Showing papers on "Fin (extended surface) published in 2006"
01 Jan 2006
TL;DR: In this paper, the authors propose to increase the surface area by increasing the fluid flow over the surface since h is a function of the flow velocity, and the higher the velocity, the higher h.
Abstract: • Increase the temperature difference (Ts-T) between the surface and the fluid. • Increase the convection coefficient h. This can be accomplished by increasing the fluid flow over the surface since h is a function of the flow velocity and the higher the velocity, the higher the h. Example: a cooling fan. • Increase the contact surface area A. Example: a heat sink with fins. Many times, when the first option is not in our control and the second option (i.e. increasing h) is already stretched to its limit, we are left with the only alternative of increasing the effective surface area by using fins or extended surfaces. Fins are protrusions from the base surface into the cooling fluid, so that the extra surface of the protrusions is also in contact with the fluid. Most of you have encountered cooling fins on air-cooled engines (motorcycles, portable generators, etc.), electronic equipment (CPUs), automobile radiators, air conditioning equipment (condensers) and elsewhere.
189 citations
TL;DR: In this paper, modern nonintrusive techniques are used to make skin-friction and heat transfer measurements in two shockwave/turbulent boundary-layer interactions (SWTBLIs).
Abstract: Modern nonintrusive techniques are used to make skin-friction and heat transfer measurements in two shockwave/turbulent boundary-layer interactions (SWTBLIs). The two-dimensional SWTBLI is generated by impingement of an incident oblique shock wave on a flat-plate boundary layer. The three-dimensional SWTBLI results from the interaction of the swept shock generated by a fin with a flat-plate boundary layer. The measurements are made using the global interferometry skin-friction technique for the skin friction and the quantitative infrared thermography technique for the heat transfer rate. The results show that, for the two- and three-dimensional interactions, there is a clear difference in the behavior of skin friction and heat transfer as the strength of the shock is changed. This observation suggests that the analogy between momentum and heat transfer, which is the basis of many simplified physical models, is not valid in SWTBLIs. These new data supplement the previous measurements that include boundary-layer properties, surface pressure distributions, and patterns of the limiting streamlines. Taken together, these data complete a data set that is suited for computational fluid dynamics validation.
181 citations
TL;DR: In this paper, the thermal-hydraulic performance under conditions of an initial frost growth on the air-side surface, and for subsequent "refrosting" after a defrost period is experimentally studied for folded-louvered-fin, microchannel heat exchangers.
Abstract: The thermal-hydraulic performance under conditions of an initial frost growth on the air-side surface, and for subsequent ‘refrosting’ after a defrost period is experimentally studied for folded-louvered-fin, microchannel heat exchangers In total, five heat exchangers are considered; the thermal performances during one frost-growth cycle for four different fin geometries are compared in terms of overall heat transfer coefficient, pressure drop, and j and f factors; the defrost and refrost characteristics of two heat exchangers are compared to explore geometry effects Typically, the performance under refrosting conditions becomes periodic and repeatable after the third or fourth refrosting cycle The allowable frost growth period (before a defrost is required), the defrost requirement, and the thermal-hydraulic performance depend on heat exchanger geometry for the specimens used in this study
128 citations
TL;DR: Ferrouillat et al. as mentioned in this paper studied the potential of using a compact heat exchanger as a mixer as well as a chemical reactor, generally referred to as multifunctional heat exchangers (MHE).
126 citations
TL;DR: In this article, a mathematical model is proposed to evaluate the frosting behavior of a fin-tube heat exchanger under frosting conditions, which is validated by comparing the numerical results with experimental data for the frost thickness, frost accumulation, and heat transfer rate.
92 citations
TL;DR: In this article, the effect of the number of mesh layers and amount of working fluid on the heat transfer performance of copper-water heat pipes with screen mesh wicks was investigated.
82 citations
TL;DR: In this article, the authors proposed a new reduction method to calculate the heat and mass transfer characteristics of the wavy fin-and-tube heat exchangers under dehumidifying conditions.
81 citations
TL;DR: In this paper, an engineering model is formulated to account for the effects of porosity and pore diameter on the hydrodynamic and thermal performance of a carbon-foam finned tube heat exchanger.
79 citations
TL;DR: In this article, a computational analysis of the heat transfer due to an array of distributed heat sources on the bottom wall of a horizontal enclosure is presented, where the heat sources are modeled as flush-mounted sources with prescribed heat flux boundary conditions.
