energies Communication Performance of Pure Crossflow Heat Exchanger in Sensible Heat Transfer Application Karthik Silaipillayarputhur * and Tawfiq Al-Mughanam   Citation: Silaipillayarputhur, K.; Al-Mughanam, T. Performance of Pure Crossflow Heat Exchanger in Sensible Heat Transfer Application. Energies 2021, 14, 5489. https:// doi.org/10.3390/en14175489 Academic Editor: Aliyu Aliyu Received: 13 June 2021 Accepted: 25 August 2021 Published: 2 September 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Department of Mechanical Engineering, King Faisal University, Al Ahsa 31982, Saudi Arabia; talmughanam@kfu.edu.sa * Correspondence: ksilai@kfu.edu.sa; Tel.: +966-504-538-025 Abstract: All process industries involve the usage of heat exchanger equipment and understanding its performance during the design phase is very essential. The present research work specifies the performance of a pure cross flow heat exchanger in terms of dimensionless factors such as number of transfer units, capacity rate ratio, and heat exchanger effectiveness. Steady state sensible heat transfer was considered in the analysis. The matrix approach that was established in the earlier work was used in the study. The results were depicted in the form of charts, tables, and performance equations. It was observed that indeterminately increasing the number of transfer units past a threshold limit provided very marginal improvement in the performance of a pure cross flow heat exchanger. Likewise, flow pattern in a heat exchanger is usually assumed either as mixed or unmixed. However, due to various operating conditions, partially mixed conditions do exist. This work considers partially mixed conditions in the tube side of the heat exchanger. The correction factor for heat exchanger effectiveness was developed to accommodate partially mixed flow conditions in the pure cross flow heat exchanger. Keywords: pure cross flow heat exchanger; design graphs; correction factors 1. Introduction All process and manufacturing plants have a lot of heat exchanger equipment. Heat exchanger (HX) is an equipment used to transfer heat between two or more fluids, wherein the fluids are separated by a solid wall. Two fluid heat exchangers are quite common and are employed in several applications. There are several kinds of heat exchangers available in the market. Heat exchangers can be classified based on the construction and flow arrangement. Cross flow heat exchanger, shell and tube heat exchanger, double pipe heat exchanger, and plate heat exchanger are all commonly used in industries. The choice of heat exchanger depends on the application, operating conditions, etc. In a cross flow heat exchanger, two fluids travel perpendicular to each other and thereby the name cross flow. Cross flow heat exchangers are popularly used for gas to liquid heat transfer applications where the gas is on the external side and the liquid is on the tube side of the heat exchanger. Most cross flow heat exchangers are finned tube heat exchangers. Fins enhance the surface area and these in turn enhance heat transfer. In most sensible heat transfer applications, the external fluid, which is usually gas, is treated as unmixed flow, while the tube side fluid, which is usually liquid, is treated as mixed flow. In unmixed flow, the fluid temperature varies in x- and y-directions, whereas in mixed flow, the fluid temperature varies only along the direction of flow, i.e., x-direction. Researchers over time have come up with various methodologies for designing and analyzing the sensible performance of heat exchangers. The most common methodologies are effectiveness (ε) and number of transfer units (NTU) approach, log mean temperature difference (LMTD) approach, P-NTU approach, matrix approach, and many more. In this work, ε-NTU approach combined with a matrix approach shall be used. It must also be noted that, for steady state sensible heat transfer, the heat exchanger performance can be Energies 2021, 14, 5489. https://doi.org/10.3390/en14175489 https://www.mdpi.com/journal/energies