heat transfer, efficiency, two-phase, injector, isobutane
Renewable energy sources may be applied to drive refrigeration and air-conditioning systems, e.g. solar radiation, geothermal resources, heat derived from biomass or waste heat rejected form various thermal processes. In this case absorption refrigeration systems and ejection systems may be used for cooling applications. In both these systems the crucial problem is the development of a suitable liquid pump. Energy consumption to drive these systems is not a major problem here as in most cases amount of energy required to drive a mechanical pump is a contribution of at most a few percent of the overall energy balance of the system and in most cases is of the order of magnitude 1%. Therefore the most important problem is a special difficulty to select of a commercially available liquid pump for the thermal driven cycle (absorption or ejection one). Such pumps should be low cost, small size and should produce sufficiently high compression rate for the discussed applications. They should also be adapted to work in particularly hard operating conditions resulting from the application in the discussed systems low boiling fluids: these are high penetrating substances, most of them are chemically aggressive and high susceptible to erosion caused by cavitation destruction. Under present conditions most of the pumps that could be applied have inadequate overall dimensions as well as are very expensive so the contribution of the cost of the relevant pump is dominant in the total cost of the system. As an effect refrigeration systems driven by renewable thermal sources are commercially unprofitable and unattractive. Paper deals with experimental investigation of two-phase vapour-liquid injector as a liquid pump in refrigeration systems. The selected experiment results for the injector are presented for the case of isobutane as working fluid. Investigations covers the operation characteristics of the injector as well as heat transfer coefficient, as well as evaluation of the efficiencies of the elements of the injector. It was demonstrated that these efficiencies depend on operating parameters and may not be treated as contact quantities.