In order to optimize the operation of the hot water and steam central heating systems in Tianjin Economic-Technological Development Area, China, the energy and exergy efficiencies and exergy losses of overall system have been analyzed by integrating the first and the second law of thermodynamics. The results indicate that the energy efficiencies of the hot water heating system and steam heating system are 57.10% and 89.98%, while the exergy efficiencies are only 13.89% and 41.02%. The heat losses of energy stations account for 56.98% and 89.75% and the exergy losses of energy stations account for 94.84% and 98.64% for the hot water central heating system and steam central heating system, showing that the energy station is the major part of energy and exergy destruction in the heating system. In order to improve the energy and exergy efficiencies, more attentions should be paid to improving the combustion efficiency of the boiler, and some measures should be taken to reduce energy and exergy losses, such as reducing the exhaust gas temperature, recycling condensed water and improving the hot water or steam temperatures. Besides, good thermal insulation materials should be used to reduce the heat losses of heating pipe networks.
Keywords Central heating system, energy and exergy analyses, system optimization