초록
본 연구에서는 상용 냉동 공조기기에서 사용하고 있는 휜-관 열교환기에서 R22와 이의 대체냉매로 채용하고 있는 R134a 압력강하와 열전달 특성에 대해 실험적으로 연구하였다. 실험은 입구온도 $60^{\circ}C$, 질량유량 $150,\;200,\;250\;kg/m^{2}s$의 범위에 대해 수행하였다. 이때 공기의 유입조건은 전구온도 $35^{\circ}C$, 상대습도 40%, 공기유속은 $0.68{\sim}1.6m/s$이다. 실험 결과 응축기 출구의 과냉도를 $5^{\circ}C$로 유지한 경우 Rl34a의 필요공기유속은 R22보다 5.9%작게 나타났으며, R134a의 압력강하는 R22보다 $18.1{\sim}20.4%$의 범위 내에서 크게 나타났다.
R134a is considered as an alternative refrigerant to R22 for air conditioners. An experimental investigation was made to study the characteristics of the heat transfer and pressure drop for R134a flowing in a fin-and-tube heat exchanger used for commercial air-conditioning units. Experiments were carried out under the conditions of inlet refrigerant temperature of $60^{\circ}C$ and refrigerant mass fluxes of $150,\;200,\;and\;250\;kg/m^{2}s$. The inlet air has dry bulb temperature or $35^{\circ}C$, relative humidity of 40% and air velocity varying from 0.68 to 1.6 m/s. Experiments show that air velocity decreased by 5.9% is needed for R134a than that of R22 while pressure drop for R134a was $18.1{\sim}20.4%$ higher than that of R22 for the degree of subcooling $5^{\circ}C$. The results are useful in designing more compact and effective condensers for various refrigeration and air conditioning systems using refrigerant R134a.