• Title/Summary/Keyword: Dimple plate

Search Result 35, Processing Time 0.027 seconds

A Numerical Study on Performance of Air-to-Air Plastic Plate Heat Exchanger

  • Chung, Min-Ho;Yoo, Seong-Yeon;Han, Kyu-Hyun;Yoon, Hong-Ik;Kang, Hyoung-Chul
    • International Journal of Air-Conditioning and Refrigeration
    • /
    • v.17 no.2
    • /
    • pp.52-60
    • /
    • 2009
  • The purpose of this research is to develop high efficiency plastic plate heat exchangers which can be substituted for conventional aluminum plate heat exchangers. Four simulation models of plastic plate heat exchangers are designed and simulated: that is, flat plate type, turbulent promoter type, corrugate type and dimple type heat exchanger. The flat plate type is designed as the reference model in order to evaluate how much thermal performance increases. The turbulent promoter type is fabricated with cylindrical-type vortex generators and rib-type turbulent promoters. The corrugate type is obtained from the conventional stainless steel compact heat exchangers, which are called the herringbone-type compact heat exchangers. The dimple type has a number of dimples on its surface. In this study, the flow and heat transfer characteristics of the plastic plate heat exchanger are investigated using numerical simulation and compared with experimental results. Numerical simulation is carried out using the FLUENT code. The flows are assumed as a three-dimensional, incompressible and turbulent model. The computational analysis and experimental results both show that the friction coefficient and Nu number is highest in the corrugate type. The tendency of numerical simulation results is in good agreement with that of the experimental results.

Calculation of a 2-D channel flow with a dimple (딤플이 존재하는 2차원 수로유동의 계산)

  • Choe, Seo-Won;Baek, Yeong-Ho;Kim, Du-Yeon;Gang, Ho-Cheol
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.21 no.1
    • /
    • pp.49-56
    • /
    • 1997
  • Heat-transfer enhancement is seeked through modifications of fin surface. Real life plate-fin heat exchangers have complex three-dimensional geometries. Fins can have arrays of dimples and are attached to rows of penetrating tubes. To isolate the effect of surface modification, we model the real flow by a two-dimensional channel flow with a dimple on one side. The flow is analysed by solving the incompressible Navier-Stokes equation by a finite volume method on a generalized boundary-fitted coordinate. Results show a trapped vortex inside the dimple for all cases computed. Local maximum of Nusselt number occurs near the downstream end of the dimple, due to such a vortex. Location of the vortex does not change with respect to the wall temperature change, but moved downstream when Reynolds number increases. This, together with the results that in all cases vortex core is somewhat downstream of the dimple center, suggests that the mean flow above continuously feeds the kinetic energy to the recirculating flow. Heat transfer enhancement and pressure losses are studied through analysing the relevant dimensionless parameters like, Nusselt number and friction factor. In all cases computed, dimpled channel flow experiences less pressure loss than two-dimensional Poiseuille flow.

A Numerical Study on the Flow and Heat Transfer Characteristics of Plastic Plate Heat Exchanger (플라스틱 판형 열교환기의 유동 및 열전달 특성에 관한 수치해석적 연구)

  • Chung, Min-Ho;Yoo, Seong-Yeon;Han, Kyu-Hyun;Yoon, Hong-Ik
    • Proceedings of the SAREK Conference
    • /
    • 2008.06a
    • /
    • pp.1366-1371
    • /
    • 2008
  • Four simulation models of plastic plate heat exchangers are designed and simulated. The flat plate type heat exchanger is designed as the reference model in order to evaluate how much thermal performance increases. The turbulence promoter type heat exchanger is fabricated with cylindrical-type vortex generators and rib-type turbulence promoters. The corrugate type is obtained from the conventional stainless steel compact heat exchangers, which are called the herringbone-type compact heat exchangers. The dimple type heat exchanger has a number of dimples on its surface. In this study, the flow and heat transfer characteristics of the plastic plate heat exchanger are investigated using numerical simulation and compared with experimental results. The flows are assumed as a three-dimensional, incompressible and turbulent model. The standard k-$\varepsilon$ model is used as the turbulent flow modeling, the SIMPLE algorithm is used to treat the coupling between pressure and velocity, and first order upwind scheme is used for discretization of momentum, turbulent and energy. The computational analysis and experimental results both show that the friction coefficient and Nu number is highest in the corrugate type.

  • PDF

Pressure drop and heat transfer characteristics of a flat-plate solar collector with heat transfer enhancement device (열전달 향상 장치에 따른 평판형 태양열 집열기의 압력강하 및 열전달 특성)

  • Ahn, Sung-Hoo;Shin, Jee-Young;Son, Young-Seok
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.37 no.5
    • /
    • pp.453-460
    • /
    • 2013
  • The surface roughness and heat transfer enhancement devices are known to increase the performance of a flat plate soar collector. This study includes the experiments on the effect of the several heat transfer enhancement devices inserted in duct to simulate the flat-plate solar collector. Experiment was basically at a constant heat flux on the upper duct wall. Inserted heat transfer enhancement devices are Chamfered rib $10^{\circ}$, Chamfered rib $20^{\circ}$, Rib & Groove and Rib & Dimple. Reynolds number is in the range of 2,300 to 22,000 which corresponds to turbulent regime. With the heat transfer enhancement devices, heat transfer would increase by the secondary flow and the increase of the heat transfer area. Pressure drop also increases with the insertion of the enhancement devices. Rib & Dimple model is the best in heat transfer enhancement, however, Chamfered rib $10^{\circ}$ model is the lowest in the pressure drop. Considering the heat transfer enhancement simultaneously with low pressure drop increase, performance factor was the best for the Chamfered rib $10^{\circ}$.

