Final answer:
The correct type of shutoff valve used for controlling flow in a vertical refrigerant line is a globe valve. This valve offers good throttling capabilities and precise flow control, making it suitable for refrigerant applications.
Step-by-step explanation:
The type of shutoff valve used to control flow on a vertical length of refrigerant line is a globe valve. Globe valves are designed for throttling service and provide a greater degree of flow control compared to other types of valves. They commonly have a spherical body with an internal baffle that splits the inside cavity. A moveable disk-type element and a stationary ring seat in a generally spherical body are the key components enabling the valve to modulate the flow of refrigerant.
Globe valves are especially suitable for services that require frequent operation and throttling. When a globe valve is used in a vertical position, it is particularly effective in maintaining and regulating high pressure drops without the risk of damage. The design of the globe valve allows for a good seal when closed and precise control when opened, which is essential for the delicate process of managing refrigerant flow in systems such as air conditioning or refrigeration units.