Air Side Performance Of Heat Exchangers Research Articles

Experimental and numerical investigation on air-side performance of fin-and-tube heat exchangers with various fin patterns

Air-side heat transfer and friction characteristics of five kinds of fin-and-tube heat exchangers, with the number of tube rows ( N = 12) and the diameter of tubes ( D o = 18 mm), have been experimentally investigated. The test samples consist of five types of fin configurations: crimped spiral fin, plain fin, slit fin, fin with delta-wing longitudinal vortex generators (VGs) and mixed fin with front 6-row vortex-generator fin and rear 6-row slit fin. The heat transfer and friction factor correlations for different types of heat exchangers were obtained with the Reynolds numbers ranging from 4000 to 10000. It was found that crimped spiral fin provides higher heat transfer and pressure drop than the other four fins. The air-side performance of heat exchangers with the above five fins has been evaluated under three sets of criteria and it was shown that the heat exchanger with mixed fin (front vortex-generator fin and rear slit fin) has better performance than that with fin with delta-wing vortex generators, and the slit fin offers best heat transfer performance at high Reynolds numbers. Based on the correlations of numerical data, Genetic Algorithm optimization was carried out, and the optimization results indicated that the increase of VG attack angle or length, or decrease of VG height may enhance the performance of vortex-generator fin. The heat transfer performances for optimized vortex-generator fin and slit fin at hand have been compared with numerical method.

Fin Pattern Effects on Air-Side Heat Transfer and Friction Characteristics of Fin-and-Tube Heat Exchangers with Large Number of Large-Diameter Tube Rows

Air-side heat transfer and friction characteristics of nine kinds of fin-and-tube heat exchangers, with a large number of tube rows (6, 9, and 12, respectively) and large diameter of tubes (18 mm), are experimentally investigated. The test samples consist of three types of fin configurations: plain fin, slit fin, and fin with delta-wing longitudinal vortex generators. The working fluid in the tube is steam. Results show that when the number of tube is larger than 6, the heat transfer and friction performance for three kinds of fins is independent of the number of tube rows, and slit fin provides higher heat transfer and pressure drop than the other two fins. The heat transfer and friction factor correlations for all the heat exchangers were acquired with Reynolds numbers ranging from 4000 to 10000. The air-side performance of heat exchangers with plain fin, slit fin, and longitudinal vortex-generator fin were evaluated under three sets of criteria, and the results showed that the heat exchanger with slit fin has better performance than that with vortex-generator fin, especially at high Reynolds numbers.

Air-Side Heat Transfer and Friction Correlations for Flat-Tube Louver-Fin Heat Exchangers

The objective of this study is to develop an accurate, reliable, and updated predictive model for the air-side performance of flat-tube louver-fin heat exchangers. Using the most comprehensive experimental database to date—consisting of 1030 heat-transfer and 1270 pressure-drop measurements, from nine independent laboratories for 126 sample heat exchangers—j- and f-factor correlations are developed to predict the air-side performance of heat exchangers. The database is analyzed, the form of the curve fits is explored, and the predictive performance of the correlations is evaluated. The j- and f-factor correlations predict the experimental data with rms errors of 11.5% and 16.1%, respectively. Multiple regressions for a locally linearized data model were used to estimate the confidence intervals and covariances of the regression constants. A comparison to prior correlations shows the proposed correlations to provide more accurate predictions and to span a much broader parameter space than prior work. Practical utility in design and optimization, and unavoidable limitations in developing such correlations are discussed.

Numerical investigation of fluid flow and heat transfer over louvered fins in compact heat exchanger

Numerical investigation of fluid flow and heat transfer characteristics over louvered fins and flat tube in compact heat exchangers is presented in this study. Three-dimensional simulations of single and double row tubes with louvered fins have been conducted. Simulations are performed for different geometries with varying louver pitch, louver angle, fin pitch and tube pitch and for different Reynolds number. Conjugate heat transfer and conduction through the fins are considered. The air-side performance of heat exchanger is evaluated by calculating Stanton number and friction factor. The results are compared with experiment and a good agreement is observed. The local Nusselt number variation along the top surface of the louver is calculated and effects of geometrical parameters on the average heat transfer coefficient is computed. Design curves are obtained which can used to predict the heat transfer and the pressure drop for a given louver geometry.