I'm having some difficulty to model a gas engines in energyplus. The project was designed to have an absorption chiller feeded by hot water, this hot water is produced in this gas engine that is feeded by natural gas (cogeneration), but at the same time I have a heat exchanger (air to water) between the exhaust air, from the gas engine, and the hot water produced. I'm sending an pdf explaining it better. How can i model the gas engine?