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

• Flow boiling heat transfer and frictional two-phase pressure drop for NH3/LiNO3 and NH3/(LiNO3 + H2O) in a PHE are presented.
• Effects of heat flux, mass flux and vapour quality on the boiling heat transfer and frictional pressure drop are analysed.
• Mass flux has the most influence on the flow boiling heat transfer.
• Those parameters with a pronounced effect on the frictional pressure drop are the vapour quality followed by the mass flux.

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.