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mehdi rasti,정지환 대한설비공학회 2017 International Journal Of Air-Conditioning and Refr Vol.25 No.4
Capillary tubes are widely used as expansion devices in small-capacity refrigeration systems. Since the refrigerant flow through the capillary tubes is complex, many researchers presented empirical dimensionless correlations to predict the refrigerant mass flow rate. A comprehensive review of the dimensionless correlations for the prediction of refrigerants mass flow rate through straight and coiled capillary tubes depending on their geometry and adiabatic or diabatic capillary tubes depending on the flow configurations has been discussed. A comprehensive review shows that most of previous dimensionless correlations have problems such as discontinuity at the saturated lines or ability to predict the refrigerant mass flow rate only for the capillary tube subcooled inlet condition. The correlations suggested by Rasti et al. and Rasti and Jeong appeared to be general and continuous and these correlations can be used to predict the refrigerant mass flow rate through all the types of capillary tubes with wide range of capillary tube inlet conditions including subcooled liquid, two-phase mixture, and superheated vapor conditions.
Rasti, Mehdi,Jeong, Ji Hwan Elsevier 2018 Applied thermal engineering Vol.143 No.-
<P><B>Abstract</B></P> <P>In spite of the simple geometry of capillary tubes, the refrigerant flow behavior through capillary tubes is complex. Numerous empirical correlations have been developed to predict the refrigerant mass flow rate through adiabatic helically coiled capillary tubes, but all of them have discontinuity problems at the saturated liquid line. In the present study, a generalized continuous empirical correlation is developed that can be used to predict the refrigerant mass flow rate through adiabatic helically coiled capillary tubes as well as straight capillary tubes. The new correlation can accommodate both subcooled liquids and saturated two-phase flow conditions in the capillary tube inlet condition. The proposed new correlation is validated with experimental data for R-22, R-134a, R-407C, R-410A, and LPG. In addition, the new correlation was compared with previous empirical correlations available in the open literature. The present correlation showed excellent performance in terms of its application range and degrees of continuity and accuracy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Correlation for mass flow rate through helically coiled adiabatic capillary. </LI> <LI> Single correlation is continuous over whole range of inlet conditions. </LI> <LI> New correlation can be used for straight and coiled capillary tube. </LI> </UL> </P>
Rasti, Mehdi,Ban, Jeong Ho,Jeong, Ji Hwan Elsevier 2017 Applied Thermal Engineering Vol.127 No.-
<P><B>Abstract</B></P> <P>Capillary tube, suction line heat exchangers (CT-SLHX) are widely used as expansion devices in small-capacity refrigeration and air-conditioning systems to enhance the refrigeration capacity and ensure that superheated refrigerant vapor enters the compressor. To calculate the mass flow rate through a capillary tube, a reliable non-adiabatic capillary tube model is necessary. Most previous correlations were developed separately for subcooled liquid inlet conditions and for saturated two-phase inlet conditions; so the models are not continuous at the saturated liquid point. An empirical model that is continuous at the saturated liquid point was developed and is introduced herein with a new dimensionless π parameter. This new empirical model is validated using experimental measurements available in the literature for the refrigerants R-134a, R-600a, R-410A, R-152a, and R-22. The new correlation shows good agreement with the experimental data.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Continuous correlation for mass flow rate through non-adiabatic capillary tube. </LI> <LI> Single correlation is applicable to subcooled, two-phase, and superheated regions. </LI> <LI> Correlation was validated to be applicable to R-134a, R-410A, R-152a, and R-22. </LI> </UL> </P>
Rasti, Mehdi,Jeong, Ji Hwan Elsevier 2018 Applied thermal engineering Vol.139 No.-
<P><B>Abstract</B></P> <P>Refrigerant flow through a capillary tube is complicated, and many empirical correlations have been proposed for calculating the refrigerant mass flow rate through capillary tubes. A common disadvantage of most previous empirical correlations is a discontinuity at the saturated liquid or saturated vapor lines. In the present study, a generalized continuous empirical correlation is developed that can be used to predict the refrigerant mass flow rate through a straight adiabatic capillary tube, for all capillary tube inlet conditions. The present empirical model was validated against experimental data available in the literature for R-12, R-22, R-134a, R-152a, R-404A, R-407C, R-410A, R-507A, and R-600a, covering subcooled and two-phase mixture inlet conditions. This correlation can be applied in refrigeration simulation tools to reduce runtime, and enhance the accuracy of refrigerant mass flow rate predictions for a wide range of refrigerants.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Correlation of mass flow rate through adiabatic capillary tube is developed. </LI> <LI> Single correlation is continuous across whole range of inlet conditions. </LI> <LI> Correlation is validated against experimental data of nine refrigerants. </LI> </UL> </P>
Experimental behavior assessment of short, randomly-oriented glass-fiber composite pipes
Salar Rasti,Hossein Showkati,Borhan Madroumi Aghbashi,Soheil Nejati Ozani,Tadeh Zirakian 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.47 No.6
The application of short, fiber-reinforced polymer composite pipes has been increasing rapidly. A comprehensive review of the prior research reveals that the majority of the previously-reported studies have been conducted on the filamentwound composite pipes, and fewer studies have been reported on the mechanical behavior of short, randomly-oriented fiber composite pipes. On this basis, the main objective of this research endeavor is to investigate the mechanical behavior and failure modes of short, randomly-oriented glass-fiber composite pipes under three-point bending tests. To this end, an experimental study is performed in order to explore the load-bearing capacity, failure mechanism, and deformation performance of such pipes. Fourteen properly-instrumented composite pipe specimens with different diameters, thicknesses, lengths, and nominal pressures have been tested and also simulated using the finite element approach for verification purposes. This study demonstrates the effectiveness of the diameter-to-thickness ratio, length-to-diameter ratio, and nominal pressure on the mechanical behavior and deformation performance of short, randomly-oriented glass-fiber composite pipes.
Mehdi Rasti,Ji-Hwan Jeong 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
Household refrigerators-freezers are one of the most popular energy-consuming home appliances. Moisture or small pieces of debris that have penetrated in the refrigeration system can clog the capillary tube. In the present study, two adjusting metering valves are installed at the outlet of refrigerator and freezer capillary tubes to investigate the effect of capillary tube clogging on the performance of a household refrigerator-freezer. Moreover, a transparent tube is installed at the inlet of the capillary tube for visualization of R600a flow state. Experiments are conducted under 85 g, 125 g, and 170 g refrigerant charge amount and metering valves are adjusted to be 25%, 50%, 75%, and 100% open. Visualization results at the capillary tube inlet showed the presence of two-phase flow under subcooling condition for most of the experiments. However, results showed the fully liquid refrigerant flow by increasing the refrigerant charge and also increasing the refrigerant flow restriction.