Chuwattanakul, Varesa

Preferred name

Alternative Name

Chuwattanakul, V.

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School of Engineering

varesa.ch@kmitl.ac.th

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Simulation of turbulent heat transfer characteristics in a corrugated tube with five-channel twisted tape inserts
(2017-08-31)
Promthaisong, Pitak
;
Jedsadaratanachai, Withada
;
Chuwattanakul, Varesa
;
Eiamsa-Ard, Smith
The article presents a numerical analysis of turbulent periodic flow and heat transfer characteristics in a five-start spiral corrugated tube combined with five-channel twisted tape. Influences of the five-channel twisted tape with tape width ratio, w/D=0.10, 0.20, 0.30, 0.40 and 0.44 at constant the twisted length ratio, y/D=2.0 were described. The results were reported in term of flow structure, temperature distribution, TKE field, local Nusselt number distribution on the wall, Nusselt number ratio, friction factor ratio and thermal enhancement factor. The five-start spiral corrugated tube combined with five-channel twisted tape showed a main swirl flow and secondary swirl flow along the tube due to the induction of the spiral groove while the smooth circular tube appeared the straight only and the five-start spiral corrugated tube with the five-channel twisted tape at w/D=0.44 appeared the main swirl flow only. The swirl flow help to increase fluid mixing and increase in heat transfer rate over the smooth circular tube. The increase in the w/D lead to the rise of Nusselt number and friction factor. The result showed that the optimum thermal enhancement factor of about 1.16was found at the five-start spiral corrugated tube without the five-channel twisted tape and at w/D=0.44.
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Influences of Spray Drying Conditions on the Physiochemical Properties of Karanda Fruit
(2023-01-01)
Chuwattanakul, Varesa
;
Yavirach, Koravit
;
Eiamsa-Ard, Smith
Karanda fruits are widely cultivated in Thailand. The fruit has several vitamins and minerals. One of the most fascinating possibilities is to transform it into a powdered drink. This study aimed to determine the optimal conditions for preparing karanda juice powder considering its physicochemical properties. Three levels of inlet air temperature were evaluated, 160 oC, 180 oC and 200 oC. Subsequently, three levels of maltodextrin (dextrose equivalent 10, DE10) were evaluated, 30%, 40%, and 50% by weight. Finally, three levels of whey protein (WPI) were evaluated, 5%, 10%, and 15% by weight. The moisture content dropped by 48.51% when the input air drying temperature rose from 160-200 °C. Yield increased by 15.08% and solubility by 5.06%. The maltodextrin content was increased from 30% to 50%, resulting in a 23.17% increase in product yield, while the WPI content was increased from 5% to 15%, leading in an 82.88% increase in anthocyanin content. SEM investigation indicated that the particle morphology was spherical with smooth surfaces, but an increase in inlet air temperature led to greater deformation and particle surface roughness. Additionally, the optimal parameters for spray drying karanda fruit were an inlet air temperature of 174 °C, maltodextrin (MD) content of 32%, and WPI content of 15% of soluble solids, with a product yield of 55.93±0.25%, solubility of 85.51±0.54%, and anthocyanin concentration of 12.58±0.36 mg/l.
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Rice husk combustion characteristics in a rectangular fluidized-bed combustor with triple pairs of chevron-shaped discrete ribbed walls
(2019-09-01)
Chokphoemphun, Suriya
;
Eiamsa-Ard, Smith
;
Promvonge, Pongjet
;
Chuwattanakul, Varesa
An experimental combustion work using the rice husk as a fuel was performed in a rectangular fluidized bed combustor with triple pairs of chevron-shaped discrete ribbed walls. The effect of percent excess air (EA = 40%-70%) on temperature distribution and gas emissions in a rectangular fluidized-bed combustor on combustion behaviors (temperature distributions inside the bed, exhaust gas emissions and combustion efficiency) is reported. The free-board had a rectangular shape which modified by increasing the chamber size from 300 × 100 mm2 to 600 × 200 mm2 or two times of the bottom chamber and 2400 mm in height. Triple pairs of rib configurations, namely, 30° chevron-shaped discrete ribbed walls were introduced and placed in the bottom part of the combustion chamber to generate counter-rotating vortices in the chamber. The results show that the fluidized bed combustor with 30° chevron-shaped discrete ribbed walls at 40% percent excess air provides the higher temperature than other of 861 °C. Among the studied excess air percentages, the highest combustion efficiency of 99.2% is obtained at EA = 60%. In addition, combustion at EA = 60% shows the lowest emissions CO, CO<inf>2</inf>, O<inf>2</inf> and NO<inf>x</inf> of 236.8%Vol, 2.55 ppm, 13.53 %Vol, 110.2 ppm, respectively.
