Homework Answers
False statement
The highest wall shear stress and the higher heat transfer coefficient occur at the inlet where the thickness of boundary layer is the smallest and decrease to the fully developed i.e. exit of tube.
The pressure drop and heat flux is higher at the entrance region(not fully developed)
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For turbulent forced convection in a tube, the heat flux will be lower near the inlet...
0 In spite of being forced', a forced convection is not as efficient as free convection...
0 In spite of being forced', a forced convection is not as efficient as free convection in removing heat from a vertical hot plate. True / False (ü) Computer components are designed such that the are cooled due to natural convection. This cooling will be even more effective if the computer is on the space station. True / False (ii) Birds take advantage of natural convection while soaring. True / False (iv) A fictitious planet similar to earth has an...
(0) In spite of being 'forced, a forced convection is not as efficient as free convection...
(0) In spite of being 'forced, a forced convection is not as efficient as free convection in removing heat from a vertical hot plate. True / False (ii) Computer components are designed such that the are cooled due to natural convection. This cooling will be even more effective if the computer is on the space station. True / False (iii) Birds take advantage of natural convection while soaring. True / False (iv) A fictitious planet similar to earth has an...
Superimposed free convection over forced convection will yield higher heat trans- fer coefficients for: (a) gas...
Superimposed free convection over forced convection will yield higher heat trans- fer coefficients for: (a) gas heating in a horizontal tube (b)iquid cooling in a horizontal tube (c) liquid heating in a vertical tube with upflow (d) gas cooling in a vertical tube with downflow 7.38 7.39 The free convection effect in a forced flow may be significant for (a) small (T T (c) shell-and-tube exchanger (b) highly compact exchanger (d) high Reynolds number 7.35 Compared to the constant-viscosity case,...
QUESTION 10 Which option given below is wrong Three modes of heat transfer are: conduction, convection,...
QUESTION 10 Which option given below is wrong Three modes of heat transfer are: conduction, convection, and radiation. In free convection, the Grashof number is not used as a criterion for laminar and turbulent flow. The conduction heat transfer rate unit is W. The Grashof number in free convection plays the same role as the Reynolds number in forced convection.
The convection heat flux from a surface of area and length at to a fluid at...
The convection heat flux from a surface of area and length at to a fluid at T is given by Og" = ha(T. -1.) o (1,-1.) q" = hA º p =,(,-2) ° 4' =h(T.-T.)
(40 points) Engine oil flows at a rate of 1 kg/s through a 5-mm diameter smooth straight tube. Th...
(40 points) Engine oil flows at a rate of 1 kg/s through a 5-mm diameter smooth straight tube. The oil has an inlet temperature of 47°C and it is desired to heat the oil to a mean temperature of 87°C at the exit of the tube. The surface of the tube is maintained at 150°C. Assuming the flow is fully developed both hydrodynamically and thermally, determine the required length of the tube. Note: by calculating Reynolds number at the entrance...
Which of the following statements are true (could be multiple) for internal flow through a pipe?...
Which of the following statements are true (could be multiple) for internal flow through a pipe? In laminar flow, the Nusselt is higher for constant wall temperature compared to that for constant heat flux. In turbulent flow, the Nusselt number is higher at the pipe exit than at the pipe entrance In laminar flow, the Nusselt number is lower at the pipe exit than at the pipe entrance In laminar fully developed flow, the Nusselt number is independent of Reynolds...
QUESTION 1: Heat Exchanges A concentric tube parallel floween s hot water saturated liquid from 30...
QUESTION 1: Heat Exchanges A concentric tube parallel floween s hot water saturated liquid from 30 to 90%Catate of St. The exh , having thermopla properties similar to air, enter and exit the exchange 254 and 100 p ectively. The heat force 1000 W/mK The water pipe has a diameter of 50 cm a) Determine the required length for the exchanger. b) Assuming water flow inside the tube to be fully developed, estimate the convection heat transfer coefficient c) If...
A) Determine the convection heat transfer coefficient for the flow of air. [W/m2·°C] B) Determine the...
A) Determine the convection
heat transfer coefficient for the flow of air.
[W/m2·°C]
B) Determine the convection heat transfer coefficient for water.
[W/m2·°C]
The velocity of the fluid is 9 m/s in an 8-cm diameter and 7-m-long tube when the tube is subjected to uniform heat flux from all surfaces. Use fluid properties at 25°C. Water or Air D 8 cm L=7 m Given: The properties of air at 25°C are: k 0.02551 W/m."C v 1.562 10-5 m2/s Pr =...
q = 200W, To = 24.8 degree C πχ S6. The surface heat flux in a...
q = 200W, To = 24.8 degree
C
πχ S6. The surface heat flux in a tube is specified as q"-a sin (-) where a 10,000 W/m2 and L- 0.5 m. Assume water properties and an inlet temperature of 20C. The mass flow rate is 0.01 kg/s and the tube diameter is 2 cm. a) Determine an algebraic expression for the bulk mean temperature of the water as a function of x. b) Determine algebraic expressions for the outlet temperature...
0 In spite of being forced', a forced convection is not as efficient as free convection in removing heat from a vertical hot plate. True / False (ü) Computer components are designed such that the are cooled due to natural convection. This cooling will be even more effective if the computer is on the space station. True / False (ii) Birds take advantage of natural convection while soaring. True / False (iv) A fictitious planet similar to earth has an...
(0) In spite of being 'forced, a forced convection is not as efficient as free convection in removing heat from a vertical hot plate. True / False (ii) Computer components are designed such that the are cooled due to natural convection. This cooling will be even more effective if the computer is on the space station. True / False (iii) Birds take advantage of natural convection while soaring. True / False (iv) A fictitious planet similar to earth has an...
Superimposed free convection over forced convection will yield higher heat trans- fer coefficients for: (a) gas heating in a horizontal tube (b)iquid cooling in a horizontal tube (c) liquid heating in a vertical tube with upflow (d) gas cooling in a vertical tube with downflow 7.38 7.39 The free convection effect in a forced flow may be significant for (a) small (T T (c) shell-and-tube exchanger (b) highly compact exchanger (d) high Reynolds number 7.35 Compared to the constant-viscosity case,...
QUESTION 10 Which option given below is wrong Three modes of heat transfer are: conduction, convection, and radiation. In free convection, the Grashof number is not used as a criterion for laminar and turbulent flow. The conduction heat transfer rate unit is W. The Grashof number in free convection plays the same role as the Reynolds number in forced convection.
The convection heat flux from a surface of area and length at to a fluid at T is given by Og" = ha(T. -1.) o (1,-1.) q" = hA º p =,(,-2) ° 4' =h(T.-T.)
(40 points) Engine oil flows at a rate of 1 kg/s through a 5-mm diameter smooth straight tube. The oil has an inlet temperature of 47°C and it is desired to heat the oil to a mean temperature of 87°C at the exit of the tube. The surface of the tube is maintained at 150°C. Assuming the flow is fully developed both hydrodynamically and thermally, determine the required length of the tube. Note: by calculating Reynolds number at the entrance...
Which of the following statements are true (could be multiple) for internal flow through a pipe? In laminar flow, the Nusselt is higher for constant wall temperature compared to that for constant heat flux. In turbulent flow, the Nusselt number is higher at the pipe exit than at the pipe entrance In laminar flow, the Nusselt number is lower at the pipe exit than at the pipe entrance In laminar fully developed flow, the Nusselt number is independent of Reynolds...
QUESTION 1: Heat Exchanges A concentric tube parallel floween s hot water saturated liquid from 30 to 90%Catate of St. The exh , having thermopla properties similar to air, enter and exit the exchange 254 and 100 p ectively. The heat force 1000 W/mK The water pipe has a diameter of 50 cm a) Determine the required length for the exchanger. b) Assuming water flow inside the tube to be fully developed, estimate the convection heat transfer coefficient c) If...
A) Determine the convection
heat transfer coefficient for the flow of air.
[W/m2·°C]
B) Determine the convection heat transfer coefficient for water.
[W/m2·°C]
The velocity of the fluid is 9 m/s in an 8-cm diameter and 7-m-long tube when the tube is subjected to uniform heat flux from all surfaces. Use fluid properties at 25°C. Water or Air D 8 cm L=7 m Given: The properties of air at 25°C are: k 0.02551 W/m."C v 1.562 10-5 m2/s Pr =...
q = 200W, To = 24.8 degree
C
πχ S6. The surface heat flux in a tube is specified as q"-a sin (-) where a 10,000 W/m2 and L- 0.5 m. Assume water properties and an inlet temperature of 20C. The mass flow rate is 0.01 kg/s and the tube diameter is 2 cm. a) Determine an algebraic expression for the bulk mean temperature of the water as a function of x. b) Determine algebraic expressions for the outlet temperature...
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