A Generalized Neural Network Model of Refrigerant Mass Flow Through Adiabatic Capillary Tubes and Short Tube Orifices

2007 ◽  
Vol 129 (12) ◽  
pp. 1559-1564 ◽  
Author(s):  
Ling-Xiao Zhao ◽  
Chun-Lu Zhang ◽  
Liang-Liang Shao ◽  
Liang Yang
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Mass Flow ◽  
Transfer Functions ◽  
Heat Pumps ◽  
Capillary Tubes ◽  
Two Phase ◽  
Bp Network ◽  
Inlet Conditions ◽  
Short Tube

Adiabatic capillary tubes and short tube orifices are widely used as expansive devices in refrigeration, residential air conditioners, and heat pumps. In this paper, a generalized neural network has been developed to predict the mass flow rate through adiabatic capillary tubes and short tube orifices. The input/output parameters of the neural network are dimensionless and derived from the homogeneous equilibrium flow model. Three-layer backpropagation (BP) neural network is selected as a universal function approximator. Log sigmoid and pure linear transfer functions are used in the hidden layer and the output layer, respectively. The experimental data of R12, R22, R134a, R404A, R407C, R410A, and R600a from the open literature covering capillary and short tube geometries, subcooled and two-phase inlet conditions, are collected for the BP network training and testing. Compared with experimental data, the overall average and standard deviations of the proposed neural network are 0.75% and 8.27% of the measured mass flow rates, respectively.

Assessment of Dimensionless Correlations for Prediction of Refrigerant Mass Flow Rate Through Capillary Tubes — A Review

2017 ◽  
Vol 25 (04) ◽  
pp. 1730004 ◽  
Author(s):  
Mehdi Rasti ◽  
Ji Hwan Jeong
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Capillary Tube ◽  
Capillary Tubes ◽  
Two Phase ◽  
Comprehensive Review ◽  
Wide Range ◽  
Inlet Conditions ◽  
Dimensionless Correlations

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.

Empirical Correlations for Sizing Adiabatic Capillary Tube Using LPG as Refrigerant in Split-Type Air-Conditioner

2014 ◽  
Vol 493 ◽  
pp. 99-104
Author(s):  
Shodiya Sulaimon ◽  
Azhar Abdul Aziz ◽  
Amer Nordin Darus ◽  
Henry Nasution
Keyword(s):  
Experimental Data ◽  
Mass Flow ◽  
Capillary Tube ◽  
Air Conditioner ◽  
Capillary Tubes ◽  
Two Phase ◽  
Design And Optimization ◽  
Mass Flow Rates ◽  
Inner Diameter ◽  
Vapour Compression

This paper presents correlations for sizing adiabatic capillary tubes which serves as an expansion device in split-type air-conditioner with LPG, novel hydrocarbon (HC) mixtures of butane (HC600) and propane (HC290) as refrigerant. A homogenous two-phase flow model developed by the authors and also experimental investigation of the Liquified Petroluem Gas (LPG) refrigerant flow in adiabatic capillary tubes were used in this study. The theoretical model was used to assess various percentage compositions of these HC mixtures and validated with the experimental data. For each HC refrigerant mixture, correlations for sizing adiabatic capillary tube which contains the relevant factors, viz. capillary tube inner diameter, inlet pressure, refrigerant mass flow rate, capillary tube surface roughness and capillary tube inlet subcooling was developed. The proposed correlations were compared with the authors measured data and found to be in good agreement. Further validation was made by comparing the mass flow rates predictions of the correlations with experimental data of previous studies and found that these correlations are consistent. The correlations can be used in small vapour compression refrigeration systems working with the HC refrigerant mixtures for practical design and optimization.

Modeling of Supercritical CO2 Flow Through Short Tube Orifices

2005 ◽  
Vol 127 (6) ◽  
pp. 1194-1198 ◽  
Author(s):  
Chun-Lu Zhang ◽  
Liang Yang
Keyword(s):  
Mass Flow ◽  
Supercritical Co2 ◽  
Fluid Model ◽  
Velocity Slip ◽  
Heat Pumps ◽  
Tube Length ◽  
Good Prediction ◽  
Two Phase ◽  
Promising Alternative ◽  
Short Tube

The transcritical cycle of carbon dioxide (CO2) is a promising alternative approach to heat pumps and automobile air conditioners. As an expansion device, the short tube orifice in a transcritical CO2 system usually receives supercritical fluid at the entrance and discharges a two-phase mixture at the exit. In this work, a two-fluid model (TFM) is developed for modeling the flow characteristics of supercritical CO2 through the short tube orifice. The deviations between the TFM predictions and the measured mass flow rates are within ±20%. Meanwhile, the TFM predicts reasonable pressure, temperature, and velocity distributions along the tube length. The small values of interphase temperature difference and velocity slip indicate that the nonequilibrium characteristics of the two-phase flow of CO2 in the short tube orifice are not significant. Consequently, the homogeneous equilibrium model reduced from the TFM gives a good prediction of the mass flow rate as well.