Abstract: Presented in this article is a computational analysis of the heat transfer due to an array of distributed heat sources on the bottom wall of a horizontal enclosure. The heat sources are modeled as flush-mounted sources with prescribed heat flux boundary conditions. Optimum heat transfer rates and the onset of thermal instability triggering various regimes are found to be governed by the length and spacing of the sources and the width-to-height aspect ratio of the enclosure. With respect to source spacing, we found that spacing equal to that of the source length provides effective convective heat transfer, and increasing the source spacing further does not result in significant improvements. The transition from a conduction-dominated regime to a convection-dominated regime is found to be characterized by a range of Rayleigh numbers, in contrast to the classical bottom wall heating problem. The range of Rayleigh numbers at which transition takes place decreases as the source length increases. At th...
72 citations
TL;DR: In this article, the authors proposed an optimization method for a fin-tube heat exchanger of a household refrigerator under frosting conditions to improve its thermal performance and extend its operating time.
72 citations
TL;DR: In this article, a general distributed model with frost formation was developed, which is able to predict the dynamic behavior of an air cooler both under non-frost and frost condition.
TL;DR: In this article, the average heat transfer coefficient and the fin efficiency on a vertical square fin of one-circular tube plate finned-tube heat exchangers are simultaneously taken into consideration.
TL;DR: In this paper, the basic convective and evaporative processes that produce heat transfer enhancement in nucleate pool boiling were investigated. But the results of the experiments were limited to the area around the circumference of the horizontal test tube with and without macro cavities for enhancement.
TL;DR: In this paper, the authors studied the natural convection heat transfer optimization through genetic algorithms and confirmed the methodology as computationally feasible for the optimal location of heat sources in a vertical wall.
Patent•
27 Jun 2006TL;DR: In this article, a heat sink for a power module can be mounted with a power device (101) at least on one plane, where a cooling medium communicates to dissipate heat from the power device and a corrugated fin is arranged in the cooling medium flow path.
Abstract: A heat sink (1) for a power module can be mounted with a power device (101) at least on one plane. The heat sink (1) is provided with a cooling medium flow path (1d) wherein a cooling medium communicates to dissipate heat from the power device (101), and a corrugated fin (1a) arranged in the cooling medium flow path (1d). The corrugated fin (1a) is provided with ridges (21b) and furrows (21c) extending in a communication direction of the cooling medium, and side walls (21a) connecting the adjacent ridges (21b) and the furrows (21c). A fin section (21) is composed of the two adjacent side walls (21a), and the ridge (21b) or the furrow (21c) positioned between the both side walls (21a). Each side wall (21a) is provided with a louver (31) which at least operates to turn the cooling medium communicating inside a corresponding fin section (21). Heat dissipating performance can be further improved by the heat sink (1).
TL;DR: In this article, successively increased or decreased louver angle patterns are proposed and 3-D numerical analysis on heat and fluid flow are carried out, which indicated the successively variable louver angles applied in heat exchangers could effectively enhance the heat transfer performance.
TL;DR: In this article, a generic model of an endoreversible engine is developed for studying the effect of convective heat transfer, the rate of which depends on the temperature difference to the power n where n is close to unity.
Abstract: A generic model of an endoreversible engine is developed for studying the effect of convective heat transfer, the rate of which depends on the temperature difference to the power n where n is close to unity. The efficiency at maximum power production is found to have as its principal part the Curzon-Ahlborn [Am. J. Phys. 43, 22 (1975)] expression and a small correction which depends slightly on the temperature ratio of the heat engine reservoirs and the relative heat conductances to the hot and cold sides. By a proper choice of the independent variables it is demonstrated that the analysis becomes simple and approximate analytical expressions are easily derived.
TL;DR: In this article, a 20 times scaled model of an idealized louvered fin exchanger with a fin pitch to louver pitch ratio of 0.76 and a louver angle of 27° was presented.
TL;DR: In this article, the authors presented an algorithm model for estimating the heat transfer by forced convection of the porous heat sink in a channel by applying the fin theory and the concept of the thermal network.
TL;DR: In this article, the authors used the Adomian decomposition method to evaluate the efficiency of a radiating rectangular fin with variable thermal conductivity, and then they used the correlation equations to find the optimum dimensions of space radiators which maximize the heat transfer rate per unit radiator mass.
TL;DR: In this article, the effects of Reynolds and Grashof numbers on these numbers were investigated and the effect of the buoyancy affected secondary flow and the onset of instability have been discussed.
TL;DR: In this paper, theoretical results of the heat transfer characteristics and the fin efficiency of the annular fin are presented, and the results obtained from the model are validated by comparing with those obtained from other researchers.
TL;DR: In this paper, a more consistent comparison method is presented and is demonstrated to work by comparison of the performance of an experimentally investigated pin fin heat exchanger with that of a smooth pipe heat exchange.
