# Investigation of the Environmentally-Friendly Refrigerant R152a for Air Conditioning Purposes
## 1 Introduction
However, they found the R290 to be the most efficient working fluid but they highlighted its high flammability and the need for a stronger electrical motor, two factors which make it unsuitable for a direct drop-in alternative of R134a. They finally concluded that the R152a and the R1234 vf are the most promising choices for substituting the R134a. Moreover, it can be said that [PERSON] et al. [16] stated that the use of the R152a can be performed with the use of a secondary loop for safety reasons and for facing the flammability issues. The use of R152a in cascade configurations with CO2 in the low stage is a promising choice which has also been examined. [PERSON] et al. [17] proved that the substitution of R134a refrigerant with R152a is possible in a cascade cycle with CO2. They performed experimental work and they found similar performance with both configurations and also they stated that the system had worked about two months without problems after the use of R152a. In another work, [PERSON] et al. [18] found that the use of R152a in a cascade system with CO2 is more efficient than the use of R134a/CO2 and R124/CO2 cascade systems. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Working Fluids** & **Classification** & **GWP** & \
\begin{tabular}{c} **ASHRAE** \\ **GROUP** \\ \end{tabular} &
\begin{tabular}{c} **Cost** \\ **(S/kg)** \\ \end{tabular} & **Limitations** \\ \hline R134a & HFC & 1120 & A1 & 5.3 & High GWP \\ R404a & HFC & 3922 & A1 & 3.5 & High GWP \\ R152a & HFC & 138 & A2 & 1.5 & Medium flammability, \\  & & & & Low GWP \\ R32 & HFC & 677 & A2L & 3.0 & Low flammability, \\  & & & & Medium GWP \\ R1234 yf & HFO \(<\)1 & A2L & 88 & Low flammability, \\  & & & & Stability issues \\ R1234 ze & HFO \(<\)1 & A2L & 90 & Low flammability, \\  & & & & Stability issues \\ R717 (NH\({}_{3}\)) & Natural refrigerant & \(<\)1 & B1 & 1.5 & Toxicity \\ R744 (CO\({}_{2}\)) & Natural refrigerant & 1 & A1 & 0.7 & Low COP \\ R290 (Propane) & HC (Natural refrigerant) & 3 & A3 & 1.3 & High flammability \\ R600a (iso-butane) & HC (Natural refrigerant) & 4 & A3 & 2.0 & High flammability \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Refrigerants and their characteristics [7; 8; 9]. GWP: global warming potential; COP: coefficient of performance. The previous literature review indicates that the R152a is one of the most promising refrigerants for the future refrigeration machines. The existing studies show high performance and good compatibility with the existing installations. Therefore, there is a need for deeper investigation of this working fluid. In this direction, this study is a detailed analysis of a cooling system with R152a in order to determine its performance and its cooling capacity in different operating conditions. The novelty of this investigation is based on the different examined operating scenarios and on the development of a regression model for the prediction of the system performance. Moreover, it has to be said that there is a lack of studies about the investigation of R152a in the cooling system for the building sector. This work is conducted with a developed model in Engineering Equation Solver (EES) [19] which is validated using literature data [20].