Building Services Engineering 5th Edition Handbook

Heating 115
4.34 The titanium flat-plate heat exchanger transfers heat from the brine to the district water circulating
through the Southampton geothermal heating system (reproduced by courtesy of Southampton
Geothermal Heating Company).
together with a much larger 5.7 MW CHP unit. This larger unit is a Wartsila 18V32DF, an
18-cylinder high-efficiency dual fuel reciprocating engine capable of operating on natural gas
or light fuel oil, 35 s Redwood viscosity, as used in water heating plant. Three additional water
heaters rated at a total of 7 MW burn natural gas or oil as needed. The host station also contains
district water treatment and pressurization to 4 bar, district heating pumps, generator control
and switchgear panels, a computerized heat monitoring and charging system and an absorption
heat pump.
Heat recovered from the exhaust gas heat exchanger fitted to the larger CHP unit is matched
to that required by the absorption heat pump; these can work with the geothermal well or the
large-scale district cooling system. The boilers also supply high-temperature hot-water for the
absorption heat pump. The heat pump lowers the return water temperature from the district
circuit so that more heat can be extracted from the flat-plate heat exchanger and the brine. The
heat that is removed from the district circuit is put back into it after the water has passed through
the flat-plate heat exchanger. This takes place at the higher-temperature part of the heat pump,
in the condenser.
A two-pipe recirculatory heating pipe system distributes heat to the Civic Centre, Southampton
Institute, television studios, shops, offices and hotels. Consumers pay charges from heat meters
in their building. Each heat meter integrates the water flow rate passing through that consumer’s
building, the water specific heat capacity, along with flow and return temperatures, to evaluate