Experimental Investigation of the Heat Transfer and Pressure Drop inside Tubes and the Shell of a Minichannel Shell and Tube Type Heat Exchanger

Abstract

This paper presents an experimental study on a shell and tube mini heat exchanger (STMHE). The STMHE consisted of seven tubes in a triangular arrangement, with an 0.8 mm inner diameter and 1.0 mm outer diameter. The heat exchanger shell had an inner diameter of 11 mm, and the heat exchanger had no baffles. For the adopted operating conditions, the Reynolds number on the tube side varied in the range of 300-3000, and 2000-12,000 on the shell side. The aim of this study was to determine pressure drop values during fluid flow and Nusselt number correlations for the heat transfer. A new method based on optimisation was used to derive the equations for calculating the heat transfer coefficients. It allowed the determine of the correlation equations for the heat transfer coefficients simultaneously for both sides of the heat exchanger. The obtained correlations yielded overall heat transfer coefficient values that, in most cases, did not differ by more than ±10% from those determined experimentally. The experimentally determined critical Reynolds number value for the flow inside the tubes was equal to Recr = 1160. The Darcy friction factors correlated well with the classical laminar flow correlation and with the Blasius correlation for turbulent flow. The derived correlations for the Nusselt number were best aligned with the Sieder-Tate, Gnielinski, and Kozioł correlations for tube side laminar flow, turbulent flow, and shell flow, respectively. Good agreement between the results obtained using the experimentally derived correlations and the correlations available in the literature confirms the effectiveness of the used optimisation-based method.