scholarly journals Experimental determination of correlations for mean heat transfer coefficients in plate fin and tube heat exchangers

2012 ◽  
Vol 33 (3) ◽  
pp. 1-24 ◽  
Author(s):  
Dawid Taler
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Correlation Coefficients ◽  
Outlet Temperature ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nonlinear Regression Method ◽  
Propagation Rule

Abstract This paper presents a numerical method for determining heat transfer coefficients in cross-flow heat exchangers with extended heat exchange surfaces. Coefficients in the correlations defining heat transfer on the liquid- and air-side were determined using a nonlinear regression method. Correlation coefficients were determined from the condition that the sum of squared liquid and air temperature differences at the heat exchanger outlet, obtained by measurements and those calculated, achieved minimum. Minimum of the sum of the squares was found using the Levenberg-Marquardt method. The uncertainty in estimated parameters was determined using the error propagation rule by Gauss. The outlet temperature of the liquid and air leaving the heat exchanger was calculated using the analytical model of the heat exchanger.

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.

The Correlation of Heat Transfer Coefficients for the Laminar Natural Convection in a Circular Finned-Tube Heat Exchanger

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Hie Chan Kang ◽  
Se-Myong Chang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Nusselt Number ◽  
Natural Convection ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Finned Tube ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Laminar Natural Convection

This study proposes an empirical correlation for laminar natural convection applicable to external circular finned-tube heat exchangers with wide range of configuration parameters. The transient temperature response of the heat exchangers was used to obtain the heat transfer coefficient, and the experimental data with their characteristic lengths are discussed. The data lie in the range from 1 to 1000 for Rayleigh numbers based on the fin spacing: the ratio of fin height to tube diameter ranges from 0.1 to 0.9, and the ratio of fin pitch to height ranges from 0.13 to 2.6. Sixteen sets of finned-tube electroplated with nickel–chrome were tested. The convective heat transfer coefficients on the heat exchangers were measured by elimination of the thermal radiation effect from the heat exchanger surfaces. The Nusselt number was correlated with a newly suggested composite curve formula, which converges to the quarter power of the Rayleigh number for a single cylinder case. The proposed characteristic length for the Rayleigh number is the fin pitch while that for the Nusselt number is mean flow length, defined as half the perimeter of the mean radial position inside the flow region bounded by the tube surface and two adjacent fins. The flow is regarded as laminar, which covers heat exchangers from a single horizontal cylinder to infinite parallel disks. Consequently, the result of curve fitting for the experimental data shows the reasonable physical interpretation as well as the good quantitative agreement with the correction factors.

Experimental Study and Genetic-Algorithm-Based Correlation on Shell-Side Heat Transfer and Flow Performance of Three Different Types of Shell-and-Tube Heat Exchangers

2006 ◽  
Vol 129 (9) ◽  
pp. 1277-1285 ◽  
Author(s):  
Qiu-wang Wang ◽  
Gong-nan Xie ◽  
Bo-tao Peng ◽  
Min Zeng
Keyword(s):  
Heat Transfer ◽  
Genetic Algorithm ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Transfer Coefficients ◽  
Shell Side ◽  
Heat Transfer Coefficients ◽  
Friction Factors ◽  
Shell And Tube

The heat transfer and pressure drop of three types of shell-and-tube heat exchangers, one with conventional segmental baffles and the other two with continuous helical baffles, were experimentally measured with water flowing in the tube side and oil flowing in the shell side. The genetic algorithm has been used to determine the coefficients of correlations. It is shown that under the identical mass flow, a heat exchanger with continuous helical baffles offers higher heat transfer coefficients and pressure drop than that of a heat exchanger with segmental baffles, while the shell structure of the side-in-side-out model offers better performance than that of the middle-in-middle-out model. The predicted heat transfer rates and friction factors by means of the genetic algorithm provide a closer fit to experimental data than those determined by regression analysis. The predicted corrections of heat transfer and flow performance in the shell sides may be used in engineering applications and comprehensive study. It is recommended that the genetic algorithm can be used to handle more complicated problems and to obtain the optimal correlations.

scholarly journals Numerical and experimental investigation of heat transfer of ZnO/Water nanofluid in the concentric tube and plate heat exchangers

