The presence of oil in an evaporator degrades performance by reducing evaporator heat pick‐up and by increasing the evaporator pressure drops. It can be demonstrated that there is an optimum refrigerant mass flow rate for a given refrigerant‐oil combination and oil concentration. Also, oil viscosity has an effect on the evaporator performance at low oil concentrations. Finally, it is suggested that low viscosity oil be used at low oil concentrations and high viscosity oil at high oil concentrations.

This paper presents experimental study of diesel engine heat pump (DEHP) system to find potential as retrofit technology in off-gas or weak electricity network area to replace existing gas/oil/electric heating system in domestic sector. Test setup of diesel engine driven waterto-water heat pump system was built which included heat recovery arrangement from the engine coolant & exhaust gas. The system was designed to meet typical house heating demand in Northern Ireland. Performance of DEHP was evaluated to meet house-heating demand at different flow temperature (35, 45, 55 & 65°C), a typical requirement of underfloor space heating, medium/high temperature radiators and domestic hot water. The performance was evaluated against four-evaporator water inlet temperature (0, 5, 10 & 15°C) and at three different engine speed 1600, 2000 & 2400 rpm. Experiment results were analysed in terms of heating/cooling capacity, heat recovery, total heat output, primary energy ratio (PER), isentropic efficiency etc. Test results showed that DEHP is able to meet house-heating demand with help of heat recovery with reduced system size. Heat recovery contributed in a range of 22 to 39% in total heat output. It is possible to achieve high flow temperature in a range of 74°C with help of heat recovery. Overall system PER varied in a range of 0.93 to 1.33. Speed increment and flow temperature has significant impact on heat recovery, total heat output and PER. A case scenario with different flow temperature to match house-heating demand has been presented to show working potential with different heat distribution system. In addition, DEHP shows good potential to save primary energy consumption and CO 2 emissions, a helpful technology to achieve national emission reduction target.

SUMMARYThis paper highlights the effects of circulating compressor lubricants on the performance of vapour compression refrigeration systems. It will give a baseline case of R12 and a mineral oil and show to what degree the alternative refrigerants and their mixtures conform to this.

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This paper compares the performance of a thermostatic expansion valve, thermoelectric expanison valve, solenoid expansion valve and a motorized type operating as part of an extensively controlled and instrumented refrigeration system. It will be shown that the solenoid expansion valve provides the best contol.