A pipe of outside diameter 200 mm is lagged with an insulating material
of thermal conductivity 0.06 W m–1 K–1 and thickness 75 mm. The pipe
carries a process fluid at a temperature of 300 °C and the average
temperature of the outer surface of the lagging is 45 °C.
(a) Estimate the rate of heat loss per metre length of pipe.
(b) Explain why the thermal resistance of the pipe wall can be ignored.
4. A pipe carrying superheated steam at 300 °C has an outside diameter of
120 mm and is lagged with two layers of insulating material. The first
layer (adjacent to the outer pipe wall) is 25 mm thick and has a thermal
conductivity of 0.072 W m–1 K–1. The second layer (covering the first
layer) is 20 mm thick, has a thermal conductivity of 0.051 W m–1 K–1 and
an outside temperature of 28 °C.
Estimate the rate of heat loss per metre length of pipe (assume the thermal
resistance of the pipe wall is negligible).
In: Other
Suppose you want to invest in a mining operation. You know the total mass of four ore deposits, the percent of that deposit that is a mineral containing iron (Fe), and the chemical formula for the mineral:
Deposit A contains 31,000,000 tons of ore containing 26% sidererite [FeCO3]
Knowing this information, you can determine the amount of the desired element (Fe) in the deposit. I have calculated the amount of Fe in Deposit A as an example. (Hint: You will need to obtain some information from the periodic table of elements (Links to an external site.) and do several calculations.)
Deposit A contains 31,000,000 tons of ore containing 26% sidererite [FeCO3]
Therefore, Deposit A contains 3,883,834 tons of Fe.
Questions 1 – 3: For deposits B, C, and D, calculate the amount of Iron in the deposit. *Note: when completing your calculations, remember that there is a different % of Fe in each of the different minerals!
Question 4: Which of the 4 hypothetical ore deposits (A, B, C, or D) above contains the most iron by weight, and therefore is worth the most money? For this simple example, assume that all other costs are equal.
Question 5: Next, think about some of the other probable costs associated with a mining operation. Consider all of the steps involved (from discovering the deposit to bringing it to market), all of which must be considered before going into business if you want to make a profit. List as many as you can think of. (Note: Some should be related directly to mining and geology, but others will not.)
Question 6: Finally, consider all of the waste involved in the process of obtaining minerals – both in removing the ore from the ground, and (for at least some materials) in separating the desired element or compound from the rest of the material. What do you think (or know) is done with all of this waste material?
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Reflection of the short film "How Wolves Change Rivers" and Aldo Leopold's "Thinking Like A Mountain".
In: Other
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An air conditioning unit, where water condensation is allowed, cools 9,791 m3 / min of humid air from 40 ° C and 50% relative humidity to 15 ° C. The total pressure is 1 atm. Calculate the heat removed in the cooling, answer in kW.
In: Other
Q1. Study the effect of hydrogen as a chain transfer agent on the ethylene and propylene polymerization.
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What does the IPAT formula tell us about the causes of environmental degradation? Why does the author believe that this formula is only partially accurate? What factors need to be added to improve it? Explain...
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a.Describe (or draw) the three basic patterns of water levels for each of the three tidal patterns (diurnal, semidiurnal and mixed) over a 24-hour period. Label your axes! (1 point each; 3 points total).
b.How will these patterns change during a New/Full moon and what are these types of tides called (1 point)?
c.How will these patterns change during a first/third-quarter moon and what are these types of tides called (1 point)?
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Devise a Carnot Heat Pump using steady flow components and describe how the Carnot cycle is executed in that device. Elaborately explain.
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Let's say an average cow emits 100kg of methane per annum.
If coal consists of 80% carbon and 20% moisture and ash, how much
coal would I have to burn per annum to have the same global warming
potential as one cow.
Assume that the carbon in the coal burns completely.
In: Other
5A. Which of the following is true?
A
The thermohaline circulation is partly due to the salinity differences of water.
B
The longer the river, the larger the drainage area.
C
The surface water is much more widely distributed than underground water.
D
None of the above is true.
5B. Plants need moisture to survive. The availability of moisture depends on many factors. Which of the following is true?
A
The more evaporation, the more moisture is available to the plants.
B
The more transpiration, the more moisture is available to the plants.
C
None of the above is true.
5C. The spatial distribution patterns of _ is closely related to _.
A
climate, vegetation
B
fur-bearing animals, climate
C
soil, climate
D
wildfire, soil
5D. Which of the following is true?
A
Winds always have positive effect on life.
B
Wildfires always have negative effect on life.
C
Winds and wildfires always have negative effect on life.
D
None of the above is true.
In: Other
HEAT TRANSFER: HEAT EXCHANGER
Oil flows in a heat exchanger with a mass flow rate of 20 kg/s and is to be cooled from 175 to 65°C with water as a coolant flowing at a rate of 30 kg/s and an inlet temperature of 12°C. The overall heat transfer coefficient is U = 1250 W/m2⋅K.
a) Sketch the temperature profile and calculate the mean temperature for parallel flow, counter flow, and cross flow heat exchangers..
b) Determine the area required to sustain the heat transfer for each heat exchanger stated in (a) Comment on your answer.
c) If fouling with thickness of 2 mm happens on the tubes side, determine the new heat transfer coefficient and evaluate the effectiveness of a 45 m length counter flow heat exchanger before and after fouling. Specific heat capacity of oil and water is given as cp, oil = 2058 J/kg⋅K and cp, water = 4184 J/kg⋅K. Conductivity of fouling is taken as kf,I = 11 W/m⋅K.
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A 12-cm tall, 6-cm outer diameter cylindrical ceramic mug filled with tea is boiling in a microwave oven. Assume latent heat of evaporation as 2260 kJ/kg. The convection heat transfer coefficient is h=20 W/(m 2 K) and the air in the microwave is at 20 °C. The mug’s wall thickness is 6 mm and the ceramic thermal conductivity is 30 W/(mK). Neglect heat transfer from the bottom of the mug and calculate the rate (in g/s) at which the tea is boiling if the microwave power absorbed by the tea is 50 W.
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