Sungai Buloh, Malaysia
Sungai Buloh, Malaysia

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Teh A.L.,Monash University | Chin K.W.,Monash University | Teh E.K.,Monash University | Chin W.M.,Oyl d nter Sdn Bhd | Foo J.J.,Monash University
Chemical Engineering Research and Design | Year: 2015

The downstream hydrodynamic and thermal mixing performance of control and fractal orifice plates is numerically investigated. Each insert is positioned following a T-duct. Four blockage ratio plates σ=0.5, namely, square orifice (SO), circular orifice (CO), square fractal orifice (SFO), and the Koch snowflake orifice (KSFO), are employed to promote thermal mixing. In particular, orifice configuration effects that induced transverse and horizontal thermal convergence, turbulence kinetic energy, and pressure gradient changes are discussed. Numerical validations reveal good agreement between the experimental and numerical results for centerline velocity and temperature distributions along the channel. The results show that KSFO outperforms the rest with respect to effective hydrodynamic and thermal mixing. It is critical to note that the maximum cross-sectional temperature difference δθ for KSFO is the lowest and decreases further downstream. Clearly, such low δθ values along the channel ensure temperature uniformity. Furthermore, KSFO generated area-averaged turbulence kinetic energy levels approximately 37%, 48%, 371%, and 1454% higher than those of CO, SO, SFO, and the smooth channel without an insert, respectively, at x/H=1.04. It is also important to note that the studied fractal orifice pressure gradients are lower than those of CO and SO. These pressure drop observations are consistent with those of Nicolleau et al. (2011). Overall, the complex KSFO geometry forms a prominent balance between the pressure coefficient and thermal mixing at a Reynolds number of Reh=1.94×104. Most importantly, this finding may help guide the long-term sustainable development of heating, ventilation and free-cooling air conditioning systems. © 2015 The Institution of Chemical Engineers.

Nordin N.,University Tun Hussein Onn Malaysia | Karim Z.A.A.,Petronas University of Technology | Othman S.,University Tun Hussein Onn Malaysia | Raghavan V.R.,Oyl d nter Sdn Bhd
Advanced Materials Research | Year: 2013

In practice, it is basically difficult even with controlled measurement environment to acquire a steady, uniform and fully developed flow. The flow entering diffuser was severely distorted despite a sufficient hydrodynamic entrance length already introduced. This was mainly due to the imperfect joining of duct and the abrupt change of the inlet cross-section applied. In this study, several basic features of a low subsonic wind tunnel, i.e. a centrifugal blower with 3-phase inverter, a settling chamber, screens and a contraction cone, are designed and developed for a turning diffuser application in order to improve the flow quality. The flow profiles are examined using Pitot static probe at five measurement points within the range of inflow Reynolds number, Rein= 5.786E+04-1.775E+05. The steady, uniform and fully developed turbulent flow profiles with an average deviation with theory of about 3.5% are obtained. This proves that a good flow quality could be produced by means of incorporating some basic features of a low subsonic wind tunnel to the system. © (2013) Trans Tech Publications, Switzerland.

Nordin N.,Petronas University of Technology | Nordin N.,University Tun Hussein Onn Malaysia | Abdul Karim Z.A.,Petronas University of Technology | Othman S.,University Tun Hussein Onn Malaysia | Raghavan V.R.,Oyl d nter Sdn Bhd
Applied Mechanics and Materials | Year: 2014

A turning diffuser is often introduced in the flow line to recover the energy losses by converting the kinetic energy to pressure energy. There are two types of turning diffusers, i.e. a 2-D and 3-D diffuser that are commonly defined by their expansion direction. This study aims to investigate the performance of a 2-D and a 3-D turning diffuser with 90° angle of turn and an area ratio, AR=2.16 by means of varying operating conditions. The geometry configurations applied for a 2-D turning diffuser are outlet-inlet configurations, W2/W12-D=2.160, X2/X12-D =1.000 and an inner wall length to an inlet throat width ratio, Lin/W12-D=4.370, whereas for a 3-D turning diffuser, they are W2/W13-D=1.440, X2/X13-D =1.500 and Lin/W13-D=3.970. The operating conditions represented by inflow Reynolds numbers, Rein are varied from 5.786E+04 to 1.775E+05. Particle image velocimetry (PIV) is used to examine the flow quality, and a digital manometer provides the average static pressure at the inlet and outlet of the turning diffuser. A compromise between the maximum permissible pressure recovery and flow uniformity is determined based upon the need. Whenever the flow uniformity being the need it is promising to apply a 3-D turning diffuser for Rein=1.027E+05 - 1.775E+05 and a 2-D turning diffuser for Rein=5.786E+04-6.382E+04. On the other hand, it is viable to opt for a 3-D turning diffuser for Rein=5.786E+04-6.382E+04 and a 2-D turning diffuser for Rein=1.027E+05-1.775E+05 in the case of the outlet pressure recovery being the need. The secondary flow separation takes place prior at 1/2Lin/W1 for a 2-D turning diffuser, whereas approximately at 3/4Lin/W1 for a 3-D turning diffuser. © (2014) Trans Tech Publications, Switzerland.

