Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman Comparative study of the conventional types of heat and mass exchangers to achieve the best design of dew point evaporative coolers at diverse climatic conditions Ali Sohani, Hoseyn Sayyaadi ⁎ , Negar Mohammadhosseini Optimization of Energy Systems’ Installations Lab., Faculty of Mechanical Engineering-Energy Division, K.N. Toosi University of Technology, P.O. Box 19395-1999, No. 15-19, Pardis St., Mollasadra Ave., Vanak Sq., Tehran 1991 943344, Iran ARTICLE INFO Keywords: Best heat and mass exchanger Dew-point (M-cycle) indirect evaporative coolers Life-cycle cost analysis Multi-objective optimization Thermal comfort conditions Water consumption ABSTRACT The objective of this research is a comparative analysis of various kinds of heat and mass exchangers of dew point indirect evaporative cooler. Considering three key performance parameters of an evaporative cooler, namely life-cycle cost, annual water consumption and the annual average of the coefficient of performance as objective functions, the best design of two popular types of the dew-point evaporative cooler (counter-re- generative and cross configurations) for employing in small-scale residential buildings was found through a multi-objective optimization approach. Both operational and geometric characteristics of the coolers were se- lected as the design (decision) variables while proper constraints such as thermal comfort were imposed. Afterward, between the optimized counter-regenerative and cross configurations, the foremost one was selected for representative cities of four diverse groups within the Köppen-Geiger climate classification system. It was found that in very hot and dry areas, the counter-regenerative configuration was the ideal choice while in other investigated climates, using cross configuration was a better alternative. Moreover, the results showed that in comparison to the base case conditions by using the best-optimized configurations, 64.4, 86.4, and 1039.0% improvements in life-cycle cost, the annual water consumption, and the annual average of the coefficient of performance were achieved, respectively. 1. Introduction During recent years, dew point indirect evaporative cooling system (DPIEC) has occupied an important role in air-conditioning system technologies. The system was originally patented and developed by Valery Maisotsenko [1–3]. Therefore, the system is also known as the Maisotsenko (M-cycle) indirect evaporative cooling system [4,5]. Mai- sotsenko (M-cycle) indirect evaporative coolers (MCIECs) not only provide the supply air temperature below the wet-bulb close to dew point temperature by the highest efficiency but also consume much lower electricity than the similar vapor compression systems [6]. Ad- ditionally, MCIECs are an environmental option for the conventional vapor compression system [7]. Providing cooled air without adding moisture and wet-bulb effectiveness of higher than 100% could be counted as the main advantages of MCIECs compared to direct eva- porative cooling systems (DECs) and other indirect evaporative cooling systems (IECs) [8]. There are different versions of the air flow ar- rangement in the M-cycle heat and mass exchangers [9]. Fig. 1a re- presents a counter-flow regenerative heat and mass exchanger with partial extraction of air (also known as regenerative heat and mass exchanger). Moreover, Fig. 1b shows a cross-flow heat and mass ex- changer. Each of these illustrated figures is one of the different types of air flow arrangement. Counter-flow regenerative and cross-flow M-cy- cles (CoFRMC and CrFMC) are the major popular developed kinds of heat and mass exchangers of MCIECs [10]. There have been two main approaches by which the performance of MCIECs has been analyzed: conducting experiments and developing analytical or numerical models. Conducting experiments is a method in which the researchers have performed a number of experiments and then they have reported and interpreted the results [11–14]. For in- stance, Xu et al. [11] investigated the performance of an innovative CoFRMC, in which high-quality wet material layer and intermittent water distribution system were employed. In another study, Kashif Shahzad et al. [12] tested an integrated cooling system which com- posed of solid desiccant and CrFMC. Moreover, Duan et al. [13] found the potential of electrical energy saving of a CoFRMC at diverse climatic conditions of China using an experiment-based evaluation. Khalid et al. [14] also studied the performance of a CrFMC under low inlet air https://doi.org/10.1016/j.enconman.2017.12.042 Received 1 November 2017; Received in revised form 29 November 2017; Accepted 12 December 2017 ⁎ Corresponding author. E-mail addresses: alisohany@yahoo.com, asohani@mail.kntu.ac.ir (A. Sohani), sayyaadi@kntu.ac.ir (H. Sayyaadi). Energy Conversion and Management 158 (2018) 327–345 0196-8904/ © 2017 Elsevier Ltd. All rights reserved. T