just now i sent this questions.
this is the answer given. however the answer i afraid that he used formula that is not for constant surface temperature and noncircular formula.
this is the formula foe the noncircular tube. because the question ask about triangle.
my problem is, i cannot answer question 1(b) that ask the heat transfer coefficient, h. please help me. thank you.
this pic is a note on constant surface temperature. page 482
ref: HEAT AND MASS TRANSFER: FUNDAMENTALS &
APPLICATIONS, FIFTH EDITION. yunus A. Cengel.
Homework Answers
Question 2.
In the interest of maximizing the cooling rate, the cans should be laid vertically in the compartment.
Explanation: If the can is laid vertically, the minimum surface (60 mm) of the can is touching the refrigerator plates, hence it will get more space (150 mm) for cooling at a faster rate.
Add Answer to:
just now i sent this questions.
this is the answer given. however the answer i afraid...
2) (35 pt) Atmospheric air at 25 Centers a duct having a cross section of an...
2) (35 pt) Atmospheric air at 25 Centers a duct having a cross section of an equilateral triangle 2 cm on a side with a velocity of 1.5 m/s. The length of the duct is 10 m. A constant heat flux is imposed on the duct wall. The mean temperature of the air at the duct exit is 75 °C. a. Is the flow at the duct exit hydrodynamically and thermally fully developed? Show. T-75 °C b. Calculate the convection...
Problem 3 (20 points) A cross-flow heat exchanger consists of a bundle of 32 tubes in a long duct. Hot water at 150°C and a mean velocity of 0.5 m/s enters the tubes having inner and outer diameters...
Problem 3 (20 points) A cross-flow heat exchanger consists of a bundle of 32 tubes in a long duct. Hot water at 150°C and a mean velocity of 0.5 m/s enters the tubes having inner and outer diameters of 10.2mm and 12.5mm and has to be cooled to 136°C. The tubes are made of steel of thermal conductivity k-40 W/m.K. Air at 10°c enters the exchanger (unfinned) with a volumetric flow rate of 1.0 m3/s. The convective heat transfer coefficient...
a. (2 pts.) The film temperature, used to evaluate properties, for internal flow is the average...
a. (2 pts.) The film temperature, used to evaluate properties, for internal flow is the average of the surface temperature and the external free stream fluid temperature. True or False. 1. b. (2 pts.) The local convection coefficient, h, around the circumference of a cylinder in cross flow is constant (it does not vary with position as you travel around the cylinder.) True or False c. (2 pts.) For internal fully developed flow the convection coefficient, h, decreases as the...
#1. To reduce nitrogen oxide emissions from a diesel engine, one commonly used strategy is exhaust...
#1. To reduce nitrogen oxide emissions from a diesel engine, one commonly used strategy is exhaust gas recirculation (EGR). In a stack-type EGR cooler, exhaust gases flow through tubes with a rectangular cross-section (4 mm x 6 mm). In each tube, the mass flow rate of exhaust gases is 0.0001 kg/s; the gases enter at 140°C while the inner surface of each tube is maintained at 80°C due to water being circulated as a coolant. The length of the tube...
1. Consider a 5 m long rectangular tube with a hot fluid with the properties specified in the diagram below. The inlet...
1. Consider a 5 m long rectangular tube with a hot fluid with the properties specified in the diagram below. The inlet and outlet fluid temperatures are controlled to vary from 20 to 30 °C by applying a constant heat flux at the surface of the tube. We can ignore conduction and radiation phenomena in this problem and assume that the fluid velocity profile does not change within the tube. Using the Nu correlation from table 8.1 below, find the...
this is the full problem. 11.1 An industrial boiler consists of tubes inside of which flow hot combustion gases. Water...
this is the full problem.
11.1 An industrial boiler consists of tubes inside of which flow hot combustion gases. Water boils on the exterior of the tubes. When installed, the clean boiler has an over- all heat transfer coefficient of 300 W/m2- K. Based on experience, it is anticipated that the fouling factors on the inner and outer surfaces will increase linearly with time as Rat and R = at where a;= 2.5 x 10-1" m2- K/Ws and a =...
Explain Convection 1. Describe the factors that affect the value of the convection coefficient 2. Explain why and how velocity and thermal boundary layers form 3. Explain how turbulence enhances c...
Explain
Convection 1. Describe the factors that affect the value of the convection coefficient 2. Explain why and how velocity and thermal boundary layers form 3. Explain how turbulence enhances convection heat transfer 4. Describe the significance of the Reynold's number, Nusselt number, and the Prandtl number 5. List common situations where external convection occurs 6. Explain the importance of the film temperature and use it to specify thermophysical properties of a fluid 7. Explain the significance of boundary layer...
1. (25 pts) Answer the following conceptual questions. Write down full explanations and derivations on a...
1. (25 pts) Answer the following conceptual questions. Write down full explanations and derivations on a clean piece of paper. h, 8 h(x) 80) 1 a. The effect of transition from laminar to turbulent flow on local velocity boundary layer thickness, 8(x) and local convection coefficient, h(x) for steady flow over an isothermal plate is illustrated in the following figure. Why does the convection coefficient decrease with x in the laminar region? How would the local heat flux change with...
