Abstract: There is disclosed a heat engine 10 comprising: a heat exchanger 12 to transfer heat from a heat source 100 to a working fluid; a positive displacement expander 16 configured to receive inlet working fluid from the heat exchanger 12 and discharge expanded working fluid as a multiphase fluid so that there is an overall volumetric expansion ratio between the expanded working fluid and the inlet working fluid which is a function of an inlet dryness of the inlet working fluid; a variable expansion valve 14 disposed between the heat exchanger 12 and the expander 16, the valve being configured to introduce a variable pressure drop in the working fluid to vary the inlet dryness; and a controller 30 configured to maintain the overall volumetric expansion ratio by controlling the valve 14 to compensate for variable heat transfer to or from the working fluid.

Abstract: A pumping apparatus for a heat engine, includes an extraction line arranged to extract a fraction of liquid working fluid from a working circuit of a heat engine; an extraction line pump for pumping the extracted working fluid; an extraction line heat exchanger for vaporising the extracted working fluid; and a pressure-operated pump for pumping the working fluid around the working circuit, wherein the extraction line pump and the extraction line heat exchanger are arranged in series to convert the liquid working fluid to a pressurised motive gas; and wherein the pump is driven by the pressurized motive gas.

Abstract: There is disclosed a heat engine 10 comprising: a heat exchanger 12 to transfer he at from a heat source 100 to a working fluid; a positive displacement expander 16 configured to receive inlet working fluid from the heat exchanger 12 and discharge expanded working fluid as a multiphase fluid so that there is an overall volumetric expansion ratio between the expanded working fluid and the GC inlet working fluid which is a function of an inlet dryness of the inlet working fluid; a variable expansion valve 14 disposed between the heat exchanger 12 and the expander 16, the valve being configured to introduce a variable pressure drop in the working fluid to vary the inlet dryness; and a controller 30 configured to maintain the overall volumetric expansion ratio by controlling the valve 14 to compensate for variable heat transfer to or from the working fluid.

Abstract: A pumping apparatus for a heat engine, includes an extraction line arranged to extract a fraction of liquid working fluid from a working circuit of a heat engine; an extraction line pump for pumping the extracted working fluid; an extraction line heat exchanger for vaporising the extracted working fluid; and a pressure-operated pump for pumping the working fluid around the working circuit, wherein the extraction line pump and the extraction line heat exchanger are arranged in series to convert the liquid working fluid to a pressurised motive gas; and wherein the pump is driven by the pressurized motive gas.