What happens to pressure drop as the length of the capillary tube increases?

As the length of the capillary tube increases, the pressure drop also increases. This relationship is attributed to the principles of fluid dynamics, specifically how viscosity and friction play a role in the flow of refrigerants through narrow passages.

In a longer capillary tube, the refrigerant must travel a greater distance, encountering more surface area along the tube's walls. As the fluid moves, it experiences resistance due to friction, which causes energy loss in the form of pressure drop. The longer the tube, the more frictional resistance and, subsequently, the greater the drop in pressure.

This phenomenon is a critical factor in HVAC system design, as it can affect the efficiency and performance of the refrigerant flow in cooling systems. Understanding this aspect helps HVAC technicians properly size and select capillary tubes to ensure optimal system performance.