Fixed-area expansion devices are widely used in refrigerators, air conditioners, and heat pumps of up to 3.5 kW capacity with variable operating conditions. A fixed-area expansion device falls into one of three categories: an orifice, a short tube, and a capillary tube. The study of fixed-area expansion devices has been one of the main activities in the air-conditioning and refrigeration fields since the 1940s and has been intensified to meet the need to redesign refrigerators, air conditioners, and heat pumps to accommodate alternative refrigerants in the past two decades. This paper gives an overview of the literature on flow considerations for fixed-area expansion devices to provide readers with useful links to previous work. The main topics include mass flow rate through orifices, mass flow rate through short tubes, rating capillary tubes, metastable flow, two-phase friction pressure drop, and mathematical solution approaches. Readers should consult the original papers for more details.

Units: SI