2011 ◽  
Vol 15 (1) ◽  
pp. 183-194 ◽  
Author(s):  
Fard Haghshenas ◽  
Mohammad Talaie ◽  
Somaye Nasr
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Transfer Coefficients ◽  
Flow Rates ◽  
Plate Heat ◽  
Heat Transfer Coefficients ◽  
Mass Flow Rates

The plate and concentric tube heat exchangers are tested by using the water-water and nanofluid-water streams. The ZnO/Water (0.5%v/v) nanofluid has been used as the hot stream. The heat transfer rate omitted of hot stream and overall heat transfer coefficients in both heat exchangers are measured as a function of hot and cold streams mass flow rates. The experimental results show that the heat transfer rate and heat transfer coefficients of the nanofluid in both of the heat exchangers is higher than that of the base liquid (i.e., water) and the efficiency of plate heat exchange is higher than concentric tube heat exchanger. In the plate heat exchanger the heat transfer coefficient of nanofluid at mcold = mhot = 10 gr/sec is about 20% higher than base fluid and under the same conditions in the concentric heat exchanger is 14% higher than base fluid. The heat transfer rate and heat transfer coefficients increases with increase in mass flow rates of hot and cold streams. Also the CFD1 code is used to simulate the performance of the mentioned heat exchangers. The CFD results are compared to the experimental data and showed good agreement. It is shown that the CFD is a reliable tool for investigation of heat transfer of nanofluids in the various heat exchangers.

Oscillating Heat Transfer Correlations for Spiral-Coil Thermoacoustic Heat Exchangers

2015 ◽  
Vol 7 (3) ◽  
Author(s):  
Kriengkrai Assawamartbunlue ◽  
Channarong Wantha
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Transfer Coefficients ◽  
Spiral Coil ◽  
Heat Transfer Coefficients ◽  
Flow Heat ◽  
Heat Transfer Correlations ◽  
Coil Heat Exchanger ◽  
Coil Heat

Heat exchangers are the important parts in thermoacoustic refrigerators. Types and configurations of the heat exchangers affect flow behaviors through stacks, and heat transfer behaviors between working fluids and the heat exchangers. Steady-flow heat transfer correlations to design a heat exchanger are not suitable for the thermoacoustic refrigerators due to their oscillatory flow conditions in resonator tubes. In this paper, a heat transfer correlation for a spiral-coil heat exchanger is presented. The results from the experimental study were used to develop an empirical equation between the Colburn-j factor, the Prandtl number, and the Reynolds number to correlate the oscillating heat transfer coefficient at the spiral-coil heat exchangers. The results showed that using steady-flow heat transfer correlations for analyses and design of the heat exchanger could result in distinguished errors. The heat transfer correlations developed for oscillatory flows on fin heat exchangers are also not suitable to predict heat transfer coefficients for spiral-coil heat exchanger due to difference in flow behaviors on the heat transfer surface. For oscillatory flows, the heat transfer coefficients can be improved by using curved-liked surface such as spiral coil instead of straightlike surface such as fin coil. The relationships between the oscillating heat transfer coefficients at the heat exchangers, drive ratios, and operating frequencies are also presented. Higher drive ratios and operating frequency result in greater heat transfer coefficients.

scholarly journals CHAOTISED POLYMERIC HOLLOW FIBRE BUNDLE AS A CROSSFLOW HEAT EXCHANGER IN AIR-WATER APPLICATION

2020 ◽  
Vol 60 (4) ◽  
pp. 318-323
Author(s):  
Tereza Kroulíková ◽  
Ilya Astrouski ◽  
Miroslav Raudenský
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Fibre Diameter ◽  
Cross Flow ◽  
Hollow Fibre ◽  
Middle Part ◽  
Water Application ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow Heat

Fifteen years ago, polymeric hollow fibre heat exchangers were presented for the first time. Nowadays there are not only the shell-and-tube types as there were at the beginning. In this paper, six chaotised polymeric hollow fibre bundles with a different number of fibres were studied. The bundles presented varied in their fibre diameter, number and shape. These bundles were fixed into the module in such a way that the middle part serves as a cross-flow heat exchanger in an air tunnel. They were tested for air-water application with three different airflow rates. The overall heat transfer coefficients were determined, and the inner and outer heat transfer coefficients were derived. The modules presented achieved a heat transfer rate of up to 1309 W. The overall heat transfer coefficient reached a maximum of 339 Wm−2 K−1.