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Effect of a TiO2/Water Nanofluid on the Thermal Cooling of a Central Processing Unit
(2024-01-01)
Nanan, Kwanchai
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Chuwattanakul, Varesa
;
Pramuanjaroenkij, Anchasa
;
Eiamsa-Ard, Smith
An investigation was conducted to evaluate the impact of TiO2/water nanofluids on the cooling system of a central processing unit (CPU). Tests were carried out using nanofluids with TiO2 concentrations of 0.02%, 0.05%, 0.1%, and 0.15% by volume at a Reynolds number of 20,000. Pure water (as the base fluid) was also tested for comparative analysis. The experimental findings emphasized the significant influence of nanofluid application on CPU cooling. Under identical operating conditions, the heat transfer rate of TiO2/water nanofluids proved more effective compared to pure water. Moreover, the results indicated that the nanofluid with a 0.05% volume concentration reduced CPU temperature by 1%, 0.7%, and 1.5% compared to TiO2 concentrations of 0.02%, 0.1%, and 0.15% by volume, respectively. At the optimal condition, the TiO2/water nanofluid with a volume concentration of 0.05% exhibited the highest Nusselt number, leading to a 2.4% decrease in CPU temperature compared to the base fluid.
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Effect of arc-shaped twisted-baffles on augmented heat transfer in a rectangular duct
(2023-02-01)
Promvonge, Pongjet
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Phila, Arnut
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Chuwattanakul, Varesa
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Chokphoemphun, Suriya
;
Eiamsa-Ard, Smith
In this current work, the effect of utilizing arc-shaped twisted-baffles (T-ABs) in a rectangular air channel on thermal performance factor (TPF) has been experimentally studied. In these experiments, the influence of the changes in parameters such as dimensions of pitch ratio (p/w), attached arc-shape angle (α), and Reynolds number (Re) are explored. The comparisons demonstrate that a channel mounted with arc-shaped twisted-baffles yielded considerably greater Nusselt numbers than a smooth channel, possibly attributable to multiple-impinging jets near the channel surface. Heat transfer enhancements of twisted arc-shaped baffles (T-AB) having larger attack angles were superior to those having smaller attack angles. The one with α = 90o offered greater heat transfer rates than the ones with α = 20o, 40o, 60o, and 80o by approximately 8%, 7%, 4%, and 2%, respectively. The superior heat transfer was attributed to the better contact between the working fluid and heat transfer surfaces. In addition, utilizing arc-shaped twisted-baffles with the lowest p/w of 4.0, in a channel produced stronger vortices and multiple impinging jets, which caused better fluid mixing than other p/w. The optimum condition is achieved using T-ABs at an attached arc-shape angle of α = 90o, p/w = 4.0 and Re = 4000, where the heat transfer rate (Nu), friction factor (f) and TPF are found to be, respectively, 3.31, 4.68 and 1.98 times greater than those of a plain channel.
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Impingement cooling by round jet with longitudinal swirling strip
(2018-03-01)
Kunnarak, Kengkla
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Somravysin, Prachya
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Eiamsa-Ard, Smith
;
Chuwattanakul, Varesa
The objective of this research is to study the effect of swirling impinging jet on the heat transfer in the impinged plated by using thermochromic liquid crystal (TLC) sheet. In the experiments, the nozzle having a diameter of 20 mm (D) was installed with four-channel twisted tape as a longitudinal swirling strip. The jet impingement was performed at jet-to-plate distances (L/D) of 2, 3, 4, 5, 6 and 7, and constant Reynolds number (Re) of 5000. The experimental results showed that the swirling jet induced by the four-channel twisted tape gave higher heat transfer rates than the conventional jet at the same operating conditions. The highest average heat transfer rate was obtained at the jet-to-plate distance (L/D) of 2.
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Influence of delta-winged dual twisted tapes insertion on heat transfer and pressure drop characteristics
(2015-01-01)
Samruaisin, Prachya
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Changcharoen, Wayo
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Chuwattanakul, Varesa
;
Eiamsa-Ard, Smith