Study on the Drag Reduction of 2-D Dimpled-Plates (딤플을 적용한 평판에 대한 항력 감소 연구)

  • Paik, Bu-Geun;Pyun, Young-Sik;Kim, Jun-Hyung;Kim, Kyung-Youl;Kim, Ki-Sup;Jung, Chul-Min;Kim, Chan-Ki
    • Journal of the Society of Naval Architects of Korea
    • /
    • v.49 no.4
    • /
    • pp.333-339
    • /
    • 2012
  • The main objective of the present study is to investigate the roles of the micro-dimpled surface on the drag reduction. To investigate the effectiveness of the micro-dimpled surface, the flat plates are prepared. The micro-size dimples are directly carved on the metal surface by ultrasonic nano-crystal surface modification (UNSM) method. Momentum of the main flow is increased by the dimple patterns within the turbulent boundary layer (TBL), however, there is no significant change in the turbulence intensity in the TBL. The influence of dimple patterns is examined through the flow field survey near the flat plate trailing edge in terms of the profile drag. The wake flow velocities in the flat plate are measured by PIV technique. The maximum drag reduction rate is 4.6% at the Reynolds number of $10^6{\sim}10^7$. The dimples tend to increase the drag reduction rate consistently even at high Reynolds number range.

Heat Transfer and Pressure Drop Characteristics of Cross-Flow Plastic Air Heater for a Cooling Tower (냉각탑용 직교류형 플라스틱 공기가열기의 열전달 및 압력손실)

  • Kim, Nae-Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.14 no.12
    • /
    • pp.6072-6081
    • /
    • 2013
  • In this study, experiments were performed on air heater samples with three different shapes (chevron, wave and dimple type) to reduce the plumes from cooling towers. The tests were conducted for a range of frontal air velocities of 1~3 m/s and water flow rate 0.19~0.33 kg/s. The results showed that the heat transfer rate increased with increasing air velocity or water flow rate. The air-side pressure drop also increased with increasing air velocity. At the same frontal air velocity, the highest heat transfer rate was obtained for the chevron sample (1.5~1.7 times compared to that of the plate sample), followed by the dimple, wave and plate samples. The heat transfer rate per unit power consumption was also 15% larger than that of the dimple sample. On the other hand, there was no noticeable difference between the other samples.

Formulation of Optimal Design Parameters and Failure Map for Metallic Sandwich Plates with Inner Dimpled Shell Structure Subject to Bending Moment (굽힘 하중을 받는 딤플형 내부구조 금속 샌드위치 판재의 최적설계변수의 수식화 및 파손선도)

  • Seong Dae-Yong;Jung Chang-Gyun;Yoon Seok-Joon;Ahn Dong-Gyu;Yang Dong-Yol
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.23 no.8 s.185
    • /
    • pp.127-136
    • /
    • 2006
  • Metallic sandwich plates with inner dimpled shell subject to 3-point bending have been analyzed and then optimized for minimum weight. Inner dimpled shells can be easily fabricated by press or roll with high precision and bonded with same material skin sheets by resistance welding or adhesive bonding. Metallic sandwich plates with inner dimpled shell structure can be optimally designed for minimum weight subject to prescribed combination of bending and transverse shear loads. Fundamental findings for lightweight design are presented through constrained optimization. Failure responses of sandwich plates are predicted and formulated with an assumption of narrow sandwich beam theory. Failure is attributed to four kinds of mechanisms: face yielding, face buckling, dimple buckling and dimple collapse. Optimized shape of inner dimpled shell structure is a hemispherical shell to minimize weight without failure. It is demonstrated that bending stiffness of sandwich plate is 2 or 3 times larger than solid plates with the same strength. Failure mode boundaries and iso-strength lines dependent upon the geometry and yield strain of the material are plotted with respect to geometric parameters on the failure map. Because optimal parameters of maximum strength for given material weight can be selected from the map, analytic solutions for maximum strength are expressed as a function of only material property and proposed strength. These optimal parameters match well with numerical optimal parameters.

A Numerical Analysis of Flow and Heat Transfer in the Plate Heat Exchanger with Dimple (딤플형 판형 열교환기의 열유동 수치해석)

  • Ahn, Hyuk-Jin;Lee, Sang-Hyuk;Lee, Myung-Sung;Hur, Nahm-Keon
    • 한국전산유체공학회:학술대회논문집
    • /
    • 2008.03b
    • /
    • pp.121-125
    • /
    • 2008
  • In this study, the characteristics of internal flow and the heat transfer performance of dimpled plate heat exchanger were numerically investigated. For the numerical analysis, conjugate heat transfer method between cold fluid - plate - hot fluid was studied with appropriate boundary conditions. Velocity magnitude, temperature and pressure distribution were obtained from the simulation. Correlations for fanning f-factor and Colburn j-factor were obtained from numerical results and compared to the experimented data.

  • PDF