Numerical simulation of capillary tubes. Application to domestic refrigeration with isobutane (original) (raw)
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Heat and Mass Transfer, 2011
Small vapor compression refrigeration systems incorporate a non-adiabatic capillary tube called a capillary tube-suction line heat exchanger (SLHX) in order to improve performance. The thermodynamic properties of the refrigerant in the capillary tube and suction pipe are influenced by associated phenomena. This study compares various relevant models. Based on the comparison recommended correlations were selected and the simulation results show that the friction factor model has the most dominant.
International Journal of Current Engineering and Technology, 2016
In the present study, phase change of refrigerant flow through capillary tube under adiabatic conditions has been studied based on computational fluid dynamics technique. Eulerian multiphase flow Homogeneous equilibrium model along with thermal phase change based on mass transfer mechanism was used for simulation of refrigerant flow through adiabatic straight capillary tube. The effect of various design parameter such condensation pressure, capillary tube length and capillary tube diameter on the flashing inception point has been discussed numerically. The numerical model based on finite volume method using turbulence model gives the behavior of refrigerant properties such as field of pressure, temperature, dryness fraction, void fraction and velocity along the distance of capillary tube which helps in the understanding of beginning of vaporization phenomenon. The present numerical model has been validated with the others models and a good agreement are obtained which can be lead to depend up on ANSYS CFX 16.1 in design and optimization of capillary tube of refrigeration industry.
IJERT-Simulation of Flow Characteristics of Refrigerant inside Adiabatic Straight Capillary Tube
International Journal of Engineering Research and Technology (IJERT), 2013
https://www.ijert.org/simulation-of-flow-characteristics-of-refrigerant-inside-adiabatic-straight-capillary-tube https://www.ijert.org/research/simulation-of-flow-characteristics-of-refrigerant-inside-adiabatic-straight-capillary-tube-IJERTV2IS90720.pdf In the present investigation, an attempt is made to develop mathematical model to determine the flow characteristics of refrigerant inside a straight capillary tube for adiabatic flow conditions. The proposed model can predict the length of the adiabatic straight capillary tube for a given mass flow rate. In the present study R-12 has been used as a working fluid inside the straight capillary tube of diameter 1.17 mm and 1.41 mm and used the same model to study the flow characteristics of refrigerant in ANSYS CFX software. Finally the results of mathematical model are valuated with ANSYS CFX and the results are found to be in fair agreement.
Numerical investigation of refrigerant flow through adiabatic capillary tube
In this work a computational investigation of detailed flow structures in two-phase refrigerant flow through an adiabatic capillary tube has been presented. Finite volume method with volume of fluid method has been used in the computation. A source term has been incorporated in the governing equations to model the rate of evaporation of liquid refrigerant into vapuor state. The source term effectively controls the mass transfer phenomenon during the transformation of liquid refrigerant into vapor phase. The present model has been validated with the experimental data available in the literature. The important flow properties of the single liquid and liquid-vapour mixture such as temperature, pressure, velocity, dryness fraction and flow variables at different locations of the tube and at different time levels have been presented. It has been observed that with the inception of vapor the flow properties changes drastically and a nonequilibrium state exists for some time between the two-phases.
Numerical analysis of adiabatic flow of refrigerant through a spiral capillary tube
International Journal of Thermal Sciences, 2009
In the present work, a homogenous model including the metastable liquid region has been developed for the adiabatic flow of refrigerant through the spiral capillary tube. In order to develop the model, both liquid region and two phase region have been discretized into infinitesimal segments to take into account the effect of varying radius of curvature of spiral tube on the friction factor. The effect of the pitch of spiral on the mass flow rate of refrigerant and capillary tube length has been investigated. A comparison of flow characteristics of refrigerant R22 and its alternatives, i.e., R407C and R410A has been made at different operating conditions at the inlet of the capillary tube and it has been found that the flow characteristics of R22 and R407C are almost similar for a given condenser pressure and degree of subcooling at the inlet of capillary tube.
