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9. (7 pts) A pack with a total internal resistance of 0.5 ohm experiences a constant...
8. A battery pack with a total internal resistance of 1 ohm delivers 100 amps under...
8. A battery pack with a total internal resistance of 1 ohm delivers 100 amps under steady state conditions. The pack is cooled with water. a. (3 pts) Estimate the mass flow rate of water required to keep the water temperature change from inlet to exit within 5°C. b. (3 pts) The cooling flow arrangement results in an average convection coefficient of 200 W/m2K. Estimate the temperature of a cell close to the water exit, where the water temperature is...
An electric car travels at a constant highway speed of 60 mph, requiring a battery current...
An electric car travels at a constant highway speed of 60 mph, requiring a battery current draw of 50 A. The cooling system operates such that the average convection coefficient, h, is 25 W/m2 K. The coolant average temperature is 23°C. Suddenly a cooling system malfunction results in a decrease of the convection coefficient to 5 W/m2K. The pack has a heat transfer surface area of 1.2m2 and a mass of 50 kg. The pack specific heat is 600J/kg K...
ans: (a) 25 (b) 267 (c) 314.7 (d) 2.12 9 )A thermal storage battery consists of...
ans:
(a) 25
(b) 267
(c) 314.7
(d) 2.12
9 )A thermal storage battery consists of 10 kg of a salt solution that changes phase at 80°C and has the following properties: solid to liquid latent heat 80 W-hr/kg liquid 900 J/kg-K 350 J/kg-K specific heat as specific heat as solid = The battery container is superinsulated with a heat loss rate of 3 W (assume constant). En- gine coolant flows through the battery at a rate of 0.09 kg/sec,...
7. (20 pts) A sphere with 30 mm in diameter initially at 800 K is quenched...
7. (20 pts) A sphere with 30 mm in diameter initially at 800 K is quenched in a large bath having a constant temperature of 320 K with a convection heat transfer of 75 W/m2.K. The thermophysical properties of the sphere material are: p=400 kg/mº, c=1600 J/kg-K, and k=1.7 W/mK. (Use characteristic length Lc=VIA to determine applicability of lumped method; Use radius of the sphere for one term approximation) a) Calculate the time required for the surface of the sphere...
A bare copper cable 2.5 cm in diameter is situated in still air at 15°C. A...
A bare copper cable 2.5 cm in diameter is situated in still air at 15°C. A current of 800 Amps is passed along the cable. Heat is transferred from the cable to its surroundings by natural convection for which the heat transfer coefficient may be expressed as 2.95025 W/m2 K. Determine whether or not it may be assumed that the temperature across the copper cross section is uniform and what the equilibrium temperature of the cable surface will be. If...
3. (40pts) | In the thermal system shown in Figure 7-28(a), it is assumed that the tank is insula...
3. (40pts) | In the thermal system shown in Figure 7-28(a), it is assumed that the tank is insulated to eliminate heat loss to the surrounding air, that there is no heat storage in the insula tion, and that the liquid in the tank is perfectly mixed so that it is at a uniform temper ature. (Thus, a single temperature can be used to denote both the temperature of the liquid in the tank and that of the outflowing liquid.)...
CHAPTER 9 REVIEW QUESTIONS 1. How much heat is required to raise the temperature of a...
CHAPTER 9 REVIEW QUESTIONS 1. How much heat is required to raise the temperature of a 0.04 kg stainless steel spoon from 20°C to 50°C if the specific heat of stainless steel is 0.50 kJ/kg-C? (A) 200 (B) 400 (C) 600 (D) 800) (E) 2000 5. An ideal gas is confined to a container whose volume is fixed. If the container holds n moles of gas, by what factor will the pressure increase if the absolute temperature is increased by...
CHAPTER 9 REVIEW QUESTIONS 1. How much heat is required to raise the temperature of a...
CHAPTER 9 REVIEW QUESTIONS 1. How much heat is required to raise the temperature of a 0.04 kg stainless steel spoon from 20°C to 50°C if the specific heat of stainless steel is 0.50 kJ/kg-C? (A) 200 (B) 400 (C) 600 (D) 800) (E) 1000 5. An ideal gas is confined to a container whose volume is fixed. If the container holds n moles of gas, by what factor will the pressure increase if the absolute temperature is increased by...
Chose the correct answer(s) from the multiple choice lists below 1. Exergy of a system is a) b) always increasing e) guided by the first and second laws of thermodynamics for reversible proce...
