Step 5 : propagate power, flows and temperature regimes over multiple dwellings and branches

Introduction

During the compute design flows action, we propagate power, design flow and temperature regimes.

When two branches come together, we propagate the individual parts of the flow :

1. domestic hot water (DHW)

2. heating prioritised by DHW (e.g. when HIU’s are applied)

3. heating not prioritised by DHW (e.g. when electric heaters are applied)

On top of these propagated individual parts, we will apply aggragation, as explained in Step 6 : aggregation of the DHW flow/power with the CH flow/power

Below we explain how the DHW part is propagated, but a similar algorithm applies to heating prioritised by DHW and heating not prioritised by DHW.

Propagation of the DHW part

In the example below we propagate two DHW flows

• DHW flow 1, with total power P1, diversity flow v1, and diversity factor f1

• DHW flow 2, with total power P2, diversity flow v2, and diversity factor f2

The question is : how to calculate the diversity factor f3, total power P3 and diversity flow v3 for DHW?

We calculate these in following order :

• P3 = P1 + P2 (first law of thermodynamics)

• f3 is recalculated based on the applicable diversity standard, applied on the TOTAL amount of tapflow or TOTAL amount of dwellings on the secondary side.

• The diversified power is equal to f3 * P3

• the supply temperature t3_supply is defined by the user

• the return temperature t3_return is calculated as the mixed return temperature of flow 1 and flow 2 (v3 * t3return = v1 * t1_return + v2 * t2_return). This means that the return temperature is not a direct result of the diversity, but a result of the components (like heat exchangers) and the mixing rules

• the diviersity volume flow v3 is calculated using the formula

  

  in which P is the diversity power f3 * P3, m is the diversity massflow (which can be converted to the diversity volumeflow), T1 is the return temperature t3_return, T2 is the supply temperature t3_supply