Fundamentals of Heat and Mass Transfer
7th Edition
ISBN: 9780470501979
Author: Frank P. Incropera, David P. DeWitt, Theodore L. Bergman, Adrienne S. Lavine
Publisher: Wiley, John & Sons, Incorporated
expand_more
expand_more
format_list_bulleted
Videos
Textbook Question
Chapter 7, Problem 7.9P
An electric air heater consists of a horizontal array of thin metal strips that are each 10 mm long in the direction of an airstream that is in parallel flow over the top of the strips. Each strip is 0.2 m wide, and 25 strips are arranged side by side, forming a continuous and smooth surface over which the air flows at 2 m/s. During operation, each strip is maintained at 500°C and the air is at 25°C.
- What is the rate of convection heat transfer from the first strip? The fifth strip? The tenth strip? All the strips?
- For air velocities of 2, 5, and 10 m/s, determine the convection heat rates for all the locations of part (a). Represent your results in tabular or bar graph form.
- Repeat part (b), but under conditions for which the flow is fully turbulent over the entire array of strips.
Expert Solution & Answer
Want to see the full answer?
Check out a sample textbook solution
Students have asked these similar questions
Problem#6*
A preheater involves the use of condensing steam at 100°C on the inside of a bank of tubes to heat air that
enters at 1 atmosphere and 15°C. The air moves at 8 m/s in cross flow over the tubes. Each tube is 2 m
long and has an outside diameter of 5 mm. The bank consists of 196 tubes in a square, aligned array in
which the distance between tube centers is 15 mm. What is the temperature of the air after passing through
the tubes. Also, what is the pressure drop associated with the air flow?
Compute the Nu numbers for air at 40°C flowing with 4 m/s speed over the following:
1) A Copper sphere of 5 cm in diameter with 80°C isothermal surface temperature
2) A circular Aluminum pipe of 6 cm in diameter with 80°C isothermal surface temperature
3) A bank of 20x20 5-mm diameter tubes arranged in-line with center-to-center distance of
20 mm. Each tube is assumed to have isothermal temperature of 80°C.
Please show detailed calculations.
An oil preheater consists of a single tube of 10-mm diameter and 5-m length, with its surface maintained at 180°C by swirling
combustion gases. The engine oil (new) enters at 70°C. What flow rate, in kg/h, must be supplied to maintain an oil outlet temperatur
of 105°C? What is the corresponding heat transfer rate, in W?
m =
kg/h
W
Chapter 7 Solutions
Fundamentals of Heat and Mass Transfer
Ch. 7 - Consider the following fluids at a film...Ch. 7 - Engine oil at 100C and a velocity of 0.1 m/s flows...Ch. 7 - Consider steady, parallel flow of atmospheric air...Ch. 7 - Consider a liquid metal (Pr1), with free stream...Ch. 7 - Consider the velocity boundary layer profile for...Ch. 7 - Consider a steady, turbulent boundary layer on and...Ch. 7 - Consider flow over a flat plate for which it is...Ch. 7 - A flat plate of width 1 m is maintained at a...Ch. 7 - An electric air heater consists of a horizontal...Ch. 7 - Consider atmospheric air at 25C and a velocity of...
Ch. 7 - Repeat Problem 7.11 for the case when the boundary...Ch. 7 - Consider water at 27°C in parallel flow over an...Ch. 7 - Explain under what conditions the total rate of...Ch. 7 - In fuel cell stacks, it is desirable to operate...Ch. 7 - The roof of a refrigerated truck compartment is of...Ch. 7 - The top surface of a heated compartment consists...Ch. 7 - Calculate the value of the average heat transfer...Ch. 7 - The proposed design for an anemometer to determine...Ch. 7 - Steel (AISI 1010) plates of thickness =6mm and...Ch. 7 - Consider a rectangular fin that is used to cool a...Ch. 7 - The Weather Channel reports that it is a hot,...Ch. 7 - In the production of sheet metals or plastics, it...Ch. 7 - An array of electronic chips is mounted within a...Ch. 7 - A steel strip emerges from the hot roll section of...Ch. 7 - In Problem 7.23. an anemometer design was...Ch. 7 - One hundred electrical components, each...Ch. 7 - The boundary layer associated with parallel flow...Ch. 7 - Forced air at 250C and 10 m/s is used to cool...Ch. 7 - Air at atmospheric pressure and a temperature of...Ch. 7 - Consider a thin, 50mm50mm fuel cell similar to...Ch. 7 - The cover plate of a flat-plate solar collector is...Ch. 7 - An array of 10 silicon chips, each of length...Ch. 7 - A square (10mm10mm) silicon chip is insulated on...Ch. 7 - A circular pipe of 25-mm outside diameter is...Ch. 7 - An L=1-m- long vertical copper tube