OPTIMAL DESIGN OF DOUBLE-PIPE HEAT EXCHANGERS, COMPARISONS Petrik Máté 1 , Dr. Szepesi L. Gábor 2 , Prof. Dr. Jármai Károly 3 1 PhD student, University of Miskolc Department of Chemical Machinery 2 associate professor, University of Miskolc Department of Chemical Machinery 3 professor, University of Miskolc Department of Chemical Machinery ABSTRACT Heat exchangers are used in industrial and household processes to recover heat between two process fluids. This paper shows numerical investigations on heat transfer in a double pipe heat exchanger. The working fluids are water, and the inner and outer tube was made from carbon steel. There are several constructions which able to transfer the requested heat, but there is only one geometry which has the lowest cost. This cost comes from the material cost, the fabrication cost and the operation cost. These costs depend on the material types and different geometric sizes, for example inner pipe diameter, outer pipe diameter, length of the tube. The performance of the heat exchanger and the pressure drop are in a close interaction with the geometry. Optimum sizes can be calculated from the initial conditions (when one of the process fluid inlet and outlet temperature and the flow rate is specified). The correlations to the Nusselt number and the friction data come from experimental studies. [1] [2] Keywords Double-pipe heat exchanger, Heat transfer, Optimization, Comparisons LIST OF SYMBOLS Latin letters A Area (m 2 ) C Cost ($) c Heat capacity (J·kg -1 ·K -1 ) d Diameter of inner pipe (m) D Diameter of outer pipe (m) f Friction factor (-) k Overall heat transfer coefficient (W·m -2 ·K -1 ) L Tube length (m) LMTD Logarithmic mean temperature difference (°C) m mass flow (kg·s -1 ) Nu Nusselt number (-) Pr Prandtl number (-) Q Heat performance (W) Re Reynolds number (-) T Temperature (°C) v velocity (m s -1 ) Greek letters α Individual heat transfer coefficient (W·m -2 ·K -1 ) Δp Pressure drop (Pa) DOI: 10.26649/musci.2017.067