Which of the following modes of heat transfer does NOT require any physical contact between a warmer and a cooler substance?（）

A.A gate valve
B.A globe valve
C.Any check valve
D.Any needle valve

A.a shortage of compressor oil
B.warm food in the refrigerator
C.excessive condenser cooling water
D.a shortage of refrigerant

A.molecular fluid vibration
B.energy losses
C.wide pressure variations
D.mechanical damage to control valves