Answer to Question 1
In the air handling unit, air passes through the filters, preheater, cooling coil, heating coil, reheater, and finally the fan. This type of system is referred to as a draw-through system because the fan is located after the coils and draws the air across them. A blow-through system would locate the fan before the coils.
Answer to Question 2
Refrigerant is drawn into the tip and travels between an infrared light source and an infrared light sensor. When refrigerant enters the tip, it reflects the infrared radiation and blocks the sensor from seeing it, much like a cloud can block the sun on a cloudy day.
Lymphatic system.
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