Experimental studies on a direct-steam-generation absorption heat transformer built with vertical falling-film heat exchangers

This study presents an experimental rig of direct-steam-generation single-stage heat transformer (SSHT), which was built with four main vertical heat exchangers and a plate heat exchanger. This rig uses a LiBr-water binary working fluid and is driven by low-grade hot water. Data from six test runs were analysed. The results show that bilateral falling film made it easier for the absorber to generate steam directly with pressure changing from 190 kPa to 260 kPa, which corresponded to an absorber heat load from 15.5 kW to 7.2 kW, coefficient of performance (COP) from 0.38 to 0.20, and exergy coefficient of performance (ECOP) from 0.48 to 0.27, respectively. The absorber temperature can be as high as 124 °C, with calculated internal gross temperature lift (GTL) of 34.8 K and external GTL of 29.6 K. The economizer was a conventional plate heat exchanger with effectiveness around 0.73 in six test runs.