Abstrakt

Nowadays, the most difficult technological challenge in energy sector is connected with the gas micro-CHP units, dedicated to the distributed power generation. They are expected to be of high efficiency and at the same time of compact in size. Regarding the first reason, significant increase in microturbine efficiency can only be achieved by increase in the engine operating temperature. Therefore, one of the critical elements in such installation is the recuperator, which contributes to the overall microturbine efficiency in considerable part. Taking into account the system size and its efficiency, only the compact heat exchangers with passive techniques of the heat transfer intensification can fulfil strict requirements. Very promising are the cylindrical/plate heat exchangers with minichannels or heat exchangers with jets/microjets technology. In the paper an own construction of plate heat exchanger with minichannels, proposed for high-efficiency gas microturbine engines with external combustion chamber is considered. It consists of a set of steel plates with the channels of rectangular crossection, with 3 mm width and 1.5 mm depth. This unit can be supplied with air at temperature about 1000 C and transfer the thermal energy to air at temperature close to the ambient level. A numerical model was developed for the entire unit and validated with the experimental results, coming from the analysis conducted on the prototype in the “cold” conditions (at 18 C) and normal operating conditions (at 957 C). The experimental and numerical results, referring to the pressure drop, agreed within 2%-14% range, while referring to the heat rate – within 1%-7% range. Analysis of local thermal and hydraulic results was a source of few ideas, concerning an optimization of the heat exchanger construction, oriented at the improvement of its performance.

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