A computer consists of an array of five printed circuit boards (PCBs), each dissipating
(a) If the temperature rise of the airflow.
(h) The component that is most susceptible to thermalfailure dissipates
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Fundamentals of Heat and Mass Transfer
- Q5Two large containers A and B of the same size are filled with different fluids. The fluids in containers A and B are maintainedat 0° C and 100° C, respectively. A small metal bar, whose initial temperature is 100° C, is lowered into container A. After1 minute the temperature of the bar is 90° C. After 2 minutes the bar is removed and instantly transferred to the othercontainer. After 1 minute in container B, the temperature of the bar rises 10°. How long, measured from the start of theentire process, will it take the bar to reach 99.9° C?arrow_forwardQi) Consider a large plane wall of thickness L = 0.4 m, thermal conductivity k= 2.3 W/m · °C, and surface area A= 20 m. The left side of the wall at x= 0 is subjected of T1 80°C. while the right side losses heated by convection to the surrounding air at T=15 °C with a heat transfer coefficient of H=24 W/m °C. Assuming constant thermal conductivity and no heat generation in the wall, (a) express the differential equation and the boundary conditions for steady one- MSc. Rasha Nasser 30arrow_forwardAs shown in the figure, an exterior wall of a building has an average thermal conductivity of 0.32 Btu/h-ft-ºR and a thickness of L = 8 in. At steady state, the temperature of the wall decreases linearly from T₁ = 70°F on the inner surface to T₂ on the outer surface. The outside ambient air temperature is To = 20°F and the convective heat transfer coefficient is 5.1 Btu/h-ft2.°R. Step 1 Determine the temperature T2 in °F. T₂ = i °F. Wall x=0.32 Btu/h ft. R T₁- Determine the temperature T₂ in °F, and the rate of heat transfer through the wall, in Btu/h per ft² of surface area. h 5.1 Btu/h ft². °R -T₂arrow_forward
- As shown in the figure, an exterior wall of a building has an average thermal conductivity of 0.32 Btu/h-ft-ºR and a thickness of L = 4 in. At steady state, the temperature of the wall decreases linearly from T₁ = 70°F on the inner surface to T₂ on the outer surface. The outside ambient air temperature is To = 35°F and the convective heat transfer coefficient is 5.1 Btu/h-ft²-°R. Wall Step 1 Determine the temperature T₂ in °F. T₂ = i Determine the temperature T₂ in °F, and the rate of heat transfer through the wall, in Btu/h per ft² of surface area. Save for Later K=0.32 Btu/h ft. R °F. T₁- h 5.1 Btu/h ft² °R -T₂ Attempts: 0 of 4 used Submit Answerarrow_forwardAs shown in the figure, an exterior wall of a building has an average thermal conductivity of 0.32 Btu/h-ft-ºR and a thickness of L = 6 in. At steady state, the temperature of the wall decreases linearly from T₁ = 70°F on the inner surface to T₂ on the outer surface. The outside ambient air temperature is To = 20°F and the convective heat transfer coefficient is 5.1 Btu/h.ft2.°R. Wall K=0.32 Btu/h ft. R T1- h=5.1 Btu/h ft². °R -T₂ Determine the temperature T₂ in °F, and the rate of heat transfer through the wall, in Btu/h per ft² of surface area.arrow_forwardIP Heat Transport in the Human Body The core temperature of the human body is 37.0 ∘C∘C, and the skin, with a surface area of 1.40 m2m2, has a temperature of 34.0 ∘C∘C. Find the rate of heat transfer out of the body under the following assumptions: (i) The average thickness of tissue between the core and the skin is 1.20 cmcm; (ii) the thermal conductivity of the tissue is that of water. Express your answer using two significant figures. Without repeating the calculation of part A, what rate of heat transfer would you expect if the skin temperature were to fall to 31.0 ∘C∘C? Express your answer using two significant figures.arrow_forward
- A 3,500-seat auditorium is to be air-conditioned using window units 10 kW nominal value. Assume that a person at rest will dissipate heat at a rate of approximately 360 kJ/h. There are 200 lamps in the auditorium, each rated at 250 W. The rate of heat transfer to the auditorium through the walls and windows is estimated to be equal to 150,000 kJ/h. If the auditorium air goes to maintain at a constant temperature of 200°C, determine the number of air conditioning units of required window. Answer: 45 units.arrow_forwardSteam at 150 ° C flows in a pipe having an inner radius of 45 mm and an outer radius of 55 mm. The convective heat transfer coefficient between the steam and the inner pipe wall is 2500 W / (m² ° C). The outer surface of the pipe exposed to ambient air is 20 ° C with a convective heat transfer coefficient of 10 W / (m² ° C). Assuming steady state, calculate the rate of heat transfer per meter of pipe from steam to air. Assume that the thermal conductivity of stainless steel is 15 W / (m ° C.). Steps of work according to example 4.16 Singh. a. Find the overall heat transfer coefficient = Answer W / m² ° C. b. Heat transfer rate per meter of pipe = Answer W / m.arrow_forwardConsider a heat conductor in the form of a long cylinder, with inner and outer radii R1 and R2, respectively. Heat is generated within the cylinder, where the temperature O(r, t) at position r and time t satisfies the modified heat equation = DV0 + H, where D is the thermal diffusivity, and H is proportional to the rate of heat production. The inner and outer surfaces of the cylinder are cooled by a fluid maintained at constant temperature Oo. (a) If the temperature is in a steady state and depends only on the distance r from the centre of the cylinder, use cylindrical coordinates (r, 0, 2) to write down an ordinary differential equation for O(r) valid in the region R1arrow_forwardSteam at 150 ° C flows in a pipe having an inner radius of 50 mm and an outer radius of 55 mm. The convective heat transfer coefficient between the steam and the inner pipe wall is 2500 W / (m² ° C). The outer surface of the pipe exposed to ambient air is 25 ° C with a convective heat transfer coefficient of 10 W / (m² ° C). Assuming steady state, calculate the rate of heat transfer per meter of pipe from steam to air. Assume that the thermal conductivity of stainless steel is 15 W / (m ° C.). Steps of work according to example 4.16 Singh. a. Find the overall heat transfer coefficient = Answer W / m² ° C. b. Heat transfer rate per meter of pipe = Answerarrow_forwardA food product containing 85% moisture content is being frozen. Estimate the specific heat of the product at -4 ° C when 62% of the water is frozen. The specific heat of the dry product is 2.5 kJ / (kg ° C). It is assumed that the specific heat of water at -10 ° C is the same as the specific heat of water at 0 ° C, and that the specific heat of ice follows the function Cp es = 0.0062 Tbeku + 2.0649. Cp of frozen product = Answer kJ / kg ° C.arrow_forwardIt is a Thermodynamics subject. Explain each Common Causes of Irreversibility 1. Electric resistance 2. Inelastic deformation 3. Viscous flow of a fluid 4. Solid-solid friction 5. Heat transfer across a finite temperature difference 6. Fluid flow through valves and porous plugs (throttling) 7. Mixing of dissimilar gases or liquids 8. Mixing of identical fluids initially at different pressures and temperaturesarrow_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