Experimental investigation of R600a refrigerant flow inside adiabatic capillary tube
Sigma Journal of Engineering and Natural Sciences, 2016
Capillary tubes are often used as an expansion component in the refrigeration systems of household refrigerators. During the flow of the refrigerant inside the capillary tube, due to pressure loss of the refrigerant, the refrigerant starts boiling and towards the end of the capillary tube, different types of twophase regimes occur. Therefore; the refrigerant flow inside the capillary tube is a complex phenomenon and there are many experimental and numerical studies analyzing this refrigerant flow. However; in literature there are hardly any experimental studies analyzing refrigerant flow in small scale refrigeration systems using isobutane (R600a) as the refrigerant. In this study, the two-phase flow regimes of the R600a refrigerant inside a vertical adiabatic capillary tube with 0.80 mm inner diameter, under different condensation pressures subcooling degrees and capillary tube lengths, are recorded via high-speed camera; and the effects of different parameters on refrigerant mass flow are analyzed. The boundary conditions for the condensation pressure, subcooling degree and capillary tube length are determined in accordance with a small scale refrigeration system.
A Review report on “CFD analysis of Fluid Flow in a capillary tube using various refrigerant”
In the past several years a number of new alternative refrigerant have been discovered to replace the existing refrigerants used in refrigerating equipment for improvement of performance. In order to study these refrigerants extensively an in-depth knowledge of their single-phase heat transfer characteristics, thermodynamic properties as well as simulation analysis is needed. This paper provides a literature review of current research that has been conducted on single phase flow for alternative refrigerants, addresses a number of relations for determining the thermodynamic properties of these alternative refrigerants with computational fluid analysis using different software likewise ANSYS ; and discusses their sensitivity to uncertainty. Finally, an overview of some of the current research that has been conducted on various enhancements and refrigerant / oil mixtures is provided as well. Present paper give a brief study about throttling expansion of refrigerant, capillary tube, refrigerant property and mathematical correlation for the flow through the capillary tubes of different geometries operating under adiabatic and diabetic flow conditions. Keywords: CFD; Fluid Flow; ANSYS; Refrigeration.
Improved refrigerant characteristics flow predictions in adiabatic capillary tube
Research Journal of Applied Sciences, Engineering and Technology, 2012
This study presents improved refrigerant characteristics flow predictions using homogenous flow model in adiabatic capillary tube, used in small vapor compression refrigeration system. The model is based on fundamental equations of mass, momentum and energy. In order to improve the flow predictions, the inception of vaporization in the capillary tube is determined by evaluating initial vapor quality using enthalpy equation of refrigerant at saturation point and the inlet entrance effect of the capillary tube is also accounted for. Comparing this model with experimental data from open literature showed a reasonable agreement. Further comparison of this new model with earlier model of Bansal showed that the present model could be use to improve the performance predictions of refrigerant flow in adiabatic capillary tube.
IJERT-CFD Flow Analysis of a Refrigerant inside Adiabatic Capillary Tube
International Journal of Engineering Research and Technology (IJERT), 2013
https://www.ijert.org/cfd-flow-analysis-of-a-refrigerant-inside-adiabatic-capillary-tube https://www.ijert.org/research/cfd-flow-analysis-of-a-refrigerant-inside-adiabatic-capillary-tube-IJERTV2IS90289.pdf Capillary tubes are widely used as a refrigerant flow control device in small refrigeration systems. Since the flow behaviour inside the capillary tube is complex, many physical models are necessary to predict the characteristics of the refrigerant flow in a capillary tube. The refrigerant leaves the compressor at high pressure and temperature and enters the condenser. After leaving the condenser the refrigerant is at medium temperature and high pressure and then it enters the Capillary tube. In the Capillary tubes the pressure and the temperature of the refrigerant is reduced drastically and suddenly. Thus us it is the throttling valve where the temperature of the refrigerant is reduced and it is then able to produce the cooling effect in the evaporator of the refrigerator or the cooling coil of the air conditioner. In the present investigation, an attempt is made to analyze the flow Analysis of the refrigerant inside a straight capillary tube and coiled capillary tube for adiabatic flow conditions. The proposed model can predict flow characteristics in adiabatic capillary tubes for a given mass flow rate. In the present study R-22 has been used as a working fluid inside the straight capillary tube and coiled capillary tube of diameter 1.27 mm and used the same model to study the flow characteristics of refrigerant in ANSYS CFX software. It is observed from the results dryness fraction by using the helical capillary tube is better than straight capillary tube. The best suitable helical coiled design is suggested.