Natural convection heat transfer performance of additively manufactured tube bundle heat exchangers with novel fin design

Abstract

We studied the heat transfer of finned heat exchanger configurations with a novel design. These novel fin designs use integrated pins to enhance the heat conduction from the fin base to the fin tip as well as the air-side heat transfer on the fin surface. Oval tubes with conventional circular plain fins (CPF) as well as novel circular integrated pin fins (CIPF) and serrated integrated pin fins (SIPF) were additively generated by a Selective Laser Melting (SLM) process and installed at the bottom of a 6.5 m long chimney. All heat exchanger designs were tested in a 2-row and 3-row configuration with Rayleigh numbers between 25,000 and 120,000. We found the average Nusselt number of SIPF to be higher and the Nusselt number of the CIPF to be lower than for the CPF. Moreover, the 2-row configuration achieved a higher Nusselt number compared to the 3-row configuration for all heat exchanger designs. The analysis of the individual tube rows showed the highest Nusselt numbers at the first tube row and the lowest one at the last tube row for both configurations. However, for the SIPF the difference between the first and second tube row is smaller compared to the CPF and CIPF. In order to evaluate the compactness of the heat exchanger, the volumetric heat flux density was considered. Similar to Nusselt number the volumetric heat flux density enhanced for the SIPF and reduced for the CIPF compared to the conventional design. Also the 2-row configuration reached greater thermal performance compared to the 3-row configuration. Additionally, the volume and the surface area of the heat exchanger are 6.9% and 30.7% lower for the SIPF compared to the CPF. The experimental data were used to develop an empirical heat transfer correlation between Nusselt number, Rayleigh number, fin design and tube row number.

Inhomogeneous flow model of natural convection, entropy generation, and heatlines visualization in wavy I‐shaped enclosure with rectangular heater

“…Due to an obvious increment of energy prices, it is important to control the heat transfer within numerous thermal devices such as heat exchangers, 1 thermal solar concentrators, 2 petroleum industry, 3 and melting and solidification processes, 4 and so forth. There are different methods to control heat transfer such as using nanofluids, porous mediums or changing the enclosure shape by corrugating its wall.…”

MHD Flow of a Hybrid Nano-Fluid in a Triangular Enclosure with Zigzags and an Elliptic Obstacle

“…Convection has always been the primary focus of research [1] for a variety of heating and cooling engineering systems. A modification of the geometrical shape of the system [2,3] was recently agreed upon among researchers in order to achieve spectacular optimization of the heat-transfer performance, from circular [4] and square geometries [5] to non-square geometries [6][7][8][9] (triangular, trapezoidal, etc.)…”

An Experimental Investigation of Increasing the Thermal Efficiency of a Finned Tube Heat Exchanger by Using the Chimney Effect

“…Furthermore, the average heat-transfer coefficient for a bundle of pipes was 1.4 times higher than for a single pipe. Unger et al [17], in their work, investigated how the average heat-transfer coefficient under free convection conditions evolves for a two-and three-row heat exchanger placed in a chimney of 6.5 m in height. The study was carried out for three different types of fins, that is, circular plain fins; circular integrated pin-fins, and serrated integrated pin-fins.…”