KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 10 of 22

Some of the metrics are blocked by your
consent settings
Heat Transfer Analysis in a Channel Mounted with In-Line Downward-Facing and Staggered Downward-Facing Notched Baffles
(2025-09-01)
Phila, A.
;
Keaitnukul, W.
;
Kumar, M.
;
Pimsarn, M.
;
Chokphoemphun, S.
This study presents a comprehensive analysis of heat transfer enhancement, flow resistance, and thermal performance in rectangular channels equipped with three baffle configurations: conventional transverse baffles (TBs), in-line downward-facing notched baffles (IDF-NBs), and staggered downward-facing notched baffles (SDF-NBs). The influence of the pitch-to-baffle height ratio (P/e), ranging from 2.0 to 10, was examined across Reynolds numbers from 6000 to 24,000. Results indicate that a P/e ratio of 6.0 consistently yielded the highest Nusselt numbers across all configurations. While the TB configuration produced significant heat transfer at P/e= 6.0, it experienced a substantial friction penalty, with its best thermal enhancement factor (TEF = 1.168) observed at P/e = 8.0. The IDF-NB configuration achieved optimal performance at P/e = 6.0 with a TEF of 1.257, offering a better balance between heat transfer and flow resistance. The SDF-NB arrangement outperformed all other cases, delivering the highest Nusselt number (Nu = 116.9), TEF (1.362), and improved flow reattachment, primarily due to enhanced mixing from the staggered layout. These findings demonstrate that the staggered notched baffle configuration at P/e = 6.0 offers the most effective thermal performance enhancement among the configurations studied.
Some of the metrics are blocked by your
consent settings
Multi-Objective Optimization of Lightweight Inboard Bearing Design for High-Speed Railway Axle
(2024-06-03)
Nwe, T.
;
Tantrapiwat, A.
;
Pimsarn, M.
This research delves into the intricate balance between reducing axle weight and maintaining structural integrity in high-speed rail transportation. Focusing on the critical factor of weight reduction in high-speed axle design, the study employs finite element simulations and standard calculations to systematically explore inboard and outboard bearing wheelsets. Particularly noteworthy is the examination of inboard bearing axles, revealing advantages in mass reduction, deflection, and stress mitigation, with an 8% lower weight than outboard bearing axles. Utilizing multi-objective optimization, the research achieves a remarkable 4% reduction in mass and an associated 4% decrease in stress, resulting in a 12% mass reduction compared to traditional axles. The study also enhances fatigue resistance, demonstrated through radial fatigue reverse factor (FRF) analysis. With a detailed methodology involving ABAQUS modeling, Python scripting, and optimization using the Pointer algorithm in Isight, this research adeptly navigates the trade-off, significantly contributing to the advancement of railway transportation systems.
Some of the metrics are blocked by your
consent settings
Influence of bed height and drying temperature on shrimp drying characteristics using a fluidized-bed dryer
(2023-08-01)
Nanan, K.
;
Eiamsa-ard, S.
;
Chokphoemphun, S.
;
Kumar, Manoj
;
Pimsarn, M.
The aim of this work was to study shrimp drying in a fluidized-bed dryer to develop a process that performs better than traditional (sun dried) shrimp production. In these experiments, the influence of shrimp size (small, medium and large), bed height (h/D = 0.33, 0.66 and 1.0) and air temperature (60, 70 and 80 °C) on the drying rate were studied under a constant blower power. The experimental results showed that the moisture content of boiled shrimp decreased with an increased drying temperature due to the consequently higher temperature differential between the hot air and the shrimp. When the bed height (h/D) was reduced, shrimp moisture removal increased, but it also increased when shrimp size decreased. Moreover, the production rate of dried shrimp under a bed height h/D = 1.0 and drying temperature of 80 °C yielded the highest dried shrimp production rate of 4.83, 4.21 and 3.72 kg/h for small, medium and large shrimps, respectively.
Some of the metrics are blocked by your
consent settings
Performance of a heat exchanger with compound inclined circular-rings and twisted tapes
(2022-09-01)
Pimsarn, M.
;
Samruaisin, P.
;
Thianpong, C.
;
Ruengpayungsak, K.
;
Eiamsa-Ard, P.
