An approximate expression for part-load performance of a microturbine combined heat and power system heat recovery unit

An approximate expression for the heat transfer rate of a heat recovery unit (HRU) fed by the exhaust gas exiting a microturbine operating at part-load is developed. The proposed expression can be used for various microturbine-HRU sets if the appropriate values of coefficients are used. The independent variables in this expression are limited to: the microturbine electrical power output, the circulating water mass flow rate, and the circulating water inlet temperature. By the method of non-linear regression the coefficients of the approximate expression are determined for two types of microturbines and five types of HRUs. The developed expression greatly facilitates the prediction of available thermal power. Thus it can be useful in mathematical modeling of cogeneration plants based on microturbines as well as at the design and operation of such systems.

► Heat transfer rate in a heat recovery unit for 10 cases of microturbine based CHP units is calculated.
► Correlation for the heat transfer rate versus the electric power, water flow rate and water inlet temperature is derived.
► Coefficients of the correlation are determined for 10 selected sets of microturbine and heat recovery unit.
► Sample analysis is performed using the developed correlation.