A MCDM Methodology to Determine the Most Critical Variables in the Pressure Drop and Heat Transfer in Minichannels

Eloy Hontoria,Alejandro López-Belchí,Nolberto Munier,Francisco Vera-García

doi:10.3390/en14082069

Eloy Hontoria, Alejandro López-Belchí + Show 2 more

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https://doi.org/10.3390/en14082069

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Abstract

This paper proposes a methodology aiming at determining the most influent working variables and geometrical parameters over the pressure drop and heat transfer during the condensation process of several refrigerant gases using heat exchangers with pipes mini channels technology. A multi-criteria decision making (MCDM) methodology was used; this MCDM includes a mathematical method called SIMUS (Sequential Interactive Modelling for Urban Systems) that was applied to the results of 2543 tests obtained by using a designed refrigeration rig in which five different refrigerants (R32, R134a, R290, R410A and R1234yf) and two different tube geometries were tested. This methodology allows us to reduce the computational cost compared to the use of neural networks or other model development systems. This research shows six variables out of 39 that better define simultaneously the minimum pressure drop, as well as the maximum heat transfer, saturation pressure fluid entering the condenser being the most important one. Another aim of this research was to highlight a new methodology based on operation research for their application to improve the heat transfer energy efficiency and reduce the CO2 footprint derived of the use of heat exchangers with minichannels.

Highlights

In order to increase the efficiency in modern refrigeration mini channels condensers, there is a need to determine two conflicting output variables: the minimum pressure drop and the maximum heat transfer
Condensers and evaporators with minichannels tubes are very attractive technologies to achieve the third item of the previous list, since they present extremely high heat transfer coefficient and higher area to surface ratios than conventional tubes or plain tubes
The parameter “Hydraulic diameter” is repeated but with a different label (29 and 5). This is because this parameter directly influences both processes, pressure drop and heat transfer

Summary

Introduction

In order to increase the efficiency in modern refrigeration mini channels condensers, there is a need to determine two conflicting output variables: the minimum pressure drop and the maximum heat transfer. This improvement has a direct impact in energy savings, as well as in the price of equipment, contributing to sustainability. There are several ways to reduce gas emissions and energy consumption:. Due to its reduced volume, compared with conventional tubes technology, minichannels heat exchangers are the ideal devices to work with flammable or toxic refrigerants or to reduce the gas emissions associated with a leakage [5]

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