【Haichuan WeChat Group】Parallel heat exchangers: Why does the flow rate decrease when the valve is opened wider?
Thread Content
Question from a WeChat group: Great Hai Chuan, I have a question. There are three ethylene glycol heat exchangers. Start 2 pumps with a flow rate of around 350. A new ethylene glycol heat exchanger has been added recently, activating 3 pumps. The traffic is normally around 510. When adjusting the outlet valve of the heat exchanger, it was found that when the valve was opened by more than 1/4, the total flow rate from all three pumps would drop rapidly to 350. If the valve is closed, the flow rate will increase. Normally, the flow rate should increase when the valve is opened wider. Why does the flow rate decrease when the valve is opened wider?
Open the valve wider – the pressure is insufficient, so the flow rate doesn’t increase!
Originally there were 3 heat exchangers and 2 pumps; now one more pump has been added, so there are 3 pumps in total. Are all the heat exchangers connected in parallel? Is the valve being adjusted a single unit? Still the manager? The outlet leads back to the storage tank. The tank pressure is 50 kPa. Could an oversized outlet cause air resistance or something similar?
Discuss the opinions in the group; consider whether all pumps are at line frequency. If there are both line-frequency and variable-frequency pumps, it will affect the pressure in the main pipeline; also take backflow and pressure difference into account