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The 5-mm-thick bottom of a 200-mm-diameter pan may be made from aluminum
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Introduction to Heat Transfer
- Max likes to drink tea. He uses his kettle to heat 1.6 liters of water from 18°C to 100°C every day. What does it cost him to heat the water per year (365 days) if he pays 29 cents per kWh of electricity. State the costs in euros to two decimal places. The material values of water averaged for the swept temperature range are: Cwater=4.18 kJ/(kg-K); pwater=983 kg/m3; Awater=0.654 W/(m2. K); nwater=467-10-6 kg/(m-s).arrow_forwardShow step-by-step solution and schematic diagram if possible. Thank you.arrow_forward5. A pipe with an outside diameter of 2.5 inches is insulated with 2 inches layer of asbestos (k = 0.396 Btu- in/hr-ft²-°F), followed by a layer of cork 1.5 inches thick (k = 0.30 Btu-in/hr-ft²-°F). If the temperature at the inner surface of the pipe is 290°F and at the outer surface of the cork is 90°F, calculate the heat loss per 100 ft of insulated pipe. (Btu/hr)arrow_forward
- The heat loss per hour through 1 sq. ft of furnace wall 18" thick is 520 Btu. The temperature on the hot side of the wall is 1900 degrees F, and its average thermal conductivity is 0.61 Btu/hr-ft-°F. Determine the temperature on the other side of the wall in °C.arrow_forward= Consider a large plane wall of thickness L=0.3 m, thermal conductivity k = 2.5 W/m.K, and surface area A = 12 m². The left side of the wall at x=0 is subjected to a net heat flux of ɖo = 700 W/m² while the temperature at that surface is measured to be T₁ = 80°C. Assuming constant thermal conductivity and no heat generation in the wall, (a) express the differential equation and the boundary equations for steady one- dimensional heat conduction through the wall, (b) obtain a relation for the variation of the temperature in the wall by solving the differential equation, and (c) evaluate the temperature of the right surface of the wall at x=L. Ti до L Xarrow_forwardA furnace wall is to be designed to transmit a maximum heat flux of 220 Btu/hr.ft of wall area. The inside and outside wall temperatures are to be 2200 • F and 320 ° F. Determine the most economical arrangement of bricks measuring (9 in x 4; in x 3 in). If they are made from materials one with ak of 0.44 Btu/hr. ft. ° F and maximum usable temperature of 1700 ° F and other with a k of 0.94 Btu/hr. ft. ° F and a maximum usable temperature of 2400 ° F. Bricks made of each material cost the same amount and may be laid in any manner (but bricks must remain intact, i.e., no partial bricks). After you answer the question, determine the percent increase in heat flux if there are two -in.-diameter steel bolts extending through the wall per square foot of wall are. (k of steel = 22 Btu/hr. ft. F)|arrow_forward
- Example 10: Consider a long resistance wire of radius r1 = 0.2 cm and thermal conductivity kwire = 15 W/m·°C in which heat is generated uniformly as a result of resistance heating at a constant rate of g = 50 W/cm3. The wire is embedded in a 0.5-cm-thick layer of ceramic whose thermal conductivity is kceramic = 1.2 W/m·°C. If the outer surface temperature of the ceramic layer is measured to be Ts = 45°C, determine the temperatures at the center of the resistance wire and the interface of the wire and the ceramic layer under steady conditions.arrow_forward6. a. The heat flux applied to the walls of the biomass combustion furnace is 20 W/m2. The furnace walls have a thickness of 10 mm and a thermal conductivity of 12 W/m.K. If the wall surface temperature is measured to be 50oC on the left and 30oC on the right, prove that conduction heat transfer occurs at a steady state!b. Heating the iron cylinder on the bottom side is done by placing the iron on the hotplate. This iron has a length of 20 cm. The surface temperature of the hotplate is set at 300oC while the top side of the iron is in contact with the still outside air. To reach the desired hotplate temperature, it takes 5 minutes. Then it takes 15 minutes to measure the temperature of the upper side of the iron cylinder at 300oC. Show 3 proofs that heat transfer occurs transientlyarrow_forwardSuppose that as a body cools, the temperature of the surrounding medium increases because it completely absorbs the heat being lost by the body. Let T(t) and Tm (t) be the temperatures of the body and the medium at time t, respectively. If the initial temperature of the body is T1 and the initial temperature of the medium is T2, then it can be shown in this case that Newton's law of cooling is dT/dt = k(T - Tm ), k 0 is a constant. (a) The foregoing DE is autonomous. Determine the limiting value of the temperature T(t) as t→ o What is the limiting value of Tm (t) as t→o? (b) Verify your answers in part (a) by actually solving the differential equation. (c) Discuss a physical interpretation of your answers in part (a).arrow_forward
- An electric heater producing 260 W of heat is used to warm up a room containing 7 m3 of air. If we assume the room is perfectly sealed and there is no heat loss through the room boundaries, such that all of the heater output goes into increasing the air temperature, how long will it take to heat up the air in the room from 5.0 °C to 24.1 °C? Give your answer to the nearest minute and assume that the specific volume (v = 0.85 m3/kg) and specific heat capacity at constant volume (cv = 1.005 kJ/(kg K)) remain constant throughout the heating process.arrow_forwardWater is being heated in a closed pan on top of a range while being stirred by a paddle wheel. During the process, 40 kJ of heat is added to the water and 5 kJ of heat is lost to the surrounding air. The paddle-wheel work amounts to 2 kJ. In the question that follows, select the answer that is closest to the true value. What is the change in internal energy of the water in units of kJ ?arrow_forwardThe inside wall of a furnace is at 2100oF and the outside wall is at 300oF. The wall of a furnace must be designed to transmit no more than 220 Btu/hr-ft2. Two types of bricks are available for construction:TYPE A: k = 0.38 Btu/ hr-ft-R with an allowable maximum temperature of 1400oFTYPE B: k = 0.98 Btu/ hr-ft-R with an allowable maximum temperature of 2300oF Both types of bricks have the same dimensions (9” x 4.5” x 3”) but the cost for Type B brick is twice the cost of Type A brick. Illustrate the order of arrangement of bricks A and B in the furnace wall (with thickness, estimated temperatures at the interface between walls A and B and at the interior and exterior surface, the transport area and direction of transfer included)arrow_forward
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