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[mal]

Hello everyone

I need your help guys to understand this concept. If you have a single pass shell and tube heat exchanger (counter current) between two fluids hot & cold what would be the result of the final(exit, outlet) temperature for both fluids if you increase the mass flow rates for both fluids( hot & cold)

those are the results that i got let me know if it does make sense

Outle(exit) Temperature for Hot fluid Increases (As) Mass flow rate for Hot fluid Increases & Uo Overall heat coeffecient increases.

Outle(exit) Temperature for Cold fluid Decreases (As) Mass flow rate for Cold fluid Increases & Uo Overall heat coeffecient increases

if it's right let me know, if not let me know why and what is the general rule or concept of the velocity or mass flow rate of the fluid Vs. Outlet Temperature of both of the fluids

Thanks in a million

You guys are a lifesaver

[djack77494]

mal,
You need to get your mind around the concepts of industrial heat transfer. Ideally, your system can be viewed as the adiabatic exchange of heat from the hot to the cold stream. Say you reach an operating point and you have temperatures Tci, Tco, Thi, and Tho, where subscripts c & h refer to the cold & hot streams, and i & o refer to the inlet & outlet. If you reached complete equilibrium (infinite surface area to exchange heat), then the fluid with the smaller heat content (m*Cp term) would leave the exchanger at the temperature of the fluid with the larger heat content. Knowing this, you can calculate the heat gained or lost by that fluid. The same amount of heat is lost or gained by the other fluid, so now you can calculate both your exit temperatures. Now, fix the amount of heat transfered at the value described above. When you increase the flow of the cold fluid, its outlet temperature will drop, since a less amount of heat per unit of mass is gained. So, in your equation

Q = m * Cp * (T2 - T1)

as m is increased, Q, T1, and Cp are unchanged. T2 must decrease to maintain the equation. These are not difficult concepts if you are comfortable working with thermodynamics. Rather than trying to just predict what will happen, I'd suggest you try working with some numbers to see the results. Good luck.