Effect of Inlet Flow Angle on Performance of Multilouvered Fin Heat Exchangers

2003 ◽  
Author(s):  
Dahai Guo ◽  
Danesh K. Tafti
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Inlet Flow ◽  
Flow Angle ◽  
The Heat Transfer Coefficient ◽  
Effective Reynolds Number

The effect of inlet flow angles on flat tube multilouvered fin heat exchangers is studied. Five inlet flow angles, α= ±25, ±45 and 0 degrees are employed with respect to the face of the heat exchanger. One louver angle θ = 25 degrees, and three fin pitches, Fp = 1.0, 1.5 and 2.0 are considered. There is a strong correlation between the response of the flow efficiency and heat transfer coefficient to inlet flow angle. Positive flow angles, which are in the same direction as the louver angle, have to undergo a smaller rotation to be aligned with louver directed flow in the bank, and exhibit better performance characteristics than negative inlet flow angles. The first-order effect of inlet flow angles is to reduce the effective mass flow rate and Reynolds number through the heat exchanger. For positive flow angles and small fin pitches, the heat transfer coefficient correlates well with the effective Reynolds number {Reeff = Re(cosα)}. However, this is not the case when flow angles are negative and the fin pitch increases. Under these conditions, the Nusselt number deviates considerably from the effective Reynolds number analogy, with a subsequent loss in heat transfer capability. For large negative inlet flow angles (α = −45), the heat transfer coefficient drops as much as 50% for a fin pitch Fp = 2.

scholarly journals Experimental Research and Simulation of Fin and Tube Heat Exchanger

2017 ◽  
Vol 9 (4) ◽  
pp. 451-461
Author(s):  
Artur Rubcov ◽  
Sabina Paulauskaitė ◽  
Violeta Misevičiūtė
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Ventilation System ◽  
Experimental Tests ◽  
Maximum Heat ◽  
Tube Heat Exchanger ◽  
The Heat Transfer Coefficient

The paper provides the results of experimental and theoretical test of a wavy fin and tube heat exchanger used to cool air in a ventilation system when the wavy fin of the heat exchanger is dry and wet. The experimental tests, performed in the range of 1000<Re<4500 of the Reynolds number applying LMTD-LMED methodology, determined the dependency of the heat transfer coefficient on the supplied air flow rate with the varying geometry of the heat exchanger (the number of tube rows, the distance between fins, the thickness of the fin and the diameter of the tube). The experimental tests were performed on 9 heat exchangers in heating and 6 heat exchangers in cooling mode. After processing the results of the experimental tests, empirical equation defining the characteristics of the heat transfer coefficient of all heat exchangers were derived. The maximum heat transfer coefficient deviation is 11.6 percent. The correction factor of the wet fin (Lewis number) depending on the number of Reynolds, which ranges from 0.75 to 1.1 also is determined. Maximum capacity deviation equals 3.7 percent. The obtained equations can only be applied to a certain group of heat exchangers (with the same shape of fins or the distance between the tubes). The results of the experimental test and simulation with ANSYS program are compared and the heat transfer coefficients vary from 6.5 to 11.4 percent.

scholarly journals Intensified Thermal Conductivity and Convective Heat Transfer of Ultrasonically Prepared CuO–Polyaniline Nanocomposite Based Nanofluids in Helical Coil Heat Exchanger

2019 ◽  
Vol 64 (2) ◽  
pp. 271-282 ◽  
Author(s):  
Abhishek Lanjewar ◽  
Bharat Bhanvase ◽  
Divya Barai ◽  
Shivani Chawhan ◽  
Shirish Sonawane
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Base Fluid ◽  
Cuo Nanoparticles ◽  
The Heat Transfer Coefficient

