# Condensation Flow of Refrigerants Inside Mini and Microchannels: A Review
## 1 Introduction
### Environmental Impacts of Refrigerants
On the other hand, the GWP values of the blends are not negligibly low. Despite this, refrigerant mixtures maintain their importance because the undesirable properties of pure refrigerants, such as toxicity and/or flammability, can be reduced with refrigerant blends. When refrigerants are considered in terms of ozone depletion and global warming, HC refrigerants come to the fore. \begin{table}
\begin{tabular}{l c c c} \hline
**Refrigerant** & **Atmospheric Lifetime** & **GWP** & **ODP** \\ \hline CFC Refrigerants & & & \\ R11 & 45 & 4750 & 1 \\ R12 & 100 & 10,900 & 1 \\ R13 & 6440 & 14,400 & 1 \\ R114 & 300 & 10,000 & 1 \\ R115 & 1700 & 7370 & 0.6 \\ HCFC Refrigerants & & & \\ R22 & 12 & 1810 & 0.055 \\ R123 & 1.3 & 77 & 0.02 \\ R124 & 5.8 & 609 & 0.022 \\ R225 ca & - & 170 & 0.025 \\ R225 cb & - & 530 & 0.033 \\ HFC Refrigerants & & & \\ R23 & 270 & 14,800 & 0 \\ R32 & 4.9 & 675 & 0 \\ R125 & 29 & 3500 & 0 \\ R134a & 14 & 1430 & 0 \\ R141b & 9.3 & 725 & 0.11 \\ R142b & 17.9 & 2310 & 0.065 \\ R143a & 52 & 4470 & 0 \\ R152a & 1.4 & 124 & 0 \\ R227 ea & 34.2 & 3220 & 0 \\ \hline \end{tabular}
\end{table} 
Table 1: Environmental effects of pure refrigerants [10; 12; 13]. Following extensive deliberations and negotiations, the Montreal Protocol was formally adopted in 1987 [14]. This protocol, along with the Vienna Convention for the Protection of the Ozone Layer, is committed to safeguarding the Earth's ozone layer [15]. With participation from 196 parties, these agreements represent the most extensively ratified treaties in the history of the United Nations. Their collective efforts have resulted in reductions exceeding 97% of global consumption of regulated ozone-depleting sub \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Refrigerant** & **Atmospheric Lifetime** & **GWP** & **ODP** \\ \hline R236 fa & 240 & 9810 & 0 \\ R245 ca & 6.2 & 693 & 0 \\ R245 fa & 7.6 & 1030 & 0 \\ HC Refrigerants & & & \\ R290 & 0.41 & \(\sim\)20 & 0 \\ R600 & 0.018 & \(\sim\)20 & 0 \\ R600a & 0.019 & \(\sim\)20 & 0 \\ R601 & - & \(\sim\)20 & 0 \\ R601a & 0.01 & \(\sim\)20 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: \(Cont.\)  
\begin{table}
\begin{tabular}{l c c c} \hline \hline
**Refrigerant** & **Blends (Mass Percentage)** & **GWP** & **ODP** \\ \hline \hline \multicolumn{4}{l}{Zeotrope Blends} \\ R401A & R-22/152a/124 (53/13/34) & 1200 & 0.033 \\ R401B & R-22/152a/124 (61/11/28) & 1300 & 0.036 \\ R401C & R-22/152a/124 (33/15/52) & 930 & 0.02  
stances [16]. With international regulations limiting the use of CFCs and HCFCs, refrigerant blends emerge as potential alternatives to these substances. While CFCs and HCFCs boost favourable thermodynamic properties, only a select few refrigerants can match their performance. Nevertheless, refrigerant blends offer a viable thermodynamic alternative to CFCs and HCFCs while also being environmentally conscious materials. The Kyoto Protocol, established in Kyoto, Japan, on 11 December 1997, and enforced on 16 February 2005, aims to combat climate change and mitigate global warming [14]. Serving as an international accord associated with the United Nations Framework Convention on Climate Change, its notable aspect lies in imposing mandatory emission reduction targets on 37 industrialised nations and the European community to curb greenhouse gas (GHG) emissions [8]. Fluorinated greenhouse gases (F-gases), primarily HFCs, are widely utilised as refrigerants in household refrigerators and commercial low-temperature process technologies in mobile air conditioning systems [17]. However, these F-gases significantly contribute to global warming, as recognised by the United Nations Framework Convention on Climate Change and the Kyoto Protocol [18]. Consequently, the EU implemented F-gas regulations in 2006 to manage F-gas emissions and mitigate their environmental impact, given their high global warming potential (GWP) values [19].