• Journal of the Korean Solar Energy Society
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• v.39 no.6
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• pp.83-91
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• 2019

Photovoltaic thermal (PVT) collectors are devices that simultaneously produce electricity and heat. Research on conventional air-type PVT collector focuses on installing baffles to enhance the collector's thermal performance. However, the baffles have pressure drop inside the collector which degrades the thermal performance. Thus, it is necessary to design baffles to smoothen the flow inside the air-type PVT collector. Alternatively, installing perforated baffles in air-type PVT collectors can reduce the collector weight, but parameters such as the diameter of the perforated holes and the height of the perforated plates should be considered. Therefore, the main aim of this study was to analyze thermal characteristics of each variable of perforated baffles installed inside air-type PVT collector. For this purpose, the uniformity of air flow in the collector was compared through NX program, and the resultant heat gain and thermal efficiency of the air-type PVT collector were compared and analyzed. Therefore, the main aim of this study was to analyze thermal characteristics of each variable (Baffle angle, length, height, pitch, perforated ratio) of perforated baffles installed inside air-type PVT collector. For this purpose, the uniformity of air flow in the collector was compared through CFD program, and the resultant heat gain and thermal efficiency of the air-type PVT collector were compared and analyzed. As a result, the maximum outlet temperature was increased by 1.45 times and the heat gain was increased by 193.8 Wth, depending on the perforated baffle plate, compared to the collector without the baffle. The heat transfer performance showed that the maximum internal velocity was 1.61 times higher and the Reynolds number was 1.06 times higher depending on the parameters of the baffle plate.

• International Journal of Air-Conditioning and Refrigeration
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• v.16 no.2
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• pp.70-76
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• 2008

The effects of the inclined perforated baffles on the distributions of the local heat transfer coefficients and friction factors for air flows in a rectangular channel were determined for Reynolds numbers from 23,000 to 57,000. Four different types of the baffle are used. The inclined baffles have the width of 19.8cm, the square diamond type hole having one side length of 2.55cm, and the inclination angle of $5^{\circ}$, whereas the corresponding channel width-to-height ratio was 4.95. Results show that the heat transfer and friction factor depend significantly on the number of baffle holes and Reynolds number. The friction factor decreases with increasing Reynolds number and the number of holes on the baffle, and the heat transfer performance of baffle type II (3 hole baffle) has the best value.

• Korean Chemical Engineering Research
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• v.62 no.2
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• pp.191-199
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• 2024

A study was conducted on a tubular heat exchanger to improve its heat transfer rate by using a novel baffle plate design with discontinuous swirling patterns. The design consisted of perforated baffle plates with rectangular air deflectors positioned at varying angles. The tubes in the heat exchanger were arranged in a consistent alignment with the airflow direction and exposed to a uniform heat flux on their surfaces. Each baffle plate included sixteen deflectors inclined at the same angle and arranged in a clockwise pattern. This arrangement induced a swirling motion of the air inside a circular duct where the heated tubes were located, leading to increased turbulence and improved heat transfer on the tube surfaces. The spacing between the baffle plates was adjusted at different pitch ratios, and the Reynolds number was controlled within a range of 16,000 to 29,000. The effects of pitch ratios and inclination angles on the heat exchanger's performance were analyzed. The results indicated that using a baffle plate with rectangular deflectors inclined at 30° and a pitch ratio of 1.2 resulted in an average increase of 1.29 in the thermal enhancement factor.

• Journal of computational fluids engineering
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• v.9 no.2
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• pp.11-17
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• 2004

CFD analysis was performed to figure out flow behavior in the inlet plenum of new research reactor where coolant is injected to the flow tubes with the fuel assembly. The computation results showed that large-scale vortices are generated in the inlet plenum by flow stream injected from inlet pipe. These vortices are divided into small vortices and reversed their revolution. They may lead to flow-induced vibration of fuel assembly, moreover, which has been regarded as a cause of fretting wear of fuel assembly. Also there is an another important thing that average velocity of each flow-tube is uneven showing difference in maximum 18%. So it has been suggested that perforated baffle will be installed to prevent the formation of vortex in the inlet plenum. Two perforated baffles, one is flow skirt and the other is muffler type flow straightener, were proposed and their effect was evaluated using commercial CFD code, Fluent. According to CFD analysis for two perforated baffles, it was confirmed that both of them can prevent or reduce vortex formation in the inlet plenum and make average velocity of each flow tube more even.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.7
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• pp.1003-1012
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• 2008

A three dimensional numerical study has been applied to predict the turbulent fluid flow and heat transfer characteristics for the rectangular channel with different types of baffles. Four different types of the baffles are used. The inclined baffles have the width of 19.8 cm, the square diamond type hole having one side length of 2.55 cm, and the inclination angle of $5^{\circ}$. Reynolds number is varied between 23,000 and 57,000. The SST k-${\omega}$ turbulence model is used in the present numerical study. The validity of the numerical results is examined with the experimental data. The numerical results of the flow field depict that the flow patterns around the different baffle type are entirely different and it significantly affects the local heat transfer characteristics. The heat transfer and friction factor depend significantly on the number of baffle holes. It is found that the heat transfer enhancement of baffle type II (3 hole baffle) has the best values.