17 Jul 2006
TL;DR: In this paper, the performances of three types of heat exchangers that use the louver fin geometry were compared and the results obtained are compared and compared using both the dip testing method and wind tunnel experiment.
Abstract: The performances of three types of heat exchangers that use the louver fin geometry: (1) parallel flow parallel fin with extruded flat tubes heat exchanger (PF2), (2) parallel flow serpentine fin with extruded flat tubes heat exchanger (PFSF) and (3) round tube wave plate fin heat exchanger (RTPF) have been experimentally studied under dry, wet and frost conditions and results are presented. The parameters quantified include air-side pressure drop, water retention on the surface of the heat exchanger, capacity and overall heat transfer coefficient for air face velocity 0.9, 2 and 3 m/s, air humidity 70% and 80% and different orientations. The performances of three types of heat exchanger are compared and the results obtained are presented. The condensate drainage behavior of the air-side surface of these three heat exchanger types was studied using both the dip testing method and wind tunnel experiment.
TL;DR: In this article, the authors investigated new factors such as fin types and manufacturing types of the tube affecting the thermal contact conductance and found a correlation between thermal contact resistance and the effective factors in fin-tube heat exchangers with 7mm tube.
TL;DR: In this paper, a new numerical technique for the analysis of multistream heat exchangers is proposed, which involves partitioning the exchanger in both axial and normal directions.
TL;DR: In this article, the authors used a simple thermal resistance model based on developing laminar flow in rectangular channels, the actual mean heat transfer coefficients are obtained in order to develop a simple heat transfer model for the impingement plate fin heat sink, and the experimental results are combined into a dimensionless correlation for channel average Nusselt number Nu ~ f(L *,Pr).
Abstract: *† Impingement cooling of plate fin heat sinks is examined. Experimental measurements of thermal performance were performed with four heat sinks of various impingement inlet widths, fin spacings, fin heights and airflow velocities. The percent uncertainty in the measured thermal resistance was a maximum of 2.6% in the validation tests. Using a simple thermal resistance model based on developing laminar flow in rectangular channels, the actual mean heat transfer coefficients are obtained in order to develop a simple heat transfer model for the impingement plate fin heat sink. The experimental results are combined into a dimensionless correlation for channel average Nusselt number Nu ~ f(L * ,Pr). We use a dimensionless thermal developing flow length, L * = (L/2) / (DhRePr), as the independent parameter. Results show that Nu ~ * L / 1 , similar to developing flow in parallel channels. The heat transfer model covers the practical operating range of most heat sinks, 0.01 < L * < 0.18. The accuracy of the heat transfer model was found to be within 11% of the experimental data taken on four heat sinks and other experimental data from the published literature at channel Reynolds numbers less than 1200. The proposed heat transfer model may be used to predict the thermal performance of impingement air cooled plate fin heat sinks for design purposes.
TL;DR: In this paper, the effect of fin thickness on the air-side performance of wavy fin-and-tube heat exchangers under dehumidifying conditions was investigated, and a correlation between fin thickness and heat transfer and friction correlations was proposed.
TL;DR: In this paper, a numerical and experimental investigation of a cold thermal energy storage system involving phase-change process dominated by heat conduction is presented, which involves a fluid flowing inside a horizontal finned tube surrounded by a phase change material (PCM).
TL;DR: In this article, the authors provided a thermoelectric air-conditioning system with a water-cooled sleeve heat sink in the hot side of the thermal pellets, and compared the overall heat transfer rates qt, the total heat resistances Rt between the water cooled and air cooled heat sinks as well as the optimum fin length, the optimum fluid flow velocity and the optimal fin gap distance.
Abstract: Thermoelectric air-conditioners (TEACs) are becoming much concerned due to their many advantages, but the low COPs limit their broad applications. The two key factors to raise the COPs of TEACs are both the improvement of thermoelectric materials and the optimum design of hot side heat sinks. This paper provides a thermoelectric air-conditioning system with a water-cooled sleeve heat sink in the hot side of the thermoelectric pellets, and compares the overall heat transfer rates qt, the total heat resistances Rt between the water-cooled and air-cooled heat sinks as well as the optimum fin length, the optimum fluid flow velocity and the optimum fin gap distance. The simulation results show that the overall heat transfer rate of water-cooled heat sink is more than 20 times that of air-cooled heat sink under the other same circumstances, as a result of the improvement of heat sink, the optimum COP of the thermoelectric air-conditioning system with the water-cooled heat sink proximately doubles that with the air-cooled heat sink. This novel system could be simply installed and applied all the year round for cooling in summer and heating in winter. Copyright © 2005 John Wiley & Sons, Ltd.