EXPERIMENTAL STUDY TO DETERMINE THE LOCAL CONDENSATION HEAT TRANSFER COEFFICIENTE FOR R134A FLOWING THROUGH A 4.8 MM INTERNAL DIAMETER SMOOTH HORIZONTAL TUBE

Abstract

Refrigerant fluid R134a is commonly one of the most utilised in
vapour compression cycles wordlide, wheter in dommestic HVAC or
automotive regrigeration systems. This paper’s goal is to
experimetnally determine the fluid local condensation Heat Transfer
Coefficient (HTC), in several flor regimes. In this work, the mass flux
was equal to 200, 250 and 300 kg/(m2s) and the fluid flowed
through a smooth, horizontal 4.8 mm internal diameter aluminium
pipe, during which its vapour quality varied along the entire quality
range. A purpose built test rig was developed, in which fluid
conditions were constantly monitored and controlled. Through
measurements in temperature and pressure, an energy balance was
used to calculate experimentally the local heat transfer coeeficient.
Average results for the unit quality range equalled to 3781 , 3459 and
3944 W/m2K for saturation temperature equal to 30 C and the
aforementioned mass velocities. Likewise, at 35C the averages HTC
found were 2903, 3141 and 3898 W/m2K at the same mass flux
rates. Later on, the experimental results were compared to ten
commonly used HTC correlation found in relevant references,
with Chato’s correlation returning the best fitting.