11-75 PtD | Consider a shell and tube heat exchanger in a milk pasteurizing unit in which the milk flowing is to be heated from 20°C by hot water initially at 140°C and flow- ing at a rate of 5 kg/s. The milk flows through 30 thin-walled tubes with an inside diameter of 20 mm with each tube making 10 passes through the shell. The average convective heat trans- fer coefficients on the milk and water side are 450 W/m²-K and 1100 W/m²-K, respectively. In order to complete the pasteur- izing process and hence restrict the microbial growth in the milk, it is required to have the exit temperature of milk attain at least 70°C. As a design engineer, your job is to decide upon the shell width (tube length in each pass) so that the milk exit temperature of 70°C can be achieved. One of the design requirements is that the exit temperature of hot water should be at least 10°C higher than the exit temperature of milk.

11-75 PtD | Consider a shell and tube heat exchanger in a milk pasteurizing unit in which the milk flowing is to be heated from 20°C by hot water initially at 140°C and flow- ing at a rate of 5 kg/s. The milk flows through 30 thin-walled tubes with an inside diameter of 20 mm with each tube making 10 passes through the shell. The average convective heat trans- fer coefficients on the milk and water side are 450 W/m²-K and 1100 W/m²-K, respectively. In order to complete the pasteur- izing process and hence restrict the microbial growth in the milk, it is required to have the exit temperature of milk attain at least 70°C. As a design engineer, your job is to decide upon the shell width (tube length in each pass) so that the milk exit temperature of 70°C can be achieved. One of the design requirements is that the exit temperature of hot water should be at least 10°C higher than the exit temperature of milk.

