Given a composite wall with dimensions as shown in the figure below. The wall st

Question

Given a composite wall with dimensions as shown in the figure below. The wall studs are made of hardwood and the insulation is glass fiber, paper faced (28 kg/m^3). The common brick is 1 cm and the plaster board is 1.1 cm thick. Draw the thermal resistance network and write out how you would solve R_total but do not actually do the math. Assume the surfaces parallel to the x-direction are now adiabatic. Draw the thermal resistance (2) Do you expect there to be a difference in resistance between case a and b? BONUS Solve the total resistance if the w all has 10 studs that are each 2.2m high from part a.

Explanation / Answer

Net Heat transfer = Q = K xA dT / dx

= dT / L /KA

Where L/KA = R Thermal resistance

Here the common brick and insulation and plaster board are in series and heat flowing from top to bottom

let K1 be thermal conductivity of common brick ,L1 be the length of common brick ,A1 be the area of cross section of common brick

Let K2 be the thermal conductivity of insulation ,L2 be the length of insulation , A2 be the area of crosssection of insulation and K3 be the thermal conductivity of plaster board L3 length of plaster board, A3 be the area cross section of the plaster board

Net Heat transfer Q = T1 - T2 / R1 + R2 + R3

R = R1 + R2 +R3

R1 = L1 /K1 A1 = 15 / K1 x 15 x 0.01

R2 = L2 /K2 x15 x 0.12

R3 = L3 /K3 x 15 x 0.11

Net thermal resistance = R = R1 + R2 + R3 + R4

15 / K1 x 0.01x 15 + 15 /K2 x 0.12 x15 + 15 /k3 x 0.11x15

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