Heat integration techniques are now widely used for energy saving in petroleum processes. In this paper, an industrial hydrocracking process (UOP license) is retrofitted by pinch analysis as a significant tool for heat integration. The hydrocracking process is a main important conversion process in oil refineries and there has been sustained effort to improve its energy efficiency. Application of pinch analysis in retrofit of this process shows the heat exchanger network is operated efficiently. However, a large amount of energy is wasted from the hydrocracking unit, which their condition make no of use directly by the process during pinch analysis. Actually, most of the refining petroleum processes use considerably more energy than the operational minimum energy requirements because of their energy losses. These external energy losses are due to many factors, including normally inefficient or outdated equipment and process design, inadequate heat recovery, and poor integration of heat sources and sinks. However, without identifying the quality of the energy losses, it is difficult to determine how much of that energy is feasible to recover under realistic plant operating conditions. This is where exergy analysis can significantly assist in determining energy recovery opportunities. Thus, this paper is addressed to researchers who are assessing the quality of energy wasted in hydrocracking process, by using the principles of both pinch and exergy analysis. Based on the result obtained, the flue gas exhaust and the high pressure drop in reaction section can be considered as the exergy loss sources in this process. Moreover, the portion of waste energy that can be practically recovered is quantified.

Inaccurate prediction of the required pressures can lead to a number of costly drilling problems. In this study, the hydrodynamics of mud-cuttings were numerically studied using the Mixture Model. To this end, an in-house code was developed to calculate the velocity and pressure fields. The mud velocity profile using of Herschel–Bulkley model and solid phase volume fraction were locally calculated; moreover, pressure drop through the annulus was taken into account. The effects of velocity, mud properties, and solid phase volume fraction on pressure drop were discussed and a new correlation was proposed for calculating friction factor based on corresponding parameters.

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Purpose Due to the extensive industrial applications of stagnation flow problems, the present work aims to investigate the magnetohydrodynamics (MHD) flow and heat transfer of a magnetite nanofluid (here Fe3O4–water nanofluid) impinging a flat porous plate under the effects of a non-uniform magnetic field and chemical reaction with variable reaction rate. Design/methodology/approach Similarity transformations are applied to reduce the governing partial differential equations with boundary conditions into a system of ordinary differential equations over a semi-infinite domain. The modified fourth-order Runge–Kutta method with the shooting technique which is developed for unbounded domains is conducted to give approximate solutions of the problem, which are then verified by results of other researchers, showing very good agreements. Findings The effects of the volume fraction of nanoparticles, permeability, magnetic field, chemical reaction and Schmidt number on velocity, temperature and concentration fields are examined and graphically illustrated. It was found that fluid velocity and temperature fields are affected strongly by the types of nanoparticles. Moreover, magnetic field and radiation have strong effects on velocity and temperature fields, fluid velocity increases and thickness of the velocity boundary layer decreases as magnetic parameter M increases. The results also showed that the thickness of the concentration boundary layer decreases with an increase in the Schmidt number, as well as an increase in the chemical reaction coefficient. Research limitations/implications The thermophysical properties of the magnetite nanofluid (Fe3O4–water nanofluid) in different conditions should be checked. Practical implications Stagnation flow of viscous fluid is important due to its vast industrial applications, such as the flows over the tips of rockets, aircrafts, submarines and oil ships. Moreover, nanofluid, a liquid containing a dispersion of sub-micronic solid particles (nanoparticles) with typical length of the order of 1-50 nm, showed abnormal convective heat transfer enhancement, which is remarkable. Originality/value The major novelty of the present work corresponds to utilization of a magnetite nanofluid (Fe3O4–water nanofluid) in a stagnation flow influenced by chemical reaction and magnetic field. It should be noted that in addition to a variable chemical reaction, the permeability is non-uniform, while the imposed magnetic field also varies along the sheet. These, all, make the present work rather original.