Abstract
R1234yf has been developed as an alternative refrigerant to R134a, which has been associated with global warming. The capillary tubes as expansion valves control the mass flow rate and balance system pressure in the refrigeration cycle. The present numerical model used the governing equations including the law of conservation of mass, momentum, and energy in a capillary tube. The mass flow rate of R1234yf decreased by 47.0% as the capillary tube length was increased from 1 to 4 m. As the inner diameter of the capillary tubes was changed from 1.3 to 1.7 mm, the mass flow rate of R134a and R1234yf increased by 117.9% and 121.0%, respectively. The mass flow rate of the R134a and R1234yf increased by 28.3% and 29.1% with subcooling increasing from 0 to $7^{\circ}C$. In addition, when the inlet temperature of the capillary tubes was changed from 35 to $60^{\circ}C$, the mass flow rate of R134a and R1234yf increased by 31.0% and 45.4%, respectively.
최근에 지구온난화 문제로 인하여 R134a 냉매에 대한 규제가 강화되면서 대체냉매로서 R1234yf 냉매가 개발되었다. 냉동사이클에서 팽창장치인 모세관은 유량제어와 압력조절의 역할을 한다. 본 연구에서는 모세관에 흐르는 냉매유동의 지배 방정식을 사용하여 R134a와 R1234yf 냉매에 대하여 해석적 연구를 수행하였다. 모세관 길이를 1-4 m로 변화시켰을 때 R1234yf 냉매의 질량유량은 47.0% 감소하였다. 모세관의 직경을 1.3-1.5 mm로 변화시켰을 때 R134a 냉매와 R1234yf 냉매의 질량유량은 각각 117.9%와 121.0% 증가하였다. 모세관 입구의 과냉도를 $0-7^{\circ}C$ 변화시켰을 때 R134a 냉매와 R1234yf 냉매의 질량유량은 28.3%와 29.1% 증가하는 것으로 나타내었고, 모세관 입구에서 운전조건을 $35-60^{\circ}C$로 변화시켰을 때 R134a 냉매는 31.0%, R1234yf 냉매는 45.4% 증가를 각각 나타내었다.