please very urgent i need the right answer please be carfully A power transistor of 10 mm of diameter (D),and 15 mm of length (L), is cooled by an airstream with Tair =20 C, and h = 120 W/m^2.K.What is the maximum allowable powerdissipation, Pmax if the surface temperatureshould not exceed 80 C.a.0.229 Wb. 6.3 WC.1.5 Wd. 3.9 WClear my choice

Answered: A power transistor of 10 mm of diameter…

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.68P

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A coolant with a temperature of -20 ° C passes through a copper cylindrical wire. The outer diameter of the wire is 10 mm. The wire is in contact with air at a temperature of 25 ° C, which is h = 50 W / m2K. The heat conduction coefficient of the wire is k = 0.5 W / mK. Different thicknesses of insulation will be applied to the wire. a) Calculate separately the heat transfer rate per m when 0, 2.5, 5 and 7.5 m insulation is applied. b) Interpret from which thickness the insulation will increase the heat transfer by calculating the critical radius. c) Graph the insulation thickness and heat transfer rate against each other.
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The thermal conductivities of wood is kwood = 0.1W/(m°C)and air is kair = 0.0234W/(m°C). Part A If the temperature of the room is 20°C and outside is 10°C, find the rate of heat flow for a wall of wood with area = 10 m² and thickness of 5cm. O 60 W O 304 W O 34 W O 200 W O 100 W Submit Request Answer Part B The wall of wood with thickness of 5cm is now replaced with two layers of wood and a gap of air between the wood. Each layer of wood has a 2.5cm thickness and the gap is 1cm. The rate of heat flow will, decreases. increases. stay the same. Submit Request Answer Part C The temperature in the air gap will be, O 20°C, between 10°C and 20°C, O 10°C,
ha T. R h Ta = 40 W/m °C %3D pipe L=1 m; R, = 0.05m; R2 = 0.052m; Tin = 70°C; Tout = 20°C; hn = 30 W/m2 °C; hout = 20 W/m2 °C; K The total thermal resistance of insulated steam pipe, if a 0.03m thickness of fiberglass insulation (K fibergias = 0.04 W/m. °C) is added to pipe to save heat losses. 3°C/W Ob - 2°CW -1°C/W Od. No answer is correct
Q.3//A// Find the sensible heat ratio, if the latent heat in a room is 25% of the sensible heat load. Q.3//B//Consider 5mm thick wall with a thermal conductivity of 1.5 W/m.K. The temperature of the air inside is 40°C and heat convection coefficient is hi =30 W/m².K. The outside condition space is exposed to a flow air at -10°C with a convection heat transfer coefficient ho=60 W/m².K. Find the inside and outside wall surface temperature? "20min"
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SOLVE STEP BY STEP DONT USE CHATGPT There is a horizontal PVC pipe (k=0.16 W/m°C) with a diameter of 15 cm, a wall of 3 mm and a length of 8 m. The external surface of PVC is at 19 °C. Inside this pipe is placed a steel pipe (k=45 W/m.°C), 7 em in external diameter and 2 mm thick, also 8 m long, where saturated steam circulates at 0.38 m. /s and 1.3 atm pressure. The temperature of the steel is at the same temperature of the steam. The annular space between the two pipes is filled with static air. Determine the heat flow that occurs from the steam to the outside of the system.
The ratio of heat flow Q1/Q2 from two walls of same thickness be selected) having their thermal resistances as Rth1=2 Rth2 will be: 40% of an incident radiant energy on the surface of a thermally transparent body is reflected back. If the transmissivity of the body QI Select the correct answer: 1. A. 0.125 B. 0.5 С. 0.25 D. 2 2. The absorptivity of a blackbody is equal to: В. 0.5 A. 1 C. D. None of them zero 3. be 0.15, then the emissivity of surface is: В. О.55 A. 0.45 С. D. None of them 0.40 4. Unsteady state heat flow means, A. Negligible flow of heat B. No difference of temperature between the bodies C. Heat flow independent of D. None of them time 5. The boundary conditions of the infinite length fin are: dT - kA А. В. and T-To - kA( = 0 and T=T00 at x=0 at x=L D. None of them T=0 at x-0 and q=0 at x-L Two concentric cylinders are radiated heat to each other, the inner cylinder (1) is (10cm) diameter, the outer cylinder (2) is (30cm) diameter, the shape factor F21 is equal to: А.…
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A) A plane wall has internal heat generation and is cooled covectively at its two faces. Given : heat generation rate g=1,000W/m? | 50 wall thickness 2L= 100 mm air temp T = 20C temp within wall T(x) = 10(0.052 – x')+30 WIm.K Find thermal conductivity of the wall h% D k = A1) Wim? K A2) Find convection heat transfer coeff Solution

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