Boiling heat transfer and pressure drop of NH3/LiNO3 and NH3/(LiNO3 + H2O) in a plate heat exchanger

Abstract

This paper presents the experiments carried out to determine the flow boiling heat transfer coefficient and associated frictional pressure drop in a plate heat exchanger which uses the binary fluid mixture ammonia/lithium nitrate and the ternary fluid mixture ammonia/(lithium nitrate + water) with a water content in the absorbent of 20% by weight. The effects on the flow boiling heat transfer coefficient and two phase frictional pressure drop are analysed with a heat flux range of 5–20 kW m−2, a mass flux of 50–100 kg m−2 s−1 and a mean vapour quality of 0–0.2.The mass flux greatly influenced the flow boiling heat transfer coefficient, whereas the addition of water only produced a slight increase. The measurements taken experimentally indicated that the parameters with a pronounced effect on the frictional pressure drop were vapour quality followed by mass flux. Finally, the correlations proposed in Táboas et al. [1] used to predict the flow boiling heat transfer coefficient and frictional pressure drop were well in agreement with the experimental results.