Homework Answers
Add Answer to:
On a clear night the air temperature is observed to remain at about 4 °C Yet...
11 We often see frost on a windshield of car at a clear cold night. A...
11 We often see frost on a windshield of car at a clear cold night. A thin layer of water formed from moist ar dew point) on a windshield of a car in a parking lot is exposed to a clear sky at -17°C. The ambient air temperature and convection coefficient are 5°C and 10 W/m2.K. Assume that the emissivity of the thin layer of water is 0.9. Explain how frost can be formed even the ambient air temperature of...
7. Frost forms on a grapefruit when the temperature of its surface reaches 0°c At night, the grap...
7. Frost forms on a grapefruit when the temperature of its surface reaches 0°c At night, the grapefruit is assumed to be completely surrounded by the night sky acting as a black body at -45°C. The emissivity of the grapefruit is approximately 0.93 while the heat transfer coefficient between the grapefruit and the air surrounding it is 17 W/m°C. The grapefruit may be assumed to be at steady state without internal heat generation and energy conduction up the stem may...
A household oven door of 0.6-m height and 0.7-m width reaches an average surface temperature of...
A household oven door of 0.6-m height and 0.7-m width reaches an average surface temperature of 32°C during operation. The temperature of ambient air is 22°C. Assuming the door has an emissivity of 0.8 and the surroundings are also at 22°C, determine the heat transfer by free convection and the heat transfer by radiation. 1) What is the volumetric thermal expansion coefficient of air at the film temperature outside the oven door, in 1/K? 2) What is the Rayleigh number...
During its manufacture, plate glass at 600°C is cooled by passing air over its surface such...
During its manufacture, plate glass at 600°C is cooled by passing air over its surface such that the convection heat transfer coefficient is h. To prevent cracking, it is known that the temperature gradient must not exceed 15 °C/mm at any point in the glass during the cooling process. The thermal conductivity of the glass is 1.4 W/mK and its surface emissivity is 0.75. The temperature of the air that is used for the cooling is 315 °C. Assume that...
The wall of a house is 3 m high, 10 m long and 30 cm thick;...
The wall of a house is 3 m high, 10 m long and 30 cm thick; it has an effective thermal conductivity of 10 W/m K. The outer surface of the wall has an emissivity of 0.75. On a winter night, the outer surface of this wall is at a temperature of 0 °C and the air is at a temperature of –10 °C. The heat transfer coefficient for the outside wall is 8 W/m2 K. The outside wall also...
Homework 7 heat transfer 2018-20 1) A horizontal tube of 12.5-mm dimeter with an outer srface temperature of 240°C is placed in a room with an air temperature of 20°C. Estimate the heat transfer rate...
Homework 7 heat transfer 2018-20 1) A horizontal tube of 12.5-mm dimeter with an outer srface temperature of 240°C is placed in a room with an air temperature of 20°C. Estimate the heat transfer rate per unit length of the tube due to free convection. 2) Air at -10°C flows at 10 m/s over the roof plate of two 5m length rooms whose air is at Too-200C. The roof plate is 0.20-m thick concrete (k = 0.6 w/ m. K)....
“A pipe is carrying hot water through a cold storage facility. The ambient air in the...
“A pipe is carrying hot water through a cold storage facility. The ambient air in the cold storage has temperature of ?5?C. To maintain uniform temperature in the cold storage, blowers installed in the facility induce a 3 m/s velocity to the cold air (which can be assumed to be flowing across the water pipe). Hot water inside the pipe has a mean velocity of 0.5 m/s. The internal and exter- nal diameter of the pipe are 8.4 cm and...
Cold conditioned air at 10°C is flowing inside a 1.5 cm thick square aluminum (k = 240 w/mK) duct...
Cold conditioned air at 10°C is flowing inside a 1.5 cm thick square aluminum (k = 240 w/mK) duct of inner cross section of 25x25cm at a mass flow rate of 1.0 kg/s. The duct is exposed to air at 35°C with a combined convection-radiation heat transfer coefficient of 15 W/m2K. The convection heat transfer coefficient at the inner surface is 75 W/.m2.K. If the air temperature in the duct should not increase by more than 1°C determine the maximum...
1. Consider an opaque, horizontal square plate (Im by 1m) with an electrical heater on its backside. The front side is exposed to ambient quiescent air that is at 20° C, solar irradiation (from...
1. Consider an opaque, horizontal square plate (Im by 1m) with an electrical heater on its backside. The front side is exposed to ambient quiescent air that is at 20° C, solar irradiation (from sun at 5800° K) of 600 W/m2, and an effective sky temperature of -40° C. The plate surface temperature is kept at Ts 60 C (at steady state condition). Calculate natural convection heat transfer coefficient from the plate. (10 points) What is the electrical power (W/m2)...
