Answer / kangchuentat

ELECTRICAL TECHNOLOGY - ANSWER 16.3 : (a) Input = Output / Efficiency = 100 watts / 0.5 = 200 watts. (b) Number of inverter = Input / Rated power = 200 / 300 = 2 / 3 < 1. Practically only 1 inverter is needed. (c) I = Pin / V = 200 / 12 = 16.667 A. (d) Number of charge controllers = Input / Rated current = 16.667 / 10 = 1.6667 < 2. Practically only 2 are needed. (e) Energy consumption = 0.1 kilowatt x 2 hours / day = 0.2 kilowatt hour per day. (f) Input energy = Energy consumption / Efficiency = 0.2 / 0.5 = 0.4 kilowatt hour per day. (g) Energy generation per day per solar panel = 2.88 hours x 0.02 kilowatt = 0.0576 kilowatt hour. (h) Number of solar panels needed = Answer for (f) / Answer for (g) = 0.4 / 0.0576 = 6.944 < 7. Practically only 7 are needed. (i) Ampere hour per day to run the load = 0.4 kilowatt hour per day / 12 V = 1 / 30 k. Total ampere hour needed for 3 days = 1 / 30 k x 3 = 0.1 k. Number of batteries needed = 0.1 k / 5 = 100 / 5 = 20. The answer is given by Kang Chuen Tat; PO Box 6263, Dandenong, Victoria VIC 3175, Australia; SMS +61405421706; chuentat@hotmail.com; http://kangchuentat.wordpress.com.

Question 78 - Fact 1 : Dry air contains 20.95 % oxygen, 78.09 % nitrogen, 0.93 % argon, 0.039% carbon dioxide, and small amounts of other gases by volume. Fact 2 : Volume occupied is directly proportional to the number of moles for ideal gases at constant temperature and pressure. Fact 3 : 12.5 moles of pure oxygen is required to completely burn 1 mole of pure octane. Fact 4 : Air–fuel ratio (AFR) is the mass ratio of dry air to fuel present in a combustion process such as in an internal combustion engine or industrial furnace. Fact 5 : Molecular weight of oxygen gas is 31.998 g / mole and molecular weight of nitrogen gas is 28.014 g / mole. (a) Find the molar ratio of nitrogen and oxygen, or (moles of nitrogen) / (moles of oxygen) in dry air, by assuming ideal features of nitrogen and oxygen gases. (b) How many moles of nitrogen are available if dry air is used to completely burn the 1 mole pure octane? (c) Find the mass of fuel of 1 mole of octane with molecular weight of 114.232 g / mole. (d) Find the mass of dry air with 12.5 moles of pure oxygen by assuming only oxygen and nitrogen gases exist in the air. (e) Find the air-fuel ratio (AFR) when octane is used as fuel. (f) Find the fuel-air ratio (FAR) when octane is used as fuel.

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When should one be concerned with the tube wall temperature on the cooling waterside of a shell and tube exchanger?

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Question 106 - In a wavefunction, let P(x) = A cos kx + B sin kx. By using the boundary conditions of x = 0 and x = l, where P(0) = P(l) = 0, prove by mathematical calculation that P(x) = B sin (npx / l) where p = 22 / 7 approximately, n is a rounded number. A, B and k are constants.

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oil field interview question

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Explain the different types of equipments for the conveyance of solids?

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What types of valves are recommended for slurry services?

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What are the steps taken to operate a tank-blanketing valve?

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What are some good uses of low-grade steam at 12 atm and 1920c?

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How can you keep our seawater used for heat rejection clean before entering our heat exchangers?

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FOOD ENGINEERING - QUESTION 23.2 : (a) A dryer reduces the moisture content of 100 kg of a potato product from 80 % to 10 % moisture. Find the mass of the water removed in such drying process. (b) During the drying process, the air is cooled from 80 °C to 71 °C in passing through the dryer. If the latent heat of vaporization corresponding to a saturation temperature of 71 °C is 2331 kJ / kg for water, find the heat energy required to evaporate the water only. (c) Assume potato enters at 24 °C, which is also the ambient air temperature, and leaves at the same temperature as the exit air. The specific heat of potato is 3.43 kJ / (kg °C). Find the minimum heat energy required to raise the temperature of the potatoes. (d) 250 kg of steam at 70 kPa gauge is used to heat 49,800 cubic metre of air to 80 °C, and the air is cooled to 71 °C in passing through the dryer. If the latent heat of steam at 70 kPa gauge is 2283 kJ / kg, find the heat energy in steam. (e) Calculate the efficiency of the dryer based heat input and output, in drying air. Use the formula (Ti - To) / (Ti - Ta) where Ti is the inlet (high) air temperature into the dryer, To is the outlet air temperature from the dryer, and Ta is the ambient air temperature.

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Question 38 - The terminal velocity of a falling object, v is given by v = sqrt [ 4g (R - r) D / (3Cr) ] where sqrt is the square root of, g = 9.81, D = 0.000208, R = 1800, r = 994.6, m = 0.000893. The Reynold number, L is given by L = rD (v) / m. The C for various conditions are : C = 24 / L for L < 0.1; C = 24 (1 + 0.14 L^0.7) / L for 0.1 <= L <= 1000; C = 0.44 for 1000 < L <= 350000; C = 0.19 - 80000 / L for 350000 < L. Find the value of v for the situation above by trial and error, ^ is power, <= is less than or equal to.

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Define pcbs?

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