High Performance Micro-Channel Cross Flow Heat Exchangers

2005 ◽  
Author(s):  
Kevin W. Kelly ◽  
Andrew McCandless ◽  
Christoffe Marques ◽  
Ryan A. Turner ◽  
Shariar Motakef
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
High Performance ◽  
Gas Flow ◽  
Cross Flow ◽  
Micro Channel ◽  
Transfer Coefficients ◽  
Order Of Magnitude ◽  
Flow Heat

The performance of a micro-channel gas-liquid cross flow heat exchanger, manufactured by the LIGA technique is presented. Large heat transfer coefficients are achieved on the gas side by achieving gas-flow passage dimensions as low as 300 microns. Cross flow heat exchanger panels have been produced as large as 20 cm by 15 cm. These panels can be arranged in a variety of ways to produce heat exchangers capable of handling large thermal loads. Experimental results have shown that these heat exchangers are approximately one order of magnitude better, in terms of heat transfer per unit volume, than the commercially available tube-fin heat exchangers with characteristic cross flow channel dimensions that are typically three times larger.

scholarly journals Convection Heat Transfer Coefficients in Thermoacoustic Heat Exchangers: An Experimental Investigation

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4525 ◽  
Author(s):  
Piccolo ◽  
Sapienza ◽  
Guglielmino
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Boundary Layer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
Oscillating Flows ◽  
Heat Transfer Coefficients

This paper investigates the thermal performance of thermoacoustic heat exchangers subjected to acoustically oscillating flows. The analysis is carried out by experimental measurements of the heat fluxes sustained by the ambient heat exchanger of a prime mover of the standing wave type. A home-made parallel-plate heat exchanger is considered for the study. The gas-side convection heat transfer coefficients expressed as Nusselt numbers are determined over a wide range of velocity amplitudes of the oscillating flow. The experimental results are then compared to the predictions of a number of theoretical models currently applied in thermoacoustics such as the time-average steady-flow equivalent (TASFE) model, the root mean square Reynolds number (RMS-Re) model, and the boundary layer conduction model. The comparison suggests that the boundary layer model performs better than the rms-Re and TASFE models in predicting the heat transfer coefficients in oscillating flows. The relative difference between the model predictions and the experimental data amounts to 19%. A new correlation law, based on regression of the experimental data, is also proposed.

Experimental and Numerical Study on the Effects of the Relative Position of Film Hole and Orientation Ribs on the Film Cooling With Ribbed Cross-Flow Coolant Channel

2020 ◽  
Author(s):  
Bingran Li ◽  
Cunliang Liu ◽  
Lin Ye ◽  
Huiren Zhu ◽  
Fan Zhang
Keyword(s):  
Heat Transfer ◽  
Relative Position ◽  
Film Cooling ◽  
Numerical Study ◽  
Cross Flow ◽  
Internal Cooling ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Heat Transfer Coefficients ◽  
Numerical Studies

Abstract To investigate the application of ribbed cross-flow coolant channels with film hole effusion and the effects of the internal cooling configuration on film cooling, experimental and numerical studies are conducted on the effect of the relative position of the film holes and different orientation ribs on the film cooling performance. Three cases of the relative position of the film holes and different orientation ribs (post-rib, centered, and pre-rib) in two ribbed cross-flow channels (135° and 45° orientation ribs) are investigated. The film cooling performances are measured under three blowing ratios by the transient liquid crystal measurement technique. A RANS simulation with the realizable k-ε turbulence model and enhanced wall treatment is performed. The results show that the cooling effectiveness and the downstream heat transfer coefficient for the 135° rib are basically the same in the three position cases, and the differences between the local effectiveness average values for the three are no more than 0.04. The differences between the heat transfer coefficients are no more than 0.1. The “pre-rib” and “centered” cases are studied for the 45° rib, and the position of the structures has little effect on the film cooling performance. In the different position cases, the outlet velocity distribution of the film holes, the jet pattern and the discharge coefficient are consistent with the variation in the cross flow. The related research previously published by the authors showed that the inclination of the ribs with respect to the holes affects the film cooling performance. This study reveals that the relative positions of the ribs and holes have little effect on the film cooling performance. This paper expands and improves the study of the effect of the internal cooling configuration on film cooling and makes a significant contribution to the design and industrial application of the internal cooling channel of a turbine blade.

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