Which type of metering device is characterized by a small bore?

The capillary tube is characterized by its small bore, which is a crucial feature of its design. This metering device consists of a long, thin tube that allows refrigerant flow to pass through, creating a pressure drop necessary for refrigeration cycles. The small diameter of the capillary tube restricts the refrigerant flow based on the pressure differential between the high and low sides of the system. This characteristic makes the capillary tube an effective and simple device for applications where precise control of refrigerant flow is not as critical, such as in small refrigeration systems or appliances.

In contrast, the expansion valve and thermostatic expansion valve operate based on different principles and are typically larger in bore size to allow for control mechanisms that adjust flow based on temperature or pressure changes. These devices require more complex components and are designed for different applications than the capillary tube. The flow control valve also serves a different purpose by managing the flow of fluids rather than acting strictly as a metering device for refrigerants, further distinguishing it from the capillary tube.