Navigation by alphabet

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Hagen-Poiseuille law Hagen-Rubens relation, between electrical and optical constants, Hall Taylor, N S, Halogenated hydrocarbons: Handley and Heggs equation for fixed bed pressure drop, Hankinson and Thomson method, for liquid density: Hardening (precipative) of stainless steels, Hardwick, R, Harris, D, Hausen equation for developing laminar flow, Hays, G F Headers in shell-and-tube heat exchangers, Heads, in heat exchangers: Heat and mass transfer: Heat exchanger design, introduction, Heat exchangers: Heat of vaporisation (see Enthalpy of vaporisation), of pure substances Heat pipes: Heat pumping, relation to heat exchanger network design, Heat storage (see Regenerators and thermal energy storage) entropy generation in, Heat transfer: Heat transfer coefficient: Heat transfer media, Heat transfer salt, Heat transfer regimes: Heat of vaporization, Heated cavity reflectometer, Heating media, for reboilers, Heavy water, physical properties of, Heggs, P J, Helical coils of circular cross section: Helical coils of rectangular cross section, Helical inserts, for enhancement of heat transfer in boiling, Helium: Helmholtz reciprocity principle, in radiative heat transfer, Henry, J A R, Henry-Fauske model, for critical two-phase flow, Henry's law, for partial pressure, Heptadecane: Heptadecene: Heptane: 1-Heptanol: 1-Heptene: Herman, K W, Hermes, C L L, Heterogeneous conveyance in horizontal pipes, Heterogeneous nucleation in boiling, Hewitt, G F Hexachloroethane (Refrigerant 116): Hexacyclopentane, superheated vapor properties, Hexadecane: Hexadecene: 1,5-Hexadiene: Hexagonal cells, in free convection, Hexamethylbenzene: Hexane: Hexanoic acid: 1-Hexanol: 1-Hexene: Hexylbenzene: Hexylcyclohexane: Hexylcyclopentane, Hicks equation, for fixed-bed pressure drop, High pressure closures, ASME VIII code guidance for, High-chrome steels, thermal and mechanical properties, High-finned tubes, correlations for single-phase heat transfer in flow over, Hills, P D Hohlraum cavity, Holdup, in liquid-liquid flow, Holland, guide to national practice for mechanical design of heat exchangers, Homogeneous condensation (fog formation), Homogeneous model: Homogeneous nucleation: Honeycombs: Hopkins, D, Horizontal condensers: Horizontal cylinders: Horizontal layers, of fluid, free convection heat transfer in, Horizontal pipes: Horizontal shell-side evaporator, Horizontal surfaces: Horizontal thermosiphon reboilers: Horizontal tube-side evaporator, Horizontal tubes: Hottel's rule, in absorption of radiation by gases, Hsu criterion, for onset of nucleate boiling, Hybrid cooling towers, Hydraulic conveyance: Hydraulic expansion, of tubes into tube sheets in shell-and-tube heat exchangers, Hydraulic turbine, lost work in,
Assessing lost work in unit operations
Hydraulic resistance, in flow of supercritical fluids, Hydraulically smooth surface, Hydrazine: Hydrocarbons: Hydrodynamic entrance length, in single-phase flow in ducts, Hydrogen: Hydrogen bromide: Hydrogen chloride: Hydrogen cyanide: Hydrogen fluoride: Hydrogen iodide: Hydrogen peroxide: Hydrogen sulfide: Hydrostatic testing of shell-and-tube heat exchangers, Hysteresis:

