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The 150-mm-thick wall of a gas-fired furnace is constructed of fireclay brick
(a) How long does it take for the outer surface of the wall to reach a temperature of 750°C’?
(b) Plot the temperature distribution in the va1l at the foregoing lime, as well as at several intermediate times.
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Chapter 3 Solutions
Introduction to Heat Transfer
- Refrigerators make use of the heat absorption required to vaporize a volatile liquid. A fluorocarbon has a molar heat of vaporization of 26.0 kJ/mol at 250K and 750 torr. Calculate Q,W, ΔH and ΔU when 1 mole is vaporized at his temperature and pressure.arrow_forwarda tray of liquid water is placed in a freezer where it cools from 20 deg C to "-5" deg C. what is the total amount of energy needed to freeze per unit of liquid water? the specific heat of ice is half of the specific heat of liquid water. the latent heat of fusion for water is 335 kj/kg include diagramarrow_forwardA dead body was found within a closed room of a house where the temperature was a constant 24° C. At the time of discovery, the core temperature of the body was determined to be 28° C. One hour later, a second measurement showed that the core temperature of the body was 26° C. The core temperature of the body at the time of death is 37°C. A. Determine how many hours elapsed before the body was found. Answer: hours B. What is the temperature of the body 5 hours from the death of the victim? Answer: °Carrow_forward
- find the driving pressure for a stack that has a height of 18 m and carry a hot gas mixture with an average density of 1.2 k/m3. If you know that the total heat rejection by the stack is 1450 KJ and the c, of the hot gas is 1.8 KJ/Kg.K while the hot gas inlet and outlet temperature are 650 K and 500 K respectively. Assume the hot gas pressure as 2.3 bar while the ambient pressure is 1 bar.arrow_forwardIf a food product is being frozen in a system capable of removing 6200 kJ of thermal energy per product, with the product having a specific heat of 4.1 kJ/kg°C above the freezing temperature of -1.7°C , a latent heat of fusion of 284 kJ/kg, and the product has a specific heat of 2.2 kJ/kg°C below the freezing temperature. If 10.1 kg of product enters the system at 15°C, and exits it with a temperature of –12 °C, what percentage (to the nearest percent) of the full capability of the freezer has been used?arrow_forwardA dead body was found within a closed room of a house where the temperature was a constant 70°F. At the time of discovery, the core temperature of the body was determined to be 85°F. One hour later a second measurement showed that the core temperature of the body was 80°F. Assume that the time of death corresponds t = 0 and that the core temperature at that time was 98.6°F. Determine how many hours elapsed before the body was found. (Round your answer to one decimal place.) hrarrow_forward
- A piece of chromium steel of length 7.4 cm (density = 8780 kg/m³, K = 50 W/m.K, and Cp = 200 j/kg.K) with mass 1.27 kg, is rolled into a solid cylinder with the same length and heated to a temperature of 600 C and quenched in oi at 36 C. You may take the convective heat rate coefficient between the oil and the cylinder at 280 W/m².K. a) Show that the lumped capacitance system analysis is applicable by calculating the Bi Number b) Find the temperature of the cylinder after 4 min. c) Find the total energy loss during this period. The temperature of the cylinder after 4 min is: The Bi Number is: The total energy loss during this 4 min period is: Choose Choose Choosearrow_forwardA welding heat source is capable of transferring 160 kJ/min to the surface of a metal part. The heated area is approximately circular, and the heat intensity decreases with increasing radius as follows: 50% of the power is transferred within a circle of diameter = 0.25 cm and 75% is transferred within a concentric circle of diameter = 0.625 cm. What are the power densities in (a) the 0.25 cm diameter inner circle and (b) the 0.625 cm diameter ring that lies around the inner circle? (c) Are these power densities sufficient for melting metal?arrow_forwardA solar radiant heat flux of 700 W/m2 is absorbed in a metal plate that is perfectly insulated on the back side. The convection heat- transfer coefficient on the plate is 11 W/m2 • C, and the ambient air temperature is 30 -C. Calculate the temperature of the plate in deg F under equilibrium conditions.arrow_forward
- Assume that there is an isolated system which has 2 compartments that are separated by a wall that is adiabatic, impermeable, and movable. The said system contains an ideal gas. One compartment has NO-0.75 gas moles and is initially held at 200K. Then, the other compartment has N2)-0.5 gas moles and is initially held at 300K. Moreover, the initial pressures are P(1)-p(2)-2 atm. Find the final volume of each compartment at equilibrium.arrow_forwardSteam at 100°C is used to warm 350 g of water contained in a 300 g aluminum container. The initial temperature of the water and aluminum is 20°C and after the steam is added, the equilibrium temperature is 50°C. What mass of steam will be required to accomplish this?Specific Heat of steam = 2010 J/kg- oCSpecific Heat of water = 4186 J/kg- oCSpecific Heat of aluminum = 900 J/kg- oCLatent Heat of Fusion of ice = 3.33 x 10 5 J/kgLatent Heat of Vaporization of water = 2.26 x 10 6 J/kgarrow_forwardTwo insulated cylinders A and B with volumes VA = 1.2 m³ and VB = 6.4 m³ contain chlorine gas at different pressures and temperatures. The cylinders are insulated (no heat is lost to or gained from the outside) and connected by a valve. Initially, the valve is closed and the gas in the two cylinders has the following values: PA= 4.0 x 105 N/m2, TA= 250 K, PB = 2.5 x 105 N/m², Tg = 580 K. The valve is opened to allow the contents in the two cylinders to mix until the pressure equalizes. valve K TEACHER (a) Assuming there is no change in the temperatures of the containers themselves, determine the final temperature of the gas in the two cylinders. The atomic mass of chlorine gas is 35.4527 U. (b) Determine the final pressure. N/m²arrow_forward
- Refrigeration and Air Conditioning Technology (Mi...Mechanical EngineeringISBN:9781305578296Author:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill JohnsonPublisher:Cengage Learning
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