Quantification of liquid refrigerant distribution in parallel flow microchannel heat exchanger using infrared thermography

Li, Huize; Hrnjak, Pega

doi:10.1016/j.applthermaleng.2015.01.003

Cited by 45 publications

(15 citation statements)

References 27 publications

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“…There was numerous research in the last decade on how to quantify refrigerant maldistribution (Vist and Pettersen, 2004;Kim and Kim, 2011;Zou and Hrnjak, 2013;Li and Hrnjak, 2015a) and its effect on cooling capacity (Kulkarni et al, 2004;Zou et al, 2014;Li and Hrnjak, 2015b).…”

Section: List Of Tablesmentioning

confidence: 99%

Control of flash gas bypass MAC system with emphasis on start-ups and transients

Hrnjak

2017

International Journal of Refrigeration

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Flash Gas Bypass (FGB) approach has the benefits of eliminating refrigerant maldistribution and reducing refrigerant pressure drop across the evaporator. Most of the previous research on flash gas bypass focused on performance improvement in steady state and demonstrated that compared to direct expansion mode (DX), FGB mode have better performance. However, the control strategy of FGB system and dynamic behavior during start-ups and transients were not yet clearly defined and investigated. In this paper, a novel

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Section: List Of Tablesmentioning

confidence: 99%

Control of flash gas bypass MAC system with emphasis on start-ups and transients

Hrnjak

2017

International Journal of Refrigeration

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“…The particles have a peak excitation wavelength of 542 nm, a peak emission wavelength of 612 nm, and a density of 1.05 g/cm 3 . At the concentration used, the presence of these particles has a negligible impact on the density, viscosity [22,23], or surface tension [24,25].…”

Section: Working Fluidsmentioning

confidence: 99%

“…Technologies that leverage the enhanced transport behavior at small scales to extend their performance envelopes include fuel cells that are able to achieve higher efficiencies and power densities [1], chemical reactors that have greater mass transfer and reaction rates 4 leading to higher yields and/or smaller system sizes [2], and high-performance compact heat exchangers [3]. In particular, two-phase microchannel heat sinks are an attractive option for the thermal management of electronic devices, capable of removing high heat fluxes while maintaining uniformity in device surface temperatures; however two-phase operation is not widely employed due to difficulties associated with performance prediction [4].…”

Section: Introductionmentioning

confidence: 99%

Mechanistic modeling of the liquid film shape and heat transfer coefficient in annular-regime microchannel flow boiling

Patel

Weibel

Garimella

2017

International Journal of Heat and Mass Transfer

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A methodology is proposed for predictive modeling of the liquid-gas interface shape and saturated flow boiling heat transfer coefficient in two-phase microchannel flows within the annular regime. The mechanistic model accounts for the effects of surface tension and interface curvature, gravity, and shear stress in determining the liquid film shape; one-dimensional conduction is assumed to occur across the variable-thickness film to calculate wall heat transfer coefficients locally along the channel length. Model performance is benchmarked against 251 experimentally measured heat transfer coefficient values taken from the literature for annularregime flow boiling in microchannels of a rectangular cross-section. These data are successfully predicted with a mean absolute error of 21.7%, and 72.1% of the points lie within an error band of ±30%. The match to data is poorest at lower vapor qualities corresponding to the onset of the annular regime, for which the heat transfer coefficient is underpredicted; an experimental investigation is performed to better understand the disparity under these operating conditions. Liquid film shapes are measured during adiabatic annular flow through microchannels of square cross-section for a range of channel hydraulic diameters (160 µm, 510 µm, 1020 µm) and operating conditions, so as to control the void fraction and Weber number of the flow. Using air and water as the working gas and liquid, respectively, trends in film behavior are identified and 2 compared against model predictions. The experimental findings reveal the non-negligible impact of capillary pumping on the interface morphology at the onset of the annular regime.

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“…Using different fluids in heat exchangers allows an evaluation of the performance of the heat exchanger. This involves looking at the cooling process and the temperature difference, and deriving correlations between the concentration and flow, and the boiling temperature [8][9][10][11][12][13]. Examination of the thermal and dynamic analysis of plate-type heat exchangers has been performed using computational fluid dynamics (CFD) programs, and analytical studies using numerical calculations that have been used to investigate the thermal conductivity of heat exchangers have been reviewed in published literature.…”

Section: Introductionmentioning

confidence: 99%

“…A range of different channel angles have been investigated to show the effect of surface area on heat transfer. The heat transfer and heat transfer coefficient has been examined with important parameters, such as the Reynolds number and the Nusselt number, and taken into account in the design of heat exchangers [9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Examination of Different Heat Exchangers and the Thermal Activities of Different Designs

2017

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In this study, instead of gasketed or brazed plate heat exchangers, which are used in various fields of application, a direct metal sintering method is used to design a heat exchanger with its original geometry and with different geometries. Studies of heat exchangers found in published literature were reviewed, and the thermal behaviors of the proposed unique designs were examined. Usually heat exchangers using this design do not use channel spacing angles of 30-45-60-75• for the plate ducts. The thermal behaviors of the fluid-circulating systems were analyzed using ANSYS FLUENT software, and they used the boundary conditions found in the literature for this design. Heat transfer between the heat exchanger channels and channel walls was calculated. The analyses results show that an increase in the amount of heat transfer surface area and also an increase in surface roughness increased the amount of positive heat transfer.

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Quantification of liquid refrigerant distribution in parallel flow microchannel heat exchanger using infrared thermography

Cited by 45 publications

References 27 publications

Control of flash gas bypass MAC system with emphasis on start-ups and transients

Control of flash gas bypass MAC system with emphasis on start-ups and transients

Mechanistic modeling of the liquid film shape and heat transfer coefficient in annular-regime microchannel flow boiling

Examination of Different Heat Exchangers and the Thermal Activities of Different Designs

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