Experimental characterization of a newly developed air-source water-ammonia gas absorption heat pump for residential applications

摘要

The need of providing Domestic Hot Water (DHW) and the use of radiators in most existing buildings in the European market represent the main barriers to the diffusion of heat pumps. Moreover, to use a heat pump as monovalent appliance, it has to be properly sized to meet the maximum heating load of the building; this causes the appliance to work at part load conditions for a large part of the heating season, making the part load efficiency and the control strategy crucial for the seasonal plant performance. To overcome these barriers, within the European project HEAT4U an 18 kW heating capacity air-source water-ammonia Gas Absorption Heat Pump (GAHP) has been developed. The appliance is designed to maintain high efficiency with an outlet temperature up to 65°C and at part load conditions. Standards, as the new prEN 12309, provide a method for calculating the seasonal efficiency of gas driven appliance. Such methods provides a term of comparison among different appliances, but can hardly be used to quantify the energy savings or the seasonal performance of GAHP in real life applications. Calculation of appliance behavior under various conditions, such as different climate conditions, building size, system layout or control strategy are usually carried out by means of software for dynamic simulation of building and system. Purpose of this paper is the development of a simple and flexible model of the 18 kW GAHP which could be used for this purpose. The model is based on experimental data, collected in compliance with the test protocol defined in the latest version of European Standard prEN 12309, collected under a wide range of test conditions, with different outlet water temperature, air temperature and delivered heating load. The developed model, based on the characteristic equation, is suitable for the implementation in existing simulation software. The input of the model are the gas input, the outdoor air temperature and the outlet water temperature; on the basis of these data, usually available, it predicts the GAHP hating capacity and GUE with a uncertainty lower than 10%.