Evaluation of Two-Phase Frictional Pressure Drop Correlations Against Experimental Data

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Wei Li ◽  
Kunrong Shen ◽  
Boren Zheng ◽  
Xiang Ma ◽  
S. A. Sherif ◽  
...  
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Mass Flow ◽  
Flow Model ◽  
Saturation Temperature ◽  
Separated Flow ◽  
Outer Diameter ◽  
Two Phase ◽  
Homogeneous Flow ◽  
Frictional Pressure Drop

Abstract Results are presented here from an experimental investigation on tube side two-phase characteristics that took place in four tested tubes—the 1EHT-1, 1EHT-2, 4LB, and smooth tubes. The equivalent outer diameter of the tube was 9.52 mm and the inner diameter was 8.32 mm. Condensation tests were conducted using refrigerant R410A at a saturation temperature of 318 K, over a mass flow range of 150–450 kg m−2 s−1, with inlet and outlet vapor qualities of 0.8 and 0.2, respectively. Evaporation tests were performed at a saturation temperature of 279 K, over a mass flow range of 150–380 kg m−2 s−1, with inlet and outlet vapor qualities of 0.2 and 0.8, respectively. Pressure drop data of the four tested tubes were collected to evaluate five identified prediction correlations based on the separated flow model and the homogeneous flow model. The separated flow approaches presented predictions with average MAEs of 24.9% and 16.4% for condensation and evaporation data, respectively, while the average MAEs of the homogeneous flow model were 31.6% and 43.4%, respectively. Almost all the identified correlations underestimated the frictional pressure drop of the 4LB tube with MAEs exceeding 30%. An earlier transition of different flow patterns was expected to occur in the EHT tubes while developing a new diabatic flow pattern map is needed for the 4LB tube. A new correlation was presented based on the two-phase multiplier Φ and the Martinelli parameter Xtt, which exhibited excellent predictive results for the experimental data.

A Critical Review on the Numerical Methods of Two-Phase Flows

2012 ◽  
Author(s):  
Muhammet Balcilar ◽  
Ahmet Selim Dalkiliç ◽  
Ali Çelen ◽  
Nurullah Kayaci ◽  
Somchai Wongwises
Keyword(s):  
Neural Network ◽  
Heat Transfer ◽  
Experimental Data ◽  
Numerical Methods ◽  
Critical Review ◽  
Optimization Techniques ◽  
Numerical Analyses ◽  
Heat Transfer Characteristics ◽  
Two Phase ◽  
Transfer Characteristics

The two-phase flow processes play a significant role in the heat transfer processes in the chemical and power industry, including in nuclear power plants. This study is a critical review on the determination of the heat transfer characteristics of pure refrigerants flowing in vertical and horizontal tubes. The authors’ previous publications on this issue, including the numerical analyses, are summarized here. The lengths of the vertical and horizontal test sections varied between 0.5 m and 4 m countercurrent flow double-tube heat exchangers with refrigerant flowing in the inner tube and cooling water flowing in the annulus. The measured data are compared to numerical predictions based on the solution of the artificial intelligence methods and CFD analyses for the condensation and evaporation processes in the smooth and enhanced tubes. The theoretical solutions are related to the design of passive containment cooling systems (PCCS) in simplified water boiling reactors (SWBR). A genetic algorithm (GA), various artificial neural network models (ANN) such as multilayer perceptron (MLP), radial basis networks (RBFN), generalized regression neural network (GRNN), and adaptive neuro-fuzzy inference system (ANFIS), and various optimization techniques such as unconstrained nonlinear minimization algorithm-Nelder-Mead method (NM), non-linear least squares error method (NLS), and Fluent CFD program are used in the numerical solution. It is shown that the heat transfer characteristics of laminar and turbulent condensing and evaporating film flows such as heat transfer coefficient and pressure drop can be predicted by means of numerical analyses reasonably well if there is a sufficient amount of reliable experimental data. Regression analysis gave convincing correlations, and the most suitable coefficients of the proposed correlations are depicted as compatible with the large number of experimental data by means of the computational numerical methods. Dependency of the output of the ANNs from various numbers of input values is also shown for condensing and evaporating flows.

NUMERICAL AND EXPERIMENTAL INVESTIGATION OF THE FLOW CHARACTERISTICS OF R134a FLOWING THROUGH ADIABATIC HELICAL CAPILLARY TUBES

2012 ◽  
Vol 20 (04) ◽  
pp. 1250019 ◽  
Author(s):  
SUKKARIN CHINGULPITAK ◽  
JATUPORN KAEW-ON ◽  
SOMCHAI WONGWISES
Keyword(s):  
Experimental Data ◽  
Capillary Tube ◽  
Flow Characteristics ◽  
Phase Region ◽  
Liquid Region ◽  
Alternative Refrigerants ◽  
Capillary Tubes ◽  
Local Pressure ◽  
Two Phase ◽  
Comparison Results

This paper presents numerical and experimental results of the flow characteristics of R134a flowing through adiabatic helical capillary tubes. The local pressure distribution along the length of the capillary tubes is measured at inlet pressures ranging from 10 to 14 bar, mass flow rates from 8 to 20 kg h-1, and degrees of subcooling from 0.5°C to 15°C. The theoretical model is based on conservation of mass, energy and the momentum of the fluids in the capillary tube. The model is divided into three regions: subcooled liquid region, metastable liquid region and equilibrium two-phase region and can be applied for various tube geometries, new alternative refrigerants and critical or noncritical flow conditions. The model is validated by comparing results from the present experimental data with that of the available literature. Based on the comparison results, the model used in the present study provides reasonable agreement with the experimental data.

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