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1.
《Applied Thermal Engineering》2007,27(2-3):539-544
The Taguchi method is a well-known parametric study tool in engineering quality and experimental design. This study analyzes five experimental factors (flow depth, ratio of fin pitch and fin thickness, tube pitch, number of louvers and angle of louver) affecting the heat transfer and pressure drop of a heat exchanger with corrugated louvered fins using the Taguchi method. Fifteen samples are selected from experimental database and the heat transfer and flow friction characteristics are analyzed. The results show that flow depth, ratio of fin pitch and fin thickness and the number of the louvers are the main factors that influence significantly the thermal hydraulic performance of the heat exchanger with corrugated louvered fins. Therefore, these three factors are considered as the main factors for an optimum design of a heat exchanger. 相似文献
2.
《International Journal of Heat and Mass Transfer》2006,49(21-22):4058-4069
The louvered fin heat exchanger, a type of compact heat exchanger, has been used heavily in the automotive and air conditioning industries for the last several decades. The majority of past research, aimed towards improving louvered fin exchanger efficiency, has focused on optimizing various parameters of the louvered fin. The experimental study presented in this paper concentrates instead on augmenting the heat transfer along the tube wall of the compact heat exchanger through the use of winglets placed on the louvers. The experiments were completed on 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°. The Reynolds numbers tested, based on louver pitch, were between 230 and 1016. A number of geometrical winglet parameters, including angle of attack, aspect ratio, direction, and shape, were all evaluated based on heat transfer augmentation, friction factor augmentation, and efficiency index (combination of both augmentations). In an attempt to optimize these winglet parameters, tube wall heat transfer augmentations as high as 39% were achieved with associated friction factor augmentations as high as 23%. 相似文献
3.
Experimental study on heat and mass transfer characteristics of louvered fin-tube heat exchangers under wet condition 总被引:1,自引:0,他引:1
Thanh-Long PhanKeun Sun Chang Young Chul Kwon Jeong-Tae Kwon 《International Communications in Heat and Mass Transfer》2011,38(7):893-899
An experimental study was conducted to investigate the effect of a tube row, a fin pitch and an inlet humidity on air-side heat and mass transfer performance of louvered fin-tube heat exchangers under wet condition. Experimental conditions were varied by three fin pitches, two rows, and two inlet relative humidities. From the experimental results, it was found that the heat transfer performance decreased and the friction increased with the decrease of a fin pitch, for 2 row heat exchanger. The effect of a fin pitch on heat transfer performance was negligible with 3 row heat exchanger. The change in a relative humidity was not affected heat transfer and friction. However, the mass transfer performance was slightly decreased with the increase of a relative humidity and with the decrease of a fin pitch. The mass transfer performance decreased with the decrease of a fin pitch. The mass transfer performance of the louvered fin-and-tube heat exchanger was different according to the number of a tube row. 相似文献
4.
Michael J. Lawson Karen A. Thole 《International Journal of Heat and Mass Transfer》2008,51(9-10):2346-2360
Delta winglets are known to induce the formation of streamwise vortices and increase heat transfer between a working fluid and the surface on which the winglets are placed. This study investigates the use of delta winglets to augment heat transfer on the tube surface of louvered fin heat exchangers. It is shown that delta winglets placed on louvered fins produce augmentations in heat transfer along the tube wall as high as 47% with a corresponding increase of 19% in pressure losses. Manufacturing constraints are considered in this study whereby piercings in the louvered fins resulting from stamping the winglets into the louvered fins are simulated. Comparisons of measured heat transfer coefficients with and without piercings indicate that piercings reduce average heat transfer augmentations, but significant increases still occur with respect to no winglets present. 相似文献
5.
An experimental study on the air-side heat transfer and pressure drop characteristics for brazed aluminum heat exchangers with multi-region louver fins and flat tubes was conducted. A series of tests were conducted for heat exchangers with different numbers of louver regions at the air-side Reynolds numbers of 400–1600 based on the louver pitch. The air-side thermal performance data were analyzed by using the effectiveness-NTU method. The characteristics of the heat transfer and pressure drop for heat exchangers with different geometry parameters were presented in terms of the Colburn j factor and Fanning friction f factor as function of the Reynolds number. 相似文献
6.
