Question 4 of 5 < > -/ 20 View Policies Current Attempt in Progress Under conditions for which the same room temperature is maintained by a heating or cooling system, it is not uncommon for a person to feel chilled in the winter but comfortable in the summer. Consider a room whose air temperature is maintained at 16°C throughout the year, while the walls of the room are nominally at 28°C and 14°C in the summer and winter, respectively. The exposed surface of a person in the room may be assumed to be at a temperature of 32°C throughout the year and to have an emissivity of 0.90. The coefficient associated with heat transfer by natural convection between the person and the room air is approximately 2 W/m2-K. Calculate the following. Heat flux due to convection: gbony = i W/m? Heat flux due to radiation in the summer: i W/m? Heat flux due to radiation in the winter: Tad i W/m2 Physical Properties Mathematical Functions

Question 4 of 5 < > -/ 20 View Policies Current Attempt in Progress Under conditions for which the same room temperature is maintained by a heating or cooling system, it is not uncommon for a person to feel chilled in the winter but comfortable in the summer. Consider a room whose air temperature is maintained at 16°C throughout the year, while the walls of the room are nominally at 28°C and 14°C in the summer and winter, respectively. The exposed surface of a person in the room may be assumed to be at a temperature of 32°C throughout the year and to have an emissivity of 0.90. The coefficient associated with heat transfer by natural convection between the person and the room air is approximately 2 W/m2-K. Calculate the following. Heat flux due to convection: gbony = i W/m? Heat flux due to radiation in the summer: i W/m? Heat flux due to radiation in the winter: Tad i W/m2 Physical Properties Mathematical Functions

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.

Chapter5: Analysis Of Convection Heat Transfer

Section: Chapter Questions

Problem 5.27P

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3.9 The heat transfer coefficients for the flow of 26.6°C air over a sphere of 1.25 cm in diameter are measured by observing the temperature-time history of a copper ball the same dimension. The temperature of the copper ball was measured by two thermocouples, one located in the center and the other near the surface. The two thermocouples registered, within the accuracy of the recording instruments, the same temperature at any given instant. In one test run, the initial temperature of the ball was 66°C, and the temperature decreased by 7°C in 1.15 min. Calculate the heat transfer coefficient for this case.
Using the information in Problem 1.22, estimate the ambient air temperature that could cause frostbite on a calm day on the ski slopes. 1.22 In order to prevent frostbite to skiers on chair lifts, the weather report at most ski areas gives both an air temperature and the wind-chill temperature. The air temperature is measured with a thermometer that is not affected by the wind. However, the rate of heat loss from the skier increases with wind velocity, and the wind-chill temperature is the temperature that would result in the same rate of heat loss in still air as occurs at the measured air temperature with the existing wind. Suppose that the inner temperature of a 3-mm-thick layer of skin with a thermal conductivity of 0.35W/mKis35C and the air temperature is 20C. Under calm ambient conditions the heat transfer coefficient at the outer skin surface is about 20W/m2K (see Table 1.4), but in a 40-mph wind it increases to 75W/m2K. If frostbite occurs when the skin temperature drops to about 10C, do you advise the skier to wear a face mask? What is the skin temperature drop due to the wind?
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Using Table 1.4 as a guide, prepare a similar table showing the orders of magnitude of the thermal resistances of a unit area for convection between a surface and various fluids.
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Examples of external data I can use to support the claim that the consumers living within regions with hot climate will buy the stainless steel pan with digital thermometer reading that is powered by the heat generated while cooking and that sales will be higher in summer.
What external data can I use to support the claim that the consumers living within regions with hot climate will buy the stainless steel pan with digital thermometer reading that is powered by the heat generated while cooking and that sales will be higher in summer?
The schematic below illustrates a tank formed from two zones, i.e. liquid and solid. The tank is heated from the left-side with a time-varying solar heat radiation g,ol =f(t) (Wim), while the right-side is kept at a low temperature T. The top surface of the tank is subjected to the ambient conditions, i.e. (hair & Tair ), while its bottom is thermally insulated. Conjugate heat transfer takes place between the two-physically different zones through the fluid-solid interface separating them, while fluid flow is induced due to buoyancy effects where the buoyancy force is approximated according to Boussinesq formulation Fiuoyaney=P0 Bg(T-To). Explain the following: 1- The assumptions required to simulate the below problem. 2- The conservation equations governing the transport phenomena in each zone. 3- The boundary conditions closing the mathematical model. 4- The discretized form of each conservation equation stated in (point 2) above. 5- The appropriate differencing scheme to be used for…
You are tasked to design a cooling system for an ice rink. A standard ice rink has surface area ofArink = 1580 m2 . In this design, a technologically advanced solid state thermoelectric generatingcooling plate is placed in between concrete slabs. The following diagram contains the dimensionalparameters of the design (a) In the space below, with your best effort to correspond to the above diagram, draw a thermalcircuit that establishes the relationship between the cooling plate’s heat rate, Q, and the system’stemperatures and thermal resistances. Label the appropriate dimensions, thermal conductivities,convection coefficient, and temperatures. Ignore effects from contact resistance. (b) Given that the temperature at the top surface of the ice must be T ice = -5°C, obtain the requiredheat rate Q that must be drawn by the cooling plate in units Kilowatts. Be careful of +/- sign.Answer: ____________________________ [kW] c) Using the thermal circuit you established in Part (a), obtain the…
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V:01 Expert Q&A Done Question 1: In your own words, write down the differences between thermodynamic and heat transfer. (3 Marks) Question 2: Estimate the heat loss per square metre of surface through a brick wall 0.5 m thick when the inner surface is at 400 K and the outside surface is at 300 K. The thermal conductivity of the brick may be taken as 0.7 W/mK. (2 Marks) Question 3: A furnace is constructed with 0.20 m of firebrick, 0.10 m of insulating brick, and 0.20 m of building brick. The inside temperature is 1200 K and the outside temperature is 330 K. If the thermal conductivities are as shown in the figure below, estimate the heat loss per unit area. (5 Marks) 1200 K 330 K Insulating brick X-0.10m k= 0.21 Ordinary brick X=0.20 m Fire brick X= 0.20 m k= 1.4 k= 0.7 (W/mK)