Development of Ammonia-Water Absorption Heat Pump Water Heater for Residential and Commercial Applications

Abstract

Approximately half of the water heaters sold in the U.S. and Canada for residential and small commercial applications are natural gas fired storage water heaters, with a maximum theoretical thermal efficiency of 96%. A packaged water heater heated by a 2.9 kW absorption heat pump was designed and demonstrated in this study to achieve performance exceeding these limitations. The modeling and validation of the absorption cycle and of the natural gas-fired combustion system are discussed here. Heat transfer characteristics of the absorption components at expected operating conditions were used to model cycle performance. A single-effect system based on these models was fabricated and yielded a cyclic COP of 1.63, within 3% of predictions. A corresponding GAX cycle-based system yielded performance 20% lower than predicted values, indicating the need for larger heat and mass exchangers to achieve the expected system level performance. The gas-fired burner configuration required for this heat pump is governed by the water heater envelope, desorber geometry and process requirements, coupled with emissions requirements. Parametric CFD analyses were conducted to estimate the impact of chamber design on burner performance, and revealed a beneficial recirculation pattern within the combustion chamber that was strongly influenced by chamber height. Emission reductions depended on chamber diameter, and prototype burners with smaller outer diameter fabricated based on these designs met emission targets.

Energetic evaluation of a double-effect LiBr-H2O absorption heat pump coupled to a multi-effect distillation plant at nominal and off-design conditions

“…Case study 1: Influence of the live steam flow rate on , and distillate production As it can be observed, the slightly increased with the rise of the and ℎ between 7 L/s and 12 L/s (with a percentage of 4.93%), which match with the work stated in Refs [28,38]. The significant increase in with ℎ and can be because the increase of these two parameters helps to raise the heat transfer coefficients of the absorber and condenser falling films in the case of DEAHP and of the first effect falling film in the case of the MED plant, increasing the (10.90%).…”

Simulation of an ammonia-water heat pump water heater with combustion products-driven evaporator

“…Regarding absorption, a unit is studied theoretically and also experimentally in three configurations: a single effect (SE) , solution-cooled absorber (SCA), and a GAX configuration [10]. Predicted performance for the SE, SCA, is a remarkable COP of 1.6, verified experimentally [10]. The GAX configuration does not reach the expected performance, with only a small improvement over the SE, SCA cycle.…”

“…In this regard, compactness is of paramount importance, and adsorption of ammonia in carbon is being considered as a strategy to reduce complexity and to improve COP, currently about 1 [9]. Regarding absorption, a unit is studied theoretically and also experimentally in three configurations: a single effect (SE) , solution-cooled absorber (SCA), and a GAX configuration [10]. Predicted performance for the SE, SCA, is a remarkable COP of 1.6, verified experimentally [10].…”