Royyan Firdaus

Universitas 17 Agustus 1945 Surabaya

M.Fatur Farhat

Universitas 17 Agustus 1945 Surabaya

Yahya Nurwahyudi

Universitas 17 Agustus 1945 Surabaya

DOI: https://doi.org/10.19184/rotor.v19i1.60017 

ABSTRACT 

Expansion device characteristics directly affect how an automotive AC system performs in the refrigeration cycle. Among common expansion devices, capillary tubes are preferred due to their simple construction, low cost, and ability to regulate refrigerant flow. This study experimentally examined how varying the capillary tube diameter impacts the operating behavior and COP of an R-134a automotive air conditioning system. Three capillary tube diameters were tested: 0.64 mm, 0.70 mm, and 0.80 mm. A Thermostatic Expansion Valve was also tested as a benchmark. Pressure and temperature data were measured at multiple points in the cycle and used with CoolPack software plus the R-134a p–h diagram to calculate refrigerant enthalpy. System performance was then assessed through mass flow rate, compressor work, evaporator cooling capacity, condenser heat rejection, HRR, and COP. Results show that tube diameter has a major influence on refrigerant flow and overall AC performance. Diameter changes led to differences in cooling capacity, compressor power use, heat rejection, and COP. The comparison with TXV also highlights how effective capillary tubes are as expansion devices in R-134a automotive AC systems.

Keywords: automotive air conditioning, capillary tube diameter, coefficient of performance, r-134a, thermostatic expansion valve.

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