The dynamic behaviour of a solar operated absorption cooling machine

Abstract

The present energy crisis due to the depletion of fossil fuels and rapid energy consumption has created renewed interest in absorption cycles based on solar systems used for refrigeration, air conditioning, and space heating, their principal advantage being the small amount of mechanical work required. While a heat input many times greater than the work input of a vapour-compression cycle is required, the absorption cycle can be economically attractive if the heat is sufficiently cheap. Comparing the performance of the vapour-compression cycle to the absorption cycle, the performance of the latter is less than that of the former. This, owning to the fact that work input in the latter has been obtained at the expense of the irreversibilities and the degradation of energy inherent in the conversion of heat to work. However, the lower performance of the absorption cycle system can be compensated for by the fact that the absorption cycle can be driven by low grade heat available from solar collectors. Objectives: The performance of a solar operated absorption machine used for space cooling is the main objective of this thesis. Thus the coefficients of performance (COP) for the machine were computed from data collected during tests carried out in the peak months of summer. Finally an overall economic feasibility, together with recommendations for system performance improvement, is presented. The absorption machine, located in Bungalow 2, operated in order to cool the space air inside the bungalow via four fan coil units (refer to Figure 1.1). The solar energy was supplied to the machine from a bank of concentrating collectors (refer to Figure 1.2). Al equipment used is situated at the Austrian Maltese Research Centre (AMRC), Marsaxlokk, Malta. Due to the fact that the whole maintenance operation, described in Section 3. took much more time than expected, the time remaining for testing was very limited. It must also be mentioned that after a short period of successful operation, the absorption machine failed due to a leak in the evaporator. What’s more, repair work was out of the question, as from past experience, the job would be very lengthy. This would therefore leave absolutely no time for additional testing and analysis of results. Thus, not all the planned experiments could be performed. It was therefore decided that for this thesis to be a more complete form of study on the subject, additional data was retrieved from print-outs kept at the AMRC. This data, as yet never analysed, was recorded when the absorption machine was in full operation under the auspices of the Austrian Research Team in 1984.