Question

An engineer operates a counter-flow shell-and-tube heat exchanger. It is known that the A fluid (specific heat is 1.0 J/g*°C) flows into the outside of the tube at a mass flow rate of 100 g/hr. The inlet temperature is 90 ° C and the outlet temperature is At 70 ° C, the B fluid flows into the tube. The inlet temperature is 20 ° C and the outlet temperature is 65 ° C. If the heat transfer effective area is 20 m ² , answer the following questions:

(1) What is the logrithm average temperature difference (ΔTln) for °C?

(2) What is the total heat transfer coefficient (Uo) J/(hr*m2 *°C)? (ln2=0.693)

Answer 1

Solution Inlet temperatures fluid A → Tai = go' L fluid B → TB: = 20 € outlet temperatures To fluid A w Tao = 70° ng fluid B - TB. - GSC Given specific heat of fluid A CP= i 5/g.oc. Also flow rate of fluid A MA= 100 8ln. & Heat transfer rate G- MA Con CTAE-TAQ) Q. 100% 1x (90-70) Ilona g. 2000) Jine for counter flow s ARPET LE TBi zati. TA :> Tao ý AT: e AT, = AT2 = TAO- TB70-20:505 TAI - Tee = go-65 = 25's

o dogmean temperature difference C LMTD) olem = LMTD = Atar OT-AIR stem = LMTD = (50-25) c = 25 de 0,693 Atem = TEMTD = 36.075 l Ganswer © Now ow given & Area of Heat transfer A = 20 me Heat transfer rate = VASTUM U- Overall Heat transfer coefficient 200. A A Tum 2o x 360 - 1 AP TU = 2.772] marine " Total Heat transfer coefficient.