Problems with low-temperature methanol wash heat exchangers and heat exchangers in general
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1. In the system, I feel that the heat generated by the pump cannot be ignored. So how can we reduce the heat produced by the pump without decreasing the flow rate? 2. What is the temperature difference between the inlet and outlet of the rich-methanol and lean-methanol heat exchangers in low-temperature methanol washing? Flow rate is a key factor in heat transfer; how can it be reduced while maintaining the flow volume? (Is Rich-41/Poor-28 normal?) ）
Reducing the heat generated by the pump can lower the methanol circulation rate. To reduce the flow rate, larger pipes can be used in place of smaller ones.
Heat generation by pumps is inevitable; heat is produced as long as the pump is operating~! How can no heat be generated when the flow rate remains constant~! The best approach is to use a variable-frequency pump–it helps save energy and also reduces heat generation. A ratio of Fu-41 to Poor-28 of this kind is abnormal in normal production; the main reason for this is that the amount of carbon dioxide released is too low. It seems you don’t fully understand how heat exchangers work: in a heat exchanger, the flow velocity in the tube side is slower than that at the inlet side! The main increase is in the heat exchange area~! Why didn’t I consider flow rate nearly at all when designing the heat exchanger? It seems that flow rate isn’t either a very important parameter, right? You should take a close look at the calculations for the heat exchanger
“Reducing the heat generated by the pump can lower the methanol circulation rate. ” How to explain it?
I agree with the view from the third floor – there isn’t any direct relationship between flow rate and heat exchange efficiency, right? Are the Fu-41 and Pei-28 you mentioned referring to that temperature? If it’s a rich-lean fluid heat exchanger, then the heat exchange efficiency is extremely poor@ The temperature difference between the inlet and outlet of our largest rich-lean fluid heat exchanger is over 70 degrees! ~Generally, the temperature of the lean liquid entering the washing tower is around -50 degrees, while that of the rich liquid is as low as around -60 degrees!
Less methanol is pumped, so less work is done on the methanol; consequently, less heat is lost by the methanol as well! [I replied on the 2nd floor; I didn’t see clearly that ‘the data usage remains unchanged’.]
I think this is still worth considering! Two formulas are required for the design calculation of heat exchangers: Q=m*c*Δt ； Q=k*s*Δt. This m represents the mass of the fluid [that is, the load on the heat exchanger]. The higher the flow rate, the greater the mass that passes through per unit time; consequently, a larger heat exchange area is required to reach the same temperature. In other words, with the same heat exchange area and under the same conditions, the higher the flow rate, the smaller the temperature increase of the fluid ； The flow rate is low. . . This post was last edited by z880347730 on 2009-3-12 18:40]
The manager in our unit has set the shut-off valve at the pump’s inlet to a relatively low position; I’m not sure why