Question

i figured out the first question but im not sure how to answer question 2 and 3?

i have figured out question 2. Question #3 is what is diffcult to grasp because i have to guess my Fo #. Fo=time

1. To reduce building heating costs, modern building codes in many parts of the country require the use of double-pane windows (sometimes, called "double-glazed" or "thermopane" windows). Some of In one design of a double-pane window, each glass layer is 0.7 cm thick, the stagnant air layer is 2 sm thick, and the area is 4 m2 In the living room of a large suburban house, 10 of these windows are installed. In the six months of winter, the room is heated by a bank of electric resistance heaters, which maintains the moving air temperature inside the living room at 22 c when the Calculate the savings that are obtained when double-pane windows are used, instead of single-pane windows. GIVE YOUR ANSWER IN DOLLARS A single-pane window contains one laver of glass,0.7 cm thick Thermal conductivity of the glass 0.81 (W(m.K) Thermal conductivity of stagnant airs 0.024 w/(m-K). Mean convective heat a glass laver 4 W/(m2.K) Mean convective heat transfer coefficient between the moving air outside a room and a glass laver 15 W(m2K). Take each month to comprise 30.4 days and assume that the heating bank runs continuously every day. In the suburb, electricity costs $0.10/kWh. transfer coefficient between the moving air inside a room and

Answer 1

SOLUTION Khoun : Inatic l tempe trutuste, hoof ternpeacduce and din c. İcra c cylindro and tempesneture and cenvecfon cendifions otsng Findi: Time to neach etepaed cententhe tempestakore Shemec 1 Asumptong 1. Two-dimengenal conduction m γ and χ R. Constant Prepeahes s. Shont Cylinden , k=0-634w(mps) Anabypp: The tempenahse at any pefnt and Hmein e cylindaical steak may be expaesed a the folleuing preduch Where 'To- 14s℃ wheste P,t)and C,t) ar definedl as Wall d=o. 14245 m= 142-4S mm andpo L:4=0.071m=71.22m

Hence ton the plane wal wfh 0634 Wm- Unit becau L- .071 m e: rad) paepunty totle t plane wall. with F. given ahove e.-TL,t)기부 1-1594 8g expl-(1) w alt 0 634 gr. hr, = 15.63424 0.5934 ende Hence, fan the centen d the cyinder, T(o, x,)-To 80-175 sall 二0.562 By soluing, oe get 168.36 min (afpnox) Anheue.