Concept explainers
A method for determining the thermal conductivity k and the specific heat
For a particular test run, the electrical heater dissipates 15.0 W fora period of
Determine the specific heat and thermal conductivity of the test material. By looking at values of the thermophysical properties in Table A.1 or A.2, identify the test sample material.
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Fundamentals of Heat and Mass Transfer
- 1.4 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_forwardA section of a composite wall with the dimensions shown below has uniform temperatures of 200C and 50C over the left and right surfaces, respectively. If the thermal conductivities of the wall materials are: kA=70W/mK,kB=60W/mK, kC=40W/mK, and kP=20W/mK, determine the rate of heat transfer through this section of the wall and the temperatures at the interfaces. Repeat Problem 1.34, including a contact resistance of 0.1 K/W at each of the interfaces.arrow_forward5.10 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_forward
- 1.3 A furnace wall is to be constructed of brick having standard dimensions of Two kinds of material are available. One has a maximum usable temperature of 1040°C and a thermal conductivity of 1.7 W/(m K), and the other has a maximum temperature limit of 870°C and a thermal conductivity of 0.85 W/(m K). The bricks have the same cost and are laid in any manner, but we wish to design the most economical wall for a furnace with a temperature of 1040°C on the hot side and 200°C on the cold side. If the maximum amount of heat transfer permissible is 950 , determine the most economical arrangement using the available bricks.arrow_forwardPlease provide accurate answer with proper steps The wall of the furnace is 30.48 mm thick and is insulated from outside. Thermal conductivity of the wall material is 0.1 W/m K and the insulation material is 0.01 W/m K. The furnace operates at 650 0C and the ambient temperature is 30 0 Allowable temperature on the outer side of the insulation is 1000C. Determine the overall heat transfer by conduction per unit area occurring across a furnace wall made from clay. If the air side heat transfer coefficient is 0.4 W/m2 K, calculate the minimum insulation thickness requirement.arrow_forwardPROBLEM 1: The block of 304 stainless steel shown below is well insulated on the front and back surfaces, and the temperature in the block varies linearly in both the x- and y-directions. Find: (a) The heat fluxes and heat flows in the x- and y-directions. (b) The magnitude and direction of the heat flux vector. 15°C 5°C 5 cm y 5 cm- 10 cm The thermal conductivity of 304 stainless steel is 14.4 W/m K. 10°C 0°Carrow_forward
- Question 5: Assume steady-state, one-dimensional heat conductionthrough the symmetric shape shown in Figure 1.Assuming that there is no internal heat generation, derivean expression for the thermal conductivity k(x) for theseconditions: A(x) = (1 -x), T(x) = 300(1 - 2x -x3),and q = 6000 W, where A is in square meters, T inkelvins, and x in meters. Consider x= 0 and 1arrow_forwardWhat is the analogical reason between heat transfer by conduction and flow of electricity through ohmic resistance? Use a composite wall of a building to illustrate the concept. A composite slab with three layers of thermal conductivities k1, k2, k3 and thickness ti, t2, të respectively, are placed in a close contact. Derive an expression from the first principle for the heat flow through the composite slab per unit surface area in terms of the overall temperature difference across the slab.arrow_forwardAfter a thorough derivation by Doraemon to establish an equation for cylindrical fuel rod of a nuclear reactor. Here he was able to come up an equation of heat generated internally as shown below. 9G = 9. where qG is the local rate of heat generation per unit volume at radius r, ro is the outside radius, and qo is the rate of heat generation per unit volume at the centre line. Calculate the temperature drop from the centre line to the surface for a 2.5 cm outer diameter rod having k = 25 W/m K, if the rate of heat removal from the surface is 1650 kW/m² А) 619°C В 719 °C C) 819 °C D) 919 °C E 1019 °C F None of thesearrow_forward
- 2. The lateral surface of a 50-units-long, thin vertical rod is insulated. When 0arrow_forward8. The shown 2-D plate is in contact with a heat source at its upper edge, which supplies heat at a constant flux, qo, per unit length. -- a. Derive a finite-difference relationship to express the steady-state temperature at the shown boundary point TP, in terms of the temperatures at the surrounding points (TE, Tw, Ts) and the other quantities in the problem (e.g., k, qo, etc.). Follow the methodology outlined in the class notes (i.e., use energy balance). Assume Ax = Ay. y 90 b. Modify the relationship for the case when the upper edge is perfectly insulated (without heat addition).arrow_forward6. A furnace wall consists of 250 mm fiber brick,125 mm insulating brick, and 250 mm building brick. The inside wall is at a temperature of 600°C and the atmospheric temperature is 20°C. Calculate the heat loss per m' of wall area and the temperature of the outside wall surface of the furnace and the temperature at each interface throughout the wall. The heat transfer coefficient for the outside surface is 10 W/m² °k and the thermal conductivities of the fiber brick, insulating brick and the building brick are 1.4,0.2 and 0.7 W/m.°C respectively.arrow_forwardarrow_back_iosSEE MORE QUESTIONSarrow_forward_ios
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning