Performance evaluation of an absorption heat transformer for industrial heat waste recovery using the characteristic equation

In this paper we report on new experimental results of an absorption heat transformer. In order to have a concise view on the whole performance field the characteristic equation model, a novel version of ideas from the 80ies of the last century is developed. In the model insight from recent research on absorption chillers is used. The 40 kW prototype implements a single effect absorption cycle working with water as refrigerant and an aqueous LiBr solution as the solvent. As a novelty, the parameter set of the characteristic equation model has been obtained from the cycle analysis of the device based on the measurements of one single operating point. The resulting model predicts the prototype performance for driving heat temperature levels of low temperature industrial waste heat sources (60–100 °C), with variations of the temperature of the useful upgraded between 90 and 138 °C that result in gross temperature lifts (GTL) between 20 and 55 K. The measured COP values are between 0.30 and 0.48. An additional regression developed after evaluating the deviations from the model assumptions reduces the uncertainty of the model. The uncertainties for COP and upgraded heat flow rate predictions are below 11% (R² = 0.812) and 4% (R² = 0.918) respectively.