Optimal operation of simple refrigeration cycles

Jensen, Jørgen Bauck; Skogestad, Sigurd

doi:10.1016/j.compchemeng.2007.01.008

Cited by 45 publications

(19 citation statements)

References 8 publications

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“…The second strategy consists of the control by means of the temperature approach as it was theoretically proposed in (Pitarch et al, 2017a) and (Jensen and Skogestad, 2007b).…”

Section: Theoretical Analysismentioning

confidence: 99%

“…In (Jensen and Skogestad, 2007b) the temperature approach at the condenser was proposed and statistically studied as a good candidate to control the subcooling. However, the reason of this choice is not analyzed in deep.…”

Section: Optimal Subcooling Control Based On the Temperature Approachmentioning

confidence: 99%

“…For predefined external conditions, the subcooling of the system is controlled mainly by the amount of effective charge circulating thorugh the system as it can be seen in (Fernando et al, 2004) for propane. This type of control has some similarities with the control and optimality of the pressure in the gas cooler for transcritical cycles being an example of this the work done in [7] by the application to CO2 and propane or in (Jensen and Skogestad, 2007b) for CO2 and ammonia. Although there is a vast literature on the thermodynamic analysis of closed refrigeration cycles, few authors discuss the control of the effective charge circulating through the systems.…”

mentioning

confidence: 99%

“…This dependece allows the control based on an equation for a given size of the system. Furthermore, the potential of the temperature approach as a control variable is analyzed in (Jensen and Skogestad, 2007b) and deeply studied in [7], where, from a theoretical point of view, it was found that the optimal subcooling in an infinite area condenser takes place when there are two pinch points at the condenser: one inside (dew point) and another at the condenser outlet (approach) and for finite heat exchangers, a similar value of those leads to nearly-optimal operation conditions. Hence, the control of the system based on the temperature approach appears to be a good methodology even though, up to the knowledge of the authors, it has not been experimentally done yet.…”

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confidence: 99%

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Study of different subcooling control strategies in order to enhance the performance of a heat pump

Hervas-Blasco

Pitarch

Navarro-Peris

et al. 2018

International Journal of Refrigeration

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Hervas-Blasco, E.; Pitarch, M.; Navarro-Peris, E.; Corberán, JM. (2018). Study of different subcooling control strategies in order to enhance the performance of a heat pump. International Journal of Refrigeration. 88:324-336. ABSTRACTThe performance of vapor-compression systems working with subcritical refrigerants varies with the degree of subcooling. There is an optimal subcooling that maximizes efficiency. However, it depends on the operating conditions and the control of the system needs to be adapted. Most of the works available in literature are able to operate in optimal conditions only at the design point or if a system is designed to be able to adapt its subcooling, only complex control algorithms which usually are difficult to set and time-costly, are used. This work focuses on the study of the main variables influencing the optimal subcooling and analyzes two different control methodologies from the theoretical point of view. Based on the theoretical study a final control strategy is selected and tested experimentally. The reliability, stability and robustness of the selected strategy is experimentally demonstrated for a wide set of operating conditions. KEYWORDSHeat pump, natural refrigerant, subcritical refrigerant, optimal subcooling, control HIGHLIGHTS  Subcooling enhances heat pump performance up to an optimal value  Two methodologies to control the optimal subcooling are studied  Optimal subcooling control based on the secondary fluid temperature lift  Optimal subcooling control based on a temperature approach  Stability of the temperature approach control is experimentally proved

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“…The second strategy consists of the control by means of the temperature approach as it was theoretically proposed in (Pitarch et al, 2017a) and (Jensen and Skogestad, 2007b).…”

Section: Theoretical Analysismentioning

confidence: 99%

Section: Optimal Subcooling Control Based On the Temperature Approachmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Study of different subcooling control strategies in order to enhance the performance of a heat pump

Hervas-Blasco

Pitarch

Navarro-Peris

et al. 2018

International Journal of Refrigeration

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“…Khan and Lee implemented a particle-swarm optimization paradigm. Jensen considered a nonlinear objective function to balance capital and operating cost trade-offs.…”

Section: Introductionmentioning

confidence: 99%

Scenario-Free Optimal Design under Uncertainty of the PRICO Natural Gas Liquefaction Process

Tsay

Bâldea

2018

Ind. Eng. Chem. Res.

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Liquefaction accounts for a large portion of the cost of liquefied natural gas (LNG), motivating significant efforts in the simulation and optimization of liquefaction processes. While most optimization studies typically assume a fixed feed stream concentration, the properties of natural gas feeds can vary in time or between different sources. This constitutes a significant exogenous uncertainty, particularly for field or offshore liquefaction facilities with limited feed-blending capabilities. This paper examines the PRICO plant as a representative mixed-refrigerant liquefaction process and presents a design optimization formulation for natural gas liquefaction processes with varying feed composition. We introduce models for the multistream heat exchanger and for the compressor that allow for the size of key equipment to be optimized along with the process operating conditions. Using a recently developed scenario-free framework for optimization under parametric uncertainty, our study provides new insights (including some counterintuitive results) concerning optimal liquefaction equipment sizing for dealing with uncertainty in feed composition.

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Economic Plantwide Control

Skogestad

2012

Plantwide Control

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Most (if not all) available control theories assume that a control structure is given at the outset. They therefore fail to answer some basic questions that a control engineer regularly meets in practice (Foss 1973): "Which variables should be controlled, which variables should be measured, which inputs should be manipulated, and which links should be made between them?" These are the question that plantwide control tries to answer.There are two main approaches to the problem, a mathematically oriented approach (control structure design) and a process oriented approach. Both approaches are reviewed in the paper. Emphasis is put on the selection of controlled variables, and it is shown that the idea of "self-optimizing control" provides a link between steady-state optimization and control.We also provide some definitions of terms used within the area of plantwide control.This paper is an unpublished internal report which was written as part of the European Union CAPE.NET project (working group 5). We welcome any comments you may have.

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Optimal operation of simple refrigeration cycles

Cited by 45 publications

References 8 publications

Study of different subcooling control strategies in order to enhance the performance of a heat pump

Study of different subcooling control strategies in order to enhance the performance of a heat pump

Scenario-Free Optimal Design under Uncertainty of the PRICO Natural Gas Liquefaction Process

Economic Plantwide Control

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