Development of a direct concept helical-coil evaporator for an ORC based micro-CHP system

The combined production of heat and power (CHP) has been considered the major alternative to traditional systems in terms of energy savings and environmental conservation. Micro-CHP systems are those suitable for a scale that ranges from the thermal demands of public/commercial buildings down to the needs of individual household. The residential market represents the most promising sector for the micro-CHP systems which has the potential to meet a number of energy, social and policy goals. Considering the available technologies, ORC based CHP solutions are recognized as one of the simplest and less likely to raise difficulties to retrofit the current residential heating systems. ORC based CHP systems points to a residential implementation almost with market available components. In fact, two of the most important components, the pump and the condenser, are considered off-the-shelf products while the expander has been adapted from a scroll compressor with success. On the other hand, for the ORC-evaporator there isn’t a ready-to-use component within this power range and the overwhelming majority of the ORC based systems developed by universities or research centers use an indirect way to vaporize the organic fluid which involves the implementation of an intermediate circuit, usually with water or oil, between the heat source and the ORC-evaporator. This intermediate circuit appears to be far from the ideal solution because it increases the thermal inertia, the system complexity and costs. This paper presents the conceptual design and the preliminary characterization results of a special developed heat-exchanger to be incorporated in an ORC cycle and work as an evaporator.