Three-dimensional simulations of four louver-tube junction geometries are performed to investigate the effect on louver and tube friction and heat transfer characteristics. Three Reynolds numbers, 300, 600 and 1100, based on bulk velocity and louver pitch are calculated. Strong three-dimensionality exists in the flow structure in the region where the angled louver transitions to a flat landing adjoining the tube surface, whereas the flow on the angled louver far from the tube surface is nominally two-dimensional. Due to the small spatial extent of the transition region, its overall impact on louver heat transfer is limited, but the strong unsteady flow acceleration on the top louver surface augments the heat transfer coefficient on the tube surface by over 100%. In spite of the augmentation, the presence of the tube lowers the overall Nusselt number of the heat exchanger between 25% and 30%. Comparisons with correlations derived from experiments on full heat exchanger cores show that computational modeling of a small subsystem can be used reliably to extract performance data for the full heat exchanger. 相似文献
7.
The performance of frosted finned-tube heat exchangers of different fin types is investigated by experiments in this paper. The effects of the air flow rate, the air relative humidity, the refrigerant temperature, and the fin type on the thermofluid characteristics of the heat exchangers are discussed. The time variations of the heat transfer rate, the overall heat transfer coefficient, and the pressure drop of the heat exchangers are presented. The heat transfer rate, the overall heat transfer coefficient, and the pressure drop for heat exchangers with re-direction louver fins are higher than those with flat plate fins and one-sided louver fins are. The amount of frost formation is the highest for heat exchangers with re-direction louver fins. 相似文献
8.
Experimental studies were conducted to investigate the air-side heat transfer and pressure drop characteristics of a novel louvered fins and flat tube heat exchangers. A series of tests were conducted for 9 heat exchangers with different fin space and fin length, at a constant tube-side water flow rate of 2.8 m3/h. The air side thermal performance data were analyzed using the effectiveness-NTU method. Results were presented as plot of Colburn j factor and friction factor f against the Reynolds number in the range of 500–6500. The characteristics of the heat transfer and pressure drop of different fin space and fin length were analyzed and compared. In addition, the curves of the heat transfer coefficients vs. pumping power per unit heat transfer area were plotted. Finally, the area optimization factor was used to evaluate the thermal hydraulic performance of the louvered fins with differential geometries. The results showed that the j and f factors increase with the decrease of the fin space and fin length, and the fin space has more obvious effect on the thermal hydraulic characteristics of the novel louvered fins. 相似文献
9.
10.
A.W. Fan J.J. Deng A. Nakayama W. Liu 《International Journal of Heat and Mass Transfer》2012,55(19-20):5205-5213
In the present work, characteristics of heat transfer, flow resistance, and overall thermo-hydraulic performance of turbulent airflow in a circular tube fitted with louvered strip inserts were investigated through numerical simulation. Our main attention was paid to the effects of the slant angle and pitch of the turbulators. The results show that the Nusselt number is augmented by 2.75–4.05 times (Nu = 108.71–423.87) as that of the smooth tube. The value of performance evaluation criterion (PEC) lies in the range of 1.60–2.05, which demonstrates that the louvered strip insert has a very good overall thermo-hydraulic performance. Moreover, the computational results indicate that larger slant angle and small pitch can effectively enhance the heat transfer rate, but also increase the flow resistance. Furthermore, it is noted that the Nusselt number and friction factor are more sensitive to the slant angle than the inserts pitch. Comparatively steady and good overall thermo-hydraulic performance can be obtained at a moderate slant angle together with a small pitch. All these data show that the louvered strip is a promising tube insert which would be widely used in heat transfer enhancement of turbulent flow. 相似文献
11.
To obtain better fluid mixing and higher heat transfer rate in the low Reynolds number regime, various types of fins have been employed for electronic cooling applications. However, previous works showed that there are no remarkable differences in the thermal performance of a straight-plate and a channel with louvered-fins when the Reynolds number is low or moderate. In this paper, the Constructal law is applied to optimize the geometry of a channel with louvered-fins, where the objective is to maximize the total heat transfer rate and minimize the pressure loss. The selected domain has three degrees of freedom; the louver angle ratio, the louver pitch ratio, and the inlet louver length to outlet louver length ratio. The results showed that the effect of louver on the louver pitch ratio and the inlet louver length to outlet louver length ratio. There is a minimum value for the louver pitch ratio and below this value the vortices upstream of the turnaround louver block the distance between louvers and so decreases the flow efficiency. A comparison between results and previous experimental studies indicated that the channel optimized by constructal law is considerably superior compared to the standard channel in low Reynolds number regime. 相似文献
12.
