Numerical investigation on thermal performance of absorption refrigeration system using MWCNT nanoparticle-enhanced 1-hexyl-3-methylimidazolium cation-based ionic liquids conducted in Renewable Energy Laboratory (Advisor: Prof: Honghyun Cho), Department of Mechanical Engineering, Chosun University, has been published in Applied Thermal Engineering (Top 9.17%, Impact factor 5.295). This study aimed to study the influence of MWCNT nanoparticle decorated 1-hexyl-3-methylimidazolium cation-based ionic liquids in an absorption refrigeration system. The examined room temperature ionic liquids (RTILs) based working pairs were pure RTILs ([HMIM][Bf4], [HMIM][TfO], [HMIM] [Pf6], and [HMIM][Tf2N]) as well as their MWCNT NEILs counterparts. To determine the effects of the MWCNT nanoparticles in the RTILs, the concentrations of the NEILs were changed in the range of 0–1 wt%. For ARS cycle simulations, detailed properties of both the RTILs and MWCNT NEILs were needed; therefore, their specific heats were experimentally obtained. Moreover, the solubility of the R1234 refrigerant in different ILs was predicted theoretically using the nonrandom two-liquid model based on the obtained properties of the RTILs and the MWCNT NEILs.