Experimental investigation of in-tube condensation of low GWP refrigerant R450A using a fiber optic distributed temperature sensor

Abstract

Heat transfer coefficients and frictional pressure drop values are experimentally measured during condensation of R134a and its proposed low global warming potential (GWP) replacement, R450A. R450A is a non-flammable zeotropic mixture of R134a and R1234ze (42/58% by mass). Experiments were conducted in a horizontal tube (ID = 4.7 mm) for a range of mass fluxes (100 kg m−2 s−1 to 550 kg m−2 s−1) and saturation conditions (45 ∘C and 55 ∘C). The measured pressure drop values and heat transfer coefficients were compared with established literature correlations. Good agreement indicates that existing correlations can be used for design of condensers with R450A as the working fluid. Additionally, this study evaluates the viability of using distributed fiber optic temperature sensors during refrigerant condensation experiments. The fiber sensor is installed in the annulus of a tube-in-tube heat exchanger and is used to obtain the axial temperature profile of the cooling water. The measurements from the distributed temperature sensors are compared with conventional RTD measurements co-located within the test section. The results (Average Deviation = ±0.26 ∘C, Maximum Deviation = ±1.11 ∘C) suggest that fiber optic measurement techniques can provide temperature data with accuracy and high spatial resolution (equal to 0.65 mm).