of inner...Ch. 7 - A long, cylindrical, electrical heating element of...Ch. 7 - Consider the conditions of Problem 7.49, but now...Ch. 7 - Pin fins are to be specified for use in an...Ch. 7 - Prob. 7.52PCh. 7 - Prob. 7.53PCh. 7 - Hot water at 500C is routed from one building in...Ch. 7 - In a manufacturing process, long aluminum rods of...Ch. 7 - Prob. 7.58PCh. 7 - To determine air velocity changes, it is proposed...Ch. 7 - Determine the convection heat loss from both the...Ch. 7 - Prob. 7.63PCh. 7 - Prob. 7.64PCh. 7 - Prob. 7.67PCh. 7 - A thermocouple is inserted into a hot air duct to...Ch. 7 - Consider a sphere with a diameter of 20 mm and a...Ch. 7 - Prob. 7.76PCh. 7 - A spherical, underwater instrument pod used to...Ch. 7 - Worldwide. over a billion solder balls must be...Ch. 7 - Prob. 7.80PCh. 7 - Prob. 7.81PCh. 7 - Consider the plasma spray coating process of...Ch. 7 - Prob. 7.83PCh. 7 - Tissue engineering involves the development of...Ch. 7 - Consider temperature measurement in a gas stream...Ch. 7 - Prob. 7.89PCh. 7 - A preheater involves the use of condensing steam...Ch. 7 - Prob. 7.91PCh. 7 - A tube bank uses an aligned arrangement of...Ch. 7 - A tube bank uses an aligned arrangement of...Ch. 7 - Repeat Problem 7.94, but with NL=7,NT=10, and...Ch. 7 - Heating and cooling with miniature impinging jets...Ch. 7 - A circular transistor of 10-mm diameter is cooled...Ch. 7 - A long rectangular plate of AISI 304 stainless...Ch. 7 - A cryogenic probe is used to treat cancerous skin...Ch. 7 - Prob. 7.103PCh. 7 - Prob. 7.104PCh. 7 - Prob. 7.105PCh. 7 - Consider the packed bed of aluminum spheres...Ch. 7 - Prob. 7.108PCh. 7 - Prob. 7.109PCh. 7 - Prob. 7.111PCh. 7 - Packed beds of spherical panicles can be sintered...Ch. 7 - Prob. 7.114PCh. 7 - Prob. 7.116PCh. 7 - Prob. 7.117PCh. 7 - Prob. 7.118PCh. 7 - Prob. 7.119PCh. 7 - Prob. 7.120PCh. 7 - Dry air at 35°C and a velocity of 20 m/s flows...Ch. 7 - Prob. 7.123PCh. 7 - Benzene, a known carcinogen, has been spilled on...Ch. 7 - Prob. 7.125PCh. 7 - Prob. 7.126PCh. 7 - Condenser cooling water for a power plant is...Ch. 7 - Prob. 7.128PCh. 7 - In a paper-drying process, the paper moves on a...Ch. 7 - Prob. 7.131PCh. 7 - Prob. 7.132PCh. 7 - Prob. 7.133PCh. 7 - Prob. 7.134PCh. 7 - Prob. 7.136PCh. 7 - It has been suggested that heat transfer from a...Ch. 7 - Prob. 7.138PCh. 7 - Cylindrical dry-bulb and wet-bulb thermometers are...Ch. 7 - The thermal pollution problem is associated with...Ch. 7 - Cranberries are harvested by flooding the bogs in...Ch. 7 - A spherical drop of water, 0.5 mm in diameter, is...Ch. 7 - Prob. 7.143PCh. 7 - Prob. 7.144PCh. 7 - Prob. 7.145PCh. 7 - Prob. 7.146PCh. 7 - Prob. 7.147PCh. 7 - Consider an air-conditioning system composed of a...Ch. 7 - Prob. 7.149P
Knowledge Booster
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, mechanical-engineering and related others by exploring similar questions and additional content below.Similar questions
- A tube bank uses an aligned arrangement of 15-mm-diameter tubes with ST = S = 30 mm. There are 10 rows of tubes with 50 tubes in each row. Consider an application for which cold water flows through the tubes, maintaining the outer surface temperature at 40°C, while flue gases at 427°C and a velocity of 7 m/s are in cross flow over the tubes. The properties of the flue gas may be approximated as those of atmospheric air at 427°C. What is the total rate of heat transfer per unit length of the tubes in the bank, in kW/m? i 89 kW/marrow_forwardYou can skip if you are unsure.arrow_forwardA square isothermal chip is of width 5mm on a side mounted in a substrate such that its side and back surfaces are well insulated, while the front surface is exposed to the flow of coolant at 15C. From reliability considerations, the chip temperature must not exceed 85C. If air is used as a coolant, h = 200W/m2. If a dielectric liquid is used as coolant, h = 3000W/m2. What is the difference in maximum allowable power through the chip between the two coolants? (answer in W) *arrow_forward
