1st sentence " It can be seen that increasing the ambient temperature shows slightly decreasing trend for both refrigerants under consideration". - I assume this statement about refrigeration cycle if so - they try to explain that refrigerant after the compressor will have higher temperature (ex: 250oC) than atmospheric temperature until just before the expansion valve. now heat transfer from that pipe to atmosphere mainly depend on temperature difference between both states. If atm temperature is let say 20oC and 35oC is two cases, convection and radiation heat transfer will be higher between highest temperature difference. if temperature rises transfer of energy is less

2nd sentence "This is because the system carried even smaller amount of heat energy to be rejected when the ambient temperature becomes lowered and this caused the heat rejection rate to be lowered, hence the heating effect also lowered."- this case if you lower the atm temperature from 35 to 20 you can remove more energy even though you had less energy (now inside the pipe refrigerant temperature drop to lets say 40oC)

3rd sentence- i guess they try to talk like this trend they got not assuming there is no pressure drop, they also took that also into account when they did this experiment or analysis

The value of the Thermal properties refrigerants are function of the working temperature (or room temperature), properties as the Specific Heat Capacity, thermal conductivity and the density of the fluid also depends on the room temperature.

Dear Mr. Ravi Raj Ladha

Can you please edit the question to be more clear?

The ambient temperature affect the refrigeration system from to sides, the first it is directly affect the condensation process specially for air cooled condensers, the second side it is indirectly affect to increase the load on the evaporator if assuming more heat will transfer to the cooled environment.

best wishes!