Capillary is the throttling element for room air conditioners, with the advantages of simple operation and reliability, but with the ultimate disadvantage that the flow can't be adjusted automatically in accordance with the load. It can onlyeconomically operate under the unique set condition, while the actual operationcondition is always different from the set operation condition. Hence, there'sdecreased refrigerating capacity and energy efficiency ratio. When the expansion valve is used as the throttling element, the average refrigerating capacity can be increased above 15%, and the average energy efficiency ratiocan be increased above 13%.Features:1) Bidirectional operation: cooling and heating2) Airtight performance: annual leakage below 3g3) Compact size, low material consumption, low cost4) Easy to install, energy saving