In this study, investigation of convective heat transfer enhancement with the use of CuO–Polyaniline (CuO–PANI) nanocomposite basednanofluid inside vertical helically coiled tube heat exchanger was carried out experimentally. In these experiments, the effects of different parameters such as Reynolds number and volume % of CuO–PANI nanocomposite in nanofluid on the heat transfer coefficient of base fluid have been studied. In order to study the effect of CuO–PANI nanocomposite based nanofluid on heat transfer, CuO nanoparticles loaded in PANI were synthesized in the presence of ultrasound assisted environment at different loading concentration of CuO nanoparticles (1, 3 and 5 wt.%). Then the nanofluids were prepared at different concentrations of CuO–PANI nanocomposite using water as a base fluid. The 1 wt.% CuO–PANI nanocomposite was selected for the heat transfer study for nanofluid concentration in the range of 0.05 to 0.3 volume % and Reynolds number range of was 1080 to 2160 (±5). Around 37 % enhancement in the heat transfer coefficient was observed for 0.2 volume % of 1 wt.% CuO–PANI nanocomposite in the base fluid. In addition, significant enhancement in the heat transfer coefficient was observed with an increase in the Reynolds number and percentage loading of CuO nanoparticle in Polyaniline (PANI).

scholarly journals DEVELOPMENT OF HIGH EFFICIENT SHELL-AND-TUBE HEAT EXCHANGERS BASED ON PROFILED TUBES

2020 ◽  
Author(s):  
Djamalutdin Chalaev ◽  
◽  
Nina Silnyagina ◽  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Transfer Coefficient ◽  
Hydraulic Resistance ◽  
Heat Exchangers ◽  
Experimental Studies ◽  
Corrugated Tube ◽  
The Heat Transfer Coefficient

The use of advanced heat transfer surfaces (corrugated tubes of various modifications) is an effective way to intensify the heat transfer and improve the hydraulic characteristics of tubular heat exchangers. The methods for evaluating the use of such surfaces as working elements in tubular heat exchangers have not been developed so far. The thermal and hydrodynamic processes occurring in the tubes with the developed surfaces were studied to evaluate the efficiency of heat exchange therein. Thin-walled corrugated flexible stainless steel tubes of various modifications were used in experimental studies. The researches were carried out on a laboratory stand, which was designed as a heat exchanger type "tube in tube" with a corrugated inner tube. The stand was equipped with sensors to measure the thermal hydraulic flow conditions. The comparative analysis of operation modes of the heat exchanger with a corrugated inner tube of various modifications and the heat exchanger with a smooth inner tube was performed according to the obtained data. Materials and methods. A convective component of the heat transfer coefficient of corrugated tube increased significantly at identical flow conditions comparing with a smooth tube. Increasing the heat transfer coefficient was in the range of 2.0 to 2.6, and increased with increasing Reynolds number. The increase in heat transfer of specified range outstripped the gain of hydraulic resistance caused by increase of the flow. Results and discussion. CFD model in the software ANSYS CFX 14.5 was adapted to estimate the effect of the tube geometry on the intensity of the heat transfer process. A two-dimensional axially symmetric computer model was used for the calculation. The model is based on Reynolds equation (Navier-Stokes equations for turbulent flow), the continuity equation and the energy equation supplemented by the conditions of uniqueness. SST-turbulence model was used for the solution of the equations. The problem was solved in the conjugate formulation, which allowed assessing the efficiency of heat exchange, depending on various parameters (coolant temperature, coolant velocity, pressure). The criteria dependences were obtained Nu = f (Re, Pr). Conclusions. The use a corrugated tube as a working element in tubular heat exchangers can improve the heat transfer coefficient of 2.0 - 2.6 times, with an increase in hydraulic resistance in the heat exchanger of 2 times (compared with the use of smooth tubes). The criteria dependences obtained on the basis of experimental studies and mathematical modeling allow developing a methodology for engineering calculations for the design of new efficient heat exchangers with corrugated tubes.

