Optimization of a shell-and-tube district heat condenser for a small back pressure combined heat and power plant

Wood-fired combined heat and power (CHP) plants are a proven technology for producing domestic, carbon-neutral heat and power in Nordic countries. Such plants are often of backpressure configuration, the district heat condenser replacing the vacuum condenser of a condensing power plant. The condenser is usually a shell-and-tube heat exchanger with district heating water on the tube side. In this paper, a new approach is presented to optimize the condenser design considering not only the design-point performance, but also variations in the operating conditions. A power plant model is used to determine the plant performance (net power output and boiler fuel consumption) as a function of the main performance parameters of the condenser at each point. Cuckoo search algorithm is used for the optimization. The results show that although electricity price variation has a significant impact on plant net cash flow rate, the effects of electricity price and heat exchanger specific cost on condenser design are low.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016