As we can see in Figure 8, the heat flux was increased as increasing of operation temperature that supplied by hot water. While the operating temp was increased, at the same time the vapor pressure to increasing and then flow rapidly toward the condenser. Maximum Heat flux (at inclined angle =90 deg.) was 9.42, 13.36 and 16.71 kW/m2 of operating temperature 60, 70 and 80 oC, respectively.