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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]

• Fluid flow and thermal performances of PHE are investigated experimentally. • The effectiveness and NTU of PHE are improved with increasing Rr. • Pressure drop and pumping power are increased by increasing Rr. • SHR is improved with increasing surface roughness particularly at low Reynolds number. • Empirical correlations are proposed to predict SHR as a function of Rr and Re. In the present paper, an experimental study of the effectiveness and pumping power of plate heat exchanger (PHE) with rough surface was performed. The experiments were developed for different values of relative roughness, Rr, of 2.6 * 10−4 (smooth surface), 3.4 * 10−4, 7.5 * 10−4 and 9.8 * 10−4 for Reynolds number, Re, varied from 500 to 5000. The average heat transfer rate, Q avg , hence the effectiveness of PHE, ε , and number of transfer units, NTU , as well as pressure drop, Δp , consequently pumping power, P, and specfic heat rate, SHR, were estimated. The results show that Q avg and NTU are enhanced with increasing Rr ; while, they are decreased with increasing Re. At Re = 5000, the effectiveness of PHE with relative roughness of 3.4 * 10−4, 7.5 * 10−4 and 9.8 * 10−4 is greater than that of the smooth surface by 11.5%, 16.6% and 18.6%, respectively. Furthermore, Δp and P are increased by increasing Rr and Re. Moreover, at Re = 500, SHR is enhanced with increasing Rr and its improvements compared with the smooth surface are 39.5%, 23.4% and 6.9% for Rr of 3.4 * 10−4, 7.5 * 10−4 and 9.8 * 10−4, respectively. In addition, empirical correlations are proposed to estimate SHR as a function of Rr and Re with a standard deviation of 5.1%. [ABSTRACT FROM AUTHOR]

The three-fluid heat exchanger is a multi-stream heat exchanger that provides three streams at different temperatures for certain usage objectives. Recently, optimizing heat exchangers generally and three-fluid heat exchangers especially have received great attention in the energy field. The current study objective is to get the optimal mass flow rate of the three streams to minimize the entropy generation number and maximize effectiveness. Optimization is performed on the inserted coiled tube type for 24 cases with different usage objectives and different mass flow rate constraints. The optimization is done using an analytical approach for the temperature profiles and a regressed model for the overall heat transfer coefficients. Single-objective and multi-objective genetic algorithms are the optimization algorithms. The result shows that cooling the hot fluid is the most efficient usage objective; however, heating the intermediate-temperature fluid is the less efficient usage objective. Also, the study shows that the entropy generation number is dependent on the mass flow rate constraint. The maximum effectiveness of 0.693 occurs when the usage objective is cooling the hot fluid. In this case, the mass flow rate of the cold and the intermediate-temperature fluids are maxima while the mass flow rate of the hot fluid is minimum. The minimum entropy generation number 0.0486 occurs when the mass flow rate of the cold fluid is maximum while the mass flow rate of the hot fluid and intermediate-temperature fluid are minimal. [Display omitted] • Heat transfer of a three-fluid heat exchanger is investigated. • A model for optimizing the inserted coiled tube three-fluid heat exchanger is developed. • The maximum errors for the regression models of heat transfer coefficients are 1.72% and 2.81%. • The maximum effectiveness reached about 0.69323. [ABSTRACT FROM AUTHOR]