An Experimental Study on Convective Boiling Heat Transfer in Micro Heat Exchangers

2010 ◽  
Author(s):  
Chien-Yuh Yang ◽  
Wei-Chi Liu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
High Heat ◽  
Vapor Quality ◽  
Straight Flow ◽  
The Heat Transfer Coefficient

Attributed to its high heat transfer coefficient, evaporating cooling involving the use of micro heat exchangers is considered a possible thermal management solution for cooling of high heat flux electronic devices. The desire to develop high-performance micro heat exchangers operating in the evaporation regime provides a major motivation for the present work. Methanol evaporated in two micro heat exchangers with chevron flow passages and straight flow passages respectively were tested in the present study. The test results show that the heat transfer coefficient increased with increasing flow rate in both chevron and straight flow passages micro heat exchangers. However, the effect of vapor quality on the heat transfer coefficient in the straight passages heat exchanger is in adverse to that in the chevron passages heat exchanger. The heat transfer coefficient increased with increasing vapor quality in the chevron passages heat exchanger but decreased in the straight passages heat exchanger. The flow visualization through transparent cover heat exchangers showed that the liquid film inside channel is partially dry out in the straight passages heat exchanger. The dryout portion area increased with increasing heating rate and exit vapor quality. This degraded the average heat transfer performance for evaporation in the straight passages heat exchanger. Because of the surface tension effect, the liquid film was dragged at the intersection corner of the upper and lower plate chevron passages. There is no significant dryout portion in the chevron passages heat exchanger. The relation of vapor quality with heat transfer performance in chevron passages heat exchanger is therefore similar to the boiling in a single channel prior to critical heat flux condition.

scholarly journals CFD Analysis on the Air-Side Thermal-Hydraulic Performance of Multi-Louvered Fin Heat Exchangers at Low Reynolds Numbers

2017 ◽  
Author(s):  
Arslan Saleem ◽  
Man-Hoe Kim
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Reynolds Numbers ◽  
Hydraulic Performance

The air side thermal hydraulic performance of multi-louvered aluminium fin heat exchangers is investigated. A detailed study was performed to analyse the thermal performance of air over a wide range of Reynolds number i.e. from 30 to 250. Air-side heat transfer coefficient and air pressure drop were calculated and validated over the mentioned band of Reynolds numbers. Critical Reynolds number was determined numerically and the variation in flow physics along with the thermal and hydraulic performance of microchannel heat exchanger associated with R_cri has been reported. Moreover, a parametric study of the multi-louvered aluminium fin heat exchangers was also performed for 36 heat exchanger configurations with the louver angles (19-31°), fin pitches (1.0, 1.2, 1.4 mm) and flow depths (16, 20, 24 mm); and the geometric configuration exhibiting the highest thermal performance was reported. The air-side heat transfer coefficient and pressure drop results for different geometrical configurations were presented in terms of Colburn j factor and Fanning friction factor f, as a function of Reynolds number based on louver pitch.

scholarly journals Evaluation of selected methods of the heat transfer coefficient determination in fin-and-tube cross-flow heat exchangers

2018 ◽  
Vol 240 ◽  
pp. 02004 ◽  
Author(s):  
Tomasz Bury ◽  
Małgorzata Hanuszkiewicz Drapała
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow Heat ◽  
The Heat Transfer Coefficient

The work is a part of a thermodynamic analysis of a finned cross-flow heat exchanger of the liquid-gas type. The heat transfer coefficients on the liquid and the gas side and the area of the heat transfer are the main parameters describing such a device. The basic problem in computations of such heat exchangers is determination of the coefficient of the heat transfer from the finned surfaces to the gas. The differences in the heat transfer coefficient local values resulting from the non-uniform flow of mediums through the exchanger complicates the analysis additionally. Six Nusselt number relationships are selected as suitable for the considered heat exchanger, and they are used to calculate the heat transfer coefficient for the air temperature ranging from 10°C to 30°C and for the velocity values ranging from 2 m/s to 20 m/s. In the next step, the gas-side heat transfer coefficient is determined by means of numerical simulations using a numerical model of a repetitive fragment of the heat exchanger under consideration. Finally, the Wilson plot method is also used. The work focuses on an analysis of the in-house HEWES code sensitivity to the method of the heat transfer coefficient determination. The authors believe that the analysis may also be useful for the evaluation of different methods of the heat transfer coefficient computation.