Problem 11.051 Exhaust gas from a furnace is used to preheat the combustion air supplied to...
Problem 11.051 Exhaust gas from a furnace is used to preheat the combustion air supplied to the furnace burners. The gas, which has a flow rate of 15 kg/s and an inlet temperature of 1100 K, passes through a bundle of tubes, while the air, which has a flow rate of 10 kg/s and an inlet temperature of 300 K, is in cross flow over the tubes. The tubes are unfinned, and the overall heat transfer coefficient is 90 W/m2...
Please solve question 7.3 and it is depends on 7.2 so I upload the two questions...
Please solve question 7.3 and it is depends on 7.2 so I upload
the two questions
7.2 Consider fully developed laminar flow of a fluicd inside a wide rectangular duct with both the upper and lower surface at uniform surface temperature, as schematically shown in the figure below. The effect of the two sides of the duct is neglected (W H), and at a location far from the entrance the velocity distribution is assumed to be uniform, 7.5 n(x) =...
2) (35 pt) Atmospheric air at 25 Centers a duct having a cross section of an equilateral triangle 2 cm on a side with a velocity of 1.5 m/s. The length of the duct is 10 m. A constant heat flux is imposed on the duct wall. The mean temperature of the air at the duct exit is 75 °C. a. Is the flow at the duct exit hydrodynamically and thermally fully developed? Show. T-75 °C b. Calculate the convection...
Problem 3 (20 points) A cross-flow heat exchanger consists of a bundle of 32 tubes in a long duct. Hot water at 150°C and a mean velocity of 0.5 m/s enters the tubes having inner and outer diameters of 10.2mm and 12.5mm and has to be cooled to 136°C. The tubes are made of steel of thermal conductivity k-40 W/m.K. Air at 10°c enters the exchanger (unfinned) with a volumetric flow rate of 1.0 m3/s. The convective heat transfer coefficient...
a. (2 pts.) The film temperature, used to evaluate properties, for internal flow is the average of the surface temperature and the external free stream fluid temperature. True or False. 1. b. (2 pts.) The local convection coefficient, h, around the circumference of a cylinder in cross flow is constant (it does not vary with position as you travel around the cylinder.) True or False c. (2 pts.) For internal fully developed flow the convection coefficient, h, decreases as the...
#1. To reduce nitrogen oxide emissions from a diesel engine, one commonly used strategy is exhaust gas recirculation (EGR). In a stack-type EGR cooler, exhaust gases flow through tubes with a rectangular cross-section (4 mm x 6 mm). In each tube, the mass flow rate of exhaust gases is 0.0001 kg/s; the gases enter at 140°C while the inner surface of each tube is maintained at 80°C due to water being circulated as a coolant. The length of the tube...
1. Consider a 5 m long rectangular tube with a hot fluid with the properties specified in the diagram below. The inlet and outlet fluid temperatures are controlled to vary from 20 to 30 °C by applying a constant heat flux at the surface of the tube. We can ignore conduction and radiation phenomena in this problem and assume that the fluid velocity profile does not change within the tube. Using the Nu correlation from table 8.1 below, find the...
this is the full problem.
11.1 An industrial boiler consists of tubes inside of which flow hot combustion gases. Water boils on the exterior of the tubes. When installed, the clean boiler has an over- all heat transfer coefficient of 300 W/m2- K. Based on experience, it is anticipated that the fouling factors on the inner and outer surfaces will increase linearly with time as Rat and R = at where a;= 2.5 x 10-1" m2- K/Ws and a =...
Explain
Convection 1. Describe the factors that affect the value of the convection coefficient 2. Explain why and how velocity and thermal boundary layers form 3. Explain how turbulence enhances convection heat transfer 4. Describe the significance of the Reynold's number, Nusselt number, and the Prandtl number 5. List common situations where external convection occurs 6. Explain the importance of the film temperature and use it to specify thermophysical properties of a fluid 7. Explain the significance of boundary layer...
1. (25 pts) Answer the following conceptual questions. Write down full explanations and derivations on a clean piece of paper. h, 8 h(x) 80) 1 a. The effect of transition from laminar to turbulent flow on local velocity boundary layer thickness, 8(x) and local convection coefficient, h(x) for steady flow over an isothermal plate is illustrated in the following figure. Why does the convection coefficient decrease with x in the laminar region? How would the local heat flux change with...
Problem 11.051 Exhaust gas from a furnace is used to preheat the combustion air supplied to the furnace burners. The gas, which has a flow rate of 15 kg/s and an inlet temperature of 1100 K, passes through a bundle of tubes, while the air, which has a flow rate of 10 kg/s and an inlet temperature of 300 K, is in cross flow over the tubes. The tubes are unfinned, and the overall heat transfer coefficient is 90 W/m2...
Please solve question 7.3 and it is depends on 7.2 so I upload
the two questions
7.2 Consider fully developed laminar flow of a fluicd inside a wide rectangular duct with both the upper and lower surface at uniform surface temperature, as schematically shown in the figure below. The effect of the two sides of the duct is neglected (W H), and at a location far from the entrance the velocity distribution is assumed to be uniform, 7.5 n(x) =...
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