Nordin N.,University Tun Hussein Onn Malaysia | Abdul Karim Z.A.,Petronas University of Technology | Othman S.,University Tun Hussein Onn Malaysia | Raghavan V.R.,Oyl d nter Sdn Bhd
Applied Mechanics and Materials | Year: 2014

3-D stereoscopic PIV is capable of measuring 3-dimensional velocity components. It involves a very sophisticated routine during setup, calibration, measurement and data processing phases. This paper aims to verify the 3-D stereoscopic PIV measurement procedures and to prove that the flow entering the diffuser is a fully developed flow. A diffuser inlet of rectangular crosssection, 130 mm x 50 mm is presently considered. For verification, the velocities from PIV are compared with the velocities from pitot static probe and theory. The mean velocity obtained using pitot static probe is 2.44 m/s, whereas using PIV is 2.46 m/s. It thus gives the discrepancy of 0.8%. There is also a good agreement between the mean velocity measured by PIV and theoretical value with the discrepancy of 1.2%. This minor discrepancy is mainly due to uncertainties in the experiments such as imperfect matching of coordinates between the probe and laser sheet, unsteadiness of flow, variation in density and less precision in calibration. Basically, the operating procedures of 3-D stereoscopic PIV have successfully been verified. Nevertheless, the flow entering diffuser is not perfectly developed due to the imperfect joining duct and the abrupt change of inlet cross-section introduced. Therefore, improvement to the existing rig is proposed by means of installing settling chamber with multiple screens arrangement and contraction cone. © (2014) Trans Tech Publications, Switzerland.

Nordin N.,University Tun Hussein Onn Malaysia | Raghavan V.R.,Oyl d nter Sdn Bhd | Othman S.,University Tun Hussein Onn Malaysia | Karim Z.A.A.,Petronas University of Technology
ARPN Journal of Engineering and Applied Sciences | Year: 2012

Combined turning and diffusing is often associated with detrimental flow phenomena that contribute to losses induced by the very nature of its geometry. This paper aims to investigate the compatibility of using 3-D turning diffusers in improving pressure recovery and flow uniformity by means of varying area ratios (AR) and outlet-inlet configurations (W 2/W 1, X 2/X 1). There were three cases considered; (i) Case-A (reference): 2-D turning diffuser (AR=2.0, W 2/W 1=2.0, X 2/X 1=1.0), (ii) Case-B: 3-D turning diffuser (AR=2.0, W 2/W 1=1.5, X 2/X 1=1.3) and (iii) Case-C: 3-D turning diffuser (AR=4.0 W 2/W 1=1.5 and X 2/X 1=2.7). Inflow Reynolds Number (Re) approximately of 20 was applied. The experimental rig was set up with the diffuser models fabricated using acrylic. Particle Image Velocimetry (PIV) was used to acquire the velocity profile and visualize the flow structure in the diffusers. Digital manometer with resolution of 0.1Pa provided pressure values. Results show pressure recovery (C p) of respectively 0.3, 0.1 and 0.5 gained for Case A, B and C. In terms of flow uniformity, standard deviations (σ u) of 2.04E-03, 3.14E-03 and 2.57E-03 were recorded, respectively. There was a reduction in terms of recovery and uniformity when a 3D turning diffuser with an AR=2.0 was introduced. Whereas, the compatibility of 3-D turning diffuser with an AR=4.0 seems more promising. The results obtained in this study will be used to validate the CFD codes. The intensive CFD simulation by means of varying other geometry configurations in the event of different inflow Reynolds number will be carried out in future. © 2006-2012 Asian Research Publishing Network (ARPN).

Yet N.M.,Petronas University of Technology | Raghavan V.R.,Petronas University of Technology | Chinc W.M.,Oyl d nter Sdn Bhd
AIP Conference Proceedings | Year: 2012

The cross flow fan is a unique type of turbo machinery where the air stream flows transversely across the impeller, passing the blades twice. Due to its complex geometry, and highly turbulent and unsteady air-flow, a numerical method is used in this work to conduct the characterization study on the performance of a cross flow fan. A 2D cross-sectional model of a typical indoor air conditioning unit has been chosen for the simulation instead of a three dimensional 3D model due to the highly complex geometry of the fan. The simplified 2D model has been validated with experiments where it is found that the RMS error between the simulation and experimental results is less than 7%. The important parameters that affect the cross flow fan performance, i.e. the internal and external blade angles, the blade thickness, and the casing design, are analyzed in this study. The formation of an eccentric vortex is observed within the impeller. © 2012 American Institute of Physics.

