velocity field in radial direction, the depth of the diffusion of the fluid velocity field in z-direction, shear-stresses and pressure function decreases. However, the depth of diffusion of the thermal boundary-layer increases. It is clear by adding nanoparticles to the base fluid there is a significant enhancement in Nusselt number and heat transfer.

Exergy rate profiles, exergetic efficiency and irreversibility were used to examine the driving forces in multicomponent distillation system with the view to identifying feasible and efficient operating parameters. The mixture comprised of 5% propane, 15% iso butane, 25% n-butane, 20% iso pentane and 35% n-pentane. Operating variables were feed temperature (-30oC and -80oC), pressure (800KPa and 1200KPa), and reflux-ratio (2 and 6). Sensitivity analysis was carried out to examine the effect of varying operating parameters on the systems. Stage-by-stage system exergy analysis was estimated. Column profiles of a base case -30oC, -80oC, -30oC-reflus ratio 6,80oC -80oC reflux ratio 6 and base case reflux ratio 6 did not cross thus are thermodynamically feasible. Base case -30oC-reflux ratio 2, -80oC-reflux ratio 2, and base case-reflux ratio 2 were crossed and constricted and are infeasible. Base case results gave efficiency of 81.7% at depropanizer and 65.2% at debutanizer. Base cases sensitivity results with -30oC, -80oC and reflux ratio 6, efficiency range 57.40 -70% and 65.20% -54.90% for depropanizer and debutanizer respectively. Spitted cases gave 81.7% and 62.20% with more scatter profiles. Splitted feed base case -30oC design gave the lowest overall system exergy loss rate of 1.12E+6 and efficiency of 95.70%.

In this paper, energy recycling for distillation tower condenser was done by use of heat integration method. At first, we calculated the amount of condensation energy (QAir Cooler), in air cooler, and then we calculated energy consumption in this equipment based on annual balance (5460 GJ per year). Then, based on heat integration (energy unification), two conditions were proposed to use the current energies in the process for supplying condensation energy (QAir Cooler): first, its must be lesser than condensing temperature of condenser (55 ° C) (the major condition). Second, it must have much more flow rate than the overhead flow. According to two above conditions, the food flow as chosen as the integration factor and its amount of energy (EStream) is calculated from the Enthalpy equation as 9863964 kj/h. As EFeed >>> QAir Cooler and food flow temperature to condense an overhead vapor is satisfying. The food flow can be used to condense the saturated vapor to 55 ° C. in case of using food energy and using heat exchanger instead of air cooler; 5460 GJ energy will be saved annually. By using heat exchanger and omitting air cooler, the unit103 operating costs will be reduced considerably. Economically, conducting such a project will demand investing costs. However, obtainable incomes from doing this project (electricity consumption recycling and cost's reduction) reveal this fact that capital return rate and the project benefits for unit103 of South Pars phases2&3 are beneficial.