Exergy and sensibility analysis of each individual effect in a kraft multiple effect evaporator

The multiple effect evaporator (MEE) is an energy intensive step in the kraft pulping process. The exergetic analysis can be useful for locating irreversibilities in the process and pointing out which equipment is less efficient, and it could also be the object of optimization studies. In the present work, each evaporator of a real kraft system has been individually described using mass balance and thermodynamics principles (the first and the second laws). Real data from a kraft MEE were collected from a Brazilian plant and were used for the estimation of heat transfer coefficients in a nonlinear optimization problem, as well as for the validation of the model. An exergetic analysis was made for each effect individually, which resulted in effects 1A and 1B being the least efficient, and therefore having the greatest potential for improvement. A sensibility analysis was also performed, showing that steam temperature and liquor input flow rate are sensible parameters.

Download Full-text

Endoreversible Modeling of a Hydraulic Recuperation System

Entropy ◽

10.3390/e22040383 ◽

2020 ◽

Vol 22 (4) ◽

pp. 383 ◽

Cited By ~ 8

Author(s):

Robin Masser ◽

Karl Heinz Hoffmann

Keyword(s):

Heat Transfer ◽

Energy Saving ◽

Energy Savings ◽

Dynamical Behavior ◽

Real Data ◽

Pipe Diameter ◽

Transfer Coefficients ◽

Hydraulic Unit ◽

Energy Saving Potential ◽

Heat Transfer Coefficients

Hybrid drive systems able to recover and reuse braking energy of the vehicle can reduce fuel consumption, air pollution and operating costs. Among them, hydraulic recuperation systems are particularly suitable for commercial vehicles, especially if they are already equipped with a hydraulic system. Thus far, the investigation of such systems has been limited to individual components or optimizing their control. In this paper, we focus on thermodynamic effects and their impact on the overall systems energy saving potential using endoreversible thermodynamics as the ideal framework for modeling. The dynamical behavior of the hydraulic recuperation system as well as energy savings are estimated using real data of a vehicle suitable for application. Here, energy savings accelerating the vehicle around 10% and a reduction in energy transferred to the conventional disc brakes around 58% are predicted. We further vary certain design and loss parameters—such as accumulator volume, displacement of the hydraulic unit, heat transfer coefficients or pipe diameter—and discuss their influence on the energy saving potential of the system. It turns out that heat transfer coefficients and pipe diameter are of less importance than accumulator volume and displacement of the hydraulic unit.

Download Full-text

Development of a chemical simplex of deposit formationon the walls of the fuel supply channels of engines and power plants

Engineering Journal Science and Innovation ◽

10.18698/2308-6033-2021-9-2110 ◽

2021 ◽

Author(s):

K.V. Altunin

Keyword(s):

Heat Transfer ◽

Power Plants ◽

Real Data ◽

Similarity Criteria ◽

Theoretical Research ◽

Transfer Coefficients ◽

Fuel Supply ◽

Heat Transfer Coefficients ◽

Mass Fractions ◽

Number Of Cycles

The article describes a theoretical research related to development of a new simplex of deposit formation. This simplex differs from the existing similarity criteria and heat transfer simplices in that it is chemical and consists of the mass fractions of some fuel components, a metal wall and deposits. The problem of the formation of carbon-containing deposits on the heated walls of the fuel supply channels of power plants and engines is considered in detail. The main conditions for the occurrence of carbon-containing deposit and its properties, as well as its dependence on many factors, including temperature, number of cycles, the presence of additives in fuel, etc., are shown. For some thermophysical properties of deposits in different engines real data are given, as well as data on metals-catalysts and metals-inhibitors of oxidation and sedimentation. The obtained chemical simplex can be successfully used when creating new heat transfer criterion equations that would be much more accurate and applied for the following determination of heat transfer coefficients in fuel supply channels of engines and power plants.

Download Full-text