Optimization was done of the aerothermal performance factor (η) of a tube into which a combination of inclined circular-rings (ICRs) and twisted-tapes (TTs) were installed. The key contribution of this research is determination of the appropriate ICR and TT sizes to produce the best heat exchanger performance. An ICR's purpose is to produce counter-rotating vortices, whereas the TT's role is to create swirl flow within a tube to improve turbulence and transfer cold fluid from the core region to the heated-wall zone. The influence of circular-ring inclination angle (α = 30o, 45o, 60o and 90o), number of twisted tapes (H = 2, 4, and 6) and twist ratios (TR = 1.0, 2.0, and 3.0) on heat transfer and pressure losses were assessed to determine an optimum η condition. The heat transfer and friction factor tend to increase with H values and decreasing TR. The heat transfer of ICRs together with TTs is higher than in a plain tube by up to 128.7% and 155.3%, respectively, while it is better than the transverse circular-ring (α = 90o) and twisted-tape by up to 116.9% and 146.5%, respectively. Furthermore, due to moderate heat transfer and low pressure losses, a maximal η of 1.66 was achieved for α = 30o, H = 2 and TR = 3.0 within the examined range.
Some of the metrics are blocked by your
consent settings
Effect of conical air distributors on drying of peppercorns in a fluidized bed dryer: Prediction using an artificial neural network
(2022-08-01)
Chuwattanakul, V.
;
Wongcharee, K.
;
Pimsarn, M.
;
Chokphoemphun, S.
;
Chamoli, S.
The effect of conical air distributors on the drying of peppercorns in a fluidized bed dryer was experimentally studied. A flat perforated sheet was installed in the column at the base of the bed. Conical air distributors consisted of two parts. The first was a solid cone located below an air duct, while the second part was a perforated metal cone placed on the flat perforated sheet. Experiments were carried out using perforated metal cones with three different height to base diameter ratios, (h/H) values of 0.5, 1.0, and 1.5 and three different air velocities, 1.2Umf, 1.6Umf, and 2.0Umf. An air distributor, consisting of a solid cone and a perforated metal cone with h/H = 1.0 and an air velocity of 2.0Umf, showed the best drying performance. It was also discovered that increasing the air velocity accelerated the drying process. A neural network was created to predict the moisture content of peppercorns during the drying process. The split, sample type, spilt ratio, momentum, and learning rate, as well as the numbers of hidden layers, hidden nodes, and training cycles all had an impact. A maximum coefficient of determination of 0.996 was found for the best model.
Some of the metrics are blocked by your
consent settings
Heat transfer characteristics of a swirling impinging air jet emerging from a triple spiral-corrugated nozzle with a twisted tape installed
(2022-07-01)
Eiamsa-ard, P.
;
Wongcharee, K.
;
Kunnarak, K.
;
Kumar, M.
;
Eiamsa-ard, S.
Thermal visualization using a thermochromic liquid crystal sheet was performed to investigate and compare heat transfer behavior of a swirling impinging jet emerging from a triple spiral-corrugated nozzle with a twisted tape (SIJ with TT), a SIJ issuing through a triple spiral-corrugated nozzle, and a typical/conventional impinging jet (CIJ) emerging from a smooth straight circular nozzle. The experimental results showed that the stronger jet recirculation close to the wall due to the swirl flow created by triple spiral-corrugated nozzle and twisted tape inserts (SIJ with TT) support in reducing the value of Nusselt number between the stagnation region and surroundings. For the SIJ with TT, the average Nusselt number performed by the jets with L/d<inf>H</inf> shows that the magnitude of the heat transfer coefficient was significantly enhanced with increasing twist ratios. The maximal value Nu of the SIJ with TT was obtained at the lowest twist ratio (y/W = 2.0). This was up to 5.7 % and 35.5 % higher than those of the SIJ with TT at y/W = 4.0, and the CIJ, respectively.
Some of the metrics are blocked by your
consent settings
Enhanced forced convection heat transfer of a heat exchanger tube utilizing serrated-ring turbulators
(2021-12-01)
Pimsarn, M.
;
Samruaisin, P.
;
Eiamsa-ard, P.
;
Koolnapadol, N.
;
Promthaisong, P.
Experiments were performed to study the thermohydraulic behaviors of heating tubes equipped with serrated-ring bundles as turbulators. Their thermohydraulic characteristics are reported in terms of Nusselt numbers (Nu) and friction factors (f) as well as performance in terms of a thermohydraulic performance index (TPI) at identical pumping power. Influences of serrated-ring diagonal angles (θ = 15°, 30°, 45° and 60°), pitch ratios (PR = 6.0, 8.0 and 12.0) and Re were examined. Various geometries of serrated-ring bundles can affect the laminar sub-layer disruption, creating a reversing flow, reconnecting the separated flow to the surface, and delaying the thermal/velocity boundary layer development. These are the most important mechanisms that lead to enhanced force convection heat transfer in a fluid flow. The heat transfer rate, friction loss and TPI increased with decreasing pitch ratio (PR) and serrated-ring diagonal angle (θ ). Heat transfer rate and friction factor were increased to 2.2 and 8.8 times that of a plain tube, respectively. Over the range investigated, the highest TPI, 1.16, was found using a serrated-ring bundle having θ = 15° and PR = 6.0 at Re = 4000.
