Concept explainers
Consider the thick slab of copper in Example 5.12, which is initially at a uniform temperature of 20°C and is suddenly exposed to a net radiant flux of
(a) Calculate the 00 and 04 nodal temperatures at
(b) Plot temperature histories for
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Introduction to Heat Transfer
- A square silicon chip 7mm7mm in size and 0.5-mm thick is mounted on a plastic substrate as shown in the sketch below. The top surface of the chip is cooled by a synthetic liquid flowing over it. Electronic circuits on the bottom of the chip generate heat at a rate of 5 W that must be transferred through the chip. Estimate the steady-state temperature difference between the front and back surfaces of the chip. The thermal conductivity of silicon is 150 W/m K. Problem 1.6arrow_forward2.3 The shield of a nuclear reactor is idealized by a large 25-cm-thick flat plate having a thermal conductivity of . Radiation from the interior of the reactor penetrates the shield and there produces heat generation that decreases exponentially from a value of at the inner surface to a value of at a distance of 12.5 cm from the interior surface. If the exterior surface is kept at 38°C by forced convection, determine the temperature at the inner surface of the field. Hint: First set up the differential equation for a system in which the heat generation rate varies according to .arrow_forward1.4 To measure thermal conductivity, two similar 1-cm-thick specimens are placed in the apparatus shown in the accompanying sketch. Electric current is supplied to the guard heater, and a wattmeter shows that the power dissipation is 10 W. Thermocouples attached to the warmer and to the cooler surfaces show temperatures of 322 and 300 K, respectively. Calculate the thermal conductivity of the material at the mean temperature in W/m K. Problem 1.4arrow_forward
- 5.10 Experiments have been performed on the temperature distribution in a homogeneous long cylinder (0.1 m diameter, thermal conductivity of 0.2 W/m K) with uniform internal heat generation. By dimensional analysis, determine the relation between the steady-state temperature at the center of the cylinder , the diameter, the thermal conductivity, and the rate of heat generation. Take the temperature at the surface as your datum. What is the equation for the center temperature if the difference between center and surface temperature is when the heat generation is ?arrow_forward1.63 Liquid oxygen (LOX) for the space shuttle is stored at 90 K prior to launch in a spherical container 4 m in diameter. To reduce the loss of oxygen, the sphere is insulated with superinsulation developed at the U.S. National Institute of Standards and Technology's Cryogenic Division; the superinsulation has an effective thermal conductivity of 0.00012 W/m K. If the outside temperature is on the average and the LOX has a heat of vaporization of 213 J/g, calculate the thickness of insulation required to keep the LOX evaporation rate below 200 g/h.arrow_forwardA plane wall of thickness 8cm and thermal conductivity k=5W/mK experiences uniform volumetric heat generation, while convection heat transfer occurs at both of its surfaces (x= -L, x= + L), each of which is exposed to a fluid of temperature T∞ = 20˚C. The origin of the x-coordinate is at the midplane of the wall. Under steady-state conditions, the temperature distribution in the wall is of the form T(˚C) = a + bx - cx^2, where x is in meters, a =86˚C, b = -500˚C/m, and c=4459. 1) Heat Flux Entering the wall is ? 2) Temperature at the left face is /arrow_forward
- A solid cylinder of radius R and length L is made from material with thermal conductivity 2. Heat is generated inside the cylinder at a rate S (energy per unit volume per unit time). (a) Neglecting conduction along the axis of the cylinder, find the steady-state temperature distribution in the cylinder, given that the surface temperature is Ts. (b) Consider a crude approximation of a mouse modeled as a cylinder of radius 1 cm and length 5 cm. If the ambient air temperature is 10°C and the internal rate of heat generation in the animal is 10-³ W/cm³, find the skin temperature (Ts) for the mouse. The external heat-transfer coefficient is h = 0.2 W/m².K. (You can neglect conduction along the axis of the mouse, as in part a.)arrow_forward(a) Consider nodal configuration shown below. Derive the finite-difference equations under steady-state conditions for the following situations. (a) The boundary is insulated. (b) The boundary is subjected to a constant heat flux. m, n+1 Ay Im, n The side insulated m-1, n I I Ax- m, n-1arrow_forwardA solid circular rode of 40 cm long and 4 cm diameter is subjected to a uniform temperature at the circular surface of one of its ends of 100 °C. The surface of other end are subjected to free convection with surrounding air with a convection coefficient of h = 10 W/(m². °C) and air temperature of 30 °C. Lateral surface is insulated. Use three linear elements to find the temperature along the rod, and the energy entered at the end of constant temperature. The thermal conductivity of the rod is K= 60 W/(m. °C K)arrow_forward
- Steel pipe 3 cm thick, 1.0 m long and 10 cm deep, quiet with 6 cm thick insulation. The inner wall temperature of the steel pipe is 100 ° C. The ambient temperature around the integrated pipe is 24 ° C. The convection heat transfer coefficient outside the surface is 50 W / (m² K). The thermal conductivity of steel is 54 W / (m K), and the thermal conductivity of the insulation is 0.04 W / (m K). Count; A. Heat loss per meter of pipe = answer watt. b. Temperature between steel pipe and insulation. = Answer ° C.arrow_forward2. Consider the temperature distributions associated with a dx differential control volume within the one-dimensional plane walls shown below. T(x,00) T\x,00) * dx * dx (a) (Б) Tx,1) T(x,1) * dx dx (c) (d) (a) Steady-state conditions exist. Is thermal energy being generated within the differential control volume? If so, is the generation rate positive or negative? (b) Steady-state conditions exist as in part (a). Is the volumetric generation rate positive or negative within the differential control volume? (c) Steady-state conditions do not exist, and there is no volumetric thermal energy generation. Is the temperature of the material in the differential control volume increasing or decreasing with time? (d) Transient conditions exist as in part (c). Is the temperature increasing or decreasing with time?arrow_forwardTransient Heat Conduction Cooking a Thanksgiving turkey is an art form and, if your skills in the kitchen are like mine, it is sometimes more of a mystical, elusive art form. Thankfully, science also has much to contribute in the kitchen as well as the laboratory. Let us consider the change in temperature of a common, 20-lb holiday fowl as it is cooked in a convection oven. To simplify the analysis, let's assume the bird can be modeled as a uniform sphere of radius 7.0 in. with a specific heat of 3.53 kJ/kg-K. Moreover, the turkey will be assumed to have a uniform temperature, T, throughout that will change with time as it is cooked according to the following relationship: 。 + (To - T∞)ept T(t) = T∞ + where To is the initial temperature of the turkey, T∞, is the oven temperature, V is the volume of the turkey, As is the surface area of the turkey, and h is the convection coefficient for the scenario which is 11.3 W/m²-K. If the oven is set to 325 °F and the initial temperature of the…arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning