4.31. Tap point / distribution area

4.31.1. TAP (class)

Fig. 4.31.1 Tap point or distribution area

Supplier type

type label	description	active
Tap return flow	If system head drops below downstream head, tap supplies back to system.	No
Tap non-return flow	If system head drops below downstream head, tap does not supply back to system.	No
Tap non-return flow with dP for reopen	If system pressure drops below downstream pressure, tap does not supply back to system. Supply to system (re)starts when a minimum required pressure is exceeded.	No

4.31.1.1. Mathematical model

In steady state the governing equation of this component is very simple:

(4.31.1)\[Q=-Q_{\mathrm{D}}\]

in which:

Q	= system discharge to the TAP	[m3/s]
QD	= delivery rate	[m3/s]

The negative sign appears because of the convention that a flow out of the system is defined negative. After obtaining the steady state solution the head loss coefficient is computed with:

(4.31.2)\[C=\left(H-H_{\mathrm{D}}\right) / Q^{2}\]

in which:

C	=	head loss coefficient	[s2/m5]
H	=	system pressure head	[m]
HD	=	downstream pressure head	[m]

The downstream head is either given by the user or for the Tap non-return flow 2 based on the downstream pressure specified by the user.

This head loss coefficient is kept constant throughout the unsteady state computation.

The governing equation then is:

(4.31.3)\[H-H_{D}=C Q|Q|\]

For the return type of the tap component equation (3) is valid for positive as well as negative values of Q. For the non-return type equation (3) is only valid for positive values of Q. In case Q becomes negative the component changes from H-phase and closes like a check valve. The governing equation the simply is:

(4.31.4)\[Q=0\]

The non-return tap opens again if H > H_D. For the Tap non-return flow 2 an additional pressure drop can be set which is required to open the tap.

4.31.2. Tap return flow

4.31.2.1. Hydraulic specifications

Description	Input	unit	range	default	remarks
downstream head	Real	[Pa]
initial delivery rate	Real	[m­3/s]	(0-5]

See also “Mathematical model” (Section 4.31.1.1).

4.31.2.2. Component specific output

None

4.31.2.3. H-actions

None

4.31.2.4. Component messages

Message	Type	Explanation
System pressure head (… m) is lower than delivery head (… m)	Error	Initially the tap discharge must be out of the system. Since the computed head loss coefficient may not be nega­tive the system pressure head must be higher than the delivery (downstream) head.

See also “Mathematical model” (Section 4.31.1.1).

4.31.3. Tap non-return flow

4.31.3.1. Hydraulic specifications

description	input	unit	range	default	remarks
downstream head	Real	[m]
initial delivery rate	Real	[m­3/s]	(0-5]

See also “Mathematical model” (Section 4.31.1.1).

4.31.3.2. Component specific output

None

4.31.3.3. H-actions

None

4.31.3.4. Component messages

Message	Type	Explanation
System pressure head (… m) is lower than delivery head (… m)	Error	Initially the tap discharge must be out of the system. Since the computed head loss coefficient may not be nega­tive the system pressure head must be higher than the delivery (downstream) head.
opens	Info
closes	Info

4.31.4. Tap non-return flow with DP reopen

4.31.4.1. Hydraulic specifications

description	input	unit	range	default	remarks
downstream pressure	Real	[Pa]
initial delivery rate	Real	[m­3/s]	(0-5]
Delta P for reopen	Real	[Pa]

See also “Mathematical model” (Section 4.31.1.1).

4.31.4.2. Component specific output

None

4.31.4.3. H-actions

None

4.31.4.4. Component messages

Message	Type	Explanation
System pressure (… barg) is lower than delivery pressure (…barg)	Error	Initially the tap discharge must be out of the system. Since the computed pressure loss coefficient may not be nega­tive the system pressure must be higher than the delivery (downstream) pressure.
opens	Info
closes	Info