Final answer:
The correct term for a heat exchanger used only in warm weather, as part of an air conditioning system to dissipate heat, is a condenser. It functions by condensing refrigerant from a gas to a liquid through a heat transfer with the outside air.
Step-by-step explanation:
A heat exchanger used only in warm weather typically functions as part of an air conditioning system, where its main role is to dissipate heat to the outside environment. The correct terminology for this component is a condenser (option A). In a typical air conditioning cycle, an electrically driven compressor increases the temperature and pressure of the refrigerant gas and pushes it into the condenser coils. Here, given that the temperature of the gas is higher than the ambient outside temperature, a heat transfer occurs from the gas to the outside air, and the refrigerant condenses to a liquid. Subsequently, the liquid refrigerant is then cooled as it flows back through an expansion valve to the evaporator coils, where it is ready to absorb heat from the indoor environment once again. Hence, a heat exchanger used only in warm weather is referred to as a condenser.