Thermal analysis of indirect geothermal district heating systems

Low- and moderate-temperature geothermal resources have been discovered in many areas of the world, and are being used increasingly for district heating. Due to the corrosive action of some geothermal waters, heat exchangers are used to avoid circulating the geothermal fluid directly through the district heating systems, in what are called Indirect Geothermal District Heating Systems (IGDHS). In this case, the geothermal water acts as a heat source directly heating the network fluid through a heat exchanger. However, it is different from that of conventional systems in which hot water from a fossil fuel boiler is used directly. In the former (IGDHS), the geothermal water is regarded as a heat source with constant temperature, and in the latter the boiler is considered a heat source with variable heat flux. This paper presents a thermal analysis of a simple IGDHS, and discusses the selection of heat exchangers and optimum operating conditions. (~) 1997 CNR. Published by Elsevier Science Ltd.