Introduction
In collective housing (apartment buildings, dormitories, service flats, etc...) projects the heat distribution for space heating (SH) and domestic hot water (DHW) can be implemented using satellite units. The satellite unit system exists of a central boiler room with a boiler and pump, heat distribution happens via a shared circulation pipe. The central heating and domestic hot water needs of each individual apartment is managed by a satellite unit.
...
Hysopt incorporates an extension of the DIN 1988-300 (2012) standard into the Hysopt software. We have extended the calculation to cope with simultaneous space heating and domestic hot water usage, and with combination of power needed in mixed systems.
In the example below, there is a shower- and a kitchen tap. When the flow rates are summed the total flow rate is 0.22 l/s, When using the simultaneous factor this becomes 0,17 l/s. For one satellite unit the difference between total and simultaneous flow rate is quite small, in case of a building with several units the simultaneous flow rate can go to 10% of the total flow rate which have a big impact on the pipe selection.
On the basis of the DHW design flow rate at the level of the heat exchanger and the performance of the heat exchanger (UA-value - W/K, from the technical specifications of the manufacturer), the primary to supply DHW flow rate is calculated which is necessary for the transfer of the required thermal power. In this example, the primary flow rate 0.86 m³/h , and the secondary flow rate 0.6 m³/h. The primary and secondary flow rate of space heating rate remains unchanged. The example below shows that there is a big difference between thermal power and flow rate according to SH and DHW, also the UA- value of the heat exchanger has a influence on the primary and secondaryreturn temperature and flow rate of DHW.
