The liquid refrigerant goes from the filter/dryer to the expansion valve, which is located at the entrance to the evaporator. The expansion valve sprays the liquid refrigerant through a small opening into the evaporator. The small opening of the expansion valve creates a transition from high pressure to low pressure, so the liquid refrigerant expands into a gas and gives up its heat as a result of the conversion from liquid to gas. Think of water going through a garden sprayer set for mist: There's high pressure (water) going into the sprayer, and it empties into the low-pressure (our atmosphere) almost a a gas (mist). The pressure drop across the expansion valve actually causes the refrigerant to boil (when a liquid boils, it changes phase from a liquid into a gas and releases heat).
The expansion valve is in the aquarium, just to the right (as viewed from the front of the car) of the dryer cylinder.
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