The strength and stability of tires may be enhanced by heating both sides of the rubber
(a) If steam flow over the tire surfaces maintains a convection coefficient of
(b) To accelerate the heating process, it is recommended that the steam flow be made sufficiently vigorous to maintain the tire surfaces at 200°C throughout the process. Compute and plot the midplane and surface temperatures for this case, as well as for the conditions of part (a).
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Introduction to Heat Transfer
- A gasoline engine is at a location where the temperature is measured to be 14.8 °C and produces 300 kW at 5800 rpm while consuming 0.0184 kg/s of fuel. During operation, data shows that its mechanical energy loss is 18 %, the actual volume of air going into each cylinder is 80% (the volumetric efficiency has a negligible variation), and the actual fuel-to-air ratio is 0.065. What were the engine parameters at sea level conditions if the pressure here is 99.3 kPa and the temperature here is 18 0C hotter than that of the elevated condition? Determine at sea-level conditions the Brake Power in kW.arrow_forwardA gas with R = 278.6 J/kg-K and cv = .736 kJ/kg-K expands from 14.972 atm and 561 K to9.524 atm. Assume that throughout the process, the system is insulated. For 0.454 kg/sof this gas, prove that:a. V2 = 0.06 m3/s;b. dS = 0; andc. - dH = 1810 kJ/min.arrow_forwardAn electric immersion heater is put into a sample of water of mass m. The water is heated from its initial temperature T; (approximately room temperature) to a final temperature T; (less than 100°C) while the heater itself maintains a constant temperature To. The specific heat of water, c, remains constant throughout the process, and any heat transfer to the container and the environment is negligible. a. Can the temperature of the heater be compared to the final temperature of the water? If not, why not? If so, is To greater than, less than, or equal to Tf? Explain. b. In terms of the given quantities (m, c, T;, Tf, To) determine expressions for the entropy change of the water and the heater. С. Determine whether this process is reversible by analyzing the sign of the entropy change for the heater-and-water system. d. Explain conceptually in terms of the 2nd law why your result about reversibility from part (c) is correct.arrow_forward
- Q5Two large containers A and B of the same size are filled with different fluids. The fluids in containers A and B are maintainedat 0° C and 100° C, respectively. A small metal bar, whose initial temperature is 100° C, is lowered into container A. After1 minute the temperature of the bar is 90° C. After 2 minutes the bar is removed and instantly transferred to the othercontainer. After 1 minute in container B, the temperature of the bar rises 10°. How long, measured from the start of theentire process, will it take the bar to reach 99.9° C?arrow_forwardStudents are casting an aluminum cylinder of diameter D = 2.5 cm and length of L = 10 cm from molten aluminum. The heated aluminum comes out of the mold at Ti = 530°C where it is quenched to T = 30°C by a cold-water faucet at T∞= 20°C and ℎ=1000 W/m2⋅K. Assume the thermophysical properties of aluminum are k = 230 W/m⋅K, ρ= 2710 kg/m3, and cp = 0.9 kJ/kg⋅K. First, determine whether the Lumped Capacitance Method is valid. Then, use the appropriate equation to determine how much time the aluminum cylinder must remain under the faucet to reach the desired temperature.arrow_forwardAn ice chest is constructed of Styrofoam [k = 0.033 W/m.°C] with inside dimensions of 25 by 40 by 100 cm. The wall thickness is 5.0 cm The outside of the chest is exposed to air at 25°C with N=10 W/m2°C. If the chest is completely filled with ice, calculate the time for the ice to completely melt. State your assumptions. The enthalpy of fusion for water is 330 kJ/kgarrow_forward
- Determine the MW and specific heat ratio of a gas whose Cv=1.386 kJ/kg.K and R= 0.485 kJ/Kg.K Provide the MW.arrow_forward2 (a) A short bronze cylinder of diameter 6 cm and length 12 cm is initially at 40°C and then plunged into a fluid at 200°C. The temperature at the centre of the cylinder is measured by a thermocouple to be 150°C after 5 minutes. What is the convective heat transfer coefficient between the cylinder and the fluid? The following properties of the bronze cylinder may be used: Thermal conductivity k = 26 W/m-K, density p = 8800 kg/m², and specific heat c = 420 J/kg-K. State and justify all assumptions made.arrow_forwardQI/The top surface of the passenger car of a train moving at a velocity of 70 km/h is 2.8 m wide and 8 m long. The top surface is absorbing solar radiation at a rate of 200 W/m2, and the temperature of the ambient air is 30°C. Assuming the roof of the car to be perfectly insulated and the radiation heat exchange with the surroundings to be small relative to convection, determine the equilibrium temperature of the top surface of the car. Ans =35.1 carrow_forward
- 1. A lead pipe has 2 cm inside diameter, 3 cm outer diameter, length of 130 cm. Liquid water at 4°C flows through the pipe with a bulk velocity of 2.50 km/hr. Air is blown around the outside of the pipe at 20 deg C. The inside wall of the said pipe has a temperature of 8 deg Celsius. Density of liquid water= 999.6509 kg/m³ Cp=4.218 kJ/kgK Viscosity of liquid water= 1.6193x10-3 Pa.s k (thermal conductivity of water) = 0.5742 W/mK Find: Overall heat coefficient (U) based on outside surface area b. Prandtl (Pr) and Reynolds (Re) numbers based on classification of flow а.arrow_forward1. A lead pipe has 2 cm inside diameter, 3 cm outer diameter, length of 130 cm. Liquid water at 4°C flows through the pipe with a bulk velocity of 2.50 km/hr. Air is blown around the outside of the pipe at 20 deg C. The inside wall of the said pipe has a temperature of 8 deg Celsius. Density of liquid water= 999.6506 kg/m³ Cp water=4.2184 kJ/kgK Viscosity of liquid water= 1.6202 x10-3 Pa.s k1 (thermal conductivity of water) = 0.5742 W/mK k2 (thermal conductivity of lead) = 34.92 W/mK Find: a. Overall heat coefficient (U) based on outside surface area b. Prandtl (Pr) and Reynolds (Re) numbers based on classification of flowarrow_forwardConsider two coffee cups A and B. Small coffee cup heaters are placed in cups A and B and heat is transferred to keep cup A at 45°C and cup B at 35°C. Room temperature is 25°C. The cups contain the same amount of water (100 grams). Which answer best describes the rates at which heat must be transferred to maintain the temperatures described above?: * A. Cup A will require heat at about five times the rate of B. B. Cup A will require heat at about twice the rate of B. C. Cup A will require heat at a slightly faster rate than B. D. Both cups will require heat at the same rate.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning