2 replies to this topic

[rsk]

for a closed loop system catering to several heat loads in parallel, what shall be the approach in sizing the pump.
Sir please correct me if i am wrong
1. Flow: the desired flows through each path to cater the heat load are fixed, total of this will give pump design flow & taking some margin will give pump design capacity.
2. For each path pressure drop is calculated at the desired flows, & pump developed head is selected to cater to this max pressure drop. flow will naturally be more through other parallel paths (relatively lesser resistance) which will be set by manual valves.
Thanks in advance

[JoeWong]

for a closed loop system catering to several heat loads in parallel, what shall be the approach in sizing the pump.
Sir please correct me if i am wrong
1. Flow: the desired flows through each path to cater the heat load are fixed, total of this will give pump design flow & taking some margin will give pump design capacity.
2. For each path pressure drop is calculated at the desired flows, & pump developed head is selected to cater to this max pressure drop. flow will naturally be more through other parallel paths (relatively lesser resistance) which will be set by manual valves.
Thanks in advance

A close loop system with pump feeding 3 users in parallel and the flow are Q1, Q2 and Q3. The pressure drop on each user are DP1, DP2 & DP3 respectively. DP1 is maximum among all.

1) Pump capacity should be (Q1 + Q2 + Q3 + margin). In real world application, there will be a bypass across the parallel users to manage the pressure fluctuation. The flow could be 10% (Q1+Q2+Q3). Thus the pump capacity is (110% (Q1+Q2+Q3) + margin).

2) Pump head shall be sufficient for :
= pressure drop from pump discharge to the user with maximum pressure drop (DP1)
+ pressure drop of the user (DP1)
+ minimum pressure drop of the controlling device (i.e. control valve) if any
+ pressure drop on the return line (upto pump suction)

You are right that the pressure drop on the parallel loop are same. The balance pressure drop shall be taken by the manual valve (or control device).

For user 1, pressure drop on manual valve = DP1 - DP2
For user 2, pressure drop on manual valve = DP1 - DP3

[fallah]

for a closed loop system catering to several heat loads in parallel, what shall be the approach in sizing the pump.
Sir please correct me if i am wrong
1. Flow: the desired flows through each path to cater the heat load are fixed, total of this will give pump design flow & taking some margin will give pump design capacity.
2. For each path pressure drop is calculated at the desired flows, & pump developed head is selected to cater to this max pressure drop. flow will naturally be more through other parallel paths (relatively lesser resistance) which will be set by manual valves.
Thanks in advance

A close loop system with pump feeding 3 users in parallel and the flow are Q1, Q2 and Q3. The pressure drop on each user are DP1, DP2 & DP3 respectively. DP1 is maximum among all.

1) Pump capacity should be (Q1 + Q2 + Q3 + margin). In real world application, there will be a bypass across the parallel users to manage the pressure fluctuation. The flow could be 10% (Q1+Q2+Q3). Thus the pump capacity is (110% (Q1+Q2+Q3) + margin).

2) Pump head shall be sufficient for :
= pressure drop from pump discharge to the user with maximum pressure drop (DP1)
+ pressure drop of the user (DP1)
+ minimum pressure drop of the controlling device (i.e. control valve) if any
+ pressure drop on the return line (upto pump suction)

You are right that the pressure drop on the parallel loop are same. The balance pressure drop shall be taken by the manual valve (or control device).

For user 1, pressure drop on manual valve = DP1 - DP2
For user 2, pressure drop on manual valve = DP1 - DP3

Dear Joe

Regarding above two equations aren't their correct forms as below?:
For user 2, pressure drop on manual valve = DP1 - DP2
For user 3, pressure drop on manual valve = DP1 - DP3

Regards