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter10: Heat Exchangers

Section: Chapter Questions

Problem 10.32P

See similar textbooks

Similar questions

Water flowing in a long, aluminum lube is to be heated by air flowing perpendicular to the exterior of the tube. The ID of the tube is 1.85 cm, and its OD is 2.3 cm. The mass flow rate of the water through the tube is 0.65kg/s, and the temperature of the water in the lube averages 30C. The free-stream velocity and ambient temperature of the air are 10m/sand120C, respectively. Estimate the overall heat transfer coefficient for the heat exchanger using appropriate correlations from previous chapters. State all your assumptions.
In order to cool a mass flow rate of 25 Kg/h of air (cp = 1060 J/Kg oC) at 300 oC, it is passed through the tube side of a counter flow heat exchanger with a length of 2 m and 2.54 cm tube outer diameter. The cooling water, (cp = 4182 J/Kg oC and r = 1000 Kg/m3), enters the heat exchanger at a temperature of 30 oC with a volume flow rate of 0.3 Litre/min. If the overall heat transfer coefficient, U, is 5.83 W/m2 oC and the effectiveness of the heat exchanger 60 %, calculate the following: The heat transfer rate, The exit temperatures of both the water and the air, The surface area of the heat exchanger, The number of tubes used in the heat exchanger The capacity rate ratio.
A 2-shell passes and 4-tube passes heat exchanger is used to heat glycerin from 20oC to 50oC by hot water, which enters the thin-walled 2-cm-diameter tubes at 80oC and leaves at 40oC . The total length of the tubes in the heat exchanger is 60 m. The convection heat transfer coefficient is 25 W/m2K on the glycerin (shell) side and 160 W/m2K on the water (tube) side.Determine the rate of heat transfer in the heat exchanger (a) before any fouling and (b) after fouling with a fouling factor of 0.0006 m2K/W occurs on the outer surfaces of the tubes
A two-shell passes and four-tube passes heat exchanger is used to heat glycerin from 20°C to 50°C by hot water, which enters the thin-walled 2-cmdiameter tubes at 80°C and leaves at 40°C. The total length of the tubes in the heat exchanger is 60 m. The convection heat transfer coefficient is 25 W/m2∙K on the glycerin (shell) side and 160 W/m2∙K on the water (tube) side. Determine the rate of heat transfer in the heat exchanger (a) before any fouling and (b) after fouling with a fouling factor of 0.0006 m2∙K/W occurs on the outer surfaces of the tubes.
Steam is to be condensed on the shell side of a 1-shellpass and 8-tube-passes condenser, with 50 tubes in each pass,at 308C (hfg 5 2431 kJ/kg). Cooling water (cp 5 4180 J/kg?K)enters the tubes at 158C at a rate of 1800 kg/h. The tubes arethin-walled, and have a diameter of 1.5 cm and length of 2 mper pass. If the overall heat transfer coefficient is 3000 W/m2?K,determine (a) the rate of heat transfer and (b) the rate of condensation of steam.
A shell-and-tube heat exchanger with 1-shell pass and 20–tube passes is used to heat glycerin in the shell, with hot water in the tubes. The tubes are thin-walled and have a diameter of 4 cm and length of 2 m per pass. The water enters the tubes at 1000C at a rate of 0.5 kg/s and leaves at 550C. The glycerin enters the shell at 150C and leaves at 550C. Determine the mass flow rate of the glycerin and the overall heat transfer coefficient of the heat exchanger.
A long thin-walled double-pipe heat exchanger with tube and shell diameters of 2 cm and 4 cm, respectively, is used to condense refrigerant-134a by water at 20 C. The refrigerant flows through the tube, with a convection heat transfer coefficient of hi = 4000 W/m2 K.A 1-mm-thick layer of limestone (k = 1.2 W/mK) forms on the outer surface of the inner tube. Water flows through the shell at a rate of 0.4 kg/s. Determine the overall heat transfer coefficient U of this heat exchanger with and without the fouling factor, and the error in U introduced by neglecting the fouling factor. Comment the fouling effect on this heat exchanger.
Consider a double-pipe parallel-flow heat exchanger of length L. The inner and outer diameters of the inner tube are D1 and D2, respectively, and the inner diameter of the outer tube is D3. Explain how you would determine the two heat transfer surface areas Ai and Ao. When is it reasonable to assume Ai = Ao = As?
Engine oil at 20°C is to be heated to a temperature of 60°C by saturated steam at 1 atm in a double-pipe heat exchanger. The inner and outer diameters of the annular space are 4 cm and 6 cm, respectively, and engine oil enters the inner tube with a mean velocity of 0.8 m/s. The inner tube surface may be assumed to be isothermal at 100°C, and the outer tube is well insulated. Assuming fully developed Poiseulle flow for oil, determine the rate of heat transfer to the oil from the tube surface and find the tube length required to heat the oil to the indicated temperature using the empirical relations associated with convection heat transfer.
A shell-and-tube process heater is to be selected to heat water (cp = 4190 J/kg.K) from 20°C to 90°C by steam flowing on the shell side. The heat transfer load of the heater is 600 kW. If the inner diameter of the tubes is 1 cm and the velocity of water is not to exceed 3 m/s, determine how many tubes need to be used in the heat exchanger.
Water (cp = 4180 J/kg·K) enters the 2.5-cminternal- diameter tube of a double-pipe counter-flow heat exchanger at 17°C at a rate of 1.8 kg/s. Water is heated by steam condensing at 120°C (hfg = 2203 kJ/kg) in the shell. If the overall heat transfer coefficient of the heat exchanger is 700 W/m2·K, determine the length of the tube required in order to heat the water to 80°C using (a) the LMTD method and (b) the «-NTU method.
A shell-and-tube heat exchanger with 1-shell pass and14-tube passes is used to heat water in the tubes with geothermal steam condensing at 1208C (hfg 5 2203 kJ/kg) on the shellside. The tubes are thin-walled and have a diameter of 2.4 cmand length of 3.2 m per pass. Water (cp 5 4180 J/kg?K) entersthe tubes at 228C at a rate of 3.9 kg/s. If the temperature difference between the two fluids at the exit is 468C, determine(a) the rate of heat transfer, (b) the rate of condensation ofsteam, and (c) the overall heat transfer coefficient.