Copper-coated, epoxy-filled fiberglass circuit boards are treated by heating a stack of them under high pressure, as shown in the sketch. The purpose of the pressing—heating operation is to cure the epoxy that bonds the fiberglass sheets, imparting stiffness to the boards. The stack, referred to as a book, is comprised of 10 boards and 11 pressing plates, which prevent epoxy from flowing between the boards and impart a smooth finish to the cured boards. In order to perform simplified thermal analyses, it is reasonable to approximate the book as having an effective thermal conductivity (k) and an effective thermal capacitance
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Introduction to Heat Transfer
- Two inches of urethane foam will reduce heat loss close to 1000% when applied to a 2-inch diameter uninsulated steel pipe. Assume the pipe wall thickness is 0.25-inches, the pipe interior convective heat loss (hi) is 500 BTU/hr-ft2-oF, and the pipe outside convective heat loss ho 20 BTU/hr-ft2-oF, k steel is 25 BTU/hr-ft-oF, and k insulaton is 0.023 BTU/hr-ft-oF. (hint - calculate heat loss with and without insulation.arrow_forwardc) A steel pipe of 100 mm bore, and 10 mm bore thickness, carrying dry saturated steam at 28 bars, is insulated with a 40 mm layer of moulded insulation. This insulation in turn is insulated with a 60 mm layer of felt. The atmospheric temperature is 15 °C. Calculate: (i) the rate of heat loss by the steam per metre pipe length. (ii) the temperature of the outside Dimensions in mm surface.zzzzzzz h₂-15 W/m²K Steel k₁=50 W/mK AVALEHT Ø100 1₂ " Steam 28 bar h-550 W/m²K, Inner heat transfer coefficient = 550 W/m² K Outer heat transfer coefficient = 15 W/m² K Thermal conductivity of steel = 50 W/m K Thermal conductivity of felt = 0.07 W/m K Moulded insulation Felt Moulded insulation K₂=0.09 W/mK Thermal conductivity of moulded insulation = 0.09 W/m 40 10. A 60 15°C Felt K₁=0.07 W/mK zzzzzzzzarrow_forwardPROBLEM: IIC-21 BOOK: ENGINEERING THERMOFLUIDS, M. MASSOUDarrow_forward
- Review Conceptual Example 5 before attempting this problem. To illustrate the effect of ice on the aluminum cooling plate, consider the drawing shown here and the data contained therein. Ignore any limitations due to significant figures. (a) Calculate the heat per second per square meter that is conducted through the ice-aluminum combination. (b) Calculate the heat per second per square meter that would be conducted through the aluminum if the ice were not present. Notice how much larger the answer is in (b) as compared to (a). (a) Number i (b) Number i -10.0°C Units Units Ice -0.0050 m Aluminum -25.0°C 0.0015 marrow_forwardCalculate the sphericity of a cylinder of diameter 1 cm and height 3 cm.arrow_forwardDerive heat diffusion equation for cylinder and circlearrow_forward
- Volumetric expansion coefficients of simple materials are often well cataloged. However, the thermal expansion coefficient B of a human body is less well known. This could affect the human body's specific gravity and, therefore, measurements of its body-fat ratio. Suppose that a human body of weight wo on dry land is placed on a scale while completely immersed in formaldehyde of temperature T1- Once the temperature increases by AT, the scale reading drops by Aw. Derive an expression for ß in terms of AT, wo, and Aw by assuming that the ratio of the density of formaldehyde ef and the initial density of the body Po is R = Pf/pb. Assume also that pf does not change when heated. B = %3D If the body weighs 237.2 lb on dry land and his weight reading lowers by 0.237 lb when the formaldehyde is heated from 63.40 °F to 82.80 °F, calculate the coefficient of volume expansion of the body.* Assume R = 0.820. 1/°C B =arrow_forwardChapter Va - 31 BOOK: ENGINEERING THERMOFLUIDS, M. MASSOUDarrow_forwardThe Diamond Ring Solution. The processing chip on the computer that controls the navigation equipment on your spacecraft is overheating. Unless you fix the problem, the chip will be damaged and the navigation system will shut down. You open the panel and find that the small copper disk that was supposed to bridge the gap between the smooth top of the chip and the cooling plate is missing, leaving a 2.0 mm gap between them. In this configuration, the heat cannot escape the chip at the required rate. You notice by the thin smudge of thermal grease (a highly thermally conductive material used to promote good thermal contact between surfaces) that the missing copper disk was 2.0 mm thick and had a díameter of 1.2 cm. You know that the chip is designed to run below 65 °C, and the copper cooling plate is held at a constant 5.0 °C. (a) What was the rate of heat flow from the chip to the copper plate when the original copper disk was in place and the chip was at its maximum operating…arrow_forward
- Question : Studies show that the major energy consumption in Fijian villages is wood which is used for cooking over open fires. Typical consumption of wood is 1 kg person–1day–1. (a) Estimate the heat energy required to boil a 2-liter pot full of water. Assuming this to be the cooking requirement of each person, compare this with the heat content of the wood, and thus estimate the thermal efficiency of the open fire. (b) How much timber has to be felled each year to cook for a village of 200 people?Assuming systematic replanting, what area of crop must the village therefore set aside for fuel use if it is not to make a net deforestation? Hint: refer to Table 10.4. (c) Comment on the realism of the assumptions made, and revise your estimates accordingly. Answer: (a) mcDT ≈ 0.6 MJ (heat losses from pot imply actual requirement is higher). h ≈ 3%. (b) 70 tonnes; 7 ha.arrow_forwardThe Diamond Ring Solution. The processing chip on the computer that controls the navigation equipment on your spacecraft is overheating. Unless you fix the problem, the chip will be damaged and the navigation system will shut down. You open the panel and find that the small copper disk that was supposed to bridge the gap between the smooth top of the chip and the cooling plate is missing, leaving a 2.0 mm gap between them. In this configuration, the heat cannot escape the chip at the required rate. You notice by the thin smudge of thermal grease (a highly thermally conductive material used to promote good thermal contact between surfaces) that the missing copper disk was 2.0 mm thick and had a diameter of 1.0 cm. You know that the chip is designed to run below 70 °C, and the copper cooling plate is held at a constant 5.0 °C. (a) What was the rate of heat flow from the chip to the copper plate when the original copper disk was in place and the chip was at its maximum operating…arrow_forward@ Draw a neat sketch for a seive tray column for gas-liquid contact. Label the main parts of such column? And what are other types of trays?arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning