
Sometimes we can develop equations and solve practical problems by knowing nothing more than the dimensions of the key parameters in the problem. For example, consider the heal Joss through a window in a building. Window efficiency is rated in terms of "R value," which has units of (ft2 · h · °F)/Btu. A certain manufacturer advertises a double-pane window with an R value of 2,5. The same company produces a. triple-pane window with an R value of 3.4. In either case the window dimensions are 3 ft by 5 ft. On a given winter day, the temperature difference between the inside and outside of the building is 45°F. (a) Develop an equation for the amount of heat lost in a given time period
(b) How much heat (in Btu) is lost through the triple-pane window in one 24-h period?
(c) Suppose the building is heated with propane gas, which costs $3.25 per gallon. The propane burner is HO percent efficient. Propane has approximately 90,000 Btu of available energy per gallon. In that same 24-h period, how much money would a homeowner save per window by installing triple-pane rather than double-pane windows?
(d) Finally, suppose the homeowner buys 20 such triple-pane windows for the house. A typical winter has the equivalent of about 120 heating days at a temperature difference of 45°F. Each triple-pane window costs $85 more than the double-pane window. Ignoring interest and inflation, how many years will it take the homeowner to make up the additional cost of the triple-pane windows from heating bill savings?

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Chapter 1 Solutions
Fluid Mechanics
- 7) Please draw the front, top and side view for the following object. Please cross this line outarrow_forwardA 10-kg box is pulled along P,Na rough surface by a force P, as shown in thefigure. The pulling force linearly increaseswith time, while the particle is motionless att = 0s untilit reaches a maximum force of100 Nattimet = 4s. If the ground has staticand kinetic friction coefficients of u, = 0.6 andHU, = 0.4 respectively, determine the velocityof the A 1 0 - kg box is pulled along P , N a rough surface by a force P , as shown in the figure. The pulling force linearly increases with time, while the particle is motionless at t = 0 s untilit reaches a maximum force of 1 0 0 Nattimet = 4 s . If the ground has static and kinetic friction coefficients of u , = 0 . 6 and HU , = 0 . 4 respectively, determine the velocity of the particle att = 4 s .arrow_forwardCalculate the speed of the driven member with the following conditions: Diameter of the motor pulley: 4 in Diameter of the driven pulley: 12 in Speed of the motor pulley: 1800 rpmarrow_forward
- 4. In the figure, shaft A made of AISI 1010 hot-rolled steel, is welded to a fixed support and is subjected to loading by equal and opposite Forces F via shaft B. Stress concentration factors K₁ (1.7) and Kts (1.6) are induced by the 3mm fillet. Notch sensitivities are q₁=0.9 and qts=1. The length of shaft A from the fixed support to the connection at shaft B is 1m. The load F cycles from 0.5 to 2kN and a static load P is 100N. For shaft A, find the factor of safety (for infinite life) using the modified Goodman fatigue failure criterion. 3 mm fillet Shaft A 20 mm 25 mm Shaft B 25 mmarrow_forwardPlease sovle this for me and please don't use aiarrow_forwardPlease sovle this for me and please don't use aiarrow_forward
- 3. The cold-drawn AISI 1040 steel bar shown in the figure is subjected to a completely reversed axial load fluctuating between 28 kN in compression to 28 kN in tension. Estimate the fatigue factor of safety based on achieving infinite life (using Goodman line) and the yielding factor of safety. If infinite life is not predicted, estimate the number of cycles to failure. 25 mm + 6-mm D. 10 mmarrow_forwardCORRECT AND DETAILED SOLUTION WITH FBD ONLY. I WILL UPVOTE 1. The truss shown is supported by hinge at A and cable at E.Given: H = 4m, S = 1.5 m, α = 75⁰, θ = 33⁰.Allowable tensile stress in cable = 64 MPa.Allowable compressive stress in all members = 120 MPaAllowable tensile stress in all members = 180 MPa1.Calculate the maximum permissible P, in kN, if the diameter of the cable is 20 mm.2.If P = 40 kN, calculate the required area (mm2) of member BC.3. If members have solid square section, with dimension 15 mm, calculate the maximum permissible P (kN) based on the allowable strength of member HI.ANSWERS: (1) 45.6 kN; (2) 83.71 mm2; (3) 171.76 kNarrow_forwardCORRECT AND DETAILED SOLUTION WITH FBD ONLY. I WILL UPVOTE 2: A wire 4 meters long is stretched horizontally between points 4 meters apart. The wire is 25 mm2 in cross-section with a modulus of elasticity of 200 GPa. A load W placed at the center of the wire produces a sag Δ.1.Calculate the tension (N) in the wire if sag Δ = 30 mm.2.Calculate the magnitude of W, in N, if sag Δ = 54.3 mm.3. If W is 60 N, what is the sag (in mm)?ANSWERS: (1) 562 N, (2) 100 N, (3) 45.8 Narrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning
