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A wet towel hangs on a clothes line under conditions for which one surface receives solar irradiation of
Determine the temperature
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Fundamentals of Heat and Mass Transfer
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- Ex1. A thin-walled cubical container that is 0.5 m by 0.5 m by 0.5 m is filled with ice water. The container is inside another .cubical container and the 3 cm gap between the containers is a vacuum. The outer surface of the inner container has an emissivity of 0.1 and a temperature of 1 C. The inner surface of the outer container has an emissivity of 0.3 and a temperature of 19 C. (a) What is the rate of heat transfer to the ice water? (b) If the container initially contains 1/2 ice and 1/2 water by volume, how long will it take for all the ice to be melted?arrow_forwardRequired information Consider a person whose exposed surface area is 21 m4, emissivity is 0.5, and surface temperature is 32°C. Given: 0 = 5.67×10-8 W/m2.K4 Determine the rate of heat loss from that person by radiation in a large room having walls at a temperature of 300 K (upto 3 decimal places). You must provide an answer before moving to the next part. The rate of heat loss from the person at 300K is W.arrow_forwardA thermocouple shielded by a layer of aluminum foil and copper with an emissivity of 0.05 and 0.02 is used to measure the temperature of hot gases flowing in a duct whose walls are maintained at T= 380K. Assuming emissivity of the thermocouple junction is 0.7 and convection heat transfer coefficient to be h= 130 W/m2.C, determine the radiation heat transfer from thermocouple junction to duct wall.arrow_forward
- A group of 25 power transistors, dissipating 1.5 W each, are to be cooled by attaching them to a black-anodized square aluminum plate and mounting the plate on the wall of a room at 30°C. The emissivity of the transistor and the plate surfaces is 0.9. Assuming the heat transfer from the back side of the plate to be negligible and the temperature of the surrounding surfaces to be the same as the air temperature of the room, determine the size of the plate if the average surface temperature of the plate is not to exceed 50°C.arrow_forwardConsider steady heat transfer between two large parallel plates at constant temperatures T1 = 300 K and T2 = 200 K that are L = 1 cm apart, as shown below. Assuming the surface to be black, determine the rate of heat transfer between the plates per unit surface area assuming the gap between the plates is a) filled with still air with k = 0.0219 W/m°C, b) free flowing air with h = 7.5 W/m2°C, c) evacuated, d) filled with urethane insulation with k = 0.026 W/m°C, and e) filled with superinsulation that has an apparent thermal conductivity k = 0.00002 W/m°Carrow_forwardConsider steady heat transfer between two large parallel plates at constant temperatures T1 = 300 K and T2 = 200 K that are L = 1 cm apart, as shown below. Assuming the surface to be black, determine the rate of heat transfer between the plates per unit surface area assuming the gap between the plates is a) filled with still air with k = 0.0219 W/m°C, b) free flowing air with h = 7.5 W/m2°C, c) evacuated, d) filled with urethane insulation with k = 0.026 W/m°C, and e) filled with superinsulation that has an apparent thermal conductivity k = 0.00002 W/m°C PLEASE ANSWER LETTER D AND E, THANK YOUarrow_forward
- The amount of radiation received per unit time by a person working near a radioactive source, commonly called the dose rate, is measured in rem hr-1. The safety regulations forbid dose rates in excess of 7.5 × 10-4 rem hr-1. The γ dose rate from the 4219K source is found to be 3 × 10-3 rem hr-1 at a distance of 1 m. What is the minimum distance from this source at which itis safe to work? After how long will it be safe to work at a distance of 1 m from the source?arrow_forwardThe car is outdoors in direct sunlight. The outside air temperature is 27 ° C. The temperature inside the car is maintained by air conditioning 22 ° C. What is the temperature of the outside surface of the car roof? The power density of solar radiation is 840 W / m2 and the absorption coefficient of the roof paint for radiation is 0.51. The heat transfer coefficient from the roof surface to the outside air is 11.6 W / (m2K), which also includes heat radiation from the surface to the environment. Radiation from the atmosphere to the car is not taken into account. The total thermal resistance of the car's roof structure is 1.0 m2K / W. The task does not look at any other part of the vehicle but only the roof. If you need an area, make a calculation per 1 m2.arrow_forwardQuestion 4:Consider a person standing in a room maintained at20°C at all times. The inner surfaces of the walls, floors, and ceiling of the house are observed to be at an average temperature of 12°C in winter and 23°C in summer. Determine threats of radiation heat transfer between this person and the surrounding surfaces in both summer and winter if the exposed surface area, emissivity, and the average outer surface temperature of the person are 1.6 m2, 0.95, and 32°C, respectively.arrow_forward
- 1. A 1000-W iron is left on the iron board with its base exposed to the air at 20°C. The convection heat transfer coefficient between the base surface and the surrounding air is 35 W/m². °C. If the base has an emissivity of 0.6 and a surface area of 0.02 m², determine the temperature of the base of the iron. 2. The inner and outer surfaces of a 5-m x 6-m brick wall of thickness 30 cm and thermal conductivity 0.69 W/m °C are maintained at temperatures of 20°C and 5°C, respectively. Determine the rate of heat transfer through the wall, in W.arrow_forwardConsider steady heat transfer between two large parallel plates at constant temperature of T1 = 500K and T2 =300K that are L =2 cm apart. Assuming the surfaces to be black ( emissivity Ɛ = 1 ), determine the rate of heat transfer between the plates per unit surface area assuming the gap between the plate filled with atmospheric air, (b) evacuated, (c) filled with fiberglass insulation, and (d) filled with superinsulation having an apparent thermal conductivity of 0.00015 W/m.˚C.arrow_forwardDetermine the heat transfer that occurs by radiation between two surfaces that are co-axial and parallel to each other, full and semicircular. Assume that the surfaces only exchange radiation with each other. T1 = 700 °C; ɛ1 = 0.8; T2 = 20 °C; e2 = 0.4. фб ст (2) to 4 cm 6 8 cm (1 t.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning