single-pass, cross-flow heat exchanger uses hot exhaust gases (mixed) to heat water (unmixed) from 30 to 70 °C at a rate of 3 kg/s. The exhaust gases, having thermophysical properties similar to air, enter and exit the exchanger at 200 and 100 °C, respectively. If the overall heat transfer coefficient is 200 W/m2 ·K, estimate the required surface area. Hint : from 30 to 70 °C at a rate of 3 kg/s.

single-pass, cross-flow heat exchanger uses hot exhaust gases (mixed) to heat water (unmixed) from 30 to 70 °C at a rate of 3 kg/s. The exhaust gases, having thermophysical properties similar to air, enter and exit the exchanger at 200 and 100 °C, respectively. If the overall heat transfer coefficient is 200 W/m2 ·K, estimate the required surface area. Hint : from 30 to 70 °C at a rate of 3 kg/s.

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 10.43P

See similar textbooks

Similar questions

10.1 In a heat exchanger, as shown in the accompanying figure, air flows over brass tubes of 1.8-cm 1D and 2.1-cm OD containing steam. The convection heat transfer coefficients on the air and steam sides of the tubes are , respectively. Calculate the overall heal transfer coefficient for the heal exchanger (a) based on the inner tube area and (b) based on the outer tube area.
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.
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.
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.
1. A long thin-walled double-pipe heat exchanger with tube and shell diameters of 1.0 cm and 2.5 cm, respectively, is used to condense refrigerant-134a by water at 20 0C. The refrigerant flows through the tube, with a convection heat transfer coefficient of 5000 W/m2 K. Water flows through the shell at a rate of 0.3 kg/s. Determine the overall heat transfer coefficient of this heat exchanger. If a 2-mm-thick layer of limestone (k = 1.3 W/m K) forms on the outer surface of the inner tube what will be new overall heat transfer coefficient
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.
What is the heat capacity rate? What can you say about the temperature changes of the hot and cold fluids in a heat exchanger if both fluids have the same capacity rate? What does a heat capacity of infinity for a fluid in a heat exchanger mean?
Hot water at 90°C flows on the inside of a 2.5-cm-ID steel tube with 0.8-mm wall thickness at a velocity of 4 m/s. This tube forms the inside of a double-pipe heat exchanger. The outer pipe has a 3.75-cm ID, and engine oil at 20°C flows in the annular space at a velocity of 7 m/s. Calculate the overall heat-transfer coefficient for this arrangement. The tube length is 6.0 m.
Hot water flowing at 0.015 m3/min enters the tube side of a counter current shell & tube heat exchanger at 80 C and leaves at 50 C. Cold oil flowing thru the shell at 0.05 m3/min, with density 800 kg/m3 and specific heat of 2.0 kJ/kg K, enters at 20 C. Consider water specific heat at 4.2 kJ/kg K and density of 988 kg/m3 at above condition, what is the approximate Log Mean Temperature Difference (LMTD)? Show the temperature profile completely labeled.
How does a cross-flow heat exchanger differ from a counter-flow one? What is the difference between mixed and unmixed fluids in cross-flow?
A cross-flow heat exchanger with both fluids unmixed has an overall heat transfer coefficient of 200 W/m2·K, and a heat transfer surface area of 400 m2. The hot fluid has a heat capacity of 40,000 W/K, while the cold fluid has a heat capacity of 80,000 W/K. If the inlet temperatures of both hot and cold fluids are 80°C and 20°C, respectively, determine (a) the exit temperature of the hot fluid and (b) the rate of heat transfer in the heat exchanger.
Answer the following questions about heat transfer in a double tube heat exchanger.(1) In a double tube heat exchanger in which hot and cold fluids flow into a countercurrent flow, the temperature of the hot fluid dropped from 60°C to 30°C, and the temperature of the cold fluid rose from 20°C to 55°C. Calculate the heat flux [kcal/m2h] when the overall heat transfer coefficient of this heat exchanger is constant at 69 kcal/m2h℃.(2) In a double tube heat exchanger in which hot and cold fluids flow in parallel flow, the temperature of the hot fluid dropped from 60°C to 45°C, and the temperature of the cold fluid rose from 20°C to 40°C. When the heat flux of this heat exchanger is 600 kcal/m2h, calculate the overall heat transfer coefficient of this heat exchanger [kcal/m2h℃].