Problem 2: A stainless steel rod (k-21 W/m-K, p-8000 kg/m3, C,,-570 J/kg-K) with diameter D-10 mm is heat-treated as it...
Problem 2. A long 6.5 cm diameter solid cylinder steel (K 16.3 W/m. K,p 7817 kg/m3, Cp 460 J/kg.k). It's initially at a uniform temperature of T 150°C. It is suddenly exposed to a convection environment with h-285 W/m2 K and Too 50°C. Calculate the temperature at 1.) the axis of the cylinder, and 2.) a 2.5 cm radial distance after 5 min of exposure to the cooling flow. (20%)
A rod of diameter D = 25 mm and thermal conductivity of 60 W/m K protrudes from a furnace with a wall temperature of 200°C. The rod is welded to the furnace wall and is used as a hangar for instrumentation cables. To avoid damaging the cables, the surface temperature of last 100 mm of the rod must be kept below 100°C. The ambient air temperature is 25°C and the convection coefficient is 15 W/m2K. (a) Write the finite-difference equation for...
Problem 3 (50 points). A long stainless steel cylinder with diameter of d=55cm is heated up to 450°C. The cylinder is then cooled slowly in a chamber at 150°C with an average convection heat transfer coefficient of h = 70 W/m2.°C. (a) Find the temperature at the center of the cylinder after 25 min. (b) Find the heat transfer per unit length of the cylinder during this time period. Cylinder properties: k=15 W/m•°C, p=8000 kg/m², c=477 J/kg•°C, a=3.95x10-6 m²/s.
H8-1: An 8-m-internal-diameter spherical tank made of 1.5-cm-thick stainless steel (k-15 W/m K) is used to store iced water at 0°C. The tank is located in a room whose temperature is 25°C. The convection heat transfer coefficients at the inner and the outer surfaces of the tank are 80 W/m2 K and 10 W/m2 K, respectively. Radiatior heat transfer is negligible. Determine the rate of heat transfer to the iced water in the tank. room 25°0c T. Iced water 0...
A long steel bar with a diameter of 4 cm (ρ = 7840 kg / m3 , cp = 580 J / kg ° K, k = 52 W / mK, α = 1.21x10-5 m2 / s), internal enters the 2 m long moving belt heat treatment furnace at ambient temperature of 900 ° C at 40 ° C. Since the film coefficient in the oven is 100 W / m2K, the center axis temperature of the bar at the...
A long steel bar of radius R=2.5 cm, k =50 W/(m °C), p= 7800 kg/m), and c = 0.5 kJ/(kg. . °C) is to be annealed by cooling slowly from 800.°C to 100.°C in an environment at temperature 50.°C. If the heat transfer coefficient between the environment and the surface of the bars is h = 45 W/(m .°C), determine the time required for the annealing process using lumped system analysis.
A long cylinder of diameter D 0.012 m, thermal conductivity k 358 W/(mK), density p - 7614 kg/m3, specific heat c 418 J/(kgK) is initially at a uniform temperature of Ti-74°C. The cylinder is suddenly exposed to a gas at T,-18 ℃ The convection coefficient is h -17 W/(m2K). Verify that a lumped capacitance analysis can be used for the transient response of the cylinder temperature. What is the time t in seconds for the cylinder temperature to become Tf-32...
A long wire with circular cross section and diameter D = 1 mm is submerged in an oil bath with temperature To 20。C. The wire is initially at temperature T = 20。C, the same temperature as the oil. A current is passed through the wire, resulting in a volumetric heat generation of q - 1.5 x 108 W/m3. The convection coefficient is h - 500 W/m2 - K, and the properties of the wire are ρ-8000 kg/m3, Cp-500 J/kg-K, and...
Q2 (a) A 12 mm diameter mild steel sphere (k = 42.5 W/m K) is exposed to cooling airflow at 27 "C resulting in the convective coefficient, h = 114 W/m' K. The relevant properties of mild steel are given as follows: Density p= 7850 kg/m . Specific heat c = 475 J/kg K and thermal diffusivity a = 0.043 m/hr Determine: (i) Time required to cool the sphere (lumped parameter system) from 540 °C to 95°C. [7 marks] (ii)...
QUESTION TWO Carbon steel balls (p 7833 kg/m3, k-54 W/m K, cp 0.465 kJ/kg.0C and a-1.474 x 10-6 m2/s) 10 mm in diameter are annealed by heating them first to 900'C in a furnace and then allowing them to cool slowly to 100°C in ambient air at 35°C. If the average heat transfer coefficient is 75 W/m2 K, determine how long the annealing process will take. If 2500 balls are to be annealed per hour, determine the total rate of...