Pressure difference and flow rate issues in the circulating water system
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I would like to ask the experts: in our factory, the pressure of the circulating water at the outlet is 0.35 MPa, while the pressure at the inlet is 0.232 MPa. However, the temperature difference is only 6 degrees – neither the pressure difference nor the temperature difference meets the design specifications (pressure difference of 0.2 MPa, temperature difference of 10 degrees). The temperature of the heat exchanger is currently high; could this be due to scaling on the heat exchanger or a low pressure difference?
Firstly, the smaller the temperature difference, the greater the flow rate. If your design calls for 10 degrees but it’s actually 6 degrees, it indicates that the flow rate is too high. Meanwhile, your inlet pressure is 0.35 and the return pressure is 0.23; your pressure difference is 0.12. Is there any end valve that is closed? It is recommended that you open all the return valves.
The design temperature difference is the temperature difference at the designed flow rate, while the design pressure difference is the pressure difference under conditions of reduced return water pressure and increased return water flow rate; it is inaccurate
Check the circulating water flow rates and temperature differences in each branch; it’s possible that the branch with lower resistance has an excessive flow rate, so adjust the hydraulic balance across all branches.
The heat exchange efficiency is poor, and scaling is a possibility; even scaling of less than 1 mm can reduce the heat exchange efficiency by 30%. Switch to a better scale inhibitor manufacturer, or consider other alternatives
Based on your description, both the temperature difference and pressure difference are below the standard values; therefore, the temperature of the heat exchanger should not be high, which would represent a waste. However, in reality the temperature of your heat exchanger is quite high, indicating that its heat exchange efficiency is poor. This could be due to blockages, insufficient heat exchange capacity, or an excessively open bypass valve. First, check for issues with the heat exchanger; if everything is normal, then reducing the flow rate at the return valve will increase both the pressure difference and the temperature difference
This post was last edited by hesonchang214 on 2019-9-22 at 10:26. There are definitely differences between the design data and actual operation; the following recommendations are given for heat exchangers: 1. Check the flow rate to see if it is caused by insufficient water volume
It is possible that the branch pipes are too narrow, resulting in insufficient flow rate and thus affecting the operation of the heat exchanger. You can check the temperature of the cooling water exiting the heat exchanger; if the temperature difference is large, it is likely a problem with the pipes, while if the difference is small, scaling may be the cause