EXPERIMENTAL INVESTIGATION OF BUBBLE PUMP AND SYSTEM PERFORMANCE FOR A SOLAR DRIVEN 2.5 KW DIFFUSION ABSORPTION COOLING MACHINE

This paper presents the development and experimental investigation of the indirectly heated, solar powered generator with its bubble pump and the 2.5 kW Diffusion Absorption Cooling Machine (DACM) performance. The DACM, which has a combined evaporator-gas heat exchanger-absorber unit, is designed for the application area of air-conditioning as a water chiller as well as for the operation of activated ceilings with an evaporator temperature of 12/6°C or 18/15°C, respectively. The set up of the machine with two different bubble pumps was in October 2005. With a total height of 2.20 m and a weight of 240 kg marketable dimensions were reached. The measurements were carried out at stationary pressure and temperature levels. Heating temperatures of the generator in a range between 100°C and 150°C were obtained. The values of coefficient of performance (COP) were between 0.12 and 0.38, while the continuous evaporator cooling performance was between 0.7 kW and 3.0 kW, depending on cold cycle temperatures (-8 to +18°C). In October 2006, the two bubble pumps were replaced by a single one, which now combines the heat transfer surfaces of the two previous bubble pumps. The latest performance of the machine showed cooling capacities of 2.0 kW and 2.4 kW at evaporator inlet/outlet temperatures of 12/6°C and 18/15°C, respectively. The average COPs are 0.3 at heating inlet temperatures of 125°C. The performance of the investigated bubble pumps shows that they work in a wide operation range at varied heating temperatures as well as external mass flows.