Showing papers on "Subcooling published in 2016"
TL;DR: In this article, a theoretical comparison among different commercial refrigeration systems in terms of annual energy consumption and environmental impact is presented, based on weather data in Valencia (Spain) and in Athens (Greece), as well as on the running modes of a conventional European supermarket.
Abstract: This paper presents a theoretical comparison among different commercial refrigeration systems in terms of annual energy consumption and environmental impact. Eight configurations were studied: a R744/R134a cascade refrigeration system (baseline), a conventional and an improved R744 booster system, two R744 booster solutions with dedicated mechanical subcooling, a R744 booster with parallel compression and two solutions which combined the parallel compression and the mechanical subcooling. The evaluation was based on the weather data in Valencia (Spain) and in Athens (Greece), as well as on the running modes of a conventional European supermarket. A transition zone, which occurred between subcritical and transcritical operations, was adopted. The results showed that all the enhanced configurations may achieve a comparable energy saving to the one of the baseline in both the selected locations. Furthermore, they allow reducing the Total Equivalent Warming Impact (TEWI) by at least 9.6% beside the cascade solution.
132 citations
TL;DR: The authors gratefully acknowledge the Ministerio de Economia y Competitividad (NE2014-53760-R.7) and Jaume I University (project P11B2015-66) for financing this research work as mentioned in this paper.
Abstract: The authors gratefully acknowledge the Ministerio de Economia y Competitividad (project ENE2014-53760-R.7) and Jaume I University (project P11B2015-66) for financing this research work.
112 citations
TL;DR: In this paper, a comparative analysis of thermodynamic performance of cascade refrigeration systems (CRSs) for refrigerant couples R41/R404A and R23/R 404A to discover whether R41 is a suitable substitute for R23 is presented.
76 citations
TL;DR: In this article, a modified mechanistic force-balance model for bubble departure in subcooled flow boiling has been proposed to evaluate the predictive accuracy of the predicted bubble departure diameter in a wide range of orientation angle, subcooling, heat flux, mass flux and pressure conditions.
73 citations
TL;DR: In this article, the performance of a LiBr/H2O absorption cooling system and a PCM system was investigated using 20 kg each of Erythritol to compare three heat transfer enhancement techniques; circular finned, longitudinal finned and multitube systems.
69 citations
TL;DR: In this article, the authors investigated the solidification behavior of water dispersed with graphene nanoplatelets (GNP) in a spherical container during solidification and found that the addition of GNP resulted to an appreciable reduction in the subcooling of water from −7°C to −2.5°C along with reduction of 25% in solidification time owing to its high thermal conductivity and larger specific surface area.
Abstract: This study aimed to investigate the solidification behavior of water dispersed with graphene nanoplatelets (GNPs) in a spherical container during solidification. The nanofluid phase change materials (NFPCMs) with GNP mass concentrations of 0.3%, 0.6%, 0.9% and 1.2% were prepared and their corresponding thermal conductivity was measured both in liquid and solid states. The thermal conductivity data showed the linear and nonlinear enhancement in liquid and solid state, respectively. The addition of GNPs resulted to an appreciable reduction in the subcooling of water from −7 °C to −2.5 °C along with reduction of 25% in solidification time owing to its high thermal conductivity and larger specific surface area. The onset of solidification got advanced in the case of NFPCM due to higher cooling rate in the subcooling region for any given driving potential. The accelerated mode of energy charging occurred during 78% of total solidification time.
68 citations
TL;DR: In this paper, an Eulerian-Eulerian, two-fluid CFD model is evaluated over a large database of subcooled boiling flows, avoiding the rather popular case-by-case tuning of descriptive models to a limited number of experiments.
67 citations
TL;DR: In this paper, a single-pass gas-dominant flowloop was used to measure hydrate growth and particle deposition rates with variable liquid holdup (1 − 10 − vol%) and subcooling (1−20 − ǫ).
64 citations
TL;DR: In this article, a novel process configuration for large scale natural gas liquefaction process is introduced and analyzed, which is based on replacement of vapor compression refrigeration cycle by absorption refrigeration system.
62 citations
TL;DR: In this paper, an experimental study on flow boiling pressure drop and heat transfer of a new environmentally friendly refrigerant R1233zd(E), in a parallel multi-microchannel evaporator was carried out.
60 citations
TL;DR: In this article, the experimental results of a parametric series of liquid nitrogen chilldown tests of a stainless steel tube were presented, and the experimental data covered liquid Reynolds numbers ranging from 800 to 230,000 and local pressures ranging from 150 to 725 kPa.
TL;DR: In this article, a porous coating with reentrant channels with sintered copper powder was used for pool boiling and compared with a solid sample with the same reentrants configurations.
