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An experimental investigation is performed to study the effect of the inclination angle of air jets on heat transfer from a horizontal surface. A pair of inclined circular jets issuing from the straight pipes of length to diameter ratio of 40 is considered. The inclination angles of 0°, 10°, 20°, 30° 45°, and 60° are selected while the Reynolds number is varied from 10,000 to 40,000 based on a jet exit diameter. Jets to impingement plate distance (L/D) as well as the spacing distance (S/D) are changed from 2 to 8. The results of the temperature contours as well as the Nusselt number contours are illustrated to study the characteristics of heat transfer from a flat surface cooled by a pair of oblique jets. The experimental results show that the maximum magnitude of average heat transfer coefficient is achieved in the range of inclination angle from 10° to 20°. Empirical correlations are presented to predict the value of average Nusselt number as a function of Re , Pr , and θ. Moreover, a comparison between the values of average Nusslet number of the present study and those available in the literature is carried out. [ABSTRACT FROM AUTHOR]

Experimental study and sensitivity analysis on the heat transfer and pressure drop of a shell and helically coiled tube heat exchanger (SHCTHE) are carried out. The inclination angle ( ɵ ) is varied from the horizontal direction (0°) to vertical direction (90°) by a step of 10° and the coil Dean number ( De c ) is varied from 1540 to 3860. The results indicate that the effectiveness of SHCTHE ( ε ) at the vertical direction is higher than that of the horizontal direction by 26.3% and 23.1% at De c of 1540 and 3860, respectively. Maintaining the SHCTHE in the vertical direction reduces the coil pressure drop comparing with that of the horizontal one by 11% and 32.7% for De c of 3800 and 1800, respectively. Changing the direction of SHCTHE from the horizontal to vertical direction enhances the performance evaluation criteria ( PEC ) by 15.1% and 19.1% for De c of 3800 and 1800, respectively. The ANOVA statistical analysis shows that the effects of the independent variables such as the coil Dean number and the inclination angle of SHCTHE are significant on both the thermal performance and pressure drop. In addition, using multiple regression analysis, correlations are presented to evaluate Nu c and ΔP c as functions of D e c a n d θ with standard deviations of ±2% and ±6.6%, respectively. • The performance of shell and helically coiled tube heat exchanger was investigated. • Effect of the direction of SHCTHE on its performance was assessed. • Changing θ from 0° to 90° improved the Nu c by 12% for De c of 1800. • The sensitivity analysis was achieved using the Analysis of Variance. • Using regression analysis, new correlations were proposed to compute Nu c and ΔP c. [ABSTRACT FROM AUTHOR]