Index

HEDH
A B C D E F G H
Hagen-Poiseuille law Hagen-Rubens relation, between electrical and optical constants, Hall Taylor, N S, Halogenated hydrocarbons: Handley and Heggs equation for fixed bed pressure drop, Hankinson and Thomson method, for liquid density: Hardening (precipative) of stainless steels, Hardwick, R, Harris, D, Hausen equation for developing laminar flow, Hays, G F Headers in shell-and-tube heat exchangers, Heads, in heat exchangers: Heat and mass transfer: Heat exchanger design, introduction, Heat exchangers: Heat of vaporisation (see Enthalpy of vaporisation), of pure substances Heat pipes: Heat pumping, relation to heat exchanger network design, Heat storage (see Regenerators and thermal energy storage) entropy generation in, Heat transfer: Heat transfer coefficient: Heat transfer media, Heat transfer salt, Heat transfer regimes: Heat of vaporization, Heated cavity reflectometer, Heating media, for reboilers, Heavy water, physical properties of, Heggs, P J, Helical coils of circular cross section: Helical coils of rectangular cross section, Helical inserts, for enhancement of heat transfer in boiling, Helium: Helmholtz reciprocity principle, in radiative heat transfer, Henry, J A R, Henry-Fauske model, for critical two-phase flow, Henry's law, for partial pressure, Heptadecane: Heptadecene: Heptane: 1-Heptanol: 1-Heptene: Herman, K W, Hermes, C L L, Heterogeneous conveyance in horizontal pipes, Heterogeneous nucleation in boiling, Hewitt, G F Hexachloroethane (Refrigerant 116): Hexacyclopentane, superheated vapor properties, Hexadecane: Hexadecene: 1,5-Hexadiene: Hexagonal cells, in free convection, Hexamethylbenzene: Hexane: Hexanoic acid: 1-Hexanol: 1-Hexene: Hexylbenzene: Hexylcyclohexane: Hexylcyclopentane, Hicks equation, for fixed-bed pressure drop, High pressure closures, ASME VIII code guidance for, High-chrome steels, thermal and mechanical properties, High-finned tubes, correlations for single-phase heat transfer in flow over, Hills, P D Hohlraum cavity, Holdup, in liquid-liquid flow, Holland, guide to national practice for mechanical design of heat exchangers, Homogeneous condensation (fog formation), Homogeneous model: Homogeneous nucleation: Honeycombs: Hopkins, D, Horizontal condensers: Horizontal cylinders: Horizontal layers, of fluid, free convection heat transfer in, Horizontal pipes: Horizontal shell-side evaporator, Horizontal surfaces: Horizontal thermosiphon reboilers: Horizontal tube-side evaporator, Horizontal tubes: Hottel's rule, in absorption of radiation by gases, Hsu criterion, for onset of nucleate boiling, Hybrid cooling towers, Hydraulic conveyance: Hydraulic expansion, of tubes into tube sheets in shell-and-tube heat exchangers, Hydraulic turbine, lost work in,
Assessing lost work in unit operations
Hydraulic resistance, in flow of supercritical fluids, Hydraulically smooth surface, Hydrazine: Hydrocarbons: Hydrodynamic entrance length, in single-phase flow in ducts, Hydrogen: Hydrogen bromide: Hydrogen chloride: Hydrogen cyanide: Hydrogen fluoride: Hydrogen iodide: Hydrogen peroxide: Hydrogen sulfide: Hydrostatic testing of shell-and-tube heat exchangers, Hysteresis:
I J K L M N O P Q R S T U V W X Y Z
H Hydraulic turbine, lost work in,
Download the citation in the EndNote formatOpen in a new tab. Download the citation in the RefWorks formatOpen in a new tab. Download the citation in the BibTex formatOpen in a new tab.

Assessing lost work in unit operations

DOI 10.1615/hedhme.a.000134

1.9.5 Assessing lost work in unit operations

D. Limb

A. Overview

A unit operation is a sub-element of a complete process, which is defined by a boundary or envelope circumscribing it. Material and energy may cross this boundary. The exergy entering the unit operation envelope via the feed streams or any work done on it will exceed the exergy leaving the envelope by a certain amount. This is the lost work. As we know, unit operations are hooked together in a chain or network to make a complete process. There is a logical direction for the flow of materials and energy — and therefore of exergy through the process. The final elements (unit operations) from which the products are delivered will require a net exergy input to deliver the products under the correct conditions and purities, and to offset the irreversibilities arising within its envelope. The exergy needed by this “final step” must be provided as external work supply or as an input in the streams entering that unit operation’s envelope from preceding unit operations. It thus becomes evident that the irreversibilities in a final step can have a “knock on” effect on the work which has to be done by preceding steps, which themselves are to some extent irreversible — and so on. There is often a compounding effect as one works backwards (in the sense of exergy flow) through the process. This is sometimes expressed by the statement “irreversibilities breed irreversibilities”. The issue is further developed and formalized by Kotas (1986), using the concept Coefficients of Structural Bonds, or CSB. Basically, this coefficient is the ratio of the change in irreversibility rate for the plant as a whole — to the change in a particular component, when one of the design parameters on that component is varied. This concept is intriguing for those wishing to pursue work in the exergy field, but for the rest, it is probably more of academic than of practical interest.

Exergy flow through a process can sometimes be conveniently depicted on a so-called “Grassmann diagram” see Figure 1. This is a development of the “Sankey” diagram used to show heat flow and losses (First Law).

Figure 1 Grassmann diagram

Recently some workers in the field have used exergy as means to assess the overall lifetime costs of a piece of equipment. This takes account not only of the exergy destroyed during its operation but also of the exergy consumed in manufacturing it from raw materials. See Cornelissen (1995).

... You need a subscriptionOpen in a new tab. to view the full text of the article. If you already have the subscription, please login here

© 2024 by Begell House, Inc.