TL;DR: In this paper, an experimental investigation is conducted to investigate the bubble growth characteristics during flow boiling in a single microchannel with 0.5mm × 1mm rectangular cross-section, and the heat transfer performance of flow boiling and its influencing factors are studied.
TL;DR: In this article, the authors extensively assess and validate the wall heat flux partitioning (WHFP) model in the coupled Eulerian-Eulerian Multiphase Flow (EEMF) method to simulate subcooled flow boiling conditions at high pressures.
TL;DR: In this paper, the experimental results of the chilldown of a thin-walled stainless steel tube with liquid nitrogen under a wide range of pressures and mass fluxes in terrestrial gravity are presented.
TL;DR: In this paper, the formation of cyclopentane (CP)-methane binary sII-type hydrate in brine solutions at two salinities (3.5% and 7.0% NaCl, w/w) was investigated.
TL;DR: In this article, a superhydrophilic surface was prepared on stainless steel spheres by spray coating of silica nanoparticles to enhance the surface roughness at the nanoscale.
TL;DR: In this paper, the authors evaluate the heat transfer through small thermal energy storage (TES) units filled with different phase change materials (PCMs): free-form and micro-encapsulated PCMs.
TL;DR: Porous interconnected microchannel nets are fabricated in this article using copper powder sintering and wire electric discharge machining, which yields a higher heat transfer coefficient (HTC) than its solid copper counterpart at any liquid subcooling and suppresses the temperature excursion by lowering the wall superheat at the onset of nucleate boiling (ONB).
TL;DR: In this article, the influence of non-condensable gas on water vapor condensation heat transfer on an isothermal vertical aluminum plate in an air mass fraction range of 0.05-0.5 was investigated.
TL;DR: In this article, the authors describe the method and results of experimental study of heat transfer during cooling the spherical patterns from nickel, stainless steel, and copper with initial temperature above 700°C in water at subcoolings up to 70 K.
TL;DR: In this paper, a basic CO 2 transcritical/subcritical commercial refrigeration system is considered, applied to cold rooms and display cabinets in a supermarket, taking advantage of a large fire prevention water tank.
Abstract: A basic CO 2 transcritical/subcritical commercial refrigeration system is considered, applied to cold rooms and display cabinets in a supermarket. Subcooling of the refrigerant or heat recovery from condensation can be performed, taking advantage of a large fire prevention water tank. The whole refrigeration system is modelled in a TRNSYS environment, taking into account the hourly weather data and calculating the hourly cooling load demand from display cabinets and cold rooms equipment. New types have been written to describe display cabinets and cold rooms, CO 2 refrigerating units and a particular water store. Simulations consider a simple double compression cycle with liquid receiver, and other options among which an auxiliary compressor. Results show that CO 2 plants are feasible and energetically acceptable in mild climates, provided that improvements to standard cycle are adopted. Furthermore, heat recovery can be effectively performed through the employment of a heat storage.
TL;DR: In this article, the authors measured the wall and liquid phase heat transfer of a single bubble in subcooled boiling at a sampling frequency of 50 kHz using a MEMS sensor.
TL;DR: In this article, the authors presented a novel combination of transcritical carbon dioxide refrigeration with Boosted-MED (Multi-Effect-Desalination) system to provide cooling and fresh water simultaneously.
TL;DR: In this paper, a new mechanistic model for predicting the maximum diameter of attached vapor bubbles in a subcooled boiling flow is proposed, which is derived from the lumped energy balance for the bubbles.
TL;DR: In this paper, the effect of pipe diameter, heat flux and mass flux on boiling pressure drop and local heat transfer coefficient is investigated for low pressure flow boiling with water as the working medium.
TL;DR: In this paper, the second generation HP-ALTA MkII was used to measure the nucleation curves of Structure II (sII)-forming methane-propane mixed gas hydrates on the surface of a quasi-free water droplet suspended in involatile hydrocarbon oil, squalane.
TL;DR: In this paper, the authors investigated natural convection and nucleate boiling of PF-5060 dielectric liquid on 10×10mm uniformly heated copper (Cu) surfaces with different diameter dimples, for potential application to immersion cooling of high power computer chips.
TL;DR: In this paper, the authors present new systematic data on cooling the metal spheres in subcooled isopropanol and in perfluorohexane (FC-72) at very high subcoolings, up to 160 K. The experiments showed that stable film boiling was the dominant cooling regime; heat transfer intensity was approximately two-three times greater than in saturated film boiling at the sphere surface.
TL;DR: In this paper, the authors present an analysis of sliding bubble and wall heat transfer parameters measured during subcooled boiling in a square, vertical, upward flow channel, and show that sliding bubbles involve two distinct growth behaviors: (i) at low mass fluxes, sliding bubbles grew fast near the nucleation site, subsequently shrank, and then grew again as mass flux increased.