When the air temperature is below 0 C, the water at the surface of a lake...
When the air temperature is below 0 C, the water at the surface of a lake freezes to form an ice sheet. The longer the air remains at this temperature, the thicker the ice sheet will become. Will a lake in Minnesota that is uniformly 40 m deep ever freeze solid? To answer this, calculate how long it would take to freeze all the water in the lake. Assume that the upper surface of the ice sheet is steady at...
11 We often see frost on a windshield of car at a clear cold night. A thin layer of water formed from moist ar dew point) on a windshield of a car in a parking lot is exposed to a clear sky at -17°C. The ambient air temperature and convection coefficient are 5°C and 10 W/m2.K. Assume that the emissivity of the thin layer of water is 0.9. Explain how frost can be formed even the ambient air temperature of...
7. Frost forms on a grapefruit when the temperature of its surface reaches 0°c At night, the grapefruit is assumed to be completely surrounded by the night sky acting as a black body at -45°C. The emissivity of the grapefruit is approximately 0.93 while the heat transfer coefficient between the grapefruit and the air surrounding it is 17 W/m°C. The grapefruit may be assumed to be at steady state without internal heat generation and energy conduction up the stem may...
During its manufacture, plate glass at 600°C is cooled by passing air over its surface such that the convection heat transfer coefficient is h. To prevent cracking, it is known that the temperature gradient must not exceed 15 °C/mm at any point in the glass during the cooling process. The thermal conductivity of the glass is 1.4 W/mK and its surface emissivity is 0.75. The temperature of the air that is used for the cooling is 315 °C. Assume that...
Homework 7 heat transfer 2018-20 1) A horizontal tube of 12.5-mm dimeter with an outer srface temperature of 240°C is placed in a room with an air temperature of 20°C. Estimate the heat transfer rate per unit length of the tube due to free convection. 2) Air at -10°C flows at 10 m/s over the roof plate of two 5m length rooms whose air is at Too-200C. The roof plate is 0.20-m thick concrete (k = 0.6 w/ m. K)....
Cold conditioned air at 10°C is flowing inside a 1.5 cm thick square aluminum (k = 240 w/mK) duct of inner cross section of 25x25cm at a mass flow rate of 1.0 kg/s. The duct is exposed to air at 35°C with a combined convection-radiation heat transfer coefficient of 15 W/m2K. The convection heat transfer coefficient at the inner surface is 75 W/.m2.K. If the air temperature in the duct should not increase by more than 1°C determine the maximum...
1. Consider an opaque, horizontal square plate (Im by 1m) with an electrical heater on its backside. The front side is exposed to ambient quiescent air that is at 20° C, solar irradiation (from sun at 5800° K) of 600 W/m2, and an effective sky temperature of -40° C. The plate surface temperature is kept at Ts 60 C (at steady state condition). Calculate natural convection heat transfer coefficient from the plate. (10 points) What is the electrical power (W/m2)...
Most questions answered within 3 hours.
-
A student takes a multiple-choice test that has 10 questions.
Each question has two choices. The...
asked 16 minutes ago -
Willie Keeler has a lifetime batting average of 0.341. Assume
that Willie Keeler came to bat...
asked 18 minutes ago -
Which of the following has the highest boiling point?
A) 0.5m NaCl
B) 0.5m C6H12O6
C)...
asked 37 minutes ago -
12. A firm is producing at an output level where
AR = MC > AC >...
asked 34 minutes ago -
Radovilsky Manufacturing Company, in Hayward, California,
makes flashing lights for toys. The company operates its production...
asked 36 minutes ago -
As an athlete exercises, sweat is produced and evaporated to
jelp maintain a proper body temperature....
asked 36 minutes ago -
Which of these macromolecules is most prevalent (by mass) in the
environment? What particular challenge does...
asked 38 minutes ago -
Consider two stocks. Stock A has a standard deviation of 46% and
stock B has a...
asked 41 minutes ago -
Give a unary language (using only input alphabet ∑={1} )that is
not Turing- recognizable and prove...
asked 52 minutes ago -
1. Write the balanced net reaction for a Ti (s) | TiCl2 (aq) ||
InCl3 (aq)...
asked 50 minutes ago -
3) Answer the following questions:please respond in one
paragraph
In your opinion, what are the crucial...
asked 56 minutes ago -
Assume that the readings at freezing on a batch of thermometers
are normally distributed with a...
asked 1 hour ago