| || || Low temperature engineering|
| || || Development and performance testing of a steam jet refrigeration system powered by low temperature heat for applications in Pacific Island countries |
Author: Chandra, Vineet Vishal
Institution: University of the South Pacific.
Subject: Refrigeration and refrigerating machinery -- Oceania -- Design and construction, Refrigeration and refrigerating machinery -- Oceania -- Testing, Low temperature engineering
Call No.: Pac TP 492 .7 .C532 2013
Copyright:10-20% of this thesis may be copied without the authors written permission
Abstract: The purpose of this research is to study the potential of steam jet ejector refrigeration system powered by renewable or waste heat sources as an alternative to electric powered compressor-refrigeration system for cooling. This was carried out by the means experimental and numerical (CFD) analysis. Two types of ejectors were used in this newly designed setup: a conventional ejector and a supersonic ejector (shockfree ejector). The system setup comprised of an open loop configuration with boiler temperatures ranging from 90 ºC to 120 ºC and the evaporator temperature ranging from 5 ºC to 15 ºC. The boiler and the evaporator-cooling load were equipped with variac-controlled 6 kW and 3 kW electric heaters respectively. The primary nozzle was designed and constructed with the criteria to obtain the maximum coefficient of performance (COP) at boiler temperature of 90 ºC and nozzle with a throat diameter of 3.5 mm theoretically satisfied this criteria. Nozzles with 2 mm and 3 mm throat diameter were also constructed for comparison. Two ejectors were designed and constructed for testing. Experimental and numerical (CFD) results revealed that at 90 ºC boiler temperature, the nozzle with a throat diameter of 3.5 mm achieved the highest COP of 0.235 at evaporator temperature of 10 ºC and any further increases in boiler temperature resulted in a decrease in COP with a noted increase in critical condenser pressure. It was also found that decreasing the throat diameter increased the optimal boiler temperature at which the COP was highest and any increase in evaporator temperature resulted in an increase in COP overall. The results additionally illustrated that supersonic ejector has a higher COP and critical condenser pressure than conventional ejector and did not encounter shock, which was experienced by conventional ejector. An optimum nozzle exit position (NXP) was noted to be between -10 mm to 0 mm. From these experiments, it is established that a steam jet refrigeration system performs well with stability at low heat input of below 120 ºC which can be obtained from solar or waste heat and this system performance is enhanced by the use of supersonic ejectors. These characteristics at large should inspire the growth in the innovative utilisation of such systems so that harmful emissions triggered by using electric powered compressor-refrigeration systems can be reduced.