Given a composite wall with dimensions as shown in the figure below. The wall st
ID: 1718042 • Letter: G
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 Do you expect there to be a difference in resistance between case a and b? BONUS Solve the total resistance if the wall has 10 studs that are each 2.2m high from part a.Explanation / Answer
let L1 = length of brick , L2 = length of insulation , L3 = length of paster board
K1 = thermal conductivity of brick , K2 = thermal conductivity of insulation , K3 = Thermal conductivity of plaster board
A1 = Area of cross section of brick ,A2 area of cross section of Insulation ,A3 = Area of cross section of Plaster board
T 1 = Temperature of inet at Brick , T2 = Temperature of outlet at plaster board
Total heat transfer Q = T1 - T2 / L1 / K1 A1 + L2 /K2 A2 + L3 /K3 A3
Q = T1 - T2 / R
Where R = Thermal Resistance = L1 / K1 A1 + L2 /K2 A2 + L3 / A3 K3
If a system is well insulated, no transfer of heat will occur between it and its environment. This means that Q = 0, and the first law of thermodynamics shows that ÆU = - W
If work is done by the system (positive W) its internal energy decreases. Conversely, if work is done on the system (negative W) its internal energy will increase. For gases, the internal energy is related to the temperature: a higher internal energy means a higher temperature. Adiabatic expansion of a gas will lower its temperature; adiabatic compression of a gas will increase its temperature
Yes there is some difference between the resisistance of adiaabatic process
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