Strojniški vestnik - Journal of Mechanical Engineering 64(2018)2, 114-120 Received for review: 2017-11-16 © 2018 Journal of Mechanical Engineering. All rights reserved. Received revised form: 2018-01-19 DOI:10.5545/sv-jme.2017.5093 Original Scientific Paper Accepted for publication: 2018-02-09 *Corr. Author’s Address: University of Yalova, Faculty of Engineering, Turkey, mehmetdirek@hotmail.com 114 0 INTRODUCTION Even though R134a has low ozone depletion potential (ODP), its global warming potential (GWP) value is as high as 1300 [1]. Therefore, European Regulation No. 2006/40/EC and No. 517/2014 restrict the usage of HFCs which have GWP greater than 150 in MAC systems and other vapour compression refrigeration (VCR) systems [2] and [3]. Aprea et al. [4] experimentally investigated a refrigeration system using R1234ze(E) as a replacement of R134a. Total equivalent warming impact (TEW1) and life cycle climate performance indexes were found to be lower than R134a for all working conditions. In addition to low GWP values, R1234ze(E) has low flammability with regards considering safety issues [5]. Imamura et al. [6], performed experiments to elucidate fire hazards of R32 and R1234ze(E). They observed that ignition could be prevented using mechanical ventilation when the level of leakage is equal to the upper flammability limit (UFL). Table 1 shows that the vapour density of R1234ze(E) is 19 %, and the latent heat is 7 % lower when compared to R134a. R1234ze(E) has a low mass flow rate per unit volume of compression and thus a lower cooling capacity. Mota-Babiloni et al. [7] have identified the performance parameters of a refrigeration system, which uses R134a and R1234ze(E), as the functions of different evaporator and condenser temperatures. They observed that the R1234ze(E) has lower cooling capacity and COP values by 30 % and 9 %, respectively, in comparison compared to R134a. Leighton et al. [8] tested R1234ze(E) as an alternative to R134a in a refrigeration system. They found that R1234ze(E) has a lower cooling capacity and COP by 21.5 % and 7.9 %, respectively. Table 1. Refrigerant properties of R1234ze(E) and R134a [1] and [9] Property R134a R1234ze(E) ASHRAE safety classification A1 A2L ODP 0 0 GWP 1300 4 Critical temperature [K] 247.08 253.88 Critical pressure [kPa] 4059.28 3623.90 Vapor density [kg·m –3 ] 14.35 11.65 Liquid density [kg·m –3 ] 1295 1240 Latent heat of vaporization [kJ·kg –1 ] 198.72 184.28 Janković et al. [10] carried out a study in a VCR system and found that the cooling capacity of R1234ze(E) is 27 % lower, and the COP value is similar to that of R134a. They also observed that at higher compressor speeds, R1234ze(E) provides the same cooling capacity with R134a at the rates of 34 % to 39 %. Kabeel et al. [11] figured out the performance of the VCR cycle for the cases of R134a and R1234ze(E). They found that the R1234ze(E) The Effect of Internal Heat Exchanger Using R1234ze(E) as an Alternative Refrigerant in a Mobile Air-Conditioning System Direk, M. – Soylu, E. Mehmet Direk 1,* – Eren Soylu 2 1 University of Yalova, Faculty of Engineering, Turkey 2 University of Yalova, Institute of Science and Engineering, Turkey In this study, the use of R1234ze(E) refrigerant in an R134a-based mobile air-conditioning (MAC) system was experimentally investigated. Additionally, the effect of internal heat exchanger (IHX) on the performance of MAC was determined using R1234ze(E). Under the same conditions, we have tested and compared two different cases that use R1234ze(E) with and without an IHX by taking the performance of R134a as a reference. The inlet airflow temperatures of the evaporator and condenser were kept at 27 °C and 35 °C during the experiments, respectively. Performance parameters were determined using energy and exergy analysis. Compressor power was reduced by an average of 19 %, and the COP of R1234ze(E) were increased by an average of 4 % after activating the IHX. Moreover, it was determined that the value of exergy destruction of the system with R1234ze(E) was decreased by an average of 50 % when compared to R134a. Keywords: R134a, R1234ze(E), mobile air conditioning, coefficient of performance, internal heat exchanger Highlights • The performance of a MAC system using R134a and R1234ze(E) was tested. • The effect of IHX on the system performance was determined. • COP was increased by 4 % on average after IHX activated. • The exergy destruction value was found to be decreased by 50 % on average in the case of R1234ze(E).