- A tube bank uses an aligned arrangement of 10-mm-diameter tubes with ST = SL = 20 mm. There are 10 rows of tubes with 50 tubes in each row. Consider an application for which cold water flows through the tubes, maintaining the outer surface temperature at 27°C, while flue gases at 427°C and a velocity of 5 m/s are in cross flow over the tubes. The properties of the flue gas may be approximated as those of atmospheric air at 427oC. What is the total rate of heat transfer per unit length of the tubes in the bank?arrow_forwardExperiments have been conducted on a metallic cylinder 12.7 mm in diameter and 94 mm long. The cylinder is heated internally by an electrical heater and is subjected to a cross flow of air in a low-speed wind tunnel. Under a specific set of operating conditions for which the upstream air velocity and temperature were maintained at V = 10 m/s and 26.2°C, respectively, the heater power dissipation was measured to be P = 46 W, while the average cylinder surface temperature was determined to be T, = 128.4°C. It is estimated that 15% of the power dissipation is lost through the cumulative effect of surface radiation and conduction through the endpieces. Thermocouple for measuring airstream temperature Pitot tube for determining velocity Wind tunnel Power leads to electrical heater Heated cylinder Insulated endpiece Thermocouple leads 1. Determine the convection heat transfer coefficient from the experimental observations. 2. Compare the experimental result with the convection coefficient…arrow_forwardAn insulated steam pipe is used to transport high-temperature steam from one building to another. The pipe has a diameter of 500 mm, a surface temperature of 164 °C and is exposed to ambient air at -10 °C. The pipe is subjected to an extermal forced convection as the air moves in a cross-flow over the pipe at a speed of 5 m/s (see figure below). a. What are the main assumptions? b. What is the heat loss per unit length of pipe without insulation? c. What is the heat loss per unit length of pipe if the insulation thickness is 10 mm? V = 5 m/s Too= -10 °C Air Tsi = 150 °C Insulation k, = 0.026 W/m-K D = 500 mm Ts.o Os8s 50 mm Steam Thermophysical Properties of Air at Atmospheric Pressure' k 10 4.107 (N-s/m) v• 10 (m/s) a 10 (m/s) T (K) (kg/m') (kJ/kg - K) (W/m K) Pr 100 3.5562 1.032 71.1 2.00 9.34 2.54 0.786 150 2.3364 1.012 103.4 4.426 13.8 5.84 0.758 200 1.7458 1.007 132.5 7.590 18.1 10.3 0.737 250 1.3947 1.006 159.6 11.44 22.3 15.9 0.720 300 1.1614 1.007 184.6 15.89 26.3 22.5 0.707…arrow_forward
- The pressure is 101.32 kPa and the air velocity at 316.5 k is 0.61m / s. The surface of the sphere is 277.76 k and its average diameter is 114 mm. Calculate the heat transfer coefficient for the air blown aroundarrow_forwardA thin, flat plate of length L = 1 m seperates two airstreams that are in parallel flow over opposite surfaces of the plate. One airstream has a temperature of T,1=200°C and a velocity of uo,1= 60 m/s, while the other airstream has a temperature of T,2= = 25°C and a velocity 10 m/s. What is the heat flux between the two streams at the mid point of the of u0,2 plate?arrow_forwardA flat plate 1.0 m wide and 1.0m long is placed in a wind tunnel. The temperature and the velocity of free stream air is 10°C and 80 m/s respectively. The flow over the whole length of the plate is made turbulent with the help of a turbulizing grid placed upstream of the plate. Calculate the mean value of the heat transfer coefficient from the surface of the plate.arrow_forward
- Problem#4* - Design the optimal location of triggering flow transition to maximize the cooling efficiency of a flat plate. The boundary layer associated with parallel flow over an isothermal plate may be "tripped" at any x- location by using a fine wire that is stretched across the width of the plate. Determine the value of the critical Reynolds number Rex,c, that is associated with the optimal location of the trip wire from the leading edge that will result in maximum heat transfer from a warm plate to a cooler fluid. Assume the Nusselt number correlations provided in the text for laminar and turbulent flows apply in the laminar and turbulent regions (mixing laminar and turbulent flows, CASE C in your handout notes), respectively.arrow_forwardProblem 1 Water at 50°C flows over a large plate at a velocity of 30.0 cm/s. The plate is 1.0 m long in the flow direction and its surface is maintained at a uniform temperature of 10.0°C. Calculate the steady rate of heat transfer per unit width of the plate. Remember the flow over the plate is laminar when Re < 5× 105.arrow_forwardi need the answer quicklyarrow_forward
arrow_back_ios
SEE MORE QUESTIONS
arrow_forward_ios
Recommended textbooks for you
Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning
Principles of Heat Transfer (Activate Learning wi...
Mechanical Engineering
ISBN:9781305387102
Author:Kreith, Frank; Manglik, Raj M.
Publisher:Cengage Learning
Heat Transfer – Conduction, Convection and Radiation; Author: NG Science;https://www.youtube.com/watch?v=Me60Ti0E_rY;License: Standard youtube license