An experimental study of two-phase flow in idealised tube bundles

This thesis reports on an experimental study of air-water mixtures flowing through idealized shell and tube, in-line and staggered heat exchangers. The measured void fractions in the maximum and minimum gaps between the tubes are reported at near atmospheric conditions, to give local variations for different tube diameters and tube bundle arrangements. The void fraction measurements were made using a gamma-ray densitometer. The pressure drops in the tube bundles are also reported. These data are compared with the correlations available in the open literatures to investigate the void fraction and pressure drop prediction methods for these heat exchangers. The in-line 38 mm tube bundle is shown to provide no significant effect on void fraction or drag force when compared with the 20 mm tube diameter bundle. A new void fraction model is therefore proposed by modifying the characteristic length of an existing slip ratio method. A new pressure drop model is presented. The acceleration pressure drop between the tubes from the separation to re-attachment is shown to be responsible for some of the frictional pressure drop with a liquid film on the tubes responsible for the remainder. The staggered bundle shows the bundle arrangement gives different void fraction and different pressure drop data when compared to the in-line bundle

Modelling of the flow of refrigerant 134a in capillary tubes

Practical tools for the design of capillary tubes for refrigeration systems employing the traditional CFC-12 and HCFC-22 as refrigerants are widely available. Due to environmental concern of the depletion of ozone layer and global warming, CFCs and HCFCs have to be phased out eventually according to the Montreal Protocol. As a result, a number of alternative refrigerants including HFC-134a have emerged as promising chlorine free alternatives to CFC-12 in domestic refrigerators and freezers. The proper size of a capillary tube with a new refrigerant is a critical factor for the optimum performance of a refrigeration system. This study presents a computer model KAPILARI, which has been developed to predict the length of capillary tube used as an expansion device in small refrigerating and air-conditioning systems. The pressure drop through a capillary tube in the single-phase and two-phase regions is modelled in an attempt to predict the size of capillary tube. The model is based on the governing equations of conservation of mass, energy and momentum. Stoecker's basic model was modified with the consideration of various effects due to sub cooling, choked flow and friction factor used in single-phase region. The developed model has been validated by employing available studies and found to agree well with the experimental data and other mathematical model predictions of HFC-134a. The capability of the program has been tested and simulations are carried out to investigate the effect of varying the operating and design parameters of the system, namely cooling capacity, evaporating temperature, degree of superheat, condensing temperature, degree of subcoo1ing and inner diameter of capillary tube, on the length of the capillary tube. The developed model is an effective tool of capillary tube's 377$ design and optimization for systems using HFC-134

Determine physical properties of an organic citric acid (processed lime juice) dissolve with water using experimental apparatus

This paper describes experimental studies on the physical properties of processed lime juice to dissolve with water. Lime juice as known as organic citric acid have many advantages in our life especially in food industries, pharmaceutical industries, anticancer and antioxidant and cleaning agent. Physical properties of liquid include pH, viscosity, density, molar mass and surface tension. This Study conducted using common laboratory apparatus such as Pycnometer, the pH device (HI 9811 pH), Viscolite700 etc. The additional organic citric acid by percentage in water was changed the physical properties of liquids. The future strategy of this research is to introduce organic lime juice mixed with water in spray system as cleaning agent, reduce air pollution and reduce water consumption for Commercial Restaurant Equipment

A Comparative Study of Turbulence Models on Aerodynamics Characteristics of a NACA0012 Airfoil

This paper presented a computational fluid dynamics (CFD) simulation of air flow past a 2D model NACA0012 airfoil at high Reynolds number (Re = 3.0 x 106) at various angles of attack (-10° to 15°). The simulations were undertaken to inform on how the fluid flowed around the airfoil by solving the steady state governing equations of continuity and momentum conservation that are combined with one of three turbulence models Spalart-Allmaras, Realizable k-ε and k-ω shear stress transport (SST). It is observed that the Realizable k- ε eliminates the small separation bubble on the upper surface of the airfoil and delaying separation flow.  Also, for the lift coefficient, CL and drag coefficient, CD investigated in this paper, the predicted data have good agreement with other published data

Numerical Simulation in Transient Flow of Non-Newtonian Fluid in Nozzles

The rheological complexities of non-Newtonian fluids can lead to a variety of difficulties including most importantly changes in viscosity during packaging process. In order to give more understanding in this phenomena, the effect of temperature to the viscosity of chili sauce during packaging is investigated. This paper also presents the influence of three different shape of nozzles to the chili sauce flow behavior during filling time. A transient simulation has been conduct in this work using computational fluid dynamics (CFD) ANSYS CFX 15.0. It was found that viscosity is inversely proportional with temperature drop and time. The filling time also improved when using bigger conical angle of the nozzle. The results indicate the increased in production of the chilli sauce and improve packaging process

A mechanistic analysis of shell-side two-phase flow in an idealised in-line tube bundle