Some of the metrics are blocked by your
consent settings
Influence of a double vortex chamber on temperature reduction in a counter-flow vortex tube
(2021-12-01)
Samruaisin, P.
;
Chuwattanakul, V.
;
Pimsarn, M.
;
Promthaisong, P.
;
Saysroy, A.
This article reports the effect of double vortex-chambers with multiple inlet snail entries of N = 1, 4 and 6 nozzles on the energy separation referred to cold gas exit temperature difference (ΔT<inf>c</inf>) in a counter-flow vortex tube type. The experimental work focused on ascertaining the effects of entry air pressure (P<inf>i</inf> = 2, 3 and 4 bar), distance ratios between the two vortex-chamber to the vortex tube diameter (l/D = 0.875–1.125) and the cold gas mass ratio (μ<inf>c</inf>) in a vortex tube. It was found that cold gas exit temperature difference (ΔT<inf>c</inf>) increased with increasing inlet air pressure (P<inf>i</inf>) and number of inlet nozzles (N), and decreasing l/D. Among the studied conditions, the double vortex-chamber operated at the highest P<inf>i</inf> of 4 bar, N = 6, the smallest l/D = 0.875 and μ<inf>c</inf> = 0.38 gave the highest cold gas exit temperature difference (ΔT<inf>c</inf>) of 31.5 °C. In addition, the deep learning optimization technique was also developed to predict the temperatures for different combination of parameters used in this study. It was found that the optimal models provide maximum R<sup>2</sup> value of 0.99317.
Some of the metrics are blocked by your
consent settings
Parametric study on thermal enhancement and flow characteristics in a heat exchanger tube installed with protruded baffle bundles
(2019-11-01)
Eiamsa-ard, S.
;
Ruengpayungsak, K.
;
Thianpong, C.
;
Pimsarn, M.
;
Chuwattanakul, V.
Influence of protruded baffle turbulators (P-BTs) on turbulent convective heat transfer rate and thermal performance behavior in round tubes was experimentally studied. The following geometrical parameters of P-BTs were considered (i) spacing ratio (SR = s/D<inf>ob</inf> = 1.0–3.0), (ii) diameter ratio (DR = d/D<inf>ob</inf> = 0.2–0.4), (iii) baffle orientation angle (θ = 0° (without rotation), 60°, 120° and 180°), and (iv) Reynolds number (Re = 6000 to 20,000). Air was used as working fluid at Prandtl number of Pr = 0.71. The plain tube data was examined for comparison with tube installed with protruded baffle turbulators (P-BTs). The experimental results obvious that increasing baffle orientation angle (θ), increasing diameter ratio (DR) and decreasing spacing ratio (SR) lead to the significant increases in heat transfer (Nu) and pressure loss (f). It can be also reveal that thermal performance (η) at a given Re considerably increases with the increasing spacing ratio (SR) and the reduction of diameter ratio (DR) and baffle orientation angle. The P-BTs with larger baffle orientation angle, induce stronger vortex ring and longitudinal vortex behind the baffles, give higher the thermal performance. Furthermore, all of empirical correlations (Nu, f and η) were derived as a function of Re and the protruded baffle turbulator (P-BT) geometry parameters including spacing ratio (SR), and protrusion-diameter ratio (DR).
Some of the metrics are blocked by your
consent settings
Influence of regularly spaced quadruple twisted tape elements on thermal enhancement characteristics
(2018-06-01)
Samruaisin, P.
;
Changcharoen, W.
;
Thianpong, C.
;
Chuwattanakul, V.
;
Pimsarn, M.
The present work explores the heat transfer, pressure loss and thermal enhancement factor (TEF) behaviors of a tube fitted with regularly spaced quadruple twisted tape elements (RS-QTTs). The effects of free space ratio and twisted tape arrangement (co, counter and cross arrangements) were investigated in turbulent flow regime. Experiments were carried out using all twisted tapes with constant twist ratio of 2.5 under constant heat flux condition. The results show that RS-QTTs in all arrangements yield lower heat transfer rate and cause lower friction loss than full-length quadruple twisted tapes (QTTs) due to the weaker swirling intensity caused by the decaying of swirling flow. Heat transfer rates given by the RS-QTTs with s/y of 0.5, 1.0, 1.5 and 2.0 are lower than those given by the QTTs by around 6.2%, 8.13%, 10.6% and 12.8%, respectively. For RS-QTTs, heat transfer rate, friction loss and TEF increase with decreasing s/y. Over the range reported, the RS-QTTs in cross-arrangement with s/y = 0.5 gives heat transfer rate up to 6.6% over than that of the QTTs and the maximum TEF of 1.27. Moreover, the flow and thermal behaviors were also numerically studied for a better understanding on heat transfer mechanism.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results