Calculation problem of heat exchange area
Thread Content
Hello everyone, I work in water treatment. Can anyone help me calculate the heat exchange area? How much heat exchange area is required to heat 70m3/d of 15°C cold water into 35°C water using 80m3/d of 45°C hot water? Thanks! This post was last edited by Warm Home at 2009-3-4 20:54 ]
Question 111 cannot be heated unless the poster is able.
Attention, the poster, the posts you post must be realistic. You obviously made up the data yourself and posted it randomly. . Doesn’t heat up to 35°C at all
There is a problem with the data, the temperature of the hot water is not enough, or the flow rate is not enough.
It can be calculated! The hot water outlet temperature is more than 25 degrees, and the plate replacement area is about 3 square meters.
Heat exchange also depends on the material, right? Is the default 100% heat exchange?
There is indeed a problem. It should be replaced with low-pressure steam heating or 90 degrees + hot water exchange
If the heat exchange efficiency is 100%, a 0.36m2 heat exchanger is required, and the plate replacement is calculated as 24h/d. K=200kj/(℃, S, h) Using cross-flow heat exchange, the outlet temperature is 27.5℃, and the average temperature difference is 11.2℃. This post was last edited by tongle on 2009-3-18 11:46 ]
First do the caloric calculation, how much heat is needed to heat up, how much heat can be released when cooling down, and then ask the question.
It’s not very realistic. Is the poster wrong?
I think it should be possible to heat it, but the area must be very large.
The hot water inlet temperature is 45, the cold water inlet is 15, and the outlet is 35. The heat exchange effect is calculated as 100%. The specific heat of water within the above temperature range is c1=c2=4.2kJ/kg.℃. The hot water outlet temperature is calculated from q1c1(T1-T2)= q2c2(t1-t2).: T2=27.5℃, the flow direction is countercurrent, and parallel flow is obviously impossible. Δtm=(10+12.5)/2=11.25℃ Select spiral heat exchanger, the heat transfer coefficient is 1800kcal/m2.h. ℃, which is 7560kJ/m2.h. ℃. From Q=kAΔtmτ, the heat exchange area is 2.9m2
Counter-flow heat exchange is used, the heat exchange area is about 8m2, and the heat outlet temperature is 27.3 degrees Celsius. 1#carriemy
1# carriemy Using Q=CM△T, we can see that your request cannot be achieved at all. The heat released is not equal to the required heat. No matter how large the heat exchange area is, it will have no effect.