• Journal of Power System Engineering
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• v.12 no.3
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• pp.26-31
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• 2008

This experimental study investigates the local heat transfer enhancement characteristics and the associated frictional head loss in the rectangular channel with a single inclined baffle. Four different types of the baffle are used. The inclined baffles have the width of 19.8 cm, the square diamond of $2.55cm{\times}2.55cm$, and the inclination angle of 5o, and number of holes of up to 9. Reynolds number is varied between 23,000 and 57,000. Results show that the heat transfer and friction factor depend significantly on the number of baffle holes and Reynolds number. The friction factor decreases with increasing Reynolds number and the number of holes on the baffle. It is found that the heat transfer performance of baffle type II(3 hole baffle) has the best values.

• Journal of the Korean Society of Combustion
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• v.14 no.4
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• pp.7-16
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• 2009

Porous metal plates (Metal fiber, muti-hole metal plate) using mainly in surface burner are known to have a corrosion and durability problem under high temperature condition. In this study, premixed flat flame with perforated ceramic tile of more durable cordierite material was examined with respect to combustion stability and emission. The flat premixed ceramic burner consists of perforated ceramic tile and various type of baffle plates to form stable surface flame. The results show that most stable flat flame is generated using baffle plate with open ratio of 0.193. In downward flat flame mode which is widely used in condensing boiler, CO is measured below 50ppm from equivalence ratio 0.755 to 0.765 and $NO_X$ is measured below 12ppm from equivalence ratio 0.75 to 0.79. It is also found that the range of blue flame in flame stability curve becomes wider with increasing heat capacity.

• Journal of Power System Engineering
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• v.12 no.4
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• pp.39-45
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• 2008

본 연구는 두 개의 경사진 다공 배플이 설치된 사각채널에서 국부 열전달향상 특성을 조사하였다. 채널은 19.8cm(W)$\times$4cm(H)의 단면적을 가지며 형상계수는 4.95이며 수력직경은 6.66cm이다. 4종류의 배플을 취급하였다. 가열 시험부에 동일한 크기, 경사각, 구멍형태의 경사 배플을 설치하였다. 경사 배플은 모두 19.8 cm의 폭, $2.55cm\times2.55cm$의 정 다이아몬드 형 구멍, 그리고 So의 경사각을 갖는다. 레이놀즈 수 범위는 23,000에서 57,000까지이다. 배플의 구멍의 수가 열전달 향상에 중요한 역할을 하였으며 구멍이 3개 인(baffle type II)가 가장 우수한 열전달 향상을 보였다.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.4
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• pp.427-436
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• 2004

Sedimentation is one of the most common and important units in conventional water treatment plants. Structure such as various baffle walls and inclined plate settler may be obstacles to the horizontal flow when it is poorly designed. Therefore, the effects of these structures on characteristics of hydraulic flow must be evaluated to improve the settling efficiency of the floc. The hydraulic characteristic of the four sedimentations at the three real WTPs (water treatment plants), which have different structural properties respectively inside the settling basin, were investigated by tracer (fluoride) test. The inclined plate settler installed inside settling basin caused a undesirable impact on horizontal flow and produced dead zone. Intermediate baffle and solid baffle wall under the inclined plate settler at GE plant help to minimize the formation of density currents and flow short circuiting. However, installing perforated baffle under the inclined plate settler at other plants could not induce even distribution of flow. NaF used as a tracer was recovered more than 90% at investigated all basin. Morill index ($t_{90}/t_{10}$), Modal index ($t_p/T-HRT$) and short-circuiting index ($[M-HRT-t_p/M-HRT$) were determined from tracer test results performed at three WTPs. Those indices ranged 2.99~3.45, 0.44~0.72 and 0.23~0.47, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.8
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• pp.855-860
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• 2011

We numerically simulated a dissolved air flotation (DAF) tank to predict the performance of the pilot facility. The flow was assumed to be two-dimensional and two-phase. The velocity distributions in the separation zones of differently shaped DAFs were compared to find the effect of the shape on the performance. The results showed that the typical flow pattern that appeared in a well-designed DAF-tank was generated in the separation zone of the base model. This flow pattern could be maintained while the baffle height was sufficiently tall regardless of the other geometric parameters. However, the baffle height and angle, the contact zone width, and the perforated plate affected the uniformity of the downward flow in the separation zone. Except for the baffle height, the base model used in this study showed a better uniformity of downward flow than did other models with different geometric parameters.