Dynamic mode decomposition (DMD) represents an effective means for capturing the essential features of numerically or experimentally generated flow fields. In order to achieve a desirable tradeoff between the quality of approximation and the number of modes that are used to approximate the given fields, we develop a sparsity-promoting variant of the standard DMD algorithm. Sparsity is induced by regularizing the least-squares deviation between the matrix of snapshots and the linear combination of DMD modes with an additional term that penalizes the l1-norm of the vector of DMD amplitudes. The globally optimal solution of the resulting regularized convex optimization problem is computed using the alternating direction method of multipliers, an algorithm well-suited for large problems. Several examples of flow fields resulting from numerical simulations and physical experiments are used to illustrate the effectiveness of the developed method.

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Sparsity-promoting dynamic mode decomposition

Analysis of a carbon dioxide transcritical power cycle using a low temperature source

This paper evaluates performance merits of CO2 and R134a automotive air conditioning systems using semi-theoretical cycle models. The R134a system had a current-production configuration,which consisted of a compressor, condenser,expansion device,and evaporator. The CO 2 system was additionally equipped with a liquid-line/suction-line heat exchanger. Using these two systems,an effort was made to derive an equitable comparison of performance; the components in both systems were equivalent and differences in thermodynamic and transport properties were accounted for in the simulations. The analysis showed R134a having a better COP than CO2 with the COP disparity being dependent on compressor speed (system capacity) and ambient temperature. For a compressor speed of 1000 RPM,the COP of CO 2 was lower by 21% at 32.2 � C and by 34% at 48.9 � C. At higher speeds and ambient temperatures,the COP disparity was even greater. The entropy generation calculations indicated that the large entropy generation in the gas cooler was the primary cause for the lower performance of CO2. # 2001 Elsevier Science Ltd and IIR. All rights reserved.

https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=860836

Comparitive analysis of an automotive air conditioning systems operating with CO2 and R134a

Exergoenvironmental analysis of a steam methane reforming process for hydrogen production

Depleting energy resources have become the driving force for their conservation. Increasing the system efficiencies is one method by which sustainability of energy may be ensured, for which miniaturization has successfully provided solutions. Miniature heat exchangers, owing to their high thermal performance, have the potential to provide energy efficient systems. In addition, their characteristics of compactness, small size and lesser weight have attracted widespread applications. Various works on micro- and minichannel heat exchangers as heat sinks and heat exchangers have been reviewed in this paper. Currently employed fabrication techniques and different applications have been summarized. An overview of the single-phase thermo-hydraulic studies in micro- and minichannel heat sinks has been presented. Literatures related co-current, counter-current and cross-current micro- and minichannel heat exchangers have been discussed. Finally, the persisting lacunae of this technology drawn from the review have been pointed out.

Review of micro- and mini-channel heat sinks and heat exchangers for single phase fluids

CLASSIFICATIONS OF HEAT EXCHANGERS Introduction Recuperation and Regeneration Transfer Processes Geometry of Construction Heat Transfer Mechanisms Flow Arrangements Applications Selection of Heat Exchangers BASIC DESIGN METHODS OF HEAT EXCHANGERS Introduction Arrangement of Flow Path in Heat Exchangers Basic Equations in Design Overall Heat Transfer Coefficient The LMTD Method for Heat Exchangers Analysis The e-NTU Method for Heat Exchangers Analysis Heat Exchanger Design Calculation Variable Overall Heat Transfer Coefficient Heat Exchanger Design Methodology FORCED CONVECTION CORRELATIONS FOR SINGLE-PHASE SIDE OF HEAT EXCHANGERS Introduction Laminar Forced Convection The Effect of Variable Physical Properties Turbulent Forced Convection Turbulent Flow in Smooth Straight Noncircular Ducts The Effect of Variable Physical Properties in Turbulent Forced Convection Summary of Forced Convection in Straight Ducts Heat Transfer from Smooth-Tube Bundles Heat Transfer in Helical Coils and Spirals Heat Transfer in Bends HEAT EXCHANGER PRESSURE DROP AND PUMPING POWER Introduction Tube-Side Pressure Drop Pressure Drop in Tube Bundles in Cross-Flow Pressure Drop in Helical and Spiral Coils Pressure Drop in Bends and Fittings Pressure Drop for Abrupt Contraction, Expansion, and Momentum Change Heat Transfer and Pumping Power Relationship FOULING OF HEAT EXCHANGERS Introduction Basic Considerations Effects of Fouling Aspects of Fouling Design of Heat Exchangers Subject to Fouling Operation of Heat Exchangers Subject to Fouling Techniques to Control Fouling DOUBLE-PIPE HEAT EXCHANGERS Introduction Thermal and Hydraulic Design of Inner Tube Thermal and Hydraulic Analysis of Annulus Parallel-Series Arrangements of Hairpins Total Pressure Drop Design and Operational Features DESIGN CORRELATIONS FOR CONDENSERS AND EVAPORATORS Introduction Condensation Film Condensation on a Single Horizontal Tube Film Condensation on Tube Bundles Condensation Inside Tubes Flow Boiling SHELL-AND-TUBE HEAT EXCHANGERS Introduction Basic Components Basic Design Procedure of a Heat Exchanger Shell-Side Heat Transfer and Pressure Drop COMPACT HEAT EXCHANGERS Introduction Heat Transfer and Pressure Drop THE GASKETED-PLATE HEAT EXCHANGERS Introduction Mechanical Features Operational Characteristics Passes and Flow Arrangements Applications Heat Transfer and Pressure Drop Calculations Thermal Performance CONDENSERS AND EVAPORATORS Introduction Shell and Tube Condensers Steam Turbine Exhaust Condensers Plate Condensers Air Cooled Condensers Direct Contact Condensers Thermal Design of Shell-and-Tube Condensers Design and Operational Considerations Condensers for Refrigeration and Air Conditioning Evaporators for Refrigeration and Air Conditioning Thermal Analysis Standards for Evaporators and Condensers APPENDICES Physical Properties of Metals and Nonmetals Physical Properties of Air, Water, Liquid Metals, and Refrigerants Each chapter also contains sections of Nomenclature, References, and Problems

Hongton Liu

Papers

Heat Exchangers: Selection, Rating, and Thermal Design

Convective condensation heat transfer in a horizontal condenser tube

The effect of inlet subcooling and heat transfer enhancement on two-phase flow pressure-drop type and thermal instabilities