13.
Junqi DONG Jiangping CHEN Zhijiu CHEN 《Frontiers of Energy and Power Engineering in China》2008,2(1):99-106
Experimental studies were conducted to investigate the air-side heat transfer and pressure drop characteristics of a novel
louvered fins and flat tube heat exchangers. A series of tests were conducted for 9 heat exchangers with different fin space
and fin length, at a constant tube-side water flow rate of 2.8 m3/h. The air side thermal performance data were analyzed using the effectiveness-NTU method. Results were presented as plot
of Colburn j factor and friction factor f against the Reynolds number in the range of 500–6500. The characteristics of the heat transfer and pressure drop of different
fin space and fin length were analyzed and compared. In addition, the curves of the heat transfer coefficients vs. pumping
power per unit heat transfer area were plotted. Finally, the area optimization factor was used to evaluate the thermal hydraulic
performance of the louvered fins with differential geometries. The results showed that the j and f factors increase with the decrease of the fin space and fin length, and the fin space has more obvious effect on the thermal
hydraulic characteristics of the novel louvered fins.
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Translated from Journal of Shanghai Jiaotong University, 2007, 41(3): 380–383 [译自: 上海交通大学学报] 相似文献
14.
Jufang FAN Weikun DING Zhigeng WU Yaling HE Wenquan TAO Yongxin ZHENG Yifeng GAO Ji SONG 《Frontiers in Energy》2011,5(1):59
In this paper, a simple yet efficient performance comparison method is proposed based on the assumptions of constant properties and identical frontal area. For this method, no correlations are required, and a small number of discrete data are sufficient. To illustrate the feasibility of the proposed approach, a new slotted fin with 4 mm tubes is designed to replace the original louvered fin with tubes of 7 mm. The orthogonal design method is adopted in the fin design to reduce the number of computational cases significantly, and yet a nearly optimum combination of major geometric factors can still be obtained. The reasonable parametric combination of 3 global parameters is obtained by analyzing the numerical results of 16 plain plate fins. Based on this result, 3 new slotted fins with different fin pitches are studied. The slotted fin with a fin pitch of 1.4 mm is recommended after considering the heat transfer, comprehensive performance, and cost of material and operation. The result shows that compared with the original louvered fin, the recommended fin not only increases the heat transfer rate by 2.2%, 22.5%, and 13.7% under an identical flow rate, identical pressure drop, and identical pumping power constraint, respectively, but also saves approximately 36% of the copper tube materials. 相似文献
15.
Smith Eiamsa-ard Somsak Pethkool Chinaruk Thianpong Pongjet Promvonge 《International Communications in Heat and Mass Transfer》2008
In the present work, heat transfer and friction characteristics were experimentally investigated, employing louvered strips inserted in a concentric tube heat exchanger. The louvered strip was inserted into the tube to generate turbulent flow which helped to increase the heat transfer rate of the tube. The flow rate of the tube was in a range of Reynolds number between 6000 and 42,000. The turbulent flow devices were consisted of (1) the louvered strips with forward or backward arrangements, and (2) the louvered strip with various inclined angles (θ = 15°, 25° and 30°), inserted in the inner tube of the heat exchanger. In the experiment, hot water was flowed through the inner tube whereas cold water was flowed in the annulus. The experimental data obtained were compared with those from plain tubes of published data. Experimental results confirmed that the use of louvered strips leads to a higher heat transfer rate over the plain tube. The increases in average Nusselt number and friction loss for the inclined forward louvered strip were 284% and 413% while those for the backward louvered strip were 263% and 233% over the plain tube, respectively. In addition, the use of the louvered strip with backward arrangement leads to better overall enhancement ratio than that with forward arrangement around 9% to 24%. 相似文献
16.
Extended surfaces mostly aim to improve the heat transfer upon increasing the area of heat transfer. In this paper, the influence of using fins on flow behaviors and the heat transfer of the shell and tube heat exchanger has been investigated. In this regard, the present results are verified with available experimental data in the literature for a helical tube without fins. The effects of fin density (fin per inch), its height, and material have been studied on the heat transfer rate. In addition, the effects of radial pitch and the number of coil loops are studied. The results indicate that implementing extended surfaces significantly increases the heat transfer rate. The increase of fin density from 8 to 12 and the height from 11.5 to 13.5 mm enhances heat transfer up to 48% and 43% depending on Dean number, respectively. The rise of coil pitch augments the overall heat transfer, and it is more efficient at lower Dean numbers. The predicted results also show that the fin material does not have any significant effect on heat transfer. 相似文献
17.
