Pressure and flow issues in central air conditioning circulation systems
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I am aware of this situation: after the pump starts, the valve closes, the pressure gauge inside the valve shows high pressure, while the pressure gauge behind the valve indicates a pressure of 0 or very low. As the valve is opened, the pressure indicated by the gauge in front of the valve decreases, while the pressure indicated by the gauge behind the valve increases. The two cooling pumps operating in parallel were measured using an ultrasonic flow meter; the flow rate difference between the two pumps was around 30% (the rated parameters of the pumps were different, while the piping was the same). The pressure gauge installed on the valve indicated that the flow rate of the pump with the higher flow rate was 0.01 Mpa lower. The pressure gauge is a standard seismic pressure gauge with a range of 0-1.6 MPa. If only one unit is used, what is the pressure in the main pipeline? Is the pressure higher in the main pipeline for the pump with a higher flow rate, compared to the pump with a lower flow rate? For example, in the case of a refrigeration pump under the same conditions, when the pump operates at its end or connected to the main unit, is the pressure shown on the pressure gauge higher when the flow rate is high? I’m a bit messy in my explanation; please give me some advice. Thank you!
Draw the characteristic curves of the two pumps, and then you’ll know it by comparing them with the device’s characteristic curves
Hello. I’ll phrase it differently. I don’t want to know the head of each pump; I’m just confused about the pressure levels in the pipeline at different flow rates. For example, with different valve openings, the pressure behind the valve increases as the valve opening gets larger; the greater the flow rate, the higher the pressure behind the valve. In a chilled water circulation system or a cooling water circulation system, with all valves open in the same pipeline, assuming flow rates of 300 and 400, what is the pressure at the same point as indicated by the pressure gauge? Is the pressure higher when the flow rate is higher, or is it higher when the flow rate is lower?
For pumps, the flow rate is low while the pressure is high; behind the valve, the flow rate is high and the pipeline resistance is high, resulting in high pressure there as well
Well, I just want to know the relationship between flow rate and pressure downstream of the valve. For example, regarding the pressure from the refrigeration pump to the main unit: if one pump is used, the flow rate is 200, while if two pumps are used, the flow rate is 350. As the flow rate increases, the resistance in the piping increases as well, which results in a higher pressure. On the pressure gauge at the host, the pressure shown at a flow rate of 350 is higher than the pressure shown at a flow rate of 200, right?
As the valve opening increases, the flow rate rises, and the pressure behind the valve increases as well
For pumps connected in parallel, with a valve after each pump, the pressure behind the valves should be the same, right? Isn’t it true that the pressure is the same throughout a pipe that is connected together? Shouldn’t the pressure be higher when the flow rate is greater?