Question

1. A shell-and-tube heat exchanger with 1 shell and 10 tubes is used to heat glycerine in the shell, with hot water in the tubes. The tubes are thin walled and have a diameter of 1.5 cm and length of 2 m. The water enters the tubes at 100°C at a rate of 5 kg/s and leaves at 55°C. The glycerine enters the shell at 15°C and leaves at 55°C. Determine the mass flow rate of the glycerine and the overall heat transfer coefficient of the heat exchanger. Standard conditions may be assumed for material properties

Answer 1

shell and tube heat exchanger

Specific heat of water and specific heat of glycerin is taken as a standard value

Counter flow is consider as for parallel flow LMTD can not be calculated

Date m2 = Steges Thi: 100°c Tc, = 5°C comoss of water) The = 55°c TC2 = 55°c To find mass flow rate of glycerine cm I overtall Heat transfer coefficient of He soin o Assuming that there is no Heat loss to sunsounting Energy balonce in Heat elecharger is Heat loss by hor quiel - Heat gain by cold fluid. Max Chx (The- Tha) = me x Ce X CTc. - Tei) - where ch=spreific Heat of water = 4.2 killage (ca specific Hear of glycerine = 2.43 12 / Ege substituting known values in eon 5x 4.2 x 100 (100-55) = mex 2.43 x 26 x (55-15) 3x4.2 x 45= mix 2.43 x 40 me = 5x4,2x45 2.63x40 [me= 9.72 leylsec] moss flowrote of glycerine is 9.72 kg see.

overall Heat tronsfer coefficient 9 = UACOM - where A Effective heat onster area com- Legerrithmic mean temp aliggen en (0./02) 70 counter low Hea cronzer Tea: 1600- 55 - 45 T -55-15= 40. i = The 0 2 = The 45-40 = en(40/40) com 42.45 a = mhx Chx (The Tha) - 5 X 4.24 103 x (100-55) a = 945 kg/sec. CN: No f te bes) a = NIXDXL - pox TX 0.015*2 = 0.9424 m² egn becomes 9458103=0x0.94248 42.45 u= 9458108 0.9426x42.45 Tu = 23.622 kg/m2K/ overore heat transfer coefficient is 23.622 kg/mk