This paper presents the off-design modelling of a domestic scale solar organic Rankine cycle (ORC) and vapour compression cycle (VCC) in a coupled operation in different operating modes by using evacuated flat plate (EFP) collectors. Thermodynamic and parametric studies of such coupled system in literature usually assume that the isentropic efficiencies of expander and compressor and the heat exchanger pinch temperature differences are constant. Moreover, studies for directly coupling the ORC-VCC system with solar collectors are somewhat rare. Transient performance of the solar ORC-VCC considering the off-design behaviour of the system components needs to be investigated. A simulation for a period of 24hrs is conducted by considering the electricity and cooling demand of a 60 m 2 office building during a typical day in July for Istanbul. The effect of heat storage capacity on meeting the demand is investigated for a given area of EFP collectors. Moreover, the water flow rate to the boiler is controlled periodically to provide the demanded electricity and cooling. The required EFP collector area and heat storage unit volume have been determined to be 80 m 2 and 9.4 m 3 , respectively. For these design parameters, 25.6 kWh cooling and 18.76 kWh electricity can be generated during a typical day in July. Finally, a simulation is given for such design on a sunny winter day in February, 5.5 kWh electricity and 104 kWh heat can be produced.

Fluid flow and heat transfer in communicating converging and diverging channel has been numerically investigated. Channels are assumed to be at constant wall temperature and the flow is assumed to be steady state and incompressible. Since the flow and temperature fields to repeat periodically after a certain developing length, periodic boundary conditions are used for the calculations. Finite volume method is used to solve the governing differential equations numerically. Computations are performed for different values of the plate angles and Reynolds numbers. Moreover, velocity distributions along the flow field are illustrated. It was found that the converging-diverging channels destroy the boundary layer significantly and Nusselt number is found to be about 400% higher than those of parallel plate channels, whereas due to vortex formation, pressure drop increases also.

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