Seth N.N.,University Tun Hussein Onn Malaysia | Mat Isa N.B.,University Tun Hussein Onn Malaysia | Othman S.B.,University Tun Hussein Onn Malaysia | Raghavan V.R.,Oyl d nter Sdn Bhd
ARPN Journal of Engineering and Applied Sciences | Year: 2016

The aim of installing baffles is to reduce or eliminate, if possible, secondary flow which exists mostly at the inner wall of the turning diffuser. Furthermore, other than distortion at the inner wall, 3-dimensional turning diffuser has secondary flow at both left and right wall. This was due to the diffusing activities which were not only in x-y direction but in y-z direction as well. Experiment on 3-dimensional turning diffuser with baffle has been conducted using airfoil baffle with AOA=17°. Present study focuses on changing angle of attack of the installed baffle and their effects on flow uniformity and pressure recovery using numerical approach. The baffle was rotated 3° clockwise and anti-clockwise resulting in AOA=20° and AOA=14° respectively. Qualitative and quantitative comparison was discussed in this paper. AOA=14° offers higher quality of flow structure as compared to AOA= 20°, but still could not surpass the performance using preliminary design baffle with AOA= 17°. The abnormality of flow in AOA=20° resulting in higher pressure loss, thus affecting pressure recovery. The optimum configuration can be developed if the effort of improving the airfoil design could be enhance in future works. © 2006-2016 Asian Research Publishing Network (ARPN). All rights reserved.

Tang S.H.,University Putra Malaysia | Chng M.H.,University Putra Malaysia | Chng M.H.,Oyl d nter Sdn Bhd | Chin W.M.,Oyl d nter Sdn Bhd
International Journal of Automotive and Mechanical Engineering | Year: 2014

In recent years, conservation of energy has become a challenging issue in air-conditioning applications. In order to overcome this issue, many researchers have recommended the use of a Parallel Flow Condenser and a low Global Warming Potential and Ozone Depletion Potential refrigerant, such as R32, in air conditioning systems. However, PFC faces the critical challenge of flow maldistribution in the tubes. This literature review mainly examines the refrigerant maldistribution problem which has been investigated by previous researchers. It was found that many of the researchers did not properly analyse the influence of flow maldistribution profiles on the performance degradation of heat exchangers. In order to have a comprehensive analysis of tube-side maldistribution in Parallel Flow microchannel heat exchangers, it is recommended that the influence of the higher statistical moments of the probability density function of the flow maldistribution profiles on performance degradation be quantified. Additionally, R32 maldistribution should be analysed and compared with R410A, which is the current commonly used refrigerant in air conditioning units. Moreover, in order to have a realistic simulation of the effect of refrigerant flow maldistribution profiles on performance degradation of heat exchangers, the effect of superheat and sub-cooling must be analysed. © Universiti Malaysia Pahang.

Nohseth N.H.,University Tun Hussein Onn Malaysia | Nordin N.,University Tun Hussein Onn Malaysia | Othman S.,University Tun Hussein Onn Malaysia | Raghavan V.R.,Oyl d nter Sdn Bhd
Applied Mechanics and Materials | Year: 2014

Turning diffuser is an engineering device that is widely used in the industry to reduce the flow velocity as well as change the direction of the flow. Having a curvature shape causes its performance to decrease in terms of pressure recovery (Cp) and flow uniformity (σu). Therefore, this study presents the work done in designing baffles to be installed in the turning diffuser with ratio of AR=2.16 to improve the flow uniformity and pressure recovery. It also aims to investigate the mechanism of flow structure and pressure recovery in turning diffusers by means of turning baffles. The results with varying inflow Reynolds number (Rein) between 5.786E+04 - 1.775E+05 have been experimentally tested and compared with previous study. Particle image velocimetry (PIV) was used to determine the flow uniformity. On the other hand, a digital manometer provided the average static pressure of the inlet and outlet of turning diffuser. The best produced pressure recovery of Cp=0.526 were recorded when the system were operated at the highest Reynolds number tested Rein=1.775E+05. This result shows an improvement up to 54.625% deviation from previous study with Cp=0.239. The flow uniformity also shows an improvement of 47.127% deviation from previous study at the same Rein with σu=3.235 as compared to previous study σu=6.12. © (2014) Trans Tech Publications, Switzerland.

Seri S.M.,Petronas | Abdul Karim Z.A.,Petronas | Batcha M.F.M.,University Tun Hussein Onn Malaysia | Raghavan V.R.,Oyl d nter Sdn Bhd
Applied Mechanics and Materials | Year: 2014

Present study involves experimental and numerical work to investigate the effect of integral wake splitter towards the overall performance of cross-flow, circular tube, heat exchanger system. The experimental work was conducted to obtain local distribution of pressure coefficient around plain tube bank of staggered arrangement which was subjected to a cross-flow of air with Reynolds number of 15950. The numerical work consisted of 2-dimensional unsteady numerical simulation which was validated against the experimental data. The validated numerical approach was utilized to simulate cross-flow around similar tube bank but with integral wake splitter of length-to-diameter ratio of 0.5, 1, 1.5 and 2, at Reynolds number between 5000 to 50000. It is concluded that integral wake splitter is able to reduce pressure loss, which in turn reduces power requirement of a blower, which is intended in effort to increase the system efficiency. Splitter which acts as fin may improve the overall performance of the system by enhancing total heat removal via extended surface provided that certain value of fin efficiency is achieved. © (2014) Trans Tech Publications, Switzerland.

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