Experimental Analysis of Fin and Tube Heat Exchanger in Heating and Cooling Mode

2017 ◽  
Author(s):  
Artur Rubcov ◽  
Sabina Paulauskaitė ◽  
Violeta Misevičiūtė
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Ventilation System ◽  
Experimental Tests ◽  
Cooling Mode ◽  
Tube Heat Exchanger ◽  
The Heat Transfer Coefficient

The paper provides the results of experimental tests of a wavy fin and tube heat exchanger used to heat (cool) air in a ventilation system when the wavy fin of the heat exchanger is dry and wet. The experimental tests, performed in the range of 1000<Re<4500 of the Reynolds number, determined the dependency of the heat transfer coefficient on the amount of supplied air with the varying geometry of the heat exchanger (the number of tube rows, the distance between fins, the thickness of the fin and the diameter of the tube). The experimental tests were performed on 9 heat exchangers in heating mode (dry fin) and 6 heat exchangers in cooling mode (wet fin). The ratio of heat transfer coefficient values when the fin is dry and wet varies from 0.79 to 1.12. After processing the results of the experimental tests, equations defining the dependency of the heat transfer coefficient on the amount of air and varying geometric parameters of the heat exchanger were derived, based on which 86% to 88% of the results do not exceed the 10% tolerance margin and the standard deviation varies from 3.5% to 4.3%.

scholarly journals STUDI EKSPERIMENTAL PERPINDAHAN KALOR KONVEKSI, PENURUNAN TEKANAN DAN FAKTOR GESEKAN PADA ALAT PENUKAR KALOR MENGGUNAKAN MICRO-FIN TUBE

2019 ◽  
Vol 18 (1) ◽  
Author(s):  
Ahmad Imam Rifa’i ◽  
Budi Kristiawan ◽  
Agung Tri Wijayanta
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Flow Region ◽  
Counter Flow ◽  
Flow Heat ◽  
Fin Tube ◽  
The Heat Transfer Coefficient

<p><em>Micro-fin is the popular technique for increasing heat transfer performance of the heat exchangers. In this research, the heat transfer coefficient of water inside counter-flow heat exchangers with micro-fin was investigated by experiment at the Reynolds number (Re) was varied from 4000-10,000. The results show that the heat transfer coefficient increase with increasing Reynolds number. Furthermore, effect helical micro-fin increasing pressure drop and friction factor at turbulent flow region.</em></p>

Test and Analysis on the Heat Transfer Coefficient of the Mixed Plate Heat Exchanger

2014 ◽  
Vol 552 ◽  
pp. 55-60
Author(s):  
Zheng Ming Tong ◽  
Peng Hou ◽  
Gui Hua Qin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Mixed Mode ◽  
Plate Heat Exchanger ◽  
Plate Heat ◽  
Fitting Method ◽  
Engineering Significance ◽  
The Heat Transfer Coefficient

In this article, we use BR0.3 type plate heat exchanger for experiment,and the heat transfer coefficient of the mixed plate heat exchanger is explored. Through the test platform of plate heat exchanger, a large number of experiments have been done in different mixed mode but the same passageway,and lots experimental data are obtained. By the linear fitting method and the analysis of the data, the main factors which influence the heat transfer coefficient of mixed plate heat exchanger were carried out,and the formula of heat transfer coefficient which fits at any mixed mode plate heat exchanger is obtained, to solve the problem of engineering calculation.The fact , there is no denying that the result which we get has great engineering significance

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