The article presents the heat transfer and friction factor characteristics of turbulent flow in a uniform wall heat flux tube inserted with delta-winged dual twisted tapes. The typical dual twisted tapes (DTs) with constant twist ratio of y/W = 3.0 and delta-winged dual twisted tapes with delta-winged attack angle of α = 30° and β = 30° were carried out. Influences of the delta-winged arrangements in (1) the parallel direction (DT-PW) and (2) the counter direction (DT-CW) on the thermal performance characteristics were also described. The experimental results found that the use of the dual twisted tapes with parallel wing arrangements (DT-PW) provide the heat transfer higher than those the typical dual twisted tapes (DTs) and dual twisted tapes with counter wing arrangements (DT-CW) around 6.6-7.3% and 5.5-8%, respectively, due to stronger of dual-swirling/turbulent flow leading to better fluid mixing between the core and near tube walls while the friction factor is increasing up to 10.9 times above the plain tube. The typical dual twisted tapes (DTs), dual twisted tapes with parallel wing arrangements (DT-PW) and dual twisted tapes with counter wing arrangements (DT-CW) performs the highest thermal performance factor up to 1.2, 0.9 and 0.85 at Reynolds number of 6000.
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Heat transfer and fluid flow behaviors in a five-start spiral corrugated tube
(2017-08-31)
Promthaisong, Pitak
;
Jedsadaratanachai, Withada
;
Chuwattanakul, Varesa
;
Eiamsa-Ard, Smith
This paper presented a numerical investigation on turbulent periodic flow, heat transfer, pressure loss and thermal enhancement factor in a 3D five-start spiral corrugated tube. Air was used as the working fluids through the tube for Reynolds numbers of about 5000-20,000. In the current studied, the five-start spiral corrugated tube with six relative pitch ratios (p/D, PR=1.0, 1.5, 2.0, 2.5, 3.0 and 3.5) with constant depth ratio (e/D, DR=0.06). The numerical results reveal that the five-start spiral corrugated tube can generated a swirl flow, main swirl flow and five-secondary swirl flow. This behavior lead to the major change of temperature in transverse plane, reduced thermal layer thickness and enhanced heat transfer on the tube wall. The five-start spiral corrugated tube in range investigated provided the heat transfer rate and friction factor up to 2.02 and 6.12 times, respectively, over the straight circular tube. The thermal enhancement factor of the five-start spiral corrugated tube in the range of 0.89-1.16 where its maximum found as the optimum point is at PR=2.0.
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Heat transfer enhancement in turbular heat exchanger fitted with twin twisted tape swirl generators
(2017-08-31)
Saysroy, Anucha
;
Chuwattanakul, Varesa
;
Eiamsa-Ard, Smith
An experimental investigation was made with aim to enhance heat transfer in a double-tube heat exchanger fitted with twin twisted tapes. The effects of the twin twisted tape inserts on heat transfer rate, friction factor and thermal performance behaviors were studied in turbulent region of Reynolds number between 5000 and 15,000. The twin twisted tapes with three twist ratios (y/w = 1.5, 2.0 and 2.5) were used for generating two longitudinal swirl flows along the test section. The experimental result indicates that heat transfer rate in term of Nusselt number (Nu) and friction loss in term of friction factor (f) increase as twisted ratio (y/w) decreases. The twin twisted tapes with y/w = 1.5 yield higher Nusselt number (Nu) than the ones with y/w = 2.0 and 2.5 up to 16% and 38%, respectively which are accompanied with the higher friction factor up to 15% and 35%, respectively. Among the tested twisted tapes, the twin twisted tapes with the smallest twist ratio (y/w = 1.5) offer the maximum thermal performance factor of 1.64. In addition, the flow structure, temperature field, turbulent kinetic energy and local heat transfer coefficient in tube fitted twin twisted tapes are also presented.
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Temperature Distribution and Combustion Characteristics of Rice Husks in a Fluidized Bed Combustor
(2022-01-01)
Manop, Chalermchat
;
Wongcharee, Khwanchit
;
Chuwattanakul, Varesa
;
Promvonge, Pongjet
;
Saysroy, Anucha
This article presents an experimental study on the combustion characteristics of rice husks in a fluidized bed combustor (FBC). In the experiments, the FBC was tested with rice husk feeding rates ranging from 10-15.5 kg/hr to yield percent excess air (EA) between 25% and 35%. The axial and radial temperature distribution within the FBC was measured at a selected location while gas emissions were also monitored. From the experimental results, it can be seen that the maximum exhaust gas temperature is between 852 and 950 °C. In the exhaust gas emission analysis, CO is in the range of 951-1452 ppm, NO between 271 ppm and 303 ppm, CO<inf>2</inf> between 6.5% and 9.5%, and O<inf>2</inf> between 5.1% and 12.8%.

Chuwattanakul, Varesa

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