《Energy Conversion and Management》1999,40(15-16):1743-1751
A compact gas to gas heat exchanger needs large heat transfer areas on both fluid sides. This can be realised by adding secondary surfaces. The secondary surfaces are plate fin, strip fin, and louvered fin, etc. The fins extend the heat transfer surfaces and promote turbulence.This paper presents a gas to gas heat exchanger with strip fins. The heat exchanger design and construction are based on a method to seal rectangular strip fins in slots in opposite walls of a rectangular pipe. Fins are fixed and sealed to the walls simultaneously by high temperature brazing of glass mixed with metals in a furnace. The additional advantage of glass is that it forms a coating on the heat transfer surface to protect the surface from corrosion.A number of measurements were carried out to test the performance of this heat exchanger. Not surprisingly, the measurement results indicate that heat transfer coefficient and pressure drop increase with the ratio of heat transfer area to volume (fin density). Colburn factor and friction factor versus Reynolds number are presented. 相似文献
18.
The heat transfer enhancement performance of a phase change buried tubes thermal storage system is influenced by major parameters such as arrangement of heat transfer tubes, fin structure and fin geometry size. We developed a three-dimensional numerical model with two different arrangements and five different enhanced heat transfer structures respectively. For the sake of analysis the effects of arrangement of heat transfer tubes, fin structure and fin geometry size. In addition, we applied the enthalpy-transforming model to obtain the liquid fraction and location of the solid-liquid interface at different time in the phase change process. The numerical results show that the melting time of the thermal storage system model with a triangle arrangement is about 6.1% longer than that of the model with a square arrangement. Besides, the melting time of the model with 55 mm tube pitch is about 16.7% shorter than that of tube pitch with 60 mm. Moreover, the buried tube thermal storage system models with circle fins have the shortest melting time, which is 18 seconds. Melting time of the model with circle fins is about 40% shorter than that of the model with smooth tube. In addition, the melting time of the model with 3 mm fin thickness is 10 seconds, which is the shortest. The model with thicker fins means the shorter time of melting process. Moreover, the melting time of the model with 10.5 mm fin spacing is about 23.5% shorter than that of the model with 12.5 mm fin spacing, which is 13 seconds. In conclusion, the main factor of the melting time is the heat transfer area. It provides a guidance for the design and reconstruction of the type of heat storage structure. 相似文献
19.
《International Journal of Heat and Mass Transfer》2007,50(1-2):361-366
The effect of inclination angle on the louver finned tube heat exchanger subject to natural convection condition is reported in this study. It is found that the inclination angle plays an importance role on the performance of the louver finned heat exchanger. Performance of the heat exchanger is associated with the interactions between fin, louver, tube, and inclination angle. The heat transfer performance generally decreases with the rise of the inclination angle. This decrease of heat transfer performance is due to the blockage fin and its reversed heat dissipating direction against the raising air. However, at an inclination angle such as 30–45°, a considerable increase of heat transfer performance is seen. This is because appreciable amount of air flow was directed by the louver, causing a “louver-directed” phenomenon as that of in forced convection. With a further increase of inclination angle, the blockage effect caused by the fin is so strong as to offset the “louver-directed” phenomenon. Unlike those shown in force convection, the heat transfer performance decreased with the number of tube row. 相似文献
20.
Erling Næss 《Applied Thermal Engineering》2010,30(13):1531-1537
An experimental investigation of the heat transfer and pressure drop performance of ten finned tube bundles using serrated fins is presented. All tube bundles had staggered layouts, and the influence on varying tube bundle layout, tube and fin parameters are presented. The heat transfer coefficient experienced a maximum when the flow areas in the transversal and diagonal planes were equal. An increase in the fin pitch increased the heat transfer coefficient; the same was observed with an increase in fin height. The pressure drop coefficient showed no influence of the tube bundle layout for small pitch ratios, but dropped significantly for higher ratios. Increasing fin pitch reduced the pressure drop, whereas varying fin height had insignificant effect. None of the literature correlations were able to reproduce the experiments for the entire range of tested conditions. A set of correlations were developed, reproducing the experimental data to within ±5% at a confidence interval of 95%. 相似文献