This paper reports on an experimental study of air–water mixtures flowing through an idealised shell and tube, in-line heat exchanger. Void fraction measurements are reported for the minimum gaps between the tubes at near atmospheric conditions. The pressure distributions around some tubes are also reported. These data are combined with data available in the open literature to investigate pressure drop and void fraction prediction methods for these heat exchangers. The data are shown to be flow pattern dependent. Criteria for flow pattern boundaries are deduced from previously published flow maps. Void fraction data in the maximum gap between the tubes are shown to be compatible with the drift flux model and to be different in magnitude to the minimum gap values, which are shown to result from acceleration phenomena in the gaps between the tubes. The pressure drop data are analysed through a one-dimensional model that incorporates separation and re-attachment phenomena. The frictional pres-sure drop is shown to depend on a liquid layer located on the upper portion of the tubes at low gas veloc-ity and on acceleration effects at high gas velocity

A mechanistic analysis of shell-side two-phase flow in an idealised in-line tube bundle

This paper reports on an experimental study of air–water mixtures flowing through an idealised shell and tube, in-line heat exchanger. Void fraction measurements are reported for the minimum gaps between the tubes at near atmospheric conditions. The pressure distributions around some tubes are also reported. These data are combined with data available in the open literature to investigate pressure drop and void fraction prediction methods for these heat exchangers. The data are shown to be flow pattern dependent. Criteria for flow pattern boundaries are deduced from previously published flow maps. Void fraction data in the maximum gap between the tubes are shown to be compatible with the drift flux model and to be different in magnitude to the minimum gap values, which are shown to result from acceleration phenomena in the gaps between the tubes. The pressure drop data are analysed through a one-dimensional model that incorporates separation and re-attachment phenomena. The frictional pressure drop is shown to depend on a liquid layer located on the upper portion of the tubes at low gas velocity and on acceleration effects at high gas velocity

Inter-Rater Reliability of the New Observational Method for Assessing an Exposure to Risk Factors Related to Work-Related Musculoskeletal Disorders (WMSDS)

The Entire Body Risk Assessment (ENBORA) method is a new observational method used to evaluate risk factors linked to Work-related Musculoskeletal Disorders (WMSDs). Hence, this study aims to verify the inter-rater reliability of the ENBORA method. 16 raters were involved in a one day ENBORA training session. All of the participants needed to assess three different tasks using the ENBORA paper checklist. The tasks involved were; lifting from pallet to conveyor for Task A, creels of wire onto spindles for Task B, and bottling line inspection for Task C. The Cohen’s Kappa (K) coefficient and percentage of agreement were calculated. As a result, the inter-rater reliability for Task A has a Cohen’s Kappa value (K) of 0.88, while Task B and Task C achieved K=0.91 which indicated very good agreement. This study found that trained practitioners can reliably use the ENBORA method to assess exposure to risk factors related to WMSDs

Inter-Rater Reliability of the New Observational Method for Assessing an Exposure to Risk Factors Related to Work-Related Musculoskeletal Disorders (WMSDS)

The Entire Body Risk Assessment (ENBORA) method is a new observational method used to evaluate risk factors linked to Work-related Musculoskeletal Disorders (WMSDs). Hence, this study aims to verify the inter-rater reliability of the ENBORA method. 16 raters were involved in a one day ENBORA training session. All of the participants needed to assess three different tasks using the ENBORA paper checklist. The tasks involved were; lifting from pallet to conveyor for Task A, creels of wire onto spindles for Task B, and bottling line inspection for Task C. The Cohen’s Kappa (K) coefficient and percentage of agreement were calculated. As a result, the inter-rater reliability for Task A has a Cohen’s Kappa value (K) of 0.88, while Task B and Task C achieved K=0.91 which indicated very good agreement. This study found that trained practitioners can reliably use the ENBORA method to assess exposure to risk factors related to WMSDs

Comparative analysis on flow over cylinder between commercial code and open source algorithm

The understanding of flow over cylinder is crucial especially in aerodynamic study.The present of vortices due to flow separation at the stagnation point of cylinder is differ with the changes of Reynolds number. This study aims to investigate the flow characteristics over cylinder with different Reynolds numbers. Computational modelling is used in predicting the flow characteristic of flow over cylinder. Two different software has been used: Code::Blocks as compiler and commercial code as a basis of comparison. Three different Reynolds number imposed in this study are 20,40 and 100 to compare the accuracy and speed of convergence. Validation has been made with the previous finding to benchmark the accuracy of the result. The parameters used in this study are velocity in x and y direction, Mach numbers, drag coefficient and pressure coefficient.A brief comparison between sequential and optimized configuration which includes multiple processors is also considered. Results show that the drag coefficient and pressure are highly dependent on Reynolds numbers. The commercial code is acknowledged to be providing better results than the applied source code. However, for the optimization issue in the future, the advancement of applied source code will obtain the similar result as compared to commercial code