Question

Consider a composite wall that includes an 8-mm thick hardwood siding, 40mm by 130mm hardwood studs on .65m centers with glass insulation ( paper faced, 28 kg/m^3) and a 12mm layer of gypsum (vermiculite) wall board.

what is the thermal resistance associated with a wall that is 2.5m high by 6.5m wide ( having 10 studs, each 2.5m high)? assume surfaces parallel to the x-direstion are adiabatic.
Introduction to heat transfer sixth edition prob. 3.16

Answer 1

To find the thermal resistance associated with the composite wall, calculate the R-values of each layer and sum them up.

Step-by-step explanation:

To find the thermal resistance associated with the composite wall, we need to calculate the thermal resistance of each layer and then sum them up.

First, let's calculate the thermal resistance of the hardwood siding:

Thermal resistance of hardwood siding = thickness / thermal conductivity = 8 mm / ksiding

Next, let's calculate the thermal resistance of the hardwood studs:

Thermal resistance of hardwood studs = thickness / (thermal conductivity x cross-sectional area) = 40 mm / (kstud x 40 mm x 130 mm)

Now, let's calculate the thermal resistance of the glass insulation:

Thermal resistance of glass insulation = thickness / (thermal conductivity x cross-sectional area) = 40 mm / (kinsulation x 40 mm x 130 mm)

Finally, let's calculate the thermal resistance of the gypsum wall board:

Thermal resistance of gypsum wall board = thickness / thermal conductivity = 12 mm / kgypsum

Now, we can sum up the thermal resistances of all layers:

Total thermal resistance = thermal resistance of hardwood siding + (number of studs x thermal resistance of hardwood studs) + thermal resistance of glass insulation + thermal resistance of gypsum wall board