Development of a 5 kW absorption chiller for solar cooling installations (Englisch)

A strong increase in the number of solar thermal cooling installations and research efforts could be seen over the last years in Europe. Especially the producers of solar thermal collectors and systems were looking for thermal chillers in the small capacity range to provide solutions for one family houses. In a joint R&D-project of the company EAW, the Technical University of Ilmenau and the Institute of Air Handling and Refrigeration (ILK), all Germany, a test prototype of a 5 kW water/lithium bromide absorption chiller for solar cooling applications was developed. The company EAW already produces water/lithium bromide absorption chillers in the capacity range of 15 to 250 kW. The positive experiences with the heat and mass exchangers used in these chillers have been used. Furthermore, some major design modifications were made with the development of the test prototype to achieve reductions of cost and floor space. The high-pressure vessel was placed above the low-pressure vessel instead of side-by-side. The condenser is situated inside the generator and the evaporator inside the absorber. Therefore, the spiral form of the heat and mass exchangers had to be partially changed. With this design, only one solution pump must be used. The refrigerant transport from the condenser to the evaporator was also optimized. Two test prototypes were built and measured. After measuring the first prototype, the chiller was redesigned to reduce internal heat losses. The illustrated results in this contribution are only some of the series of the experiments with the test plant. From the results, it is clearly, that the work temperatures have a great influence on the cold performance of the chiller. The higher is the needed cold-water temperature, the higher are the cold performance and the COP of the absorption chiller. In addition, the lower is the cooling water temperature; the higher are cold performance and the COP of the absorption chiller.