Chose the correct answer(s) from the multiple choice lists below 1. Exergy of a system is a) b) always increasing e) guided by the first and second laws of thermodynamics for reversible processes only Un d) limited by the second law of thermodynamics for all processes. processes, it is destroyed partly or completely). e) equal to the Gibs free energy of the system. 211two electrodes, one made of u (E.-3.06 V) and another made of Cu ΟΕ.+034V placed in an...
Chapter overview 1. Reasons for international trade Resources reasons Economic reasons Other reasons 2. Difference between...
Chapter overview 1. Reasons for international trade Resources reasons Economic reasons Other reasons 2. Difference between international trade and domestic trade More complex context More difficult and risky Higher management skills required 3. Basic concept s relating to international trade Visible trade & invisible trade Favorable trade & unfavorable trade General trade system & special trade system Volume of international trade & quantum of international trade Commodity composition of international trade Geographical composition of international trade Degree / ratio of...
8. A battery pack with a total internal resistance of 1 ohm delivers 100 amps under steady state conditions. The pack is cooled with water. a. (3 pts) Estimate the mass flow rate of water required to keep the water temperature change from inlet to exit within 5°C. b. (3 pts) The cooling flow arrangement results in an average convection coefficient of 200 W/m2K. Estimate the temperature of a cell close to the water exit, where the water temperature is...
ans:
(a) 25
(b) 267
(c) 314.7
(d) 2.12
9 )A thermal storage battery consists of 10 kg of a salt solution that changes phase at 80°C and has the following properties: solid to liquid latent heat 80 W-hr/kg liquid 900 J/kg-K 350 J/kg-K specific heat as specific heat as solid = The battery container is superinsulated with a heat loss rate of 3 W (assume constant). En- gine coolant flows through the battery at a rate of 0.09 kg/sec,...
7. (20 pts) A sphere with 30 mm in diameter initially at 800 K is quenched in a large bath having a constant temperature of 320 K with a convection heat transfer of 75 W/m2.K. The thermophysical properties of the sphere material are: p=400 kg/mº, c=1600 J/kg-K, and k=1.7 W/mK. (Use characteristic length Lc=VIA to determine applicability of lumped method; Use radius of the sphere for one term approximation) a) Calculate the time required for the surface of the sphere...
A bare copper cable 2.5 cm in diameter is situated in still air at 15°C. A current of 800 Amps is passed along the cable. Heat is transferred from the cable to its surroundings by natural convection for which the heat transfer coefficient may be expressed as 2.95025 W/m2 K. Determine whether or not it may be assumed that the temperature across the copper cross section is uniform and what the equilibrium temperature of the cable surface will be. If...
3. (40pts) | In the thermal system shown in Figure 7-28(a), it is assumed that the tank is insulated to eliminate heat loss to the surrounding air, that there is no heat storage in the insula tion, and that the liquid in the tank is perfectly mixed so that it is at a uniform temper ature. (Thus, a single temperature can be used to denote both the temperature of the liquid in the tank and that of the outflowing liquid.)...
CHAPTER 9 REVIEW QUESTIONS 1. How much heat is required to raise the temperature of a 0.04 kg stainless steel spoon from 20°C to 50°C if the specific heat of stainless steel is 0.50 kJ/kg-C? (A) 200 (B) 400 (C) 600 (D) 800) (E) 2000 5. An ideal gas is confined to a container whose volume is fixed. If the container holds n moles of gas, by what factor will the pressure increase if the absolute temperature is increased by...
CHAPTER 9 REVIEW QUESTIONS 1. How much heat is required to raise the temperature of a 0.04 kg stainless steel spoon from 20°C to 50°C if the specific heat of stainless steel is 0.50 kJ/kg-C? (A) 200 (B) 400 (C) 600 (D) 800) (E) 1000 5. An ideal gas is confined to a container whose volume is fixed. If the container holds n moles of gas, by what factor will the pressure increase if the absolute temperature is increased by...
Chose the correct answer(s) from the multiple choice lists below 1. Exergy of a system is a) b) always increasing e) guided by the first and second laws of thermodynamics for reversible processes only Un d) limited by the second law of thermodynamics for all processes. processes, it is destroyed partly or completely). e) equal to the Gibs free energy of the system. 211two electrodes, one made of u (E.-3.06 V) and another made of Cu ΟΕ.+034V placed in an...
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