## 5 Conclusions
**Nomenclature**  
Nu refrigerant nusselt number  
\(\rm{Re_{Dh}}\) hydraulic diameter Reynolds number  
\(\rm{Re_{I}}\) liquid refrigerant Reynolds number  
\(\rm{Re_{g}}\) gas Reynolds number  
\(\rm{Re_{ea}}\) Reynolds number on the air side  
\(\rm{Re_{ef}}\) refrigerants Reynolds number  
\(\rm{Re_{eq}}\) equivalent Reynolds Number  
\(\rm{Re_{w}}\) cold water Reynolds number  
\(\rm{Pr}\) Prandtl number  
\(\rm{Pr_{I}}\) liquid refrigerant prandtl number  
\(\rm{Pr_{a}}\) air side prandtl number  
\(\rm{D_{h}}\) hydraulic diameter [m]  
\(\rm{G_{r}}\) refrigerant mass flux [kg/(m\({}^{2}\times\rm{K}\))]  
\(\rm{H_{rp}}\) two-phase heat transfer coefficient [W/(m\({}^{2}\times\rm{K}\))]  
x refrigerant dryness  
\begin{tabular}{l l} \(\mathrm{v_{r}}\) & refrigerant flow rate [m \(\times\) s\({}^{-1}\)] \\ L & the cell length [m] \\ \(\mathrm{\rho_{r}}\) & density of refrigerant [(kg \(\times\) m\({}^{3}\))\({}^{-1}\)] \\ \(\mathrm{A_{fe}}\) & effective circulation cross-sectional area [m\({}^{2}\)] \\ \(\mathrm{A_{s}}\) & windward area [m\({}^{2}\)] \\ \(\mathrm{\omega}\) & ripple length \\ Ac & effective circulation area [m\({}^{2}\)] \\ \(\mathrm{G_{eq}}\) & equivalent mass flow density [m\({}^{3}\)\(\times\) s\({}^{-1}\)] \\ \(\mathrm{h_{fg}}\) & latent heat of vaporization [J \(\times\) kg\({}^{-1}\)] \\ \(\mathrm{m_{j}}\) & refrigerant mass of unit j [kg] \\ \(\mathrm{\rho_{r}}\) & refrigerant density [(kg \(\times\) m\({}^{3}\))\({}^{-1}\)] \\ \(\mathrm{\mu_{1}}\) & saturated liquid viscosity [Pa \(\times\) s] \\ \(\mathrm{\rho_{1}}\) & saturated liquid phase density [(kg \(\times\) m\({}^{3}\))\({}^{-1}\)] \\ \(\mathrm{P_{r}}\) & Pcrit refrigerant pressure [Pa] \\ \(\mathrm{h_{a}}\) & air side heat transfer coefficient [W \(\times\) (m\(2\times\) K)\({}^{-1}\)] \\ \(\mathrm{I_{br,in}}\) & unit refrigerant inlet enthalpy [J \(\times\) kg\({}^{-1}\)] \\ \(\mathrm{P_{H}}\), \(\mathrm{P_{F}}\) & heated perimeter channel wet week [m] \\ \(\mathrm{\rho_{tp,j}}\) & refrigerant density in two-phase region [(kg \(\times\) m\({}^{3}\))\({}^{-1}\)] \\ \(\mathrm{T_{w,in,j}}\) & cold water inlet temperatures of the j th unit [K] \\ \(\mathrm{A_{g}}\) & cross section of the ascending or descending pipe [m\({}^{2}\)] \\ \(\mathrm{H}\) & height difference between evaporator and condenser [m] \\ \(\mathrm{M_{g}}\) & mass of refrigerant in the ascending or descending pipe [kg] \\ \(\mathrm{\Lambda}\) & liquid refrigerant coefficient of thermal conductivity [W \(\times\) (m K)\({}^{-1}\)] \\ \(\mathrm{\Phi_{12}}\) & friction multiplier \\ \(\mathrm{\beta}\) & ripple dip [\({}^{\circ}\)] \\ \(\mathrm{m_{r}}\) & refrigerant flow [kg \(\times\) s\({}^{-1}\)] \\ \(\mathrm{\alpha}\) & section gas content \\ E, \(\mathrm{F}\) & enhancement factor and inhibitory factor \\ \(\mathrm{m_{w}}\) & cold water flow [kg \(\times\) s\({}^{-1}\)] \\ \(\mathrm{\Gamma_{wc,j}}\) & cold water side temperature of j th unit [K] \\ \(\mathrm{\lambda}\) & along-path resistance coefficient \\ \(\mathrm{\zeta}\) & local resistance coefficient \\ \(\mathrm{V/\mu_{r}}\) & refrigerant flow rate [m\({}^{3}\)\(\times\) s\({}^{-1}\)] \\ \(\mathrm{Q_{cj}}\) & unit refrigerant heat exchange capacity [W] \\ \(\mathrm{L_{g2}}\) & length of riser or descender [m] \\ \(\mathrm{\delta}\) & area ratio \\ \(\mathrm{\mu_{r}}\) & refrigerant dynamic viscosity [Pa \(\times\) s] \\ \(\mathrm{q^{*}H}\) & effective heat flux density [W/m\({}^{2}\)] \\ Bo & Bond number \\ \(\mathrm{X_{tt}}\) & Marty number \\ f & friction coefficient \\ \(\mathrm{T_{wcj}}\) & unit refrigerant side wall temperature [K] \\ \(\mathrm{A_{r}}\) & micro-element heat exchange area [m\({}^{2}\)] \\ B/b & ripple amplitude [m\({}^{2}\)] \\ \(\mathrm{\Phi}\) & area to expand coefficient \\ G & actual mass flow [m\({}^{3}\)\(\times\) s\({}^{-1}\)] \\ Q & heat flux density [(W \(\times\) m\({}^{2}\))] \\ \(\mathrm{M_{r}}\) & refrigerant mass flow [J \(\times\) kg\({}^{-1}\)] \\ \(\mathrm{L_{g}}\) & length of riser or descender [m] \\ \(\mathrm{T_{rc,j}}\) & unit refrigerant temperature [K] \\ \(\mathrm{\mu_{g}}\) & saturated vapor phase dynamic viscosity \\ \(\mathrm{\mu