The natural convection air cooled condensers are used in

Natural convection air-cooled condensers find applications in various cooling systems. The correct option is All of these, which means that they are used in domestic refrigerators, water coolers, and room air conditioners.

Natural convection refers to the heat transfer process where the movement of fluid (air, in this case) is driven by density differences due to temperature variations. Air-cooled condensers utilize natural convection to dissipate heat from the refrigerant to the surrounding air.

Therefore, in the context of the question, natural convection air-cooled condensers are utilized in domestic refrigerators, water coolers, and room air conditioners.